Etiology, Prevalence, Risk Factors and Pathological Lesions Associated With Canine Cutaneous Myiasis in Kitui County, Kenya

Abstract

A cross-sectional study of canine cutaneous myiasis (CCM) was conducted from March to August, 2021 in eight sub-counties of Kitui County, Kenya. The aim of the study was to determine the etiology, prevalence, risk factors and pathological lesions associated with canine cutaneous myiasis in dogs. Face to face questionnaire interviews were conducted for assessment of risk factors that determine the occurrence of canine cutaneous myiasis in the study area. A total of 400 dogs were physically examined for the presence of skin lesions characteristic of canine cutaneous myiasis. At least two larvae were collected from each dog by application of digital pressure at the base of the lesions. The fly larvae causing CCM were preserved in 70% ethyl alcohol, transported to laboratory where they were processed, characterized and identified. From 400 dogs sampled, 180 (45%) had furuncular skin lesions due to third stage larvae of myiasis causing flies. These furuncles were concentrated on the ventral parts of the body of the dogs. Two cases of cutaneous myiasis in goats were also encountered during the study. Intensity of infestation was 434 and 6 dipteran maggots from dogs and goats, respectively. All dipteran larvae samples (440) were identified as Cordylobia anthropophaga fly larvae (100%). Freshly harvested C. anthropophaga larvae were cultured for four weeks and adult “tumbu” flies hatched, captured and identified. Analysis of questionnaires using chi-square revealed that there was a statistically significant association among different dog breeds, housing structures, their hygiene measures and environmental hygiene (p˂0.05) and myiasis. However, there was no statistically significant differences in the prevalence of canine cutaneous myiasis among different dog age and sex groups (p>0.05). Complete canine necropsy examination was conducted in four dogs purchased with severe canine cutaneous myiasis infestation from Kitui County. Grossly there were multifocal furuncular skin lesions extending throughout the thickness of the skin epidermis to the dermis. xix The skin lesions were characterized by thick, firm consistency, cutaneous edema and congestion. Some of these had live maggots. The underlying skeletal muscles were bright red due to hyperemia. There was regional lymphadenopathy in affected body regions. Microscopically, there was disruption, discontinuity and desquamation of the stratified squamous epithelium of stratum corneum of the skin which were the entry points for the C. anthropophaga larvae into the dogs` skin. There were circular cavities surrounded by a fibrous capsule, mixed inflammatory cells infiltrate with predominant eosinophils. Underlying skeletal muscles had coagulative necrosis, proliferation of fibroblasts and deposition of eosinophilic collagen fibres and infiltration of mixed inflammatory cells. During necropsy, various ectoparasites and endoparasites were recovered and included ticks, fleas, tapeworms and nematodes, an indication of poor dog management practices in the area. In conclusion, C. anthropophaga larvae of tumbu fly were the etiological agent associated with canine cutaneous myiasis, that was predisposed by poor housing and hygiene and had high occurrence and caused furuncular lesions in animals in Kitui County, Kenya. More studies on seasonal prevalence, distribution in various counties, etiological survival limits, public health importance and control strategies of CCM in the country are recommended.