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Title: Papular dermatitis induced in guinea pigs by the biting midge Culicoides sonorensis (Diptera: Ceratopogonidae)

Author
item O'TOOLE, DONAL - UNIVERSITY OF WYOMING
item Perez De Leon, Adalberto - Beto
item HEARNE, CAROL - UNIVERSITY OF WYOMING
item McHolland, Linda
item Yun, Limei
item Tabachnick, Walter

Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2002
Publication Date: 1/15/2003
Citation: O'Toole, D., Perez De Leon, A.A., Hearne, C., Mcholland, L.E., Yun, L., Tabachnick, W.J. 2003. Papular dermatitis induced in guinea pigs by the biting midge Culicoides sonorensis (Diptera: Ceratopogonidae). Journal of Veterinary Diagnostic Investigation. 15:67-71.

Interpretive Summary: When female biting midges (No-see-ums) take a blood meal, they use a sawing action to sever the skin blood vessels with cutting mouthparts to create a pool of blood from which to feed. In the process they secrete saliva containing anticoagulants and other pharmacologically active compounds into the skin of the host. After repeated exposure to midge bites, a delayed hypersensitivity dermatitis (allergy induced rash) has been reported to occur in mammalian species, particularly horses. Little, however, is known about the changes that occur in the skin of animals that have not been exposed previously to midge bites. Studies were initiated to characterize the skin response in naive guinea pigs. Immediately after insect feeding, small crateriform ulcers with necrosis developed at the feeding sites which healed within 24-48 hours. Five days later, the animals developed papular dermatitis at the feeding sites. The papules persisted until the termination of the experiment at 12 days. The focal necrosis present after the initial feeding was suggestive of the presence of a cytotoxic compound in the midge saliva. The dermatitis present after 5 days was not characteristic of a hypersensitivity type reaction. It may represent a host reaction to persisting insect salivary components and should be considered as an additional consequence of midge blood feeding in future studies.

Technical Abstract: Histological, ultrastructural, and virological examinations were performed on abdominal skin from guinea pigs after a blood meal by colony-bred biting midges, Culicoides sonorensis. Small, superficial, cutaneous, crateriform ulcers with necrosis of superficial dermis developed at feeding sites and healed within 24-48 hours. Animals developed nonpruritic erythematous papules 5 days after feeding that persisted until the study ended at 12 days after feeding. Papules corresponded histologically to foci of epidermal hyperplasia and superficial interstitial dermatitis with intraepidermal micropustules and scattered intraepidermal polykaryons. The principal ultrastructural changes were spongiosis in germinal epithelium and neutrophilic-histiocytic exocytosis. No viral agents or broken mouthparts were identified in lesions. The dermatitis may represent a host reaction to persisting insect salivary secretion and should be considered as an additional consequence of blood feeding in future studies involving biting midges.