Immune Carrier State of Feline Panleukopenia Virus-Infected Cats

SUMMARY Persistence of feline panleukopenia (fpl) serum-neutralizing (sn) antibody titers resulting from naturally occurring infections was examined in 6 cats kept in Horsfall isolation units and in 4 cats housed in a closed colony. Titers remained constant as long as 47 weeks and 99 weeks, respectively. Panleukopenia virus was isolated from urine of inoculated cats as long as 20 to 22 days and from feces of the same cats as long as 41 to 43 days after inoculation in secondary feline kidney (fk) cell cultures. With the same cell culture technique, viral isolation was unsuccessful from tissues of cats after postinoculation day (pid) 22. The fpl viral persistence was demonstrated by direct monolayer cultures prepared from cats which had recovered from experimental or naturally occurring infections. Kidneys and lungs of experimental cats were shown to contain virus as long as pid 70. By the latter technique, fpl virus was isolated in kidneys of 5 of 8 cats, in lungs of 2 of 8 cats, and in the intestine of 1 of 5 cats that ranged in ages between 4 and 156 weeks and had had ataxia since birth.