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Population Medicine
Midterm
76
Veterinary Medicine
Professional
10/28/2010

Additional Veterinary Medicine Flashcards

 


 

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Term
Definitive Host
Definition
Host where parasite reaches sexual maturity (patent infection)
Term
Intermediate Host
Definition
Host required for parasite maturation, does not reach sexual maturity here
Term
Paratenic Host
Definition
Host not required for parasite maturation, but may provide homeostasis and transport. (e.g., toxocara infection from ingested earthworms/insects)
Term
Direct Life Cycle
Definition
Life cycle where definitive host is infects another definitive host direcly. CAN use paratenic hosts, but not required. Fecal-oral transmission is one example.
Term
Indirect Life Cycle
Definition
Life cycle where parasite is required to pass through an intermediate host to become infective. Definitive host passes egg/larvae to intermediate host --> intermediate host infects another definitive host, where parasite matures.
Vector borne (malaria, HW) or by predator/prey cycle
Term
Fecal-oral Transmission
Definition
Eggs pass into into environment and are directly ingested by next definitive host. The parasite egg or oocyst must be able to survive environmental conditions - a paratenic host helps the parasite by providing homeostasis and transport.
Term
Toxocara canis Transmission
Definition
Transplacental AND transmammary
DIRECT w/ possible paratenic (earthworm, snails, rodents, birds)
Term
Toxocara canis Biology
Definition
98% of puppies infected by transplacental (after day 40) followed by transmammary
Eggs shed in feces 21 days -3m post partum, then decline
Female parasite produces >200,000 eggs/day, can survive in soil and remain viable >10 yrs
Larva develop inside egg and stay there for protection from environment
Term
Where can children be infected with Toxocara canis?
Definition
Kids get infected playing in soil, more likely in backyards than parks
Term
What complications does Toxocara canis produce in the human host?
Definition
VLM - nonspecific symptoms (fever, malaise, abdominal pain, leukocytosis and eosinophilia), about 1-5 y/o

OLM - hard to ignore (misdiagnosis common, treated as retrobulbar tumor), about 5-10 y/o. 2nd leading cause of blindness in children
Term
How to prevent VLM and OLM?
Definition
Deworm puppies at 2, 4, 6, 8 weeks, then start HWP at 10 weeks. Clean feces from YARDS, parks. Do fecals to verify treatments worked.
Term
Use of selamectin in preventing Toxocara canis
Definition
Parasite preventative useful in gestation - apply to dam at day 40 (before transplacental), apply again at day 10 postpartum to reduce transmammary
Term
Ascarids implicated in migrations
Definition
Toxocara canis
Toxocara cati (yards, sandboxes, counter tops)
Baylisascaris procyonis (raccoons, worse than T. canis, eosinophilic meningitis)
Term
Transmission of Hookworms
Definition
Transmammary
Direct - larvae in environment
Percutaneous - produce collagenase to digest skin
Term
Cutaneous Larva Migrans
Definition
In wrong, larva cannot digest collagen efficiently and wander - painful and irritating. People become infected from contaminated ground or walking barefoot
Term
What meats are associated with Trichinella spiralis?
Definition
Undercooked bear, pork.
Term
What is the life cycle of Trichinella spiralis?
Definition
1.) Carnivore ingests meat infected with larvae
2.) Larvae penetrate stomach lining and become adults
3.) Adults mate, females penetrate lining of small intestine and produce larvae (1,000/day for 40-60 days). Intestines act as DH.
4.) Larvae pass through lymphatics, into blood and distributed to musculature
5.) Paralysis develops, infected animal now eaten (IH)
Term
Principal muscles affected by Trichinella spiralis
Definition
This parasite affects the diaphragm, hypoglossal, and masseter muscles - predator becomes prey
Term
Toxplasmosis infection in cats
Definition
Majority <1 y/o
Majority do not shed oocysts again
FeLV/FIV do not affect shedding - immunosuppression leads to systemic manifestations
Term
Major sources of Toxo
Definition
Handling raw pork/lamb, tasting marinades, not washing cutting board, feral kittens, unpasteurized milk from actively infected goats
Term
Toxo recommendations to client
Definition
Don't adopt a kitten during pregnancy or chemo
Make cat indoors-only to reduce risk of infection through predation
Don't feed raw scraps to cats
Pregnant women should not scoop litter
Titers on cats are useless - active infection already passed, usually +
FREEZE fresh meat > 48hr
Term
What is the seroprevalance of toxo in the U.S.
Definition
30-40% are seroprevalent for this parasite
Term
Tachyzoites & Bradyzoites
Definition
Stages of toxo in tissue (acute and chronic, respectively)
Term
Characteristics of Toxo Titer
Definition
Most cats + by 1 year old
IgM = recent infection
IgM/IgG = active
IgG = past infection or systemic disease
Term
In NORMAL humans and animals, what do giardia and Crypto usually cause?
Definition
These parasites usually cause self-limiting diarrhea in normal hosts
Term
Characteristics of Giardia and Crypto
Definition
Infected host can shed 10^6 organisms/gram feces
Infectious dose is very low
Cysts and oocysts resistant to normal municipal water filtration/sewage tx systems
Environmental contamination likely
Commonly affect livestock
Term
Giardia assemblages
Definition
A and B - potentially zoonotic
C and D - Canid only
E - Hoofstock
F and G - cats, rats
Term
Crypto Genotypes
Definition
Genotype I - C. hominis
Genotyple II - C. parvum, ZOONOTIC
Term
What is a major public health concern with Giardia and Crypto?
Definition
Water-borne outbreaks (water systems, pools) are a major concern with these parasites
Term
Tapeworm Life Cycle
Definition
Indirect life cycle
An IH is consumed to transmit parasite to DH (dog, cat)
In some cases, parasite debilitates IH to increase likelihood of consumption by DH
Term
How does the tapeworm develop in the IH
Definition
IH ingests egg -> hatch -> larvae migrate to vital location and form Cysticercus (cysticercoid in arthropod) -> cysticercus enlarges, fills with fluid as space occupying lesion -> IH consumed, develops into adult in DH
Term
What are the parts of a tapeworm?
Definition
Scolex - head (1 per cysticercus)
Strobila - body or bladder. Elongates into proglottids
Term
What is Taenia saginata?
Definition
Humans are DH, cattle are IH, infected by proglottids in feed. Cysticercus in cattle muscle (beef measles), transmitted to human by undercooked/raw beef.
Term
What is Taenia solium?
Definition
Humans are DH, pigs are IH, infected by proglottids. Humans eat undercooked pork and ingest muscle cysts. If humans consume only eggs, they are the IH.
Term
What is neural cysticercosis?
Definition
Occurs in humans that act as IH for Taenia solium. Cysts in many sites - brain and eye. Leading cause of adult-onset epilepsy in Mexico. Widespread in tropics, now in US through immigration
Term
Echinococcus Life Cycle
Definition
Carnivore DH passes egg in feces, no proglottids seen -> herbivore/human IH becomes infected and Hydatid cysts (many scolices) in liver and lungs enlarge to incapacitate the IH slowly
Term
Where is Echinococcus widespread and what host is blamed?
Definition
In the Middle East, S America, Asia, and Africa, the dog is noted for this zoonotic parasite. Religious taboos against contact with dogs probably stem from this parasite.
Term
Humans serve as DH for which tapeworms? As IH?
Definition
DH for Taenia saginata, Taenia solium
IH for Echinococcusm, Taenia solium
Term
Would it be better to be a DH or IH for a tapeworm?
Definition
It would be better for the host to be a DH for this parasite, as IH are usually progressively debilitated to the point of death
Term
What is the difference between a zoonotic disease and vector-borne disease?
Definition
Zoonotic diseases are transmissible between different VERTEBRATES

Vector-borne diseases are spread by invertebrates, and may affect multiple species. Can be zoonotic (plague) or non-zoonotic (malaria - man is the only reservoir)
Term
What is a reservoir?
Definition
Other vertebrates
Passively harbor arthropod-borne disease, must develop high enough blood levels to infect arthropod.

Don't usually die from disease, become sub-clinical carriers
Term
What is a dead-end host?
Definition
Infected host does not develop sufficient pathogen levels to infect arthropod
Ex: white-tail deer carry Lyme but do not infect ticks
Term
What are the 4 genera of Ixodid ticks in North America?
Definition
Dermacentor (American Brown Dog), Amblyoma, Rhicephalus, Ixodes
Term
Tick Life Cycle
Definition
Adult F lays 5,000 eggs then dies
Eggs hatch into larva, feed on blood-meal (nestling birds, often) and molt into nymphs
Nymphs feed on blood-meal, molt into adults
Adults feed on larger mammals or birds
Term
What is the significance of ticks feeding on neonates?
Definition
Exposure to a pathogen during immunological development can induce a state of tolerance in neonates whereas exposure of a naive adult would likely kill it. Neonates survive and perpetuate infection.
Term
Transmission of disease in the arthropod
Definition
Transovarian transmission from adult female to eggs
Transtadial - larval stage becomes infected and remains infected through maturation
Term
RMSF epidemiology
Definition
Causative agent: Rickettsia rickettsii
Dermacentor (American Brown Dog tick) are vectors, infected through transtradial AND transovarian
Rodents are reservoirs
Term
RMSF in humans and dogs
Definition
Humans - acute vasculitis, pettechia, bleeding in many organs (CNS, kidneys), 2-10% mortality
Canine: Vasculitis, hemorrhage, shock, end-arterial organs most affected
Term
Life Cycle of Ixodes (deer tick)
Definition
Adult females preferentially feed on WTD (lay more eggs)
Reservoir is white-footed mouse - transtadial, no transovarian. Larvae feed on neonates
Neonatal white-footed mice infected by nymphal stages
Term
What three organisms must be present for Lyme disease to spread? What can be done to decrease prevalence?
Definition
Ixodes ticks, WTD, white-footed mice. Rodent control is necessary but not always practical (no reservoir = no disease)
Term
Factors affecting tick-borne illnesses
Definition
-Seasonal and annual variations
-Reservoir capable of transmitting agent
-Environmental factors conducive to reservoir populations
Term
How prevalent is Yersinia pestis today?
Definition
10-20 human cases in US/year
1,000 - 3,000 humans cases worldwide/year - vastly under-reported
Term
Characteristics of Yersinia pestis
Definition
-Facultative anaerobic, intracellular, gramNEG bacillus
-Easy to culture, but survives poorly in environment
-Primarily rodent pathogen - rats, squirrels, prairie dogs
-Kills most rodents it infects, some become carriers
Term
What is the primary vector of Yersinia pestis?
Definition
Xenopsylla cheopis (oriental rat flea)
Term
Transmission of Yersinia pestis
Definition
Flea bites infected rodent -> bacillus grows in esophagus/foregut of flea, blocking swallowing -> flea bites again and expels bacteria into new host
Term
Three routes of human exposure to Yersinia pestis
Definition
1.) Flea-borne, from infected rodents
2.) Direct contact with infected tissues or fluids of sick animals
3.) Air-borne by resp droplets from cats and humans with pneumonic plague
Term
What rodent is responsible for the most cases of human plague? What carnivore?
Definition
When humans are infected, rock squirrels are the most likely rodent source. Cats are the most likely carnivore source.
Term
Three forms of human plaque
Definition
Bubonic - LN are primary site
Septicemic - bacillus has traveled throughout body from bite or LN
Pneumonic - primary site is the lungs
Term
What form of plague do cats spread?
Definition
Cats spread the pneumonic form - nearly all human pneumonic cases have results from contact with cats. Mortality in both is >50%.
Term
Efforts to control plague
Definition
-Rodent and flea control in environment, flea treatment for dogs and cats.
-Abx if exposed
-No approved vaccine
-No forseeable eradication due to wildlife and flea population
Term
Category A agents
Definition
This category includes plague, anthrax
Term
Bartonella henselae
Definition
Causative agent of Cat Scratch Dz
GramNEG, pleomorphic bacteria
Very slow growing
Sensitive to abx
Term
Epidemiology of Bartonella hensalae in cats
Definition
Cats are main reservoir
Documented in 25-49% of healthy cats
In cats, self-limiting febrile illness of 48 to 72 hours. Produces a chronic, asymptomatic bacteremia for 2m - several years (older cats affected longer than younger)
Transmitted through cat flea, NOT cat-cat or to kittens. (exception: blood transfusion)
Term
Bartonella henselae in other hosts
Definition
Human infection following cat bite/scratch (also, potentially through fleas and Ixodes and Dermacentor)
Immunocompromised dogs may be at risk from Ixodes and Dermacentor
Term
Cat Scratch Disease in humans
Definition
22,000 cases/yr, 2,000 hospital admissions
90% have exposure to cat (other: squirrels, dogs, goats, barbed wire), usually a bite/scratch to head/neck/upper limb
Usually <21 y/o, Sep-March
Usually self-limiting and benign - regional lymphadenopathy, spontaneously resolves in 2-5 m.
Complications possible in immunosuppressed
Term
What disease is associated with Parinaud Ocular Glandular Syndrome?
Definition
Cat Scratch Disease is associated with this ocular condition in humans
Term
Prevention of Cat Scratch Disease
Definition
1. CONTROL FLEAS
2. Sero-neg cats better for immunocompromised people (e.g., avoid young cats from shelters, etc)
3. Abx tx of bacteremic cats may or may not clear cat of infection
Term
What is the etiological agent of Murine Typhus?
Definition
Rickettsia typhi causes this illness and is endemic to all continents except Antarctica. It is a gramNEG obligate intracellular bacterium, survives well in environment
Term
Epidemiology of Murine Typhus (Rickettsia typhi)
Definition
Rats are primary host and reservoir - asymptomatic infection.
Vector is primarily Xenopsylla cheopis, infected when feeding on rat -> organism multiplies in mid-gut, infecting flea for life and causing no damage -> shed in flea feces -> rats inhale feces and amplify
Term
Transmission of Murine Typhus to human
Definition
Man is accidental host, scratching contaminated flea feces into skin. Incubated 1-2w. Also, by cat/mouse flea and direct bite by flea infected >3w. Usually occurs late spring-fall, southern states, in areas with large rat populations. Fever, malaise, headache, joint pain. Tetra/doxycycline.
Term
What are the two types of mosquitoes infected with WNV and what do they feed on?
Definition
Culex - bird feeders
Aedes - mammal feeders
Term
Clinical signs of WNV in the horse
Definition
Acute
93.9% ataxia, usually symmetric
43% CN signs
54% muscle fasciculations
32% fever
Term
Diseases that can resemble WNV
Definition
Rabies (but ascending paralysis)
Botulism (severe muscle shaking)
EPM (asymmetric incoordination)
Term
Vaccine recommendations for WNV
Definition
Regional decision
Horses should receive 2 initial doses 3-6 w apart, before start of mosquito season
Additional booster in July/August if highly stressed
Term
WNV treatment
Definition
Mostly supportive
Anti-inflammatory meds
Mannitol to reduce CNS edema
Antioxidants (Vit E)
IV/parenteral nutrition
Slings/feeding tubes may be necessary
Term
Diagnosis of WNV
Definition
CBC/chem WNL
CSF - mononuclear pleocytosis or high TP
Plaque reduction neutralization test is gold standard, but most labs use antigen-capture ELISA for IgM - detected 8-10 days post infection for up to 2m. Virus isolated in whole blood, serum, CSF, CNS
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