An annotated checklist of tick-borne pathogens of dogs in Nigeria

Tick-borne pathogens are transmitted by the bite of a tick vector or the ingestion therein by a susceptible host. Conventionally, the diagnosis of tick-borne parasites in Nigeria is achieved through the demonstration of their developmental stages in the host's blood or tissues. These classical methods are limited in their capability to detect chronic cases or healthy carriers and to differentiate between pathogens of similar morphological features. Molecular diagnostic techniques of high sensitivity have been developed to overcome these shortfalls by detecting the pathogen's DNA, elucidating their genetic makeup and comparing their phylogenetic relationship to other pathogens, sometimes necessitating taxonomic changes. Detection of DNA of canine tick-borne pathogens (CTBPs) such as Ehrlichia canis, Hepatozoon canis, and Mycoplasma haemocanis has been reported in Nigerian dogs corroborating earlier microscopic findings. Furthermore, DNA of Anaplasma platys, Ehrlichia ewingii, ‘Candidatus Mycoplasma haemobos’ and Theileria sp. hitherto considered to be absent in Nigeria has been detected, thereby expanding the spectrum of CTBPs in the country. However, in some cases, diagnoses based on the detection of single short DNA fragments from pathogens can cause considerable confusion. This occurred in the case of the large canine Babesia, previously referred to as Babesia canis which has been reported in Nigerian dogs. There appears to be confusion regarding the accurate status of this pathogen in Nigeria due to the subsequent classification into Babesia canis, Babesia vogeli and Babesia rossi. Moreover, several molecular studies failed to detect the DNA of Babesia gibsoni previously reported in Nigerian dogs by light microscope. These findings necessitate regular update of the list of CTBPs of veterinary and medical importance, in order to keep practitioners abreast with these changes. Herein, an annotated checklist of tick-borne pathogens of dogs in Nigeria, based on available data from both classical and molecular studies, with notes explaining any discrepancies between the methods and probable explanations thereof, is presented.