EOSINOPHILIC MEDIASTINITIS, MYOSITIS, PLEURITIS, AND PNEUMONIA OF CATTLE ASSOCIATED WITH MIGRATION OF 1ST-INSTAR LARVAE OF HYPODERMA-LINEATUM

Migrating first-instar larvae of Hypoderma lineatum are a frequent cau se of focal inflammatory lesions in connective tissues of the mediasti num, parietal and visceral pleura, peritoneum, lungs, diaphragm, and o ther loci. The lesions are characterized grossly by foci of yellowish or greenish gelatinous edema and microscopically by infiltration of th e edematous tissue by a dense array of eosinophils. Lesions were recog nized during a period of several weeks in late spring; the timing was attributable to events in the life cycle of the fly. The larvae, which were small (almost-equal-to 1 x 4.5 mm), transparent, and unobtrusive , were recovered from lesions in 12 of 20 cattle in which careful para sitologic examination was made.