Bovine Leukemia Virus is a hidden but damaging infection. In fact, this thing could be in your herd right now and you would likely not even know it is there. It already has a major 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 costs, 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.
The ability to get rid of this disease once it appears in your place will be different from herd to the herd. The major 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 that is 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.
The primary way that this virus is transmitted is by the transfer of blood or other body fluids from infected animals to non-infected animals. Things like blood-contaminated needles, dirty syringes, OB sleeves, dehorners, tattoo pliers, hoof knives, and others are potential carriers. So as you may have guessed the way that 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 back in the 1970s this virus has seen a surge as of late. 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 3 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 the ones infected will have an elevated lymphocyte count which is referred to as 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 that are associated with this virus are appetite, weight loss, and digestive problems. They can also develop a fever or eye problems along with hind limb paralysis which can cause some problems walking. Finally enlarged lymph nodes or tumors develop in cattle 3 years old or older.
Treatment and Prevention
Currently, there are no treatments that exist for cattle that are infected with this virus. This means that prevention and culling are your only options to deal with this. 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 it is possible you should separate the negative and the positive animals into separate groups. This will help prevent any contact between the two and stop any potential spreading. If you will be needing 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 a good strategy to follow even if you are not trying to prevent 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 end up being infected. As with the others separate any potentially infected calves away from the others till test results show that they are not infected.
Although it is not necessary testing your herd every 6 months can be helpful in preventing the spread. Your control progress will be tracked, and you can check if the horizontal transmission is occurring and which ones are infected. The Texas A&M Veterinary Medical Diagnostic Laboratory offers testing for this virus at $27 each.
Keep 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 is coming into your operation. Separate them from your herd until you can determine their status if possible 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 that 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. BLV-free herds can be certified by these programs 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.
