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ABSTRACTTsetse flies (Glossinasp.) are the vectors that transmit African trypanosomes, protozoan parasites that cause human sleeping sickness and veterinary infections in the African continent. These blood-feeding dipteran insects deposit saliva at the feeding site that enables the blood-feeding process. Here we demonstrate that tsetse fly saliva also accelerates the onset of a Trypanosoma bruceiinfection. This effect was associated with a reduced inflammatory reaction at the site of infection initiation (reflected by a decrease of interleukin-6 [IL-6] and IL-12 mRNA) as well as lower serum concentrations of the trypanocidal cytokine tumor necrosis factor. Variant-specific surface glycoprotein-specific antibody isotypes immunoglobulin M (IgM) and IgG2a, implicated in trypanosome clearance, were not suppressed. We propose that tsetse fly saliva accelerates the onset of trypanosome infection by inhibiting local and systemic inflammatory responses involved in parasite control.

Tsetse flies (Glossina sp.) are the vectors that transmit African trypanosomes, protozoan parasites that cause human sleeping sickness and veterinary infections in the African continent. These blood-feeding dipteran insects deposit saliva at the feeding site that enables the blood-feeding process. Here we demonstrate that tsetse fly saliva also accelerates the onset of a Trypanosoma brucei infection. This effect was associated with a reduced inflammatory reaction at the site of infection initiation (reflected by a decrease of interleukin-6 [IL-6] and IL-12 mRNA) as well as lower serum concentrations of the trypanocidal cytokine tumor necrosis factor. Variant-specific surface glycoprotein-specific antibody isotypes immunoglobulin M (IgM) and IgG2a, implicated in trypanosome clearance, were not suppressed. We propose that tsetse fly saliva accelerates the onset of trypanosome infection by inhibiting local and systemic inflammatory responses involved in parasite control.

The current control of Phebotomus argentipes (Annandale and Brunetti), the vector of Leishmania donovani (Laveran and Mesnil), on the Indian subcontinent is base on indoor residual spraying. The efficacy of this method depends, among other factors, on the timing and number of spraying rounds, which depend on the P. argentipes seasonality. To describe P. argentipes’ seasonal patterns, six visceral leishmaniasis (VL) endemic villages, three in Muzaffarpur and three in Sunsari districts in India and Nepal, respectively, were selected based on accessibility and VL incidence. Ten houses per cluster with the highest P. argentipes density were monitored monthly for 15–16 mo using Center for Disease Control and Prevention light traps. Minimum and maximum temperature and rainfall data for the months January 2006 through December 2007 were collected from the nearest available weather stations. Backwards stepwise regression was used to generate the minimal adequate model for explaining the monthly variation in P. argentipes populations. The seasonality of P. argentipes is similar in India and Nepal, with two annual density peaks around May and October. Monthly P. argentipes density is positively associated with temperature and negatively associated with rainfall in both study sites. The multivariate climate model explained 57% of the monthly vectorial abundance. Vector control programs against P. argentipes (i.e., indoor residual spraying) should take into account the seasonal described here when implementing and monitoring interventions. Monitoring simple meteorological variables (i.e., temperature, rainfall) may allow prediction of VL epidemics on the Indian subcontinent.

The presence of cryptic species within Anopheles minimus s.l. Theobald, one of the most widespread malaria vectors in Southeast Asia, was suggested on the basis of behavioral heterogeneities observed within this taxon. Subsequently, two species, A and C, were recognized. However, the existence of these cryptic species did not explain all observed behavioral heterogeneities within this complex. Besides, data on the behavior of vectors are essential to understand the dynamics of disease transmission and thus evaluate the appropriateness of vector control measures. Different collection methods were used to collect Anopheles species from several localities in Southeast Asia to assess the inter- and intraspecific behavioral divergences of An. minimus A and C. Collection results were subjected to a correspondence analysis. The members of the An. minimus complex were identified by use of the octanol dehydrogenase allozyme profiles or the polymerase chain reaction-restriction fragment length polymorphism assay. Large intraspecific behavioral differences were observed among populations of An. minimus A. These populations belong to the same species on the basis of the applied genetic markers. In northern Vietnam, species A tended to be more zoophilic, whereas in the study sites of south central Vietnam, Cambodia, and Laos it showed marked antropophilic behavior when cattle were scarce. In the most northern study site, An. minimus A showed noteworthy endophilic behavior. An. minimus C was primarily zoophilic and based on this behavior, its role in malaria transmission is questionable. However, it was only found in one locality, so that intraspecific behavioral variation could not be assessed. An. minimus A is able to change its host preference in function of local situations in host availability. Hence, its role in malaria transmission can differ from region to region. Similarly, the impact of vector control on this species may differ between localities. In conclusion, intraspecific behavioral differences in Anopheles species can occur and these behavioral heterogeneities, albeit important for disease transmission and control, are not a priori indicative for the presence of cryptic species.

A cellulose acetate electrophoresis system was used to study the Anopheles gambiae complex at 2 villages in Central Imbo Valley and at 1 village in South Imbo Valley (Burundi). In South Imbo, only An. gambiae Giles sensu stricto was present. In the drier Central Imbo, the dominant species was An. arabiensis Patton (97.5%); An. gambiae s.s. represented only 2.5%. Both species were separated readily by Odh and Mpi, because they did not share alleles at those loci. Indoor resting An. gambiae s.s. from South Imbo differed significantly from outdoor resting females at 2 loci, Mpi, and Got-2. In Central Imbo, total An. arabiensis did not differ between adjacent villages. Endophagic An. arabiensis significantly differed at loci a-Gpd, and Idh-I between the 2 villages, whereas no difference was observed between exophagic females. Allelic and genotypic frequencies at the locus Mdh-2 were significantly different between indoor and outdoor biting An. arabiensis. Active choice for the best place to bite or to rest seemed to be associated with specific genotypes. The Nei genetic distance values were typical of conspecific populations, ranging from 0.154 to 0.160 between An. gambiae s.s. and An. arabiensis. Even though vector populations were structured at spatial and behavioral levels, they were panmictic, and thus selection of exophilic or exophagic vectors, or both, by insecticide pressure is not likely to occur.