Bovine Leukosis – An Increasing Problem In Kansas
More Kansas beef producers are reporting problems with Bovine Leukosis in their cow herds. Bovine Leukosis is not a new cattle disease, but is caused by the Bovine Leukosis Virus (BLV), a virus that has been around since the 18th century. Dairy producers have contended with the problem for years; however, major problems with the disease in beef herds have seemed to be on the increase in recent years. The most frequent complaint is that individual cows suddenly start going downhill and die. The loss rate in some Kansas herds has reportedly approached 5% per year. The disease-causing virus infects white blood cells (lymphocytes) and is transmitted by any mechanism that allows the transfer of blood from one animal to another. This includes biting flies, ticks, needles, tattoo pliers, ear tagging equipment, castration and dehorning equipment, etc. In a small number of instances, the virus is also transmitted from the cow to the fetus in utero or in colostrum. Infected cows may exist as carriers in the herd for several years before becoming sick. Most of the time the first sign observed is a cow that starts losing body condition when compared to other similar-aged animals in the herd. This may occur gradually or rapidly. In some cases, swollen lymph nodes will occur that are externally visible as tumors. There is no treatment for the disease, and the cow will eventually die. Cows detected early may possibly be salvaged; however, if there are any lesions observed at slaughter the animal will be condemned and not be allowed to enter the human food chain.
The best management strategy to control the effects of the disease depends upon the level of disease incidence in the herd. Blood tests of suspicious animals should lead to herd-wide testing if suspected animals are found to be positive. If the incidence in the herd is low, culling all positive individuals will quickly rid the carriers from the herd. If the incidence is high, sorting the herd into 2 herds (BLV negative and positive herds) and maintaining them as separate herds will allow the producer to stay in business while working their way through the diseased animals in the positive herd.
To help prevent transmission of the disease, especially when trying to maintain a negative herd in proximity to a positive herd, several different management procedures should be implemented. Disinfect needles between animals (except those used to administer modified live or live vaccines, in which case disposable needles should be utilized and changed between every animal). Disinfect all tattoo pliers, ear tagging equipment, and surgical equipment between animals.
Follow recommended management procedures for fly and tick control. If you
lose a cow to Bovine Leukosis Virus, do not keep her calf for a replacement animal without first testing the calf for the disease at weaning time. Test all retained replacements before adding them to the herd. If you buy replacements, buy only animals that come from Bovine Leukosis Virus tested-negative herds or herds that have tested free of Bovine Leukosis Virus.
If you have cows (or bulls) that start going downhill unexpectedly, have your veterinarian test suspect animals. If Bovine Leukosis Virus is in the herd, producers can test to find and remove infected animals, utilize management procedures to reduce transmission of the disease, and ultimately free the herd of the disease.
Source: Larry Hollis, D.V.M., M.Ag, extension veterinarian
More Kansas beef producers are reporting problems with Bovine Leukosis in their cow herds. Bovine Leukosis is not a new cattle disease, but is caused by the Bovine Leukosis Virus (BLV), a virus that has been around since the 18th century. Dairy producers have contended with the problem for years; however, major problems with the disease in beef herds have seemed to be on the increase in recent years. The most frequent complaint is that individual cows suddenly start going downhill and die. The loss rate in some Kansas herds has reportedly approached 5% per year. The disease-causing virus infects white blood cells (lymphocytes) and is transmitted by any mechanism that allows the transfer of blood from one animal to another. This includes biting flies, ticks, needles, tattoo pliers, ear tagging equipment, castration and dehorning equipment, etc. In a small number of instances, the virus is also transmitted from the cow to the fetus in utero or in colostrum. Infected cows may exist as carriers in the herd for several years before becoming sick. Most of the time the first sign observed is a cow that starts losing body condition when compared to other similar-aged animals in the herd. This may occur gradually or rapidly. In some cases, swollen lymph nodes will occur that are externally visible as tumors. There is no treatment for the disease, and the cow will eventually die. Cows detected early may possibly be salvaged; however, if there are any lesions observed at slaughter the animal will be condemned and not be allowed to enter the human food chain.
The best management strategy to control the effects of the disease depends upon the level of disease incidence in the herd. Blood tests of suspicious animals should lead to herd-wide testing if suspected animals are found to be positive. If the incidence in the herd is low, culling all positive individuals will quickly rid the carriers from the herd. If the incidence is high, sorting the herd into 2 herds (BLV negative and positive herds) and maintaining them as separate herds will allow the producer to stay in business while working their way through the diseased animals in the positive herd.
To help prevent transmission of the disease, especially when trying to maintain a negative herd in proximity to a positive herd, several different management procedures should be implemented. Disinfect needles between animals (except those used to administer modified live or live vaccines, in which case disposable needles should be utilized and changed between every animal). Disinfect all tattoo pliers, ear tagging equipment, and surgical equipment between animals.
Follow recommended management procedures for fly and tick control. If you
lose a cow to Bovine Leukosis Virus, do not keep her calf for a replacement animal without first testing the calf for the disease at weaning time. Test all retained replacements before adding them to the herd. If you buy replacements, buy only animals that come from Bovine Leukosis Virus tested-negative herds or herds that have tested free of Bovine Leukosis Virus.
If you have cows (or bulls) that start going downhill unexpectedly, have your veterinarian test suspect animals. If Bovine Leukosis Virus is in the herd, producers can test to find and remove infected animals, utilize management procedures to reduce transmission of the disease, and ultimately free the herd of the disease.
Source: Larry Hollis, D.V.M., M.Ag, extension veterinarian
