Resp infections in cattle & sheep

What is being shown with these lungs?

Damage to cranio-ventral lung lobes —> enzootic pneumonia

• Lungs should be pink & float

• Lungs sink because collapsed

• Haemorrhagic w/ harder than normal areas

What structures are present on these lung lobes?

Nodules —> become chronic

What is being shown in this lung? What is the significance?

Microabscesses caused by mycoplasma → frothy exudate

cannot be penetrated by ABs because can hide intracellularly

What is being shown here? What is the significance?

Pleuritis / pleurisy—> infection & inflm of pleura

• Thickening of pleura

• Movement of lungs against thoracic wall impeded → more difficult to expand

  • held in place by thickened pleura —> should be thin & well lubricated to allow lung expansion

What viruses cause respiratory diseaes in cattle?

• Paramyoxviridae

  • Bovine respiratory syncytial virus

  • Parainflunza virus 3

    • ssRNA, enveloped

• Herpesviridae

  • Bovine herpesvirus 1 (IBR)

    • DNA virus

• Flaviviridae

  • Bovine Viral Diarrhoea Virus (BVD)

    • ssRNA enveloped

• Coronaviridae

  • Bovine coronavirus = new —> damages protective mucus in resp tract, intranasal vacc available

What are virulence factors?

Components of virus that allow it to attach & invade host cellls → cause dx

What are the features of the pathogenesis of paramyxoviridae?

• Proteins required for attachement to target cell

  • In RSV (pneumovirus) —> done by G protein.

  • In PI3 (paramyxovirus) —> done by HN glycoproteins (Haemagglutinin/Neuraminidase)

• Fusion proteins induce fusion between viral envelope & target cell membrane

• Virus nucleocapsids released into cytoplasm

What is a marker vaccine?

Vacc against dx made from modified pathogen (protein removed → vacc made of resultant pathogen) e.g. IgE deleted vacc

(esp. important for bovine herpes virus)

What is the subfamily and genus is bovine respiratory synctial virus in?

• Subfamily —> Pneumovirinae

• Genus —> Pneumovirus

What is the incubation, surface survival and shedding times of BRSV?

• Inc 2-8 days

• Surface survival 6h

• Shedding 2-3 wks

  • (longer if immunocompromised?)

What pathology does BRSV cause?

• Interstitial pneumonia

• Interstitial emphysema

• Formation of multinucleated giant cells/ syncytia, often containing eosinophilic inclusion bodies

How does BRSV present histologically?

• Thickened alveoli septae by lymphocytes and mononuclear cells

^^ normal on L, R = tissue between alveoli infected w/ RSV -> inflam cells, MNGCs -> difficult exchange of gas across thicker surface

• formation of Giant cells in the epithelial lining and in the lumen of the bronchioles and alveoli causing obstruction of airways and impairs lung clearance mechanisms, predisposing to secondary bacterial bronchopneumonia.

  • MNGCs = chronic inflam

^^ alveolar wall thickening on L, normal on R

How does BRSV present grossly?

Characterised by bullae on surface

(sample + PM to confirm)

What is the subfamily & genus of PI3?

Subfamily = paramyxovirinae

Genus = paramyxovirus

How does parainfluenza virus 3 (PI3) present pathologically?

• Bronchitis

• Bronchiolitis

How does PI3 present histologically?

• Alveolar cell thickening & hyperplasia → oxygen exchange impaired

• Possibly also giant cells

• Intracytoplasmic inclusion bodies in lungs days 5-7

  • aggregations of viral capside proteins

What is the family and subfamily of (nfectious bovine rhinotracheitis (IBR)?

• Family —> Herpesviridae

• Subfamily —> Alphaherpesviridaea

What are the features of IBR BHV-1?

• Neurotropic

• Latency in sciatic & trigem nerves

  • infected for life + periodic shedding

  • Recurrence during stress, immunosuppression (even in adults)

• Initial response to infection by cell-mediated immunity → non-specific monocytes + macros

  • if fails, virus able to replicate

What age of cattle does IBR tend to affect?

6-18 months old

Describe the pathogenesis of IBR?

• Sloughing of epithelial cells of mucosa in URT —> loud rasping noise through stethoscope

  

• Necrosis leaves animal open to bacterial infection

• Robust ab response & carrier status

What are the different subtypes of BHV-1 infections?

• Encephalitic subtypes

• Genital subtype

  • Infectious Pustular Balanoposthitis

  • Infectious Pustular Vulvovaginitis

  • Abortion

What does bovine coronavirus cause?

• D+ in calves & poss adults —> winter dysentery → outbreak of scour in adult cattle

• Damages protective mucous layer in resp tract

• Intranasal vacc available

What genus is BVDV?

Pestivirus

What are the two genotypes of BVDV?

BVDV-1 and BVDV-2

What is pathogenesis of BVDV?

• Destroys alveolar macrophages

• Depletes lymphoid tissue —> tonsil, thymus, ileum, BM, intestinal mucosa, lymphoid tissue of Peyer’s patches

Immunosuppressive

How does the time of infection during pregnancy affect the outcome of BVD?

What causes mucosal disease?

• Infection of a BVD PI animal with cytopathic biotype (shown below)

  • No antibodies

  • High mortality

  • Causes cell vacuolation & cell death

  • Severe foul-smelling D+

  • Ulcerations of mucosae & death

What are the main sheep resp viruses?

• OPA (ovine pulmonary adenocarcinoma) / Jaagsiekte

• Maedi

What are the features of OPA/ Jaagsiekte?

• Retrovirus —> betaretrovirus

  • transmission via aerosol

• Oncogenic, acute-transforming

  • The env gene is the oncogene

• Targets type II pneumocytes

• Multifocal lesions

  

• Chronic wasting dx

• Wheel barrow test for profuse white nasal discharge

  

What are the features of maedi?

• Retrovirus

• Small Ruminant Lentivirus

How is maedi transmitted?

Infected colostrum and milk + resp route

What is the pathogenesis of Maedi?

• Infects monocytes

• Progressive lymphoid infiltration and smooth muscle hyperplasia in lungs

• Development of clinical signs takes years

What are the common bacteria that cause resp disease in cattle?

Pasteurellaceae:

• Mannheimia haemolytica

• Pasteurella multocida

  • both of the above are normal commensals of URT, but not LRT

• Histophilus somni

  • commensal of genital tract but as pathogen in resp tract

Mycoplasma

What are the features of pasteurellaceae?

• Gram -ve, facultative anaerobes

  • can be commensal in resp tract

  • faculative anaerobe = can survive in collapsed lung

• Bacilli or coccobacilli

• Host-specific RTX toxin

• Fibrinous Pleurisy & intra-alveolar fibrin deposition

What is shipping fever?

Classically recrudescence IBR followed by Mannheimia haemolytica

• Following stress e.g. transport

What is being shown here?

• Shipping fever → Mannheimia haemolytica

• Blood filled spaces

  • endotoxin acting on endothelial cells lining pulmonary arteries → haemorrhage

How does mannheimia haemolytica present histologically?

• Thrombosis, necrosis, inflammatory cell infiltration in Mannhaemia haemolytica pneumonia

• Dotted line shows the affected area, more purple due to more lymphocytes & monocytes

What are the features of histophilus somni? What is its pathogenesis

• Commensal in the genital tract

• Pathogenic in the resp tract

• Lipoligossacharides (virulence factors) provoke host inflammatory response (e.g. cytokines) → damage to endothelial cells & vasculitis → thrombus formation

• Histamine release → vasocon & increased epithelial permeability

What are the predilection sites of histophilus somni?

What are the features of mycoplasma bovis?

• No cell wall

  • Can't treat with B lactams —> use oxytetracycline / macrolides instead

• Gram +ve

• Found in URT & LRT

  • shed for many months —> reservoirs of infection

• Can survive in epithelial and inflammatory cells

• Infection via resp tract, teat canal or genital tract

• Infection also via AI with infected semen

What pathology does mycoplasma bovis cause?

• “Cuffing” pneumonia

• Septic arthritis

  

• Otitis media

• Mastitis

• Joint ill in calves with concurrent pneumonia

What bacteria can cause resp disease in sheep?

• Mycoplasma ovipneumoniae (arginini, capricolam)

• Pasteurellosis

  • Vaccine commonly used

What aetiological agents cause pasteurellosis?

• Mannheimia haemolytica

• Bibersteinia trehalosi

What increases the risk of respiratory disease?

• Close contact

  • Calves close together, creep feeding in sheep

• Carriers —> age mixing

• Poor ventilation

• Poor immunity

How can sheep respiratory infection be diagnosed?

• Maedi-visna ELISA

• No test for mycoplasma ovipneumoniae

  • can culture but difficult

• PM

How can cattle respiratory infection be diagnosed?

• Serology (Viruses, Mycoplasma, H. somnus)

• PCR on nasopharyngeal swabs or tissue (IBR, PI3, BRSV)

• PM (histology, tissue PCR)

(testing packages available so multiple pathogens tested at once)

What are the general ways you can prevent resp disease?

• Colostrum in first 3hrs of calf life

• Housing & husbandry —> dry environment, ammonia free (lung damage)

• Hygiene & stocking density, correct air flow

• Vaccination