New records of phlebotomine sand flies (Diptera: Psychodidae) from Ecuador

The plebotomine sand fly fauna of Ecuador was surveyed in two 3-month collecting trips made in 1988 and 1990. A total of 12 provinces were visited, including three (Bolivar, Loja and Morona Santiago) from wich no previous records to phlebotomines existed. Forty-six species were collected, 13 of wich, together with 1 subspecies and 1 genus (Warileya) represented new records for the country. This survey increases the known number of species in Ecuador to 60. The distribuition of Ecuadorian sand flies is discussed in the light of these new findings

Andean leishmaniasis in Ecuador caused by infection with Leishmania mexicana and L. major-like parasites.

Between 1986 and 1988, epidemiologic studies were carried out in a small rural community in an Andean region of Ecuador, where cutaneous leishmaniasis is highly endemic. A total of 25 human cases, positive for Leishmania parasites by culture and/or smear, were examined. Fourteen of the cases were in infants less than one year of age, suggesting intradomiciliary transmission of the disease. Clinically, many of these cases were similar to descriptions of "uta," a form of cutaneous leishmaniasis which occurs in Andean regions of Peru and is reported caused by L. peruviana. Of the 11 positive cultures obtained from human cases in the present study, eight were identified by molecular characterization as L. mexicana and three were identified as L. major-like. Two additional isolates of L. mexicana were also made from an infected dog and from a sand fly, Lutzomyia ayacuchensis, living in the region, thus implicating the latter species as possible reservoir and vector, respectively, of L. mexicana in this highland community. The significance and validity of recent isolates of L. major-like parasites from the New World are also discussed.

Natural infections with Leishmania promastigotes in Lutzomyia ayacuchensis (Diptera: Psychodidae) in an Andean focus of Ecuador.

In the Andean town of Paute, Ecuador, 2 of 97 (2%) Lutzomyia ayacuchensis Cáceres and Bianchi were found to be naturally infected with Leishmania promastigotes. The parasites were confined to the midgut of the sand fly, indicating they did not belong to the subgenus Leishmania (Viannia).

The vectoral role of several blackfly species (Diptera: Simuliidae) in relation to human onchocerciasis in the Sierra Parima and Upper Orinoco regions of Venezuela.

Experimental and natural infections with Onchocerca volvulus were studied in several anthropophilic blackfly species present in the endemic area of the Upper Orinoco region of Venezuela. When fed on four different Yanomami volunteers in the Sierra Parima, the total infection rate was 31.4% for Simulium guianense in comparison with 7.5% for S. limbatum. The proportion of ingested microfilariae that entered the thorax during the first 24 hours and completed development to the infective stage was also much lower in the latter than in the former species. There was no larval development of O. volvulus in S. antillarum, but one female harboured in its head six infective larvae of a zoonotic filaria. When S. oyapokense s.l. was fed on an infected volunteer in the Upper Orinoco most flies ingested few microfilariae, and further development reached only the L1 stage. Natural infection and infectivity rates for S. guianense in two localities of the Sierra Parima were 0.2-4.0% and 1.3-10.2%, respectively, more than 50% of the L3 larvae being in the head. The corresponding data for S. oyapockense s.l. in the Upper Orinoco were 0.1-0.5%, although the only L3 larva found did not correspond to O. volvulus. It is suggested that S. guianense is the main vector of onchocerciasis in the Sierra Parima and that S. limbatum could play a secondary role. Simulium oyapockense s.l. replaces them in the Upper Orinoco and may maintain a degree of transmission, but its epidemiological importance remains to be assessed.

Development of Onchocerca volvulus larvae in Simulium pintoi in the Amazonas region of Venezuela.

The intake and development of Onchocerca volvulus in Simulium pintoi from the Parima mountain region of the Federal Territory of Amazonas in Venezuela, were studied experimentally. When wild females fed on the lower half of the legs and lower third of the back of an onchocerciasis patient harboring 23 and 264 microfilariae per skin snip, respectively, at each site, an average (median) of 14 (range, 1-77) and 245 (range, 58-495) microfilariae was ingested. However, within 24 hours of microfilarial ingestion a mortality of 47% (16/34 flies) was observed in the group of flies which fed on the back, as compared with 2% (2/101 flies) in the other group which fed on the legs. At a temperature varying between 16 degrees C and 24 degrees C, the development of O. volvulus larvae in S. pintoi was synchronous and orderly; no abnormal nor deformed larvae were observed. Third-stage larvae were first seen in the head of flies dying between 8 and 9 days after microfilarial ingestion, and 98 of 100 larvae recovered from days 10-16 were in the third stage. The proportions of females harboring third-stage larvae among flies which lived through day 8 in the two groups which fed on the legs and back, respectively, were 55% (21/38 flies) and 63% (5/8 flies). Although only two of five positive flies in the latter group contained third-stage larvae in the head (1 and 12, respectively), 71% (15/21 positive flies) of the former group had an average of 2.7 third-stage larvae in the head (range, 1-10).(ABSTRACT TRUNCATED AT 250 WORDS)

Seasonal occurrence of Simulium ochraceum, the principal vector of Onchocerca volvulus in the southeastern endemic area of Guatemala.

Investigation of the seasonal occurrence of Simulium ochraceum, the principal vector of the Guatemalan strain of Onchocerca volvulus, were made from August 1978 until January 1980 in the upper reaches of the two main rivers of endemic onchocerciasis in Escuintla, Guatemala. The results showed that in the late dry season S. ochraceum larvae were restricted to permanent streams at intermediate altitudes. During the rainy season, though, the preimaginal sites of this black fly extended to the upper reaches of the numerous small intermittent streams due to partial subterranean flows. Seasonal occurrence of S. ochraceum in these temporary streams was observed throughout the wet season. However, this was most pronounced during the early months of the dry season (October-December) as long as these streamlets continued to flow. The adult population along the headwaters of these two rivers showed a high peak from October-December. This represented a pattern distinct from that of other places where the preimaginal sites of S. ochraceum occurred mostly in larger perennially running streams. The implications which the present findings have for any future larvicidal control program on the onchocerciasis-endemic region of Guatemala are discussed.