The modes of stylostome formation by larvae (chiggers) of Leptotrombidium intermedium, L. fletcheri, L. arenicola, and L. deliense in parasitized mouse skin were studied histologically in relation to their capacity to transmit Rickettsia tsutsugamushi. Three types of stylostome formation were recognized among the different species: the epidermal stylostome formed by the larva of L. intermedium; the mesenchymal stylostome formed by the larva of L. fletcheri; and, the mixed stylostome formed by the larva of both L. arenicola and L. deliense. Dermal inflammations related to the three types of stylostomes were histologically defined. The possible importance of stylostome characteristics to the transmission of rickettsial organisms is discussed.
We describe a patient with cutaneous myiasis caused by the African tumbu fly (Cordylobia anthropophaga). This case demonstrates the need for a detailed travel history and an understanding of the fly life cycle to prevent erroneous diagnosis and to expedite prompt treatment. The nature of the lesions, larval morphological features, histological characteristics, and immune response directed toward fly maggots are described.
Deet, the lactone CIC-4, and the piperidine compounds A13-37220 and A13-35765 were evaluated for initial repellency against laboratory-reared Anopheles albimanus Wiedemann, An. freeborni Aitken, An. gambiae Giles, An. stephensi Liston, and Phlebotomus papatasi (Scopoli) using a dose-response testing procedure on human volunteers. In addition, deet and CIC-4 were tested against Lutzomyia longipalpis (Lutz & Neiva). In general, the repellency of A13-37220, A13-35765, and CIC-4 was not markedly different from that of deet against each species tested; however, the different species varied greatly in response to the repellents. Overall, An. stephensi, L. longipalpis, and P. papatasi were the most sensitive, and An. albimanus the most tolerant species. The four repellents subsequently were tested against An. stephensi and An. albimanus to determine the duration of repellency. AI3-37220 provided effective (> 90%) protection against An. stephensi bites for 7 h, whereas deet, AI3-35765, and CIC-4 provided 6, 5, and 3 h of protection, respectively. Each of the four compounds provided < 1 h of protection against An. albimanus bites.
Five repellents were evaluated against Anopheles albimanus Wiedemann An. freeborni Aitken, An. gambiae Giles, and An. stephensi Liston, using a "free choice," dose-response testing procedure on rabbits. Overall, deet was the most effective repellent based on effective dosages (ED50's and ED95's), except against An. albimanus. An. albimanus was significantly more tolerant to deet compared with dimethyl phthalate or ethyl hexanediol. Permethrin was effective against all four anopheline species at the ED50 levels; however, the ED95 values were higher compared with the other repellents. There were significant differences in sensitivity of some of the four species to all the repellents tested, except dimethyl phthalate and indalone. The variability in the response of these anopheline species to repellents confirm that the extrapolation of repellent data from one anopheline species to another is unreliable and that comprehensive tests are needed for each species.
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