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Nguetsa GC, Elanga-Ndille E, Essangui Same EG, Nganso Keptchouang T, Mandeng SE, Ekoko Eyisap W, Binyang JA, Fogang B, Nouage L, Piameu M, Ayong L, Etang J, Wanji S, Eboumbou Moukoko CE. Utility of plasma anti-gSG6-P1 IgG levels in determining changes in Anopheles gambiae bite rates in a rural area of Cameroon. Sci Rep 2024; 14:14294. [PMID: 38906949 PMCID: PMC11192751 DOI: 10.1038/s41598-024-58337-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 03/27/2024] [Indexed: 06/23/2024] Open
Abstract
The applicability of the specific human IgG antibody response to Anopheles gambiae salivary Gland Protein-6 peptide 1 (gSG6-P1 salivary peptide) as a biomarker able to distinguish the level of exposure to mosquito bites according to seasonal variations has not yet been evaluated in Central African regions. The study aimed to provide the first reliable data on the IgG anti-gSG6-P1 response in rural area in Cameroon according to the dry- and rainy-season. Between May and December 2020, dry blood samples were collected from people living in the Bankeng village in the forest area of the Centre region of Cameroon. Malaria infection was determined by thick-blood smear microscopy and multiplex PCR. The level of IgG anti-gSG6-P1 response, was assessed by enzyme-linked immunosorbent assay. Anopheles density and aggressiveness were assessed using human landing catches. The prevalence of malaria infection remains significantly higher in the rainy season than in the dry season (77.57% vs 61.44%; p = 0.0001). The specific anti-gSG6-P1 IgG response could be detected in individuals exposed to few mosquito bites and showed inter-individual heterogeneity even when living in the same exposure area. In both seasons, the level of anti-gSG6-P1 IgG response was not significantly different between Plasmodium infected and non-infected individuals. Mosquito bites were more aggressive in the rainy season compared to the dry season (human biting rate-HBR of 15.05 b/p/n vs 1.5 b/p/n) where mosquito density was very low. Infected mosquitoes were found only during the rainy season (sporozoite rate = 10.63% and entomological inoculation rate-EIR = 1.42 ib/p/n). The level of IgG anti-gSG6-P1 response was significantly higher in the rainy season and correlated with HBR (p ˂ 0.0001). This study highlights the high heterogeneity of individual's exposure to the Anopheles gambiae s.l vector bites depending on the transmission season in the same area. These findings reinforce the usefulness of the anti-gSG6-P1 IgG response as an accurate immunological biomarker for detecting individual exposure to Anopheles gambiae s.l. bites during the low risk period of malaria transmission in rural areas and for the differentiating the level of exposure to mosquitoes.
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Affiliation(s)
- Glwadys Cheteug Nguetsa
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon.
- Department of Microbiology and Parasitology, Faculty of Sciences, The University of Buea, P.O. Box 63, Buea, Cameroon.
| | - Emmanuel Elanga-Ndille
- Department of Animal Biology, Faculty of Sciences, The University of Dschang, P.O. Box 96, Dschang, Cameroon
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
| | - Estelle Géraldine Essangui Same
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Tatiana Nganso Keptchouang
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Stanilas Elysée Mandeng
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Wolfgang Ekoko Eyisap
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Jérome Achille Binyang
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
| | - Balotin Fogang
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
| | - Lynda Nouage
- Department of Medical Entomology, Centre for Research in Infectious Diseases, P.O. Box 13591, Yaoundé, Cameroon
- Department of Animal Biology and Physiology, Faculty of Sciences, The University of Yaoundé, P.O. Box 337, Yaounde 1, Cameroon
| | - Micheal Piameu
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
- Ecole des Sciences de La Santé, Université Catholique d'Afrique Centrale, P.O. Box 1110, Yaoundé, Cameroon
| | - Lawrence Ayong
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon
| | - Josiane Etang
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon
- Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte Contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
| | - Samuel Wanji
- Department of Microbiology and Parasitology, Faculty of Sciences, The University of Buea, P.O. Box 63, Buea, Cameroon
| | - Carole Else Eboumbou Moukoko
- Malaria Research Unit, Centre Pasteur Cameroon, P.O. Box 1274, Yaoundé, Cameroon.
- Department of Biological Sciences, Faculty of Medicine and Pharmaceutical Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon.
- Laboratory of Parasitology, Mycology and Virology, Postgraduate Training Unit for Health Sciences, Postgraduate School for Pure and Applied Sciences, The University of Douala, P.O. Box 2701, Douala, Cameroon.
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Azizi S, Martin J, Mbewe NJ, Msapalla A, Mwacha S, Joram A, Mawa B, Kaaya RD, Kitau J, Mosha F, Matowo J, Protopopoff N. Evaluation of Durability as a Function of Fabric Strength and Residual Bio-Efficacy for the Olyset Plus and Interceptor G2 LLINs after 3 Years of Field Use in Tanzania. Trop Med Infect Dis 2023; 8:379. [PMID: 37624317 PMCID: PMC10459516 DOI: 10.3390/tropicalmed8080379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/08/2023] [Accepted: 07/10/2023] [Indexed: 08/26/2023] Open
Abstract
Long-lasting insecticidal nets (LLINs) are prone to reduction in insecticide content and physical strength due to repeated washes and usage. The significant loss to these features jeopardizes their protection against bites from malaria vectors. Insecticide washout is attributed to routine use, friction, and washing, while fabric damage is associated with routine use in households. To maintain coverage and cost-effectiveness, nets should maintain optimal bio-efficacy and physical strength for at least 3 years after distribution. In this study, the bio-efficacy and fabric strength of Olyset plus (OP) LLINs and Interceptor G2 (IG2), that were used for 3 years, were assessed in comparison to untreated and new unwashed counterparts. Both IG2 and OP LLINs (unused, laboratory-washed, and 36 months used) were able to induce significant mortality and blood feeding inhibition (BFI) to mosquitoes compared to the untreated nets. Significantly higher mortality was induced by unused IG2 LLIN and OP LLIN compared to their 36-month-old counterparts against both pyrethroid resistant and susceptible Anopheles gambiae sensu strito. The physical strength of the IG2 LLIN was higher than that of the Olyset Plus LLIN with a decreasing trend from unwashed, laboratory-washed to community usage (36 months old). Malaria control programs should consider bio-efficacy and physical integrity prior to an LLINs' procurement and replacement plan.
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Affiliation(s)
- Salum Azizi
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Jackline Martin
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Njelembo J. Mbewe
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Agness Msapalla
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Silvia Mwacha
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Amandus Joram
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Benson Mawa
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Robert Diotrephes Kaaya
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Jovin Kitau
- Country Office, World Health Organization, Dar es Salaam 255, Tanzania;
| | - Franklin Mosha
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Johnson Matowo
- Department of Medical Parasitology and Entomology, Kilimanjaro Christian Medical University College, Moshi 255, Tanzania (S.M.); (R.D.K.); (F.M.); (J.M.)
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
| | - Natacha Protopopoff
- Pan African Malaria Vector Research Consortium, Moshi 255, Tanzania (N.P.)
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
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Bio-efficacy, physical integrity, use and attrition of long-lasting insecticidal nets under operational conditions for malaria prevention in Ghana. PLoS One 2022; 17:e0275825. [PMID: 36240161 PMCID: PMC9565380 DOI: 10.1371/journal.pone.0275825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 09/23/2022] [Indexed: 11/05/2022] Open
Abstract
Background Malaria remains a public health challenge in endemic countries of the world. The use of Long-lasting Insecticidal Nets (LLINs) is one of the major ways of malaria vector control. Recent evidence however suggests some LLINs are unable to maintain their effectiveness over their useful life span. This study assessed the bio-efficacy, physical integrity, use and attrition at 6 and 12-months post-distribution of LLINs (LifeNet). Methods Following a mass distribution of LLINs in the West Mamprusi District of the North-East region of Ghana in 2018, a total of 147 LLINs were sampled for physical integrity and attrition assessment using hole size and the number of holes as a measure of the proportionate hole index (pHI). Bioassays were conducted on sixty randomly selected LLINs using the WHO guidelines for bio-efficacy testing (cone tests), (20 each at baseline, midline and endline) over a one-year study period. Bed net ownership and use as well as malaria vector resistance status were also assessed. Results Findings indicate high bio-efficacy of approximately 100% average mortalities of mosquitoes at baseline, 6-months and 12-months post-distribution. A small proportion of LLINs (0.8% and 5.6% at the 6 and 12-months surveys respectively) were damaged beyond maintenance while 62.4% and 62.7% of LLINs were used the night before the survey for 6 and 12-months post-distribution respectively. Households with electricity were less likely to use LLINs compared to those without electricity (P-value = 0.016, OR = 0.39). There were 20 fewer LLINs recovered at the 12-months relative to the 6-months resulting in 14.3% attrition rate. Susceptibility testing showed high pyrethroid and organochlorine resistance (18%, 67.5% and 3.8%) to local malaria vectors respectively), whereas organophosphates and carbamates recorded vector susceptibility of 100% for pirimiphos-methyl and 98.7% for bendiocarb. Conclusion Biological efficacy, physical integrity and net attrition during the study period were in conformity with respect to the WHOPES one year net use. LLINs remained effective after one-year of usage. Net ownership was high in the study households. There should be continuous and regular distribution campaigns to maintain high coverage.
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Diouf EH, Diouf M, Dieme C, Swamidoss I, Ngom EHM, Senghor MW, Mbaye M, Konaté A, Coulibaly Y, Tine D, Dia I, Dotson EM, Faye O, Konaté L. Evaluation of the residual efficacy and physical durability of five long-lasting insecticidal nets (LLINs) in Senegal. Malar J 2022; 21:210. [PMID: 35780153 PMCID: PMC9250169 DOI: 10.1186/s12936-022-04230-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 06/06/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The preventive and curative strategies of malaria are based on promoting the use of long-lasting insecticidal nets (LLINs) and treating confirmed cases with artemisinin-based combination therapy. These strategies have led to a sharp decline in the burden of malaria, which remains a significant public health problem in sub-Saharan countries. The objective of this study was to determine and compare the residual efficacy of LLINs recommended by the World Health Organization. METHODS The study was conducted in six villages in two sites in Senegal located in the Sahelo-Sudanian area of the Thiès region, 70 km from Dakar and in Mbagame, a semi-urban zone in the Senegal River Valley. A census was conducted of all sleeping places in each household to be covered by LLINs. Five brands of LLIN were distributed, and every six months, retention rates, net use, maintenance, physical integrity, insecticide chemical content, and biological efficacy were examined for each type of LLIN. RESULTS A total of 3012 LLINs were distributed in 1249 households in both sites, with an average coverage rate of 94% (95% CI 92.68-95.3). After 36 months, the average retention rate was 12.5% and this rate was respectively 20.5%, 15.1%, 10%, 7%, and 3% for Olyset Net®, Dawa Plus® 2.0, PermaNet® 2.0, NetProtect® and Life Net®, respectively. The proportion of LLINs with holes and the average number of holes per mosquito net increased significantly during each follow-up, with a large predominance of size 1 (small) holes for all types of LLINs distributed. During the three-year follow-up, bioassay mortality rates of a susceptible strain of insectary reared Anopheles coluzzii decreased in the following net types: in Dawa Plus® 2.0 (100% to 51.7%), PermaNet® 2.0 (96.6% to 83%), and Olyset Net® (96.6% to 33.3%). Mortality rates remained at 100% in Life Net® over the same time period. After 36 months, the average insecticide content per brand of LLIN decreased by 40.9% for Dawa Plus® 2.0, 31% for PermaNet® 2.0, 39.6% for NetProtect® and 51.9% for Olyset Net® and 40.1% for Life Net. CONCLUSIONS Although some net types retained sufficient insecticidal activity, based on all durability parameters measured, none of the net types survived longer than 2 years.
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Affiliation(s)
- El Hadji Diouf
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal.
| | - Mbaye Diouf
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Constentin Dieme
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Isabel Swamidoss
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | | | - Massila Wagué Senghor
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Modou Mbaye
- Laboratoire de Télédétection Appliquée, LTA/IST/FST/UCAD, Dakar, Sénégal
| | - Abdoulaye Konaté
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Youssouph Coulibaly
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Dome Tine
- Laboratoire de Télédétection Appliquée, LTA/IST/FST/UCAD, Dakar, Sénégal
| | | | - Ellen Marie Dotson
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Ousmane Faye
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
| | - Lassana Konaté
- Laboratoire d'Ecologie Vectorielle et Parasitaire, Département de Biologie Animal, Faculté Des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Sénégal
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Ngongang-Yipmo ES, Tchouakui M, Menze BD, Mugenzi LMJ, Njiokou F, Wondji CS. Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon. Parasit Vectors 2022; 15:230. [PMID: 35754045 PMCID: PMC9233849 DOI: 10.1186/s13071-022-05335-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/23/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are a vital tool in the fight against malaria vectors. However, their efficacy in the field can be impacted by several factors, including patterns of usage, net age, mosquito resistance and the delayed mortality effect, all of which could influence malaria transmission. We have investigated the effectiveness of the various brands of LLINs available in markets and households in Cameroon on pyrethroid-resistant mosquitoes and assessed their post-exposure effect. METHODS Following quality control assessment on a susceptible laboratory mosquito strain, we evaluated the immediate and delayed mortality effects of exposure to LLINs (both newly bough LLINst and used ones collected from households in Elende village, Cameroon, in 2019) using standard WHO cone tests on Anopheles gambiae and Anopheles funestus populations collected from the Centre region of Cameroon. Alive female mosquitoes were genotyped for various resistance markers at different time points post-exposure to evaluate the impact of insecticide resistance on the efficacy of bednets. RESULTS The laboratory-susceptible strain experienced high mortality rates when exposed to all pyrethroid-only brands of purchased nets (Olyset® Net, Super Net, PermaNet® 2.0, Yorkool®, Royal Sentry®) (Mean±SEM: 68.66 ± 8.35% to 93.33 ± 2.90%). However, low mortality was observed among wild An. funestus mosquitoes exposed to the bednets (0 ± 0 to 28 ± 6.7%), indicating a reduced performance of these nets against field mosquitoes. Bednets collected from households also showed reduced efficacy on the laboratory strain (mortality: 19-66%), as well as displaying a significant loss of efficacy against the local wild strains (mortality: 0 ± 0% to 4 ± 2.6% for An. gambiae sensu lato and 0 ± 0% to 8 ± 3.2% for An. funestus). However, compared to the unexposed group, mosquitoes exposed to bednets showed a significantly reduced longevity, indicating that the efficacy of these nets was not completely lost. Mosquitoes with the CYP6P9a-RR and L119F-GSTe2 mutations conferring pyrethroid resistance showed greater longevity after exposure to the Olyset net than their susceptible counterparts, indicating the impact of resistance on bednet efficacy and delayed mortality. CONCLUSION These findings show that although standard bednets drastically lose their efficacy against pyrethroid-resistant field mosquitoes, they still are able to induce delayed mortality in exposed populations. The results of this study also provide evidence of the actual impact of resistance on the quality and efficacy of LLINs in use in the community, with mosquitoes carrying the CYP6P9a-RR and L119F-GSTe2 mutations conferring pyrethroid resistance living longer than their susceptible counterparts. These results highlight the need to use new-generation nets that do not rely solely on pyrethroids.
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Affiliation(s)
- Emilie S. Ngongang-Yipmo
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Magellan Tchouakui
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Benjamin D. Menze
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L35QA UK
| | - Leon M. J. Mugenzi
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Flobert Njiokou
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Parasitology and Ecology Laboratory, Department of Animal Biology and Physiology, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Yaoundé, Cameroon
| | - Charles S. Wondji
- Centre for Research in Infectious Diseases (CRID), P.O. Box 13501, Yaoundé, Cameroon
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L35QA UK
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Nyasa RB, Awatboh F, Kwenti TE, Titanji VPK, Ayamba NLM. The effect of climatic factors on the number of malaria cases in an inland and a coastal setting from 2011 to 2017 in the equatorial rain forest of Cameroon. BMC Infect Dis 2022; 22:461. [PMID: 35562702 PMCID: PMC9101852 DOI: 10.1186/s12879-022-07445-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/05/2022] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Weather fluctuation affects the incidence of malaria through a network of causuative pathays. Globally, human activities have ultered weather conditions over time, and consequently the number of malaria cases. This study aimed at determining the influence of humidity, temperature and rainfall on malaria incidence in an inland (Muyuka) and a coastal (Tiko) settings for a period of seven years (2011-2017) as well as predict the number of malaria cases two years after (2018 and 2019). METHODS Malaria data for Muyuka Health District (MHD) and Tiko Health District (THD) were obtained from the Regional Delegation of Public Health and Tiko District Health service respectively. Climate data for MHD was obtained from the Regional Delegation of Transport while that of THD was gotten from Cameroon Development Coorporation. Spearman rank correlation was used to investigate the relationship between number of malaria cases and the weather variables and the simple seasonal model was used to forecast the number of malaria cases for 2018 and 2019. RESULTS The mean monthly rainfall, temperature and relative humidity for MHD were 200.38 mm, 27.050C, 82.35% and THD were 207.36 mm, 27.57 °C and 84.32% respectively, with a total number of malaria cases of 56,745 and 40,160. In MHD, mean yearly humidity strongly correlated negatively with number of malaria cases (r = - 0.811, p = 0.027) but in THD, a moderate negative yearly correlation was observed (r = - 0.595, p = 0.159). In THD, the mean seasonal temperature moderately correlated (r = 0.599, p = 0.024) positively with the number of malaria cases, whereas MHD had a very weak negative correlation (r = - 0.174, p = 0.551). Likewise mean seasonal rainfall in THD moderately correlated (r = - 0.559, p = 0.038) negatively with malaria cases, contrary to MHD which showed a very weak positive correlation (r = 0.425, p = 0.130). The simple seasonal model predicted 6,842 malaria cases in Muyuka, for 2018 and same number for 2019, while 3167 cases were observed in 2018 and 2848 in 2019. Also 6,738 cases of malaria were predicted for MHD in 2018 likewise 2019, but 7327 cases were observed in 2018 and 21,735 cases in 2019. CONCLUSION Humidity is the principal climatic variable that negatively influences malaria cases in MHD, while higher seasonal temperatures and lower seasonal rain fall significantly increase malaria cases in THD.
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Affiliation(s)
- Raymond Babila Nyasa
- Department of Microbiology and Parasitology, University of Buea, P. O. Box 63, Buea, Cameroon.
- Biotechnology Unit, Faculty of Science, University of Buea, P.O. Box 63, Buea, South West Region, Cameroon.
| | - Fuanyi Awatboh
- Department of Microbiology and Parasitology, University of Buea, P. O. Box 63, Buea, Cameroon
| | - Tebit Emmanuel Kwenti
- Department of Medical Laboratory Sciences, Faculty of Health Science, University of Buea, P.O. Box 63, Buea, South West Region, Cameroon
| | - Vincent P K Titanji
- Biotechnology Unit, Faculty of Science, University of Buea, P.O. Box 63, Buea, South West Region, Cameroon
- Cameroon Christian University, P.O. Box 5, Bali, North West Region, Cameroon
| | - Ndip Lucy M Ayamba
- Department of Microbiology and Parasitology, University of Buea, P. O. Box 63, Buea, Cameroon
- Laboratory for Emerging Infectious Diseases, University of Buea, P.O.Box 63, Buea, South West Region, Cameroon
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Standardised bioassays reveal that mosquitoes learn to avoid compounds used in chemical vector control after a single sub-lethal exposure. Sci Rep 2022; 12:2206. [PMID: 35177630 PMCID: PMC8854624 DOI: 10.1038/s41598-022-05754-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 01/03/2022] [Indexed: 11/21/2022] Open
Abstract
Vector-borne diseases are worldwide public health issues. Despite research focused on vectorial capacity determinants in pathogen transmitting mosquitoes, their behavioural plasticity remains poorly understood. Memory and associative learning have been linked to behavioural changes in several insect species, but their relevance in behavioural responses to pesticide vector control has been largely overlooked. In this study, female Aedes aegypti and Culex quinquefasciastus were exposed to sub-lethal doses of 5 pesticide compounds using modified World Health Organization (WHO) tube bioassays. Conditioned females, subsequently exposed to the same pesticides in WHO tunnel assays, exhibited behavioural avoidance by forgoing blood-feeding to ensure survival. Standardized resting site choice tests showed that pre-exposed females avoided the pesticides smell and choose to rest in a pesticide-free compartment. These results showed that, following a single exposure, mosquitoes can associate the olfactory stimulus of pesticides with their detrimental effects and subsequently avoid pesticide contact. Findings highlight the importance of mosquito cognition as determinants of pesticide resistance in mosquito populations targeted by chemical control.
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8
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Teh RN, Sumbele IUN, Meduke DN, Nkeudem GA, Ojong ST, Teh EA, Kimbi HK. Insecticide-treated net ownership, utilization and knowledge of malaria in children residing in Batoke-Limbe, Mount Cameroon area: effect on malariometric and haematological indices. Malar J 2021; 20:333. [PMID: 34325689 PMCID: PMC8320188 DOI: 10.1186/s12936-021-03860-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 07/20/2021] [Indexed: 11/15/2022] Open
Abstract
Background Insecticide-treated nets (ITNs) are the most widely used interventions for malaria control in Africa. The aim of this study was to assess the ownership and utilization of ITNs and the knowledge of malaria and their effects on malariometric and haematological indices in children living in the Mount Cameroon area. Methods A community-based cross-sectional study involving a total of 405 children aged between 6 months and 14 years living in Batoke–Limbe was carried out between July and October 2017. A semi-structured questionnaire was used to document demographic status, knowledge on malaria and ITN ownership and usage. Venous blood sample was collected from each child to determine the prevalence and intensity of parasitaemia by Giemsa-stained microscopy and full blood count by auto haematology analysis to obtain white blood cell (WBC) and red blood cell (RBC) counts, haemoglobin (Hb) level, haematocrit (Hct), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC). A multilinear regression model was used to determine the relationship between haematological parameter as dependent variable and the independent variables. Results The overall prevalence of parasitaemia, anaemia, knowledge about malaria, ITN ownership, usage and effective usage was 46.7%, 54.7%, 40.7%, 78.8%, 50.9% and 29.9%, respectively. The prevalence of parasitaemia was significantly higher (P < 0.001) in children who ineffectively utilized ITNs (54.9%) than effective users (27.3%). Having knowledge of malaria, negatively correlated with WBC counts (P = 0.005), but positively correlated with Hb levels (P < 0.001), RBC counts (P < 0.001), Hct (P < 0.001), MCV (P < 0.001) and MCH (P < 0.001). ITN use positively correlated with WBC counts (P = 0.005) but negatively with Hb levels (P = 0.004), RBC counts (P = 0.006), and MCH (P < 0.001). Meanwhile, parasitaemia negatively correlated with Hb levels (P = 0.004), RBC counts (P = 0.01), Hct (P = 0.04) and MCHC (P = 0.015). Conclusion There is need for more sensitization on the benefits of using the ITNs to meet up with the intended and expected impact of the free distribution of ITNs. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03860-6.
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Affiliation(s)
- Rene Ning Teh
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon. .,Department of Social Economy and Family Management, Higher Technical Teachers' Training College, University of Buea, Kumba, Cameroon.
| | - Irene Ule Ngole Sumbele
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon.,Department of Microbiology and Immunology, Cornell College of Veterinary Medicine, Ithaca, NY, USA
| | | | - Gillian Asoba Nkeudem
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon.,Department of Social Economy and Family Management, Higher Technical Teachers' Training College, University of Buea, Kumba, Cameroon
| | - Samuel Takang Ojong
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon.,Clinical Diagnostic Laboratory, University of Buea, Buea, Cameroon
| | - Exodus Akwa Teh
- Department of Microbiology, Kenyatta University, Nairobi, Kenya
| | - Helen Kuokuo Kimbi
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon.,Department of Medical Laboratory Sciences, The University of Bamenda, Bambili, Cameroon
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9
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Nyangi M, Kigondu E, Irungu B, Nganga M, Gachanja A, Murigi M, Nyangacha R, Muniu E, Kamau L, Gathirwa J. Integrity, use and care of long-lasting insecticidal nets in Kirinyaga County, Kenya. BMC Public Health 2021; 21:856. [PMID: 33941135 PMCID: PMC8091527 DOI: 10.1186/s12889-021-10882-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 04/21/2021] [Indexed: 11/21/2022] Open
Abstract
Background Vector control is an essential component in prevention and control of malaria in malaria endemic areas. Insecticide treated nets is one of the standard tools recommended for malaria vector control. The objective of the study was to determine physical integrity and insecticidal potency of long-lasting insecticidal nets (LLINs) used in control of malaria vector in Kirinyaga County, Kenya. Method The study targeted households in an area which had received LLINs during mass net distribution in 2016 from Ministry of Health. A total of 420 households were sampled using systematic sampling method, where the household heads consented to participate in the study. A semi-structured questionnaire was administered to assess care and use while physical examination was used to determine integrity. Chemical concentration was determined by gas chromatography mass spectroscopy (GC-MS). Data analysis was done using Statistical Package for Social Sciences (SPSS) version 19. Results After 18 months of use, 96.9% (95% CI: 95.2–98.6%) of the distributed nets were still available. Regarding net utilization, 94.1% of household heads reported sleeping under an LLIN the previous night. After physical examination, 49.9% (95% CI: 43–52.8%) of the bed nets had at least one hole. The median number of holes of any size was 2[interquartile range (IQR) 1–4], and most holes were located on the lower part of the nets, [median 3 (IQR 2–5)]. Only 15% of the nets with holes had been repaired. The median concentration for α-cypermethrin was 7.15 mg/m2 (IQR 4.25–15.31) and 0.00 mg/g (IQR 0.00–1.99) for permethrin. Based on pHI, Chi-square test varied significantly with the manufacturer (X (6, N = 389) = 29.14, p = 0.04). There was no significant difference between nets with different number of washes (X2(2) = 4.55, p = 0.103). Conclusion More than three-quarters of the nets supplied had survived and insecticidal potency was adequate in vector control. Standard procedure for field evaluation of surface insecticidal content available to a mosquito after landing on a net to rest is recommended. Supplementary Information The online version contains supplementary material available at 10.1186/s12889-021-10882-x.
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Affiliation(s)
- Mary Nyangi
- Department of Chemistry, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya.
| | - Elizabeth Kigondu
- Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya
| | - Beatrice Irungu
- Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya
| | - Margaret Nganga
- Department of Chemistry, Kenyatta University, P.O. Box 43844-00100, Nairobi, Kenya
| | - Anthony Gachanja
- Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya
| | - Martin Murigi
- Department of Chemistry, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya
| | - Ruth Nyangacha
- Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya
| | - Erastus Muniu
- Centre for Public Health and Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya
| | - Luna Kamau
- Centre for Biotechnology, Research and Development, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya
| | - Jeremiah Gathirwa
- Centre for Traditional Medicine and Drug Research, Kenya Medical Research Institute, P.O. Box 54840-00200, Nairobi, Kenya
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10
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Fru PN, Cho FN, Tassang AN, Fru CN, Fon PN, Ekobo AS. Ownership and Utilisation of Long-Lasting Insecticidal Nets in Tiko Health District, Southwest Region, Cameroon: A Cross-Sectional Study. J Parasitol Res 2021; 2021:8848091. [PMID: 33623716 PMCID: PMC7875632 DOI: 10.1155/2021/8848091] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 01/06/2021] [Accepted: 01/18/2021] [Indexed: 11/17/2022] Open
Abstract
INTRODUCTION Malaria is and remains a serious health concern in Africa. In Cameroon, where malaria is endemic and a major public health problem, the major control measure put in place is the use of long-lasting insecticidal nets (LLINs). In the Tiko Health District (THD), the challenges have been to assess and to evaluate the ownership and utilisation of LLINs. This study sought to assess the ownership and utilisation rates of LLINs in the THD. Methodology. A cross-sectional survey involving 418 households was conducted in four health areas in the THD. A structured questionnaire was used to collect data on LLIN ownership and utilisation as well as sociodemographic characteristics. RESULTS The ownership of at least one LLIN per household, coverage, and accessibility were, respectively, 89%, 56.2%, and 66.3%, while installing LLINs on all beds in the household, sleeping under LLINs the previous night (SULPN), and universal utilisation were 72%, 24.9%, and 14.1%, respectively. Factors significantly associated with the ownership of at least one LLIN per household were respondent's age and gender. Heat (21.1%) and forgetfulness (6.5%) were the main reasons postulated for irregular utilisation of LLINs. CONCLUSION The ownership LLINs failed to guarantee utilisation and definitely effective control of malaria in the THD, as expected. Continuous and appropriate use of LLINs is indispensable, in addition to periodic sanitation, booster campaigns of LLIN distribution, and evaluation research for effective prevention and control of malaria.
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Affiliation(s)
- Paulette Ngum Fru
- Department of Public Health and Hygiene, Faculty of Health Sciences, University of Buea, P.O. Box 63 Buea, Cameroon
- District Health Service Tiko, South West Regional Delegation of Health, Ministry of Public Health, Cameroon
| | - Frederick Nchang Cho
- Department of Biochemistry and Molecular Biology, Faculty of Science, University of Buea, P.O. Box 63 Buea, Cameroon
- Catholic School of Health Sciences, Saint Elizabeth Hospital Complex, P.O. Box 8 Shisong-Nso, Cameroon
- Central African Network for Tuberculosis, HIV/AIDS and Malaria (CANTAM), University of Buea, P.O. Box 63 Buea, Cameroon
- Global Health Systems Solutions, Cameroon
| | - Andrew N. Tassang
- Department of Obstetrics and Gynaecology, Faculty of Health Sciences, University of Buea, P.O. Box 63, Buea, Cameroon
- Buea Regional Hospital Annex, Buea, Cameroon
- Atlantic Medical Foundation, Mutengene, Cameroon
| | - Celestina Neh Fru
- Atlantic Medical Foundation, Mutengene, Cameroon
- Department of Sociology and Anthropology, Faculty of Social and Management Sciences, University of Buea, P.O. Box 63 Buea, Cameroon
| | - Peter Nde Fon
- Department of Public Health and Hygiene, Faculty of Health Sciences, University of Buea, P.O. Box 63 Buea, Cameroon
- Solidarity Hospital, Buea, Cameroon
| | - Albert Same Ekobo
- Faculty of Sciences, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
- Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Cameroon
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11
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Wheldrake A, Guillemois E, Arouni H, Chetty V, Russell SJ. Textile testing to assess the resistance to damage of long-lasting insecticidal nets for malaria control and prevention. Malar J 2021; 20:47. [PMID: 33468152 PMCID: PMC7816374 DOI: 10.1186/s12936-020-03571-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 12/24/2020] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND LLINs are susceptible to forming holes within a short time in use, compromising their ability to provide long-term physical protection against insect-borne vectors of disease. Mechanical damage is known to be responsible for the majority of holes, with most being the result of snagging, tearing, hole enlargement, abrasion and seam failure, which can readily occur during normal household use. To enable an assessment of the ability of LLINs to resist such damage prior to distribution, a new suite of testing methods was developed to reflect the main damage mechanisms encountered during normal use of LLINs. METHODS Four existing BS EN and ISO standards used by the textile industry were adapted to determine the ability of LLINs to resist the most common mechanisms of real-world damage experienced in the field. The new suite comprised tests for snag strength (BS 15,598:2008), bursting strength (ISO 13938-2:1999), hole enlargement resistance (BS 3423-38:1998), abrasion resistance (ISO 12947-1:1998) and new guidance around the seam construction of LLINs. Fourteen different LLINs were tested using the new suite of tests to evaluate their resistance to damage. RESULTS The resistance to mechanical damage of LLINs is not the same, even when the bursting strength values are comparable. Differences in performance between LLINs are directly related to the fabric design specifications, including the knitted structure and constituent yarns. The differences in performance do not primarily relate to what polymer type the LLIN is made from. LLINs made with a Marquisette knitted structure produced the highest snag strength and lowest hole enlargement values. By contrast, LLINs made with a traverse knitted structure exhibited low snag strength values when compared at the same mesh count. CONCLUSIONS Prequalification of LLINs should consider not only insecticidal performance, but also inherent resistance to mechanical damage. This is critical to ensuring LLINs are fit for purpose prior to distribution, and are capable of remaining in good physical condition for longer. The new suite of test methods enables the performance of LLINs to be assessed and specified in advance of distribution and can be used to establish minimum performance standards. Implementation of these testing methods is therefore recommended.
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Affiliation(s)
- Amy Wheldrake
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Estelle Guillemois
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Hamidreza Arouni
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Vera Chetty
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Stephen J Russell
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK.
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12
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Wheldrake A, Guillemois E, Arouni H, Chetty V, Russell SJ. The causes of holes and loss of physical integrity in long-lasting insecticidal nets. Malar J 2021; 20:45. [PMID: 33468114 PMCID: PMC7816425 DOI: 10.1186/s12936-020-03567-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 12/22/2020] [Indexed: 11/17/2022] Open
Abstract
Background Long-lasting insecticidal nets (LLINs) are expected to last for at least 3 years, but whilst this may be achieved from an insecticidal perspective, physical protection is frequently compromised much earlier because of the rapid accumulation of holes during use. To understand why LLINs are so susceptible to loss of physical integrity, thousands of hole damage sites in LLINs retrieved from the field in Africa and Asia were forensically studied to identify the persistent underlying causes. Methods A total of 525 LLINs consisting of six different brands from five different countries across Africa and Asia were collected from the field after 1 to 3 years in use. More than 42,000 individual sites of hole damage were analysed based on the morphology and size of each individual hole, aided by optical microscopy (OM) and scanning electron microscopy (SEM). The fracture morphology enabled positive identification of the underlying mechanisms of the damage. Results Across all LLINs and geographical settings, mechanical damage is the primary cause of holes and loss of physical integrity in LLINs (63.14% by frequency and 81.52% by area). Snagging is the single most frequent mechanical damage mechanism, whilst the largest sized holes in LLINs result from seam failure and tearing. Abrasion and hole enlargement are also responsible for a progressive loss in the physical integrity of nets. Collectively, these five modes of mechanical damage can be expected to result from normal use of LLINs by households. Evidence of deliberate cutting, burn holes and rodent damage was observed to a lesser degree, which LLINs are not designed to withstand. Conclusions Loss of physical integrity in LLINs is an inevitable consequence of using a vector control product that has an inherently low resistance to mechanical damage during normal use. To improve performance, new specifications based on laboratory textile testing is needed, to assess the resistance of LLIN products to the primary causes of mechanical damage when in use, which are snagging, tearing, abrasion and hole enlargement. Seam construction also needs to meet a revised minimum standard to reduce the risk of a rapid loss of physical integrity during use.
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Affiliation(s)
- Amy Wheldrake
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Estelle Guillemois
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Hamidreza Arouni
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Vera Chetty
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK
| | - Stephen J Russell
- Nonwovens Innovation & Research Institute Ltd, 169 Meanwood Road, Leeds, LS7 1SR, West Yorkshire, UK.
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13
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Olukosi AY, Olakiigbe A, Ajibaye O, Orok BA, Aina OO, Akindele SK, Akinyele OO, Onajole AT, Awolola ST, Arowolo T, Afolabi BM. Socio-economic behavioural indicators of falciparum malaria parasitaemia and moderate to severe anaemia among pregnant women attending antenatal clinics in Lagos, Southwest Nigeria. Malar J 2020; 19:393. [PMID: 33160357 PMCID: PMC7648425 DOI: 10.1186/s12936-020-03462-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 10/26/2020] [Indexed: 11/28/2022] Open
Abstract
Background Incidence of malaria and anaemia are of public health importance especially in pregnant women in endemic regions, due to the negative health consequences to the mother and fetus. This study aimed to assess the pattern of falciparum malaria infection and anaemia, based on malaria prevention methods practiced by participants. Methods A semi-structured tool was used to capture information on demographic, socio-economic and malaria prevention practices from 113 pregnant women attending antenatal clinics in 2 peri-urban health facilities in Lagos, southwest Nigeria. Malaria microscopy was conducted and haematocrit was measured. Logistic regression analysis was performed on the data collated from the survey. Results The prevalence of anaemia among pregnant women was 87.2%. The mean (± sd) packed cell volume (PCV) (%) of the 22 (19.5%) infected subjects (26.8 ± 6.6), was significantly lower (t = −2.60, P value = 0.007) than that of the 91 (80.5%) uninfected subjects (30.8 ± 6.0). The prevalence of infection was highest in the 3rd trimester (n = 40, 35.4%) at 27.5% (11/40) and among those in their first pregnancy (n = 32, 28.3%) at 25.0% (8/32). There was a significant difference (t = −2.23, P-value = 0.01) in the mean PCV % of pregnant women who consumed herbal teas in pregnancy (28.2 ± 5.2) compared to those who did not (30.8 ± 6.6). Regression analysis showed that first pregnancy, anti-malarial use and insecticide-treated nets use the night before study had increased odds of malaria infection in participants (OR = 1.35, P = 0.006, 95% CI 0.52−2.49; OR = 2.3, P = 0.005, 95% CI 0.14−0.41; OR = 1.92, P = 0.001, 95% CI 0.62−5.98) while intermittent preventive treatment (IPT) participation and formal education were strongly and significantly associated with lower risk of parasitaemia (OR = 0.95, P = 0.025, 95% CI 0.41−2.26; OR = 0.44, P = 0.005, 95% CI 0.34−10.50). Conclusion Interventions that will reduce malaria and moderate to severe anaemia, especially in a first pregnancy, should include education on the correct use of long-lasting insecticide-treated bed nets (LLIN), IPT and the dangers of herbal teas in pregnancy.
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Affiliation(s)
- Adeola Y Olukosi
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria.
| | - Abiodun Olakiigbe
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria
| | - Olusola Ajibaye
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria
| | - Bassey A Orok
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria
| | - Olugbenga O Aina
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria
| | - Samuel K Akindele
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria
| | - Olajumoke O Akinyele
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria.,College of Medicine, University of Lagos, Idi-araba, Lagos, Nigeria.,Health, Environment and Development Foundation, Surulere, Lagos, Nigeria
| | | | - Samson T Awolola
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria
| | - Tolulope Arowolo
- Nigerian Institute of Medical Research, 6, Edmund Crescent, PMB 2013, Yaba, Lagos, Nigeria.,College of Medicine, University of Lagos, Idi-araba, Lagos, Nigeria.,Health, Environment and Development Foundation, Surulere, Lagos, Nigeria
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14
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South A, Lees R, Garrod G, Carson J, Malone D, Hastings I. The role of windows of selection and windows of dominance in the evolution of insecticide resistance in human disease vectors. Evol Appl 2020; 13:738-751. [PMID: 32211064 PMCID: PMC7086049 DOI: 10.1111/eva.12897] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 01/23/2023] Open
Abstract
Persistent insecticides sprayed onto house walls, and incorporated into insecticide-treated bednets, provide long-acting, cost-effective control of vector-borne diseases such as malaria and leishmaniasis. The high concentrations that occur immediately postdeployment may kill both resistant and susceptible insects. However, insecticide concentration, and therefore killing ability, declines in the months after deployment. As concentrations decline, resistant insects start to survive, while susceptible insects are still killed. The period of time after deployment, within which the mortality of resistant individuals is lower than that of susceptible ones, has been termed the "window of selection" in other contexts. It is recognized as driving resistance in bacteria and malaria parasites, both of which are predominantly haploid. We argue that paying more attention to these mortality differences can help understand the evolution of insecticide resistance. Because insects are diploid, resistance encoded by single genes generates heterozygotes. This gives the potential for a narrower "window of dominance," within the window of selection, where heterozygote mortality is lower than that of susceptible homozygotes. We explore the general properties of windows of selection and dominance in driving resistance. We quantify their likely effect using data from new laboratory experiments and published data from the laboratory and field. These windows can persist months or years after insecticide deployments. Differential mortalities of resistant, susceptible and heterozygous genotypes, after public health deployments, constitute a major challenge to controlling resistance. Greater attention to mortality differences by genotype would inform strategies to reduce the evolution of resistance to existing and new insecticides.
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Affiliation(s)
- Andy South
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | - Rosemary Lees
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | - Gala Garrod
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | | | - David Malone
- Innovative Vector Control Consortium (IVCC)LiverpoolUK
- Present address:
Bill & Melinda Gates FoundationLondonUK
| | - Ian Hastings
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
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15
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Andronescu LR, Buchwald AG, Coalson JE, Cohee L, Bauleni A, Walldorf JA, Kandangwe C, Mzilahowa T, Taylor TE, Mathanga DP, Laufer MK. Net age, but not integrity, may be associated with decreased protection against Plasmodium falciparum infection in southern Malawi. Malar J 2019; 18:329. [PMID: 31551076 PMCID: PMC6760057 DOI: 10.1186/s12936-019-2930-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/22/2019] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Distribution campaigns for insecticide-treated nets (ITN) have increased the use of ITNs in Malawi, but malaria prevalence remains high even among those using the nets. Previous studies have addressed ITN ownership, insecticide resistance, and frequency of ITN use as possible contributing factors to the high prevalence of malaria infection despite high ITN coverage, but have rarely considered whether the condition of the ITN, or how many people use it, impacts efficacy. This study assessed how ITN integrity, ITN age, and the number of persons sharing a net might mitigate or reduce protective efficacy among self-identified ITN users in Malawi. METHODS From 2012 to 2014, six cross-sectional surveys were conducted in both the rainy and dry seasons in southern Malawi. Data were collected on ITN use, integrity (number and size of holes), and age. Blood samples for detecting Plasmodium falciparum infection were obtained from reported ITN users over 6 months of age. Generalized linear mixed models were used to account for clustering at the household and community level. The final model controlled for gender, household eaves, and community-level infection prevalence during the rainy season. RESULTS There were 9646 ITN users with blood samples across six surveys, 15% of whom tested positive for P. falciparum infection. Among children under 5 years old, there was a 50% increased odds of P. falciparum infection among those sleeping under an ITN older than two years, compared to those using an ITN less than 2 years old (OR = 1.50; 95% CI 1.07-2.08). ITN integrity and number of individuals sharing an ITN were not associated with P. falciparum infection. CONCLUSIONS Older ITNs were associated with higher rates of P. falciparum in young children, which may indicate that insecticide concentrations play a larger role in infection prevention than the physical barrier of an ITN. ITN use was self-reported and the integrity measures lacked the precision of newer methods, suggesting a need for objective measures of ITN use and more precise assessment of ITN integrity.
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Affiliation(s)
- Liana R. Andronescu
- 0000 0001 2175 4264grid.411024.2Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W, Baltimore Street, Baltimore, MD 21201 USA
| | - Andrea G. Buchwald
- 0000 0001 2175 4264grid.411024.2Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W, Baltimore Street, Baltimore, MD 21201 USA ,0000 0001 0703 675Xgrid.430503.1Present Address: University of Colorado School of Public Health, University of Colorado, 13001 E, 17th Place, Mail Stop B119, Aurora, CO 80045 USA
| | - Jenna E. Coalson
- 0000 0001 2168 186Xgrid.134563.6Mel and Enid Zuckerman College of Public Health, University of Arizona, 1295N Martin Ave, Tucson, AZ 85724 USA
| | - Lauren Cohee
- 0000 0001 2175 4264grid.411024.2Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W, Baltimore Street, Baltimore, MD 21201 USA
| | - Andy Bauleni
- 0000 0001 2113 2211grid.10595.38Malaria Alert Centre, University of Malawi College of Medicine, Blantyre, Malawi
| | - Jenny A. Walldorf
- 0000 0001 2175 4264grid.411024.2Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W, Baltimore Street, Baltimore, MD 21201 USA ,0000 0001 2163 0069grid.416738.fPresent Address: Global Immunization Division, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Chifundo Kandangwe
- 0000 0001 2113 2211grid.10595.38Malaria Alert Centre, University of Malawi College of Medicine, Blantyre, Malawi
| | - Themba Mzilahowa
- 0000 0001 2113 2211grid.10595.38Malaria Alert Centre, University of Malawi College of Medicine, Blantyre, Malawi
| | - Terrie E. Taylor
- 0000 0001 2150 1785grid.17088.36Department of Osteopathic Medical Specialties, Michigan State University, 909 Fee Road, East Lansing, MI 48824 USA
| | - Don P. Mathanga
- 0000 0001 2113 2211grid.10595.38Malaria Alert Centre, University of Malawi College of Medicine, Blantyre, Malawi
| | - Miriam K. Laufer
- 0000 0001 2175 4264grid.411024.2Center for Vaccine Development and Global Health, University of Maryland School of Medicine, 685 W, Baltimore Street, Baltimore, MD 21201 USA
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16
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Birhanu A, Asale A, Yewhalaw D. Bio-efficacy and physical integrity of piperonylbutoxide coated combination net (PermaNet ® 3.0) against pyrethroid resistant population of Anopheles gambiae s.l. and Culex quinquefasciatus mosquitoes in Ethiopia. Malar J 2019; 18:224. [PMID: 31272452 PMCID: PMC6610987 DOI: 10.1186/s12936-019-2641-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 01/08/2019] [Indexed: 11/21/2022] Open
Abstract
Background PermaNet® 3.0 is a deltamethrin-treated combination long-lasting insecticidal net with the addition of synergist piperonylbutoxide (PBO) on its roof section. It is designed to overcome the challenge posed by pyrethroid resistant vector populations against mainstream long-lasting insecticidal nets impregnated with pyrethroids only. The objective of this study was to determine insecticide resistance status of Anopheline and Culicine mosquitoes, to evaluate the bio-efficacy of PermaNet® 3.0 nets and to assess household factors affecting the physical integrity of PermaNet® 3.0 after 3 years of use. Methods Insecticide susceptibility test was conducted using the WHO tube test. Bio-activity of PermaNet® 3.0 samples was evaluated using the WHO cone bioassay. Cross-sectional survey was conducted on 150 randomly selected households from two districts to determine household factors affecting net utilization. One hundred fifty PermaNet® 3.0 nets were randomly collected from the community with replacement after 3 years of deployment and physical integrity of each net was assessed. Results Both Anopheles gambiae sensu lato and Culex quinquefasciatus developed resistance against permethrin and deltamethrin. However, following pre-exposure to synergist PBO the susceptibility of mosquito population increased to both permethrin (from 39% without to 92% with PBO against An. gambiae and from 28% without to 94% with PBO against Culex quinquefasciatus) and deltamethrin (from 52% without to 99% with PBO against An. gambiae and from 43% without to 98% with PBO against Culex quinquefasciatus). Eighty percent (80%) mortality was recorded in wild population of An. gambiae s.l. exposed to unused PermaNet® 3.0, but its bioactivity subsequently declined as washing frequency increased from 0 to 20. The PBO coated roof section of unused PermaNet® 3.0 resulted in higher mosquito mortality (100%) compared to the side panels without PBO (85%). House structure, cooking and washing habits, and damage due to household pests were cited as determinants associated with bed net deterioration. Bed net proportionate hole index (pHI) was ranged from 0 to 6064. Of the 150 PermaNet® 3.0 nets assessed 80, 29 and 41 were considered as ‘good’, ‘acceptable’ and ‘too torn’, respectively. Conclusions The bio-efficacy evaluation of PermaNet® 3.0 from Jimma area, southwestern Ethiopia showed moderate efficacy against pyrethroid resistant population of An. gambiae and Culex quinquefasciatus. Thus, NMCPs in parallel to deployment of LLINs, should implement timely insecticide resistance management and integrated vector management strategies to slowdown the evolution and further spread of insecticide resistance. Household factors such as, housing conditions, open flame fire used for cooking and rodent attack were identified as factors contributing to the observed reduced bed net physical integrity in the study area. Universal coverage of bed nets should be accompanied with community awareness creation and training on net utilization and handling.
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Affiliation(s)
- Abaynesh Birhanu
- Department of Biology, College of Natural Sciences, Jimma University, Jimma, Ethiopia
| | - Abebe Asale
- Department of Biology, College of Natural Sciences, Jimma University, Jimma, Ethiopia. .,International Center of Insect Physiology and Ecology, Addis Ababa, Ethiopia.
| | - Delenasaw Yewhalaw
- Faculty of Health Sciences, School of Medical Laboratory Sciences, Jimma University, Jimma, Ethiopia.,Tropical and Infectious Diseases Research Center, Jimma University, Jimma, Ethiopia
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17
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Teh RN, Sumbele IUN, Meduke DN, Ojong ST, Kimbi HK. Malaria parasitaemia, anaemia and malnutrition in children less than 15 years residing in different altitudes along the slope of Mount Cameroon: prevalence, intensity and risk factors. Malar J 2018; 17:336. [PMID: 30249261 PMCID: PMC6154899 DOI: 10.1186/s12936-018-2492-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 09/21/2018] [Indexed: 12/20/2022] Open
Abstract
Background Malaria, anaemia and malnutrition are frequently co-existing diseases that cause significant morbidity and mortality particularly among children. This study measured the prevalence, intensity and evaluated risk factors for malaria parasitaemia, anaemia and malnutrition among children living at low versus high altitude settings in the Mount Cameroon area. Methods A cross-sectional community based survey involving 828 children aged 6 months to 14 years was conducted between July and November 2017. Malaria parasitaemia was confirmed by light microscopy, haemoglobin concentration was measured using an auto haematology analyser, nutritional status was determined from the anthropometric measurements collected, and socioeconomic status related variables by the use of questionnaire. Anaemia and malnutrition were defined according to World Health Organization standards. Associations between predictor variables and primary outcomes were assessed using logistic regression analysis. Results Malaria parasite and anaemia were prevalent in 41.7% and 56.2% of the children, respectively while, malnutrition prevalence was 34.8% with wasting, underweight and stunting occurring in 25.7%, 19.9% and 23.7% of them respectively. Overall malaria parasite geometric mean density was 413/µL of blood (range 100–27,060). The odds of having malaria parasitaemia was highest in children 5–9 years of age [odd ratio (OR) = 1.69, P = 0.006], living in lowland (OR = 1.48, P = 0.008) as well as those whose domestic water was collected from an open source (streams/springs) (OR = 1.81, P = 0.005) than their counterparts. Being < 5 years (OR = 3.15, P = < 0.001) or 5–9 years (OR = 2.20, P < 0.001) of age, having malaria parasite (OR = 2.07, P = < 0.001) and fever in the past 2 days (OR = 1.52, P < 0.04) were identified as significant risk factors of anaemia while the age group < 5 years was the only significant risk (OR = 3.09, P = < 0.001) associated with malnutrition. Conclusion While age specific attention should be given in the control of malaria (5–9 years), anaemia (< 10 years) and malnutrition (< 5 years), the existing malaria control programmes should be revised to integrate anaemia and malnutrition control strategies so as to improve upon the health of the children.
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Affiliation(s)
- Rene Ning Teh
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon
| | | | | | - Samuel Takang Ojong
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon.,Clinical Diagnostic Laboratory, University of Buea, Buea, Cameroon
| | - Helen Kuokuo Kimbi
- Department of Zoology and Animal Physiology, University of Buea, Buea, Cameroon.,Department of Medical Laboratory Sciences, University of Bamenda, Bamenda, Cameroon
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18
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Boussougou-Sambe ST, Eyisap WE, Tasse GCT, Mandeng SE, Mbakop LR, Enyong P, Etang J, Fokam EB, Awono-Ambene PH. Insecticide susceptibility status of Anopheles gambiae (s.l.) in South-West Cameroon four years after long-lasting insecticidal net mass distribution. Parasit Vectors 2018; 11:391. [PMID: 29973260 PMCID: PMC6033221 DOI: 10.1186/s13071-018-2979-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 06/25/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Members of the Anopheles gambiae (s.l.) complex are one of the major vectors of malaria in Africa. LLINs and IRS are the most effective tools used in vector control of malaria. However, their effectiveness may be hampered by the development and spread of insecticide resistance in the target vectors species. The objective of this study was to assess the susceptibility of Anopheles gambiae (s.l.) mosquitoes from South-West Cameroon to deltamethrin, permethrin and to malathion, four years after the mass deployment of LLINs. METHODS Anopheles larvae were collected from Limbe, Tiko and Buea, three cities of the Fako division and reared until adult emergence. Adult mosquitoes from field larvae were identified as belonging to the Anopheles gambiae (s.l.) complex using standard identification keys. Susceptibility of mosquito samples to deltamethrin, permethrin and malathion was assessed using WHO susceptibility tests protocol for adult mosquitoes. Molecular identification of tested samples was performed using the PCR SINE200 protocol and by PCR-RFLP. The kdr alleles were genotyped using the hot ligation oligonucleotide assay (HOLA). RESULTS Two species of the An. gambiae (s.l.) complex, An. coluzzii and An. gambiae (s.s.) were identified in all three study locations with high proportions of An. coluzzii in Limbe (84.06%) and Tiko (92.2%), while in Buea, An. coluzzii (55.6%) and An. gambiae (s.s.) (44.4%) occurred almost in the same proportions. Tested samples were found resistant to pyrethroids (deltamethrin and permethrin) in all locations (< 90% mortality), with > 3-fold increase of KDT50 values compared with the Kisumu susceptible reference strain of An. gambiae (s.s.). However, the mosquito populations from Limbe and Buea were fully susceptible to malathion. The L1014F kdr was found in both An. coluzzii and An. gambiae (s.s.) with the highest frequencies found in An. gambiae (s.l.) populations from Tiko (94%) and Buea (90%) compared with the Limbe population (66%) (P = 0.00063, df = 2). No kdr L1014S was observed in analyzed samples. CONCLUSIONS These findings reemphasize the ongoing development of An. gambiae (s.l.) resistance to pyrethroids used in impregnating LLINs and suggest the use of malathion as an alternative insecticide for IRS in complementarity with LLINs.
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Affiliation(s)
- Stravensky Térence Boussougou-Sambe
- Microbiology and Parasitology Department, University of Buea, P.O. Box 63, Buea, Cameroon.,Institut de Recherche de Yaoundé, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon.,Centre de Recherches Médicales de Lambaréné (CERMEL), P.O Box 242, Lambaréné, Gabon.,Institute of Tropical Medicine, University of Tübingen, Wilhemstrasse 27, P.O. Box 72074, Tübingen, Germany
| | - Wolfgang Ekoko Eyisap
- Institut de Recherche de Yaoundé, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon.,Laboratory of Animal Biology and Physiology, University of Douala, PO Box 24157, Douala, Cameroon
| | - Geraud Canis Taboue Tasse
- Laboratory for Biodiversity and Conservation Biology, University of Buea, P.O. Box 63, Buea, Cameroon.,Department of Zoology and Animal Physiology, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Stanislas Elysee Mandeng
- Institut de Recherche de Yaoundé, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon.,Department of Biology and Animal Physiology, University of Yaoundé I, P.O. Box 3851, Messa, Yaoundé, Cameroon
| | - Lili Ranaise Mbakop
- Institut de Recherche de Yaoundé, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon.,Department of Biology and Animal Physiology, University of Yaoundé I, P.O. Box 3851, Messa, Yaoundé, Cameroon
| | - Peter Enyong
- Microbiology and Parasitology Department, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Josiane Etang
- Institut de Recherche de Yaoundé, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon.,Faculty of Medicine and Pharmaceutical Sciences, University of Douala, P.O. Box 2701, Douala, Cameroon
| | - Eric Bertrand Fokam
- Laboratory for Biodiversity and Conservation Biology, University of Buea, P.O. Box 63, Buea, Cameroon.,Department of Zoology and Animal Physiology, University of Buea, P.O. Box 63, Buea, Cameroon
| | - Parfait H Awono-Ambene
- Institut de Recherche de Yaoundé, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), B.P. 288, Yaoundé, Cameroon.
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