Why millions in cities are at risk of malaria

A flooded section of Mukuru kwa Reuben slims in Nairobi. Such stagnant water is good breeding ground for mosquitoes.

Photo credit: File | Nation Media Group

What you need to know:

  • Malaria will soon be knocking on the doors of city dwellers following the invasion of a new species of mosquito from Asia.
  • The species was first discovered in 2012 following an unusual outbreak of malaria in Djibouti City.
  • Investigations revealed that the species thrives in urban environments and has since been identified in Ethiopia and Sudan.

The malaria-carrying mosquito has finally found a way of surviving in the harsh urban environment.

Long considered a rural disease, malaria will soon be knocking on the doors of city dwellers following the invasion of a new species of mosquito from Asia. 

The Anopheles stephensi is a malaria-carrying mosquito that thrives in cities, giving it the potential to spread to dozens of cities across the continent and could put more than 126 million people at risk of the disease, a new study shows.

The species was first discovered in 2012 following an unusual outbreak of malaria in Djibouti City.

According to the study published in the scientific journal Proceedings of the National Academy of Sciences, investigations revealed that the species thrives in urban environments and has since been identified in Ethiopia and Sudan.

“By combining data for Anopheles stephensi across its full range (Asia, Arabian Peninsula, Horn of Africa) with spatial models that identify the species’ preferred habitat, our results suggest over 126 million people in cities across Africa could be at risk,” the researchers said.

Annual deaths

Malaria is caused by a parasite called plasmodium, which is transmitted to humans through bites of infected female Anopheles mosquitoes. It kills more than 400,000 people a year, mostly pregnant women and children.

It’s largely a rural disease, where the species known as Anopheles gambiae thrives. However, ongoing urbanisation has meant that many cities have developed areas for urban agriculture. This, combined with poor water management, unplanned urban sprawl and an emerging adaptation to dirtier water, means there are increasingly more environments for mosquitoes to breed. This has led to a rise in malaria transmission in many African cities.

A new study led by Marianne Sinka, a senior postdoctoral researcher at the University of Oxford, says the new species may already be adapting to its new environment and becoming active year-round. “If it continues its incursion into the African continent unchecked, there is a real possibility of mass outbreaks of malaria. In a continent striving to improve and strengthen its health systems, such a huge burden could be catastrophic. Targeted vector surveillance is, therefore, urgently needed,” Sinka’s team said.

Out of 68 cities with a population of more than one million, 44 were found to be suitable habitats for Anopheles stephensi, the team reported two weeks ago. The cities are home to 126 million people.

Vector alert

The situation prompted the World Health Organisation to issue a vector alert mid last year, saying, countries in and around the Horn of Africa must take immediate action to monitor the presence of the mosquito and prevent it from breeding.

The continent currently records 94 per cent of global malaria deaths. In 2018, there were an estimated 228 million cases of malaria worldwide.