Anopheles stephensi

Description

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. 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. 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. However, A. s. mysorensis is a detrimental vector in Iran. An intermediate form also exists in rural communities and peri-urban areas, though its vector status is unknown. About 12% of malaria cases in India are due to A. stephensi. 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. 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. They may also occupy smaller environments, such as tree holes, leaf axils, and man-made containers. The larvae of A. s. mysorensis exclusively prefer to occupy stone pots and earthenware containers. 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. 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. A. stephensi is a subtropical species that predominates in the Indian subcontinent (except Nepal and Sri Lanka) 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. A. stephensi was discovered to be established on the continent of Africa, in Djibouti on the Horn of Africa in 2012 or 2013, in 2016 in Ethiopia, Sri Lanka in 2017, and in 2019 in the Republic of the Sudan/North Sudan.