Clinical observations of Babesia gibsoni infection with low parasitaemia confirmed by PCR in dogs.

摘要

This short communication describes a case series in which clinical data from dogs with acute Babesia gibsoni infection demonstrating low parasitaemia and confirmed by PCR were evaluated and compared retrospectively with dogs with apparent B. gibsoni infection or immune-mediated haemolytic anaemia (IHMA). A total of 35 dogs with acute B. gibsoni infection and 8 with IMHA, treated between 1998 and 2003 at the Veterinary Teaching Hospital, Yamaguchi University, Japan, were included in the study. Twenty-five of the 35 dogs were diagnosed with B. gibsoni infection by the demonstration of the parasites in blood smears. In the 10 remaining dogs, no parasites were detected in the blood smear, but positive reactions to diminazene aceturate, or the appearance of Babesia sp. parasites in blood films after the dog has been treated with immunosuppressive drugs, later caused these 10 dogs to be diagnosed with B. gibsoni infection with low parasitaemia. The information obtained for the 35 babesiosis cases and 8 IMHA cases included histories and the findings of physical examination, complete blood counts, serum biochemical analysis and abdominal radiography. To compare the data from the dogs with low parasitaemia with those with moderate to severe parasitaemia or with IHMA cases, chi-squared tests and one-way analysis of variance were performed. No significant differences were observed upon comparison of the clinical and laboratory findings of the Babesia-infected animals with low parasitaemia and dogs with moderate to severe parasitaemia. However, comparison of the results of clinical and laboratory findings in dogs with low parasitaemia and dogs suffering from IMHA showed more severe clinical signs in dogs with IMHA than those with B. gibsoni infection. The mean erythrocyte count, haematocrit and haemoglobin value in the dogs with IMHA were slightly lower than those in the B. gibsoni-infected dogs, but these differences were not significant. Most of the dogs with IMHA were also positive by direct Coomb's test, showing significant numbers of spherocytes in blood smears; however, these results were also found in some dogs with B. gibsoni infection. Thus, if there are no evidence of Babesia sp. parasites in blood smears, it is very difficult for veterinarians to confirm B. gibsoni infection and differentiate it from IMHA on clinical grounds. In conclusion, the B. gibsoni-specific PCR will be a highly useful tool for the diagnosis of acute B. gibsoni infection in dogs.