Impact of BVD can linger if undetected in carrier

KANSAS CITY, Mo. — Bovine viral diarrhea lurks wherever cattle are raised.

This mutating virus presents diverse clinical symptoms, and control is elusive, said scientists during an April 7 BVD symposium in Kansas City, Missouri.

Producers may not see diarrhea among calves, but poor growth and respiratory and reproduction problems are common among the infected.

“We have to understand this virus causes a lot more symptoms than diarrhea,” said Dan Grooms, who specializes in infectious diseases at Michigan State University.

“Not all studies have actually showed the impact of BVD on performance because there is so much variability in the virus. There are some viruses that tend to be more pathogenic than others, and there is variability in the type of cattle.”

BVD is an RNA virus and a member of the pestivirus family.

These viruses mutate rapidly and cause similar disease in cattle, sheep, pigs, camelids and cervids, such as border disease virus in sheep and classical swine fever in pigs.

Two types, BVD1 and BVD2, are seen in cattle, and a third new pestivirus was identified as the HoBi-like virus 10 years ago.

“This is a virus everybody should learn about. It has been called BVD Type 3,” Grooms said.

Clinical signs for these three viruses are similar to influenza viruses in people.

The results in cattle may be mucosal disease, poor performance, immuno-suppression, acute diarrhea, congenital defects, abortion, early embryonic death or subclinical infections.

The World Organization for Animal Health says prevalence varies globally. It encourages control or eradication through biosecurity, vaccination, surveillance and removal of persistently infected animals.

Persistently infected calves are the result of mothers becoming infected 60 to 125 days into gestation. The fetus thinks the virus is part of itself and becomes tolerant to it. As a result, no immune response is developed.

An abortion may result or the calf is born but fails to thrive and dies. It may have deformities.

Some are born and look normal, but they are carriers throughout their lives and pass the virus in blood, nasal secretions, saliva, feces, urine, semen and milk.

“These persistently infected fetuses or calves, when they are born, are the major source of transmission of this virus in the cattle population,” said Grooms.

Some can live to reproductive age and may become pregnant and infect their unborn calves.

“You can get families of PIs but that is a rare event,” he said.

These calves can do considerable damage if they go undetected: $25 per year per beef cow exposed to the disease and $42 to $93 per exposed animal in the feedlot.

Pregnancy rates fall by five percent in cow-calf herds containing persistently infected animals.

“This can be pretty economically significant, especially with the price of calves,” Grooms said.

“It can still be a big impact if you are losing five percent of your pregnancies.”

Considerable research has been devoted to the disease and its complications.

Julia Ridpath, lead scientist with the U.S. Department of Agriculture in Ames, Iowa, said some producers blame genetics or nutrition when infected animals are found.

Cattle with high virulence BVD put on weight in belly fat rather than muscle and long bone. It has also been learned that the disease destroys the thymus gland, needed to launch an immune response.

“These animals are not what they were before they were exposed,” she said.

Control encompasses an entire herd health plan with vaccination, testing and biosecurity measures.

“If we are really serious about controlling BVD, we can’t just rely on vaccines,” Grooms said.

“They are a great tool, but they have to be combined with other strategies.”

  • your carcass compost pile doubles as a sled riding hill for your kids
  • every animal is walking around with strange looking V shaped notch in the ear
  • your drug rep says it can’t be BVD because you used their vaccine
  • your calf barn doubles as a halloween house of horrors
  • you think BVD is caused by a bad veterinarian
  • your thoughts about your breeding program and the presidential election are the same
  • your nutritionist blames poor health on your previous nutritionist, who blames it on his predecessor
  • you have cattle on your farm named Runty, Nubby, Pipsqueak and Shorty
  • you just won a million dollar lawsuit against the electric company because of stray voltage, but herd health is still a problem
  • you have lost everything but your BVD

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