The presence of leukaemia (lymphosarcoma) and feline leukaemia virus (FeLV) in cats in The Netherlands

ABSTRACT To study the presence and spread of feline leukaemia virus (FeLV) in The Netherlands, seven different groups of cats were examined. The indirect fluorescent antibody (IFA) test was used to detect FeLV‐antigen in blood smears. Of cats with lymphosarcoma/leukaemia 73.2% were positive and 32.4% with infectious peritonitis were positive. Only one of sixty‐six cats with other tumours–a cat with mammary carcinoma–was positive. Forty‐two (7.5%) of 557 cats with various complaints were positive for FeLV‐antigen. The IFA‐test appeared to be an important diagnostic supplement. Of all stud males which had had contact with FeLV‐positive cats 24.7% were positive for FeLV‐antigen, whereas all stud males which had not had this contact, were negative. There was a distinct difference between the percentages of FeLV‐positive individuals in the groups of cats which had had (20.6%) and which had not had (0.4%) contact with FeLV‐positive cats. From the follow‐up study it was found that 67.3% of the FeLV‐positive cats died from, or were destroyed because of, FeLV‐associated diseases within a period of 20 months.