Anopheles stephensi, a highly competent vector of Plasmodium falciparum and P. vivax, is considered an efficient vector of urban malaria. Until 2011, the reported distribution of An. stephensi was confined to certain countries in South-East Asia and large parts of the Arabian Peninsula. Since then, the vector has been reported from Djibouti (2012), Ethiopia (2016), Sri Lanka (2017) and most recently from the Republic of the Sudan (2019). In the Horn of Africa, the vector seems to be spreading from its first site of detection (Djibouti) to neighbouring countries.
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© Armauer Hansen Research Institute/Temesgen Ashine
An. stephensi typically breeds in containers or cisterns with clean water, and the vector appears to quickly adapt itself to the local environment; it also survives extremely high temperatures during the dry season, when malaria transmission usually reaches a seasonal low. In addition, the genetic background of introduced An. stephensi seems to confer resistance to multiple insecticide classes, posing potential challenges to its control.
WHO considers the spread of An. stephensi to be a major potential threat to malaria control and elimination in Africa and southern Asia. This vector alert has been developed to urge WHO Member States and their implementing partners – especially those in and around the Horn of Africa, the Republic of the Sudan and surrounding geographical areas, and in Sri Lanka – to take immediate action.
This vector alert provides detailed information on:
- what African countries, especially those in and around the Horn of Africa, should do now;
- what countries should do in areas where the vector has been detected; and
- how interventions should be monitored and evaluated.
→ Vector alert: Anopheles stephensi invasion and spread (2023 update)