Rapid diagnostic test becoming less effective in detecting malaria parasite.Credit: Jimlop collection/Alamy Stock Photo
A new study has found that rapid diagnostic tests (RDTs), which are easier to deploy at low cost and require minimal expertise, may be missing 20% of malaria cases in some regions in Africa. The continent accounts for more than 94% of malaria cases and deaths globally, according to the World Health Organisation.
Published in Nature Microbiology, Sindew Feleke, from the Ethiopian Public Health Institute and colleagues studied blood samples of nearly 13,000 participants in Ethiopia, along its borders with Eritrea, Sudan and South Sudan. As well as using RDTs — whose accuracy is susceptible to the deletion of histidine-rich protein 2 (pfhrp2) and 3 (pfhrp3) genes, the mechanism through which malaria parasites are able to evade detection — the researchers applied other more sensitive and specific methods.
The result showed more than 13% of total P. falciparum-positive study participants had an RDT profile suggestive of pfhrp2/3-deleted P. falciparum infection. They reported that the northern region of Tigray had the highest proportion of infections with incorrect RDT profiles at 20.4% of positive cases, followed by Amhara with 15.8%, and Gambella 1.5%. The study concluded that pfhrp2/3-deleted parasites are circulating in multiple sites along Ethiopia’s borders with Sudan and Eritrea.
“Existing malaria control programmes are threatened by expansion of these parasite strains, and prevalence estimates in Tigray and Amhara exceed WHO-recommended thresholds for RDT change. Urgent attention to these deletion mutations is needed to inform malaria diagnostic testing policies throughout the Horn of Africa,” the researchers concluded.
Olabanji Surakat, a parasitologist and malaria research expert at Osun State University in Nigeria, told Nature Africa the findings further reinforced microscopy as the gold standard for malaria testing. RDTs are only a stop gap for low-resource settings,to reduce the over-use of antimalarial combination therapy medicines.
