Transmissible Cancer

     Cancer is not considered a contagious disease in the strictest sense, but through the years, evidence has mounted that cancer is at least slightly transmissible, possibly from human to human as in cancer of the cervix from herpes virus, but especially from animals to humans as in leukemias and lymphomas.

     In addition to the venereal spread of herpes viruses, they are also known to be present in various dairy products including “sterile” milk, raw milk, and chocolate milk.  Cancer producing viruses actually demonstrated to resist pasteurization temperatures are Rauscher and Moloney murine leukemia viruses, Moloney and Rous sarcoma viruses, adenovirus 12, herpes simplex virus, and reovirus 1 (not considered a cancer-producing virus, but may somehow assist in the cancerous process as they are found in human lymphomas and cat leukemia).  Lip and cervical cancers show reactions to antibodies made with herpes simplex virus antigens obtained from animal cells infected with herpes simplex virus, giving evidence in favor of the possibility that this virus causes both lip and cervical cancer.  Normal human cells do not react with the antibodies.

     Indefinite statements are often expressed concerning identifying a certain cancer virus in humans by the antibodies produced in an animal.  We show no such insecurity with other viruses: why should we do so with cancer viruses?  If we find antibodies to smallpox viruses or measles in an animal we confidently say that the animal has had the human infection of smallpox or measles.  But when a cancer virus stimulates an antibody response in an animal we do not confidently state that the animal was infected by that particular virus.  It is as if we are afraid to say that the virus that caused cancer in the cow or dog is the same virus that produces an identical antibody in humans.

     For years, conclusions in regard to cancer have been held back by reluctance to accept the evidence of antibodies.  It was not until 1981 that definite statements were made in medical literature declaring that the cause of leukemia in humans is “an RNA agent similar to those causing leukemia in animals but never before clearly tied to the condition in man.” human cancer has been strangely neglected, considering the prominent position animal products have in the marketplace, and pets have at the fireside.


     It is now understood that a relatively harmless virus may serve as a “helper virus” to activate a potentially dangerous one to induce cancer.  A number of virus diseases transmitted by animals could be used by cancer viruses as “helper viruses.”  Other viruses are sometimes required in order to help a cancer virus of the ribonucleic acid (RNA, an essential component of cells) or DNA-types to produce an actual cancer in an animal.  In 1972, The Journal of the American Medical Association carried this statement: “Although some viruses, which may occur widely in food and water, are not considered to be pathologic for man, it has been speculated that when they infect an unnatural host, such as man, they may play a roll in carcinogenesis” (cancer production).


     There is increasing evidence that cancer virus are spread through the same process as other infectious diseases.  For more than sixty years it has been known that viruses induce cancer in chickens, and it has been around forty years that virus-caused tumors in animals were first discovered.

     To transform a cell from normal to cancerous, one method a virus uses is to dissolve the protein coat of the virus first into the cell membrane of the victim cell.  Then the coat opens up and becomes one with the cell membrane, about like adding a link to a chain.  Next, the particle containing the gene, the genome DNA or RNA, is released into the cell, a process called viropexis.  The virus particle then acts as independent genetic material inside the host cells using the cells own mechanisms to reproduce itself abundantly.  This particle may remain a part of the genetic information in the nucleus of the cells, even when the virus itself can no longer be detected in the daughter cells, as it is lying dormant to be activated by radiation, excessive fats, a carcinogen, or something else, at some later time or future generation.

     The DNA virus include polyoma virus, simian, adenoviruses, herpes viruses, and pox viruses.  Two herpes viruses are associated with forms of human cancer.  Both types of viruses multiply within the host cells and produce antigens.  The Bittner cancer viruses of mouse milk have been seen by the use of the electron microscope.  Newly born mice pups taken from their mothers and put with mothers having no virus particle have one-fourth the cancer of those fed by their natural mothers.  Journal of American Medical association

     In one study, a virus that caused cancer of the breast in woman produced an antigen close to, or identical with, the antigen produced by the virus causing breast cancer in mice.  It is also very similar or identical to a monkey virus which causes breast cancer in monkeys.  It is quite possible that further testing will prove breast cancer viruses in all species to be identical.



               OR FLESH

     In mice, the concentration of the cancer virus in milk is equal to that in the mammary glands itself, suggesting that the virus is multiplying rapidly during the time of milk production.  These results show that as far as viral transmission is concerned, milk is as good a source of material for cancer virus as is the blood or flesh of an animal.

     Virus-like particles are found in breast milk of other animals and humans having cancer of the breast.  A marker enzyme, RNA-dependent DNA polymerase, also called reverse transcriptase, has been found in all animal cancer-producing RNA viruses.  it has also been identified in many of the human milk viral particles and breast tissue samples of human breast cancer victims, suggesting a common origin.

Medical Tribune,  April 28, 1971

     Some portions of genetic material found in virus particles from human milk are identical to those found in known animal RNA cancer viruses.










     We live in a very unfortunate time of earth’s history.  The most desirable place to rear children is in rural areas, and a valuable method of training children to shoulder responsibility is by giving them animals to care for.  Yet at the present time the hazards of contact with animals are increasing.  There is a statistically significant association between farming and death from leukemia and multiple myeloma.  Virus particles with diameters approximately 60 to 110 mu were detected in concentrated milk from cows in a herd with a high incidence of lymphosarcoma.  Even those herds apparently lymphosarcoma-free showed virus particles in pooled tank samples of milk indicating that the absence of physical signs in the cow does not insure the milk to be free of viruses.  Although it has not yet been proven in the laboratory, leukemia in cattle is assumed by many authorities in cattle diseases to be transmitted from mother to offspring by means of colostrum and milk.  Bibliotheca Haematologica 1968  There is a need for work to be done along these lines to establish the safety (or lack of it) of milk, as milk continues to be certified to be safe for children and older people to drink.

     Two chimpanzees at the Yerkes Regional Primate Research Center of Emory University died of a type of pneumonia, rare in humans, and unknown previously in chimpanzees.  The two chimpanzees were on a special diet—milk from a herd of cows having a high incidence of lymphosarcoma, and having virus-like particles in their milk.  The researchers were trying to determine the significance of these virus-like particles revealed by electron microscopy.  The rare type of pneumonia was caused by Pneumocystis carinii, a type of pneumonia almost always associated in humans with leukemia or other malignancies, or in persons with some sort of immune deficiency.  The question is raised as to whether or not this rare type of pneumonia is acquired in humans at the same time the viral agent for leukemia and other malignancies is acquired.

     A group of researchers noted that while they were trying to produce hardening of the arteries in rats by prolonged feeding of milk and egg yolk, the rats developed tumors in various parts of the body, particularly in the liver.  It was understood by the researchers that the tumors were the result of the milk and egg diet.

     The association between farming as an occupation and leukemia has been recognized for years.  The association is strongest for men under age 60 with lymphatic and the acute types of leukemia.  Poultry farmers are especially hard-hit, having the highest proportion of excess cases as determined by a study of death certificates in Washington State.

American Journal of Epidemiology 1971


    Trends of deaths from breast cancer in the United States have been rising since 1910.  The breast cancer rates per 1000,000 in all ages, in 1911 was 7.5; in 1920 it was 8.8; in 1930, 11.2; in 1964-1965 it was 21,55.  Similarly animals have shown a great increase during the same period.  Known animal RNA breast cancer viruses are identical to certain RNA particles found in one-third of human milk samples furnishing further evidence that human and animal milk carry identical cancer viruses.  Science News, February 24, 1973

  The Milk of Leukemic cattle is a very rich source of virus particles.  “It is tempting to consider milk as a possible vehicle for the transmission of a leukemia virus...”   The  viruses are present in cattle for years before the animal develops the disease.  Cattle lymphoma is capable of spreading from one animal to another, and from one herd to another.  There is also vertical transmission from cow to calf.  In children, the age of three to four is the peak incidence of leukemia deaths; Milk-drinking is heaviest during and preceding these years.

     Other RNA viruses cause polio, colds, and influenza.  They replicate without DNA and the genetic material is translated into protein.  We agree with the researchers who say that there is unmistakable evidence that the virus RNA from human cancer is identical in the virus RNA that causes similar tumors in animals.  There may be both horizontal (person to person) and vertical (parent to child) transmission of cancer viruses.  It is easily recognized that some types of malignancies “run in the families.”  There has also been reported the phenomenon of clustering cancer cases.  This occurrence of multiple cancer cases in a small group or geographic area surely suggest a shared environment or food supply as the source of the cancer; it further strongly implicates an infectious agent as the cause of cancer, leaving little doubt that the agent is a virus.  We believe all cancers are caused by a specific viral agent regardless of  how many other factors are involved in producing the cancer.


     Tumor viruses have now been proven to cross species lines to induce tumors.  Some of this work was done early in cancer research using marmosets and hamsters.  The greater the infectious dose of both the “helper” and primary virus, the higher is the occurrence of induced cancer.  Human leukemia was transmitted to Syrian hamsters in 1967 by Dr. Sydney Farber of the Children’s Cancer Research Foundation in Boston.  Herpes simplex type II from a human genital lesion was used by Doctors Ronald Duff and Fred Rapp of the Milton Hershey Medical Center of Pennsylvania State in making animal cells cancerous.  The resulting transformed cells subsequently produced malignant tumors when injected into newborn hamsters.  Viral particles have been discovered in “normal” dogs living in direct contact with leukemic children.  Additional confirmation of cross of species lines by cancer viruses has been obtained from the Rous sarcoma virus transmission to rabbits, dogs, mice, and hamsters.  Antibiotic New April 5, 1967

     For many years, the household cat has been suspected of transmitting leukemia to humans.  Cat lymphoma is believed by some investigators to be transmitted from cat to cat, but the question arises, can the cat leukemia and lymphoma virus cause cancer in man?  Several reports have confidently declared no association between animals and human leukemia, but most of these reports were prior to 1973.  An epidemiologic study in 1973 revealed evidence that linked cases of human leukemia to contact with pets.  Investigation focused largely on pet illness or death occurring in the year before the diagnosis of leukemia; and in regard to childhood cases, pet deaths that had occurred since the child’s birth.  The association between human leukemia and cats is stronger  for ill cats, and is significant also for birds and dogs.  The relative risk increases with the age of the pet.

     Children, ages one to fourteen, have roughly double the risk of leukemia if they have been exposed at any time during their lives to a sick cat or one which died.  This finding has now been confirmed in approximately 1,400 cases.  Other animals, including ill or dead canaries, parakeets, and pet dogs, show less risk of human leukemia association than cats.  American Journal Of Public Health 1972

     Malignant lymphoma is the most common cancer in cats.  The causative virus can be grown in human cells in a test tube.  Pregnant mothers or young children in contact with cats may be far more susceptible than others in the population.  This may be an important matter in which humans, especially children, obtain leukemia or lymphoma.  Leukemic cats should not be cared for in their owner’s homes.

     Dog, cat and pig lymphomas have been shown to be of the same histologic type as human  Burkitt’s lymphoma.  Lymphomas are not uncommon in these animals, particularly dogs.  We should weigh heavily the evidence that identical structural features between animal and human cancers reflect a common agent.  Science News  February 24, 1973

A. & C. Thrash