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Newsletter of Penn Dutch Cow Care October 2004

Hi Folks,

Occasionally, I find animals with various lumps and bumps in odd spots on apparently healthy mature animals. After ruling out an abscess (usually due to location) or trauma, the thought of cancer tumor comes to mind. Cattle can suffer from cancer just as any animal can. Other names for cancer that farmers may hear are: leucosis, leukemia, enzootic bovine leukosis. Interestingly, there is a virus (bovine leukemia virus, "BLV" , is a retrovrus), that can be transmitted cow to cow by a single drop of blood. The general problem is an increasing amount of cancerous white blood cells, leucocytes, being produced from within the lymph nodes. A lot of the original research after the original discovery of the virus was carried out at the University of Pennsylvania, School of Veterinary Medicine in the early 1960' s. About 85% of the dairy cattle in the United States are thought to harbor antibodies to the virus. In other words, test positive animals have been exposed to it at some point in life and therefore show antibodies to it (their reaction to the challenge). One of the main reasons for the high incidence of it in this country is that it can be contagious between cows. However, it is well known that it depends on familial genetics whether or not an animal will actually come down with cancer. Immunogenetic strength or weakness will determine the outcome of an animal that is exposed to the virus. In general, only 1-3% of the animals exposed will get clinical cancer.

The symptoms can be quite plain or they can be very vague. The main symptoms are tumor growths which are visible or felt by touch anywhere over the body, but mainly at lymph nodes. The supramammary lymph nodes are commonly involved. These lymph nodes are located at the top of the udder near the attachment to the body when looking from the rear. In a normal cow, you can feel these if you grasp the udder in that area and feel for them. These will be enlarged if there is mastitis, but if they are enlarged with no history of mastitis, consider a tumor. The pre-femoral (in front of the rear leg along the abdomen) and pre-scapular (just in front of the shoulder) lymph nodes also are occasionally enlarged. During rectal exam, lymph nodes may be felt internally in the abdomen at the iliac nodes. Sometimes, it will affect an eye. Early on, the third eyelid (nictitans) will have a small growth on it which appears a bit brighter pink, and, over time, becomes larger and larger, eventually creating an infected, swollen eye. Sometimes, doing surgery for a displaced abomasum, I will see small tumors on the stomach wall and alert the farmer to their presence. These are the most common places. However, small tumors in the spinal cord are also a real possibility. And so, with older down cows, this must be considered as a possibility. But, unless I can manually feel or see tumors, I really dislike diagnosing "cancer" in a cow, because of lack of physical confirmation.

Obviously, cancerous tumors, especially by the time they are diagnosed out in the field, usually keep progressing and ultimately the cow dies from it. There can be, however, spontaneous remission, but don' t count on it. I have observed this only one time when I palpated a large tumor at the internal iliac node on a fresh cow whose rear leg was bowed out. I thought the farmer would ship her right away, but he didn' t. So at the next herd check I asked if I could reach in her to check on the tumor since she was standing better and it had shrunk to near normal. That was the only time.

As there is no cure for this kind of cancer, the best thing to do is try to prevent it from spreading. Since only one drop of blood transmitted to another cow is all it takes to infect a cow, in herds that are trying to become BLV free, individual sleeves should be used for rectal palpation, individual needles should be used for injections, and scrupulous detail to fly control is paramount. Flies can transmit the blood easily. They take a bite from an infected cow, the cow swats at the fly with her tail, then the fly goes to the next cow with the wet blood on its proboscis and proceeds to bite her, thus infecting her with the still wet blood from the first cow. Unless all three measures are taken seriously (individual sleeves, individual needles, serious fly control), the chances of reducing enzootic bovine leukemia from a herd will be very difficult. It can be killed by pasteurization. New born calves can be exposed to it via colostrum and milk. Calves should either receive colostrum from known BLV negative animals or be given pasteurized milk on those few farms actively trying to eliminate BLV from the herd. A rare form of this kind of cancer is the juvenile onset form seen in yearlings. This may be the result of a calf ingesting infected milk or perhaps by some spontaneous mechanism combined with the animal' s familial susceptibility to the disease.

There are certainly as many cancer types as there are different cell types. In other words, cows can get bone cancer, kidney cancer, brain cancer, gum cancer, skin cancer, ovarian cancer - but all these are exceedingly rare as compared to the enzootic bovine leukemia virus, due to its contagious nature. Perhaps these other cancers are not seen much also due to the younger animals that are in production these days. As a herd has older cows (usually the grazing herds) that live longer lives, conditions such as cancer may be encountered more often.

Levi S. King, 523 Valley Rd, Quarryville, has 7 cows for sale (certified organic), 2 are fresh and the others further out in lactation. Five are Jersey-Holstein crosses and 2 are Holstein. His phone number is 786-9183, 7:15-7:30 Tuesday evenings.

 

For Bovinity Health, information on functional alternatives to antibiotics see:
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