Food Animal Respiratory Disease, Pt. 2 Flashcards
(39 cards)
What can all viral infections predispose cattle to?
Bovine Respiratory Disease Complex (BRDC)
- shipping fever - feedlot calves
- enzootic pneumonia - diary and veal calves
What are the 4 most common viruses and bacteria associated with BRDC?
VIRUSES - BVD, IBR, BRSV, PI3
BACTERIAL - Mannheimia hemolytica, Pasteurella multocida, Mycoplasma, Histophilus somni
What predisposes to BRDC?
STRESS and viral disease
- shipping
- comingling at sale barns
- heat
- poor nutrition
- weaning
What treatment is recommended for BRDC? How is it controlled? What is prognosis like?
antibitoics and Flunixin meglumine
vaccines, control stress and viral infections
good
What causes infectious bovine rhinotracheitis? How is it transmitted?
bovine herpesvirus-1
- oronasal secretions of infected
- reactivation from trigeminal ganglia in clinically recovered cattle with immunocompromization
What are some hosts of infectious bovine rhinotracheitis?
- cattle
- buffalos
- small ruminants
- wild ruminants
What is the characteristic sign of infectious bovine rhinotracheitis? What else is seen?
red nose - rhinitis causes hyperemia and ulceration of the mucosa
- bilateral conjunctivitis +/- corneal opacity without ulcers
- fever >104 F
- abortion - BHV-1.2
- pustular vulvovaginitis - BHV-1.2
- encephalitis - BHV-1.3 or BHV-5
What are the 2 forms of transmission of infectious bovine rhinotracheitis? What are 2 risk factors?
- RESPIRATORY - droplets, nasal secretions
- GENITAL - semen, genital fluid, fetal fluid, venereal
- ALL ages and breeds are susceptible, but most common in those above 6 months of age
- unvaccinated herds - breeding cattle are highly susceptible to epidemics of respiratory disease and abortion
What are the 5 clinical forms of infectious bovine rhinotracheitis?
- respiratory - rhinitis (red nose)
- ocular
- abortive (IPV)
- systemic disease - newborn calves
- encephalitic
What necropsy lesions are associated with infectious bovine rhinotracheitis? What are 2 methods of diagnosis?
reddened, congested tracheal mucosa with secondary bacterial infections
- virus isolation from nasal or ocular swabs
- serology - paired samples ONLY with a 4 fold rise in the 2nd sample taken 2-3 weeks later
What cattle are most commonly affected by bovine respiratory syncytial virus? How is it spread?
feeder age dairy and beef calves and naive adults –> fatalities associated
oronasal secretions
What is the pathophysiology of bovine respiratory syncytial virus? What does it have a predilection for?
CYTOPATHIC
- forms syncytial cells in infected tissues, causing the formation of multinuclear cell fusion
- induced cytokine production by cellular immunity
lower respiratory tract
What are some signs of bovine respiratory syncytial virus? What are 2 unique signs?
- depressed, off feed
- cough, severe dyspnea
- high fever >104
lung and SQ emphysema
What are 3 signs of bovine respiratory syncytial virus on necropsy?
- lungs fail to collapse when thorax is opened
- pulmonary edema and interstitial pneumonia
- emphysema
How is bovine respiratory syncytial virus diagnosed? Treated?
- clinical signs and necropsy lesions
- virus isolation - difficult
- serology
NSAIDs +/- corticosteroids
What causes bovine viral diarrhea? What are the 3 ways it is classified?
Flaviviridae, Pestivirus (RNA)
- BIOTYPE - way it behaves in culture (cytopathic vs. non-cytopathic –> both capable of causing disease!)
- GENOTYPE - Type 1a, 1b, 2a (2 is newer and associated with severe hemorrhagic syndrome)
- STRAIN - small genetic differences
What serves as the main reservoir for BVD? What are the 3 courses of disease?
persistently infected –> spread through infected body fluids
- acute infection - usually subclinical
- in-utero fetal infection
- persistent infection - mucosal disease
What clinical signs are associated with acute infection of BVD?
- anorexia, depression
- high fever
- oculonasal d/c
- salivation
- mucosal erosion
- diarrhea
- leukopenia, thrombocytopenia (Type II, older cattle)
- may have NO signs –> immunosuppression
(all post-natal infections are acute, most are subclinical)
How does fetal infection of BVD occur? What does outcome depend on?
dam is infected or viremic and virus infects fetus transplacentally –> fetal infection continues independent of maternal infection
stage of fetal development
- <150 days = death and abortion
- 100-150 days = congenital malformation
- 40-125 days = persistently infected calf
- >150 days = normal calf with acquired immunity to BVD, may be born weak
When does mucosal disease occur with BVD? How does this typically develop?
fetal infection with noncytopathic persistant virus only - calf’s body doesn’t recognize the virus as foreign (any calf born to a PI cow WILL BE PI)
calf may look normal at birth and secretes large amounts of virus throughout its life +/- chronic poor-doers
What are the 4 possible outcomes of a PI animal infected with BVD?
What are 3 necropsy lesions seen with BVD?
- mucosal erosions seen in oral cavity, nose, esophagus, rumen, omasum, and abomasum
- necrosis of Peyer’s patches in the ileum
- erosions on coronary band and interdigital skin
What is the gold standard for diagnosing BVD? What are 2 other options?
viral isolation - blood antemortem, best for detecting acute infection
- serology - paired samples
- PI screening tests - Microplate VI, antigen-capture ELISA, PCR, IHC on skin samples (skin notch) - poor detection of acute infections
What treatment is recommended for mucosal disease with BVD? How is infection controlled?
euthanasia
- vaccination - does not completely protect fetus
- detection and removal of PI carriers
- biosecurity - isolation of new cattle for 3 weeks prior to comingling and testing prior to addition
