\ud Detection and Monitoring of Insecticide Resistance in Malaria Vectors in Tanzania Mainland\ud

\ud Vector control is a major component of the global strategy for malaria control which aims to prevent parasite transmission mainly through interventions targeting adult Anopheline vectors. Insecticide treated nets (ITNs) and indoor residual spraying (IRS) are the cornerstone of malaria vector control programmes. These major interventions in most cases use pyrethroid insecticides which are also used for agricultural purposes. With widespread development of resistance to pyrethroid insecticides in malaria vectors raises concern over the sustainability of insecticide-based interventions for malaria control. Therefore, close monitoring of performance of the insecticides against malaria vectors is essential for early detection and\ud management of resistance. To measure pyrethroid susceptibility in populations of malaria vectors in Tanzania and to test the efficacy of LLINs/ITNs and insecticide residues on sprayed wall substrates in the IRS operation areas. In 2011 the National Institute for Medical Research (NIMR) in collaboration with National Malaria Control Programme (NMCP) conducted large scale surveillance to determine the countrywide susceptibility levels of malaria vectors to insecticides used for both public health and agricultural purposes. Anopheles gambiae Giles s.l. were collected during national surveys and samples of LLINs/ITNs in the 14 sentinel sites and houses from the IRS areas were randomly selected for bioassays to test the efficacy and insecticide residual effects on sprayed wall substrates respectively. Wild adult mosquitoes for susceptibility testing were collected by resting catches indoors. Net traps (outdoors and indoors) were set up to enhance catches. WHO Susceptibility kits were used to test for resistance status using test papers: Lambdacyhalothrin 0.05%, Deltamethrin 0.05%, Permethrin 0.75%, DDT 4%, Propoxur 0.1% and Fenitrothion 1%. The quality of the test paper was checked against a laboratory susceptible An. gambiae Kisumu strain. Knockdown effect and mortality were measured in standard WHO susceptibility tests and cone bio-efficacy tests. Whereas, con bioassays on treated walls and ITNs were conducted using the laboratory susceptible An. gambiae Kisumu strain. The results from the surveillance recorded continued susceptibility of malaria vectors to commonly used insecticides. However, there were some isolated cases of resistance and/or reduced susceptibility to pyrethroid insecticides which may not compromise the current vector control interventions in the country. Anopheles gambiae s.l. showed resistance (15-28%) to each of the pyrethroids and to DDT but not to Organophosphates (Propoxur 0.1%), and Carbamates (Fenitrothion 1%). The information obtained from this surveillance is expected to be used to guide the National Malaria Control Programme on the rational selection of insecticides for malaria vector control and for the national mitigation plans for management and containment of malaria vector resistance in the country. The current observation warrants more vigilant monitoring of the susceptibility of malaria mosquitoes to commonly used insecticides in areas found with resistance and/or reduced levels of susceptibility of malaria vectors to insecticides, particularly in areas with heavy agricultural and/or public health use of insecticides where resistance is likely to develop. The current survey covered malaria vectors only and not the non malaria vectors (nuisance) mosquitoes such as Culex. Similar monitoring of insecticide susceptibility of this non malaria vectors may be needed to ensure public motivation for sustained use of ITNs/LLINs in the country. The surveillance leading to these results received funding from PMI/USAID through RTI International with Sub Agreement Number 33300212555.\u

Mosquito Net Coverage and Utilisation for Malaria\ud Control in Tanzania\ud

\ud In recent years malaria parasites have developed resistance to the most commonly used antimalarial drugs in Tanzania, posing a major challenge for its control. This has led to frequent changes of malaria treatment guidelines, more recently to expensive, yet more effective arthemether/lumefantrine. The use of insecticide treated mosquito nets (ITNs) and long lasting nets (LLINs) in Tanzania has increased slowly over the past few years. Despite the introduction of a voucher scheme to the vulnerable groups, the proportion of households with at least an ITN/LLIN in the country has not been able to achieve the Abuja Declaration of 60% net coverage. Statistics available on the utilisation of nets do not provide a good estimate of the coverage, because of the different study design used to collect the information. This survey was carried out in 21 districts of Tanzania to determine the coverage and utilisation of insecticide treated nets to provide baseline information of the net requirement to cover every sleeping bed in the country. Specifically, this study aimed to (i) determine the ITN coverage by and its distribution in the country; and (ii) determine knowledge, attitudes and practice of the householders as regards to malaria prevention and control Twenty one districts (one from each region) of Mainland Tanzania were selected for the survey. Selection of the district was random. In each district, two wards were selected, one urban (within the district capital) and one rural or sub‐urban. Households were selected randomly using a table of random numbers. At household level, the head or any adult who represented the head of household was interviewed. A structured pre‐tested questionnaire was used to collect information on knowledge, attitude and practices in malaria control, with emphasis on mosquito net ownership and utilisation. Of the 9549 targeted households, 9166 (96%) participated in the survey. Majority of the respondents (76.8%) were from rural district.The mean household size was 3.9 persons. On average, children <5 years old accounted for 39.3% of the members of the households. Respondents with no formal education accounted for 15.8‐37.4% of the interviewees. Most of them were from Mkuranga (55%), Kigoma‐Ujiji (44.2%) and Newala (37.9%). High literate rates were observed in Arumeru and Moshi districts. The majority of the respondents knew that the mosquito is the vector of the malaria parasite (92.6‐99.4%) and infection is through a mosquito bite (92.7‐99.8%). The knowledge of respondents on malaria transmission was generally high (94.0‐99.0%). The majority of the respondents (95.2%) considered the use of mosquito nets as the most effective way of malaria prevention. However, of these, only 66.7% said to have actually used nets in their life time. Knowledge on the use of mosquito nets in the control of malaria was highest and lowest in Eastern and Central zones, respectively.\ud Seventy‐seven percent (4457/8933) agreed to have the investigator entry into their houses and verify the\ud number of nets owned. On average, 62.9% (5,785/8933) of the households had at least a mosquito net. Majority of the respondents in Northern (76.5%) and Southern (76.5%) zones owned at least a mosquito net. The lowest mosquito net ownership was observed among respondents in Western Zone (39.6%). District‐wise, net ownership was highest in Lindi (94.5%), Kyela (91.3%) Arumeru (86.1%), Ilala (83.1%)\ud and Nyamagana (80.0%). Ownership of net was very low in Kilolo (34.8%), Kigoma (36.5%) and Musoma Rural (41.3%). Of the households with nets, 74.4% were using nets all year round. A larger proportion of respondents in Kilolo (68.5%), Mpwapwa (51.9%), Songea Rural (49.2%) and Shinyanga Rural (46.3%) were only using the nets during the rainy season. Out of 9,166 households visited, 3,610 (39.3%) had at least one under five child. Of these, in 1,939 (53.7%) of the households the child slept under a mosquito net during the previous night. Use of nets in children <5 years was most common in northern zone (74%); followed by eastern (66.9%) and southern zone (61.1%). Districts with the largest proportion of <5 year children sleeping under a mosquito nets were Lindi (90.0%), Kyela (85.2%), Ilala (83.2%) and Arumeru (78.2%). Only about a quarter (27%) of the children <5% in western zone were sleeping under a mosquito net. Lowest net coverage for <5 year was in Kigoma (22.7%), Kilolo (25%) and Bukoba Rural (31.2%). A total of 5,785 (62.9%) owned at least a mosquito net. Of these, 4,219 and 1,566 were from the rural and urban districts, respectively. More households in the urban districts (73.4%) than rural districts (59.7%) owned at least a mosquito net. Likewise, there were more households (64.9%) in the urban districts with <5years children sleeping under mosquito nets than in the rural districts (50.4%). More households in urban (32.8%) than in rural districts (25.1%) had at least one insecticide treated net. The number of households with mosquito nets enough for all members of the households ranged from 18.9% (in Urambo) to 37.4% (in Hanang). Households with at least 50% or more occupants using mosquito nets ranged from 16.4% (in Urambo) to 42.8% (in Arumeru). Districts with the largest proportion of ≥50% of the household members sleeping under mosquito nets were Arumeru (46.9%) and Lindi (46.7%). In Manyoni and Lindi, 3.1% and 5% of the households were found to have more nets than the number of household occupants. Only 9% (801/9196) of the households had all occupants sleeping under a mosquito net. Kyela district had about a quarter (23.9%) of the households with all occupants sleeping under nets. Only 29% of the households had at least one insecticide treated mosquito nets. All nets in 51.4% of the households surveyed were ITNs. The largest proportion of households with ITN was observed in northern zone (40.2%), with Arumeru (46%) and Hanang (44.1%) districts having the highest ITN coverage. The lowest proportion (15.5%) of households with ITN was found in the Western Zone. Districts which had the lowest ITN coverage were Musoma Rural (12.6%), Kigoma‐Ujiji (13.2%), and Shinyanga Rural (14.4%). On average, 90.7% (8,123/8,953) of the respondents would prefer using ITN than having their house sprayed with long lasting residual insecticide. More households in urban (32.8%) than in rural districts (25.1%) had at least an ITN> A total of 1939 children underfives were sleeping under mosquito net (any type). Of these, 1140 (58.8%) were using insecticide treated nets (ITN). Overall, 31.6% of the underfives slept under an insecticide treated net during the previous night. Highest coverage was reported in Kyela (47.7%), Nyamagana (47.7%) and Arumeru (46.4%). Lowest ITN in underfives was reported in Kigoma‐Ujiji (16.0%), Musoma (17.2%) and Urambo (17.7%). In Songea more underfives children were sleeping under ITN (43.6%) than in untreated nets (40.9%). Control of bedbugs, lice, fleas, mites and cockroaches was the major added advantage of using insecticide treated nets. On average, 30.8% and 19.6% of the respondents mentioned cockroach and bedbug control as the main advantage of using ITN, respectively. The majority (52.9%) preferred blue coloured net (Northern=45.6%; Central=59.2%; Eastern=56.4%; Lake= 54.4%; Southern= 60.3%, Western= 58.5%) and Southern Highlands= 49.1%). Other colour preferences were white (29.6%), green (14.1%), black (2.1%) and pink (1.2%). A strong preference for blue mosquito nets was observed among respondents in Musoma (77.3%) and Newala (75.5%) districts. On the other hand, the weakest preference (24.7%) for blue nets was observed among respondents in Arumeru district. The majority of the respondents (82%) preferred rectangular shaped net. A larger percent (61.8%) the respondents preferred to have the map of Tanzania as a national logo to identify nets distributed in the country. On average, 62.7% and 28.8% of the households in Tanzania own at least one mosquito net (any type) and insecticide treated net, respectively. Tanzania expects that ITN coverage of under fives in 2009, after the Under Five Catch‐up Campaign is complete, to be at least 80%. If this is to be achieved, there is a need for concerted effort in scaling up the distribution and demand for long lasting nets throughout the country. Moreover, the planned use of IRS in malaria control, currently considered unpopular should be accompanied by rigorous community health education to avoid resistance from household members.\u

On-farm comparison of different postharvest storage technologies for effectiveness in pest management in a maize farming system of Tanzania Central Corridor: Presentation

Seven methods for storing maize were compared with traditional practice of storing maize in polypropylene bags. Twenty farmers managed the experiment under their prevailing conditions for 30 weeks. Stored grain was assessed for damage every six weeks. The dominant storage insect pests identified were the Maize weevil (Sitophilus zeamais) and the Red flour beetle (Tribolium castaneum). There was no significant difference (F = 87.09; P &lt; 0.0001) in insect control and grain damage between hermetic storage and fumigation with insecticides. However, the insecticide treated polypropylene yarn (ZeroFly®) did not control insect infestation of grain for the experimental period under farmers’ management. Grain damage was significantly lower in hermetic storage and fumigated grain than ZeroFly® and polypropylene bags without fumigation. No significant difference in grain damage was found between airtight treatment alone and when combined with the use of insecticides. During storage, S. zeamais was predominant and could be of more economic importance than T. castaneum as far as maize damage is concerned. Even though ZeroFly®, and polypropylene bags without grain treatment did not control storage pests, farmers still prefered this cheap technology. Hermetic storage techniques can be recommended to farmers without the use of insecticides provided they are inexpensive, and the proper application of technologies is ensured.Seven methods for storing maize were compared with traditional practice of storing maize in polypropylene bags. Twenty farmers managed the experiment under their prevailing conditions for 30 weeks. Stored grain was assessed for damage every six weeks. The dominant storage insect pests identified were the Maize weevil (Sitophilus zeamais) and the Red flour beetle (Tribolium castaneum). There was no significant difference (F = 87.09; P &lt; 0.0001) in insect control and grain damage between hermetic storage and fumigation with insecticides. However, the insecticide treated polypropylene yarn (ZeroFly®) did not control insect infestation of grain for the experimental period under farmers’ management. Grain damage was significantly lower in hermetic storage and fumigated grain than ZeroFly® and polypropylene bags without fumigation. No significant difference in grain damage was found between airtight treatment alone and when combined with the use of insecticides. During storage, S. zeamais was predominant and could be of more economic importance than T. castaneum as far as maize damage is concerned. Even though ZeroFly®, and polypropylene bags without grain treatment did not control storage pests, farmers still prefered this cheap technology. Hermetic storage techniques can be recommended to farmers without the use of insecticides provided they are inexpensive, and the proper application of technologies is ensured

Evaluating malaria prevalence and land cover across varying transmission intensity in Tanzania using a cross-sectional survey of school-aged children

BACKGROUND: Transmission of malaria in sub-Saharan Africa has become increasingly stratified following decades of malaria control interventions. The extent to which environmental and land cover risk factors for malaria may differ across distinct strata of transmission intensity is not well known and could provide actionable targets to maximize the success of malaria control efforts. METHODS: This study used cross-sectional malaria survey data from a nationally representative cohort of school-aged children in Tanzania, and satellite-derived measures for environmental features and land cover. Hierarchical logistic regression models were applied to evaluate associations between land cover and malaria prevalence within three distinct strata of transmission intensity: low and unstable, moderate and seasonal, and high and perennial. RESULTS: In areas with low malaria transmission, each 10-percentage point increase in cropland cover was associated with an increase in malaria prevalence odds of 2.44 (95% UI: 1.27, 5.11). However, at moderate and higher levels of transmission intensity, no association between cropland cover and malaria prevalence was detected. Small associations were observed between greater grassland cover and greater malaria prevalence in high intensity settings (prevalence odds ratio (POR): 1.10, 95% UI: 1.00, 1.21), and between greater forest cover and reduced malaria prevalence in low transmission areas (POR: 0.74, 95% UI: 0.51, 1.03), however the uncertainty intervals of both estimates included the null. CONCLUSIONS: The intensity of malaria transmission appears to modify relationships between land cover and malaria prevalence among school-aged children in Tanzania. In particular, greater cropland cover was positively associated with increased malaria prevalence in areas with low transmission intensity and presents an actionable target for environmental vector control interventions to complement current malaria control activities. As areas are nearing malaria elimination, it is important to re-evaluate environmental risk factors and employ appropriate interventions to effectively address low-level malaria transmission

Entomological Surveillance of Behavioural Resilience and Resistance in Residual Malaria Vector Populations.

The most potent malaria vectors rely heavily upon human blood so they are vulnerable to attack with insecticide-treated nets (ITNs) and indoor residual spraying (IRS) within houses. Mosquito taxa that can avoid feeding or resting indoors, or by obtaining blood from animals, mediate a growing proportion of the dwindling transmission that persists as ITNs and IRS are scaled up. Increasing frequency of behavioural evasion traits within persisting residual vector systems usually reflect the successful suppression of the most potent and vulnerable vector taxa by IRS or ITNs, rather than their failure. Many of the commonly observed changes in mosquito behavioural patterns following intervention scale-up may well be explained by modified taxonomic composition and expression of phenotypically plastic behavioural preferences, rather than altered innate preferences of individuals or populations. Detailed review of the contemporary evidence base does not yet provide any clear-cut example of true behavioural resistance and is, therefore, consistent with the hypothesis presented. Caution should be exercised before over-interpreting most existing reports of increased frequency of behavioural traits which enable mosquitoes to evade fatal contact with insecticides: this may simply be the result of suppressing the most behaviourally vulnerable of the vector taxa that constituted the original transmission system. Mosquito taxa which have always exhibited such evasive traits may be more accurately described as behaviourally resilient, rather than resistant. Ongoing national or regional entomological monitoring surveys of physiological susceptibility to insecticides should be supplemented with biologically and epidemiologically meaningfully estimates of malaria vector population dynamics and the behavioural phenotypes that determine intervention impact, in order to design, select, evaluate and optimize the implementation of vector control measures