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.

The performance of health laboratories and the quality of malaria diagnosis in six districts of Tanzania

Early laboratory diagnosis is critical for the optimal management of human malaria, particularly following the introduction of relatively expensive, artemisinin-combination therapies (ACT). The performance of the laboratories and the quality of malaria diagnosis have recently been assessed in 36 healthcare facilities in six districts of Tanzania. Questionnaires, checklists and observations were used to collect information on the availability and functional status of equipment as well as on laboratory personnel and their performance in malaria diagnosis. Together, the surveyed facilities had 112 laboratory staff [almost half (41.1%) of whom were laboratory assistants] and 57 microscopes. Twenty-seven (75.0%) of the healthcare facilities included in the survey had only one functional microscope each. Only seven (12.3%) of the assessed microscopes had been serviced in the previous 2 years. Of the 38 microscopists who were assessed, 24 (63.2%) were re-using microscope slides, 29 (73.5%) were producing bloodsmears of low quality, and 30 (79.0%) were using Field's stain. Although the facility microscopists gave similar results to experienced research microscopists when reading bloodsmears prepared by the survey team, using high-quality reagents (kappa=0.769), they appeared far less competent when reading smears stained using the reagents from the study laboratories (kappa=0.265-0.489). The quality of malaria diagnosis at healthcare facilities in Tanzania, which is generally poor (largely because of inadequate supplies of consumables and the limited skills of laboratory staff in the preparation of bloodsmears), urgently needs to be improved if the utilization of ACT is to be sustainable.