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.

Genetic Characterization of Vibrio cholerae O1 isolates from outbreaks between 2011 and 2015 in Tanzania.

BACKGROUND: Cholera outbreaks have occurred in Tanzania since 1974. To date, the genetic epidemiology of these outbreaks has not been assessed. METHODS: 96 Vibrio cholerae O1 isolates from five regions were characterized, and their genetic relatedness assessed using multi-locus variable-number tandem-repeat analysis (MLVA) and whole genome sequencing (WGS). RESULTS: Of the 48 MLVA genotypes observed, 3 were genetically unrelated to any others, while the remaining 45 genotypes separated into three MLVA clonal complexes (CCs) - each comprised of genotypes differing by a single allelic change. In Kigoma, two separate outbreaks, 4 months apart (January and May, 2015), were each caused by genetically distinct strains by MLVA and WGS. Remarkably, one MLVA CC contained isolates from both the May outbreak and ones from the 2011/2012 outbreak in Dar-es-Salaam. However, WGS revealed the isolates from the two outbreaks to be distinct clades. The outbreak that started in August 2015 in Dar-es-Salaam and spread to Morogoro, Singida and Mara was comprised of a single MLVA CC and WGS clade. Isolates from within an outbreak were closely related differing at fewer than 5 nucleotides. All isolates were part of the 3rd wave of the 7th pandemic and were found in four clades related to isolates from Kenya and Asia. CONCLUSIONS: We conclude that genetically related V. cholerae cluster in outbreaks, and distinct strains circulate simultaneously.

Modified veranda-trap hut for improved evaluation of vector control interventions.

Experimental huts with veranda traps have been used in Tanzania since 1963 for the study of residual insecticides for use with insecticide-treated nets and indoor residual spraying. Mosquitoes are allowed unrestricted entry through the eaves to facilitate the collection of an estimable proportion of mosquitoes that attempt to exit through the eave gaps, which are left open on two sides of the hut. This study was designed to validate the use of eave baffles to funnel entry and to prevent mosquito escape, and to determine biting times of Anopheles arabiensis (Patton) (Diptera: Culicidae). Anopheles arabiensis and Culex quinquefasciatus (Say) (Diptera: Culicidae) were released into the room at 20.30 hours and collected the following morning from veranda traps, window traps and the room. Centers for Disease Control light traps hung overnight next to volunteers were emptied every 2 h to determine peak biting times. A total of 55% of An. arabiensis were trapped before 22.30 hours and the highest peak in 'biting' was recorded during 18.30-20.30 hours. Of the released An. arabiensis that exited into veranda traps, 7% were captured in veranda traps entered through baffles and 93% were captured in traps entered through unmodified eaves. When veranda screens were left open to allow for escape outdoors, recapture rates were 68% for huts with eave baffles and 39% for huts with unmodified eaves. The comparison of open eaves with baffled eaves validated the assumption that in huts of the traditional non-baffled design, 50% of mosquitoes escape through open eaves. Eave baffles succeeded in reducing the potential for mosquito exit and produced more precise estimates of effect.

Trends in the selection of insecticide resistance in Anopheles gambiae s.l. mosquitoes in northwest Tanzania during a community randomized trial of longlasting insecticidal nets and indoor residual spraying.

Anopheles gambiae s.l. (Diptera: Culicidae) in Muleba, Tanzania has developed high levels of resistance to most insecticides currently advocated for malaria control. The kdr mutation has almost reached fixation in An. gambiae s.s. in Muleba. This change has the potential to jeopardize malaria control interventions carried out in the region. Trends in insecticide resistance were monitored in two intervention villages using World Health Organization (WHO) susceptibility test kits. Additional mechanisms contributing to observed phenotypic resistance were investigated using Centers for Disease Control (CDC) bottle bioassays with piperonylbutoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) synergists. Resistance genotyping for kdr and Ace-1 alleles was conducted using quantitative polymerase chain reaction (qPCR). In both study villages, high phenotypic resistance to several pyrethroids and DDT was observed, with mortality in the range of 12-23%. There was a sharp decrease in mortality in An. gambiae s.l. exposed to bendiocarb (carbamate) from 84% in November 2011 to 31% in December 2012 after two rounds of bendiocarb-based indoor residual spraying (IRS). Anopheles gambiae s.l. remained susceptible to pirimiphos-methyl (organophosphate). Bendiocarb-based IRS did not lead to the reversion of pyrethroid resistance. There was no evidence for selection for Ace-1 resistance alleles. The need to investigate the operational impact of the observed resistance selection on the effectiveness of longlasting insecticidal nets and IRS for malaria control is urgent.

Distribution and spread of pyrethroid and DDT resistance among the Anopheles gambiae complex in Tanzania.

The development of insecticide resistance is a threat to the control of malaria in Africa. We report the findings of a national survey carried out in Tanzania in 2011 to monitor the susceptibility of malaria vectors to pyrethroid, organophosphate, carbamate and DDT insecticides, and compare these findings with those identified in 2004 and 2010. Standard World Health Organization (WHO) methods were used to detect knock-down and mortality rates in wild female Anopheles gambiae s.l. (Diptera: Culicidae) collected from 14 sentinel districts. Diagnostic doses of the pyrethroids deltamethrin, lambdacyhalothrin and permethrin, the carbamate propoxur, the organophosphate fenitrothion and the organochlorine DDT were used. Anopheles gambiae s.l. was resistant to permethrin in Muleba, where a mortality rate of 11% [95% confidence interval (CI) 6-19%] was recorded, Muheza (mortality rate of 75%, 95% CI 66-83%), Moshi and Arumeru (mortality rates of 74% in both). Similarly, resistance was reported to lambdacyhalothrin in Muleba, Muheza, Moshi and Arumeru (mortality rates of 31-82%), and to deltamethrin in Muleba, Moshi and Muheza (mortality rates of 28-75%). Resistance to DDT was reported in Muleba. No resistance to the carbamate propoxur or the organophosphate fenitrothion was observed. Anopheles gambiae s.l. is becoming resistant to pyrethoids and DDT in several parts of Tanzania. This has coincided with the scaling up of vector control measures. Resistance may impair the effectiveness of these interventions and therefore demands close monitoring and the adoption of a resistance management strategy.

Prevalence of genotypic resistance to antiretroviral drugs in treatment-naive youths infected with diverse HIV type 1 subtypes and recombinant forms in Dar es Salaam, Tanzania.

As human immunodeficiency virus (HIV) diversity may have an impact on both vaccine efficacy and drug resistance, it is important to have knowledge of circulating genetic variants. With widespread use of antiretroviral (ARV) drugs in Africa, one of the major potential challenges is the risk of emergence of ARV drug-resistant HIV strains. This study aimed to determine the circulating HIV subtypes and recombinant forms, as well as the prevalence of ARV drug resistance mutations, among 75 treatment-naive HIV-infected youths in Dar es Salaam, Tanzania. Gag (n = 48), partial pol (n = 44), and partial env (n = 35) sequencing was performed; all three regions were sequenced in 26 samples. Evidence of infection with recombinant viruses was found in 12 (46%) participants; AC recombinants were the most commonly detected and they were identified in six (23%) participants. Of individuals infected with nonrecombinant strains, subtype A was most commonly detected in seven (27%) participants, followed by subtype C detected in six (23%) participants and subtype D detected in one (4%) participant. Among the pol sequences from 44 individuals, three (7%) had resistance to nucleoside reverse transcriptase (RT) inhibitors and four (9%) had nonnucleoside RT inhibitor resistance mutations. Of these, three (7%) individuals were infected with viruses with cross-resistance mutations to both classes of RT inhibitors. These resistant mutations were all associated with drugs currently used in first-line therapy and in the prevention of vertical transmission. This high prevalence of resistance mutations is of considerable concern in apparently drug-naive populations as it may result in treatment failure and the spread of ARV-resistant strains.

Evaluation of indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-susceptible Anopheles arabiensis and pyrethroid-resistant Culex quinquefasciatus mosquitoes.

Chlorfenapyr is a pyrrole insecticide with a unique non-neurological mode of action. Laboratory bioassays of chlorfenapyr comparing the mortality of pyrethroid-susceptible and -resistant Anopheles gambiae s.s. and Culex quinquefasciatus mosquitoes indicated that operational cross-resistance is unlikely to occur (resistance ratio ranged between 0 and 2.1). Three trials of chlorfenapyr indoor residual spraying were undertaken in experimental huts in an area of rice irrigation in northern Tanzania that supports breeding of A. arabiensis. Daily mosquito collections were undertaken to assess product performance primarily in terms of mortality. In the second trial, 250mg/m(2) and 500mg/m(2) chlorfenapyr were tested for residual efficacy over 6 months. Both dosages killed 54% of C. quinquefasciatus, whilst for A. arabiensis 250mg/m(2) killed 48% compared with 41% for 500mg/m(2); mortality was as high at the end of the trial as at the beginning. In the third trial, 250mg/m(2) chlorfenapyr was compared with the pyrethroid alpha-cypermethrin dosed at 30mg/m(2). Chlorfenapyr performance was equivalent to the pyrethroid against A. arabiensis, with both insecticides killing 50% of mosquitoes. Chlorfenapyr killed a significantly higher proportion of pyrethroid-resistant C. quinquefasciatus (56%) compared with alpha-cypermethrin (17%). Chlorfenapyr has the potential to be an important addition to the limited arsenal of public health insecticides for indoor residual control of A. arabiensis and pyrethroid-resistant species of mosquito.

Behavioural and insecticidal effects of organophosphate-, carbamate- and pyrethroid-treated mosquito nets against African malaria vectors.

Three insecticides - the pyrethroid deltamethrin, the carbamate carbosulfan and the organophosphate chlorpyrifos-methyl - were tested on mosquito nets in experimental huts to determine their potential for introduction as malaria control measures. Their behavioural effects and efficacy were examined in Anopheles gambiae Giles s.s. (Diptera: Culicidae) and Anopheles funestus Giles s.s. in Muheza, Tanzania, and in Anopheles arabiensis Patton and Culex quinquefasciatus Say in Moshi, Tanzania. A standardized dosage of 25 mg/m(2) plus high dosages of carbosulfan (50 mg/m(2), 100 mg/m(2) and 200 mg/m(2)) and chlorpyrifos-methyl (100 mg/m(2)) were used to compare the three types of insecticide. At 25 mg/m(2), the rank order of the insecticides for insecticide-induced mortality in wild An. gambiae and An. funestus was, respectively, carbosulfan (88%, 86%) > deltamethrin (79%, 78%) > chlorpyrifos-methyl (35%, 53%). The rank order of the insecticides for blood-feeding inhibition (reduction in the number of blood-fed mosquitoes compared with control) in wild An. gambiae and An. funestus was deltamethrin > chlorpyrifos-methyl > carbosulfan. Carbosulfan was particularly toxic to endophilic anophelines at 200 mg/m(2), killing 100% of An. gambiae and 98% of An. funestus that entered the huts. It was less effective against the more exophilic An. arabiensis (67% mortality) and carbamate-resistant Cx quinquefasciatus (36% mortality). Carbosulfan deterred anophelines from entering huts, but did not deter carbamate-resistant Cx quinquefasciatus. Deltamethrin reduced the proportion of insects engaged in blood-feeding, probably as a consequence of contact irritancy, whereas carbosulfan seemed to provide personal protection through deterred entry or perhaps a spatial repellent action. Any deployment of carbosulfan as an individual treatment on nets should be carried out on a large scale to reduce the risk of diverting mosquitoes to unprotected individuals. Chlorpyrifos-methyl was inferior to deltamethrin in terms of mortality and blood-feeding inhibition and would be better deployed on a net in combination with a pyrethroid to control insecticide-resistant mosquitoes.

Case studies in public-private-partnership in health with the focus of enhancing the accessibility of health interventions.

Various definitions have been framed for public-private partnerships (PPPs) in health depending on the desired relationship and the characteristics of the respective sectors. These relationships span from a continuum of loose relationships with narrow objectives, lack of a legal status and an absence of a formalized membership or governing body to high level institutionalization. The latter includes concrete objectives, the presence of a legal status and permanent multi-sectoral membership. The study used qualitative research methods including case studies, literature review and interview with key informants. The research undertakes an extensive literature review of various PPP models in health in scale and in scope which are aimed at advancing public health goals in developing countries. The major emphasis is on a qualitative description of some of the PPPs in the planning and implementation phases, including the challenges encountered. This background is used to analyse in-depth two case studies which are both health oriented; the first one is a national level NGO consortium with a focus on malaria and the second one is an international advocacy group with an overarching goal of protecting children against malaria through an innovative mechanism. The case study approach is used to analyze why the PPP approach was used to address malaria control and how it was implemented. Both PPPs demonstrated that relationships between the public and private sector may begin from very humble and loose beginnings. However, with perseverance from committed individuals, a vision and trustworthiness may become powerful advocates for meeting prescribed health agendas. In conclusion, three key themes (trust, sacrifice and championship) run vividly through the case studies and are significant for developing countries to emulate.

Mosquitoes and bednets: testing the spatial positioning of insecticide on nets and the rationale behind combination insecticide treatments.

The recent development of pyrethroid resistance of operational significance in Anopheles gambiae s.l. is a major threat to the control of malaria in West Africa. The so-called '2-in-1' bednet, in which the top of the net is treated with a non-pyrethroid insecticide and the sides with pyrethroid, has been proposed as a way of maintaining efficacy in the wake of such resistance. A host-seeking female Anopheles mosquito must contact both the top and sides of a '2-in-1' net, however, for such nets to be useful in resistance management. In the present study, the interaction between mosquitoes and insecticide-treated bednets (ITN) was explored by restricting the insecticide to particular surfaces of the nets (top only or sides only) and then testing these nets, untreated nets and nets treated on all their surfaces in experimental huts, under simulated field conditions. Over the 6-week trial, there was no significant difference in An. arabiensis mortality between nets treated with pyrethroid on the top only (39.2%), sides only (39.6%) and all surfaces (39.7%), thus indicating that a female An. arabiensis usually contacts both the top and sides of a bednet during its host-seeking behaviour. The data on blood-feeding indicated, however, that the insecticide used on the sides of the net may be more important in preventing mosquito biting than that on the top. These results support the rationale behind the '2-in-1' nets. Such nets may have advantages over the use of nets treated on all surfaces with a mixture of insecticides that includes a non-pyrethroid component. With the '2-in-1', the more toxic component can be deployed on the top of the net, away from human contact, while the more repellent pyrethroid can be restricted to the sides, to prevent blood-feeding. With the scaling-up of ITN coverage and the need to preserve pyrethroid efficacy, more consideration should be given to switching from pyrethroid-only nets to 'combination' nets that have been treated with a pyrethroid and another insecticide. Since the mosquitoes that act as malarial vectors may contact all surfaces of a bednet during their host-seeking, spatial heterogeneity in insecticide levels over the surface of a net may not reduce that net's overall efficacy. Nets with a rather uneven distribution of insecticide (such as those that might be produced using home-treatment insecticide kits) may therefore be no less effective, prior to washing, than nets with a more even distribution of insecticide (such as long-lasting insecticidal nets produced under factory conditions).

Has the HIV epidemic in rural Mwanza, Tanzania reached a plateau?

Data from studies in Mwanza Region in Tanzania suggest stabilising HIV prevalence. The objective was to determine the factors that may have contributed to the relatively stable pattern of the HIV prevalence observed in the comparison communities of the Mwanza STD treatment trial in rural Mwanza Region, Tanzania between 1991 and 2001. Socio-demographic, sexual behaviour and HIV prevalence data in two surveys conducted 10 years apart in the same communities using similar sampling schemes were compared. The age standardised HIV prevalence was 3.8% (95% CI: 3.2-4.6) in 1991 and 4.3% (95% CI: 2.8-6.4) in 2001 for males (Z= - 0.56, P= 0.58); and 4.5% (95% CI: 3.8-5.3) in 1991 and 3.9% (95% CI: 2.6-5.6) in 2001 for females (Z= 0.64, P = 0.52). Participants in the 2001 survey reported significantly fewer lifetime and recent sexual partners (12 months), Sexually Transmitted disease syndromes (12 months) and significantly more condom use at last sex with casual partners than those in the 1991 behaviour survey. We conclude that STD/HIV infection prevention activities in rural Mwanza may be responsible for changes in risky sexual behaviour and have successfully impeded the spread of HIV infection. These activities should therefore be enhanced to reduce HIV incidence even further. In addition, modelling studies are needed to assess whether mobility of HIV infected people out of rural communities may stabilise the prevalence of the HIV infection in the general populations.

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.

Comparative efficacies of permethrin-, deltamethrin- and alpha-cypermethrin-treated nets, against Anopheles arabiensis and Culex quinquefasciatus in northern Tanzania.

Mosquito nets treated with permethrin, deltamethrin or alpha-cypermethrin at 25 mg/m(2) were evaluated in experimental huts in an area of rice irrigation near Moshi, in northern Tanzania. The nets were deliberately holed to resemble worn nets. The nets treated with permethrin offered the highest personal protection against Anopheles arabiensis (61.6% reduction in fed mosquitoes) and Culex quinquefasciatus (25.0%). Deltamethrin and alpha-cypermethrin provided lower personal protection against An. arabiensis (46.4% and 45.6%, respectively) and no such protection against Cx. quinquefasciatus. Permethrin performed poorly in terms of mosquito mortality, however, killing only 15.2% of the An. arabiensis and 9.2% of the Cx. quinquefasciatus exposed to the nets treated with this pyrethroid (after correcting for control mortality). The alpha-cypermethrin and deltamethrin performed marginally better, with respective mortalities of 32.8% and 33.0% for An. arabiensis and 19.4% and 18.9% for Cx quinquefasciatus. The poor killing effect of permethrin was confirmed in a second trial where a commercial, long-lasting insecticidal net based on this pyrethroid (Olyset) produced low mortalities in both An. arabiensis (11.8%) and Cx. quinquefasciatus (3.6%). Anopheles arabiensis survivors collected from the verandahs of the experimental huts and tested on 0.75%-permethrin and 0.05%-deltamethrin papers, in World Health Organization susceptibility kits, showed mortalities of 96% and 100%, respectively. The continued use of permethrin-treated nets is recommended for personal protection against An. arabiensis. In control programmes that aim to interrupt transmission of pathogens by mosquitoes and/or manage pyrethroid resistance in such vectors, a combination of a pyrethroid and another insecticide with greater killing effect should be considered.

Experimental hut evaluation of the pyrrole insecticide chlorfenapyr on bed nets for the control of Anopheles arabiensis and Culex quinquefasciatus.

OBJECTIVE: To determine the efficacy of chlorfenapyr against Anopheles arabiensis and Culex quinquefasciatus in East Africa and to identify effective dosages for net treatment in comparison with the commonly used pyrethroid deltamethrin. METHODS: Chlorfenapyr was evaluated on bed nets in experimental huts against A. arabiensis and C. quinquefasciatus in Northern Tanzania, at application rates of 100-500 mg/m(2). RESULTS: In experimental huts, mortality rates in A. arabiensis were high (46.0-63.9%) for all dosages of chlorfenapyr and were similar to that of deltamethrin-treated nets. Mortality rates in C. quinquefasciatus were higher for chlorfenapyr than for deltamethrin. Despite a reputation for being slow acting, >90% of insecticide-induced mortality in laboratory tunnel tests and experimental huts occurred within 24 h, and the speed of killing was no slower than for deltamethrin-treated nets. CONCLUSIONS: Chlorfenapyr induced low irritability and knockdown, which explains the relatively small reduction in blood-feeding rate. Combining chlorfenapyr with a more excito-repellent pyrethroid on bed nets for improved personal protection, control of pyrethroid-resistant mosquitoes and pyrethroid resistance management would be advantageous.

Community knowledge, attitude and practice towards sexually transmitted diseases and HIV infection in Biharamulo and Muleba districts in Kagera Region, Tanzania.

The study was conducted to determine knowledge, attitude and practice towards Sexually Transmitted Diseases and HIV infections among communities in Biharamulo and Muleba districts, Kagera Tanzania. A total of 915 study participants were recruited and most of them (96.3%) knew that there are diseases which could be transmitted through sexual contact. Seventy one percent of participants thought STDs could be acquired through sharing a towel while fifty percent thought HIV could be transmitted through insect bites. Eighty five percent of school pupils who participated in the study reported to have been taught about AIDS and less than 30% on sex and pregnancy. Sixty three percent of study participants were of the opinion that a girl or woman should not refuse to have sex after being given a gift, and having sex with an elder partner was thought to be acceptable by almost fifty percent of participants. Over 50% percent of interviewees thought a girl or woman should not refuse to have sex with their friends. Although 99% of interviewees reported to have ever heard about condoms, only 28% reported to have ever used them irrespective of been affordable. Most schoolboys and about 50% of schoolgirls reported to have experienced sex by the time of the study. Thirty eight percent of girls reported to have first sex at the age of 14 years. Nine percent of the participants who reported to have experienced sex were forced to do so. Knowledge regarding STDs and HIV/AIDS was high among participants, but a sizeable proportion report misconception on transmission of STDs/HIV such as through sharing a towel and insect bites. Therefore it is recommended that S&RH intervention programme should address these misconceptions in order to match knowledge and practice, and achieve the intended objectives.

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

Has the HIV Epidemic in Rural Mwanza; Tanzania Reached a Plateau?

Data from studies in Mwanza Region in Tanzania suggest stabilising HIV prevalence. The objective was to determine the factors that may have contributed to the relatively stable pattern of the HIV prevalence observed in the comparison communities of the Mwanza STD treatment trial in rural Mwanza Region; Tanzania between 1991 and 2001. Socio-demographic; sexual behaviour and HIV prevalence data in two surveys conducted 10 years apart in the same communities using similar sampling schemes were compared. The age standardised HIV prevalence was 3.8(95CI: 3.2-4.6) in 1991 and 4.3(95CI: 2.8-6.4) in 2001 for males (Z= - 0.56; P= 0.58); and 4.5(95CI: 3.8-5.3) in 1991 and 3.9(95CI: 2.6-5.6) in 2001 for females (Z= 0.64; P= 0.52). Participants in the 2001 survey reported significantly fewer lifetime and recent sexual partners (12 months); Sexually Transmitted disease syndromes (12 months) and significantly more condom use at last sex with casual partners than those in the 1991 behaviour survey. We conclude that STD/ HIV infection prevention activities in rural Mwanza may be responsible for changes in risky sexual behaviour and have successfully impeded the spread of HIV infection. These activities should therefore be enhanced to reduce HIV incidence even further. In addition; modelling studies are needed to assess whether mobility of HIV infected people out of rural communities may stabilise the prevalence of the HIV infection in the general populations

Spatial and temporal variation in malaria transmission in a low endemicity area in northern Tanzania.

BACKGROUND: Spatial and longitudinal monitoring of transmission intensity will allow better targeting of malaria interventions. In this study, data on meteorological, demographic, entomological and parasitological data over the course of a year was collected to describe malaria epidemiology in a single village of low transmission intensity. METHODS: Entomological monitoring of malaria vectors was performed by weekly light trap catches in 10 houses. Each house in the village of Msitu wa Tembo, Lower Moshi, was mapped and censused. Malaria cases identified through passive case detection at the local health centre were mapped by residence using GIS software and the incidence of cases by season and distance to the main breeding site was calculated. RESULTS: The principle vector was Anopheles arabiensis and peak mosquito numbers followed peaks in recent rainfall. The entomological inoculation rate estimated was 3.4 (95% CI 0.7-9.9) infectious bites per person per year. The majority of malaria cases (85/130) occurred during the rainy season (chi2 = 62,3, p < 0.001). Living further away from the river (OR 0.96, CI 0.92-0.998, p = 0.04 every 50 m) and use of anti-insect window screens (OR 0.65, CI 0.44-0.94, p = 0.023) were independent protective factors for the risk of malaria infection. Children aged 1-5 years and 5-15 years were at greater risk of clinical episodes (OR 2.36, CI 1.41-3.97, p = 0.001 and OR 3.68, CI 2.42-5.61, p < 0.001 respectively). CONCLUSION: These data show that local malaria transmission is restricted to the rainy season and strongly associated with proximity to the river. Transmission reducing interventions should, therefore, be timed before the rain-associated increase in mosquito numbers and target households located near the river.

Entomological evaluation of malaria vectors at different altitudes in Hai district, northeastern Tanzania.

Entomological monitoring in four villages situated along an altitude transect in the Hai District of Northeastern Tanzania identified Anopheles arabiensis Patton as the principal vector of malaria and detected seasonal changes in vector behavior. Over a 13-mo sampling period, 10,557 mosquitoes were collected with CDC light traps, pyrethrum spray catches, and pit traps of which 5,969 (56.5%) wereAn. arabiensis, 762 (7.2%) wereAnopheles funestus Giles s.l., 3,578 (33.9%) were culicines, and 248 (2.3%) were nonvector anophelines. Vector densities declined rapidly with increasing altitude, demonstrating a 50% decrease in annual human biting rate for every 86-m rise in altitude. Light traps were found to be more efficient than spray catches for the collection of An. arabiensis. This observation was attributed to increased exophily of this species, most notably in the wet season, and is supported by seasonal changes in the human blood index and fed/gravid ratio. These results indicate that spray catches may underestimate the abundance of exophilic vectors such as An. arabiensis and that entomological monitoring may require more than one collection method, especially at low vector densities. The annual entomological inoculation rate (EIR) decreased sharply with increasing altitude, with large variation around the estimate at low vector densities. Increased transmission because of unpredictable short rains at low altitudes and spatial clustering of infective mosquitoes may contribute to elevated EIR estimates.

Evaluation of the effectiveness of a clean delivery kit intervention in preventing cord infection and puerperal sepsis among neonates and their mothers in rural Mwanza Region, Tanzania.

A study was carried out in Misungwi and Kwimba Districts, Tanzania to determine the effectiveness of clean delivery kits in preventing cord infection and puerperal sepsis and to provide qualitative information on community acceptability, correct use, and appropriateness of the kits. This study involved pregnant women aged 18-45 years old. In the delivery kit intervention population, the Maternal and Child Health Aide (MCHA) assigned to the health facility provided pregnant mothers with a clean delivery kit on their first antenatal visit. She explained how to use each of the kit components, with the aid of pictorial instructions included in the kit. The pregnant mothers were asked to convey the information to whoever assisted them during delivery. The MCHA also gave them health education based on the principles of the "six cleans" recognized by WHO (i.e., clean hands, clean perineum, clean delivery surface, clean cord cutting and tying instruments, clean cutting surface). Women received the clean delivery kit free of charge in accordance with the randomised stepped-wedge design schedule. During the first week following delivery, the Village Health Workers (VHWs) from both the intervention and control groups made two visits to the households of mothers who had delivered. They administered questionnaire about delivery to mother and birth attendant. During the two scheduled postpartum visits, those who were suspected to have puerperal sepsis or cord infection of the baby were referred to the health facility clinician for confirmation. Results indicated that use of clean delivery kit had a positive effect on reducing both cord infection and puerperal sepsis. The use of a clean home delivery kit coupled with an educational intervention about the "six cleans" had a significant effect on reducing the incidence of cord infection and puerperal sepsis among women enrolled in the study. In low resource settings where home birth is common and clean delivery supplies are scarce, disposable kits can be made available through health clinics, markets, pharmacies or other channels to help reduce rates of infection.