Veterinary Parasitology: Regional Studies and Reports 15 (2019) 100255 Contents lists available at ScienceDirect Veterinary Parasitology: Regional Studies and Reports journal homepage: www.elsevier.com/locate/vprsr Review An annotated checklist of tick-borne pathogens of dogs in Nigeria T ⁎ Joshua Kamania, , Gad Banethb, Shimon Harrusb a Parasitology Division, National Veterinary Research Institute (NVRI), PMB 01 Vom, Plateau State, Nigeria b Koret School of Veterinary Medicine, The Hebrew University of Jerusalem, Rehovot, Israel ARTICLE INFO ABSTRACT Keywords: Tick-borne pathogens are transmitted by the bite of a tick vector or the ingestion therein by a susceptible host. Tick-borne pathogens Conventionally, the diagnosis of tick-borne parasites in Nigeria is achieved through the demonstration of their Checklist developmental stages in the host's blood or tissues. These classical methods are limited in their capability to Diagnosis detect chronic cases or healthy carriers and to differentiate between pathogens of similar morphological features. Dogs Molecular diagnostic techniques of high sensitivity have been developed to overcome these shortfalls by de- Nigeria tecting 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 pa- thogens 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 CTBPsof veterinary and medical importance, in order to keep practitioners abreast with these changes. Herein, an an- notated 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. 1. Introduction degree of host specificity, and therefore considered not to infect dogs, were amplified from blood samples of dogs from Nigeria (Adamu et al., Tick-borne pathogens and their consequences on the wellbeing of 2014). On the other hand, molecular methods failed to detect other dogs in Nigeria have been reported since the 1970s (Oduye and pathogens such as Babesia gibsoni (Sasaki et al., 2007; Kamani et al., Dipeolu, 1976; Aliu et al., 1976; Idowu et al., 1977). These reports were 2010, 2013a; Adamu et al., 2014; Happi et al., 2018) described earlier based mainly on the detection of the pathogens in the host's blood and by light microscopy in Nigerian dogs (Aliu et al., 1976; Ezeokoli et al., tissues using classical methods until recently when molecular methods 1983). Although the molecular methods are highly sensitive and results were employed (Sasaki et al., 2007; Kamani et al., 2010, 2013a, 2013b; generated appear to be reliable, the cost implication precludes their Adamu et al., 2014; Happi et al., 2018). Results from the molecular general use in most developing countries like Nigeria. Hence, classical studies, however not only confirmed the presence of some of the earlier methods are routinely used for most diagnostic purposes, being com- reported pathogens but also detected some species, such as, Anaplasma plimented in some instances with molecular techniques for research platys and ‘Candidatus Mycoplasma haemobos’ hitherto considered ab- investigations. The concurrent use of classical and molecular methods, sent in Nigeria (Kamani et al., 2013a; Happi et al., 2018). Furthermore, where indicated, seems to be the optimal diagnostic option. By mole- DNA attributed to some pathogens such as Theileria equi, Theileria sp. cular methods the list of canine tick-borne pathogens (CTBPs) in Ni- (sable), and Ehrlichia ruminantium generally known to exhibit a high geria is likely to increase. However, caution should be exercised in the ⁎ Corresponding author. E-mail address: [email protected] (J. Kamani). https://doi.org/10.1016/j.vprsr.2018.12.001 Received 21 October 2018; Received in revised form 2 December 2018; Accepted 2 December 2018 Available online 03 December 2018 2405-9390/ © 2018 Elsevier B.V. All rights reserved. J. Kamani et al. Veterinary Parasitology: Regional Studies and Reports 15 (2019) 100255 interpretation and drawing of conclusions based on preliminary results et al., 1999). obtained solely by molecular methods (Uilenberg et al., 2018). One way Status in Nigeria to guide the research community in this matter is to compile up to date Ehrlichia ewingii was detected by light microscopy as a co-infecting information on the diversity of CTBPs in Nigeria, which is the aim of agent with other tick-borne pathogens in dogs in Ibadan Nigeria (Happi this article. and Anita, 2012). This was the first and only report of this pathogen in dogs from Nigeria. Although not each morula of Ehrlichia (or Ana- 2. Materials and methods plasma) seen in granulocytes is necessarily E. ewingii, it should be noted that it could also be A. phagocytophilum. Thus, molecular confirmation A checklist of tick-borne pathogens of dogs in Nigeria was compiled (by PCR and sequencing) is required to validate this finding, con- based on the examination of published literature for the years sidering limitations of the method used as well as epidemiological 1970–2018. To ensure the broadest possible coverage of scientific lit- factors involved in the transmission of this pathogen. Interestingly, erature, searches were conducted in the following online databases: DNA of E. ewingii has been reported in dogs from Cameroon (Ndip et al., PubMed, CabDirect, Web of Science (WoS) and African Journals Online 2005), a neighboring country to Nigeria, suggesting that the detected (AJOL), using the following keywords; blood, parasites, dog, tick-borne organism was indeed E. ewingii. and Nigeria. Genus: Anaplasma A list of pathogens was retrieved following careful evaluation of the Anaplasma platys information and the diagnostic methods applied. In addition, ex- Anaplasma platys (formerly, Ehrlichia platys) was first described in planatory notes highlighting key points for each pathogen listed were dogs from Florida, United States of America (Harvey et al., 1978). It is provided. an obligatory intracellular bacterium that infects platelets (Fig. 2) and causes canine infectious cyclic thrombocytopenia. Anaplasma platys 3. Checklist of tick-borne pathogens of dogs in Nigeria infection was originally considered to be subclinical (Harvey et al., 1978). However, there are reports of more virulent strains of this agent Several tick-borne pathogens of dogs have been reported in Nigeria. in several countries of the Mediterranean basin suggesting it can cause Their presence has been demonstrated either through the detection of signs similar to those caused by E. canis however with lower severity. developmental stage(s) in the blood of dogs by light microscopy or by The disease is characterized by cyclic thrombocytopenia (Walker et al., the detection of their DNA using PCR and sequencing methods 1970; Harrus et al., 1997; Aguirre et al., 2006). Although a single report (Table 1). associated A. platys with a disease in 2 women from Venezuela (Arraga- Phylum: Proteobacteria Alvarado et al., 2014), A. platys is not considered to be pathogenic to Class: Alphaproteobacteria humans. Order: Rickettsiales Status in Nigeria Family: Anaplasmataceae There are a few reports of A. platys infection in dogs from Nigeria. Genus: Ehrlichia Happi and Anita, (2012) using light microscopy, detected A. platys in Ehrlichia canis co-infection with Hepatozoon canis in one dog. Additionally, the DNA of Ehrlichia canis, the agent of canine monocytic ehrlichiosis was first A. platys was detected in Nigerian dogs (Kamani et al., 2013a). These identified in dogs in Algeria (Donatien and Lestoquard, 1935). The findings suggest that the bacterium might have been long infecting dogs organism (Fig. 1) has special tropism for monocytes and macrophages, in Nigeria, but has been overlooked or misdiagnosed during micro- appearing in the form of morulae within the cytoplasm of the latter cells scopic examination of blood smears. Microscopists and diagnosticians (Huxsoll et al., 1970). Canine monocytic ehrlichiosis is a multisystemic in Nigeria should pay particular attention to typical A. platys inclusions disease manifesting itself in acute, subclinical or chronic forms. The in the form of morulae within platelets during evaluation of blood clinical signs vary greatly, ranging from silent infection to severe clin- smears for the presence of haemoparasites. Preparation and examina- ical disease, characterized by depression, lethargy, anorexia, fever, tion of