Pathological findings of cutaneous periocular habronemiasis in a horse in Egypt

[Abstract] A 14 years old horse was admitted in June 2014 with an unhealed ulcer near to the medial canthus of the left eye. The ulcerated skin lesion was 3 cm in diameter reddish in color with hazy irregular borders and containing grayish and yellowish necrotic tissues with offensive odor. Histopathological examination of tissue sections showed parasitic elements embedded in multiple granulomas with caseated centers with degenerated habronema larvae containing masses from granulated eosinophil in the center followed by eosinophilic and basophilic necrotic debris beside numerous macrophage and giant cells followed by fibrous capsule. The covering skin revealed large deep cutaneous ulcer containing purulent or serous exudate with living and degenerated neutrophils. The inflammatory process was extended into deeper area forming pyogranuloma containing multinucleated giant cells and fibrous tissues. Alsothe adjacent tissues revealed aggregations of microfilaria in dermis (Onchocerciasis), and in other section from behind the granuloma we saw nonseptated mycelium (Cutaneous Phaeohyphomycosis) within the purulent exudate as an opportunistic infection. It could be concluded that complicated cutaneous Habronemiasis consider one of the parasitic cutaneous lesions which is rare among horses in Egypt. Immunological reactions of the parasitic element may be one of the etiological agents of skin ulcers and fungal invasions.