Lecture 11: Bovine Viruses 2 Flashcards
What is bovine respiratory disease complex? What animals are affected? Why is it important?
- Multifactorial
- 1st 40 days on feed – associated with winter (but summer pneumonia too)
- Most important cause of economic loss
- Metaphylactic antimicrobials = antimicrobial resistance issues
What are the viral agents that can cause BRDC
- Many bacterial and viral causes
o Viruses: BHV1, PI3, PRSV, BVDV
What s the taxonomy of bovine respiratory syncytial virus
Bovine Respiratory Syncytial Virus (BRSV)
* Family: Paramyxoviridae
* Subfamily: Pneumovirinae
* Genera: Pneumovirus
What are the clinical signs of bovine syncytial virus? what does it depend on?
- Clinically: severe dyspnea, excessive foam/mucus obstructing trachea
o 2-3% to 20% mortality
o Depend on age, immune status/immunosuppression, presence of Ig, route/dose of virus/strain virulence
o High fever (>40C), depression, anorexia, increased respiratory rate (hypersalivation/orthopnia/grunting)/ cough
o Mucopurulent nasal discharge/pulmonary emphysema/edema = crackles and wheezes
o Interstitial pneumonia
Who/when does BRSV affect?
- Target: cattle
o Seasonality: fall/winter
o More pathogenic in young calves (neonates less susceptible)
How is BRSV transmitted?
- Transmit: direct contact, aerosol, humans as a passive vector
o 70% calves infected <1yo
o Excrete in nasal discharge
o Not persistent infection – re-infection is common
What is the prevalence of BRSV in beef and dairy populations
- Very common: 60% of epizootic respiratory disease – dairy (70% in beef)
What s the pathogenesis of BRSV
- Path: polynucleated cell (syncytium) form – pathogenesis related to host response/immune
o No cytopathology = minimal viral caused damage
o Enter respiratory tract and migrate through mucus – invade via sialic acid residue epithelial cells and replicate
o Host immune system causes damage – upregulate pro-inflam/mast cell degeneration
What is a concern with the BRSV vaccine
- Vaccine can induce disease (modern vaccines are better and this is less of a risk)
What is BPI3
Bovine Parainfluenza 3 Virus (BPI3)
How is BPI3 transmitted? How prevalent is it?
- Transmit: same as BRSV: direct contact, aerosol, humans as a passive vector
o 70% calves infected <1yo
o Excrete in nasal discharge
o Not persistent infection – re-infection is common
What is the pathogenesis for BPI3
- Path: same as BRSV
o Enter respiratory tract and migrate through mucus – invade via sialic acid residue epithelial cells and replicate
o Will replicate well. In pulmonary alveolar macrophages = immunosuppression
o Host immune system causes damage – upregulate pro-inflam/mast cell degeneration
What ar the clinical consequences of BPI3
- Clinically: severe dyspnea, excessive foam/mucus obstructing trachea
o Depend on age, immune status/immunosuppression, presence of Ig, route/dose of virus/strain virulence
o High fever (>40C), depression, anorexia, increased respiratory rate (hypersalivation/orthopnia/grunting)/ cough
o Mucopurulent nasal discharge/pulmonary emphysema/edema = crackles and wheezes
o Less severe than BRSV
What is BHV1
Bovine Herpesvirus 1 (BHV1/IBR)
What type of virus is BHV1
- Large dsDNA
o Environmentally resistant – better at survival in cold temp - 3 types of BHV: type 1 is main in NA
What animals does BHV1 target? and how is it transmitted?
- Transmit: cattle and buffalo
o Nose to nose contact, aerosol (short distance)
o Excreted in nasal fluid or semen
o Incubation: 2-6d
What are the general clinical signs of BHV1 infection
o Infectious bovine rhinotracheitis: serous rhinitis + hyperemia/edema
Tracheal lesions + purulent inflammation and ulceration
Secondary infection common – resulting pneumonia
o Conjunctivitis
o Infectious pustular vulvovaginitis or balanopostitis
o Abortion
o High fever
o Anorexia/cough/hypersalivation/nasal discharge/inflamed nares/dyspnea
o BHV1.1 (main): respiratory tract infection and abortion
What are the 3 main types of BHV in NA? What are the general clinical signs associated with each type?
o BHV1.1 (main): respiratory tract infection and abortion
o BHV1.2a: respiratory and infectious pustular vulvovaginitis or balanopostitis and abortion
o BHV1.2b: respiratory and infectious pustular vulvovaginitis or balanopostitis
What is the prognosis of BHV1
- Prognosis: w/o pneumonia = recover in 4-5d
o 10% mortality and 100% morbidity
What is the pathogenesis of BHV1
- Pathogenesis: enter epithelial cells/nerves of upper airway > lysis of infected cells
o Lysis of ciliate epithelium in trachea (mucociliary elevator impair)
o Immunosuppressive: kill CD4 cells, reduce MHC1 and 2 expression, down regulate type 1 IFN
How to control and prevent BHV1
- Control: modified live or killed vaccine (intranasal – always modified live)
o Prevent calving in early spring – but unable to vaccinate when they go to market because they are too young (maternal Ig interference)
o Marker vaccines
Can BHV1 be eradicated? If so how?
o Not very effective – Ro is >1 meaning the virus is able to transmit between individuals
Transmission is lower in vaccinated herds
Prevent mixing of vaccinated and unvaccinated herds – this is a mechanism to eradicate BHV (drive Ro to <1 of transmission between herds – not necessarily within herd)
What is a concern when using BHV1 vaccines
o Vaccine manufacturing uses fetal bovine serum – if serum contaminated = can infect cows with live BHV
What are the 2 types of herpes viruses that can affect cattle
Bovine Herpesvirus 1 (BHV1/IBR)
Ovine Herpesvirus 2
How is ovine herpes virus 2 transmitted
- Transmit: from sheep/wildebeest to cow (not between cattle)
How does ovine herpes virus 2 clinically present
- Clinically: malignant catarrhal fever
o High fever (~41)
o Catarrhal inflame: erosion/mucopurulent exudation – upper resp/eyes/oral mucosa
Eye: panopthalmitis, hypopyon, corneal opacity/keratitis
o Swollen lymph nodes
o Lameness
o CNS: depression/trembling/hyporersponsiveness/sstuporr/sggressive/convulsion
o 100% mortality
What are the primary diagnostics used to diagnose BRD
- Respiratory panel: culture/PCR (look for BRSV/PI3/IBIR/M. bovis)
What are the 2 common causative agents of scours
- Agents: Bovine coronavirus
o Bovine rotavirus (similar to porcine rotavirus)
What is the pathology of bovine coronavirus
- Agents: Bovine coronavirus
Path: replicate in respiratory or GI tract
Many types all from bats
acts similarly to the porcine coronavirus
What is the taxonomy of bovine rotavirus
o Bovine rotavirus (similar to porcine rotavirus)
Genus: rotavirus, Family: Reoviridae
dsRNA, segmented, non-enveloped + multi-layer capsid
What is the pathogenesis of bovine rotavirus
pathogenicity factors in genome can be important
* replicate in epithelial cytoplasm
* due to viral enterotoxin NSP4 = destroy mature enterocytes
What are the features of the virus: bovine rotavirus
dsRNA, segmented, non-enveloped + multi-layer capsid
tons of serotypes = not feasible to make vaccines
What is the clinical presentation of bovine rotavirus
Clinically: lots of diarrhea in calf (1-2wk old)
* Maldigested/malabsorptive diarrhea = rapid dehydration
What is the transmission of bovine rotavirus like
1-2d incubation
5-7d of high viral shedding
What 3 other pathogens can cause scours (not bovine coronavirus or rotavirus)
o Also E. coli, salmonella, coccidia
