A.K. Mishra , S.K. Chand  , T.K. Barik , V.K. Dua  & K. Raghavendra

Journal of Vector Borne Diseases

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J Vector Borne Dis 49, March 2012, pp. 39–41Insecticide resistance status in Anopheles culicifacies in Madhya Pradesh,central IndiaA.K. Mishra1, S.K. Chand1, T.K. Barik2, V.K. Dua3 & K. Raghavendra21National Institute of Malaria Research, Field Unit, Jabalpur; 2National Institute of Malaria Research, New Delhi; 3National Institute ofMalaria Research, Field Unit, Hardwar, IndiaKey words Anopheles culicifacies; insecticide resistance; India; Madhya Pradesh; malaria; vectorMalaria is one of the most common vector-borne dis-eases widespread in tropical and subtropical regions1.Vector control constitutes an important aspect of vectorborne disease control programme. Use of insecticides forvector control is an effective strategy but is also associ-ated with the development of insecticide resistance in thetarget disease vectors and is one of the reasons for failuresof disease control in many countries including India. Ear-lier, indoor residual spraying (IRS) with insecticides wasthe key component of malaria control and was respon-sible for spectacular reduction in disease incidence duringthe early 20th century2–5. Still IRS and insecticide-treatedmaterials are in use as adulticides in vector control6. Sev-eral studies have been done on the susceptibility status ofadult mosquitoes in different locations and on differentspecies in India7–12.Anopheles culicifacies (Diptera: Culicidae) is a prin-cipal malaria vector in rural and peri-urban areas and con-tributes about 65% of malaria cases in India13. To date, inIndia, DDT (organochlorine), malathion (organophospho-rus) and deltamethrin, cyfluthrin, alpha-cypermethrin andlambda-cyhalothrin (synthetic pyrethroids) are the com-monly used insecticides for vector control in public health.Resistance to DDT in An. culicifacies is reported wide-spread throughout the country14–16, and also to malathionin the states of Maharashtra, Gujarat, Tamil Nadu andUttar Pradesh17–20 and there are few reports of decreasedsusceptibility to synthetic pyrethroids in various parts ofthe country21–23 including Chhattisgarh (Bhatt et al. un-published data).   Recently, surveys were conducted in theyear 2009–10 in 9 tribal districts of Madhya Pradesh toassess the susceptibility status in An. culicifacies to DDT,malathion and deltamethrin.Madhya Pradesh is the largest state in the country(308,252 km2) having 50 districts with forest cover ofabout 31% with intense perennial malaria transmission inthese areas. The state has about 60 million population with12 million tribal population. The main vector control in-tervention is IRS and in some places insecticide treatednets (ITN) and long-lasting insecticidal nets are also inuse. The major malaria vector in this state is An.culicifacies.The insecticide susceptibility of An. culicifacies toDDT, malathion and deltamethrin was tested during Au-gust and September, 2009 in  Balaghat, Betul, Chhindwara,Dindori, Guna, Jhabua, Mandla, Shadol and Sidhi dis-tricts using standard WHO adult susceptibility kit andmethods24. The districts selected for assessment of sus-ceptibility to insecticides in An. culicifacies have almostsimilar ecotype, vector prevalence and employ same vec-tor control strategies. For adult insecticide susceptibilitytest, insecticide impregnated papers were procured fromVector Control Research Unit, University Sans Malaysia,Malaysia. Female mosquitoes were collected from the studyvillages of the district in the early hours using a mouthaspirator and torch light25. The mosquitoes collected fromfield were held in a cloth cage and transported to baselaboratory with a wet towel around the cage. Mosquitoeswere identified to species based on morphological charac-ters using a standard key.  Mosquitoes were exposed todifferent insecticides, DDT, malathion and deltamethrinfor 1 h. At least 3–4 test replicate exposures to the giveninsecticide and respective controls were run simulta-neously. After exposure to diagnostic dosages of the giveninsecticides for one hour, mosquitoes were held for 24 hholding period at 27 ± 2ºC temperature and 70–80% rela-tive humidity. Mortality was determined by scoring thedead and alive mosquitoes and results were expressed aspercent mortality. In experiments, where mortality in con-trol replicates was between 5 and 20%, the mortality wascorrected using Abbott’s formula26 and tests with >20%control mortality were discarded. Based on the observedpercent corrected mortality as per the WHO criteria24 ,the data are presented in three classes namely susceptible–mortality >98%, verification required (tolerance)–mortalitybetween 81% and 97%, and resistant –mortality <80%.The results of the present study are given in Table 1.An. culicifacies was found resistant to DDT in all the dis- J Vector Borne Dis 49, March 201240tricts surveyed and to malathion in Sidhi, Shadol, Mandla,Betul, Chhindwara and Jhabua districts and was tolerantto malathion in Districts Dindori and Balaghat and thespecies was susceptible in Guna district. While todeltamethrin, the species registered resistance in DistrictsMandla and Dindori, tolerant in Districts Sidhi, Shadol,Balaghat, Betul, Chhindwara and Jhabua but the specieswas still susceptible in Guna district. The observed mor-tality in different districts varied from 0 to 28.3% for DDT,57.1 to 100% for malathion and 64.3 to 100% fordeltamethrin (Table 1). The results indicated that the spe-cies was highly resistant to DDT in all the districts whileto malathion the species was moderately resistant and wasmostly tolerant to deltamethrin.Further stratification of the group of villages in thestudy districts was made based on spray history in the last5–10 yr as Group A (IRS with pyrethroids), Group B (IRSwith DDT), and Group C (without insecticide IRS) (Table2).It may be stated that DDT is being sprayed in theseareas since the inception of National Malaria Control ac-tivities in early-1950s.  Decreased mortality in An.culicifacies to deltamethrin was found in Group A areathat received deltamethrin IRS in the last5–10 yr (Table 2). All the areas have shown resistance toDDT and also to malathion, however, in areas withoutdeltamethrin spray the species registered higher mortalityto deltamethrin in the range of 94.7 to 96.4%. Malathionwas also not sprayed regularly in these areas and the ob-served levels of resistance to malathion could be due toselection by its use in agriculture/forestry in the absenceof its use in public health sprays.  Similar observationswere made earlier in district Chhindwara, Madhya Pradeshon the presence of resistance to malathion in An.culicifacies (Raghavendra unpublished). Surprisingly, inthe present study, An. culicifacies has shown resistance toDDT in all the areas irrespective of its withdrawal fromIRS and replaced with other insecticide or no insecticidespray. This could be due to increased genetic stability ofDDT resistance gene as was observed in An. culicifaciesin Surat. A study carried out in Surat in 2005 and 2006,wherein pyrethroid IRS was discontinued earlier since 2002resulted in reversion of pyrethroid resistance to suscepti-bility from 60% in 2001 to > 96% in 2005 and 2006 but,the species was still reporting resistance to DDT andmalathion even after their withdrawal from IRS respec-tively for 30 and 9 yr.  The relatively low levels of rever-sion against DDT and malathion in Surat could be due toincreased genetic stability of DDT and malathion resis-tance in the populations27.In conclusion, the present data indicated developmentof resistance to pyrethroids in An. culicifacies is of greatconcern to Indian malaria control programme as it is inextensive use in public health programmes for IRS andfor impregnation of bed nets. There is a need for regularmonitoring to assess insecticide susceptibility to formu-late effective vector control strategies.ACKNOWLEDGEMENTSAuthors thank NVBDCP for funding this study andOfficer Incharge, NIMR, IDVC Field Unit and staff,Table 2. Susceptibility status of Anopheles culicifacies to DDT,malathion and deltamethrin in three different insecticidespray areas of Madhya PradeshVillages with different   Insecticide tested % Mortalityinsecticide spraysGroup-ASP sprayed since DDT 4% 11.2 (780) Rlast 5–10 yr Malathion 5% 73.4 (780) RDeltamethrin 0.05% 77.4 (780) RGroup-BDDT spray DDT 4% 16.2 (690) RMalathion 5% 87.5 (720) VRDeltamethrin 0.05% 96.5 (690) VRGroup-CWithout insecticide DDT 4% 5.9* (630) R IRS since last Malathion 5% 77.4 (630) R  5–10 yr Deltamethrin 0.05% 94.7 (630) VRTable 1. Susceptibility status of Anopheles culicifacies to DDT,malathion and deltamethrin in nine districts ofMadhya PradeshDistrict % MortalityInsecticideDDT Malathion Deltamethrin4%  5%  0.05%Shahdol 8.8 (180) R 77.8 (180) R 93.8 (180) VRSidhi 7.5*(360) R 78.8 (360) R 94.1 (360) VRDindori 12.8 (180) R 80 (180) R 71.6 (180) RMandla 13.3 (180) R 78.3 (180) R 76.6 (180) RBalaghat 6.7 (120) R 84 (150) VR 92 (150) VRBetul 12.4 (225) R 72.4 (225) R 83.1 (225) VRChhindwara 9.2 (315) R 74.9 (315) R 85.9* (315) VRGuna 26.6 (300) R 100 (300) S 100 (270) SJhabua 6.6 (240) R 65.4 (240) R 87 (240) VR*Figures in parentheses indicate number of mosquitoes tested; S–Susceptible (mortality > 98%); R—Resistant (mortality <80%); VR—Tolerant (mortality 81–97%).*Figures in parentheses indicate number of mosquitoes tested. Mean-ing of abbreviations as in Table 1. 41Mishra et al: Insecticide susceptibility of An. culicifacies in Madhya Pradesh, IndiaJabalpur, Madhya Pradesh for technical support.REFERENCES1. 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Bio-efficacy and persistence of insecticides ontreated surfaces. Report of the WHO informal consultation.Geneva: World Health Organization 1998. WHO/CDC/MAL/98.12.25. Manual of practical entomology in malaria, vector bionomicsand organization of anti-malaria activities, pt II.  Geneva : Off-set Publication, WHO 1975.26. Abbott WS. A method of computing the effectiveness of insec-ticide. J Econ Entomol 1925; 18: 265–7.27. Raghavendra K, Verma V, Srivastava HC, Gunasekaran K,Sreehari U, Dash AP. Persistence of DDT, malathion anddeltamethrin resistance in Anopheles culicifacies after their se-quential withdrawal from indoor residual spraying in Surat dis-trict, India. Indian J Med Res 2010; 132: 260–4.Correspondence to: Dr A.K. Mishra, National Institute of Malaria Research Field Unit, RMRC Campus, Jabalpur–482 003, India.E–mail: akmishra05@gmail.comReceived: 7 October 2011 Accepted in revised form: 2 February 2012

Insecticide resistance status in Anopheles culicifacies in Madhya Pradesh, central India

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Insecticide resistance status in Anopheles culicifacies in Madhya Pradesh, central India

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