Pestivirus infection (cattle)

Also known as Mucosal disease or Bovine viral diarrhoea virus (BVDV)

Description

Pestivirus is a viral infection of cattle present in feedlots and beef and dairy herds in Australia. Lifelong carriers of the virus, including cases of mucosal disease, are a consequence of infection in early foetal life (usually before 100 days gestation). These lifelong carriers are often termed PI (persistently infected).

Foetal infection which persists into and through post-natal life will have resulted from one of two circumstances:

• Infection of a susceptible dam, probably through contact with a virus carrier, in early (usually 30 to 100 days) pregnancy. Immune tolerance to the virus is induced; or,
• The dam herself is a persistently viraemic and immunotolerant animal.

Pestivirus infection is associated with:

• Embryonic or foetal death
• Reduced fertility
• Congenital malformations
• Perinatal mortality
• Poor growth rates
• Respiratory disease
• Non-specific immunosuppression
• Disease with mortality in calfhood or early adult life

Control

• Vaccination of all breeding cattle
• Removal of carrier animals and maintain strict bio-security (including testing of all animals entering the property)
• Livestock management to ensure all breeding heifers have been infected with pestivirus well before mating

Diagnosis and tests available

Diagnosis

Diagnosis is based on recognition of a syndrome consistent with pestivirus infection in combination with confirmatory laboratory testing.

Tests available

¹ Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.

Specimen requirements

Detection of virus in live animals

Blood (with anti-coagulant)

• 10 ml of blood collected into an EDTA tube
  • Submitted chilled

Blood (without anti-coagulant)

• For animals over 3 months of age collect 10 ml of blood into a plain red top tube
  • Do not use serum separator tubes.
  • Submit chilled

Hair

• Hair samples may be used to detect the virus using the PI-test®.
• Hair samples must be submitted to the laboratory promptly and within 2 weeks of collection
• Collection kits can be ordered free of charge by calling Customer Services on 1800 675 623 or ordering online
• The kits contain detailed notes on hair collection. The collection guide is also available online.

Milk

• Bulk milk
  • Submit chilled, ideally in milk preservative.
  • If milk preservative is unavailable samples may be frozen prior to submission.

Semen

• Semen straws or raw semen (please contact the laboratory prior to submission. For regulatory testing samples must be shipped at specified temperatures)

Skin

• Ear notch samples (skin) can be used for animals of any age.
  • Submit chilled in sterile container or in ear notch media
  • When sampling groups of >10 animals, ear notch samples should be submitted in ear notch media (media can be requested online)

Swab

• Nasal swab collected from affected animal
  • Send in viral transport media (PBGS)
  • PBGS can be requested online
• Used in cases of respiratory disease, where one is trying to detect acute infections rather than PI animals.

Detection of virus in dead animals and foetuses

Fresh tissues

• Spleen, lung or lymph node
  • Submit chilled

Skin

• Ear notch (skin) can be used for animals of any age
  • Submit chilled

Detection of antibodies in live animals

Blood (without anti-coagulant)

• 10 ml of blood collected in a plain red top tube
  • Submit chilled
• Serum samples from 10-15 cows may provide evidence of the extent of herd infection. This information may help with management decisions regarding pestivirus. In cases of embryonic mortality or abortion this information may allow more selective investigation to confirm pestivirus involvement.
• The pestivirus antibody AGID is usually preferred to the ELISA for disease investigations, as the time of infection may be inferred from the results

Milk

• Bulk milk samples
  • Submit chilled

Detection of antibodies in foetuses

Foetal fluid

• Pericardial, pleural or peritoneal (in order of preference).
  • Submit chilled
• For IgG test initially and for pestivirus antibody if the IgG level is elevated.
• Please note on the submission form I if colostrum was given to a neonate

Note

• Care should be exercised when interpreting serological results from calves less than six months of age because the detection of antibodies may be the result of colostral transfer rather than previous infection.
• Where pestivirus infection and/or mucosal disease has been confirmed, further testing of maternal relatives and enquiry into the history and management of the herd may indicate how or when infection occurred, and what steps can be taken to eliminate the problem.
  
  A newborn calf with congenital deformities, the product of infection at 120-180 days gestation, may be seropositive. Some stillborn apparently normal calves can also be seropositive.
  PI animals are usually antibody negative at birth, but will acquire specific antibody from their dam with colostrum. This colostral antibody may persist up to 6 months. Demonstration of an antibody titre in a live animal usually indicates the animal is not persistently infected, assuming it is old enough to have lost maternal antibody (> 6 months). However, around 5% of PI animals may have antibody to pestivirus.