Respiratory Infections in Cattle and Sheep Flashcards
Which two cattle viruses belong in the family paramyxoviridae?
- Bovine respiratory syncytial virus
- Parainfluenza virus 3
Bovine viral Diarrhoea belongs to which family?
Flaviviridae
Which 4 viruses make up the bovine respiratory disease complex?
- Bovine respiratory syncytial virus
- Parainfluenza virus 3
- Bovine herpes virus 1
- Bovine viral diarrhoea
What are virulence factors?
The components of the virus that allow it to attach to and invade host cells, i.e. they are molecules produced by the virus that allow the pathogen to cause disease
What are the 2 main virulence factors for bovine respiratory syncytial virus?
G-protein
F-protein
What are the functions of the G and F proteins?
G-protein - allows attachment of the virion to the host cell membrane
F-protein - facilitates fusion of the virion with the host cell membrane
Describe the disease caused by bovine respiratory syncytial virus
- Interstitial pneumonia (inflammation of the tissues supporting the lung)
- Interstitial emphysema
- Secondary bacterial bronchopneumonia
How does bovine respiratory syncytial virus predispose to secondary bacterial bronchopneumonia?
- Formation of multinucleated giant cells
- These contain eosinophilic inclusion bodies
- Causes obstruction of airways and impairs lung clearance mechanisms
- > predisposing to secondary bacterial bronchopneumonia
What is a giant cell and what does it indicate?
A fusion of macrophages
Indicated chronic inflammation
How does bovine respiratory syncytial virus appear grossly?
Filled sacs on the lung surface which would pop if touched caused by coalescence of alveoli (Alveoli septae thickened by lymphocytes and mononuclear cells)
What are inclusion bodies?
Aggregates of viral capsid proteins
How does bovine parainfluenza virus type 3 affect the airways?
- Bronchitis
- Bronchiolitis
- Intracytoplasmic inclusion bodies in lungs days 5-7
- Hyperplasia= proliferation in numbers of alveolar cells (clogging of airways)
Describe how the virus of Bovine Rhinotracheitis BHV-1 infects the body and causes disease?
- The virus remains latent in sciatic and trigeminal nerves
- Once an animal is infected, it’s infected for life
- Initial response to infection is always by cell mediated immunity
- In times of stress, when immunosuppression occurs, you get recrudescence of disease, even in adult cattle
What is the source of infection of Bovine Rhinotracheitis BHV-1 ?
Periodic shedding of persistently infected animals
Cattle of which age are most susceptible to Bovine Rhinotracheitis BHV-1 ?
6-18 months old
Describe the pathology of Bovine Rhinotracheitis BHV-1
- Sloughing of epithelial cells in the Upper Resp Tract
- Necrosis leaves animal open to bacterial infection
What are the outcomes of bovine viral diarrhoea infection in each pregnancy trimester?
1st = reproductive losses 2nd = production of a persistently infected calf 3rd = foetus can fight off the virus
How does bovine viral diarrhoea attack the body?
- Destroys alveolar macrophages
- Depletes lymphoid tissue
- Can increase the prevalence or severity of bovine respiratory disease
What are the 2 predilection sites for bovine viral diarrhoea?
palatine tonsil and the nasal mucosa
Once bovine viral diarrhoea virus has spread in the blood, which tissues does it have a preference for, where it can be found in its highest concentrations?
Preference for lymphoid tissue, reaching its highest concentrations in the tonsil, thymus and ileum
Which disease occurs as a manifestation of BVD?
Mucosal disease
Which 2 sheep viruses are associated with respiratory disease?
- Ovine pulmonary adenocarcinoma
- Maedi
Which cells are targeted by Ovine pulmonary adenocarcinoma?
Type II pneumocytes
What is the diagnostic test for Ovine pulmonary adenocarcinoma?
The “wheelbarrow test” i.e. lift the sheep by its back legs like a wheelbarrow, and the fluid, which is produced from the tumour cells, comes out
Which cells are targeted by maedi virus?
Monocytes
How is Maedi virus transmitted?
By infected colostrum and milk as well as the respiratory route
‘Shipping fever’ is caused by which bacteria?
Mannheimia haemolytica
Mannheimia haemolytica occurs secondarily to?
Infectious bovine Rhinotracheitis (BHV-1)
How does Mannheimia haemolytica affect the lung?
- Haemorrhage is a classic feature
- Thrombosis, necrosis, inflammatory cell infiltration in Mannheimia haemolytica pneumonia
If Histophilus somni is found in the body, where is it commensal and where is it pathogenic?
Commensal in the genital tract and pathogenic in the respiratory tract
What are the effects of Histophilus somni in the body?
- Thrombus formation
- Vasoconstriction and increased epithelial permeability due to histamine release
- Systemic spread
What are the 4 main consequences of systemic spread of Histophilus somni?
Pleuritis
Pericarditis
Myocardial abscesses
Joint inflammation
Which 2 cattle bacterial are normal commensals of the URT but not the LRT?
Mannheimia haemolytica and Pasteurella
Why is used to treat mycoplasma and why?
- No cell wall
- Cannot be treated with penicillins or other beta-lactam antibiotics that target cell wall synthesis
- Use oxytetracycline or macrolides
How can animals become infected with mycoplasma?
Via the respiratory tract, the teat canal or genital tract
Artificial insemination with infected semen is another common route
What are the 4 clinical signs/conditions caused by Mycoplsma?
- Cuffing pneumonia
- Septic arthritis
- Otitis media
- Mastitis
What is cuffing pneumonia?
Peribronchial thickening or bronchial wall thickening
- A radiologic sign which occurs when excess fluid or mucus build-up in the small airway passages of the lung causes localized patches of atelectasis (lung collapse).
Describe how Mycoplasma bovis infects the body
- Found in URT and LRT
- Can survive in epithelial and inflammatory cells
- Infected cattle shed the mycoplasma via the respiratory tract for many months and even years acting as reservoirs of infection
How does spread of respiratory viruses occur? What can make them spread at a faster rate?
Close contact
Carriers- age mixing
Poor ventilation
Poor immunity
How can spread of disease be prevented?
Hygiene Stocking densities Correct air flow Dry environment Vaccination (where possible)