Detection and molecular characterisation of Ehrlichia canis in naturally infected dogs in South West Nigeria.

Canine ehrlichiosis is an important tick-borne rickettsial disease mainly caused by Ehrlichia canis. This study aimed to detect and characterise E. canis in dogs in Abeokuta, Nigeria by microscopy and nested PCR. Blood samples were collected from 205 dogs, thin smears were made, field-stained, and DNA was extracted from the blood samples. A partial region of the 16S rRNA gene was amplified by polymerase chain reaction (PCR) and sequenced unidirectionally. Ehrlichial morulae were detected in three dogs (1.5%). The PCR test revealed that 47 dogs (22.9%) were positive for E. canis. The lengths of the sequences obtained range from 374 bp to 376 bp with an average G-C content of 37% and 98-99% homology with the reference sequences in GenBank. The aligned autochthonous sequences were less polymorphic. The phylogenetic analysis separated sequences reported previously in Nigeria from the autochthonous sequences. The present work shows that the strain of E. canis detected in the study area is genetically different from those reported in the northern part of Nigeria and more closely related to sequences from Brazil and India.