Susceptibility of Anopheles gambiae complex mosquitoes to microbial larvicides in diverse ecological settings in western Kenya.

The microbial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) (Bacillales: Bacillaceae) are well known for their efficacy and safety in mosquito control. In order to assess their potential value in future mosquito control strategies in western Kenya, the current study tested the susceptibility of five populations of Anopheles gambiae complex mosquitoes (Diptera: Culicidae), collected from five diverse ecological sites in this area, to Bti and Bs under laboratory conditions. In each population, bioassays were conducted with eight concentrations of larvicide (Bti/Bs) in four replicates and were repeated on three separate days. Larval mortality was recorded at 24 h or 48 h after the application of larvicide and subjected to probit analysis. A total of 2400 An. gambiae complex larvae from each population were tested for their susceptibility to Bti and Bs. The mean (± standard error of the mean, SEM) lethal concentration values of Bti required to achieve 50% and 95% larval mortality (LC50 and LC95 ) across the five populations were 0.062 (± 0.005) mg/L and 0.797 (± 0.087) mg/L, respectively. Corresponding mean (± SEM) values for Bs were 0.058 (± 0.005) mg/L and 0.451 (± 0.053) mg/L, respectively. Statistical analysis indicated that the five populations of An. gambiae complex mosquitoes tested were fully susceptible to Bti and Bs, and there was no significant variation in susceptibility among the tested populations.

Application of hydrolysis probe analysis to identify clade types of the malaria vector mosquito Anopheles funestus sensu stricto from Muheza, northeastern Tanzania.

A hydrolysis probe analysis (TaqMan assay) was used to study clade types in Anopheles funestus sensu stricto Giles, a major malaria vector in sub-Saharan Africa, with specimens collected from Muheza in Tanga, northeastern Tanzania. A total of 186 An. funestus specimens were analysed, revealing that 176 (94.6%) were of clade I and 10 (5.4%) of clade II. These findings extend the distribution of clade type II from southern Mozambique and northern Zambia to northeastern Tanzania. The technique used can also be of great value in assessing the role and contribution of these clade types in malaria transmission and insecticide resistance frequencies for An. funestus s.s.

Jigger flea infestation (tungiasis) in rural western Tanzania: high prevalence and severe morbidity.

Epidemiologic and clinical data on the parasitic skin disease tungiasis are limited from sub-Saharan Africa, and virtually nonexistent from the East African region. We performed a community-based cross-sectional study in two villages in Kasulu district, western Tanzania. Study participants were examined for the presence of tungiasis and disease-associated morbidity. In total, 586 individuals >5 years of age were enrolled, and 249 (42.5%; 95% CI: 38.5-46.5) diagnosed with tungiasis. The ≥45 year-olds showed highest prevalence of tungiasis (71.1%) and most severe parasite load (median number of embedded fleas: 17.5; interquartile range: 15-22.5). Prevalence was slightly, but not significantly, higher in males than in females (45.3 vs 39.7%; p=0.17). Itching (68.3%), pain (38.6%) and ulcers (30.1%) were common; 22.1% of individuals found it difficult to walk due to tungiasis, and in 21.3% loss of toenails was observed. Considering the high prevalence and considerable morbidity in the population, we conclude that tungiasis is a public health threat in the study villages and that the disease needs to be recognized by health authorities. Future studies on risk factors, animal reservoirs and evidence-based control measures are needed.

Vector species composition and malaria infectivity rates in Mkuzi, Muheza District, north-eastern Tanzania.

Entomological surveys were conducted in Mkuzi village in Muheza District, north-east Tanzania from April to September 2003. The objectives were to determine the species composition and infectivity rates of mosquitoes in Mkuzi village. Mosquito collection was done using CDC light trap and pyrethrum spray catch (PSC) techniques. The light trap: spray catch ratio was 2.2:1. A total of 2157 mosquitoes were collected (light trap = 1483; PSC = 674). Anopheles gambiae s.s. accounted for 56.7% (N = 1224) of all mosquitoes collected. Other species were An. funestus complex (19.2%) and Culex quinquefasciatus (24.1%).The mosquito density per room was 74.15 and 33.7 for light trap and PSC techniques, respectively. A total of 1637 Anopheles mosquitoes were tested for circumsporozoite protein by Enzyme linked Immunosobent Assay (ELISA). The overall infectivity rate for circumsporozoite protein for P. falciparum in Anopheles mosquitoes was 21.14% (346/1637). Species-specific infectivity rates were 22.7% (278/1224) in An. gambiae s.s. and 24.0% (68/283) in An. funestus funestus, 0% (0/80) for An. rivulorum and 0% (0/50) for An. parensis. Blood meal analysis indicated that 92.3% of An. gambiae s.s, 88.9% of An. funestus s.s., 64.5% of An. rivulorum and 67.7% of An. parensis had taken blood meal from human hosts. In conclusion, malaria transmission in Mkuzi area of Muheza district is mainly by the highly anthropophagic An. gambiae s.s. and An. funestus s.s. More studies are needed to identify the seasonal variation of species composition and transmission dynamics in this village.

Vector Species Composition and Malaria Infectivity Rates in Mkuzi; Muheza District; North-Eastern Tanzania

Entomological surveys were conducted in Mkuzi village in Muheza District; north-east Tanzania from April to September 2003. The objectives were to determine the species composition and infectivity rates of mosquitoes in Mkuzi village. Mosquito collection was done using CDC light trap and pyrethrum spray catch (PSC) techniques. The light trap: spray catch ratio was 2.2:1. A total of 2157 mosquitoes were collected (light trap= 1483; PSC= 674). Anopheles gambiae s.s. accounted for 56.7(N=1224) of all mosquitoes collected. Other species were An. funestus complex (19.2) and Culex quinquefasciatus (24.1).The mosquito density per room was 74.15 and 33.7 for light trap and PSC techniques; respectively. A total of 1637 Anopheles mosquitoes were tested for circumsporozoite protein by Enzyme linked Immunosobent Assay (ELISA). The overall infectivity rate for circumsporozoite protein for P. falciparum in Anopheles mosquitoes was 21.14(346/1637). Species-specific infectivity rates were 22.7(278/1224) in An. gambiae s.s. and 24.0(68/283) in An. funestus funestus; 0(0/80) for An. rivulorum and 0(0/50) for An.parensis. Blood meal analysis indicated that 92.3of An. gambiae s.s; 88.9of An. funestus s.s.; 64.5of An. rivulorum and 67.7of An. parensis had taken blood meal from human hosts. In conclusion; malaria transmission in Mkuzi area of Muheza district is mainly by the highly anthropophagic An. gambiae s.s. and An. funestus s.s. More studies are needed to identify the seasonal variation of species composition and transmission dynamics in this village