Scientists have detected new strains of malaria-causing parasites in Ethiopia that are both resistant to current treatments and escape detection by common diagnostic tests—a development that could increase cases and deaths from malaria and make eliminating the persistent disease an even greater challenge.

Already, scientists had found in Uganda, Tanzania, and Rwanda strains of the parasite Plasmodium falciparum that were resistant to most available antimalarial drugs; and separately, parasites resistant to diagnostic tests had emerged in the Horn of Africa.

Those parasites have been spreading independently of one another. The new findings confirm the prevalence of this type of double-resistant malaria strain, says Jeffrey Bailey, MD, PhD, an associate professor of translational research and of pathology and laboratory medicine at Brown.

“Now we’re essentially seeing the worst-case scenario: parasites with the mutation that make them resistant to treatment have also picked up the chromosomal deletions that make them invisible to the diagnostic tests,” Bailey says. “This means that it will be harder to detect people who are infected, and then when infected people are treated with antimalarial drugs, that may not work to stop them from spreading the disease.”