Plasmodium knowlesi was the most common cause of severe malaria in patients admitted to Queen Elizabeth Hospital in Sabah, Malaysia, according to recent study results. There were no fatalities, which was attributed to the use of artemisinin therapy.
"Clinicians working in P. knowlesi-endemic areas, or attending patients who may have returned from such areas, need to be aware of the high severity rate of this species," study researcher Bridget E. Barber, MD, told Infectious Disease News. "Patients with any features of severe malaria from any species should be commenced on intravenous artesunate without delay."
Bridget E. Barber
Barber, of the Infectious Disease Unit, Queen Elizabeth Hospital, Sabah, and Menzies School of Health Research, Australia, and colleagues prospectively assessed nonpregnant malaria patients aged at least 12 years using polymerase chain reaction testing methods. The researchers compared risk, spectrum and severity of disease related to P. knowlesi, Plasmodium falciparum and Plasmodium vivax.
Results indicated that severe malaria occurred in 38 of 130 (29%) patients with P. knowlesi, 13 of 122 (11%) with P. falciparum, and seven of 43 (16%) with P. vivax. The most common severity criteria for P. knowlesi-related malaria were parasitemia, jaundice, respiratory distress, hypotension and acute kidney injury.
P. knowlesi was associated with a 2.96-fold higher risk (95% CI, 1.19-7.38) for severe malaria vs. P. falciparum (P=.02). Parasitemia and schizontemia >10% independently predicted the severity of P. knowlesi malaria. The risk for severe P. knowlesi malaria increased 11-fold with parasitemia >20,000/mcL and 28-fold with parasitemia >100,000/mcL.
Nearly all of the patients (92%) with P. knowlesi malaria received oral artemisinin therapy, with one or more doses of IV artesunate also given to 95% and 42% of patients with severe and non-severe knowlesi malaria, respectively. There were no deaths as a result of any Plasmodium species, according to Barber and colleagues.
“The low case-fatality rate from severe P. knowlesi malaria in this series contrasts with the high case-fatality rate previously reported with the use of nonartemisinin therapies,” the researchers wrote. “Early referral protocols and standardized (including prereferral) use of intravenous artesunate and oral [artemisinin combination therapies] likely contributed to the low case-fatality rate from P. knowlesi and indeed all Plasmodium species in this series, and warrant wider implementation.”
Disclosure: Barber reports no relevant financial disclosures.
Bridget E. Barber, MD, can be reached at firstname.lastname@example.org.