Used needles, unsterilized equipment and biting insects are all contributors to the tumor growing, lymph node swelling Bovine Leukemia Virus (BLV), that is spread through blood transfers or related products between cattle.
“The prevalence of BLV is high in the US. The most recent surveys in the USA estimate that 44 percent of dairy and 10 percent of beef cattle are infected with the virus,” says University of Tennessee veterinarian Lew Strickland. “In general, the prevalence of viral infection increases with age, with clinical signs appearing at 5-6 years of age.”
According to Strickland, along with other common day-to-day operational procedures such as tattooing, rectal palpations and dehorning are a hot bed for transmitting the virus, infected Dams can spread BLV to her calf.
“An infected Dam has the potential to transmit BLV directly to her fetus, either by contact with infected blood, or postpartum from the dam to the calf through ingestion of infected colostrum,” he explains. “Any material that is blood contaminated or lymphocyte rich has the potential to infect animals with BLV.”
There is a 5 percent chance cattle infected with BLV will develop lymphosarcoma, says Strickland, which may result in the development of tumors in specific locations of the bovine’s body and swelling of the lymph nodes.
“Tumors of the abomasum may lead to signs of cranial abdominal pain, melena (digested blood in feces), or abomasal outflow obstruction. Pelvic limb paresis progressing to paralysis can occur in animals with spinal lesions. Tumors in the eye socket cause protrusion of the globe, resulting in exposure keratitis,” explains Strickland. “Tumors of the heart may be mild and undetectable clinically, or may cause arrhythmias, murmurs, or heart failure. Uteri ne lesions may lead to reproductive failure or abortion.”
According to him, management and prevention steps are essential to cracking down on BLV since there are no treatments or vaccines for BLV. Strickland advises producers implement an annual testing program, along with testing all cattle prior to them entering a herd. If cattle have a positive BLV test, they are to be moved out of the clean herd to help prevent transmission.
It’s also strongly advised to disinfect equipment between animals and to use new sterilized needles for injections and blood collections.
Strickland’s list includes:
•Test all cattle entering the herd for BLV, and isolate them for 30 to 60 days. Test again at the end of the isolation period.
• Implement annual testing.
• If your herd is infected with BLV, maintain 2 herds; clean and infected.
• Perform all veterinary procedures on BLV-positive cows last.
• Use individual sterile needles for transdermal injection or blood collection.
• Disinfect all equipment between animals.
• Wash and rinse instruments in warm water, then submerge in an appropriate disinfectant.
• Use electric dehorners, or disinfect dehorning equipment between animals.
• Replace examination gloves and sleeves between animals.
• Use milk replacer to feed preweaned calves.
• Heat-treat or pasteurize colostrum.
• 140º for 30 minutes will kill BLV without damaging IgG antibodies.
• Use BLV-seronegative recipients for embryo transfer.
• Reduce numbers of biting insects.