Bilali KABULA - Academia.edu (original) (raw)

Papers by Bilali KABULA

Background Tanzania has made remarkable progress in reducing malaria burden and aims to transitio... more Background Tanzania has made remarkable progress in reducing malaria burden and aims to transition from malaria control to sub-national elimination. In 2013, electronic weekly and monthly reporting platforms using the District Health Information System 2 (DHIS2) were introduced. Weekly reporting was implemented through the mobile phone-based Integrated Disease Surveillance and Response (eIDSR) platform and progressively scaled-up from 67 to 7,471 (100%) public and private health facilities between 2013 and 2020. This study describes the roll-out and large-scale implementation of eIDSR and compares the consistency between weekly eIDSR and monthly DHIS2 malaria indicator data reporting, including to assess its usefulness for malaria outbreak detection and case-based surveillance (CBS) in low transmission areas. Methods The indicators included in the analysis were number of patients tested for malaria, number of confirmed malaria cases, and clinical cases (treated presumptively for mal...

Bulletin of Animal Health and Production in Africa, 2008

A study involving 105 smallholder dairy farmers was conducted in Kibaha and Morogoro districts, T... more A study involving 105 smallholder dairy farmers was conducted in Kibaha and Morogoro districts, Tanzania to characterise husbandry practices, milk production constraints; and farmers\' knowledge on milk-borne zoonoses. About 50% of the farmers in Kibaha (n=57) and 60% in Morogoro (n=48) were employed in formal public and private sectors, and hired labour while only 16.5% depended entirely on dairy farming. The average milk production was 5.9 litres/cow/day. Seventy-two percent of the farmers in Kibaha and 83.3% in Morogoro practised stall-feeding while others either tethered or herded the animals. Dairy production constraints included animal diseases; shortage of feeds, water and markets for milk; lack of animal breeding services and shortage of capital. The major cattle diseases were trypanosomosis, East Coast fever, anaplasmosis and mastitis. Only 14% of the farmers were aware of subclinical mastitis, and 67% of them were aware of milk-borne zoonoses especially tuberculosis while only 10% farmers knew about brucellosis. On a mene une etude portant sur 105 petites exploitations laitieres dans les districts de Kibaha et Morogoro en Tanzanie, en vue de determiner les modes d\'elevage, la production laitiere, les obstacles rencontres et la connaissance des eleveurs sur les zoonoses d\'origine laitiere. Environ 50% des eleveurs a Kibaha (n = 57) et 60% a Morogoro (n = 48) etaient employes dans les secteurs public et prive ; seuls 16,5% dependaient entierement de l\'elevage laitier. La production moyenne de lait etait de 5,9 litres/vache/jour. 72% des eleveurs a Kibaha et 83,3% a Morogoro avaient recours a l\'alimentation a l\'etable, tandis que les autres attachaient leur betail au piquet ou gardaient leurs animaux. Les entraves a la production laitiere etaient les suivantes : les maladies animales, la penurie d\'aliments et d\'eau, l\'absence de marches pour ecouler le lait, l\'absence de services de reproduction et le manque de capital. Les principales maladies bovines etaient : la trypanosomose, la fievre de la cote-Est, l\'anaplasmose et la mammite. Seuls 14% des eleveurs connaissaient la mammite infraclinique, parmi lesquels 67% etaient au courant des zoonoses d\'origine laitiere, notamment la tuberculose, et 10% connaissaient la brucellose. Bulletin of Animal Health and Production in Africa Vol. 54 (4) 2006: pp. 286-297

Tanzania Journal of Health Research, 2009

Malaria Journal

Background Insecticide resistance is a serious threat to the continued effectiveness of insectici... more Background Insecticide resistance is a serious threat to the continued effectiveness of insecticide-based malaria vector control measures, such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). This paper describes trends and dynamics of insecticide resistance and its underlying mechanisms from annual resistance monitoring surveys on Anopheles gambiae sensu lato (s.l.) populations conducted across mainland Tanzania from 2004 to 2020. Methods The World Health Organization (WHO) standard protocols were used to assess susceptibility of the wild female An. gambiae s.l. mosquitoes to insecticides, with mosquitoes exposed to diagnostic concentrations of permethrin, deltamethrin, lambdacyhalothrin, bendiocarb, and pirimiphos-methyl. WHO test papers at 5× and 10× the diagnostic concentrations were used to assess the intensity of resistance to pyrethroids; synergist tests using piperonyl butoxide (PBO) were carried out in sites where mosquitoes were found to be re...

Efforts to achieve malaria elimination need to consider both falciparum and non-falciparum infect... more Efforts to achieve malaria elimination need to consider both falciparum and non-falciparum infections. The prevalence and geographic distribution of four Plasmodium species were determined by real-time PCR using dried blood spots collected during the 2017 School Malaria Parasitological Survey of eight regions of Tanzania. Among 3,456 schoolchildren, 22% had P. falciparum, 24% P. ovale spp., 4% P. malariae, and 0.3% P. vivax. Ninety-one percent of P. ovale infections had very low parasite densities, based on amplification at later cycle thresholds. Sixty-four percent of P. ovale infections were single-species, and 35% of these were detected in low malaria endemicity regions. P. malariae infections were predominantly co-infections with P. falciparum (73%). P. vivax was largely detected in northern and eastern regions. Overall, 43% of children with P. falciparum were co-infected with at least one non-falciparum species. A large, previously under-appreciated burden of P. ovale spp. infe...

Malaria Journal, 2022

Background Transmission of malaria in sub-Saharan Africa has become increasingly stratified follo... more 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 o...

Abstract: In Sub Saharan Africa where most of the malaria cases and deaths occur, members of the ... more Abstract: In Sub Saharan Africa where most of the malaria cases and deaths occur, members of the Anopheles gambiae species complex and Anopheles funestus species group are the important malaria vectors. Control efforts against these vectors in Tanzania like in most other Sub Saharan countries have failed to achieve the set objectives of eliminating transmission due to scarcity of information about the enormous diversity of Anopheles mosquito species and their susceptibility status to insecticides used for malaria vector control. Understanding the diversity and insecticide susceptibility status of these vectors and other factors relating to their importance as vectors (such as malaria transmission dynamics, vector biology, ecology, behaviour and population genetics) is crucial to developing a better and sound intervention strategies that will reduce man-vector contact and also manage the emergency of insecticide resistance early and hence a success in malaria control. The objective o...

East African Health Research Journal, Nov 23, 2018

Background: Insecticide-treated nets (ITNs) are highly effective in reducing morbidity and mortal... more Background: Insecticide-treated nets (ITNs) are highly effective in reducing morbidity and mortality from malaria. However, it is widely accepted that ITNsif not re-treatedlose their effectiveness with time and eventually need to be replaced. This study sought to determine the social, ethical, and cultural issues related to the lifecycle of ITNs, which includes net ownership, usage, maintenance, reuse, recycling, disposal, and replacement. Methods: In this qualitative study, conducted in the districts of Mtwara Rural, Kilombero, and Muheza, Tanzania, we collected information about bed nets, including usage habits, types, treatment status, materials used, brands, acquisition sources, and perceptions thereof. We conducted 23 key informant interviews and 20 focus group discussions with village leaders, other influential people in the community, and district health-care personnel. Results: ITNs were deemed acceptable and used by most community members in the participating communities. Alternative uses and disposal practices of used bed nets were also common among community members; however, participants had limited knowledge regarding the health and environmental risks associated with these practices. Most participants did not perceive bed net recycling as a sustainable option. Recycling was considered feasible, however, if effective infrastructure for collection and disposal could be established. Poverty was identified as a major driving force towards alternative uses of bed nets. Financial constraints also meant that not all household members were able to sleep under bed nets; pregnant mothers, children under 5 years old, and the elderly were prioritised. Conclusion: Our findings may inform the National Malaria Control Programme and other stakeholders as they develop country-specific and environmentally friendly bed net replacement strategies. Appropriate strategies will help ensure sustained protection of vulnerable populations against malaria, while considering local social, ethical, and cultural issues related to the recovery of bed nets. Insecticide-Treated Net Lifecycle Management in Tanzania www.eahealth.org

Rwanda Journal, 2015

Background: The National Institute for Medical Research, Amani centre, in collaboration with Nati... more Background: The National Institute for Medical Research, Amani centre, in collaboration with National Malaria Control Programme, has been conducting annual insecticide resistance surveillance since 1999, aimed at early detection of resistance to insecticides used for malaria control in Tanzania. The Standard WHO method for larvae collection and rearing were used but challenges and limitations were encountered. For example rearing the larvae and adult mosquitoes using the Standard WHO method experienced 100% mortality for larvae; and adults in three days. The researchers therefore made modifications to the Standard WHO method to create suitable tools for the field environment. Methods: A ladle was created from an empty water bottle in which an oval hole longitudinally cut halfway from the bottom. Instead of using TetraMin as mosquito larval food, green algae were collected from mosquito breeding sites and used as larval food. Improvised heater of charcoal stoves and humidifier of wet fabric such as "Kanga" and "Kitenge" were also used. Results and conclusion: There was 90% larval survival, adult mosquito survived much better and the scientists had a total of 467 mosquitoes to run the insecticide susceptibility tests. Innovative ways are necessary under field conditions for mosquito breeding in susceptibility studies.

In recent years malaria parasites have developed resistance to the most commonly used antimalaria... more 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. Seventy‐seven percent (4457/8933) agreed to have the investigator entry into their houses and verify the 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%) 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 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…

Tanzania Journal of Health Research, 2012

In Sub Saharan Africa where most of the malaria cases and deaths occur, members of the Anopheles ... more In Sub Saharan Africa where most of the malaria cases and deaths occur, members of the Anopheles gambiae species complex and Anopheles funestus species group are the important malaria vectors. Control efforts against these vectors in Tanzania like in most other Sub Saharan countries have failed to achieve the set objectives of eliminating transmission due to scarcity of information about the enormous diversity of Anopheles mosquito species and their susceptibility status to insecticides used for malaria vector control. Understanding the diversity and insecticide susceptibility status of these vectors and other factors relating to their importance as vectors (such as malaria transmission dynamics, vector biology, ecology, behaviour and population genetics) is crucial to developing a better and sound intervention strategies that will reduce man-vector contact and also manage the emergency of insecticide resistance early and hence a success in malaria control. The objective of this review was therefore to obtain the information from published and unpublished documents on spatial distribution and composition of malaria vectors, key features of their behaviour, transmission indices and susceptibility status to insecticides in Tanzania. All data available were collated into a database. Details recorded for each data source were the locality, latitude/longitude, time/period of study, species, abundance, sampling/collection methods, species identification methods, insecticide resistance status, including evidence of the kdr allele, and Plasmodium falciparum sporozoite rate. This collation resulted in a total of 368 publications, encompassing 806,273 Anopheles mosquitoes from 157 georeferenced locations being collected and identified across Tanzania from 1950s to 2010. Overall, the vector species most often reported included An. gambiae complex (66.8%), An. funestus complex (21.8%), An. gambiae s.s. (2.1%) and An. arabiensis (9%). A variety of sampling/collection and species identification methods were used with an increase in molecular techniques in recent decades. Only 32.2% and 8.4% of the data sets reported on sporozoite analysis and entomological inoculation rate (EIR), respectively which highlights the paucity of such important information in the country. Studies demonstrated efficacy of all four major classes of insecticides against malaria vectors in Tanzania with focal points showing phenotypic resistance. About 95% of malaria entomological data was obtained from northeastern Tanzania. This shows the disproportionate nature of the available information with the western part of the country having none. Therefore it is important for the country to establish entomological surveillance system with state of the art to capture all vitally important entomological indices including vector bionomics in areas of Tanzania where very few or no studies have been done. This is vital in planning and implementing evidence based malaria vector control programmes as well as in monitoring the current malaria control interventions.

Tanzania Journal of Health Research, 2011

Malaria is endemic in Ghana as in most countries of sub-Saharan Africa. This study was conducted ... more Malaria is endemic in Ghana as in most countries of sub-Saharan Africa. This study was conducted to characterize Anopheles gambiae s.l. and determine pyrethroid resistance profiles relative to physicochemical properties of breeding habitats in Accra, Ghana. Eight aquatic habitats containing Anopheles larvae were identified and from each habitat, larvae and water were sampled. Adult An. gambiae reared from larvae were morphologically identified and tested for permethrin (0.75%) and deltamethrin (0.05%) resistance using WHO bioassay method. An. gambiae s.s. found were identified to their molecular levels and kdr mutation detected using PCR-based methods. Twenty-nine physicochemical parameters of each water sample were measured and their levels connected with pyrethroid resistance and proportions of An. gambiae s.s. molecular forms in habitats. A total of 2,257 mosquitoes were morphologically identified as An. gambiae s.l. and all 224 processed for PCR were identified as An. gambiae s.s., of which 56.46% and 43.54% were M and S-forms, respectively. Both forms occurred in sympatry in all larval habitats and no S/M hybrids were detected. However, M-form larvae were in high proportion in polluted habitats than the S-form. An. gambiae s.s. was highly resistant to both deltamethrin and permethrin with mortality rates of 42.98-70.0% and 6.5-20.0% respectively. The frequency of kdr mutation was 60.5 % (n=195). This mutation occurred in both S and M-forms, but was mainly associated with the S-form (X 2 =10.92, df =1, P=0.001). Carbonate and pH were both selected in discriminant function analysis as best predictors of high proportion of M-form in the habitats. The adaptation of An. gambiae s.s. in polluted aquatic habitats coupled with occurrence of insecticide resistance is quite alarming particularly for urban malaria control and needs further exploration in a wider context.

Parasites & Vectors, 2014

Background: Pyrethroid resistance has been slower to emerge in Anopheles arabiensis than in An. g... more Background: Pyrethroid resistance has been slower to emerge in Anopheles arabiensis than in An. gambiae s.s and An. funestus and, consequently, studies are only just beginning to unravel the genes involved. Permethrin resistance in An. arabiensis in Lower Moshi, Tanzania has been linked to elevated levels of both P450 monooxygenases and β-esterases. We have conducted a gene expression study to identify specific genes linked with metabolic resistance in the Lower Moshi An. arabiensis population. Methods: Microarray experiments employing an An. gambiae whole genome expression chip were performed on An. arabiensis, using interwoven loop designs. Permethrin-exposed survivors were compared to three separate unexposed mosquitoes from the same or a nearby population. A subsection of detoxification genes were chosen for subsequent quantitative real-time PCR (qRT-PCR). Results: Microarray analysis revealed significant over expression of 87 probes and under expression of 85 probes (in pairwise comparisons between permethrin survivors and unexposed sympatric and allopatric samples from Dar es Salaam (controls). For qRT-PCR we targeted over expressed ABC transporter genes (ABC '2060'), a glutathione-Stransferase, P450s and esterases. Design of efficient, specific primers was successful for ABC '2060'and two P450s (CYP6P3, CYP6M2). For the CYP4G16 gene, we used the primers that were previously used in a microarray study of An. arabiensis from Zanzibar islands. Over expression of CYP4G16 and ABC '2060' was detected though with contrasting patterns in pairwise comparisons between survivors and controls. CYP4G16 was only up regulated in survivors, whereas ABC '2060' was similar in survivors and controls but over expressed in Lower Moshi samples compared to the Dar es Salaam samples. Increased transcription of CYP4G16 and ABC '2060' are linked directly and indirectly respectively, with permethrin resistance in Lower Moshi An. arabiensis. Conclusions: Increased transcription of a P450 (CYP4G16) and an ABC transporter (ABC 2060) are linked directly and indirectly respectively, with permethrin resistance in Lower Moshi An. arabiensis. Our study provides replication of CYP4G16 as a candidate gene for pyrethroid resistance in An. arabiensis, although its role may not be in detoxification, and requires further investigation.

Journal of Veterinary Medicine Series B, 2004

A study was carried out to establish the prevalence and determinants of mastitis and milk-borne z... more A study was carried out to establish the prevalence and determinants of mastitis and milk-borne zoonoses in smallholder dairy farms in Kibaha and Morogoro districts (Tanzania). A total of 57 herds comprising 114 milking cows in Kibaha and 48 herds consisting of 96 milking animals in Morogoro were included in the study. A questionnaire survey was used to assess the socioeconomic determinants of mastitis, whereas California mastitis test (CMT) and microbiological assessment of milk was carried out to establish the status of mastitis and responsible aetiological agents. Seroconversion for brucellosis was evaluated using enzyme-linked immunosorbent assay (ELISA). Animals were also tuberculin-tested using a single comparative intradermal method and milk samples were cultured for isolation of Mycobacterium species. Based on CMT, the cow-based prevalence of subclinical mastitis was 82.4% in Kibaha and 62.4% in Morogoro. Of the 919-quarter milk samples cultured, 8.2% were positive for aerobic bacteria with predominant isolates being Staphylococcus epidermidis (2.8%), Staph. aureus (1.7%), Streptococcus agalactiae (1.2%) and Staph. intermedius (1.1%). There was a strong association between CMT positivity and bacteriological isolation [relative risk (RR) ¼ 2.60; P ¼ 0.02]. Fungal growth was observed in 21.8% (n ¼ 881) of the samples and the isolates were yeast (19.2%), Mucor (2.5%) and Aspergillus (0.1%). Bucket feeding of calves was associated with increased risk of a quarter being CMT positive (RR ¼ 1.24; P ¼ 0.000), while residual calf suckling was associated with decreased risk of positivity (RR ¼ 0.86; P ¼ 0.015). Earth floor was associated with increased risk of CMT positivity at quarter level (RR ¼ 1.13; P ¼ 0.041) and Jersey breed was identified as a risk factor to mastitis. The prevalence of bovine tuberculosis was 0.4% (n ¼ 259) and 1.7% (n ¼ 181) in Kibaha and Morogoro, respectively. Similarly, the prevalence of brucellosis was 1% (n ¼ 208) in Kibaha and 1.9% (n ¼ 104) in Morogoro. Findings from this study have demonstrated a high prevalence of subclinical mastitis and existence of health risks to milk consumers despite the low prevalence of tuberculosis and brucellosis in the study herds.

Tropical Medicine & International Health, 2012

Tropical Medicine & International Health, 2014

objective Insecticide resistance molecular markers can provide sensitive indicators of resistance... more objective Insecticide resistance molecular markers can provide sensitive indicators of resistance development in Anopheles vector populations. Assaying these makers is of paramount importance in the resistance monitoring programme. We investigated the presence and distribution of knock-down resistance (kdr) mutations in Anopheles gambiae s.l. in Tanzania. methods Indoor-resting Anopheles mosquitoes were collected from 10 sites and tested for insecticide resistance using the standard WHO protocol. Polymerase chain reaction-based molecular diagnostics were used to genotype mosquitoes and detect kdr mutations. results The An. gambiae tested were resistance to lambdacyhalothrin in Muheza, Arumeru and Muleba. Out of 350 An. gambiae s.l. genotyped, 35% were An. gambiae s.s. and 65% An. arabiensis. L1014S and L1014F mutations were detected in both An. gambiae s.s. and An. arabiensis. L1014S point mutation was found at the allelic frequency of 4-33%, while L1014F was at the allelic frequency 6-41%. The L1014S mutation was much associated with An. gambiae s.s. (v 2 = 23.41; P < 0.0001) and L1014F associated with An. arabiensis (v 2 = 11.21; P = 0.0008). The occurrence of the L1014S allele was significantly associated with lambdacyhalothrin resistance mosquitoes (Fisher exact P < 0.001). conclusion The observed co-occurrence of L1014S and L1014F mutations coupled with reports of insecticide resistance in the country suggest that pyrethroid resistance is becoming a widespread phenomenon among our malaria vector populations. The presence of L1014F mutation in this East African mosquito population indicates the spreading of this gene across Africa. The potential operational implications of these findings on malaria control need further exploration. keywords kdr, L1014S, L1014F, insecticide resistance, Anopheles gambiae, Tanzania This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Parasites & Vectors, 2013

Background: The emergence of pyrethroid resistance in the malaria vector, Anopheles arabiensis, t... more Background: The emergence of pyrethroid resistance in the malaria vector, Anopheles arabiensis, threatens to undermine the considerable gains made towards eliminating malaria on Zanzibar. Previously, resistance was restricted to the island of Pemba while mosquitoes from Unguja, the larger of the two islands of Zanzibar, were susceptible. Here, we characterised the mechanism(s) responsible for resistance on Zanzibar using a combination of gene expression and target-site mutation assays. Methods: WHO resistance bioassays were conducted using 1-5d old adult Anopheles gambiae s.l. collected between 2011 and 2013 across the archipelago. Synergist assays with the P450 inhibitor piperonyl-butoxide were performed in 2013. Members of the An. gambiae complex were PCR-identified and screened for target-site mutations (kdr and Ace-1). Gene expression in pyrethroid resistant An. arabiensis from Pemba was analysed using whole-genome microarrays. Results: Pyrethroid resistance is now present across the entire Zanzibar archipelago. Survival to the pyrethroid lambda-cyhalothrin in bioassays conducted in 2013 was 23.5-54.3% on Unguja and 32.9-81.7% on Pemba. We present evidence that resistance is mediated, in part at least, by elevated P450 monoxygenases. Whole-genome microarray scans showed that the most enriched gene terms in resistant An. arabiensis from Pemba were associated with P450 activity and synergist assays with PBO completely restored susceptibility to pyrethroids in both islands. CYP4G16 was the most consistently over-expressed gene in resistant mosquitoes compared with two susceptible strains from Unguja and Dar es Salaam. Expression of this P450 is enriched in the abdomen and it is thought to play a role in hydrocarbon synthesis. Microarray and qPCR detected several additional genes putatively involved in this pathway enriched in the Pemba pyrethroid resistant population and we hypothesise that resistance may be, in part, related to alterations in the structure of the mosquito cuticle. None of the kdr target-site mutations, associated with pyrethroid/DDT resistance in An. gambiae elsewhere in Africa, were found on the islands. Conclusion: The consequences of this resistance phenotype are discussed in relation to future vector control strategies on Zanzibar to support the ongoing malaria elimination efforts on the islands.

Emerging Infectious Diseases, 2012

Malaria control depends on mosquito susceptibility to insecticides. We tested Anopheles gambiae m... more Malaria control depends on mosquito susceptibility to insecticides. We tested Anopheles gambiae mosquitoes from Côte d'Ivoire for resistance and screened a subset for target site mutations. Mosquitoes were resistant to insecticides of all approved classes. Such complete resistance, which includes exceptionally strong phenotypes, presents a major threat to malaria control.