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Mapua SA, Samb B, Nambunga IH, Mkandawile G, Bwanaly H, Kaindoa EW, Odero JO, Masalu JP, Kahamba NF, Hape EE, Govella NJ, Okumu FO, Tripet F. Entomological survey of sibling species in the Anopheles funestus group in Tanzania confirms the role of Anopheles parensis as a secondary malaria vector. Parasit Vectors 2024; 17:261. [PMID: 38886827 PMCID: PMC11181546 DOI: 10.1186/s13071-024-06348-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 06/10/2024] [Indexed: 06/20/2024] Open
Abstract
BACKGROUND Malaria transmission in Tanzania is driven by mosquitoes of the Anopheles gambiae complex and Anopheles funestus group. The latter includes An. funestus s.s., an anthropophilic vector, which is now strongly resistant to public health insecticides, and several sibling species, which remain largely understudied despite their potential as secondary vectors. This paper provides the initial results of a cross-country study of the species composition, distribution and malaria transmission potential of members of the Anopheles funestus group in Tanzania. METHODS Mosquitoes were collected inside homes in 12 regions across Tanzania between 2018 and 2022 using Centres for Disease Control and Prevention (CDC) light traps and Prokopack aspirators. Polymerase chain reaction (PCR) assays targeting the noncoding internal transcribed spacer 2 (ITS2) and 18S ribosomal DNA (18S rDNA) were used to identify sibling species in the An. funestus group and presence of Plasmodium infections, respectively. Where DNA fragments failed to amplify during PCR, we sequenced the ITS2 region to identify any polymorphisms. RESULTS The following sibling species of the An. funestus group were found across Tanzania: An. funestus s.s. (50.3%), An. parensis (11.4%), An. rivulorum (1.1%), An. leesoni (0.3%). Sequencing of the ITS2 region in the nonamplified samples showed that polymorphisms at the priming sites of standard species-specific primers obstructed PCR amplification, although the ITS2 sequences closely matched those of An. funestus s.s., barring these polymorphisms. Of the 914 samples tested for Plasmodium infections, 11 An. funestus s.s. (1.2%), and 2 An. parensis (0.2%) individuals were confirmed positive for P. falciparum. The highest malaria transmission intensities [entomological inoculation rate (EIR)] contributed by the Funestus group were in the north-western region [108.3 infectious bites/person/year (ib/p/y)] and the south-eastern region (72.2 ib/p/y). CONCLUSIONS Whereas An. funestus s.s. is the dominant malaria vector in the Funestus group in Tanzania, this survey confirms the occurrence of Plasmodium-infected An. parensis, an observation previously made in at least two other occasions in the country. The findings indicate the need to better understand the ecology and vectorial capacity of this and other secondary malaria vectors in the region to improve malaria control.
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Affiliation(s)
- Salum Abdallah Mapua
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania.
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Huxley Building, Keele, Staffordshire, ST5 5BG, UK.
| | - Badara Samb
- Laboratoire d'Écologie Vectorielle et Parasitaire, Département de Biologie Animale, Faculté des Sciences et Techniques, Université Cheikh Anta Diop de Dakar, 5005, Dakar-Fann, BP, Senegal
| | - Ismail Hassan Nambunga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Gustav Mkandawile
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Hamis Bwanaly
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Emmanuel Wilson Kaindoa
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Joel Ouma Odero
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
| | - John Paliga Masalu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
| | - Najat Feruz Kahamba
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
| | - Emmanuel Elirehema Hape
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Nicodem James Govella
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
| | - Fredros Oketch Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Morogoro, Tanzania
- School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK
- School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania
| | - Frederic Tripet
- Swiss Tropical and Public Health Institute, Kreuzgasse 2, 4123, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
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The Impact of Insecticide Pre-Exposure on Longevity, Feeding Succession, and Egg Batch Size of Wild Anopheles gambiae s.l. J Trop Med 2020; 2020:8017187. [PMID: 33061994 PMCID: PMC7539113 DOI: 10.1155/2020/8017187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 09/11/2020] [Accepted: 09/19/2020] [Indexed: 11/18/2022] Open
Abstract
Background Insecticide resistance among the vector population is the main threat to existing control tools available. The current vector control management options rely on applications of recommended public health insecticides, mainly pyrethroids through long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Regular monitoring of insecticide resistance does not provide information on important factors that affect parasite transmission. Such factors include vector longevity, vector competence, feeding success, and fecundity. This study investigated the impacts of insecticide resistance on longevity, feeding behaviour, and egg batch size of Anopheles gambiae s.l. Method The larval sampling was conducted in rice fields using a standard dipper (350 ml) and reared to adults in field insectary. A WHO susceptibility test was conducted using standard treated permethrin (0.75%) and deltamethrin (0.05%) papers. The susceptible Kisumu strain was used for reference. Feeding succession and egg batch size were monitored for all survivors and control. Results The results revealed that mortality rates declined by 52.5 and 59.5% for permethrin and deltamethrin, respectively. The mortality rate for the Kisumu susceptible strain was 100%. The survival rates of wild An. gambiae s.l. was between 24 and 27 days. However, the Kisumu susceptible strain blood meal feeding was significantly higher than resistant colony (t = 2.789, df = 21, P=0.011). Additionally, the susceptible An. gambiae s.s. laid more eggs than the resistant An.gambiae s.l. colony (Χ2 = 1366, df = 1, P ≤ 0.05). Conclusion It can, therefore, be concluded that the wild An. gambiae s.l. had increased longevity, blood feeding, and small egg batch size compared to Kisumu susceptible colonies.
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Kweka EJ, Mazigo HD, Lyaruu LJ, Mausa EA, Venter N, Mahande AM, Coetzee M. Anopheline Mosquito Species Composition, Kdr Mutation Frequency, and Parasite Infectivity Status in Northern Tanzania. JOURNAL OF MEDICAL ENTOMOLOGY 2020; 57:933-938. [PMID: 31923308 DOI: 10.1093/jme/tjz245] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Indexed: 06/10/2023]
Abstract
The scaling-up of malaria control interventions in northern Tanzania has resulted in a decline in malaria prevalence and vector species composition. Despite this achievement, residual malaria transmission remains a concern in the area. The main aim of this study was to investigate malaria vector species composition, parasite infectivity rates, and the presence of insecticide knockdown resistance (kdr) mutations in three sites that have experienced a significant decline in malaria in northern Tanzania. Adult mosquitoes were sampled using light traps in houses and hand-aspirators in cowsheds, whereas the standard dipping method was used for sampling mosquito larvae. Adult mosquitoes identified as Anopheles gambiae s.l. and An. funestus s.l. and larval stages III and IV of An. gambiae s.l. were stored in absolute ethanol for further laboratory molecular identification. The identified species in the An. gambiae complex were An. gambiae s.s., An. merus, An. quadriannulatus, and An. arabiensis, whereas the An. funestus group comprised An. funestus s.s., An. rivulorum, and An. leesoni. For An. gambiae s.s. analyzed from Zeneth, 47.6% were kdr-East homozygous susceptible, 35.7% kdr-East heterozygous resistant, 9.6% kdr-East homozygous resistant, and 7.1% undefined, whereas specimens from Kwakibuyu were 45.5% kdr-East homozygous susceptible, 32.7% kdr-East heterozygous resistant, 16.3% kdr-East homozygous resistant, and 5.5% undefined. There were no kdr-West alleles identified from any specimen. The overall malaria parasite infectivity rate was 0.75%. No infections were found in Moshi. The findings indicate that populations of the major malaria vector mosquitoes are still present in the study area, with An. funestus taking a lead in malaria transmission.
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Affiliation(s)
- Eliningaya J Kweka
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute, Arusha, Tanzania
- Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences, Mwanza, Tanzania
| | - Humphrey D Mazigo
- Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences, Mwanza, Tanzania
| | - Lucile J Lyaruu
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute, Arusha, Tanzania
| | - Emmanuel A Mausa
- National Plant Genetic Resource Centre, Tropical Pesticides Research Institute, Arusha, Tanzania
| | - Nelius Venter
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multi-disciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging, Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Aneth M Mahande
- Mabogini Field Station, Tropical Pesticides Research Institute, Moshi, Tanzania
| | - Maureen Coetzee
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multi-disciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging, Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
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Burke A, Dahan-Moss Y, Duncan F, Qwabe B, Coetzee M, Koekemoer L, Brooke B. Anopheles parensis contributes to residual malaria transmission in South Africa. Malar J 2019; 18:257. [PMID: 31358015 PMCID: PMC6664530 DOI: 10.1186/s12936-019-2889-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 07/22/2019] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Understanding the contribution of outdoor-resting Anopheles mosquitoes to residual malaria transmission is important in terms of scaling up vector control towards malaria elimination in South Africa. The aim of this project was to assess the potential role of Anopheles parensis and other Anopheles species in residual malaria transmission, using sentinel surveillance sites in the uMkhanyakude District of northern KwaZulu-Natal Province. METHODS Monthly vector surveillance was conducted at the sentinel sites from January 2017 to May 2018. Outdoor-placed clay pot resting traps were used to collect male and female adult Anopheles mosquitoes. All Anopheles gambiae complex and Anopheles funestus group specimens collected were identified to species and all females were screened for Plasmodium falciparum circumsporozoite protein (CSP) by enzyme-linked immunosorbent assay (ELISA). Samples showing infectivity for P. falciparum were further verified by a nested PCR and subsequent DNA sequence analysis. RESULTS From a sample of 491 anophelines, Anopheles arabiensis (n = 228) and An. parensis (n = 194) were the most abundant. Other species collected included Anopheles merus (n =11), Anopheles quadriannulatus (n = 10), Anopheles leesoni (n = 29), Anopheles rivulorum (n =18), and Anopheles vaneedeni (n =1). Of the 317 female specimens screened for P. falciparum CSP, one Anopheles arabiensis and one An. parensis showed positive by ELISA and Plasmodium nested PCR. For the An. parensis specimen, confirmation of its species identity was based on sequence analysis of the ITS2 region, and the presence of P. falciparum DNA was further confirmed by sequence analysis. CONCLUSIONS Anopheles parensis is a potential vector of malaria in South Africa although its contribution to transmission is likely to be minimal at best owing to its strong zoophilic tendency. By contrast, An. arabiensis is a major vector that is primarily responsible for the bulk of residual malaria transmission in South Africa. As all recently collected sporozoite-positive Anopheles mosquitoes were found in outdoor-placed resting traps, it is necessary to introduce interventions that can be used to control outdoor-resting vector populations while maintaining the efficacy of South Africa's indoor house spraying operations.
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Affiliation(s)
- Ashley Burke
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research On Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Yael Dahan-Moss
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research On Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Frances Duncan
- School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Bheki Qwabe
- Environmental Health, Malaria and Communicable Disease Control, KwaZulu-Natal Department of Health, Jozini, South Africa
| | - Maureen Coetzee
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research On Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Lizette Koekemoer
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research On Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Basil Brooke
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multidisciplinary Research On Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa.
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Verma P, Sarkar S, Singh P, Dhiman RC. Devising a method towards development of early warning tool for detection of malaria outbreak. Indian J Med Res 2018; 146:612-621. [PMID: 29512603 PMCID: PMC5861472 DOI: 10.4103/ijmr.ijmr_426_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Background & objectives Uncertainty often arises in differentiating seasonal variation from outbreaks of malaria. The present study was aimed to generalize the theoretical structure of sine curve for detecting an outbreak so that a tool for early warning of malaria may be developed. Methods A 'case/mean-ratio scale' system was devised for labelling the outbreak in respect of two diverse districts of Assam and Rajasthan. A curve-based method of analysis was developed for determining outbreak and using the properties of sine curve. It could be used as an early warning tool for Plasmodium falciparum malaria outbreaks. Result In the present method of analysis, the critical Cmax(peak value of sine curve) value of seasonally adjusted curve for P. falciparum malaria outbreak was 2.3 for Karbi Anglong and 2.2 for Jaisalmer districts. On case/mean-ratio scale, the Cmax value of malaria curve between Cmaxand 3.5, the outbreak could be labelled as minor while >3.5 may be labelled as major. In epidemic years, with mean of case/mean ratio of ≥1.00 and root mean square (RMS) ≥1.504 of case/mean ratio, outbreaks can be predicted 1-2 months in advance. Interpretation & conclusions The present study showed that in P. falciparum cases in Karbi Anglong (Assam) and Jaisalmer (Rajasthan) districts, the rise in Cmaxvalue of curve was always followed by rise in average/RMS or both and hence could be used as an early warning tool. The present method provides better detection of outbreaks than the conventional method of mean plus two standard deviation (mean+2 SD). The identified tools are simple and may be adopted for preparedness of malaria outbreaks.
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Affiliation(s)
- Preeti Verma
- Environmental Epidemiology Division, ICMR-National Institute of Malaria Research, New Delhi, India
| | - Soma Sarkar
- Environmental Epidemiology Division, ICMR-National Institute of Malaria Research, New Delhi, India
| | - Poonam Singh
- Environmental Epidemiology Division, ICMR-National Institute of Malaria Research, New Delhi, India
| | - Ramesh C Dhiman
- Environmental Epidemiology Division, ICMR-National Institute of Malaria Research, New Delhi, India
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Kweka EJ, Mausa EA, Venter N, Derua YA, Kimaro EE, Coetzee M. Application of hydrolysis probe analysis to identify clade types of the malaria vector mosquito Anopheles funestus sensu stricto from Muheza, northeastern Tanzania. MEDICAL AND VETERINARY ENTOMOLOGY 2018; 32:125-128. [PMID: 29068089 DOI: 10.1111/mve.12274] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 06/19/2017] [Accepted: 09/18/2017] [Indexed: 06/07/2023]
Abstract
A hydrolysis probe analysis (TaqMan assay) was used to study clade types in Anopheles funestus sensu stricto Giles, a major malaria vector in sub-Saharan Africa, with specimens collected from Muheza in Tanga, northeastern Tanzania. A total of 186 An. funestus specimens were analysed, revealing that 176 (94.6%) were of clade I and 10 (5.4%) of clade II. These findings extend the distribution of clade type II from southern Mozambique and northern Zambia to northeastern Tanzania. The technique used can also be of great value in assessing the role and contribution of these clade types in malaria transmission and insecticide resistance frequencies for An. funestus s.s.
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Affiliation(s)
- E J Kweka
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute, Arusha, Tanzania
- Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences, Mwanza, Tanzania
| | - E A Mausa
- National Plant Genetic Resource Centre, Tropical Pesticides Research Institute, Arusha, Tanzania
| | - N Venter
- Faculty of Health Sciences, Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Y A Derua
- National Institute for Medical Research, Amani Research Centre, Tanga, Tanzania
| | - E E Kimaro
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute, Arusha, Tanzania
| | - M Coetzee
- Faculty of Health Sciences, Wits Research Institute for Malaria, School of Pathology, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
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Emidi B, Kisinza WN, Mosha FW. Impact of non-pyrethroid insecticide treated durable wall lining on age structure of malaria vectors in Muheza, Tanzania. BMC Res Notes 2017; 10:744. [PMID: 29258570 PMCID: PMC5735946 DOI: 10.1186/s13104-017-3078-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 12/08/2017] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVE Malaria vectors control interventions are designed to cause immediate killing or shorten mosquito lives, therefore does not allow enough time for the development of the parasites to infective stage. The wall lining is new malaria vectors control intervention in Tanzania where its impact on age structure is not well known. Therefore this study aimed at determining the impact of non-pyrethroid durable wall lining on the age structure of malaria vectors. RESULTS Higher proportions of An. gambiae sensu lato (57.1%, z = 2.66, P = 0.0077) and An. funestus (64.8%, z = 3.38, P = 0.001) were collected in the control clusters. Unexpectedly, significantly higher proportion of parous An. gambiae s. l. were collected in the intervention clusters (z = - 2.78, P = 0.0054). The wall lining intervention has demonstrated low impact on age structure of An. gambiae s. l., this call for further studies on the efficacy of the intervention.
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Affiliation(s)
- Basiliana Emidi
- Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania
- National Institute for Medical Research, Headquarters, P.O. Box 9653, Dar Es Salaam, Tanzania
| | - William N. Kisinza
- National Institute for Medical Research, Amani Research Centre, P.O. Box 81, Muheza, Tanzania
| | - Franklin W. Mosha
- Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania
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Nnko EJ, Kihamia C, Tenu F, Premji Z, Kweka EJ. Insecticide use pattern and phenotypic susceptibility of Anopheles gambiae sensu lato to commonly used insecticides in Lower Moshi, northern Tanzania. BMC Res Notes 2017; 10:443. [PMID: 28877733 PMCID: PMC5585946 DOI: 10.1186/s13104-017-2793-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Accepted: 08/31/2017] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Evidence of insecticide resistance has been documented in different malaria endemic areas. Surveillance studies to allow prompt investigation of associated factors to enable effective insecticide resistance management are needed. The objective of this study was to assess insecticide use pattern and phenotypic susceptibility level of Anopheles gambiae sensu lato to insecticides commonly used in malaria control in Moshi, northern Tanzania. METHODS A cross-sectional survey was conducted to assess insecticide usage pattern. Data was collected was through closed and open ended questionnaires The WHO diagnostic standard kit with doses of 0.1% bendiocarb, 0.05% deltamethrin, 0.75% permethrin and 4% DDT were used to detect knockdown time, mortality and resistance ratio of wild A. gambiae sensu lato. The questionnaire survey data was analyzed using descriptive statistics and one-way analysis of variance while susceptibility data was analysed by logistic regression with probit analysis using SPSS program. The WHO criteria was used to evaluate the resistance status of the tested mosquito populations. RESULTS A large proportion of respondents (80.8%) reported to have used insecticide mainly for farming purposes (77.3%). Moreover, 93.3% of household reported usage of long lasting insecticidal nets. The frequently used class of insecticide was organophosphate with chloropyrifos as the main active ingredients and dursban was the brand constantly reported. Very few respondents (24.1%) applied integrated vector control approaches of and this significantly associated with level of knowledge of insecticide use (P < 0.001). Overall knockdown time for A. gambiae s.l was highest in DDT, followed by Pyrethroids (Permethrin and deltamethrin) and lowest in bendiocarb. Anopheles gambiae s.l showed susceptibility to bendiocarb, increased tolerance to permethrin and resistant to deltamethrin. The most effective insecticide against the population from tested was bendiocarb, with a resistance ratio ranging between 0.93-2.81. CONCLUSION Education on integrated vector management should be instituted and a policy change on insecticide of choice for malaria vector control from pyrethroids to carbamates (bendiocarb) is recommended. Furthermore, studies to detect cross resistance between pyrethroids and organophosphates should be carried out.
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Affiliation(s)
- Elinas J. Nnko
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, P.O. Box 65011, Dar es Salaam, Tanzania
| | - Charles Kihamia
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, P.O. Box 65011, Dar es Salaam, Tanzania
| | - Filemoni Tenu
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, P.O. Box 81, Tanga, Tanzania
| | - Zul Premji
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, P.O. Box 65011, Dar es Salaam, Tanzania
| | - Eliningaya J. Kweka
- Tropical Pesticides Research Institute, Division of Livestock and Human Health Disease Vector Control, Mosquito Section, P.O. Box 3024, Arusha, Tanzania
- Department of Medical Parasitology and Entomology, School of Medicine, Catholic University of Health and Allied Sciences, P.O. Box 1464 Mwanza, Tanzania
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Emidi B, Kisinza WN, Mmbando BP, Malima R, Mosha FW. Effect of physicochemical parameters on Anopheles and Culex mosquito larvae abundance in different breeding sites in a rural setting of Muheza, Tanzania. Parasit Vectors 2017. [PMID: 28645303 PMCID: PMC5482952 DOI: 10.1186/s13071-017-2238-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Basiliana Emidi
- Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania. .,National Institute for Medical Research, Headquarters, P.O. Box 9653, Dar es Salaam, Tanzania.
| | - William N Kisinza
- National Institute for Medical Research, Amani Centre, P.O. Box 81, Muheza, Tanzania
| | - Bruno P Mmbando
- National Institute for Medical Research, Tanga Centre, P.O. Box 5004, Tanga, Tanzania
| | - Robert Malima
- National Institute for Medical Research, Amani Centre, P.O. Box 81, Muheza, Tanzania
| | - Franklin W Mosha
- Kilimanjaro Christian Medical University College, P.O. Box 2240, Moshi, Tanzania
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Kweka EJ, Lee MC, Mwang'onde BJ, Tenu F, Munga S, Kimaro EE, Himeidan YE. Bio-efficacy of deltamethrin based durable wall lining against wild populations of Anopheles gambiae s.l. in Northern Tanzania. BMC Res Notes 2017; 10:92. [PMID: 28187779 PMCID: PMC5303249 DOI: 10.1186/s13104-017-2414-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 02/02/2017] [Indexed: 11/18/2022] Open
Abstract
Background Indoor residual spraying (IRS) is one of the preferred tools used for control of malaria in many settings in the world. However, this control tool still faces challenges that include lack of long lasting active ingredient, limited number of well-trained personal, and need of repeated treatment which increases operational costs and reduces acceptability by residents. As a result there is need to develop and validate other methods which can complement the existing controls. The current study compared the bio-efficacy of durable wall lining (DL) (treated with deltamethrin 265 mg/m2) and IRS (with deltamethrin 5% WP at 20 mg/m2) on indoor mosquitoes densities and biting behaviour of mosquitoes in comparison with control houses without either DL or IRS. Methods A study with two treatment arms and a control was conducted in Magugu ward, Northern Tanzania. Overall, a total of 60 houses were selected for the study with 20 houses per treatment arm and control. From each arm and control five houses were selected for mosquitoes trapping. Mosquitoes were sampled from 18:00 to 07:00 hourly every month for a period of 6 months. Mosquitoes were sampled using CDC miniature light traps. Results A total of 14,400 female wild mosquitoes were used for contact bioassays in the control arm. 20 houses were sprayed, additionally walls of 20 houses were installed with wall liners, and walls of 20 unsprayed houses were used as control. Also, a total of 946 mosquitoes were sampled with traps in 60 houses during the hourly sampling for 6 months. A total of 3000 unfed females of An. gambiae s.l. wild population raised from larvae were collected from natural habitats in the same village for bioassays. The decline in indoor mosquitoes densities observed in this study did not lead to a shift in the biting cycles (P = 0.712). The number of mosquitoes caught indoors in houses with DL and IRS was significantly lower (P < 0.001) compared to control houses. When the comparisons were done between DL and IRS houses, the densities were significantly lower in DL houses compared to IRS houses (P = 0.021). In the DL installed houses, indoor mosquito density declined notably and sustained throughout the 6 months of the study. However, in those houses sprayed with deltamethrin 5% WP (PALI™5 WP), the density noted to start to increase within four months after spraying(do you mean to say that the densities declined up to 4 months post spraying and thereafter increased. Conclusions Considering the efficacy duration of DL against IRS with deltamethrin 5% WP on mosquito densities decline indoors. The results of this study suggest that DL is more effective in malaria control as its efficacy lasted more than that of IRS.
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Affiliation(s)
- Eliningaya J Kweka
- Division of Livestock and Human Diseases Mosquitoes Control, Mosquito Section, Tropical Pesticides Research Institute, P.O. Box 30214, Arusha, Tanzania. .,Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences, P.O. Box 1464, Mwanza, Tanzania.
| | - Ming-Chieh Lee
- Program in Public Health, College of Health Sciences, University of California Irvine, Irvine, CA, USA
| | - Beda J Mwang'onde
- Division of Livestock and Human Diseases Mosquitoes Control, Mosquito Section, Tropical Pesticides Research Institute, P.O. Box 30214, Arusha, Tanzania
| | - Filemoni Tenu
- Amani Medical Research Centre, National Institute for Medical Research, P.O. Box 81, Muheza, Tanzania
| | - Stephen Munga
- Centre for Global Health Research, Kenya Medical Research Institute, P.O.Box 1578, Kisumu, Kenya
| | - Epiphania E Kimaro
- Division of Livestock and Human Diseases Mosquitoes Control, Mosquito Section, Tropical Pesticides Research Institute, P.O. Box 30214, Arusha, Tanzania
| | - Yousif E Himeidan
- Africa Technical Research Centre, Mosquitoes Health International, P.O. Box 15500, Arusha, Tanzania
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11
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Tungu P, Messenger LA, Kirby MJ, Sudi W, Kisinza W, Rowland M. Phase III evaluation of the insecticidal efficacy and durability of a deltamethrin-treated polypropylene long-lasting net LifeNet®, in comparison with long-lasting nets made from polyester and polyethylene: study protocol. ACTA ACUST UNITED AC 2016; 74:56. [PMID: 28042474 PMCID: PMC5200967 DOI: 10.1186/s13690-016-0168-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 11/30/2016] [Indexed: 11/10/2022]
Abstract
Background Universal coverage of long-lasting insecticidal nets (LNs) made from polyester or polyethylene fibres has been adopted as the standard of care to control malaria among at-risk populations. To obtain a WHO recommendation, LNs must undergo prospective monitoring of insecticidal efficacy against mosquito vectors over 3 years of household use. The retention of bioefficacy and physical durability of a LN is influenced by net usage practices, textile polymer material and insecticide treatment technology. Fabric durability is the critical factor which determines the interval required between LN replacement campaigns. To investigate factors known to affect LN durability and bioefficacy, we describe a three-arm WHO Pesticide Evaluation Scheme (WHOPES) Phase III evaluation of a LN made uniquely from polypropylene (LifeNet®, Bayer CropScience) compared to standard LNs made from polyester and polyethylene, all treated with deltamethrin, over 3 years of use. Methods This is a prospective three-arm household randomized, equivalence trial of LNs in Tanzania, with nets as the unit of observation. Equal numbers of houses will be randomized to receive deltamethrin-treated polypropylene, polyester or polyethylene LNs; all sleeping spaces in a given household will be provided with one type of net. Bioefficacy (insecticidal activity against mosquitoes), insecticide content of net fibres, and fabric integrity (number, location and size of holes) will be measured every 6 months, using WHO cone or tunnel bioassays, chemical analysis and calculation of hole index, respectively. A cohort of LNs will be surveyed annually to assess survivorship (median LN survival time) and cumulative loss of fabric integrity. Field durability outcomes will be compared with laboratory strength tests. Discussion This is the first trial to compare the relative durability of three LNs each made from a different textile polymer, treated with the same insecticide, in the same community side-by-side over 3 years of use. Trial findings will 1) guide global health organizations on procurement policy and the type of textile polymer which maximizes the interval between LN replacement campaigns, and 2) stimulate manufacturers to improve product performance and development of longer lasting polymers. A full WHO recommendation may be granted to LifeNet® upon successful Phase III completion.
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Affiliation(s)
- Patrick Tungu
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Louisa A Messenger
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Matthew J Kirby
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Wema Sudi
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - William Kisinza
- National Institute for Medical Research, Amani Medical Research Centre, Muheza, Tanzania
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
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12
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Mtove G, Mugasa JP, Messenger LA, Malima RC, Mangesho P, Magogo F, Plucinski M, Hashimu R, Matowo J, Shepard D, Batengana B, Cook J, Emidi B, Halasa Y, Kaaya R, Kihombo A, Lindblade KA, Makenga G, Mpangala R, Mwambuli A, Mzava R, Mziray A, Olang G, Oxborough RM, Seif M, Sambu E, Samuels A, Sudi W, Thomas J, Weston S, Alilio M, Binkin N, Gimnig J, Kleinschmidt I, McElroy P, Moulton LH, Norris L, Ruebush T, Venkatesan M, Rowland M, Mosha FW, Kisinza WN. The effectiveness of non-pyrethroid insecticide-treated durable wall lining to control malaria in rural Tanzania: study protocol for a two-armed cluster randomized trial. BMC Public Health 2016; 16:633. [PMID: 27456339 PMCID: PMC4960851 DOI: 10.1186/s12889-016-3287-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Accepted: 07/09/2016] [Indexed: 11/16/2022] Open
Abstract
Background Despite considerable reductions in malaria achieved by scaling-up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), maintaining sustained community protection remains operationally challenging. Increasing insecticide resistance also threatens to jeopardize the future of both strategies. Non-pyrethroid insecticidetreated wall lining (ITWL) may represent an alternate or complementary control method and a potential tool to manage insecticide resistance. To date no study has demonstrated whether ITWL can reduce malaria transmission nor provide additional protection beyond the current best practice of universal coverage (UC) of LLINs and prompt case management. Methods/design A two-arm cluster randomized controlled trial will be conducted in rural Tanzania to assess whether non-pyrethroid ITWL and UC of LLINs provide added protection against malaria infection in children, compared to UC of LLINs alone. Stratified randomization based on malaria prevalence will be used to select 22 village clusters per arm. All 44 clusters will receive LLINs and half will also have ITWL installed on interior house walls. Study children, aged 6 months to 11 years old, will be enrolled from each cluster and followed monthly to estimate cumulative incidence of malaria parasitaemia (primary endpoint), time to first malaria episode and prevalence of anaemia before and after intervention. Entomological inoculation rate will be estimated using indoor CDC light traps and outdoor tent traps followed by detection of Anopheles gambiae species, sporozoite infection, insecticide resistance and blood meal source. ITWL bioefficacy and durability will be monitored using WHO cone bioassays and household surveys, respectively. Social and cultural factors influencing community and household ITWL acceptability will be explored through focus-group discussions and in-depth interviews. Cost-effectiveness, compared between study arms, will be estimated per malaria case averted. Discussion This protocol describes the large-scale evaluation of a novel vector control product, designed to overcome some of the known limitations of existing methods. If ITWL is proven to be effective and durable under field conditions, it may warrant consideration for programmatic implementation, particularly in areas with long transmission seasons and where pyrethroid-resistant vectors predominate. Trial findings will provide crucial information for policy makers in Tanzania and other malaria-endemic countries to guide resource allocations for future control efforts. Trial registration NCT02533336 registered on 13 July 2014.
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Affiliation(s)
- George Mtove
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania.
| | - Joseph P Mugasa
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Louisa A Messenger
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Robert C Malima
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Peter Mangesho
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Franklin Magogo
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Mateusz Plucinski
- US President's Malaria Initiative, Atlanta, GA, USA.,Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Ramadhan Hashimu
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | | | - Donald Shepard
- National Institute for Medical Research, Headquarters, Dar es Salaam, Tanzania
| | - Bernard Batengana
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Jackie Cook
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Basiliana Emidi
- Kilimanjaro Christian Medical College, Moshi, Tanzania.,National Institute for Medical Research, Headquarters, Dar es Salaam, Tanzania
| | - Yara Halasa
- Brandeis University, Heller School, Waltham, Massachusetts, USA
| | - Robert Kaaya
- Kilimanjaro Christian Medical College, Moshi, Tanzania
| | - Aggrey Kihombo
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Kimberly A Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Geofrey Makenga
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Robert Mpangala
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Abraham Mwambuli
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Ruth Mzava
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Abubakary Mziray
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - George Olang
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | | | - Mohammed Seif
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Edward Sambu
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - Aaron Samuels
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Wema Sudi
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
| | - John Thomas
- Phoenix Ordinary LLC, Bridgewater, New Jersey, USA
| | - Sophie Weston
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Martin Alilio
- President's Malaria Initiative, United States Agency for International Development, Washington DC, USA
| | - Nancy Binkin
- Translating Research into Action Project (TRAction) University Research Co., LLC, Bethesda, Maryland, USA
| | - John Gimnig
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Immo Kleinschmidt
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | - Peter McElroy
- US President's Malaria Initiative, Atlanta, GA, USA.,Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Lawrence H Moulton
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Laura Norris
- President's Malaria Initiative, United States Agency for International Development, Washington DC, USA
| | - Trenton Ruebush
- Translating Research into Action Project (TRAction) University Research Co., LLC, Bethesda, Maryland, USA
| | - Meera Venkatesan
- President's Malaria Initiative, United States Agency for International Development, Washington DC, USA
| | - Mark Rowland
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, UK
| | | | - William N Kisinza
- National Institute for Medical Research, Amani Research Centre, Muheza, Tanzania
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13
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Kweka EJ, Kamau L, Munga S, Lee MC, Githeko AK, Yan G. A first report of Anopheles funestus sibling species in western Kenya highlands. Acta Trop 2013; 128:158-61. [PMID: 23792011 DOI: 10.1016/j.actatropica.2013.06.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 05/29/2013] [Accepted: 06/09/2013] [Indexed: 11/18/2022]
Abstract
Understanding disease vector composition is of priority in designing effective disease control programs. In integrated vector control management, understanding of disease vector species among species complexes simplifies priorities for effective control tools selection. This study identified members of the Anopheles funestus complex sampled in western Kenya from 2002 to 2011 from different breeding sites. Larval sampling was carried out using the standard dipper (350ml) in larval habitats in western Kenya highlands from January 2002 to December 2012. The morphologically identified An. funestus larvae were preserved in absolute ethanol for molecular identification using polymerase chain reaction (PCR). Among the 184 identified specimens of An. funestus sampled, only 76 specimens were clearly identified after DNA amplification and PCR. Among these, 25 (32.9%) were An. funestus s.s, 22 (28.9%) An. leesoni, 9 (11.8%) An. rivulorum and 20 (26.3%) were An. vaneedeni. None was identified as An. parensis. This study has demonstrated the existence of the siblings species of An. funestus complex in western Kenya highlands. However, there is need for further studies to evaluate the dynamics of the adults and sporozoite infectivity rates throughout the region based on these findings.
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Affiliation(s)
- Eliningaya J Kweka
- Tropical Pesticides Research Institute, Division of Livestock and Human Health Disease Vector Control, P.O. Box 3024, Arusha, Tanzania; Centre for Global Health Research, Kenya Medical Research Institute, P.O. Box 1578, Kisumu, Kenya.
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14
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Kawada H, Dida GO, Sonye G, Njenga SM, Mwandawiro C, Minakawa N. Reconsideration of Anopheles rivulorum as a vector of Plasmodium falciparum in western Kenya: some evidence from biting time, blood preference, sporozoite positive rate, and pyrethroid resistance. Parasit Vectors 2012; 5:230. [PMID: 23050856 PMCID: PMC3485129 DOI: 10.1186/1756-3305-5-230] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 10/05/2012] [Indexed: 11/17/2022] Open
Abstract
Background Anopheles gambiae, An. arabiensis, and An. funestus are widespread malaria vectors in Africa. Anopheles rivulorum is the next most widespread species in the An. funestus group. The role of An. rivulorum as a malaria vector has not been fully studied, although it has been found to be a minor or opportunistic transmitter of Plasmodium falciparum. Methods Mosquitoes were collected indoors over a 12-hour period using a light source attached to a rotating bottle collector in order to determine peak activity times and to provide DNA for meal source identification. Gravid female mosquitoes were collected indoors via an aspirator to generate F1 progeny for testing insecticidal susceptibility. Blood meal sources were identified using a multiplexed PCR assay for human and bovine cytochrome-B, and by matching sequences generated with primers targeting vertebrate and mammalian cytochrome-B segments to the Genbank database. Results Anopheles rivulorum fed on human blood in the early evening between 18:00 and 20:00, when insecticide-treated bed nets are not in use, and the presence of Plasmodium falciparum sporozoites in 0.70% of the An. rivulorum individuals tested was demonstrated. Susceptibility to permethrin, deltamethrin, and DDT is higher in An. rivulorum (84.8%, 91.4%, and 100%, respectively) than in An. funestus s.s. (36.8%, 36.4%, and 70%, respectively), whereas mortality rates for propoxur and fenitrothion were 100% for both species. Resistance to pyrethroids was very high in An. funestus s.s. and the potential of the development of high resistance was suspected in An. rivulorum. Conclusion Given the tendency for An. rivulorum to be active early in the evening, the presence of P. falciparum in the species, and the potential for the development of pyrethroid resistance, we strongly advocate reconsideration of the latent ability of this species as an epidemiologically important malaria vector.
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Affiliation(s)
- Hitoshi Kawada
- Department of Vector Ecology & Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
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15
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Kitau J, Oxborough RM, Tungu PK, Matowo J, Malima RC, Magesa SM, Bruce J, Mosha FW, Rowland MW. Species shifts in the Anopheles gambiae complex: do LLINs successfully control Anopheles arabiensis? PLoS One 2012; 7:e31481. [PMID: 22438864 PMCID: PMC3306310 DOI: 10.1371/journal.pone.0031481] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 01/10/2012] [Indexed: 11/24/2022] Open
Abstract
INTRODUCTION High coverage of conventional and long-lasting insecticide treated nets (ITNs and LLINs) in parts of E Africa are associated with reductions in local malaria burdens. Shifts in malaria vector species ratio have coincided with the scale-up suggesting that some species are being controlled by ITNs/LLINs better than others. METHODS Between 2005-2006 six experimental hut trials of ITNs and LLINs were conducted in parallel at two field stations in northeastern Tanzania; the first station was in Lower Moshi Rice Irrigation Zone, an area where An. arabiensis predominates, and the second was in coastal Muheza, where An. gambiae and An. funestus predominate. Five pyrethroids and one carbamate insecticide were evaluated on nets in terms of insecticide-induced mortality, blood-feeding inhibition and exiting rates. RESULTS In the experimental hut trials mortality of An. arabiensis was consistently lower than that of An. gambiae and An. funestus. The mortality rates in trials with pyrethroid-treated nets ranged from 25-52% for An. arabiensis, 63-88% for An. gambiae s.s. and 53-78% for An. funestus. All pyrethroid-treated nets provided considerable protection for the occupants, despite being deliberately holed, with blood-feeding inhibition (percentage reduction in biting rates) being consistent between species. Veranda exiting rates did not differ between species. Percentage mortality of mosquitoes tested in cone bioassays on netting was similar for An. gambiae and An. arabiensis. CONCLUSIONS LLINs and ITNs treated with pyrethroids were more effective at killing An. gambiae and An. funestus than An. arabiensis. This could be a major contributing factor to the species shifts observed in East Africa following scale up of LLINs. With continued expansion of LLIN coverage in Africa An. arabiensis is likely to remain responsible for residual malaria transmission, and species shifts might be reported over larger areas. Supplementary control measures to LLINs may be necessary to control this vector species.
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Affiliation(s)
- Jovin Kitau
- Kilimanjaro Christian Medical College, Tumaini University, Moshi, Tanzania.
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