“Classified as BVD or BVDV and one of the most common diseases that affect cattle in the U.S., bovine viral diarrhea can be a major problem for cattle ranchers,” said Zachary McFarlane, assistant professor and beef cattle specialist at Cal Poly San Luis Obispo.
This viral respiratory disease can be detrimental to ranchers and their pocketbooks if not dealt with correctly, McFarlane said. If left untreated, BVD can cause abortion, fetus mutilation or even death.
“Direct contact with infected animals is the primary mode of transmission,” McFarlane said. Saliva, discharge, blood, feces, urine, milk and fetal tissue are all vehicles of transportation for the virus, he said.
John Maas, former extension veterinarian at the University of California, Davis, said the virus has the potential to be spread through objects as well as cattle. From equipment to clothing, Maas said anything coming in contact with an infected animal can transmit the virus.
While a lot of factors such as severity, strain and an animal’s individual immune system can affect the outcome of a BVD contraction, McFarlane said this viral pathogen has the ability to mutate and form various strains. Despite the strains having some differences, he said the symptoms of this disease do not waver.
In the first stages of contraction or in mild cases of BVD, cattle will show signs of fever, droopy eyes, depression, watery eyes and nasal discharge. Severe diarrhea will occur three to seven days after the virus is contracted, McFarlane said.
BVD can also cause oral and intestinal ulcers, loss of appetite, and decreased milk production, Maas added. He said all these symptoms can lead to death within as little as 48 hours.
If the threat of BVD and the negative impacts it brings were not imposing enough for ranchers, McFarlane said the disease can often be difficult to recognize with the naked eye.
“Often times, these infections will be subclinical,” he said. “I think one of the major concerns is that animals aren’t even showing signs of disease. You won’t even know you’re transmitting the issue.”
Once the cattle start exhibiting signs of the virus, it has likely already managed to be spread to several head, he said. While there is no cure for the virus, sick cattle can be removed from the herd to eliminate further spreading of BVD. McFarlane said due to this lack of cure, infected cattle will have to be culled from the herd.
McFarlane said even if BVD can be elusive, he has a few tricks to help ranchers spot the virus early on. Any signs of reduced productivity in an animal should alert producers to a problem, he said. McFarlane suggests cattlemen send a blood, milk or tissue sample to the veterinarian diagnostic lab in their state after noticing a problem in their herd’s productivity. When testing the herd, random samples should be taken from multiple cows to see how widespread the virus is, he added.
Females who contract the disease within the first two months of pregnancy will abort their calves, and McFarlane says those aborted fetuses can also be sent to the lab for testing.
Helping to identify infected cattle is only half the battle, McFarlane said. Ranchers need to be proactive in fighting the risk of BVD before it’s ever reached their operation, he said.
When introducing new cattle to the main herd, Maas said new or sick animals should be quarantined as soon as possible.
“Direct contact with those infected animals is the primary mode of transmission,” McFarlane said. “If you notice something in new cattle, you should nip it immediately.”
“I think one of the major concerns is that animals aren’t even showing signs of disease.”
At the end of the day, McFarlane said the best way for a rancher to actively fight against BVD reaching their operation is to vaccinate their cattle.
He said BVD is found commonly in the cow-calf sector of the beef industry, so he emphasizes the importance of vaccinating both mature cows and young calves.
A modified live virus vaccine will provide protection to cattle during and beyond gestation, McFarlane said. He suggests vaccinating calves at 2 to 3 months of age and then again before they are shipped off the main ranch. Heifers should be vaccinated after they hit a year of age on an annual basis at least three to four weeks before the breeding season, he added.
“You want to ensure you’re providing multiple opportunities for animals to be exposed to the modified live virus with the vaccine before they move on in the production cycle,” he said.
McFarlane said ranchers in the western part of the U.S. often have to ship calves to feedlots in the Midwest. This exposes the livestock to both other forms of infection and stress, which could cause their immune system to weaken, allowing for the BVD virus to affect the cattle.
“In order to make your cattle more marketable, you want to make sure the vaccinations are provided to calves and they’re set up for success,” he added.
Even though McFarlane’s advice on timing of vaccinations is a good rule of thumb, he stresses the importance of reading vaccine labels before developing a vaccination schedule to ensure proper care of cattle. — Megan Silveira, WLJ correspondent
