Aedes vexans Meigen is the cause of "bug bites" that reduce the value of hog carcasses from farms in Minnesota and Iowa. This newly recognized condition has forced a slaughterhouse in Worthington, MN, to dock prices paid for affected hogs by a total of $300,000 in the last two years. Skin sections from carcass lesions were viewed with a microscope to determine that the lesions were an allergic reaction to an insect bite. Bacteria and fungi were ruled out as possible causes. Records of cases at the Worthington plant in 2000 and 2001 indicated the condition occurred in late spring and summer, when biting insects are active, but not at other times of the year. A case-control study at 24 Minnesota hog farms in summer, 2001, revealed that the vexans mosquito was abundant and biting hogs in curtain-sided barns at 22 of the farms. Counts of the mosquito in CDC traps hung overnight in the barns just before the hogs were shipped to slaughter were strongly correlated with incidence of lesions on hog carcasses from the same farms. Incidence was not related to counts of stable flies, other kinds of mosquitoes, and other non-biting insects that were also present in some of the barns.
Species 1: Diptera Culicidae Aedes vexans (vexans mosquito)
Species 2: Diptera Muscidae Stomoxys calcitrans (stable fly)
Keywords: hypersensitivity, hog carcasses
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