Anopheles stephensi

Anopheles stephensi is a primary mosquito vector of malaria in urban India and is included in the same subgenus as Anopheles gambiae, the primary malaria vector in Africa.[1] A. gambiae consists of a complex of morphologically identical species of mosquitoes, along with all other major malaria vectors; however, A. stephensi has not yet been included in any of these complexes.[2] Nevertheless, two races of A. stephensi exist based on differences in egg dimensions and the number of ridges on the eggs; A. s. stephensi sensu stricto, the type form, is a competent malaria vector that takes place in urban areas, and A. s. mysorensis, the variety form, exists in rural areas and exhibits considerable zoophilic behaviour, making it a poor malaria vector.[3] However, A. s. mysorensis is a detrimental vector in Iran.[4] An intermediate form also exists in rural communities and peri-urban areas, though its vector status is unknown.[4] About 12% of malaria cases in India are due to A. stephensi.[5]

Anopheles stephensi
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Insecta
Order:
Diptera
Family:
Culicidae
Genus:
Anopheles
Species:
A. stephensi
Binomial name
Anopheles stephensi
Liston, 1901

In November 2015, an American research group demonstrated that an A. stephensi with genetic modifications could be rendered incapable of transmitting malaria, and that 99.5% of the mutant mosquitoes' offspring were also immune.[6]

Habitat

In rural areas, the larvae of A. stephensi may exist in many aquatic habitats, such as ponds, streams, swamps, marshes, and other sources of standing water.[7] They may also occupy smaller environments, such as tree holes, leaf axils, and man-made containers.[8] The larvae of A. s. mysorensis exclusively prefer to occupy stone pots and earthenware containers.[4] This species is also able to endure high levels of salinity, and have been found to breed readily in water where the salinity is equal to or even surpassing that of sea water.[9] Furthermore, A. stephensi breeds in a number of different water-bodies in urban areas, but predominantly in artificial containers, walls, overhead tanks, and ground level water tanks.[10]

Most larvae feed on microorganisms and particle matter suspended in water.[8] However, later in development, adult males feed on the nectar of flowers, whereas females take blood meals, which help produce viable eggs.[3]

Distribution

A. stephensi is a subtropical species that predominates in the Indian subcontinent (except Nepal and Sri Lanka)[3] and is also distributed across the Middle East and South Asia region, existing in countries such as: Afghanistan, Bahrain, Bangladesh, China, Egypt, India, Iran, Iraq, Oman, Pakistan, Saudi Arabia, and Thailand.[2] A. stephensi was discovered to be established on the continent of Africa, in Djibouti on the Horn of Africa in 2012[11] or 2013,[12] in 2016 in Ethiopia,[13][11] Sri Lanka in 2017,[11] and in 2019 in the Republic of the Sudan/North Sudan.[11]

Seasonal activity

A. stephensi is considered to be endophilic and endophagic, regardless that it may feed outdoors during the summer, when weather is warmer and humans and animals are more likely to sleep outside in the open air.[9] Although indoor feeding habits have shown no variation between seasons, adult females tend to feed more often at night during the summer rather than during the day in winter.[4] A. stephensi shows a greater preference for humans over animals in urban areas, where they can be found year-round.[4]

Parasites

A. stephensi is an important vector for the human malaria species Plasmodium falciparum.[14]

References
  1. Valenzuela, J.G., Francischetti, I.M.B., Pham, V.M., Garfield, M.K., & Ribeiro, J.M.C. (2003). Exploring the salivary gland transcriptome and proteome of the Anopheles stephensi mosquito. Insect Biochemistry and Molecular Biology, 33, 717-732.
  2. Dash, A.P., Adak, T., Raghavendra, K., & Singh, O.P. (2007). The biology and control of malaria vectors in India. Current Science, 92, 1571-1578.
  3. Malhotra, P.R., Jatav, C.P., & Chauhan, R.S. (2000). Surface morphology of the egg of Anopheles stephensi stephensi sensu stricto (Diptera, Culicidae). Italian Journal of Zoology, 62, 147-151.
  4. Sinka, M.E., Bangs, M.J., Manguin, S., Chareonviriyaphap, T., Patil, A.P., Temperley, W.H., Gething, P. W., Elyazar, I.R.F., Kabaria, C.W., Harbach, R.E., & Hay, S.I. (2011). The dominant Anopheles vectors of human malaria in the Asia-Pacific region: occurrence data, distribution maps and bionomic précis. Parasites & Vectors, 4, 1-46.
  5. Tikar, S.N., Mendki, M.J., Sharma, A.K., Sukumaran, D., Veer, V., Prakash, S., & Parashar. B.D. (2011). Resistance status of the malaria vector mosquitoes, Anopheles stephensi and Anopheles subpictus towards adulticides and larvicides in arid ad semi-arid areas of India. Journal of Insect Science, 11, 1-10.
  6. Gemuteerde mug moet malaria bestrijden Nederlandse Omroep Stichting 24 November 2015 (in Dutch)
  7. Rueda, L.M. (2008). Global diversity of mosquitoes (Insecta: Diptera: Culicidae). Hydrobiologia, 595, 477-487.
  8. Harbach, R.E. (2007). The Culicidae (Diptera): a review of taxonomy, classification and phylogeny. Zootaxa, 1668, 591-629.
  9. Maouchehri, A.V., Javadian, E., Eshghy, N., & Motabar, M. (1976). Ecology of Anopheles stephensi Liston in southern Iran. Tropical and Geographical Medicine, 28, 228-232.
  10. Jeyabalan, D., Arul, N., Thangamathi, P. (2003). Studies on effects of Pelargonium citrosa leaf extracts on malarial vector, Anopheles stephensi Liston. Bioresource Technology, 89, 185-189.
  11. "Vector alert: Anopheles stephensi invasion and spread". WHO. 2019-08-26. Retrieved 2020-11-11.
  12. Faulde, Michael K.; Rueda, Leopoldo M.; Khaireh, Bouh A. (2014). "First record of the Asian malaria vector Anopheles stephensi and its possible role in the resurgence of malaria in Djibouti, Horn of Africa". Acta Tropica. Elsevier BV. 139: 39–43. doi:10.1016/j.actatropica.2014.06.016. ISSN 0001-706X.
  13. Carter, Tamar E.; Yared, Solomon; Gebresilassie, Araya; Bonnell, Victoria; Damodaran, Lambodhar; Lopez, Karen; Ibrahim, Mohammed; Mohammed, Seid; Janies, Daniel (December 2018). "First detection of Anopheles stephensi Liston, 1901 (Diptera: culicidae) in Ethiopia using molecular and morphological approaches". Acta Tropica. 188: 180–186. doi:10.1016/j.actatropica.2018.09.001. ISSN 0001-706X. PMID 30189199.
  14. "Mosquitos, mosquito bite, mosquito transmitted diseases".

Further reading
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