Serological and demographic evidence for domestic dogs as a source of canine distemper virus infection for Serengeti wildlife.

Following an epidemic of canine distemper virus (CDV) in Serengeti lions in 1994, the role of domestic dogs in the epidemiology of the disease was investigated by serological and demographic analyses. From 1992 to 1994, data were collected from two domestic dog populations bordering the Serengeti National Park. Several lines of evidence indicated that patterns of CDV infection differed significantly between higher-density dog populations of Serengeti District to the west of the park and lower-density populations of Ngorongoro District to the south-east: (a) CDV age-seroprevalence patterns differed significantly between years in Ngorongoro District populations but not in Serengeti District populations; (b) CDV seropositive pups (<12 months of age) were detected in Ngorongoro District only in 1994, whereas a proportion of pups in Serengeti District were seropositive in each year of the study; (c) in Ngorongoro District, the proportion of deaths attributed to disease was significantly higher in 1994 than in 1993, whereas in Serengeti District, there was no significant difference in disease-related mortality between years; (d) in Ngorongoro District, significantly more CDV seronegative dogs than seropositive dogs died in 1994, whereas there was no difference in survival of CDV seropositives and seronegatives between years in Serengeti District. We concluded that, between 1992 and 1994, CDV persisted in higher-density dog populations of Serengeti District, but occurred only sporadically in lower-density Ngorongoro District populations. Data from Ngorongoro District are consistent with exposure of dogs to CDV in 1991 and 1994, but not in 1992 and 1993. These findings suggest that higher-density domestic dog populations to the west of the Serengeti National Park were a more likely source of CDV infection for wildlife during 1994 than lower-density pastoralist dogs to the south and east of the park.