Surveys of Canine Filarioids In Nigeria: The Path Travelled and the Way Forward

Filarioid worms infecting dogs have recently received increased attention globally because of their zoonotic potential. In Africa and, particularly, in Nigeria, however, where there is preponderance of the risk factors for vector-borne diseases transmission, there are few reports of the disease in the canid and felid definitive hosts, the wild/domestic reservoirs and humans. Thus, the epidemiology of the disease in Nigeria remains sketchy and needs to be investigated. A retrospective analysis of reported canine filarioids in Nigeria was undertaken with the view to highlight what has been done and reported, existing gaps in knowledge, what needs to be done to bridge the gap and possibly how it could be done. Thirteen published works on canine filarioids using classical laboratory methods in Nigeria, reported the finding of Dirofilaria immitis (0.4–15.1%), Dirofilaria repens (0.1–9.4%), Acanthocheilonema reconditum (0.4–9.2%) and a case of A. dracunculoides in an unspecified dog population. In most instances, the species identification of the filarioids reported was not conclusive due to limitation of the diagnostic methods employed. No human infection due to any zoonotic canine filarioid has been reported in Nigeria. Suggestions for prospective filarioids research in Nigeria were made. Keywords: Filarioids, dog, zoonosis, diagnosis, Nigeria

Molecular Approach for the Diagnosis of Blood and Skin Canine Filarioids

The zoonotic Onchocerca lupi and tick-transmitted filarioids of the genus Cercopithifilaria remain less well known due to the difficulties in accessing to skin samples as target tissues. Here, we proposed a molecular approach reliying on multiplex qPCR assays that allow the rapid identification of filarioids from canine blood, skin, and tick samples. This includes two newly developed duplex qPCR tests, the first one targeting filarial and C. grassii DNA (CanFil-C. grassii). and the second qPCR assay designed for the detection of Cercopithifilaria bainae and Cercopithifilaria sp. II DNAs (C. bainae-C.spII). The third one is a triplex TaqMan cox 1 assay targeting DNA of blood microfilariae (e.g., Dirofilaria immitis, Dirofilaria repens and Acanthocheilonema reconditum). The novel duplex qPCRs developed were validated in silico and by screening of known DNA collection. The qPCR assays were also used for screening the blood and tick samples of 72 dogs from Algeria. This allowed the identification of canine filariasis infection with 100% of specificity and 89.47% and 100% of sensitivity from naturally infected blood and tick samples, respectively. The prevalences of 26.39% for D. immitis and 5.56% for both D. repens and A. reconditum were reported in blood and tick samples. Cercopithifilaria DNAs were detected only in tick samples, with a prevalence of 4.17% and 5.56% for C. bainae and Cercopithifilaria sp. II, respectively. Co-infections were diagnosed in 6.94% and 13.89% of blood and tick samples, respectively. Whereas all samples were negative for C. grassii DNA. The use of engorged ticks instead of blood and skin samples could be an easier option for the surveillance of all canine filarioids herein investigated. The multiplex qPCR assays herein validated were shown to be useful in the detection of filarial co-infections by overcoming sequencing of positive samples.