Occurrence and Distribution of Phenotypic and Genotypic Resistant Strain of Anopheles arabiensis to insecticides and Plasmodium Sporozoites Infection in Khartoum State, Sudan

Abstract

This study was conducted in Khartoum state during March 2011 to February 2014 to assess the susceptibility status of Anopheles arabiensis the malaria vector to different classes of insecticides in Khartoum state. Furthermore, insecticides resistance genes (kdr, AChE) in concomitance with infection of Anopheles arabiensis the vector of malaria were studied. Anopheline mosquito larvae and pupae were collected from possible larval habitats in nine sentinel sites using standard collection methods and reared to adult in the insectary to conduct WHO-bioassays. Moreover, wild adult mosquitoes were collected from resting places in 20 sites to conduct molecular analysis for detection of knockdown resistance genes (kdr; L1014F and L1014S), acetylcholinesterase (ace-1R; G119S) alleles and Plasmodium sporozoites infection. The collection sites of larvae and wild adults were marked using Global Positioning System (GPS). A sub-samples from emerged adult Anopheles mosquitoes from the colony-reared and the wild ones were identified using proper entomological keys and analyzed by PCR using species-specific primers. Using WHO procedure, susceptibility tests were conducted on adults of An. arabiensis from nine sentinel sites in Khartoum State using dichloro-diphenyl-trichloroethane (DDT 4%), fenitrothion 1%, malathion 5%, propoxur 0.1%, permethrin 0.75%, deltamethrin 0.05% and lambdacyhalothrin 0.05%. Mortality rates and knockdown times (KDT50 and KDT95) of insecticides for An. arabiensis were calculated. Moreover, a well-designed socio-economic questionnaire was used to assess the knowledge, attitude and practice of the public health workers and farmers on the uses of pesticides in the field. In this study, only two types of larval habitats were identified; these were habitats formed from the drinking water pipes leakage and irrigation canal. Moreover, a total of 8325 female An. arabiensis were exposed to insecticides. Populations of An. arabiensis from Khartoum State were susceptible to only fenitrothion 1% and lambdacyhalothrin 0.05% with overall mean percentage mortalities 100±0.12 and 100±0.45 respectively. A significant differences in the mortality rates in An. arabiensis due to DDT 4%, permethrin 0.75% and deltamethrin 0.05% were observed between the sentinel sites. Moreover, An. arabiensis from Khartoum North area was resistant to most insecticides used more than populations from Khartoum and Omdurman areas. Anopheles arabiensis from urban areas was resistant to only malathion 5% whereas in the periurban areas, it was resistant to DDT 4%, malathion 5% and permethrin 0.75%. Although, the spatial distribution of the resistant strains of An. arabiensis was clear for insecticides used in different sentinel sites, the seasonal variation for the susceptibility status in this species did not follow a clear pattern. Both kdr (L1014F and L1014S) alleles and G119S mutation that confer resistance to pyrethroids and organochlorines, and organophosphate and carbamates insecticides respectively were detected in low frequencies An. arabiensis and with limited distribution in Khartoum State to periurban and urban areas respectively. Although, P. falciparum infection was detected in the An. arabiensis collected from three out of four sites, no kdr or G119S mutations were detected in concomitance with malaria parasites infections in this species. Plasmodium falciparum was detected in 6.7% of the females An. arabiensis. However, no kdr mutations was observed in concomitant with Plasmodium infection in these populations. The results of the KAP surveys revealed that 5 insecticides have been used in agriculture and public health practices in Khartoum State during the five last years. However, the public health workers and the farmers showed a relatively low knowledge about the proper uses of pesticides and insecticides in both practices respectively. In conclusion, this study reports, for the first time, the identification of the L1014S and G119S mutations in An. arabiensis populations in Khartoum. Moreover, An. arabiensis the main malaria vector in different sentinel sites which categorized as urban and periurban areas in the three administrative areas in Khartoum showed multiple resistance to most insecticides used. However, the cross-resistance between DDT and permethrin, in addition to the multiple resistance in malaria vector has significant implications for the control of malaria vector populations in Sudan since pyrethroids insecticides are used in LLINs and indoor residual sprays (IRS). Therefore, more investigations are needed to determine the occurrence and frequency of resistant gene(s) in Khartoum State and other regions in Sudan to have a corrective management strategies and effective vector control programmes in the future.