SA scientists monitor spread of invasive mosquito
SA scientists are closely monitoring the rapid expansion of the Anopheles stephensi mosquito in Africa as the invasive species has the potential to increase malaria transmission in areas free of the disease at present, a senior scientist at the National Institute of Communicable Diseases (NICD) said on Tuesday.
An. stephensi was originally confined to South Asia and the Arabian Peninsula but is now widespread in the Horn of Africa and has been detected in Kenya.
The spread of An. stephensi is worrying scientists as it is more difficult to control than other species and thrives in urban areas. Should it take hold in the Sadc region it could reverse member nations’ hard-won gains in reducing malaria transmission.
“We are particularly concerned about this vector because it can breed in both rural and urban areas quite happily,” said the head of the NICD’s laboratory for antimalarial resistance monitoring and malaria operational research, Jaishree Raman. “Most SA malaria transmission is in rural areas: if this mosquito comes into SA there is the possibility of increasing the areas where it can be transmitted,”
“It can breed just about anywhere, in very little water and is not fussy about water quality. It seems to be resistant to a range of insecticides, and it can spread both plasmodium falciparum and plasmodium vivax malaria,” she said.
The malaria-transmitting mosquito species now found in SA, of which there are several species, spread only P. falciparum.
While SA has yet to reach its goal of eliminating malaria, which is endemic to parts of Limpopo, Mpumalanga and KwaZulu-Natal, the number of indigenous cases has been on a downward trajectory since 2017, according to the World Malaria Report 2023.
It shows that the number of indigenous malaria cases reported in SA fell from 23,381 in 2017 to 2,972 in 2021, and then fell a further 31% to 2,043 in 2022. The latest data from the NICD, which includes both indigenous and imported cases, shows 5,813 malaria cases were reported in the 2022-2023 malaria season.
In a report published on Tuesday, the NICD said it was concerned that almost 1,200 people were diagnosed with severe malaria during the latest malaria season, suggesting they were not diagnosed timeously.
It also drew attention to suboptimal treatment for severe malaria in some healthcare facilities, particularly in the private sector, which gave patients intravenous quinine instead of the safer and more effective intravenous artesunate.
“Intravenous artesunate provides roughly 23%-35% better treatment outcomes,” said the NICD.