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Papers by Stephen Magesa

Journal of The American Mosquito Control Association, Sep 1, 2006

Research Square (Research Square), Jun 1, 2021

Tropical Medicine & International Health, Nov 1, 2004

BMC Public Health, Jul 5, 2010

Background: Muleba district in Northwestern Tanzania has experienced malaria epidemics in recent ... more Background: Muleba district in Northwestern Tanzania has experienced malaria epidemics in recent years. Community knowledge, attitudes and practices are important in enhancing disease control interventions. This study investigated determinants of malaria epidemics in the study area in relation to household knowledge, attitudes and practice on malaria. Methods: A community based cross-sectional survey involving 504 study participants was conducted between April and June 2007 using a structured questionnaire focusing on knowledge, attitudes and practices of community members in epidemic and non-epidemic villages about malaria transmission, signs and symptoms, treatment, prevention and control. Multivariate logistic regression analysis was used to assess determinants of malaria epidemics. Results: A total of 504 respondents (males = 36.9%) were interviewed. Overall, 453 (90.1%) mentioned malaria as the most important disease in the area. Four hundred and sixty four respondents (92.1%) knew that malaria is transmitted through mosquito bite. A total of 436 (86.7%), 306 (60.8%) and 162 (32.1%) mentioned fever, vomiting and loss of appetite as major symptoms/signs of malaria, respectively. Of those interviewed 328 (65.1%) remembered the recent outbreak of 2006. Of the 504 respondents interviewed, 296 (58.7%) reported that their households owned at least one mosquito net. Three hundred and ninety seven respondents (78.8%) knew insecticides used to impregnate bed nets. About two thirds (63.3%) of the respondents had at least a household member who suffered from malaria during the recent epidemic. During the 2006 outbreak, 278 people (87.2%) sought treatment from health facilities while 27 (8.5%) obtained drugs from drug shops and 10 (3.1%) used local herbs. Logistic regression analysis showed that household location and level of knowledge of cause of malaria were significant predictors of a household being affected by epidemic. Conclusions: Residents of Muleba district have high level of knowledge on malaria. However, this knowledge has not been fully translated into appropriate use of available malaria interventions. Our findings suggest that household location, ineffective usage of insecticide treated nets and knowledge gaps on malaria transmission, signs and symptoms, prevention and control predisposed communities in the district to malaria epidemics. It is important that health education packages are developed to address the identified knowledge gaps.

Acta Tropica, Jun 1, 1991

In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out.... more In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out. The people received them enthusiastically and brought their nets for re-impregnation at six monthly intervals. Bioassays showed that the insecticidal power of permethrin impregnated nets remained adequate for six months unless the nets were washed. Nets with 30 mg lambdacyhalothrin/m2 retained high insecticidal power despite washing, but this dose caused temporary cold-like symptoms in those sleeping under freshly treated dry nets. Methods by which durable bednets might be made affordable by Tanzanian villagers are discussed.

Parasitology International, Jun 1, 2009

The effect of HIV on filarial-specific antibody response before and after treatment with diethylc... more The effect of HIV on filarial-specific antibody response before and after treatment with diethylcarbamazine (DEC) was analysed by comparing two groups of Wuchereria bancrofti-infected adult individuals (positive for circulating filarial antigen) who were positive (n=15) or negative (n=21) for HIV co-infection. Prior to DEC treatment there was no significant difference in filarial-specific IgG1, IgG2, IgG4 and IgE antibody response between the HIV negative and the HIV positive group, while a five times (statistically significant) higher filarial-specific IgG3 response was observed in the HIV positive than in the HIV negative group. At 12 weeks after treatment with DEC, a significant decrease in filarial-specific IgG4 was observed in the HIV positive but not in the HIV negative group, indicating that DEC treatment had a stronger antifilarial effect in individuals co-infected with HIV. DEC treatment had no significant effect on the other classes of filarial specific antibodies, neither in the HIV negative or the HIV positive group.

Acta Tropica, Jun 1, 1991

In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out.... more In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out. The people received them enthusiastically and brought their nets for re-impregnation at six monthly intervals. Bioassays showed that the insecticidal power of permethrin impregnated nets remained adequate for six months unless the nets were washed. Nets with 30 mg lambdacyhalothrin/m2 retained high insecticidal power despite washing, but this dose caused temporary cold-like symptoms in those sleeping under freshly treated dry nets. Methods by which durable bednets might be made affordable by Tanzanian villagers are discussed.

Transactions of The Royal Society of Tropical Medicine and Hygiene, Aug 1, 2004

Examination of 1829 children from 6 primary schools in coastal Tanzania revealed overall Wucherer... more Examination of 1829 children from 6 primary schools in coastal Tanzania revealed overall Wuchereria bancrofti microfilaria (mf) and circulating filarial antigen (CFA) prevalences of 17.3% and 43.7%, respectively. A randomized double-blind field trial with a single dose of ivermectin (150-200 g/kg body weight) alone or in combination with albendazole (400 mg) was subsequently carried out among these children. Both treatment regimens resulted in a considerable decrease in mean mf intensities, with overall reductions being slightly but statistically significantly higher for the combination than for ivermectin alone. The difference in effect between the two treatment regimens was most pronounced at 6 months, whereas it was minor at 12 months after treatment. The relative effect of treatment on mean CFA units was less pronounced than on mf. For both treatment regimens, reductions in CFA intensity appeared to be higher in children who were both CFA and mf positive before treatment, which may suggest that treatment mainly affected the survival and/or production of mf, rather than the survival of adult worms. New cases of infection appeared after treatment with both regimens among the pre-treatment mf and CFA negative children. Adverse reactions were few and mild in both groups, and mainly reported from pre-treatment mf and CFA positive children. The alarmingly high prevalence of W. bancrofti infection in primary school children highlights the importance of also determining the reversibility of already acquired early lesions, and the development of new measures and strategies to specifically protect children from later developing clinical disease.

Malaria Journal, Sep 28, 2021

Background: Long-lasting efficacy of insecticide-treated nets is a balance between adhesion, rete... more Background: Long-lasting efficacy of insecticide-treated nets is a balance between adhesion, retention and migration of insecticide to the surface of netting fibres. ICON ® Maxx is a twin-sachet 'home-treatment kit' of pyrethroid plus binding agent, recommended by the World Health Organization (WHO) for long-lasting, wash-fast treatment of polyester nets. While knitted polyester netting is widely used, fine woven polyethylene netting is increasingly available and nets made of cotton and nylon are common in Africa and Asia. It is important to investigate whether ICON Maxx is able to fulfill the WHO criteria of long-lasting treatment on a range of domestic fabrics to widen the scope for malaria protection. Methods: This study was a controlled comparison of the bio-efficacy and wash-fastness of lambda-cyhalothrin CS, with or without binder, on nets made of cotton, polyethylene, nylon, dyed and undyed polyester. Evaluation compared an array of bioassays: WHO cone and cylinder, median time to knockdown and WHO tunnel tests using Anopheles mosquitoes. Chemical assay revealed further insight. Results: ICON Maxx treated polyethylene and polyester netting met the WHO cone and tunnel test bio-efficacy criteria for LLIN after 20 standardized washes. Although nylon and cotton netting failed to meet the WHO cone and cylinder criteria, both materials passed the WHO tunnel test criterion of 80% mortality after 20 washes. All materials treated with standard lambda-cyhalothrin CS without binder failed to meet any of the WHO bio-efficacy criteria within 5 washes. Conclusion: The bio-efficacy of ICON Maxx against mosquitoes on netting washed up to 20 times demonstrated wash durability on a range of synthetic polymer and natural fibres: polyester, polyethylene, nylon and cotton. This raises the prospect of making insecticide-binder kits into an effective approach for turning untreated nets, curtains, military clothing, blankets-and tents and tarpaulins as used in disasters and humanitarian emergencies-into effective malaria prevention products. It may provide a solution to the problem of reduced LLIN coverage between campaigns by converting commercially sourced untreated nets into LLINs through community or home treatment. It may also open the door to binding of non-pyrethroid insecticides to nets and textiles for control of pyrethroid resistant vectors.

Tanzania health research bulletin, Oct 21, 2011

PLOS ONE, Feb 16, 2010

Background: The importance of invasive salmonellosis in African children is well recognized but t... more Background: The importance of invasive salmonellosis in African children is well recognized but there is inadequate information on these infections. We conducted a fever surveillance study in a Tanzanian rural hospital to estimate the case fraction of invasive salmonellosis among pediatric admissions, examine associations with common co-morbidities and describe its clinical features. We compared our main findings with those from previous studies among children in sub-Saharan Africa.

Tanzania health research bulletin, Mar 26, 2012

Acta Tropica, Oct 1, 2000

The circadian periodicity of Plasmodium falciparum gametocytes in peripheral blood was analysed i... more The circadian periodicity of Plasmodium falciparum gametocytes in peripheral blood was analysed in a group of children from an holoendemic community of northeastern Tanzania. No periodicity was observed with asexual stage parasites. Gametocytes were shown to display a diurnal subperiodic pattern with a periodicity index of 31.8. Mathematical analysis of the data indicated that P. falciparum gametocytes tend to display periodicity with a peak (15:30-19:30 h) that do not coincide with the peak (00:30-03:30 h) biting activity of the local vector, Anopheles gambiae. We were thus able to show a P. falciparum gametocyte periodicity with a harmonic wave pattern, but its functional biological significance if any, is currently unknown.

Background The need to develop new products and novel approaches for malaria vector control is re... more Background The need to develop new products and novel approaches for malaria vector control is recognized as a global health priority. One approach to meeting this need has been the development of new products for indoor residual spraying (IRS) with novel active ingredients for public health. While initial results showing the impact of several of these next-generation IRS products have been encouraging, questions remain about how to best deploy them for maximum impact. To help address these questions, a 2-year cluster-randomized controlled trial to measure the impact of IRS with a microencapsulated formulation of pirimiphos-methyl (PM) in an area with high ownership of long-lasting insecticidal nets (LLINs) was conducted in a high-transmission district of central Mozambique with pyrethroid resistant vectors. Presented here are the results of the vector surveillance component of the trial. Methods The 2 year, two-armed trial was conducted in Mopeia District, Zambezia Province, Mozamb...

Additional file 1. Maximum and minimum temperature (°C) and relative humidity (%RH) during the 60... more Additional file 1. Maximum and minimum temperature (°C) and relative humidity (%RH) during the 60 minutes testing and up to 7 day holding period & % Mortality of mosquitoes tested with the negative control (WHO papers treated with 2ml of distilled water) for up to 7 days after bioassay.

Malaria morbidity and mortality rates in Sub-Saharan Africa are increasing. The scale-up of long-... more Malaria morbidity and mortality rates in Sub-Saharan Africa are increasing. The scale-up of long-lasting insecticidal nets and indoor residual spraying have been the major contributors to the decrease of malaria burden. These tools are now threatened by insecticide resistance in malaria vectors, which is spreading dramatically. After two different real-time polymerase chain reaction molecular characterizations carried out on 70 mosquitoes sampled in the locality of Elibou in southern Côte d’Ivoire, results revealed that 9 mosquitoes from Anopheles harbored the double Eastand West-African knockdown resistance coluzzi mutations. In the previous year, only 1 mosquito out of 150 sampled from 10 regions of the country had the same genotype. These results show the rapid spread of insecticide resistance in malaria vectors and highlight the urgent need to diversify the methods of vector control in order to avoid the failure of insecticide-based vector control tools which may favor malaria f...

Although pyrethroid insecticides are a promising means of controlling Anopheles malaria vectors, ... more Although pyrethroid insecticides are a promising means of controlling Anopheles malaria vectors, there is a need to monitor for resistance. It has been proposed that the results of the WHO-recommended testing method, involving exposure to impregnated paper for 1 hour, might be misleading because of knockdown during this period, and that exposure to a higher dose of pyrethroid for 2 minutes might be preferable. However, comparative tests with a susceptible and a permethrin-resistant strain of A. stephensi showed that exposure for 1 hour was at least as sensitive in detecting resistance as was the short exposure method.

Background: Indoor Residual Spray (IRS) has proven to be one of the most effective malaria vector... more Background: Indoor Residual Spray (IRS) has proven to be one of the most effective malaria vector control interventions in reducing malaria transmission mainly in areas with high transmission. With the support from the US President’s Malaria Initiative (PMI), Tanzania has gone through expansion of IRS implementation with different insecticides from one district in 2007 to 18 districts in 2012. However, due to financial constraints this was followed by IRS withdrawal to 6 districts by 2021 - with planned further withdrawal in 2022 – 2023 down to 2 districts. Method: The retrospective analysis is performed to understand the impact of IRS withdrawal based on DHIS2 malaria incidence per 1000 population data. Data is subjected to interrupted time series (ITS) based on monthly periods to investigate whether the effect due to IRS withdrawal is statistically significant or not. The analysis helps to examine the changes in level and/or trend before, during, and after IRS withdrawal. Results:...

Journal of The American Mosquito Control Association, Sep 1, 2006

Research Square (Research Square), Jun 1, 2021

Tropical Medicine & International Health, Nov 1, 2004

BMC Public Health, Jul 5, 2010

Background: Muleba district in Northwestern Tanzania has experienced malaria epidemics in recent ... more Background: Muleba district in Northwestern Tanzania has experienced malaria epidemics in recent years. Community knowledge, attitudes and practices are important in enhancing disease control interventions. This study investigated determinants of malaria epidemics in the study area in relation to household knowledge, attitudes and practice on malaria. Methods: A community based cross-sectional survey involving 504 study participants was conducted between April and June 2007 using a structured questionnaire focusing on knowledge, attitudes and practices of community members in epidemic and non-epidemic villages about malaria transmission, signs and symptoms, treatment, prevention and control. Multivariate logistic regression analysis was used to assess determinants of malaria epidemics. Results: A total of 504 respondents (males = 36.9%) were interviewed. Overall, 453 (90.1%) mentioned malaria as the most important disease in the area. Four hundred and sixty four respondents (92.1%) knew that malaria is transmitted through mosquito bite. A total of 436 (86.7%), 306 (60.8%) and 162 (32.1%) mentioned fever, vomiting and loss of appetite as major symptoms/signs of malaria, respectively. Of those interviewed 328 (65.1%) remembered the recent outbreak of 2006. Of the 504 respondents interviewed, 296 (58.7%) reported that their households owned at least one mosquito net. Three hundred and ninety seven respondents (78.8%) knew insecticides used to impregnate bed nets. About two thirds (63.3%) of the respondents had at least a household member who suffered from malaria during the recent epidemic. During the 2006 outbreak, 278 people (87.2%) sought treatment from health facilities while 27 (8.5%) obtained drugs from drug shops and 10 (3.1%) used local herbs. Logistic regression analysis showed that household location and level of knowledge of cause of malaria were significant predictors of a household being affected by epidemic. Conclusions: Residents of Muleba district have high level of knowledge on malaria. However, this knowledge has not been fully translated into appropriate use of available malaria interventions. Our findings suggest that household location, ineffective usage of insecticide treated nets and knowledge gaps on malaria transmission, signs and symptoms, prevention and control predisposed communities in the district to malaria epidemics. It is important that health education packages are developed to address the identified knowledge gaps.

Acta Tropica, Jun 1, 1991

In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out.... more In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out. The people received them enthusiastically and brought their nets for re-impregnation at six monthly intervals. Bioassays showed that the insecticidal power of permethrin impregnated nets remained adequate for six months unless the nets were washed. Nets with 30 mg lambdacyhalothrin/m2 retained high insecticidal power despite washing, but this dose caused temporary cold-like symptoms in those sleeping under freshly treated dry nets. Methods by which durable bednets might be made affordable by Tanzanian villagers are discussed.

Parasitology International, Jun 1, 2009

The effect of HIV on filarial-specific antibody response before and after treatment with diethylc... more The effect of HIV on filarial-specific antibody response before and after treatment with diethylcarbamazine (DEC) was analysed by comparing two groups of Wuchereria bancrofti-infected adult individuals (positive for circulating filarial antigen) who were positive (n=15) or negative (n=21) for HIV co-infection. Prior to DEC treatment there was no significant difference in filarial-specific IgG1, IgG2, IgG4 and IgE antibody response between the HIV negative and the HIV positive group, while a five times (statistically significant) higher filarial-specific IgG3 response was observed in the HIV positive than in the HIV negative group. At 12 weeks after treatment with DEC, a significant decrease in filarial-specific IgG4 was observed in the HIV positive but not in the HIV negative group, indicating that DEC treatment had a stronger antifilarial effect in individuals co-infected with HIV. DEC treatment had no significant effect on the other classes of filarial specific antibodies, neither in the HIV negative or the HIV positive group.

Acta Tropica, Jun 1, 1991

In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out.... more In five Tanzanian villages, nets impregnated with permethrin or lambdacyhalothrin were given out. The people received them enthusiastically and brought their nets for re-impregnation at six monthly intervals. Bioassays showed that the insecticidal power of permethrin impregnated nets remained adequate for six months unless the nets were washed. Nets with 30 mg lambdacyhalothrin/m2 retained high insecticidal power despite washing, but this dose caused temporary cold-like symptoms in those sleeping under freshly treated dry nets. Methods by which durable bednets might be made affordable by Tanzanian villagers are discussed.

Transactions of The Royal Society of Tropical Medicine and Hygiene, Aug 1, 2004

Examination of 1829 children from 6 primary schools in coastal Tanzania revealed overall Wucherer... more Examination of 1829 children from 6 primary schools in coastal Tanzania revealed overall Wuchereria bancrofti microfilaria (mf) and circulating filarial antigen (CFA) prevalences of 17.3% and 43.7%, respectively. A randomized double-blind field trial with a single dose of ivermectin (150-200 g/kg body weight) alone or in combination with albendazole (400 mg) was subsequently carried out among these children. Both treatment regimens resulted in a considerable decrease in mean mf intensities, with overall reductions being slightly but statistically significantly higher for the combination than for ivermectin alone. The difference in effect between the two treatment regimens was most pronounced at 6 months, whereas it was minor at 12 months after treatment. The relative effect of treatment on mean CFA units was less pronounced than on mf. For both treatment regimens, reductions in CFA intensity appeared to be higher in children who were both CFA and mf positive before treatment, which may suggest that treatment mainly affected the survival and/or production of mf, rather than the survival of adult worms. New cases of infection appeared after treatment with both regimens among the pre-treatment mf and CFA negative children. Adverse reactions were few and mild in both groups, and mainly reported from pre-treatment mf and CFA positive children. The alarmingly high prevalence of W. bancrofti infection in primary school children highlights the importance of also determining the reversibility of already acquired early lesions, and the development of new measures and strategies to specifically protect children from later developing clinical disease.

Malaria Journal, Sep 28, 2021

Background: Long-lasting efficacy of insecticide-treated nets is a balance between adhesion, rete... more Background: Long-lasting efficacy of insecticide-treated nets is a balance between adhesion, retention and migration of insecticide to the surface of netting fibres. ICON ® Maxx is a twin-sachet 'home-treatment kit' of pyrethroid plus binding agent, recommended by the World Health Organization (WHO) for long-lasting, wash-fast treatment of polyester nets. While knitted polyester netting is widely used, fine woven polyethylene netting is increasingly available and nets made of cotton and nylon are common in Africa and Asia. It is important to investigate whether ICON Maxx is able to fulfill the WHO criteria of long-lasting treatment on a range of domestic fabrics to widen the scope for malaria protection. Methods: This study was a controlled comparison of the bio-efficacy and wash-fastness of lambda-cyhalothrin CS, with or without binder, on nets made of cotton, polyethylene, nylon, dyed and undyed polyester. Evaluation compared an array of bioassays: WHO cone and cylinder, median time to knockdown and WHO tunnel tests using Anopheles mosquitoes. Chemical assay revealed further insight. Results: ICON Maxx treated polyethylene and polyester netting met the WHO cone and tunnel test bio-efficacy criteria for LLIN after 20 standardized washes. Although nylon and cotton netting failed to meet the WHO cone and cylinder criteria, both materials passed the WHO tunnel test criterion of 80% mortality after 20 washes. All materials treated with standard lambda-cyhalothrin CS without binder failed to meet any of the WHO bio-efficacy criteria within 5 washes. Conclusion: The bio-efficacy of ICON Maxx against mosquitoes on netting washed up to 20 times demonstrated wash durability on a range of synthetic polymer and natural fibres: polyester, polyethylene, nylon and cotton. This raises the prospect of making insecticide-binder kits into an effective approach for turning untreated nets, curtains, military clothing, blankets-and tents and tarpaulins as used in disasters and humanitarian emergencies-into effective malaria prevention products. It may provide a solution to the problem of reduced LLIN coverage between campaigns by converting commercially sourced untreated nets into LLINs through community or home treatment. It may also open the door to binding of non-pyrethroid insecticides to nets and textiles for control of pyrethroid resistant vectors.

Tanzania health research bulletin, Oct 21, 2011

PLOS ONE, Feb 16, 2010

Background: The importance of invasive salmonellosis in African children is well recognized but t... more Background: The importance of invasive salmonellosis in African children is well recognized but there is inadequate information on these infections. We conducted a fever surveillance study in a Tanzanian rural hospital to estimate the case fraction of invasive salmonellosis among pediatric admissions, examine associations with common co-morbidities and describe its clinical features. We compared our main findings with those from previous studies among children in sub-Saharan Africa.

Tanzania health research bulletin, Mar 26, 2012

Acta Tropica, Oct 1, 2000

The circadian periodicity of Plasmodium falciparum gametocytes in peripheral blood was analysed i... more The circadian periodicity of Plasmodium falciparum gametocytes in peripheral blood was analysed in a group of children from an holoendemic community of northeastern Tanzania. No periodicity was observed with asexual stage parasites. Gametocytes were shown to display a diurnal subperiodic pattern with a periodicity index of 31.8. Mathematical analysis of the data indicated that P. falciparum gametocytes tend to display periodicity with a peak (15:30-19:30 h) that do not coincide with the peak (00:30-03:30 h) biting activity of the local vector, Anopheles gambiae. We were thus able to show a P. falciparum gametocyte periodicity with a harmonic wave pattern, but its functional biological significance if any, is currently unknown.

Background The need to develop new products and novel approaches for malaria vector control is re... more Background The need to develop new products and novel approaches for malaria vector control is recognized as a global health priority. One approach to meeting this need has been the development of new products for indoor residual spraying (IRS) with novel active ingredients for public health. While initial results showing the impact of several of these next-generation IRS products have been encouraging, questions remain about how to best deploy them for maximum impact. To help address these questions, a 2-year cluster-randomized controlled trial to measure the impact of IRS with a microencapsulated formulation of pirimiphos-methyl (PM) in an area with high ownership of long-lasting insecticidal nets (LLINs) was conducted in a high-transmission district of central Mozambique with pyrethroid resistant vectors. Presented here are the results of the vector surveillance component of the trial. Methods The 2 year, two-armed trial was conducted in Mopeia District, Zambezia Province, Mozamb...

Additional file 1. Maximum and minimum temperature (°C) and relative humidity (%RH) during the 60... more Additional file 1. Maximum and minimum temperature (°C) and relative humidity (%RH) during the 60 minutes testing and up to 7 day holding period & % Mortality of mosquitoes tested with the negative control (WHO papers treated with 2ml of distilled water) for up to 7 days after bioassay.

Malaria morbidity and mortality rates in Sub-Saharan Africa are increasing. The scale-up of long-... more Malaria morbidity and mortality rates in Sub-Saharan Africa are increasing. The scale-up of long-lasting insecticidal nets and indoor residual spraying have been the major contributors to the decrease of malaria burden. These tools are now threatened by insecticide resistance in malaria vectors, which is spreading dramatically. After two different real-time polymerase chain reaction molecular characterizations carried out on 70 mosquitoes sampled in the locality of Elibou in southern Côte d’Ivoire, results revealed that 9 mosquitoes from Anopheles harbored the double Eastand West-African knockdown resistance coluzzi mutations. In the previous year, only 1 mosquito out of 150 sampled from 10 regions of the country had the same genotype. These results show the rapid spread of insecticide resistance in malaria vectors and highlight the urgent need to diversify the methods of vector control in order to avoid the failure of insecticide-based vector control tools which may favor malaria f...

Although pyrethroid insecticides are a promising means of controlling Anopheles malaria vectors, ... more Although pyrethroid insecticides are a promising means of controlling Anopheles malaria vectors, there is a need to monitor for resistance. It has been proposed that the results of the WHO-recommended testing method, involving exposure to impregnated paper for 1 hour, might be misleading because of knockdown during this period, and that exposure to a higher dose of pyrethroid for 2 minutes might be preferable. However, comparative tests with a susceptible and a permethrin-resistant strain of A. stephensi showed that exposure for 1 hour was at least as sensitive in detecting resistance as was the short exposure method.

Background: Indoor Residual Spray (IRS) has proven to be one of the most effective malaria vector... more Background: Indoor Residual Spray (IRS) has proven to be one of the most effective malaria vector control interventions in reducing malaria transmission mainly in areas with high transmission. With the support from the US President’s Malaria Initiative (PMI), Tanzania has gone through expansion of IRS implementation with different insecticides from one district in 2007 to 18 districts in 2012. However, due to financial constraints this was followed by IRS withdrawal to 6 districts by 2021 - with planned further withdrawal in 2022 – 2023 down to 2 districts. Method: The retrospective analysis is performed to understand the impact of IRS withdrawal based on DHIS2 malaria incidence per 1000 population data. Data is subjected to interrupted time series (ITS) based on monthly periods to investigate whether the effect due to IRS withdrawal is statistically significant or not. The analysis helps to examine the changes in level and/or trend before, during, and after IRS withdrawal. Results:...