Bovine leukosis virus (BLV) is a very common disease, but many people do not believe it is of economic importance for commercial dairies. Some estimates put prevalence at >40% with some herds exceeding 80%.
Although some dairy farms have standard operating procedures (SOPs) in place to control BLV, the norm for most modern operations is to inject multiple cows with a single needle. This needle is often inserted into a multiple-dose vial many times, and is usually changed only after it becomes dull.
With the recent increased incidence of other blood-borne pathogens in cattle populations, such as Anaplasmosis, we should reconsider our biosecurity practices with injections.
In my early days of practice, we identified a herd with a very high prevalence (>80%) of BLV infection in adult cows. We routinely necropsied all deaths in this herd, but were often frustrated with the lack of any significant findings.
When necropsies failed to reveal gross (visual) lesions, we sent tissue samples to a diagnostic lab for microscopic examinations (histopathology). Surprisingly, a significant number of cows exhibited early stages of cancer in vital organs – but no visible tumors. This forced me to reconsider the economic impact BLV might have on production and reproduction, and the likelihood we were significantly underdiagnosing lymphosarcoma in many herds.
We developed a herd control program and, over a three-year period, were able to reduce BLV prevalence to less than 20% of the herd. Today, the prevalence is very low.
The control program focused on minimizing the transfer of blood between animals, either through disinfection or changing needles. Is this a practice we should consider more widely?
Many owners and managers of large dairy herds believe changing needles for each cow is labor intensive and costly, without obvious health and economic benefits. I would challenge you to reconsider this. Experience from a number of large herds supports the practice of using a new needle for each injection, and only using a new needle to draw from a multiple-dose vial.
Using basic calculations, using new needles for each injection in routine vaccinations and synchronization programs would cost a 1,000-cow herd less than $5,000/year. If we assume a 20% prevalence rate of BLV in a herd, and that about 5% of infected cows will develop clinical lymphosarcoma, the economic losses of this single disease would be three to four times the cost of changing needles. Does it seem like this may be a topic for further discussion?
Using a new, sharp needle potentially reduces pain/discomfort, and may be safer for the person administering the injection, as there is potentially less reaction from the animal (a kick or movement). A clean needle will also reduce the risk of abscess formation related to bacterial contamination.
We have also seen an increase in another blood-borne bacterial disease, Anaplasmosis, in many regions of the United States. It can be transmitted by biting insects and ticks, and is readily transmitted through blood-contaminated equipment, such as needles and syringes.
Given the ongoing public pressure and scrutiny of the livestock industry, we must be able to justify the common practices we perform. Many are easily defensible for the health and welfare of our cattle. However, can we easily justify multiple injections with a single needle, when this practice in humans would be considered beyond belief, and would not be the standard of care for other domestic species, such as dogs, cats and horses?
This is a new concept in dairy health management. While it won't be accepted by all, at least take the time to consider it. If progressive industry leaders can set the expectation for the standard of care, others will follow.
Mark Thomas is a veterinarian and partner of Dairy Health &; Management Services, LCC and Countryside Veterinary Clinic, LLP, Lowville, N.Y. He is currently vice president of the American Association of Bovine Practitioners. Contact him via e-mail at firstname.lastname@example.org.