Bovine Leukemia Virus is a hidden but damaging infection. In fact, it could be in your herd right now, and you would likely not even know it is there. It already has a significant impact on the cattle industry at large.
This virus has already caused significant losses in the cattle industry, though currently more in the dairy industry than in the beef one. Your more direct cost will be due to loss of production, veterinary expenses, as well as replacement costs from the death of affected animals. Some of your indirect costs will be from loss of revenue due to the restrictions placed on your operation. A large Northeast slaughter plant that processes 350,000 cattle each year will condemn about 2,000 carcasses due to this disease.
Once it appears in your place, the ability to get rid of this disease will differ from herd to herd. The primary determining factor will be the producer’s ability to prevent it from horizontally transmitting. Having a good herd health plan in place will go a long way in preventing this from being catastrophic.
What is the bovine leukemia virus?
The bovine leukemia virus is a retrovirus capable of causing cancer in cattle. It is a blood-borne disease that survives in white blood cells. Other names for this virus are Enzootic Bovine Leukosis, malignant lymphoma, or lymphosarcoma. The thing about it is that only about 5% of the cows that are infected will ever develop clinical disease. If that happens, then the primary sign will be the development of tumors.
This virus is transmitted primarily by the transfer of blood or other body fluids from infected animals to non-infected animals. Blood-contaminated needles, dirty syringes, OB sleeves, dehorners, tattoo pliers, hoof knives, and others are potential carriers. As you may have guessed, the way you manage cattle will play a part in its transmission. Close contact with infected nasal and ocular secretions can also play a part.
Though it was initially discovered in the 1970s, this virus has recently seen a surge. A recent study done in eastern Kansas has found that 42 out of 44 hers had at least one cow that tested positive for the Bovine Leukemia Virus. In the same study, they found that 55% of the ones that were tested were positive. To give you some perspective, back in 1997, the National Animal Health Monitoring System reported that only 38.7% were found to have the bovine leukemia virus, and only 11.5% of the ones tested had it.
Possible outcomes
When it comes to the Bovine Leukemia Virus, cattle that are infected have three possible outcomes. The most common one that will happen is that cattle will be asymptomatic and show no signs at all. The next one will occur in about 30% of those infected, which will have an elevated lymphocyte count or persistent lymphocytosis. The last possible outcome is that the cow will develop cancer, but this will happen in less than 5%.
Symptoms
Some of the most common symptoms associated with this virus are appetite, weight loss, and digestive problems. Cattle can also develop fevers or eye problems, along with hind limb paralysis, which can cause some issues with walking. Finally, enlarged lymph nodes or tumors develop in cattle three years old or older.
Treatment and Prevention
Currently, there are no treatments for cattle infected with this virus. This means that prevention and culling are your only options. You need to remember that once a cow is infected, it will be infected for the rest of its life.
Ways to stop it from spreading
When possible, you should separate the negative and positive animals into separate groups. This will help prevent any contact between the two and stop any potential spreading. If you will need to work the two groups, you should do the negative ones first so you won’t accidentally carry the disease on any equipment.
You should always clean and sterilize any equipment that you will be using. These are things like tattoo equipment, ear taggers, nose tongs, hoof knives, and castrating equipment. Use disposable needles and discard them after every use to prevent cross-contamination. Honestly, this is an excellent strategy to follow, even if you are not trying to stop this disease from spreading.
Since the virus is spread through bodily fluids, it may be necessary to provide a colostrum replacer in case any of your cows become infected. As with the others, separate any potentially infected calves away from the others until test results show that they are not infected.
Although it is not necessary, testing your herd every six months can help prevent the spread. The testing will track the producer’s control progress, and you can check if horizontal transmission is occurring and which animals are infected. The Texas A&M Veterinary Medical Diagnostic Laboratory offers testing for this virus at $27 each.
Keep the Bovine Leukemia Virus from showing up in the first place.
The main thing to help keep this virus from showing up is to test every new animal that comes into your operation. If possible, separate them from your herd until you can determine their status. Be sure to manage all new arrivals as positive until the test results come back with a different story.
As with any other disease, do not buy animals from anyone you do not know. This may be a fairly dumb thing to say, but there are some people who would do that just because it seems like a good deal. If you do not know the source, you could be bringing anything to your place. Just remember: if it sounds too good to be true, then it probably is.
There are a few states that have developed voluntary programs for the control of the Bovine Leukemia Virus. These programs can certify BLV-free herds by removing infections and certifying that the herd is BLV-free. For the herd to be certified BLV-free, it must pass three consecutive negative tests 60 to 90 days apart.
