Variation in cuticular hydrocarbons among strains of the Anopheles gambiae sensu stricto by analysis of cuticular hydrocarbons using gas liquid chromatography of larvae.

Cuticular hydrocarbons of larvae of individual strains of the Anopheles gambiae sensu stricto were investigated using gas liquid chromatography. Biomedical discriminant analysis involving multivariate statistics suggests that there was clear hydrocarbon difference between the Gambian(G3), the Nigerian (16CSS and, its malathion resistant substrain, REFMA) and the Tanzanian (KWA) strains. The high degree of segregation (95%) in hydrocarbons among the four strains investigated indicates that further analysis is needed to enable understanding of hydrocarbon variation in samples of An. gambiae especially from areas where these populations co-exist.

Onchocerciasis and Chagas' disease control: the evolution of control via applied research through changing development scenarios.

This paper addresses the development of control strategies of two different parasitic diseases and identifies commonalities which have contributed to the success of regional intercountry programmes of onchocerciasis control in Africa, the Onchocerciasis Control Programme (OCP), and the new African Programme for Onchocerciasis Control (APOC) and the Chagas' Disease Control Programme in the southern cone of South America.

Transformation, development, and transmission of axenically cultured amastigotes of Leishmania mexicana in vitro and in Lutzomyia longipalpis.

Axenic cultures of Leishmania mexicana amastigotes were transformed to promastigotes in vitro and in vivo in Lutzomyia longipalpis. In vitro, both exponential phase and stationary phase amastigotes were capable of transforming and growing as promastigotes, but exponential phase amastigotes completed this transition more quickly. In vivo, both populations were capable of establishing infections in sand flies by membrane feeding and could be transmitted to BALB/c mice via bite. A variety of morphologic forms could be observed in vivo, including putative metacyclic promastigotes. Infection rates in sandflies with axenic amastigotes were comparable with those achieved with lesion-derived amastigotes, supporting the use of these cultured forms in studies of parasite biology.

Cuticular hydrocarbons, isoenzymes and behavior of three populations of Anopheles darlingi from Brazil.

Three populations of Anopheles darlingi were studied for cuticular hydrocarbons, isoenzymes and patterns of peak biting activity. Differences were found in specimens from Costa Marques, a malaria endemic area; Dourado, a site with a very exophilic population and Juturnaíba, located near the type locality. Twelve hour collections from sunset to sunrise showed that An. darlingi from Costa Marques had a bimodal biting activity profile with a major peak at sunset and a minor peak at sunrise. At Dourado, the pattern was trimodal, with peaks at both morning and evening periods of twilight and near midnight. The Juturnaíba population showed a slight increase in activity near 2000 and 0100 h. Nei's genetic distances, determined by isoenzyme electrophoresis between pairs of populations, were low (D < or = 0.049). Using discriminant analysis for the cuticular hydrocarbons, 92.4% of the specimens from Costa Marques, 91.2% of the specimens from Dourado and 61.3% from Juturnaíba were correctly identified. Cuticular hydrocarbon and isoenzyme results matched very well: the smaller the Nei's distance, the more misidentifications occurred in the jackknife estimator used in the cuticular hydrocarbon analysis. This is the first report of cuticular hydrocarbon analysis in combination with isoenzymes to investigate neotropical anopheline species.

Aphid derived sugars in the neotropical sandfly--Lutzomyia peruensis.

It is known that a sugar meal is a prerequisite for the transmission of Leishmania by sandflies in the laboratory. Lutzomyia peruensis the proven vector of Leishmania peruviana, was caught by aspiration from crevices in rocks near Chaute in the Rimac Valley, Peru, cryopreserved and analysed for sugars using HPLC. The major sugars present are glucose and fructose as well as smaller amounts of sucrose, maltose, melibiose, turanose and a trisaccharide, probably raffinose. The results indicate that the major carbohydrate sugar meal of Lutzomyia peruensis is aphid honeydew. This is the first report of such behaviour in Neotropical sandflies.

Separation of Psychodopygus carrerai carrerai and P. yucumensis (Diptera: Psychodidae) by gas chromatography of cuticular hydrocarbons.

Specimens of two species of sandfly, Psychodopygus carrerai carrerai and P. yucumensis, vectors of Leishmania braziliensis braziliensis in the subandean lowlands of Bolivia, were subjected to cuticular hydrocarbon analysis to ascertain if the technique could separate the females. A high degree of separation (87%) was obtained based on significant differences in the cuticular hydrocarbon composition of these two species. Statistical treatment of the data shows that these species, initially identified by the colour of the mesonotum, can also be distinguished by their hydrocarbons.

Chemical analysis of compounds extracted from the tergal "spots" of Lutzomyia longipalpis from Brazil.

The chemical composition of the compounds contained in the tergal spots of Lutzomyia longipalpis was investigated. Four populations of L. longipalpis were examined, originating from: Sobral, Ceará, Brazil (one spot and two spot populations), Santarém, Pará, Brazil (one spot) and Marajó Island, Pará, Brazil (one spot). The tergal spots were dissected out, extracted in hexane and analysed on a gas chromatograph/mass spectrometer. Two compounds were found, identical to compounds found in earlier studies, but there was no correlation between number of tergal spots and type of compound present. It was suggested that the number of tergal spots could not be used as a marker for reproductively isolated populations, and that analysis of the compound present within the spots might be necessary to characterize potentially good vector populations.