anthrax; catarrhal; bovine; disease; rabies; fever

Cattle production: Bovine viral diarrhoea and your herd

Question: I farm about 300 head of Hereford cows. There have been deaths among my young heifers, and the tests show that BVD is the possible cause. What should I do if BVD is confirmed?

Bovine viral diarrhoea (BVD) is a highly infectious disease that is characterised by the suppression of the immune system.

  • Infected animals are therefore extremely susceptible to other diseases.
  • The disease can manifest in several syndromes in a herd, such as mild diarrhoea from which most animals recover spontaneously.
  • The affinity of the virus for the unborn calf is of great economic importance.
  • When a pregnant cow that is not immune to the disease is exposed to the virus, the death of the embryo, abortion or congenital defects in the calf might occur.


  • The main source of the infection in a herd is permanently infected animals.
  • When a female animal that is not immune to BVD is exposed to the virus during the period from day 42 to day 125 of pregnancy, the foetus develops an immune-tolerance to the virus.
  • The foetus therefore loses the ability to develop immunity to the disease and remains a carrier of the virus for the rest of its life.
  • Permanently infected animals are usually – but not always – frail and extremely susceptible to other diseases.
  • From time to time, these animals excrete large quantities of viruses, especially when they are stressed, such as when they are in a feedlot.
  • Research has shown that about 6% to 8% of the calves in feedlots have to be treated more than once, particularly for pneumonia, are permanently infected animals.
  • The occurrence of permanently infected animals in commercial herds is about 1% to 2%.
  • BVD is a possible cause when a herd has a history of poor reproduction, including poor conception rates, abortions or calves showing congenital defects.
  • It is essential that other diseases, such as contagious abortion (brucellosis), vibriosis and trichmonasis, be eliminated as causes.

Also read:
Livestock production: Testing your herd for brucellosis (contagious abortion)
Livestock production: What to do if your herd tests positive for brucellosis (contagious abortion)
Livestock production: How to prevent and treat brucellosis (contagious abortion) in your herd


  • BVD can be controlled by ridding the herd of infected carriers, as well as by using vaccines correctly.
  • Discuss an inoculation programme with a veterinarian.
  • There is more than 1 way to identifying permanently infected animals.
  • The most commonly used method is to collect a piece of skin, from an ear nick for example, in a 10% formalin solution.
  • The sample should be sent to a facility like the Department of Pathology, Faculty of Veterinary Science at Onderstepoort in South Africa as soon as possible.

Also read: Livestock production: Check and revise vaccination schedules

  • This article was written by Prof. Leon Prozesky and appears in Ask the vet: What cattle farmers should know (1), compiled by Dr. Faffa Malan.

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