Serological studies of normal and leukemic cats in a multiple-case leukemia cluster.

Eleven cases of lymphoblastic leukemia and four cases of feline infectious peritonitis occurred in a private household population of 35 predominantly unrelated cats over a 39month period. The study conducted on this population con sisted of periodic physical examinations, hemograms, serological testing for feline leukemia virus group-specific antigens (gs) and for antibody to feline oncornavirus-associated cell membrane antigen (FOCMA). Serological values were compared to those for healthy and leukemic control cats from the same geographical area. Leukemic household cats had a higher mean age and had been in the household longer than those that remained healthy. Six of 9 leukemic cats were positive for FeLV (as were 9 of 10 leukemic cats living in other environments). Both the control and cluster household leukemic cats also had low geometric mean antibody titers to the FOCMA antigen (0.72 and 0.76, respectively). This differed from healthy controls from outside the house that were all nega tive for gs antigens and had a mean antibody titer of 1.66. For healthy controls within the house, the mean antibody titer was 4.65 and 5 of 17 were positive for gs antigens. This difference is apparently due to more frequent or more recent exposure to virus in the cluster household. Relatives of leu kemic cats were no more likely to develop leukemia or be come gs positive than relatives of healthy cats. Cats de veloping leukemia appear to be unable to produce or maintain a high FOCMA antibody titer. It was concluded that these data support the theory of horizontal transmis sion of feline leukemia virus.