LEUKEMIA? LYMPHOMA? THIS MAY BE THE WORST--BRACE YOURSELF!
I hate to tell you this, but the bovine leukemia virus is found in more than three of five dairy cows in the United States! This involves about 80% of dairy herds. Unfortunately, when the milk is pooled, a very large percentage of all milk produced is contaminated (90 to 95 per cent). Of course the virus is killed in pasteurisation--if the pasteurisation was done correctly. What if the milk is raw? In a study of randomly collected raw milk samples the bovine leukemia virus was recovered from two-thirds. I sincerely hope that the raw milk dairy herds are carefully monitored when compared to the regular herds. (Science 1981; 213:1014).
This is a world-wide problem. One lengthy study from Germany deplored the problem and admitted the impossibility of keeping the virus from infected cows' milk from the rest of the milk. Several European countries, including Germany and Switzerland, have attempted to "cull" the infected cows from their herds. Certainly the United States must be the leader in the fight against leukemic dairy cows, right? Wrong! We are the worst in the world with the former exception of Venezuela according to Virgil Hulse MD, a milk specialist who also has a B.S. in Dairy Manufacturing as well as a Master's degree in Public Health.
As mentioned, the leukemia virus is rendered inactive by pasteurisation. Of course. However, there can be Chernobyl like accidents. One of these occurred in the Chicago area in April, 1985. At a modern, large, milk processing plant an accidental "cross connection" between raw and pasteurised milk occurred. A violent salmonella outbreak followed, killing 4 and making an estimated 150,000 ill. Now the question I would pose to the dairy industry people is this: "How can you assure the people who drank this milk that they were not exposed to the ingestion of raw, unkilled, bully active bovine leukemia viruses?" Further, it would be fascinating to know if a "cluster" of leukemia cases blossoms in that area in 1 to 3 decades. There are reports of "leukemia clusters" elsewhere, one of them mentioned in the June 10, 1990 San Francisco Chronicle involving No. California.
What happens to other species of mammals when they are exposed to the bovine leukemia virus? It's a fair question and the answer is not reassuring. Virtually all animals exposed to the virus develop leukemia. This includes sheep, goats, and even primates such as rhesus monkeys and chimpanzees. The route of transmission includes ingestion (both intravenous and intramuscular) and cells present in milk. There are obviously no instances of transfer attempts to human beings, but we know that the virus can infect human cells in vitro. There is evidence of human antibody formation to the bovine leukemia virus; this is disturbing. How did the bovine leukemia virus particles gain access to humans and become antigens? Was it as small, denatured particles?
If the bovine leukemia viruses causes human leukemia, we could expect the dairy states with known leukemic herds to have a higher incidence of human leukemia. Is this so? Unfortunately, it seems to be the case! Iowa, Nebraska, South Dakota, Minnesota and Wisconsin have statistically higher incidence of leukemia than the national average. In Russia and in Sweden, areas with uncontrolled bovine leukemia virus have been linked with increases in human leukemia. I am also told that veterinarians have higher rates of leukemia than the general public. Dairy farmers have significantly elevated leukemia rates. Recent research shows lymphocytes from milk fed to neonatal mammals gains access to bodily tissues by passing directly through the intestinal wall.
An optimistic note from the University of Illinois, Ubana from the Department of Animal Sciences shows the importance of one's perspective. Since they are concerned with the economics of milk and not primarily the health aspects, they noted that the production of milk was greater in the cows with the bovine leukemia virus. However when the leukemia produced a persistent and significant lymphocytosis (increased white blood cell count), the production fell off. They suggested "…a need to re-evaluate the economic impact of bovine leukemia virus infection on the dairy industry". Does this mean that leukemia is good for profits only if we can keep it under control? You can get the details on this business concern from Proc. Nat. Acad. Sciences, U.S. Feb. 1989. I added emphasis and am insulted that a university department feels that this is an economic and not a human health issue. Do not expect help from the Department of Agriculture or the universities. The money stakes and the political pressures are too great. You're on you own.
What does this all mean? We know that virus is capable of producing leukemia in other animals. Is it proven that it can contribute to human leukemia (or lymphoma, a related cancer)? Several articles tackle this one:
1."Epidemiologic Relationships of the Bovine Population and Human Leukemia in Iowa". Am Journal of Epidemiology 112 (1980): 80
2."Milk of Dairy Cows Frequently Contains a Leukemogenic Virus". Science 213 (1981): 1014 3."Beware of the Cow". (Editorial) Lancet 2 (1974):30
4."Is Bovine Milk A Health Hazard?". Pediatrics; Suppl. Feeding the Normal Infant. 75:182-186; 1985