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Animal Health Major Infection Diseases of Cattle
major infectious diseases of cattle
54
Agriculture
Undergraduate 4
10/21/2014

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Term
What are the biotypes of BVDV?
Definition
Cytopathic (CV) strains kill cells in culture

Noncyotpathic (NCV) do not. These are associated with PI animals
Term
What is a PI infection with BVDV?
Definition
A persistently infected calf due to being exposed as a fetus during the first 125 days of gestation

-virus is not recognized as non-self by the immune system
-will shed the virus their entire life
-will often die before adulthood
Term
How is BVDV transmitted?
Definition
-direct contact with the shedder
-shed in saliva, mucus, semen, manure
-can also be transmitted in utero (PI calfs!)
Term
Which genotype of BVDV is more acute & more easily shed?
Definition
Type II
Term
Describe the characteristics of a BVDV infection
Definition
-virus replicates in upper resp tract & lymphoid tissues
-destroys lymphoid tissues = immune suppression
-virus in blood stream 3-10 days after infection
-may be as short as 2-3 days for some cattle
-70-90% are subclinical
Term
What are some of the risk factors for BVD disease?
Definition
Poor herd immunization
-no modified live virus used, or didn't give primary killed vaccine

Animals are purchased
-without screening for BVD
-no quarantine period
Term
What are the clinical presentations of BVDV?
Definition
Mucusal disease (only in PIs)
Peracute BVD
Acute BVD
Immune suppression & secondary pneumonia
Reproduction problems, abortion, congenital anomalies
Term
What is the difference between peracute and acute BVD?
Definition
Peracute
-high fever, off feed, diarrhea, death

Acute
-fever, diarrhea, pneumonia, abortion
Term
Describe the incidence & effects of mucosal disease
Definition
-in PI animals
-low morbidity, 100% fatality
-fever
-oral erosions
-diarrhea, sometimes bloody
-death in 5-7 days
Term
What happens if a PI animal is exposed to a CV strain of BVDV?
Definition
they will die
Term
Describe the patterns you would see in a herd following introduction of the BVDV virus
Definition
1. Acute disease in susceptible animals
2. Abortions & early embryonic death
3. Weak or deformed calves
4. PI animals
5. Death of more animals
Term
Describe the reproductive manifestations of BVDV if a cow is exposed at:

Breeding - 42 days gestation
70-125 days gestation
100-170d gestation
170-280d gestation
Definition
At breeding: inhibited conception or EED
70-125d: PI calves
100-170d: congenital anomalies or abortion
170-280d: no fetal harm, will be born with antibodies to the disease
Term
Describe some of the congenital anomalies seen in calves exposed to BVDV in-utero
Definition
cerebellar hypoplasia (inhibited motor control)
blind or cataracts
lack of hair
Term
True or False
A PI dam is not necessarily going to give birth to a PI calf
Definition
false

Will always give birth to a PI calf
Term
Describe the economic costs of BVDV
Definition
-very few infections are clinical
-acute disease of a pathogenic strain can kill 25-40% of infected animals
-severe milk reduction
-weight loss
-abortions
-persistent reproductive problems in the herd
Term
What is the recommended treatment for BVDV?
Definition
-no specific treatment
-supportive care & antibiotics for secondary infections resulting from acute BVD
-PI calves will generally die, should be euthanized to prevent spreading and end suffering
Term
What are some critical management considerations to prevent or eliminate PI animals & prevent acute disease?
Definition
-effective vaccination program
-MLV to protect fetuses
-quarantine new animals & test for PI
-vaccinate new purchases while in quarantine
-isolate animals with diarrhea & respiratory disease
Term
True or False

Salmonellosis is a host-adapted virus
Definition
False

Host-adapted and non-host adapted strains exist

More serious effects will be seen if a non-adapted strain infects a host
Term
Describe the pathology & clinical signs of Johnes disease
Definition
Pathology
-slow growing bacteria mainly in ileum
-intestines thick with bacteria & inflammatory cells
-malabsorptive diarrhea

Clinical Signs
-profuse diarrhea
-good apetite yet weight loss
-no fever
-reduced milk production in sub-clinical cases
Term
What is the best course of treatment for Johnes disease?
Definition
-no effective treatment
-selective slaughter of affected animals
-blood & milk tests, fecal cultures
Term
What are the clinical signs of salmonellosis?
Definition
-bloody diarrhea with fibrin
-fever
-off feed
-reduced milk production
-abortions
-calf septicemia, can be fatal
Term
How is salmonellosis transmitted?
Definition
Primarily through feces, but also oral/nasal/urine shedding in septicemic cases
Term
What does it mean that salmonellosis is an opportunist disease?
Definition
A low dose of exposure will affect cows with suppressed immune systems, e.g. post-partum, and calves

Healthy cows need a higher dose of exposure to be affected
Term
What are the critical control points for salmonellosis?
Definition
-restrict movement of manure between herds
-separate hospital & calving pens
-rational antibiotic use so you are not killing 'good' bacteria
-separate calves & cows in outbreaks
-cannot vaccinate for salmonellosis!
Term
How is Johnes disease transmitted?
Definition
fecal-oral
(shed in manure, ingested through contaminated feed, pasture, water etc)

-can be transmitted from dam to fetus in advanced stages
Term
Why is prevention/control of Johnes disease a challenge?
Definition
Seems to only affect calves if exposed at less than 6 months of age
-Clinical manifestation of the disease will happen years later, 2-6 yrs of age
Term
True or False

Bacteria of Johnes disease can survive years on pasture
Definition
true
Term
What are the critical control points for managing Johnes disease?
Definition
-prevent manure movement from adults to calves
-ID and quickly remove infected individuals
-clean maternity pens & immediately remove calf
-do not pool colostrum together
-don't feed leftover feed to heifers
-avoid spreading manure in same year as forage
Term
What are the chief stages/goals in biosecurity programs?
Definition
1. Prevent introduction of pathogens to farm
2. Prevent movement of pathogens within the farm
3. Prevent transfer of pathogens to humans
Term
Name some items on the 'A' list of biosecurity
Definition
-effective vaccination programs
-hygienic milking
-restrict manure movement
-isolate sick animals
-separate sick & maternity pens
-no colostrum pooling
-remove deadstock, culled cows
-disease monitoring programs
Term
Name some items on the 'B' list of biosecurity
Definition
-selective sourcing of purchases
-maximize knowledge of source
-test animals before introduction
-use milk replacer, not pooled colostrum
-metaphylactic treatments
Term
Describe the structure of placentation in ruminants
Definition
Caruncle - maternal side of placenta
Cotyledon - fetal side of placenta
Placentome - Caruncle + Cotyledon
Term
What is a freemartin?
Definition
A heifer born co-twin to a male, with genotype XX/XY

-androgenous female sex characteristics, abnormal external & internal genitalia
-95% are sterile

e.g. may have ovaries & a vagina but no cervix or uterus
Term
What is abortion? What might cause this?
Definition
premature expulsion of embryo or non-viable fetus from the uterus

-impaired function of the placenta
-infectious or non-infectious damage to fetus
Term
What are some causes of non-infectious abortion?
Definition
-twins
-heat stress
-fatal genetic anomalies
-maternal disease e.g. mastitis
-infectious contributors e.g. BVD, leptospirosis
Term
What is infectious sporadic abortion?
Definition
-introduction of disease agent through circulation or up repro tract

-can be fungal or opportunistic bacteria
-not a huge risk to rest of herd as not highly contagious
Term
What are some contagious agents that cause cause abortions?
Definition
Leptispirosus
Infectious Bovine Rhinotracheitis
Bovine Virus Diarheea
Term
What is neospora caninum? What does it cause?
Definition
-coccidian parasite which infects cattle & dogs
-lifelong infection
-manifests itself as abortion
-if fetus is not aborted,the calf is very likely infected
-no effective treatment
Term
What is horizontal vs vertical transmission of Neospora caninum?
Definition
Horizontal: from dog to cattle through do feces, or cattle to dog through cattle tissue
Vertial: from cow to fetus
Term
What should you do manage Neospora caninum in a herd?
Definition
-cull cows which have aborted due to neospora
-do not breed seropositive cows to replace heifers
-could do ET a seronegative recipient of an infected cow has desirable genetics
Term
Describe Stage I of parturition
Definition
-relaxation of pelvic ligaments & cervix
-fetus changes position
-rhythmic contractions push placental mmb against cervix
-can take 2-3 days
Term
Describe Stage II of parturition
Definition
-rupturing of allantois & amniotic sac
-abdominal & uterine contractions expel fetus from uterus
-2 to 4 hours to complete
Term
Describe Stage III of parturition
Definition
-expulsion of fetal membranes (<12hours)
-uterine involution (<28 days)
Term
What are the 3 'P's of calving?
Definition
Presentation - head first!
Position - upside down vs right side up
Posture - how head & legs are
Term
What are some causes of dystocia?
Definition
-failure of cervix to dilate
-obstruction of vagina (too much pelvic fat)
-failure of vulva/vagina to dilate
-uterine torsion
-uterine inertia (exhaustion, milk fever)
-fetus is too large for pelvis
-abnormal presentation
-twins
-malformed fetus
Term
What are some things to consider when assisting in calving?
Definition
-maximum force to be used is 2 peoples arms
-keep things sanitary, use lube
-follow natural downward arc
-rotate calf during delivery
Term
What are some of the consequences of dystocia?
Definition
-death of fetus
-vaginal tears
-uterine tears
-obturator nerve paralysis (calving too tight)
-sciatic nerve paralysis (down too long)
-muscle damage due to being down
Term
What is the term for a difficult calving?
Definition
dystocia
Term
What is postpartum involution?
Definition
restoring the repro tract so it can support another pregnancy
-shrinkage & repair of uterus and cervix
-sloughing of caruncles, repairing endometrial epithelium
-clearing of bacterial contamination
Term
What is postpartum anestrus? How would you treat this?
Definition
-cows don't return to regular estrus cycle by 60d post-partum
-may be more pronounced in 1st lactation
-associated with body condition
-difficult to identify affected individuals
-supply progesterone to treat
Term
What are the risk factors for a retained placenta?
Definition
-dystocia
-twins
-abortion
-milk fever
-C section
-induced delivery
Term
What is the root cause of a retained placenta?
Definition
impaired immune function inhibiting detachment of the placentome

-neutrophils have reduced chemotaxis at calving, reduced killing capacity post-partum
Term
True or False

Uterine motility is reduced in cows affected by a retained placenta
Definition
False
Term
What are the impacts of a retained placenta?
Definition
RP itself is not directly harmful, but there is a greatly increased risk of metritis, endometritis
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