https://orcid.org/0009-0004-7417-8255
Figures
Abstract
Mosquito-borne viral diseases such as dengue fever, chikungunya, and yellow fever have been documented in Ethiopia since the 1960s. However, the efficacy of public health insecticides against Aedes aegypti that transmits these viruses remains poorly understood in the country, particularly in the Afar Region. Thus, the aim of the study was to assess the susceptibility status of Ae. aegypti to deltamethrin, permethrin, alpha-cypermethrin, pirimiphos-methyl, bendiocarb, and propoxur insecticides. Larvae and pupae of Aedes species were collected from Awash Arba, Awash Sebat, and Werer towns of the Afar Region of Ethiopia during July-October 2022, brought to the Aklilu Lemma Institute of Pathobiology, insectary and reared to adults. Non-blood-fed, 3–5 days-old females Ae. aegypti were exposed to pyrethroid, carbamate, and organophosphate insecticide impregnated papers in tube test following the standard guidelines. Knockdown rates were noted at 10 minutes interval until one hour. The mortality in mosquitoes was recorded 24 hours after 60 minutes of exposure. The mortality rates of Ae. aegypti exposed to propoxur were 87% in all the study towns. Similarly, 88% mortality in Ae. aegypti was recorded when tested with bendiocarb in Awash Sebat and Awash Arba towns. Suspected resistance of Ae. aegypti (95% mortality) to alpha-cypermethrin was observed in Awash Arba town. However, Ae. aegypti collected from all the three sites was observed to be susceptible to deltamethrin, permethrin, and pirimiphos-methyl. Ae. aegypti was resistant to 0.1% bendiocarb and 0.1% propoxur and possibly resistant to 0.05% alpha-cypermethrin. On the other hand, it was susceptible to 0.05% deltamethrin, 0.75% permethrin, and 0.25% pirimiphos-methyl. Thus, vector control products with deltamethrin, permethrin, and pirimiphos-methyl can be used in the control of adult Ae. aegypti in the Afar Region of Ethiopia. However, further studies should be carried out to evaluate the susceptibility status of Ae. aegypti to alpha-cypermethrin in the Awash Arba area.
Citation: Seid M, Aklilu E, Animut A (2024) Susceptibility status of Aedes aegypti (Diptera: Culicidae) to public health insecticides in Southern Afar Region, Ethiopia. PLoS ONE 19(8): e0309335. https://doi.org/10.1371/journal.pone.0309335
Editor: James Colborn, Clinton Health Access Initiative, UNITED STATES OF AMERICA
Received: January 29, 2024; Accepted: August 9, 2024; Published: August 23, 2024
Copyright: © 2024 Seid et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: The study was financially supported by Addis Ababa University, the Vice President for Research and Technology Transfer Office through its thematic research grant. "The funder had no role in study design, data collection and analysis, the decision to publish, or the preparation of the manuscript.
Competing interests: The authors declared that there is no conflict of interest.
Introduction
The ever-increasing outbreaks of arboviral diseases have drawn public health attention in several countries around the world [1]. East African countries, including Kenya, Somalia, Djibouti, Eritrea, and Ethiopia are epicenters of outbreaks of arboviral diseases such as dengue, yellow fever and chikungunya [2–4]. In Ethiopia, yellow fever caused about 30,000 deaths from over 200,000 infections during 1960 and 1962 [5]. Recently, there have been yellow fever outbreaks in South Omo [6] and dengue fever outbreaks in Dire Dawa city administration, Somali Regional State, Gewane and Amibara districts of Afar Regional State [7, 8]. In addition, chikungunya outbreaks were reported in Dire Dawa city administration, Afar and Somali Regional States [9, 10]. All these outbreaks with potentially unrecognized and/or underreported deaths could not be associated with particular virus due to the highly limited laboratory facilities in the country.
Mosquitoes transmit over 90% of the viral pathogens through their bites, among which Ae. aegypti is the leading vector followed by Ae. albopictus [11, 12]. Ae. aegypti is anthropophilic and occurs in close proximity to human habitations [13, 14]. Ae. aegypti has two morphological subspecies (ecotypes); the domestic Ae. aegypti aegypti and sylvan Ae. aegypti formosus [15, 16]. In Ethiopia, Ae. aegypti, Ae. bromeliae, Ae. vittatus, Ae. hirsutus, Ae. simpsoni complex, and Ae. africanus have been implicated as potential vectors of viral diseases [6, 8, 17–19].
In the absence of effective therapeutic drugs and vaccines to treat and control mosquito-borne viral diseases, prevention largely depends on vector control with mainly public health insecticides [13]. Pyrethroids such as deltamethrin, alpha-cypermethrin, permethrin, and organophosphates pirimiphos-methyl and fenitrothion are among the public health insecticides used against Aedes mosquitoes [20]. However, the potential resistance to the insecticides may adversely affect the implementation of the control strategy in endemic areas [21]. Mosquitoes could resist insecticides through their inherent ability to detoxify and avoid contact either behaviorally or physiologically [22].
Evidence from many African countries indicates that Anopheles and Aedes mosquitoes developed resistance to insecticides [23–25]. For instance, in Ethiopia, malaria-transmitting Anopheles arabiensis has developed resistance to insecticides in several areas of the country, including the Amibara district of Afar Regional State [25, 26]. The cause of the resistance could be frequent use of the insecticides in indoor residual spraying and long-lasting insecticidal nets for the control of mosquito-borne diseases in the area [21] or in agriculture pest control [27]. However, the susceptibility status of Aedes mosquitoes to currently used insecticides is lacking in the country.
Recently, the Ethiopian Public Health Institute prepared an arboviral disease vectors surveillance and control guideline in 2021, emphasizing the use of chemical and environmental methods. Vector control by chemical methods such as fumigation, repellents, and residual insecticide surface treatments were implemented in Dire Dawa city administration and Somali Regional State during dengue fever and chikungunya outbreaks (EPH, 2021, unpublished). Unfortunately, there is a scarcity of evidence on the efficacy of the insecticides for the control of virus transmitting Aedes species in the Southern Afar Region in the presence of increased reports of viral disease incidence and prevalence. Therefore, assessing the effectiveness of the existing public health insecticides to control Aedes species is crucial to strengthening the arboviral disease prevention and control programs in the country. This inspired us to generate baseline data on the susceptibility status of Ae. aegypti to public health insecticides in the Southern part of the Afar Regional State of Ethiopia.
Materials and methods
Study sites
The study was carried out in Awash Arba, Werer, and Awash Sebat towns, Gabi-Rasu Zone (Zone 3), of Afar Regional State, Ethiopia. The Awash Arba and Werer towns are located about 250 km to the north-east of Addis Ababa at 9.33453°N latitude, 40.181385°E longitude, and an altitude range of 720 to 1100 meters above sea level (masl) (Central Statistics Agency, 2019, unpublished). Awash Arba and Werer sites were selected from Amibara district, which is about 30 km apart (Fig 1). Agro-ecologically, these two towns are semi-arid, with temperatures ranging from 25°C to 35°C and an average annual rainfall of 530 mm. The communities are pastoralist and agro-pastoralist, in which they mainly obtain income from livestock rearing and other agricultural crop production [28].
A map showing the locations of the three study areas: Awash Sebat, Awash Arba and Werer towns, in the Southern Afar Region, Ethiopia.
Awash Sebat town administration is located 214 km north-east of Addis Ababa at 8.98810°N latitude and 40.163936°E longitude (Central Statistics Agency, 2019, unpublished). Its altitude ranges from 820 masl to 1120 masl, and the temperatures vary from 22.6°C to 30.6°C. The town and its surroundings receive a mean annual rainfall of 606.6 mm.
The study areas are found in the middle of the Awash Valley, where infectious diseases such as malaria, chikungunya, and dengue fever are common [29]. Considerable attention has been given by the Regional government to achieve better health in the region, including the three towns [30]. The Region has hospitals, health centers, clinics, and health posts in different zones and districts. There is one hospital, one clinic, five health centers, and a few private clinics. Insecticides such as deltamethrin, permethrin, alpha-cypermethrin, pirimiphos-methyl bendiocarb, and propoxur have been used for indoor residual spraying or pyrethroids in long-lasting insecticide nets for the control of malaria and arboviral diseases in these towns [26, 31]. Similarly, since maize, sorghum, and cotton productions are common in the area, agricultural chemicals such as soil fertilizers and agricultural pesticides are being used to increase crop production [32].
Larval collection and rearing
A cross-sectional study was designed to collect larvae and pupae of Aedes species from July-October, 2022 in the Awash Sebat, Awash Arba, and Werer towns. The study towns were selected purposively in collaboration with the local district health professionals and on the basis of the recent outbreak reports of dengue fever and chikungunya virus (Awash Sebat town and Amibara district health bureaus, 2022, unpublished). The towns were surveyed once per month. Larvae and pupae were collected from different positive habitats, including tyres, water storage drums, discarded plastic and metallic containers, using standard dipper (350 ml), ladles, pipets, and nets. The larvae and pupae collected from each habitat were transferred into labelled plastic jars, transported to the insectary of the Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Ethiopia, and reared to adults under standard laboratory conditions. Tetra cichlid floating fish food (®/TM/©2019 Germany) was provided as food to the larvae. The emergence of larvae into pupae was checked each morning, and pupae were collected in glass flasks and transferred into (30 cm x 30 cm x 30 cm) netted cages. Emerged adult Ae. aegypti were kept at 27 ± 2°C temperature, 75 ± 10% relative humidity, and provided access to feed on a 10% sucrose solution until the bioassay tests. Emergent adults were identified by species using morphological taxonomic keys for Aedes species [33].
Phenotypic susceptibility status of Aedes aegypti
Prior to insecticide susceptibility tests, sugar-fed females Ae. aegypti were starved for 2 hrs. Non-blood-fed, 3-5-old females Ae. aegypti mosquitoes were tested for their susceptibility to insecticides in tube test following the World Health Organization’s insecticide testing procedures [20, 34]. They were exposed to pyrethroids (0.05% deltamethrin, 0.05% alpha-cypermethrin, and 0.75% permethrin), carbamates (0.1% bendiocarb and 0.1% propoxur), and organophosphate (0.25% pirimiphos-methyl) [34]. The insecticides were selected for the study because they are among the insecticide classes which have been used for the control of public health important mosquitoes in Ethiopia and the study areas. Similar concentrations of insecticides were used to test the susceptibility of Ae. aegypti in Tanzania [35]. However, we did not follow the World Health Organization’s recommended discriminating concentrations for Aedes species due to the unavailability of insecticide-impregnated papers at the time of the experiment. This practical obstacle required a strategy that looked into the alternative doses of the insecticides. In each test, 20 females of Ae. aegypti were exposed to each of the five treatment replicates and two control test tubes, making a total of 140 mosquitoes in a single test. The exposed mosquitoes were observed for 60 minutes at an interval of 10 minutes to observe their knockdown. After an hour, the exposed females were transferred into holding tubes and kept for 24 hrs at 27.0 ± 2.0°C temperature, 75 ± 10% relative humidity, and were offered cotton wool pads soaked in a 10% sugar solution. The mortality in mosquitoes was recorded 24 hrs after 60 minutes of exposure. Ae. aegypti susceptibility test was repeated for alpha-cypermethrin in Awash Arba town since Ae. aegypti populations appeared to be possibly phenotypic resistance to this insecticide. However, in Werer town, the susceptibility status of Ae. aegypti to bendiocarb was not conducted due to insufficient mosquito samples.
Ethical issues
We obtained ethical approval from the Institutional Review Board (IRB) of the Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Ethiopia (June 13, 2022; ALIPB IRB/80/2022). Written permission letters were obtained from the district health bureaus and health centers in the towns. The households were informed about the objective of the study, and their agreements were sought prior to the larvae and pupae collection.
Data analysis
Mortality was determined on the basis of the dead and alive females of Ae. aegypti after the 24 hours recovery period. Susceptible were those with a mortality in the range of 98–100%, possibly or suspected for resistance were with a mortality 90–97%, and resistant if mortality was <90% [20]. Probit analysis was used to determine the estimated duration at which 50% (KDT50) and 95% (KDT95) of the exposed Ae. aegypti mosquitoes were knocked-down. Overall adult mortalities and knockdown times were computed using SPSS Software version 20.
Results
Knockdown effect of insecticides against Aedes aegypti
The knockdown times of Ae. aegypti exposed to insecticides are given in Table 1. The time to knockdown 50% (KDT50) of Ae. aegypti exposed to deltamethrin ranged from 12.15 to 17.06 minutes whereas KDT95 of the insecticide ranged from 18.74 to 34.01 minutes. The KDT95, (34.01 minutes) observed for Ae. aegypti collected from Awash Sebat was found to be longer than for other towns (Table 1). On the other hand, Ae. aegypti exposed to permethrin showed the lowest KDT50 in Awash Arba town (KDT50, 5.11). Overall, the KDT50 and KDT95 of Ae. aegypti varied among Ae. aegypti across the study localities.
Susceptibility status of Aedes aegypti to insecticides
The percentage mortalities of Ae. aegypyi mosquito populations against insecticides are presented in Figs 2–4. Accordingly, Ae. aegypti mosquitoes showed phenotypic resistance to bendiocarb and propoxur insecticides, with mortality rates of 88% and 87% respectively in Awash Sebat town. There was 100% mortality of Ae. aegypti to deltamethrin, permethrin, alpha-cypermethrin, and pirimiphos-methyl in Awash Sebat town (Fig 2). All Ae. aegypti in the control group showed 0% mortality in all study sites.
Error bars represent 95% confidence intervals.
Error bars represent 95% confidence intervals.
Error bars represent 95% confidence intervals.
Ae. aegypti populations from Awash Arba were also observed to be resistant to bendiocarb and propoxur but were possibly resistant to alpha-cypermethrin (95% mortality) (Fig 3). Ae. aegypti populations were fully susceptible to deltamethrin, permethrin, and pirimiphos-methyl insecticides in this town.
Mortality in Ae. aegypti from Werer town was 87% with propoxur and 99% with alpha-cypermethrin (Fig 4). However, Ae. aegypti from this site was found to be fully susceptible to deltamethrin, permethrin, and pirimiphos-methyl.
Discussion
Recent outbreaks of dengue fever and chikungunya virus fever in Eastern and the North-eastern parts of Ethiopia especially in Dire Dawa city administration, Somali Regional State, Amibara and Gewane districts of Afar Regional State require the control of the Aedes species that transmit the viruses. Insecticide-based mosquito control is underway in Ethiopia in general and in the Afar Regional State in particular [7, 36]. In so doing, there has been continuous evaluation of the efficacy of the insecticides against malaria-transmitting Anopheles species, but there is a scarcity of research findings conducted to control Aedes species either chemically, biologically, or by other means of vector control strategies in the country [37]. Thus, the control of the viral disease transmitting Ae. aegypti vector is poorly investigated and needs detailed research. As far as our knowledge is concerned, this study was the first in its kind to report the susceptibility status of Ae. aegypti to public health insecticides in the Southern Afar Regional State, and there are limited data to compare our findings to others in the country.
Aedes aegypti is considered by some authors to be highly exophilic [38], exophagic, and a daytime biter [39]. It usually feeds on human and other vertebrate hosts, as described in previous study [39]. However, it may tend to be endophilic and endophagic, in which case it rests and feeds indoors [40]. This makes control of Ae. aegypti and the Aedes-borne diseases it transmits more difficult [41]. As a result, different intervention tools have been adopted to control Aedes mosquitoes including indoor residual insecticide spraying and long-lasting insecticide treated nets in addition to managing their breeding habitats [42].
In the present study, Ae. aegypti showed higher KDT50 and KDT95 as compared to the study conducted in Sudan on deltamethrin insecticide. For instance, the KDT50 and KDT95 observed for deltamethrin in Sudan were 13 and 19 minutes, respectively which were lower than the current study in Awash Sebat and Werer towns [43]. However, the study conducted in Nigeria revealed that the KDT50 of deltamethrin was almost twice the KDT50 observed in Awash Sebat [44]. A relatively similar permethrin KDT50 was observed in Awash Sebat town and Mlabani, Tanzania. However, higher KDT95 with deltamethrin and permethrin was found for Mlabani than all the present study towns [35]. Overall, the tube test revealed that Ae. aegypti was susceptible to deltamethrin in Sudan and Tanzania but possibly resistant in Nigeria.
Aedes aegypti was found to show varying susceptibility to different insecticides. Ae. aegypti populations were observed to be phenotypically resistant to bendiocarb with < 90% mortality. Ae. aegypti resistance to bendiocarb was also reported in the previous study in Tanzania during the rainy season [35]. However, this finding was contrary to the findings observed from Sudan, Nigeria, and Cambodia [43–45]. The World Health Organization has recommended in 2022 that the insecticide discriminating dose of bendiocarb for Ae. aegypti be changed from its initial 0.1% to 0.2% [34]. Thus, future efficacy studies of bendiocarb should target the 0.2% concentration [34].
In the present study, Ae. aegypti was found to be resistant to propoxur 0.1% concentration in all the study towns. Similar finding was reported in Thailand, where the efficacy of Ae. aegypti mortality to propoxur was 83%, which indicated the phenotypic resistance of Ae. aegypti to propoxur in this area [46].
The possible contributing factors to the emergence of phenotypic resistance of Ae. aegypti in the present study areas could be frequent uses of insecticide treated bed nets and indoor residual insecticide spraying to control mosquito-borne diseases as previously indicated [47]. On the other hand, Ethiopia has had a long history of utilizing pesticides to increase agricultural production and improve human health since 1964 [48, 49]. Unfortunately, however, agricultural pesticides induce insecticides resistance selection pressure in different ways. For instance, pesticides used for agriculture pest control can select vector control insecticides because of a similar mode of action, and bio-active ingredients might drive a section pressure for chemical based insecticide control tools [27]. Similarly, agro-pesticides used in agriculture may increase insecticide tolerance as the pesticides are washed into mosquito breeding habitats, which confer resistance mechanisms at the adult stage [50]. Thus, the emergence of insecticide resistance in bendiocarb and propoxur insecticides in the present study could potentially arise from the frequent exposure of the mosquito to carbamate insecticides in agriculture used as agricultural pesticides or herbicides. In addition, Ae. aegpti resistance to propoxur and bendiocarb may occur as a result of mutations in the insecticide target site enzyme Acetyl-cholinesterase (AChE) as observed in Cuba [51].
Pyerethroids such as deltamethrin and alpha-cypermethrin are commonly used to control malaria and other mosquito-borne diseases in Ethiopia. In the present study, the pyrethroid alpha-cypermethrin showed less than 97% of the mortality of adult Ae. aegypti populations in the Awash Arba town, which revealed the emergence of possibly resistance in Ae. aegypti in this area. This might be due to the frequent use of pyrethroids including alpha-cypermethrin in the insecticide-treated nets to control malaria and agricultural pesticides in this area as discussed above. This may lead to failures in vector control intervention programs in the study area and elsewhere in the country if resistance management is not undertaken. Similar findings were reported in Ghana [23].
Completely/fully susceptible Ae. aegypti populations were observed to the organophosphate, i.e., pirimiphos-methyl in all the study areas. Likewise, the study conducted in Cambodia [45] reported similar findings in that Ae. aegypti populations were completely susceptible to pirimiphos-methyl even in its lower concentration than the present study. However, this finding was contrary to the finding reported in Nigeria [44]. Similarly, Ae. aegypti was also fully susceptible to deltamethrin and permethrin in the study areas. These findings were contrary to the findings reported in Malaysia [52], where resistance phenotypes were observed in deltamethrin and permethrin. However, similar findings were reported in Tanzania [35] and in Peru [53], where deltamethrin showed greater than 99% of mortality in adult Ae. aegypti. Thus, these findings could serve as a baseline for the Ethiopian Ministry of Health and the Afar Region Health Bureau to implement chemical interventions, particularly the pyrethroids deltamethrin, permethrin, and organophosphate pirimiphos-methyl, either in the form of aerial spray or insecticidal surface treatment, to reduce the density of Ae. aegypti and prevent the burden of arboviral diseases during disease outbreaks in different parts of the country.
Conclusion
The present study showed that Ae. aegypti populations were resistant to bendiocarb and propoxur, possibly resistant to alpha-cypermethrin, and fully susceptible to deltamethrin, permethrin, and pirimiphos-methyl insecticides. Thus, based on the findings, regular monitoring of insecticide resistance should be carried out in the study areas and elsewhere in Ethiopia, including molecular aspects, to mark and evaluate resistance patterns. Moreover, proper use of existing insecticides is mandatory to prevent Ae. aegypti resistance to insecticides in the study areas. In addition, the organophosphate pirimiphos-methyl can be used in addition to deltamethrin and permethrin in the control of adult Ae. aegypti mosquitoes in Ethiopia.
Supporting information
S1 Table. Observed knockdown times (in minutes) and number of knocked-down female Ae. aegypti exposed to insecticides during the 60 minutes in Awash Sebat, Awash Arba and Werer towns of Southern Afar, July-October 2022.
https://doi.org/10.1371/journal.pone.0309335.s001
(DOCX)
S2 Table. Mortality of Ae. aegypti 24 hrs, after 1 hr exposed to insecticides Awash Sebat, Awash Arba and Werer towns, Southern Afar Regional State, Ethiopia, July-October, 2022.
https://doi.org/10.1371/journal.pone.0309335.s002
(DOCX)
S3 Table. Representative GPS points of the Awash Sebat, Awash Arba and Werer towns of Southern Afar Regional State, Ethiopia recorded during Ae. aegypti larvae and pupae collection.
https://doi.org/10.1371/journal.pone.0309335.s003
(DOCX)
Acknowledgments
The authors would like to acknowledge the Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Ethiopia, for providing us with field and laboratory materials and insecticide impregnated papers. We would also like to thank the vector biology and control unit staffs, Mr. Wosen Sisay, for his technical assistance in the insectary. Finally, we appreciated all the communities and data collectors from Awash Sebat, Awash Arba, and Werer towns, for their collaboration during the study period.
References
- 1. Braack L, et al. Mosquito-borne arboviruses of African origin: review of key viruses and vectors. Parasit vectors. 2018;11(29):1–26. pmid:29316963
- 2. Langat SK, et al. Origin and evolution of dengue virus type 2 causing outbreaks in Kenya: Evidence of circulation of two cosmopolitan genotype lineages. Virus Evolution. 2020;6(1):1–9. pmid:32523778
- 3. Gutu MA, et al. Another dengue fever outbreak in Eastern Ethiopia-An emerging public health threat. PLoS Negl Trop Dis. 2021;15(1):1–16. pmid:33465086
- 4. Usman A, et al. Dengue fever outbreaks in Eritrea, 2005–2015. Glob health research policy. 2016;1(17):1–8. pmid:29202065
- 5. Serie C, et al. Studies on yellow fever in Ethiopia. Epidemiologic study. Bulletin of the World Health Organization. 1968;38(6):879–884.
- 6. Lilay A, et al. Re-emergence of yellow fever in Ethiopia after 50 years, 2013: epidemiological and entomological investigations. BMC Infect Dis. 2017;17(343):1–6. pmid:28506254
- 7. Woyessa AB, et al. The first acute febrile illness investigation associated with dengue fever in Ethiopia, 2013: a descriptive analysis. The Ethio J Health Dev. 2014;28(3):155–161.
- 8. Mekuriaw W, et al. Epidemiological, entomological and climatological investigation of the 2019 dengue fever outbreak in Gewane district, Afar Region, North-east Ethiopia. Insects. 2022;13(1066):1–13. pmid:36421969
- 9. Geleta D, et al. Epidemiological description of chikungunya virus Outbreak in Dire Dawa Administrative City, Western Ethiopia, 2019. Int J Clin Exp Med Sci. 2020;6(3):41–45. https://doi.org/10.11648/j.ijcems.20200603.13
- 10.
Alayu M, et al. Risk factors for Chikungunya outbreak in Kebridhar City, Somali Ethiopia, 2019. Unmatched case-control study. bioRxiv. 2020:1–20.
- 11. Gubler DJ. Dengue, urbanization and globalization: the unholy trinity of the 21st century. Trop Med and health. 2011;39(4SUPPLEMENT):3–11. pmid:22500131.12
- 12. Li Y, et al. Urbanization increases Aedes albopictus larval habitats and accelerates mosquito development and survivorship. PLoS Negl Trop Dis. 2014;8(11):1–12. pmid:25393814
- 13.
World Health Organization. Dengue: guidelines for diagnosis, treatment, prevention and control. World Health Organization. 2009;1–148. 2376296314
- 14. Powell JR. Mosquito-borne human viral diseases: why Aedes aegypti? The Am J Tro Med and Hyg. 2018;98(6):1563–1565. pmid:29557341
- 15. Mattingly P. Taxonomy of Aedes aegypti and related species. Bulletin of the World Health Organization. 1967;36:552–554.
- 16. Rose NH, et al. Climate and urbanization drive mosquito preference for humans. Current Biol. 2020;30(18): 1–29. pmid:32707056
- 17. Getachew D, et al. Breeding sites of Aedes aegypti: potential dengue vectors in Dire Dawa, East Ethiopia. Interd Perspectives Infect Dis. 2015;2015:1–8. https://doi.org/10.1155/2015/706276 2643571218
- 18. Ferede G, et al. Distribution and larval breeding habitats of Aedes mosquito species in residential areas of northwest Ethiopia. Epidemiol and health. 2018;40:1–7. pmid:29748457
- 19. Waldetensai A, et al. Aedes Mosquitoes Distribution and Risk of Yellow fever transmission in Gurage Zone South-west Ethiopia. Ethiop J Public Health Nutr. 2021;4(1):1–10.
- 20. World Health Organizatio. Monitoring and managing insecticide resistance in Aedes mosquito populations: interim guidance for entomologists. 2016;1–11.
- 21. Moyes CL, et al. Contemporary status of insecticide resistance in the major Aedes vectors of arboviruses infecting humans. PLoS Negl Trop Dis. 2017;11(7):1–20. pmid:28727779
- 22. World Health Organization. Global plan for insecticide resistance management in malaria vectors 2012;13–132.
- 23. Owusu-Asenso CM, et al. Spatiotemporal distribution and insecticide resistance status of Aedes aegypti in Ghana. Parasit Vectors. 2022;15(61):1–14. https://doi.org/10.1186/s13071-022-05179-w 35183249
- 24. Mathias L, et al. Habitat productivity and pyrethroid susceptibility status of Aedes aegypti mosquitoes in Dar es Salaam, Tanzania. Infect Dis Poverty. 2017;6(102):1–10. https://doi.org/10.1186/s40249-017-0316-0 2859565325
- 25. Kenea O, et al. Impact of combining indoor residual spraying and long-lasting insecticidal nets on Anopheles arabiensis in Ethiopia: results from a cluster randomized controlled trial. Malaria J. 2019;18(182):1–11. pmid:31126286
- 26. Messenger LA, et al. Insecticide resistance in Anopheles arabiensis from Ethiopia (2012–2016): a nationwide study for insecticide resistance monitoring. Malaria J. 2017;16(469):1–14. https://doi.org/10.1186/s12936-017-2115-2 2915102427
- 27. Nkya TE, et al. Impact of environment on mosquito response to pyrethroid insecticides: facts, evidences and prospects. Insect biochemistry and molecular biol. 2013;43(2013):407–416. pmid:23123179
- 28. Mekuyie M, Jordaan A and Melka Y. Understanding resilience of pastoralists to climate change and variability in the Southern Afar Region, Ethiopia. Climate Risk Managt. 2018;20:64–77.
- 29. Gebru H, Ahmed J. Water quality assessments as implication to human health: a case study in Awash Sebat and its surrounding areas, Afar, Ethiopia. Inter J Earth Sci and Engi. 2016;9(5):1999–2008.
- 30. Goshu D, et al. Socioeconomic Development in Afar Region: Achievements, Gaps and Priorities. 2021.
- 31. Ministry of Health Ethiopia. Vector control operational manual for malaria elimination in Ethiopia. 2017;1–56.
- 32. Sileshi G, Zemedkun A and Nurhussien S. Assessment of the pesticide use, practice and hazards on cotton growing farmers in the Awash Valley Ethiopia. AgriRxiv. 2021(2021):1–22. https://cabidigitallibrary.org
- 33. Rueda LM. Pictorial keys for the identification of mosquitoes (Diptera: Culicidae) associated with dengue virus transmission. Walter Reed Army Inst of Research Washington Dc Department of Entomology. 2004;1–60.
- 34.
World Health Organization. Manual for monitoring insecticide resistance in mosquito vectors and selecting appropriate interventions. World Health Organization. 2022;1–55.
- 35. Kahamba NF, et al. Habitat characteristics and insecticide susceptibility of Aedes aegypti in the Ifakara area, south-eastern Tanzania. Parasit Vectors. 2020;13(53) 1–15. pmid:32033619
- 36. Ahmed YM, Salah AA. Epidemiology of dengue fever in Ethiopian Somali region: retrospective health facility based study. Cent Afr J Public Health. 2016;2(2):51–6.
- 37. Waldetensai A, et al. Aedes mosquito responses to control interventions against the Chikungunya outbreak of Dire Dawa, Eastern Ethiopia. Inter J Trop Insect Sci. 2021;41:2511–2520. https://doi.org/10.1007/s42690-021-00430-w
- 38. Diouf B, et al. Resting behavior of blood-fed females and host feeding preferences of Aedes aegypti (Diptera: Culicidae) morphological forms in Senegal. J Med Entomol. 2021;58(6):2467–2473. pmid:34165556
- 39. Ponlawat A, Harrington LC. Blood feeding patterns of Aedes aegypti and Aedes albopictus in Thailand. J Med Entomol. 2005;42(5):844–849. pmid:16363170
- 40. Diallo D, Diallo M. Resting behavior of Aedes aegypti in southeastern Senegal. Parasit Vectors. 2020;13(356):1–7. pmid:32682436
- 41. Bartlow AW, et al. Forecasting zoonotic infectious disease response to climate change: mosquito vectors and a changing environment. Veter sci. 2019;6(40):1.20. pmid:31064099
- 42. Lima EP MOF Goulart and Rolim Neto ML. Meta-analysis of studies on chemical, physical and biological agents in the control of Aedes aegypti. BMC Public Health. 2015;15(858):1–14. pmid:26341708
- 43. Husham A, Abdalmagid M and Brair M. Status susceptibility of dengue vector; Aedes aegypti to different groups of insecticides in Port Sudan City-Red Sea State. Sudanese J Public Health. 2010;5(4):199–202.
- 44. Ukpai OM, Ekedo CM. Insecticide susceptibility status of Aedes aegypti in umudike, Ikwuano lga Abia State, Nigeria. Animal Research Inter. 2018;15(3):3082–3089.
- 45. Boyer S, et al. Monitoring insecticide resistance of adult and larval Aedes aegypti (Diptera: Culicidae) in Phnom Penh, Cambodia. Parasit Vectors. 2022;15(44):1–7. pmid:35101104
- 46. Pethuan S, et al. Biochemical studies of insecticide resistance in Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus (Diptera: Culicidae) in Thailand. Trop Biomed. 2007;24(1):7–15. pmid:17568372
- 47. Barbosa S, et al. Modelling the impact of insecticide-based control interventions on the evolution of insecticide resistance and disease transmission. Parasit vectors. 2018;11(482):1–21. pmid:30153869
- 48. Mengistie B. Policy-practice nexus: pesticide registration, distribution and use in Ethiopia. SM J Environ Toxicol. 2016;2(1):1006–1019.
- 49. Negatu B, Dugassa S, Mekonnen Y. Environmental and health risks of pesticide use in Ethiopia. J Health Pollution. 2021;11(30):1–12. pmid:34267988
- 50. Poupardin R, et al. Cross-induction of detoxification genes by environmental xenobiotics and insecticides in the mosquito Aedes aegypti: impact on larval tolerance to chemical insecticides. Insect biochemistry molecular biolo. 2008;38(2008):540–551. pmid:18405832
- 51. Bisset J, Rodríguez MM, Fernández D. Selection of insensitive acetylcholinesterase as a resistance mechanism in Aedes aegypti (Diptera: Culicidae) from Santiago de Cuba. J Med Entomol. 2006;43(6):1185–1189. pmid:17162951
- 52. Ishak IH, et al. Contrasting patterns of insecticide resistance and knockdown resistance (kdr) in the dengue vectors Aedes aegypti and Aedes albopictus from Malaysia. Parasit Vectors. 2015;8(181):1–13. pmid:25888775
- 53. Pinto J, et al. Susceptibility to insecticides and resistance mechanisms in three populations of Aedes aegypti from Peru. Parasit Vectors. 2019;12(494):1–11. pmid:31640810