deerfly
Summary
The deerfly (Chrysops species) is a biting fly that transmits Francisella tularensis, the agent of tularaemia, and Loa loa, the African eye worm. Deerfly bite is one of several routes by which tularaemia is acquired.
Detail
For tularaemia the deerfly is one vector among several: the Dermacentor and Amblyomma ticks, direct handling of infected rabbit carcasses (hence 'rabbit fever'), inhalation of aerosols during lawn mowing over animal remains, and ingestion of contaminated water. Ulceroglandular tularaemia is the commonest form, with a punched-out ulcer at the bite site and tender regional lymphadenopathy; F. tularensis is a highly infectious intracellular gram-negative coccobacillus requiring cysteine-enriched media, a category A bioterrorism agent, treated with streptomycin or gentamicin. Separately, Chrysops is the daytime-biting vector of Loa loa in West and Central African rainforest, where the adult worm migrates through subcutaneous tissue and characteristically crosses the conjunctiva visibly, with transient Calabar swellings and marked eosinophilia. Diethylcarbamazine treats loiasis but must be preceded by assessment of microfilarial load because rapid killing can precipitate fatal encephalopathy, and ivermectin carries the same risk in co-infection with onchocerciasis.
Sources
- Levinson Medical Microbiology and Immunology
- First Aid for the USMLE Step 1
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