The World Health Organization (WHO) has launched a new initiative to counter the added malaria threat posed by the rapid expansion on the African continent of the mosquito Anopheles stephensi — native to parts of South Asia and the Arabian Peninsula, the organization said this week. 

The initiative comes just as the world struggles to get malaria control back on track – something that the invasive An. stephensi mosquito, which belongs to the same subgenus as  Anopheles gambiae, the primary malaria vector in Africa, expands its range.

“We are still learning about the presence of Anopheles stephensi and its role in malaria transmission in Africa,” said Dr Jan Kolaczinski, who leads the Vector Control and Insecticide Resistance unit within WHO’s Global Malaria Programme. “It is important to underscore that we still don’t know how far the mosquito species has already spread, and how much of a problem it is or could be.”

But with detections of the new vector already reported in several African countries including Djibouti, Ethiopia, Sudan, Somalia and Nigeria, WHO is sounding the alarm bell to Africa’s national malaria programmes. This is particularly the case because of the vector’s ability to thrive in urban settings – unlike An. gambiae.

Moreover, the vector has been found to be resistant to many of the insecticides used today for malaria control – thus posing an added challenge. One study projected that An. stephensi could put an additional 126 million people in Africa at risk of malaria if the mosquito vector were to spread unchecked. Another study estimated that the number of malaria cases in Ethiopia could increase by 50% if An. stephensi were to spread to all receptive areas.

Vector’s ability to spread in cities a big concern

Of particular concern is the vector’s ability to spread in cities; as Africa undergoes rapid urbanization with 40% of people now living in cities. The WHO noted that An. stephensi is thought to have contributed to a resurgence of malaria in Djibouti City and at least one outbreak of the disease in Ethiopia —both in  2012. So while the overall contribution of An. stephensi to malaria transmission in the region today remains unclear, there is considerable potential for this highly efficient and adaptable malaria vector to undermine the gains made in reducing the burden of the disease, experts say.

For Africa then, the new WHO initiative, described in detail in a new policy brief, could be decisive in the battle to halt further spread of An. stephensi in the region, as well as determining whether it can be eliminated from areas that have already been invaded. 

Specifically, the initiative aims to: strengthen surveillance to determine the extent of the spread of An. stephensi and its role in malaria transmission; and increase collaboration across sectors and borders so as to improve information exchange on the presence of An. stephensi and the success of efforts to control it.

The initiative also will develop guidance for national malaria control programmes on appropriate ways to respond to An. stephensi, and prioritize research to evaluate the impact of interventions and tools against the mosquito vector.

Getting malaria control back on track

In 2020, malaria deaths rose by 12% as compared to the year before, as a result of pandemic-related service interruptions. Following a longstanding pattern, the vast majority of all malaria cases (95%) and malaria deaths (96%) were located in the African Region, with an estimated 80% of all malaria deaths in the region among children under the age of 5.

In June 2022, Philip Welkhoff, Director of the Malaria Program at the Bill & Melinda Gates Foundation, told Health Policy Watch that the world has lost years of progress on malaria control thanks to the COVID pandemic, with malaria mortality close to what it was almost a decade ago.

“Malaria is really unforgiving. And when there are disruptions in either access to care or some of the routine services, that malaria burden will go up. Because of COVID, we’ve gone backwards,” Welkhoff said, in an interview.

The latest, 2021 data now shows signs of recovery in malaria control programmes, according to the latest report of the Global Fund, with increased rates of testing and diagnosis in particular.

Now more than ever, however, “integrated action” that combines all available tools for vector surveillance, control, diagnosis and treatment, will be important in tackling the additional threats posed by An. stephensi to malaria control goals, said Dr Ebenezer Baba, malaria advisor for the WHO African Region.

“Integrated action will be key to success against Anopheles stephensi and other vector-borne diseases. Shifting our focus to integrated and locally adapted vector control can save both money and lives,” he said.

See the related story here:

https://healthpolicy-watch.news/tb-hiv-malaria-rebounds-pre-pandemic-level/

Image Credits: Munira Ismail_MSH, WHO .