Food Animal Respiratory Disease, Pt. 2 Flashcards
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
What is the standard vaccine issues for BRDC?
4 way - BRV, BVD, PI3, BRSV
- often in combo with Leptospirosis
- injectable and nasal options
- modified live > killed - produced better cell-mediated immunity, killed required 2 doses spaced 2-3 weeks apart, killed is more $$$
What is the most economically significant disease of beef cattle?
BRDC - death, chronic infection, treatment cost, production loss
What cattle are most commonly affected by enzootic pneumonia? What is the most common cause of outbreaks?
housed dairy and veal calves 2-6 months old
Pasteurella multocida
What are the 3 steps of progression of shipping fever?
- stress impairs the immune system - commingling, poor weather, weaning, transport, overcrowding, poor nutrition, vaccination, castration
- primary viral respiratory infection
- further impairment of respiratory immunity due to destruction of cilia and alveolar macrophages
What are the 4 most common bacteria associated with shipping fever?
- Mannheimis hemolytica - most common, inhabitant of nasopharynx, virulence enhanced by bacterial leukotoxin
- Pasteurella multocida - common in outbreaks in dairy calves (enzootic pneumonia)
- Histophilus somni - sporadic in US
- Mycoplasma bovis
When are clinical signs of shipping fever seen? What signs are associated?
first 3 weeks after stress
- depression - drooped ears and head, weakness, will not move when approached
- anorexia - decreased rumen fill, sunken paralumbar fossa (dehydrated)
- nasal d/c, cough
- increased rectal temperature, RR (open mouth breathing common), respiratory sounds (wheezes, pleural friction rubs) cranioventrally
What is the characteristic necropsy lesion of shipping fever? What else is seen?
consolidation and dark discoloration of cranioventral lung lobes
- fibrinous pleuritis
- pulmonary abscesses with chronic cases
What are 3 options for treating shipping fever? What is not used?
- antibiotics - all labeled for bacterial pneumonia
- anti-inflammatories - Banamine (Flunixin meglumine)
- vitamin C, B
fluids
What are some good options for antibiotics for treating shipping fever? What is not commonly used?
- Ceftiofur - 3-4 day slaughter withdrawal
- OTC - 28 day withdrawal
- Tilmicosin (Micotil)
- Florfenicol
- Draxxin - also covers Mycoplasma
Baytril/Danofloxacin (A180) - not for use in cattle intended for dairy production or in calves to be processed for veal
What is metaphylaxis? What use does it have for shipping fever?
mass treatment of all animals in the hopes of preventing outbreaks
significantly decreases morbidity and case fatality + improve performance
- most beneficial when >40% of animals are anticipated to become ill
What ancillary treatment is done for BRDC?
- oral fluids
- isolate, space, shelter
- provide dry and warm environment
- plenty of palatable feed and water
- tripelennamine hydrochloride (Re-Covr)
How can stress be minimized to prevent BRDC? What biosecurity is recommended?
- work calves well in advance of weaning
- wean calves 4-6 weeks before marketing
quarantine 2-3 weeks and clean between
How are modified live vaccines handled? When are they not given?
- MLV loses viability a few hours after reconstitution
- disinfectant and soap residues left in equipment will kill MLV
pregnant cows - modified live IBR can cause temporary infertility due to follicular necrosis + minute chance for MLV to be contaminated with virulent viruses or to cause mucosal disease in PI animals
How does the nasal IBR and PI3 vaccines work?
virus cannot survive at normal body temperatures, but replicates in the upper airways, resulting in interferon production and increased secretory IgA at point of entry
- safe in pregnant cows and contact animals
What are bacterin vaccines for BRDC? What affect do they have?
M. hemolytica, P. multocida vaccines with a maximum response within 2-3 weeks following vaccination but wanes by 6 weeks
decreases morbidity
