- Anopheles stephensi is a species of mosquito that has become an increasingly significant public health concern due to its role as an efficient vector of Plasmodium falciparum and Plasmodium vivax, the parasites responsible for malaria in humans.
- Traditionally native to South Asia and parts of the Middle East, An. stephensi has gained global attention in recent years due to its rapid geographic expansion into urban areas of Africa, where it threatens to disrupt malaria control efforts in regions previously less affected by urban malaria transmission.
- Unlike many other Anopheles species that are typically associated with rural or forested environments, Anopheles stephensi is highly adapted to urban settings. It breeds in artificial water containers commonly found in cities—such as water storage tanks, cisterns, rooftop containers, and discarded items that collect rainwater. This urban adaptability allows the species to thrive in densely populated areas, increasing the risk of malaria outbreaks in cities that were historically less vulnerable to the disease due to the absence of suitable vector species.
- Morphologically, adult An. stephensi mosquitoes are medium-sized, with spotted wings and a slender, dark-colored body. They exhibit classic Anopheles characteristics, such as resting at an angle with their abdomen pointing upward. The females are the blood-feeding sex and exhibit both endophilic (indoor-resting) and endophagic (indoor-biting) behavior, although they can also feed and rest outdoors depending on local conditions. They are opportunistic feeders, taking blood meals from both humans and animals, although human preference increases their vectorial capacity.
- Anopheles stephensi is a particularly competent vector of both major human malaria parasites. It is capable of transmitting P. falciparum, the most lethal form of malaria, as well as P. vivax, which is more widespread and difficult to eliminate due to its ability to remain dormant in the liver and cause relapses. The mosquito’s rapid life cycle, high vector competence, and resistance to common insecticides make it a formidable vector, particularly in urban environments where traditional rural malaria interventions may not be effective.
- The species’ recent invasion into parts of Africa, including Djibouti, Ethiopia, Sudan, and Nigeria, has alarmed global health organizations. Previously, malaria transmission in African cities was relatively low because the dominant malaria vectors (Anopheles gambiae and Anopheles funestus) were more rural in habitat preference. The spread of An. stephensi into African cities—where many people live in crowded conditions with limited access to safe water and healthcare—poses a serious challenge to malaria control programs, which were not designed with urban transmission in mind.
- Adding to the concern is the mosquito’s growing resistance to insecticides, particularly pyrethroids, which are commonly used in insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). This resistance diminishes the effectiveness of key malaria control tools and underscores the urgent need for new vector control strategies tailored to urban environments. Proposed measures include targeted larval source management, novel insecticides, genetic control approaches, and community-based interventions to reduce breeding sites in water storage systems.
