‘Act on new threat to malaria diagnosis’

THE Malaria Policy Advisory Group (MPAG) has called for urgent action in response to a new threat to diagnoses in endemic countries, most notably in the Horn of Africa.

The group reviewed available information during its meeting last month and called for action in addressing the increased prevalence of pfhrp2 gene deletions.

Malaria rapid diagnostic tests (RDTs) have transformed malaria control by diagnosing P falciparum (Pf) infection by targeting one of its antigens, histidine-rich protein 2 (HRP2).

This current cornerstone of P falciparum diagnosis is under serious threat as a result of the emergence of parasites not expressing the HRP2 protein due to mutations in the genes that encode it, the group warned. Over the past six years, an increasing number of African and Asian countries where diagnosis is heavily reliant on HRP2-based RDTs have reported histidine-rich protein 2 and 3 gene (pfhrp2/3) deletions, raising the threat to a new level.

The World Health Organization (WHO) recommends that a more than 5% local prevalence of pfhrp2/3 deletions causing false-negative HRP2 RDTs warrants an immediate change in testing strategy and preparation for nationwide change.

“The Horn of Africa appears to be disproportionately affected, with high prevalence of pfhrp2/3 deletions reported in areas of Ethiopia, Eritrea, Djibouti and to a lesser extent in Sudan and South Sudan; the root cause of many false negative RDT results is under investigation in Somalia. Recent surveys in the Horn of Africa region found that many (> 50%) of P falciparum cases are missed by HRP2 RDTs. Failure to detect and treat infection can result in increased disease, including severe disease and death,” the MPAG said.

“Alternate diagnostic choices are limited, but some non-HRP2 based rapid tests options approved through the Global Fund Expert Review Panel for Diagnostics are available.

“It is imperative that all countries start and maintain surveillance and respond when the prevalence of pfhrp2/3 gene deletions exceeds the WHO criteria for RDT replacement by changing to quality-assured non-HRP2 RDTs to prevent unnecessary morbidity and deaths,” MPAG said.