Genus Brucella

very small gram negative coccobacilli

aerobic

obligate parasites of mammals

target reproductive organs

Genus Brucella

Stains red with Ziehl-Neelsen stain (partially acid fast)

Growth on blood agar or chocolate under increased Co2

B. abortus

(7 biovars)

Main Host: Cattle

Abortion, orchitis, epididymitis

Sheep, goats, pigs -- sporadic abortion

Horses -- butsitis

Humans -- intermittent systemic disease

B. melitensis

(3 biovars)

main hosts: Goats and Sheep

abortion, orchitis, epididymitis

Cattle -- sporadic abortion

Humans -- severe systemic disease

B. suis

(5 biovars)

Main host: Pigs

abortion, orchitis, epididymitis

Humans -- intermittent systemic disease

B. ovis

Sheep

Epididymitis

B. canis

Main host: dogs

abortion, epididymitis, discospondylitis

Humans -- mild systemic disease

B. abortus

B. melitensis

B. suis

have smooth colonies on isolation, due to long LPS O-antigens, and react with antibodies to antigen A and/or antigen M

B. ovis

B. canis

have rough colonies, with short LPS O antigens, and react with antibody to R (rough) antigen, but not A or M

Colonial Morphology

and

PCR

Two ways to distinguish Brucella genera

Brucellosis

Horses are resistant, but can have inflammation of the supra-atlantal (poll evil) and supraspinous (fistulous withers) bursae due to infection.  The bursa is swollen and painful initially and may rupture to discharge through a sinus

Genus Brucella

Found worldwide unless eradication programs in place

Reservoir: Reproductive organs of animals

Major cause of abortion

Brucella

Transmission:

ingestion of organsisms from aborted fetuses and vaginal discharge, or milk

via mating for some species

penetration of skin via cuts and abrasions

inhalation, transplacental

sexually mature animals are more susceptible and pregnant animals are most suscetible

Brucella

no exotoxins known

smooth LPS -- smooth strains and species are more virulent than rough, and more resistant to phagocytic killing and complement mediated killing

Required for uptake into macrophages via lipid rafts

cyclic beta-glucans in outer membrane

Type IV secretion system (Vir system)

survival and multiplication in macrophages in vacuole, which is formed via fusion with rough ER

Brucella Abortus

cattle

bacteria ingested and penetrate intestinal mucosa through Peyer's patches

engulfed by macrophages

Brucella abortus

Cattle

bacteria survive within macrophages by blocking phagosome maturation and forming the Brucella-containing vaculoe

acidification of vacuole, but no fusion with lysosomes

resistance to oxidative killing via catalase, superoxide dismutaste, etc

fusion with ER membranes

Brucella abortus

cattle

spread to regional lymph nods

dissemination hematogenously to reticuloendothelial system and repro tract

erythritol growth factor (sugar alcohol in placenta/mammary/epididymis)

Brucella abortus

Cattle

replication in trophoblast cells of placenta increases in late gestation due to hormones produced -- infection spreads to fetus

placentitis leads to fetal death and abortion

large numbers of bacteria are shed in aborted fetuses, placentas, and vaginal discharge

presistent lifelong infection with intermittent shedding in productive and mammary secretions

Brucella abortus

Cattle

abortions in unvaccinated first-calf heifers is the most common presentation, with no overrt systemic illness

late gestation

females usually abort only nce, presumably due to aquired immunity

continue to shed organisms in milk an vaginal secretions

In males, epididymitis and orchitis, with decreased fertility and eventually sterility

Brucella melitensis

goats and sheep

transmission via ingestion

abortion storms in last 2 months of pregnancy

mastitis common in goats

causes the most severe infections in humans

Brucella ovis

sheep

reduced virulence due to "rough" rather than "smooth" LPS

organism carried by rams -- epididymitis and infertility in ram, disease prevalence increases with age

low pathogenicity for ewes - rare abortion in ewes

Brucella suis

pigs

transmission via ingestion and venereally

orchitis with swelling and necrosis of one or both testicles leads to sterility

Brucella canis

Dogs- permanently rough so of comparatively low virulence

mainly seen in breeding kennels

causes abortion in last trimester of pregnancy with no prior signs, stillbirth, infertility, vaginal discharge after abortion for several weeks

- fetuses usually autolyzed, suggesting death in utero prior to abortion

In males, inflammation of the testes and epididymis, infertility

Can also see spondylitis and uveitis

Brucella

Pathology

Placentitis: multifocal pale foci are scattered in the cotyledons  and the intercotyledonary spaces also show thickening, with a yellowish gelatinous exudate and necrosis of their surface.

marked edema of placenta

epididymitis and orchitis are commonly seen in males

Brucella

Diagnosis

Examination of placenta is critical

- thickened, yellow gelatinous exudate

- brown,  necrotic, edematous

- gram neg coccobacilli, MZN positive

Serology to detect antibody in blood, milk, semen

- milk ring test

- agglutination tests (rose bengal test)

- CF

- AGID, ELISA, etc.

- more serologic tests than any other organism

B. melitensis

On a large sheep farm, there was an abortion storm, with 40% of the ewes aborting in late gestation. Aborted lambs showed edema and congestion of the lungs, spleen and other internal organs.  Placental membranes were edmeatous and had yellow fibrious exuate, and cotyledons were hemorrhagic and necrotic.

Brucella

use combination antibiotics treat for 6-8 weeks

in humans and dogs

Tetracycline + Rifampin or similar

Brucella

eradication programs rely upon:

- eradication of positive animals

- serology for monitoring

- vaccination

same as other agents of abortion: isolate all aborted animals for several weeks, burn all placentas, clean areas where abortions occured

organism can survive for several monts in environment

Brucella

Prevention

live attenuated vaccines- RBS1 or strain 19 in cattle

- RBS1 is safer, does not elicit antibodies that cause false positive reactions on serologic tests

- all calves should be vaccinated; adult females can be vaccinated if needed; bulls should not be vaccinated (development of orchitis)

Rev1 strain in goats - partially attenuated

bacterin for sheep not very effective

no vaccine for dogs, pigs, or humans

Brucellosis

most commonly reported laboratory-aquired infection, and vet exposure throud disease and vaccine

Human transmission--> ingestion of contaminated milk or products, inhalation of infectious aerosols, contamination of skin wound, rarely person-to-person via sexual contact or breast-feeding

Human symptoms --> fever, chills, malaise, headache, low back pain, joint pain, drenching sweats, 103-104F, undulant fever

--> chronic: anorexia, weight loss, abdominal pain, joint pain, headace, weakness, irritbility, insominia, depression, constipation

Physical findings: mainly splenomegaly, lymphadenopathy

Bacillus anthracis

Bacillus anthrcis

REPORTABLE

large gram positive spore-forming rods

aerobic

grows on blood agar with "ground glass" morphology

colonies have "medusa head" appearance

Bacillus anthracis

spores in soil

endemic in S./N. Dakota, Nebraska, Arkansas, Texas, Louisiana, Mississippi, California

transmission through ingestion, inhalation, or breaks in skin

no direct animal-to-animal transmission

Bacillus anthracis

primarily a disease of herbivores- carnivores are infected by ingestion of contaminated meat

outbreaks associated with climate change, such as after a rainstorm ending a period of drough or dry summer after heavy rain

usually warmer months

endemic in tropical and sub-tropical areas with high rainfall

Bacillus anthracis

Capsule and toxins- encoded on separate plasmids, required for disease production

Capsule - poly-D-glutamic acid

- loss of capsule leads to reduced virulenc

- encoded on plasmid pXO2

- non-toxic, but protects bacteria against phagocytosis and complement-mediated killin

Exotoxin- complex of protective Ag, lethal factor, and edema factor

- loss of toxin leads to loss of virulence

- encoded on plasmid pXO1

Bacillus anthracis

exotoxins

edema factor- adenylate cyclase which causes increased intracellular levels of cAMP once it enters host cells which leads to fluid accumulation in tissues

lethal factor- endoprotease that kills macrophages

protective Ag- binds three factors and facilitates entry of EF and LF into host cells

Bacillus anthracis

Pathogenesis

- ingestion or inhalation of spores from environment

- sproes rapidly phagocytized by macrophages

- spores germinate in macrophages - rapidly produce toxin and capsule

- bacteria multiply within macrophages - carried to regional lymph nodes

- Bacteria kill macrophages and escape - multiply in lymph nodes and spread systemically

- septicemia leads to massive invasion of tissues

- toxemia leads to extensive edema and necrosis and eventually shock, hypotension, anoxia, organ failure

Bacillus anthracis

In cattle and sheep, most animals found dead with no premonitory signs

- high fever, depression, congested mucosae, subcutaneous edema, respiratory distress, anorexia

In pigs, edematous swelling of the throat and head and regional lymphadenitis

 In horses, slower progression because disease is usually due to introduction of spores into skin abrasions

- extensive subcutaneous edema of thorax, legs, prgressing to similar disease as cattle

Bacillus anthracis

Necropsy:

rapid bloating

absence of rigor mortis

dark unclotted bloody discharges from nose, mouth, anus, vulva, etc.

dark bloodstained fluids in body cavities

Splenomegaly - extremely large soft spleen

Bacillus anthracis

Diagnosis:

clinical signs and necropsy

stain of tissue or blood with polychrome methylene blue

culture on blood agar, NG on MacConkey, gram stain, confirmation by biochemical tests and PCR

Bacillus anthracis

Treatment:

High doses of penicillin G or oxytetracycline if administered early

ciprofloxacin for humnas

hyperimmune serum if available

Bacillus anthracis

Prevention:

in endemic areas, annual vaccination with sterne strain (avirulent due to loss of pXO2 plasmid and capsule) spore vaccine

In sporadic epidemics, biosafety is critical!

anthrax vaccine for humans, preparation of protective antigen recovered from the culture filtrate of an avirulent, non-encapsulated strain that produces PA during active grwoth

Bacillus anthracis

major zoonotic pathogen and potential biological warfare agent!

natural disease in humans is often cutaneous, with localized papules that progress to ulcers then necrotic eschars, with extensive edema (can be systemic)

can progress to septicemia and systemic disease

inhalation anthrax also occurs

Yersinia pestis

Yersinia pestis

gram negative rods, ferment glucose and other sugars but not lactose, oxidasse negative

facultatice anaerobes, catalase positive

facultative intracellular pathogen

"the black death"

Yersinia pestis

circulates in rodent reservoirs

Sylvatic cycle- wild rodents transmitted by fleas

Urban cycle- rat populations with transmission by fleas

humans-flea bites, direct contact with infected animals or tissues, human aerosols

Yersinia pestis

Reservoir

rodents- rats and fleas in urban areas, prairie dogs, ground squirrels, fleas, in rural areas

Yersinia pestis

Transmission

In rodents via fleas, cats through ingestion of infected rodents, rodent bites, or flea bites

In humans- usually through flea bites, systemic spread from localized infection or via inhalation of aerosols from animals or people

Yersinia pestis

Many virulence factors are regulated by temperature, with some required for maintenance in the flea produced at flea temperature (20C) and others  for virulence in mammals produced at 37C

Yersinia pestis

Yersinia pestis

bubonic plague - characterized by enlarged lymph nodes associated with lymphatic drainage from site of infection. fever, depression, anorexia, affected superficial lymph nodes may rupture, discharge pus

septicemic - fever, hypotension, shock, hepatosplenomegaly

pneumonic plague - fever, dyspnea, hypotension, shock, hemoptysis

Yersinia pestis

Diagnosis:

culture from pus, blood, or lymph node aspirates

giemsa stain smears may show small rods with bipolar staining

direct fluorescent antibody staining

Yersinia pestis

Treatment: may respond to tetracycline of chloramphenicol

Control: routine treatment fro fleas, rodent control

Prevention: no vaccine

Yersinia pestis

Zoonosis:

humans infected through flea bites, animal bites, cat scratches, and aerosols

once a human has pneumonic plague, highly infectious to others

1-40 cases per year in US, 15% mortality

Francisella tularensis

gram negative coccobacillary rods, obligate aerobes

fastidious, cysteine required for growth

NG on MacConkey

facultative intracellular pathogen

Francisella tularensis

rabbits, deer, rodents, beaver, muskrats, ticks

ticks and deerflies- inhalation of infectious aerosols, ingestion

reported in sheep, horses, young pigs- clinical disease in livestock is rare

occurs in cats and humans

transmission correlates with heavy tick infestations

Francisella tularensis

Escherichia coli

gram negative rod, oxidase negative, ferments glucose and lactose- bright pink colonies on Mac

LPS - in outer membrane and endotoxin

moltile withe peritrichous flagella

generally colonize GI shortly after birth and persist as normal flora

more virulent strains not usually normal flora

Francisella tularensis

In sheep and mammals- characterized by sudden onset of high fever, lethargy, anorexia, stiffness, reduced mobility, increased pulse and respiratory rates = classic signs of septicemia

lymphadenitis, local or generalized

Humans- insect bite handling infected animals, skin ulcer, swollen lymph node, fever and septicemia

Francisella tularensis

Diagnosis:

clinical signs are non-specific

heavy tick infestation in severely ill animals within endemic areas

culture or detection by PCSR or fluorescent antibody stain of organism

must differentiate from other causes of septicemia- plague

Francisella tularensis

treatment: effective antibiotics include streptomycin, amikacin, and fluoroquinolones

Control: tick control, in endemic regions prevention from hunting wildlife

Prevention: no vaccines, vaccine for humans under review

Francisella tularensis

causes a serious and potentially fatal infections in humans

hunters, trappers, veterinarians,  and lab workers under particular risk

Burkholderia mallei

Burkholderia mallei

short gram negative rods, aerobic, obligate parasites

facultative intracellular pathogens

highly resistant to many antibiotics

causative agent of glanders, a disease that affects primarily horses, mules, and donkeys --> REPORTABLE

Burkholderia mallei

Reservoir: sub-clinically affected chronic carrier horses, donkey, mules

eradicated from US in mid 1900s

endemic in much of Eastern Europe, Asia, and N Africa, including former USSR, Iraq, Turkey, India, Pakistan, China, and United Arab Emirates

Burkholderia mallei

Transmission:

ingestion of food or water contaminated with respiratory exudates or skin exudates from clinically affected or carrier animals

Carnivores- ingestion of contaminated meat

infection through skin cuts and abrasions

inhalation

Glanders

three cardinal signs of clinical glanders in equines that can occur individually or in combination:

chronic nasal discharge that occurs with or without ulceration of the nasal septum - can progress to pulmonary, with nodules and abscesses in the lungs

enlargement and induration along the lymphatics and lymph nodes, especially the submandibular lymph nodes

nodules , pustules or ulcers on the flanks and extremeties of infected animals - swollen lymph vessels are present on the flanks of infected animals in a manifestation referred to as cording

Acute Glanders

nasal and pulmonary signs, including high fever, decreased appetite, coughing progressive dyspnea, nasal discharge, and ulcers and nodules on the nasal mucosa --> death within a few days to weeks

Chronic Glanders

develops insidiously and results in progressive debilitation

couging, malaise, dyspnea, intermittent fever, enlargement of lymph nodes, chonic nasal discharge, and ulcers, nodules and stellate scars on th enasal mucosa

skin and lymphatics may also be involved

slowly progressive and often fatal- affected animals may live for years before seccumbing to the disease

Burkholderia mallei

in endemic areas, clinical signs may be diagnositic

culture from lesions (not done in most labs)

serology - complement fixation and ELISA tests

mallein test = skin test similar to Tb tests

inject mallein just below lower eyelid; positive test is indicated by local swelling and mucopurulent ocular discharge within 24-48 hrs

Burkholderia mallie

Treatment- euthanasia of affected equids in most countries

Control- in an outbreak, quarantine of all animals and affected premises, in endemic areas, keep animals away from communal feeding and watering areas

Prevention- testing of animals prior to shipping across national and international lines; no vaccine

Burkholderia mallei

glander is rare but serious zoonotic diease

human infections can be traced to direct contact with infected animals or to laboratory exposure

mortality in acutely infected humans reaches 95% in three weeks if untreated

Burkholderia pseudomallei

gram negative coccobacillary rods bipolar staining

causative agent of mellioidosis in many animals an humans

grows on blood agar, growth on ashdown's agar

Burkholderia pseudomallei

Reservoir: widespread in soil and water in tropical areas (no found in US, europe)

Transmission: ingestion, inhalation, or skin contamination from environmental sources, occurs in wide range of animals- horses, sheep, goats, dogs, cats, primates, etc.

- infection usually disseminated, with abscesses developing in many organs- lungs, spleen, liver, etc

- chronic, devilitating, progressive disease with long incubation period

Burkholderia pseudomallei

Treatment:

euthanasia of infected animals in most countries

antibiotic treatment is expensive and unreliable, relapses frequent

Prevention- no vaccines available

Coxiella burnetii

small pleiomorphic gram negative rod

obligate intracellular pathogen

no growth in lab media, require tissue culture

causative agent of Q fever

affects sheep, goats, cattle, humans, also cats and dogs

Coxiella burnetii

Reservoir: obligate intracellular pathogen so the reservoir is carrier animals, a tropism for reproductive tissues

Transmission: aerosols of bacterin in vaginal discharges, can persist in dust, aerosols for long periods, direct contact with pregnant shedders

Coxiella burnetii

Pathogenesis:

bacteria replicate in monocytes and macrophages primarily

do not block fusion of phagosome and lysosome

require acidic conditions of mature phagolysosome

bacteria replicated exclusively within the phagosome

slow replication (20hr generation time) may explain why organism does not cause more damage

spread hematogenously in macrophages to reproductive tissues

Coxiella burnetii

mainly asymptomatic in sheep, goats, cattle

reproductive failure often only clinical symptom

sporaic late term abortions, stillbirths, weak newborns, infetility

organisms shed in placenta, vaginal discharge, also in milk, urine, feces

Coxiella burnetii

Necropsy:

placentitis, rarely fetal lesions, esp pneumonia

Intercotyledonary placenta is thickened, opaque and multifocally covered by tan clumps of exudate.  margins of several cotyledons are tan (necrosis) and centers are mottled red-brown (congestion and exudation). 

Difficult to distinguish from brucellosis by appearance only

Coxiella burnetii

Diagnosis:

smears from placental tissue and uterine discharges stained with modified Ziehl-Neelsen (MZN) method or giemsa

can use immunofluorescence or immunohistochemistry with specific antibioties to confirm

Serology- complement fixation, ELISA, etc.

Coxiella burnetii

Treatment- not usually done

Control- standard with infectious abortion, careful disposal of placentas, etc, and segregation of animals that have aborted

Prevention- vaccines for domestic ruminants available in some countries but not in US

Coxiella burnetii

Zoonotic pathogen and potential biological warfare agent- vets, stockyard workers, sheep shearers, tanners, farmers are at risk

Humans- mid flu-like symptoms, with abrupt onset of fever, malaise, headache, myalgia, and symptoms of atypical pneumonia (dry cough, dyspnea, chest pain)

may also include GI symptoms, with nausea, and vomiting

chronic forms- may cause endocarditis

Rickettsia rickettsii

very small gram negative coccobacillary rods

obligate intracellular pathogens- must be grown in living hosts, tissue culture, embryonated eggs

true gram negative cell wall, with peptidoglycan and outer membrane with LPS, but gram stain poorly

more readily seen by immunologic methods with specific antibodies

Rickettsia rickettsii

reservoir: ticks, rodents

american dog tick, dermacentor veriabilis, and RM wood tick, D. andersonii

theses ticks can carry it at all life stages (larva, nymphs, adults) and transmit the bacteria transoverially

1-3 % of these ticks carry this disease

Rickettsia rickettsii

Transmission:

Tick bite-which requires attachment and feeding of tick for 6-20 hrs

less frequently, removal of tick from dog leads to human infecton via skin abrasion

april - october

Rickettsia rickettsii

cycle of ticks and hosts

infected tick larvae --> rodent  --> infected nymph tick --> infected adults --> dog/human --> infected tick eggs --> infected larvae

Rickettsia rickettsii

inoculated into the skin by a tick bite

spread through the bloodstream and infect cells of the vascular endothelium

trigger phagocytosis into these cells ( type IV secretion system)

once in phagosome they rapidly escape into host cell cytoplasm (phospholipase)

move on polymerized actin tails and escape into neighboring cells

primary lesion - vasculitis

endothelial damage triggers fibrinlytic and coagulagulation cascade

leads to thrombosis and leakage of RBCs into tissues causing rash and petechial lesions

leads to thrombocytopenia, DIC, vascular collapse, renal and heart failure

Rickettsia rickettsii

Clinical Signs

fever 4-5 days after tick bite

lethargy, anorexia, depression, diarrhea

cutaneous lesions include hyperemia and edema of extremities, ears, lips, scrotum

petechial lesions visible on oral and genital mucosa

ocular signs: conjuntivitis, retinitis, uveitis

arthritis, myalgia, stiffness, reluctance to walk

vestibular and neurologic signs

Rickettsia rickettsii

Necropsy:

widespread petechial and ecchymotic hemorrhages in all tissues

lymphadenopathy and splenomegaly

necrotizing vasculitis with perivascualr cuffing

Rickettsia rickettsii

Diagnosis

CBC- thrombocytopenia, leukocytosis with a left shift, prolonged coagulation time

Serology- IFA immunofluorescence assay, which can be used either with single serum looking for high titer or with paired sera looking for increase in titer

can also look for rickettsia in tissue (biopsies) of petechial lesions) by immunohistologic stain or by PCR

Rickettsia rickettsii

Rickettsia rickettsii

Treatment: tetracycline or oxytetracycline

Prevention: no vaccine

avoidance of tick-infested areas and prompt removal of attached ticks, and use of acaricides

Zoonotic: occurs in humand and dogs, but not spread from dogs to humans except via tick vectors. 

Dog disease sentinel for human disease

humans- major symptom is petechial rash with lesions on trunk, extremities, palms and soles

Neorickettsia (Ehrlichia)

risticii

gram negative coccobacillary rods

obligate intracellular parasites

tropism for monocytes

causative agent of potomac horse fever = equine

monocytic ehrilichiosis

first identified in 1979 in outbreak in Maryland

Neorickettsia (Ehrlichia)

risticii

Epidemiology

infectious but not contagious

occurs in sporadic localized epidemics

found in US, canada, S America, Europe

highest prevalence near large rivers

seasonal- most cases in summer and autumn in areas with cold winters, year-round in warmer areas

seen only in equids- rare in foals <1 year of age

Neorickettsia (Ehrlichia)

risticii

Reservoir: Trematodes found in fresh water snails and aquatic insects, life cycle involves trematodes (flukes), snails, aquatic insects, possibly bats or birds

Neorickettsia (Ehrlichia)

risticii

Transmission:

ingesition of aquatic insects, ingestion of trematodes or of grass contaminated with trematodes and snails

apparently NOT from biting insects

horses appear to be an accidental dead end host for an organism that normally cycles between trematode life stages in snails, aquatic insects, bats, etc.

Neorickettsia (Ehrlichia)

risticii

Life Cycle

horses ingest infected fluke larvae/or adult insects --> potomavac horse fever may develop in hoses, causing signs such as anorexia, fever, diarrhea, signs of colic, and laminitis --> neorickettsia risticii is the agent of the disease --> N. resticii - infected trematodes (flukes) --> snails --> water insects --> N. risticii move to aquatic insects (such as mayflies and caddisflies)

Neorickettsia (Ehrlichia)

risticii

Pathogenesis

after ingestion, bacteria infect blood monocytes

block phagolysosomal fusion and persist in monocytes

spread to GI, colonic epithelial cells, mast cells, and tissue macrophage

infection of GI leads to diarhea, due to disruption of sodium and chloride absorption and increased water loss in lg and sm colon

Neorickettsia (Ehrlichia)

risticii

Clinical signs:

incubation period: 2-3 weeks

acute onset of anorexia and depression, with rising fever (107C) decreased GI sounds

within 24-48 hrs moderate to severe diarrhea develops, from "cow-pie" to projectile watery diarhea

colic (mild to acute), subcutaneous ventral edema seen in some cases, dehydration, increased heart and respiratory rate

laminitis in 40% of cases, 5-30% fataltiy

may see abortion in mares that were pregnant when infected

Neorickettsia (Ehrlichia)

risticii

Diagnosis

Hematology - leukopenia and neutropenia with left shift, thrombocytopenia, hemoconcentration

Blood chemistry - hyponatremia, hypokalemia, hypochloremia, metabolic acidosis

definitive diagnosis base on isolation of N. risticii from blood (10d) or feces (13d) of infected horses, or PCR

Serology- IFA (indirect immunofluorescence assay) used, but high rate of false positives

Neorickettsia (Ehrlichia)

risticii

Neorickettsia (Ehrlichia)

risticii

Necropsy

subcutaneous edema of ventral body wall

very fluid consistency to contents of colon

cecum and colon- congestion, hemorrhage, and scattered mucosal erosions

swollen edematous mesenteric lymph nodes

detect organisms in tissue with silver stain or immunohistology

aborted fetuses have enterocolitis and necrosis of mesenteric lymph nodes

Neorickettsia (Ehrlichia)

risticii

Treatment: oxytetracycline IV for 5-7 days

Prevention: inactivated whole cell vaccine (6 mo or before summer), 1 strain of Mr, and may provide minimal protection against other strains

No Zoonotic potential- not a human pathogen

Anaplasma marginale

Anaplasma ovis

infect erythrocytes

cattle, sheep, goats

Anaplasma phagocytophilum

Ehrlichia ewingii

infect granulocytes

tick-borne fever in ruminans; equine, canine, human granaulocytic anaplasmosis

canine granulocytic ehrlichiosis

Anaplasma platys

Infect platelets

canine cyclic thrombocytopenia

Ehrlichia canis

Infect monocytes and macrophages

canine monocytic ehrlichiosis

Ehrlichia ruminatium

Infect macrophages and vascular endothelial cells

heartwater

Anaplasma

&

Ehrlichia

small gram negative coccobacilli

do not have peptidoglycan cell walls

obligate intracellular parasites

(cannot be cultured ex. in tissue culture or egg yolk sac)

tropism for hematopoietic cells- RBCs, granulocytes, monocytes, platelets, seen in bloodsmears by giemsa stain (purplish-blue small organisms individual or clusters- morulae)

vector borne- ticks

Anaplasma marginale

Anaplasma ovis

Anaplasmatosis (gall sickness)

cattle, sheep, goats, other ruminants

worldwide in tropical and sub-tropical regions--> south/central America, US, S. Europe, Africa, Asia, Australia

infect erythrocytes- wright-giemsa stain

basophilic intracellular organisms, spherical incusion near margins

Anaplasma marginale

&

Anaplasma ovis

Reservoir: infected carrier animals

Transmission: ticks, iatrogenic (needles, dehorning tools, etc), seasonal- vector season, trans-stadiallly but not trans-ovarially in ticks

Pathogenesis: infect mature erythrocytes --> multiply within membrane-bound vesicles, at edge of erythrocyte --> exit via exocytosis, and infect more RBC --> parasitized RBC are removed by macrophages

Anaplasma marginale

&

Anaplasma ovis

Clinical signs:

incubation period: 3-4 weeks, number of infected RBC doubles every 24-48 hrs

requires about 15% RBCs to be infected for apparent clinical signs--> fever, anorexia, weight loss, icterus (jaundice)

acute disease--> severe anemia, pale mucous membrane, lethargy, no hemoglobinemia, hemoglobinuria (destruction of erythrocytes), fever, death

many animals survive emaciated condition - subclinical carriers

more severe in adult animals >3 yrs --> young generally become sub-clinically infected- carriers

peracute cases- affected animals are hyperexcitable and tend to attack attendants just before death

Anaplasma marginale

&

Anaplasma ovis

Diagnosis:

clinical signs in endemic areas, marked anemia, jaundice in absence of hemoglobinuria

hematology: giemsa stained bloodsmear showing densly staining bodies near periphery of RBCs

Immunofluorescence or PCR

Serologic testing (ELISA, CF) detect chronic carriers

Anaplasma marginale

&

Anaplasma ovis

Anaplasma marginale

&

Anaplasma ovis

Treatment: long acting oxytetracycline

Prevention: vaccination (killed or live attenuated) prior to introduction to endemic areas can prevent severe disease but not carriage

- weekly dipping in acaricide to reduce tick burden

- testing herd and removing carriers

Ehrlichia (Cowdria)

ruminantium

causative agent of heartwater in domestic and wild ruminants- REPORTABLE

found in sub-saharan Africa and Carribean islands

transmitted by amblyomma ticks- not currently in US but could be imported

replicates in macrophages and vascular endothelial cells of capillaries, esp. nervous system leading to increased vascular permeability

found as clumped organisms at ends of nuclei in cytoplasm of brain capillary endothelial cells

Ehrlichia (cowdria)

ruminatium

clinical signs: sudden fever, neurologic signs (chewing movements, exaggerated blinking, high stepping, circling,  prostration, convulsions) in less acute cases- neuro signs are inconsistant

Necropsy: extensive edema (pericardium, thorax, lungs, brain), splenomegaly, extensive mucosal and serosal hemorrhages

Treatment: tetracycline administered early in disease, tick control

Anaplasma phagocytophilum

causative agent of tick-borne fever in cattle and ruminants as well as equine, canine and human granulocytic anaplasmosis

more common in older animals

infects granulocytes, where it forms microcolonies called morulae

Anaplasma phagocytophilum

Reservoir: infected carriers, deer, white-footed mice, squirrels, other small rodents

Transmission: tick bites, trans-stadially but not trans-ovarially in ticks

found worldwide in northern latitudes (europe, US, etc) upper midwest and northeastern regions and pacific coastal states

Anaplasma phagocytophilum

Pathogenesis

bacteria injected through dermis by tick bite --> phagocytized by neutrophils

do not stimulate oxidative burst, and block subsequent oxidative responses (immunosuppresion)

block maturation of phagosome at early stage- does not acquire early endosomal markers, does not acidify or acquire V-ATPase

multiply within membrane-blound vacuole

delays apoptosis of infected cells

immunosuppression predisposes to opportunistic infections

Anaplasma phagocytophilum

Ruminants Clinical Signs

incubation period of 5-14 days, occurs after moving animals to tick-infested pastures, esp in spring

sudden fever lasts 4-10 days, may recur

reduced appetite, lethargy, decreased milk production, weight loss, cough, resp. distress

pregnant animals in late gestation may abort

immunosuppression, increased susceptibility to many other infections

transient thrombocytopenia, prolonged leukopenia

Anaplasma phagocytophilum

Horse Clinical Signs

incubaton 8-14 days

severity of clinical signs varies with age >4 years most severe

fever, depression, reduced appetite, limb edema, petechiation of mucosal membrane, icterus, ataxia, staggering, reluctance to move, base-wide stance, weakness, ataxia may be severe (fractures possible), abortion, laminitis, immunosuppression, increased susceptibility to other infections

Anaplasma phagocytophilum

Diagnosis-

clincial signs and geographic area, time of year

ID morulae in neutrophils, cytology, PCR

Lab findings- leukopenia, transient thrombocytopenia

morulae in nuetrophils and eosinophils

Treatment- long acting tetracycline

Prevention- no vaccine, tick control

Ehrlichia canis

causative agent of canine monocytic ehrlichiosis

Reservoir: domestic and wild canids

Transmission: ticks

found world wide in tropical and subtropical areas

Ehrlichia canis

Pathogenesis & Clinical Signs

incubation period 1-3 weeks

bacteria replicate in monocytes, and macrophages- block phagolysosome fusion

acute phase: fever, depression, lethargy, petechial lesions, swollen lymph nodes and spleen, mild weight loss, epistaxis

cytology: thrombocytopenia, leukopenia, anemia

w/o treatment generally progresses to subclinical phase, with persistent carriage in spleen and persistent thrombocytopenia

chronic: some dogs develop persistent bone marrow depression, pancytopenia, uncontrolled bleeding, secondary infections

Ehrlichia canis

Ehrlichia canis

Diagnosis:

cytology: morulae in monocytes

thrombocytopenia, leukopenia, anemia

blood chemistry: hypergobulinemia, elevated liver enzymes

antibody titers to hyperglobulinemia, elevated liver enzymes

antibody titers by indirect FA

Ehrlichia canis

Treatment: tetracycline or oxytetracycline

Prevention: no vaccines, avoidance of tick-infested areas, prompt removal of ticks, and topical acaricides

thrombocytopenia with infection of monocytes- decreased production of platelets from hypoplastic bone marrow, seqestration, increased consumption, secretion of platelet-migration inhibiton factor my lymphocytes exposed to infected cells

Ehrlichia ewingii

causative agent of canine granulocytic ehrlichiosis

Reservoir: domestic and wild canids, deer

Transmission: ticks

found US, south and southeast

younger animals

Ehrlichia ewingii

Pathogenesis and Clinical Signs

bacteria multiply in phagosomes in neutrophils (granulocyes)- block phagolysosomal fusion

acute fever, depression, lethargy, acute polyarthritis, lameness

Neuro signs- ataxia, tremors, vestibular defects

difficult to distinguish from A phagocytophilum infection

Ehrlichia ewingii

Diagnosis: thrombocytopenia, morulae in neutrophils, neutrophilic polysynovitis, no specific serotest, PCR testing

Treatment: tetracycline or oxytetracycline

Prevention: no vaccines available, avoid tick-infested areas and prompt removal of attached ticks, topical acaricides

Anaplasma platys

causative agent of canine cyclic thrombocytopenia

Reservoir: domestic and wild canids

Transmission: ticks, proably but not proven

found worldwide, including southern US

organism has never been cultured

Anaplasma platys

Pathogenesis

bacteria infect and multiply in platelets (not in megakaryocytes in bone marrow)

leads to massive drop in platelet count, which resolves

bacteremia and thromocytopenia recur repeatedly at 1-2 week intervals

Anaplasma platys

Clinical Signs: acute fever, lethargy, pale mucous membranes, petechial hemorrhages of skin and oral, bleeding

Diagnosis: thrombocytopenia, morulae in platelets (seen in mycroscopy or fluorescent Ab staining), indirect FA test for serum antibodies

Treatment: tetracycline or oxytetracycline

Prevention: no vaccine , avoid tick infested areas and prompt removal, topical acaricides

Haemotropic Mycoplasmas

small uncultureable bacteria, formerly classified as rickettsia but reclassified based on small size, lack of cell wall, and resistance to penicillin

associate with surface of erythrocytes (not intracellular) and cause severe hemolytic anemia

Mycoplasma haemofelis

feline infectious anemia

occurs worldwide- strongly associated with male sex and access to outdoors

Reservoir- infected cats

Transmission: not certian, possibly fleas or bite wounds, experimentally through blood transfusion

Mycoplasma haemofelis

bacteria attach to the surface of erythrocytes - not intracellular

damage to erythrocytes --> direct damage by pathogen, immune-mediated mechanisms

Mycoplasma haemofelis

Clinical Signs

anemia, lethargy, mucosal pallor, tachypnea, tachycardia

severe disease- profound anemia, overwhelming parasitemia rapidly results in death

more commonly- mild disease with anemia and jaundice

immunocompetent cats- successive waves of parasitemia are gradually eliminated by immune response

Mycoplasma haemofelis

Diagnosis:

demonstration of bacteri on surface of RBCs in giemsa-stained smears

PCR to identify organism in blood

hematology: may see reduced packed cell volume and evidence of regenerative anemia

Treatment: doxycycline, blood transfusions

Mycoplasma haemocanis

hemotropic mycoplasmosis in dogs

milder disease in dogs, clinical signs apparently in normal dogs

transmitted by brown dog tick

forms chains of organisms across the surface of the erythrocyte

Mycoplasma haemosuis

hemolytic anemia in pigs

maninly young piglets

organisms on surface of erythrocytes and free in plasma

Chlamydophila felis

causative agent of conjunctivitis and rhinitis in cats

"feline pneumonitis" misnomer rarity of lower respiratory disease with pathogen

gram negative bacterium

obligate intracellular pathogen with unique developmental cycle - grown in tissue culture, does not grow in standard media

Chlamydophila felis

unique developmental cycle includes infectious form and replicative form

elementary body (EB): hardy, extracellular form, non-replicative, but infectious--> can survive in environment

Reticulate body (RB): fragile, metabolically active and replicative --> does not survive in environment

Chlamydophila felis

Developmental cycle:

elementary bodies (infectious form) attach to host cells--> taken up by receptor mediated endocytosis and block maturation of phagosome--> EBs reorganize into RBs (replicative form)-> multiply--> some continue replication others tranform to EBs--> inclusion body contains both --> cell lysis with release of infections EBs and loss of RBs

Chlamydophila felis

Reservoir: cats

Transmission: direct contact or aerosols, transmitted to kittens through parturition, venereal transmission (not proven)

Clinical signs: conjunctival hyperemia (redness), chemosis (swelling of conjunctiva), blepharospasm, serous to mucopurulent ocular discharge, sneezing, nasal discharge

Chlamydophila felis

Chlamydophila felis

Diagnosis:

stained conjunctival smears showing intracytoplasmic inclusions (giemsa or iodine)

culture in tissue culture

PCR, commercial ELISA

Treatment: tetracycline

Prevention: live and inactivated vaccines are available

Moraxella bovis

Short fat gram negative rods, usually in pairs

aerobic, oxidase positive

grow on blood, beta-hemolytic, NG on MacConkey

causative agent of infectious bovine kerato-conjunctivitis

Moraxella bovis

Reservoir: carrier cattle - carriage in conjunctiva, nares, vagina, occurs worldwide

Transmission: mainly face flies, direct contact, tall grass, etc.

Moraxella bovis

Virulence factors:

Pili- two different types involved in adherence to cornea, extensive antigenic variation in amjor pilus protein

RTX hemolysin- kills neutrophils and damages corneal tissue

Loss of either pili or toxin leads to avirulence

Moraxella bovis

Pathogenesis

bacteria transmitted by face flies attach to corneal surface via pili, which allows bacteria to circumvent clearance by lacrimal secretions and blinking

replicating bacteria produce a calcium-dependent RTX hemolysin that damages corneal tissue and causes corneal erosions within 12 hrs

inflammatory response brings neutrophils to infected area

toxin kills neutrophils and release of hydrolytic enzymes from neutrophils contributes to corneal damage

Moraxella bovis

Clinical signs

incubation period 2-3 days

early signs are edema and infection of the conjunctiva, accompanied by copius watery lacrimation, blepharospasm and photophobia

may have low fever, decrease in milk yield and decrease appetite

after 1-2 days, a small opacity appears in the center of the cornea that may become elevated and ulcerated over the 2-4 days- peak infection may cover entire cornea

in most cases- cornea will heal within few weeks, but some animals may develop severe ulceration resulting in blindness

Moraxella bovis

Moraxella bovis

Diagnosis:

affects many animals in a herd

culture of lacrimal secretions on blood agar and MacConkey (should yeild beta-hemolytic colonies on blood and NG on MacConkey)

confirm biochemical tests or PCR

Treatment: topical antibiotics, parenteral oxytetracycline

Prevention: pilus and hemolysin vaccines are available but have limited efficacy, fly control

Leptospirosis

Worldwide zoonotic disease, almost all mammals susceptible

gram negative bacteria

over 250 serovars

Leptospirosis

Disease characteristics

depends on host/serovar combination

age and condition of animal

certain serovars prevalent within an area

each serovar has one or more maintenance hosts in an ecosystem --> wildlife, domestic animals

Leptospirosis

maintenance host: perferred host, obvious illness rare, organism persists, long term shedding, low titers of Ab, reservoirs of infection, vary infectious

Incidental host: all mammals except maintenance host, severe disease common, organism cleared, little shedding, high titers, transmission to other animals is rare

E. coli

Virulence Factors

pili and toxins encoded

capsular polysaccharide = K antigen

endotoxin

Fibrial adhesins (K, F, P)

K88 (F4) pigs, K99 (F5) calves, lambs, pigs, pups

987P (F6) neonatal pigs, F18 - older pigs

F41- calves

bundle forming pili, intimin, and Tir

Leptospirosis

clinical signs- incidental hosts

fever, anorexia, vomiting/diarrhea, bleeding, hemolytic anemia, jaundice, renal failure, abortion storms --> livestock and horses

Clinical signs- maintenance hosts

subclinical infections, develop clinical signs as sequelae in chronic infection

dogs- end-stage kidneys and chronic renal failure

cattle- infertility and late term abortions

Hardjo

Pomona

Grippotyphosa

Icterohaemorrhagiae

Canicola

E. coli

Protein Exotoxins

Heat Labile toxin: LT

AB subunit protein exotoxin

A active unit, B binding unit

increases cAMP in GI, extensive watery diarrhea

Heat stable toxin: ST

small peptide toxin binds and increases cGMP

bratislava

maintenace host --> pigs, horses

Lepto

infection spread by contact with urine from infected animals

organism thrives in moist warm climates

can survive outside the body for several months

infection rates in maintenance host are often 30% or higher

Routes of infection: ocular, oral, reproductive, skin

Lepto

Pathogenesis:

penetrates mucous membranes --> bacteremia --> liver, kidney, spleen, CNS, etc --> antibodies develop

maintenance hosts --> privileged sites --> long term shedding

Incidental hosts --> recovery with short term urinary shedding

Lepto

Virulence factors:

motility, hemolysins, LPS- not toxic, cytotoxins

varies from region to region

increase rainfall --> increase incidence

more common in spring and fall

Lepto

Diagnostics

Indirect --> serology

Direct -->

fluorescent antibiotic test- sensitivity, live organisms not required, rapid, inexpensive, can be used on frozen tissues

Immunohistochemistry- insensitive, silver-stains tricky, inexpensive, widely available, fixed tissue

Culture- definitive, identify serovar, expensive, difficult, long time, live organism

PCR- sensitive, not serovar specific, expensive, rapid, technically demanding

Microscopic agglutination test

used for Lepto

widely available, relatively specific

insensitive for some serovars

vaccination complicateds interpretation

highest titer = infecting serovar

titers likely to be low in acute stages of disease

Interpretation--> do not compare between labs, cross-reactivity common, vaccine titers 60-120 days- titers to multiple serovars

Lepto

first described in 1899- canicola, icterohaemorrhagiae

dogs main source of exposure

vaccines developed

prevent disease well, may not prevent infection

incidence dropped dramatically

Reemergence- serovars involved

increased diagnosis = increased in disease

BPP: Bolin's Prevalence Postulate

No of diagnoses = Z x N x L

Z= the true incidence of the disease

N= the number of animals at risk

L= number of leptospirologists in the area

Lepto

Cross reaction = Cross protection

infection and vaccination with one serovar induces antibiodies that react with other serovars

certain patterns of x-reactivity are typical

dogs infected with grippo, also have titers against Brat and Pomona

immunity is serovar specific

Lepto

Vaccination titers lasts for 60-120 days ex. w/repeated vacc

titers to multiple serovars

2-way products--> canicola, Icterhaemorrhagiae

4-way producs --> canicola, icterohaemorrhagiae, groppotyphosa, pomona (whole-cell, adjuvant, unadjuvant)

initially 2 doses required, yearly for most dogs

every 6 months for high risk dogs or evironments

Lepto

Bovine

common: hardjo, pomona, grippotyphosa

occasional: icterohaemorrhagiae, canicola, bratislava

vaccines: whole-cell inactivated, alum adjuvant, 5 or 6 serovars, given before breeding

Lepto

Dogs: supportive care, 'cillin' when they are sick, 'cycline' for 3 weeks as they recover

Cattle: tetracyclines and vaccine will stop abortion storms, long acting tetracycline, or tilmicosin for chronic infections (primarily hardjo)

Lepto

Zoonotic

occupational exposure--> in lab, working with animals, agriculture workers, handling body fluids, care when washing out cages/runs, need a clinic plan in case of exposure

client education- vaccination of dogs/livestock, care when handling urine, realistic risk assessment, provide an information sheep

Recreational exposure- exposure to open bodies of fresh water, hunting

Increasing prevalence of lepto in companion animals

Spirochetes

includes- treponema, borrelia, leptospira, brachyspira

Spiral motile gram negative bacteria with endoflagella located in periplasmic area between cell membrane and outer membrane

labile in environment, sensitive to dessication, require specialized media (can be grown in vitro)

Lepto

Spirochete

found in aquatic envrionements, cause systemic infections in many species

Brachyspira

Spirochete

intestinal some of which are importen pathogens in pigs (hyodysenteriae)

Borrelia

spriochete

transmitted by arthropod vectors, cause systemic infections in many species

Genus Borrelia

helical gram negative bacteria

corkscrew motility due to endoflagella

unique linear chromosome, multiple circular and linear plasmids

obligate parasites of vertebrate hosts --> do not survive well in envrionment

transmitted via arthropod vector

Borrelia burgdorferi

Borrelia anserine

Borrelia burgdorferi

first identified following cluster of arthritis in children

reported in humans, dogs, horses, cattle, and sheep

Reservoir: variety of small mammals, such as white-footed mouse, also deer, sheep, and other large mammals maintenance host for ticks. humans, dogs, horses are incidental hosts

Transmission: tick bites, Ixodes scapularis- eastern and central US, Ixodes pacificus- west coast

Borrelia burgdorferi

virulence factor

outer surface proteins (OspA-F)

is expressed in tick midgut and is required for adherence

during tick feeding, OspA is turned off and OspC turned on, which releases bacteria from tick midgut and help protect bacteria from complement mediated killing host

VIsE is a variable surface protein expressed in mammalian hosts, which continually alters its antigenic region to help evad immune response

Borrelia brugdorferi

Pathogenesis

transmitted into mammalian hosts by tick bites--> requires attachment and feeding for 48hrs --> multiply within the skin but spread then to bloodstream or migrate through tissues --> many symptoms likely to be due to immune responses, esp migrating polyarthritis

Borrelia burgdorferi

early infection: erythma migrans appear around bite with 3-30 days after tick bite (80% of people), persist for 3-4 weeks

can be isolated/identified in skin

classic "bull's eye" rash (erythema migrans) of lyme disease

Borrelai burgdorferi

dissemination stage- weeks to months following infection

spread hematogenously to additional body tissues

symptoms- fatigue, chills, fever, headache, muscle and joint pain, swollen lymph nodes, secondary annular skin lesions

nervous systme abnormalities can include numbness, pain, bell's palsy (paralysis of facial muscles), and meningitis (fever, stiff neck, and severe headache)

can be identified in bloodstream, joints, CNS

Borrelia burgdorferi

persistent infection

typically involves intermittent episodes of joint pain and swelling, usually in one ore more large joints and migratory pain to joints, tendons, muscle, and bone

generally do not see spirochetes in joint fluid - may be due to deposition of immune complexes

Borrelia burgdorferia

Clinical disease in dogs

about 5-10% of dogs develop clinical disease after exposure (2-6 months)

difficult to determine actual time of infection, since dogs do not develop erythema migrans (transient redness)

more severe in younger animals

clinical signs- fever, shifting leg lameness, swelling of joints, polyarthritis, lymphadenopathy--> responsive to antibiotic therapy at early stages but polyarthris may respond

Acute progressive renal failure can occur, protein-losing glomerulopathy associated with proteinuria, uremia, peripheral edema, vomiting, concurrent lameness, euthanized, no bacteria in kidneys

mild focal meningitis, but neuro signs not observed

Borrelia burgdorferi

Borrelia burgdorferi

horses- many clinical signs have been attributed to disease but no produced experimentally

clinical signs frequently reported include low grade fever, stiffness, lameness in more than one limb, muscle tenderness, lethargy

both neurologic dysfunction and panuveitis reported

high fever, and limb edema have been reported but more likely due to concomitant infection with anaplasma phagocytophila (spread via same tick)

Borrelia burgdorferi

Borrelia burgdorferi

Diagnosis

history of exposure to ticks in endemic area with clinical signs

Detection of organisms

culture (difficult and expensive) in specialized medium take 6+ weeks, rarely done

PCR detection of bactrial DNA in samples such as skin

immunolfuorescence or darkfield microscopy

Serologic diagnosis

demonstrates rising antibody titers, not confirmatory alone

ELISA and indirect FA tests using whole bacteria as antigens may have false positives with animals infected with other spirochetes

western blotting can differentiate Ab resposnes- time consuming and training (confirmatory)

solid-phase ELISA tests for VIsE protein- differentiates infected from vaccinated

Borrelia burgdorferi

Treatment:

tetracyclines - because they are effective against causes of similar clinical signs

acute disease- rapid improvement

chronic diease- prolonged therapy

Borrelia burgdorferi

Prevention:

acaricidal sprays, tick control

vaccines include whole cell bacterins and recombinant subunit vaccines

OspA vaccines stimular production of Abs that can kill bacteria in tick midgut after ingests blood

benefits of vaccinating are disputed

Borrelia burgdorferi

most frequently resported tick borne disease of humans in NA

dogs can act as transport hosts for infected ticks, exposing humans to risk of infection

Staph aureus

gram positive cocci clusters

pyogenic- pus forming

catalase positive, coagulase positive

beta-hemolytic on blood agar

Invasive and toxigenic

Staph aureus

Staph aureus

causes:

skin infections, abscesses, wound infections, pneumonia, septicemia, osteoarthritis

scaled skin syndrome, toxic shock syndrome, exudative epidermis, food poisoning

Staph aureus

reservoirs: skin and anterior nares about 25% of all humans and animals

Transmission: mainly direct contact but also by direct injection, or aerosols

very common nosocomial pathogen in humans and animals

Staph aureus

adhesins- MSCRAMMS- fibronectin and collagen-binding proteisn, linked to cell wall peptidoglycan

anti-phagocytic surface molecules--> protein A binds immunoglobulins by Fc end, capsule

Staph aureus

Exotoxins:

multiple cytolysins/hemolysins (alpha, beta, gamma, delta - toxin, panton-valentine leukocidin)

exfoliating toxins

pyrogenic exotoxins = superantigen toxins, toxic shock syndrom toxin, enterotoxins

Staph aureus

Exoenzymes

spreading factors- degradative enzymes that break down host tissues and intracellular matrix, such as collagenase, hyaluronidase, proteases, DNase, staphylokinase (fibrinolysin), etc

Coagulase- activates thrombin, leads to conversion of fibrinogen to fibrin = forms fibrin clots around bacteria

Staph aureus

Pore-forming cytolysins

alpha toxin- lyses host cell membrane and kills host cells, toxic for neutrophils, important cause of localized tissue damage

panton-valentine leukocidin- toxic for neutrophils and macrophages, has been linked to severe necrotizing pulmonary and cutaneous disease and to community-aquired MRSA

Staph aureus

Exfoliating toxins

proteases that target the intercellular adhesion protein desmoglien, found only in the epidermis, and specifically destroy desmosomes that connect epithelial cells, causing separation of layers of epidermal cells

cause sloughing of skin around lesions such as boils or cause bullous impetigo

systemic infections can cause scalded skin syndrome, symptoms of toxic shock syndrome

Staph aureus

superantigen toxins

Enterotoxins- cause food poisoning, ingested as pre-formed toxin, very heat stable, trigger vomiting and abdominal pain, rapid onset due to intoxication not infection

Toxic shock syndrome toxin- superabsorbant tampons, toxin can cross mucosal barriers and spread systemically from localized infection, causes massive release of cytokines from T cells, leading to vascular leakage, shock and death, causes supersensitivity to other toxins like exfoliating toxins and endotoxin

Staph aureus

soft tissue infections--> boils, furuncles, carbuncles, other abscesses, impetigo, superficial dermatitis, wound infections

septicemia, osteoarthritis, pneumonia, toxinogenic disease, scalded skin syndrome = systemic effect of exfoliating toxin

Staph aureus

salt and acid tolerance- established in hair follicle or sebaceous gland or minor wound

alpha toxin or leukocidins- localized tissue necrosis, kill phagocytes that migrate to area, causing degranulation, toxic for skin, muscle, WBCs

Staph aureus

evasion of host immune system

main host defense is PMNs but it can evade

leukocidins and hemolysins act to kill phagocytic cells

Protein A inhibits phagocytosis and blocks antibody function, capsule inhibits phagocytosis

catalase helps resist oxygen-dependent phagocytic killing mechanisms

Staph aureus

Staph aureus

Diagnosis: based initially on lesion appearance and location, time of year, pruritis, othe animals affected

culture of pus on blood agar or CNA or mannitol salt agar

hemolysis and colonial morphology on blood, growth and mannitol fermentation on MSA

gram stain and morphology

catalase and coagulase test

Staph aureus

Antibiotic resistance

major problem 90% resistant to penicillin

many often resistant to other classes except vancomycin and new oxazolidinones

resistant isolates now very common in many species

Staph pseudointermedius

Staph pseduointermedius

gram positive, pyogenic, coccus, catalse positive

coagulast positive, beta-hemolytic on blood agar

most common cause of canine pyoderma

also cats, rarely horses and cattle

Staph pseudointermedius

Reservoir: skin, mucosal areas of dogs, puppies aquired it from dams within 8 hrs after birth, normal flora

disease requires some distubance in host, wounds, or infections, immune dysfunction

Staph pseudointermedius

virulence factors

adhesins, anti-phagocytic surface molecules - protein A- binds immunoglobulins by Fc end, capsule

exoenzymes- spreading factors, coagulase

exotoxins- cytolysins, exfoliating toxin, superantigen toxins

Staph pseudointermedius

canine pyoderma

pyogenic or pus-producing skin infection

classification based on depth--> suface, superficial, deep

treat with beta-lactamase resistant cephalosporins or clindamycin

Staph pseudointermedius

diagnosis:

examination of skin scrapings

culture of pus on blood agar or CNA or mannitol salt agar

hemolysis and colonial morphology on blood, growth and mannitol fermentation on MSA

gram stain morphology, catalase and coagulase test

staph pseudointemedius

Corynebacterium Pseudotuberculosis

gram positive, rod, catalase positive, small zone beta-hemolysis on blood agar

Reservoir: infected animals and organisms in soil, pastures, facilities, shearing tools, etc, contaminate with bacteria, long term survival in soil

Corynebacterium pseudotuberculosis

Ovis: non-nitrate reducing

causes caseous lymphadenitis in sheep and goats

Corynebacterium pseudotuberculosis

equis: nitrate reducing

causes ulcerative lymphangitis in horses and cattle

Coynebacterium pseudotuberculosis

Transmission:

in sheep and goats- primarily due to small wounds such as shearing wounds

In horses and cattle- mainly due to insect bites and skin wounds

Corynebacterium pseudotuberculosis

virulence factors

phospholipase D (Pld) an exotoxin that degrades mammalian cell membranes, is leukotoxic, and can damage endothelial cells and promote spread from initial site of infection to regional lymph nodes and visceral organs

cell wall is distinctive, with arabinogalactan and corynemycolic acid components- chemical composition enables organism to resist being killed in a phagolysosomes within macrophages and trigger granluomatous infection

facultative intracellular pathogen with ability to survive and multiply within phagolysosomes

caseous lymphadenitis

one of most important bacterial infections of small ruminants - sheep and goats worldwide

major economic importance- decrease yield of wool, meat, increased culling, thin ewe syndrom, condemnation at slaughter

chronic abscessation of peripheral lymph nodes (may be in visceral lymph nodes)

Caseous lymphadenitis

corynebacterium pseudotuberculosis

pathogenesis:

enter through small wounds--> multiply --> trigger inflammatory response and influx of first PMNs then macrophages --> phagocytized, survive, carried to lymph nodes --> multiply tigger granulomatous response --> classic lesions

Caseous lymphadenitis

animals chronically infected

endemic areas adult animals may have lesions with no clinical signs

visceral abscesses occura and lead to thin ewe syndrome

abscesses rupture and drainage can contaminated environment

Corynebacterium pseudotuberculosis

Corynebacterium pseudotuberculosis

Diagnosis:

based initially on lesion appearance, which is considered diagnostic in herds with history of CLA

Confirmation:

culture pus

gram stain and cell morphology

hemolysis pattern with synergistic hemolysis with Rhodococcus equi and inhibition of Staph aureus  beta-hemolysis (reverse CAMP test)

Corynebacterium  pseudotuberculosis

Treatment

drainage or surgical removal of abscess, decontamination

pus collected and burned

quarantine affected animal

antibiotics don't work well but combo of erythromycin and rifampin for 4-6 weeks has been suggested

Corynebacterium pseudotuberculosis

Control:

eradication extremely difficult- culling of serologically positive animals

If herd is free, extreme care should be taken to keep it that way

vaccines available-bacterins and pld toxiod

management CRITICAl

Corynebacterium pseudotuberculosis

Ulcerative lymphangitis

worldwide, US mainly southwest during dry season

associated with insect vectors

external abscess most common forms- primarily in pectoral region and along ventral midline of abdomen, lg amounts of pus, encapsulated, severe edema

limb swelling, cellulitis, draining tracts following lymph vessels

Corynebacterium pseudotuberculosis

pigeon fever

corynebacterium pseudotuberculosis

Diagnosis:

clinical presentation

culture, gram stain, cell morphology

hemolysis pattern with synergistic hemolysis with Rhodococcus equi and inhibition of S. aureus beta-hemolysis (reverse CAMP test)

Serology- synergistic hemolysis inhibition test for Abs against pld, difficult to distinguish active infection from exposure or convalescence

corynebacterium pseudotuberculosis

Treatment:

external abscesses- drainage of abscess, decontamination

pus collected and burned

internal abscesses require long term antibiotic therapy, generally rifampin plus another antimicrobial

Ulcerative lymphangitis- treat early and aggressively, oral rifampin and IV cephalosporin, till improves, then trimethoprim-sulfa and/or rifampin fro 4-6 weeks

Mycobacterium bovis

phagocytic cells, such as macrophage:

pathogens are engulfed into phagosome and survive by blocking killing mechanisms, such as oxidative burst and maturation and/or acidification of phagosomes

Corynebacterium pseudotuberculosis

Prevention/Control

vaccines are available for small ruminants but not tested for efficacy in horses

strict insect control critical

proper sanitation to reduce spread to other horses

Genus Clostridium

large gram positive spore-forming rods, anaerobic

Reservoirs: soil and gastrointestinal tracts of animals

Transmission: wound contamination or ingestion

Genus Clostridium

Endospores

specialized structures that are highly resistant to advers conditions

produced under nutrient limitation or other stress

sporulation= formation of spore from vegetative cell = complex developental process require regulatory cascade

exotoxins are key virulence factors

Clostridium perfringens A

causes gas gangrene and myonecrosis in warm-blooded animals

alpha toxin and perfringolysin

endospores enter into tissue by injury (punture or injections) which causes sufficient damage to tissue and blood supply (anerobic atmosphere)

multiply, produce toxins, local tissue destruction

Clostridium perfringens A

growth of bacteria produces gas, emphasematous/crepitant appearance

hemorrhage, edema, tissue necrosis, with gas

death from toxemia and/or septicemia

gas gangrene caused by one of several species, this being the most common

Clostridium perfringens A

Diagnosis:

based on history of recent IM injection, penetrating injury, plus gross pathology and histopathology

gram positive bacteria isolated using anaerobic culture, fluorescent antibodies

Clostridium perfringins

five types defined on presence or absence of 4 different toxins

alpha, beta, epsilon, lota

A, B, C, D, E

alpha toxin

beta toxin

Epsilon toxin

Lota toxin

perfingolysin

Clostridium perfingens A

Clostridium perfringens B

Clostridium perfringens C

Clostridium perfingens D

Clostridium perfringens E

Clostridium perfringens A

Clostridium perfringes A

Treatment

immediate very high dose of penicillin, with possible addition of rifampin or metronidazole

myotomy and fasciotomy to allow drainage and debridement of necrotic areas and oxygenation of tissues

hyperbaric oxygen if available, or infusion of oxygen into tissues

Clostridium

control

vaccines that elicit antibodies that neutralize toxins

bacterin and toxoid and combo vaccines are available

Clostridium tetani

an acute toxemia that affects almost all mammals, horses and humans suceptible, dogs/cats/birds relatively resistant

major symptom - spastic paralysis

major virulence factor - tetanospasmin

AB subuint exotoxin

Clostridium tetani

B subunit - binds to gangliosides on CNS neurons

A subunit - zinc-dependent matalloprotease that cleaves synaptobrevins (proteins found in synaptic vesicles of neurons) essential for release inhibitory neurotransmitters  - GABA

leads to unregulated excitatory synaptic activity in  motor neurons, resulting in spastic paralysis

toxin binding is irreversible, recovery depends on whether new axonal terminals form

spastic paralysis

Clostridium tetani

Pathogenesis

reservoir: bacteria in GI tracts of humans and animals, spores in soil (persistent)

Transmission: injection of spores into a deep traumatic wound

tissue necrosis and anoxia environment for germination, growth and production of toxin

toxin spreads systemically by retrograde transport up nerve fibers to CNS or via bloodstream

early signs muscle stiffness accompanied by muscular tremor and increased responsiveness to stimuli

Clostridium tetani

trismus= spasm of jaw muscles with resitriction of jaw movement and inability to eat

grinding teeth, retraction of third eyelid, erect ears, unsteady straddling gain with tail head out stiffly, anxious expression

severe muscle spasms and convulsiosn

death caused by paralysis of respiratory muscles

Clostridium tetani

infected cats...from bite wounds do not seem to develop full systemic disease, instead symptoms are apparent mainly in limb where the bite wound is located

particularly a problem in neonates, including humans, foals, lambss

can occur due to infection of the umbilicus, castration, or docking

Clostridium tetani

Clostridium tetani

Diagnosis

mainly based on the clinical signs and a history of recent trauma in unvaccinated animals

can attempt culture of organism from wound or assay of toxin from bloodstream (difficult)

differential - fully developed is clinically distinctive

early stages confused with meningitis, encephalitis, sarcocystis, rabies, strychnine poisoning, myositis, acute laminitis in horses

Clostridium tetani

Prevention

vaccination toxoid, inactivated but still immunogenic toxin protein.  given routinely to horses, humans initially 2 doses followed by regular boosters

vaccine provides long-lasting protection but immunity takes 7-10 days after 2nd shot

antitoxin provides protection in 2-3 hrs but only lasts 2-3 weeks

Clostridium botulinum

acute intoxication acquired by pre-formed toxin

major symptom - flaccid paralysis

Major virulence factor - toxin

most potent toxin known in nature, with estimated lethal dose less than 1 mg

AB subunit exotoxins