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 Table of Contents  
PERSPECTIVE
Year : 2019  |  Volume : 4  |  Issue : 2  |  Page : 29-32

Use of World Health Organization susceptibility test for malaria vector control in South-Eastern Nigeria: A discourse


1 Department of Public Health, Federal Ministry of Health, Abuja, Nigeria
2 Department of Community Health, University of Uyo, Uyo, Akwa Ibom, Nigeria

Date of Submission14-Jan-2019
Date of Acceptance25-Mar-2019
Date of Web Publication17-Jun-2019

Correspondence Address:
Dr Ibanga Eyo Ekong
Department of Community Health, University of Uyo, P.M.B. 1017, Uyo, Akwa Ibom
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ed.ed_4_19

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  Abstract 


Background: With growing evidence of mosquito vector resistance to pyrethroids and other classes of insecticides globally, we employed one of the two important tools for the monitoring of insecticide resistance in selected states in southeastern part of Nigeria via the World Health Organization (WHO) susceptibility test.
Aim: This study tested the effectiveness of WHO susceptibility test for the use in identifying and monitoring the resistance of Anopheles and Aedes mosquitoes which transmit malaria and arbovirus-related diseases in Nigeria.
Methods: Larval sampling of mosquitoes was embarked upon with ovitraps set in various study sites; eggs were hatched and reared and subsequently subjected to susceptibility tests according to the WHO test procedures.
Summary and Conclusion: Resistance to dichloro diphenyl trichloroethane and the pyrethroids has been established to a large extent. The loss of efficacy of pyrethroids may result in operational failure of disease control programs.

Keywords: Mosquitoes, pyrethroids, susceptibility test


How to cite this article:
Akilah JD, Ekong IE. Use of World Health Organization susceptibility test for malaria vector control in South-Eastern Nigeria: A discourse. Environ Dis 2019;4:29-32

How to cite this URL:
Akilah JD, Ekong IE. Use of World Health Organization susceptibility test for malaria vector control in South-Eastern Nigeria: A discourse. Environ Dis [serial online] 2019 [cited 2022 Jul 1];4:29-32. Available from: http://www.environmentmed.org/text.asp?2019/4/2/29/260516




  Introduction Top


Malaria vector control is a major pillar in the elimination of this disease globally. The disease is prevalent in Nigeria which accounts for 25% of the 219 million cases global morbidity and 19% of the 435,000 global mortality.[1] In almost all parts of the country, favorable environmental conditions and efficient malaria vectors are present for a sustained transmission of the parasite. Comparing achievements over the years indicates that integrated vector control contributes substantially to the reduction of the global burden of malaria.[2]

Vector control is usually implemented using insecticides of various classes. These are done through the use of long-lasting insecticide-treated nets(LLINs) and indoor residual spraying(IRS). By doing so, the vectors of malaria, Anopheles spp., have over the years developed varying degrees of resistance to some classes of insecticides, especially the pyrethroids, which is the dominant insecticide used in LLINs and IRS in Nigeria.[3] Resistance to other classes such as the dichloro diphenyl trichloroethane(DDT) has long been established; interestingly, it has been reported that mosquitoes resistant to DDT are also resistant to pyrethroids, hence the discontinuation of its use for malaria control purposes.[4] Addressing the burning issue of resistance would result in efficiencies in terms of quality and program costs.

Two important tools for the monitoring of insecticide resistance are the World Health Organization(WHO) susceptibility test and United States' Centers for Disease Control and Prevention bottle bioassay. This review is concentrating on the WHO susceptibility test to see its effectiveness for use in identifying and monitoring the resistance of Anopheles and Aedes mosquitoes which transmit malaria and arbovirus-related diseases in Nigeria.


  Context Top


The National Arbo-Virus Research Center(NAVRC) was host to this resistance monitoring study, which involved various parts of the South-East geopolitical zone in 2016. Eleven WHO test papers were received from the National Malaria Elimination Programme, and states in the region were sampled for malaria and/or arbovirus vectors. Immature stages of the vectors were collected and reared to adults at the Center's insectary.

Larval sampling for Anopheles species

To ensure that populations of all possible vectors breeding in the study area were collected, extensive larval sampling was embarked upon. Puddles, rivers, streams, rice fields and other farms, containers, excavations, tire tracks, hoof prints and crab holes, among others, were sampled. Adequate use of dippers, ladles, siphons and pipettes was made to ensure that each site in the study area was combed in the course of prospecting for larvae and pupae.

All the larvae and pupae were put in well-labeled and adequate containers and transported to the insectary of NAVRC. They were then reared to adults, for the susceptibility tests.

Ovitrap setting for Aedes species

Ovitraps were set in various study sites where the study was conducted. The traps targeted mosquitoes of the Aedes species. They were set in shaded areas and left for 48h before they were retrieved. On retrieval, the eggs were dried under room temperature and preserved in air-tight containers.

Soaking/hatching of Aedes eggs

At the insectary, the eggs were introduced into bowls containing nonchlorinated water. The bowls and their contents were then covered with an untreated net to avoid “intruders” introducing foreign eggs. Hatching commenced in a few hours.

Rearing of larvae and handling of pupae

The eggs were hatched in a designated compartment of the insectary and reared in separate bowls. The larvae were fed with Quaker oats and animal feed. This was done in the normal 12h light and dark periods of the day. Rearing water was changed when necessary and feed was replaced, until larvae pupated.

The pupae were introduced into small “pupal cups” by means of disposable pipettes immediately when they were seen. The cups and their contents were then transferred into rearing cages in readiness for adult emergence.

Rearing of adults

As soon as the adults emerged, cotton wool soaked in 10% sugar solution, placed in a  Petri dish More Details, was introduced into each cage. The mosquitoes were maintained with the sugar solution which served as their food. This was changed every other day until the mosquitoes were old enough and sufficient to be utilized for the test.

World Health Organization susceptibility test

To determine the resistance status of the mosquitoes, larvae were collected from the study area and reared to adults at the NAVRC insectary. Nonblood-fed females that were 3–5days postemergence were subjected to susceptibility tests according to the WHO test procedures.[5] Adults from all the sites in the study area were tested against with all the four classes of WHOPES-approved insecticides as shown in [Table1].{Table1}


  Summary of Findings and Discussion Top


Species identification

Only Anopheles gambiae complex, which transmits the malaria parasite, was collected from larval sampling done in the 5 southeastern states. This could be attributable to the fact that most of the breeding sites where the larvae were collected from were puddles, ditches, and guttars–known breeding sites of the complex. Some studies agree with this assertion.[6],[7],[8] However, a few other studies claim otherwise that breeding sitesalso include swamps, vegetations, canals, and other farm sites.[9],[10]

On the other part, Aedes aegypti, Aedes albopictus, and Aedes simpsoni complex were the three species harvested from ovitrapping in three(Anambra, Enugu, and Abia States) of the five states. Studies have shown these species to be present in the southeastern zone of Nigeria.[11],[12] They are responsible for transmitting parasites that cause malaria and lymphatic filariasis.

A. gambiaes. l populations from the five southeast states were susceptible to only insecticide in the carbamate group, bendiocarb. They were all resistant to the pyrethroids(deltamethrin), organophosphates (pirimiphos-methyl) and organochlorines (DDT). Resistance studies on A. gambiae s. l conducted in this zone and contiguous zones reveal a similar pattern.[13],[14]

On the part of Aedes mosquitoes, there was clear resistance to the organochlorine(DDT) family of insecticides. Both A. aegypti and A. albopictus were susceptible to the three other classes of insecticides in Anambra and Enugu states. A. aegypti showed suspected resistance to the pyrethroid, deltamethrin, in Abia state. This has been demonstrated by Self and Pant in a Nigerian study.[15] However, resistance studies conducted in some African countries(Senegal and Nigeria) for Aedes spp. reveal susceptibility to permethrin.[16],[17] Worthy of mention is that only few studies have studied the susceptibility of the Aedes spp. to permethrin and DDT.[18],[19]

Emerging issues: New members of Anopheles Gambiae spp.

Dominance of Anopheles coluzzii, a relatively new member of the Anopheles Gambiae spp., has been observed in Ebonyi State, and is worth further investigation. A.coluzzii has been reported to share the same resources such as vertebrate hosts or freshwater habitats with A. Gambiae s. s.[20],[21],[22] Resistance has also been reported in A. coluzzii.[23]

Perceiving the fact that lymphatic filariasis and malaria are transmitted by the same vectors in Nigeria, there needs to be a concerted effort to jointly control the two diseases by aligning resources, goals, and strategies. This has been agreed to by some studies.[24],[25]


  Conclusion Top


This study has given a broad view on the susceptibility of A. gambiae s. l and Aedes species in the southeastern zone of Nigeria. Generally, resistance to DDT and the pyrethroids has been established, to a large extent. The loss of efficacy of pyrethroids may result in the operational failure of disease control programs, hence a need for synergy.

Study limitation

Paucity of funds affected the number of study sites covered; an increased number of sites would have provided a broader picture on the mosquito vector resistance to insecticides.

Acknowledgments

We acknowledge the NAVRC, Enugu, and the National Malaria Elimination Programme for the support provided.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
World Health Organization. World Malaria Report 2018. Licence: CC BY-NC-SA 3.0 IGO. Geneva: World Health Organization; 2018.  Back to cited text no. 1
    
2.
CibulskisRE, AlonsoP, AponteJ, AregawiM, BarretteA, BergeronL, etal. Malaria: Global progress 2000–2015 and future challenges. Infect Dis Poverty 2016;5:61.  Back to cited text no. 2
    
3.
CorbelV, N'GuessanR. Distribution, mechanisms, impact management of insecticide resistance in malaria vectors: Apragmatic review. In: ManguinS, editor. Anopheles Mosquitoes–New Insights into Malaria Vectors. Rijeka, Croatia: InTech Open Access Publisher; 2013.  Back to cited text no. 3
    
4.
RiveronJM, YuntaC, IbrahimSS, DjouakaR, IrvingH, MenzeBD, etal. A single mutation in the GSTe2 gene allows tracking of metabolically based insecticide resistance in a major malaria vector. Genome Biol 2014;15:R27.  Back to cited text no. 4
    
5.
World Health Organization. Test Procedures for Insecticide Resistance Monitoring in Malaria Vector Mosquitoes. 2nded. Geneva: World Health Organization; 2016.  Back to cited text no. 5
    
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KiflawiM, BlausteinL, MangelM. Oviposition habit selection by the mosquito Culiseta longiareolata in response to risk of predation and conspecific larval density. Ecol Entomol 2003;28:168-73.  Back to cited text no. 6
    
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AlineM, NoutchaE, OkiweluSN. Breeding sites of Anopheles gambiae s. l.(Gilles) in rural low land rainforest, rivers state, Nigeria. Public Health Res 2013;3:50-3.  Back to cited text no. 7
    
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De SilvaPM, MarshallJM. Factors contributing to urban malaria transmission in sub-Saharan Africa: Asystematic review. JTrop Med 2012;2012:819563.  Back to cited text no. 8
    
9.
ServiceMW:Medical Entomology for Students. 4th edition.New York; Cambridge University Press;2008. p.289.  Back to cited text no. 9
    
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MattahPA, FutagbiG, AmekudziLK, MattahMM, de SouzaDK, Kartey-AttipoeWD, etal. Diversity in breeding sites and distribution of Anopheles mosquitoes in selected urban areas of Southern Ghana. Parasit Vectors 2017;10:25.  Back to cited text no. 10
    
11.
OkwokwoNJ, ObiechinaIO, UgbaCN, IrikanuKC, ObianunbaSN, Okoyo-UzochukwuCI, etal. Mosquito species composition in Oba, Idemili South local government area of Anambra state. Researcher 2014;6:51-6.  Back to cited text no. 11
    
12.
BangYH, BownDN, OnwubikoAO. Prevalence of larvae of potential yellow fever vectors in domestic water containers in South-East Nigeria. Bull World Health Organ 1981;59:107-14.  Back to cited text no. 12
    
13.
NwankwoEN, OkoriePN, AchaCT, OkonkwoOE, NwangwuUC, EziheEK. Insecticide resistance in Anopheles gambiae s.l mosquitoes in Awka, Anambra state, Southeast Nigeria. JMosq Res 2017;7:32-7.  Back to cited text no. 13
    
14.
MohammedBR, AbdulsalamYM, DeeniYY. Insecticide resistance to Anopheles spp. mosquitoes(Diptera: Culicidae) in Nigeria: Areview. Int J Mosq Res 2015;2:56-63.  Back to cited text no. 14
    
15.
SelfLS, PantCP. Insecticide susceptibility and resistance in populations of Anopheles gambiae, Culex fatigans and Aedes aegypti in Southern Nigeria. Bull World Health Organ 1966;34:960-2.  Back to cited text no. 15
    
16.
DiaI, DiagneCT, BaY, DialloD, KonateL, DialloM, etal. Insecticide susceptibility of Aedes aegypti populations from Senegal and Cape Verde archipelago. Parasit Vectors 2012;5:238.  Back to cited text no. 16
    
17.
NdamsI, LailaKM, TukurZ. Susceptibility of some species of mosquitoes to permethrin pyrethroid in Zaria, Nigeria. Sci World J 2006;1:15-9.  Back to cited text no. 17
    
18.
AyorindeA, ObohB, OtubanjoO, AlimbaA, OdeigahP. Some toxicological effects of a commonly used mosquito repellent in Lagos state, Nigeria. Res J Environ Toxicol 2014;8:46-52.  Back to cited text no. 18
    
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KemabontaKA, AnikweJC, AdaezeobioraI. Bioefficacy of skeetar in Anopheles gambiae and Aedes aegypti mosquitoes from insecticides resistance areas in Lagos and Oyo state. Biol Agric Healthc 2013;3:122-35.  Back to cited text no. 19
    
20.
LehmannT, DiabateA. The molecular forms of Anopheles gambiae: Aphenotypic perspective. Infect Genet Evol2008;8:737-46.  Back to cited text no. 20
    
21.
CostantiniC, AyalaD, GuelbeogoWM, PombiM, SomeCY, BassoleIH, etal. Living at the edge: Biogeographic patterns of habitat segregation conform to speciation by niche expansion in Anopheles gambiae. BMC Ecol 2009;9:16.  Back to cited text no. 21
    
22.
SimardF, AyalaD, KamdemGC, PombiM, EtounaJ, OseK, etal. Ecological niche partitioning between Anopheles gambiae molecular forms in Cameroon: The ecological side of speciation. BMC Ecol 2009;9:17.  Back to cited text no. 22
    
23.
Chouaïbou M, EtangJ, Brévault T, NwaneP, Hinzoumbé CK, MimpfoundiR, etal. Dynamics of insecticide resistance in the malaria vector Anopheles gambiae s.l. from an area of extensive cotton cultivation in Northern Cameroon. Trop Med Int Health 2008;13:476-86.  Back to cited text no. 23
    
24.
WHO. Weekly Epidemiological Record Relevé 25March 2011. 86thyear/25Mars 2011. No13, 86. World Health Organization; p.113-28. Available from: http://www.who.int/wervia.internet. [Last accessed on 2011May12].  Back to cited text no. 24
    
25.
NjengaSM, MwandawiroCS, WamaeCN, MukokoDA, OmarAA, ShimadaM, etal. Sustained reduction in prevalence of lymphatic filariasis infection in spite of missed rounds of mass drug administration in an area under mosquito nets for malaria control. Parasit Vectors 2011;4:90.  Back to cited text no. 25
    



 
 
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