High morbidity cutaneous enzootic myiasis by Dermatobia hominis (Diptera: Oestridae) in sambar deer (Rusa unicolor)

This study describes the first known occurrence and treatment of enzootic cutaneous myiasis by Dermatobia hominis in a herd of sambar deer (Rusa unicolor). Sambar deer are clinically affected by enzootic cutaneous myiasis during the spring and summer in Rio de Janeiro, Brazil. Through direct inspection and clinicopathological evaluation in the herd with 80 R. unicolor, it was observed that infestation by D. hominis caused 100% morbidity. At histological exam, skin had eosinophilic and granulomatous chronic active severe necrohemorrhagic dermatitis associated with botfly and moderate surrounding fibroplasia. The systemic treatment with oral ivermectin at 0.08% was effective in 93.7% of deer with enzootic cutaneous myiasis after fourteen days. After treatment, the skin deer had eosinophilic and granulomatous chronic severe dermatitis associated with degenerated botfly and severe fibroplasia. Notable differences in leukocyte profile were observed between groups pre- and post-treatment. Decrease of relative values of neutrophils and eosinophils were significant in the treated deer group. An increase of relative values of monocytes was also confirmed in the treated group. Sambar deer was the only species affected by D. hominis, even though several other wild herbivores were kept in the same area. More studies are needed to elucidate the susceptibility of R. unicolor to D. hominis cutaneous infestations.