Anaplasma phagocytophilum infection in thrombocytopenic dogs

Anaplasma and Ehrlichia spp. are tick-transmitted bacteria of clinical relevance in European dogs. The diagnosis of infection is often difficult due to the wide spectrum of disease caused by them. During infection, reduction in platelet count is considered the most common haematological abnormality, frequently representing the sole alteration in asymptomatic dogs. In this study, the presence of bacteria belonging to the genera Anaplasma and Ehrlichia was investigated in Northern Italy in blood samples from 159 thrombocytopenic dogs using a polymerase chain reaction (PCR) assay amplifying a portion of the heat shock gene (groEL). Obtained amplicons were sequenced and analysed. Two dogs were positive for A. phagocytophilum, while A. platys and E. canis were not detected. None of the PCR-positive dogs were diagnosed at the time of hospital admission, even in the presence of clinical signs and clinicopathological abnormalities potentially related to A. phagocytophilum infection. Nucleotide sequence analysis showed that the 2 detected strains belonged to the cluster Europe 1 and were different from each other. This study confirms the presence of A. phagocytophilum infections in dogs of Northern Italy, causing clinical signs and laboratory abnormalities that could not be properly diagnosed and treated.