High incidence of asymptomatic cases during an outbreak of Plasmodium malariae in a remote village of Malaysian Borneo

Abstract

An outbreak of Plasmodium malariae occurred in Sonsogon Paliu village in the remote area of Ulu Bengkoka sub-district of Kota Marudu, Northern Sabah, Malaysian Borneo from July through August 2019. This was the first outbreak of malaria in this village since 2014. On 11th July 2019 the Kota Kinabalu Public Health Laboratory notified the Kota Marudu District Health Office of a Polymerase Chain Reaction (PCR) positive case of P. malariae. This index case was a male from Sulawesi, Indonesia working for a logging company operating in Sonsogon Paliu. During the resulting outbreak, a total of 14 symptomatic cases were detected. All of these cases were positive by thick and thin blood smear examination, and also by PCR. During the outbreak, a mass blood survey screening was performed by light-microscopy and PCR. A total of 94 asymptomatic villagers 31 (33.0%) were PCR positive but thick and thin blood smear negative for P. malariae. Both symptomatic and asymptomatic cases received treatment at the district hospital. When symptomatic and asymptomatic cases were considered together, males (29/45. 64.5%) were infected more than females (16/45, 35.6%), the male:female ratio being 1.8:1. Adults were the predominant age group infected (22/45, 48.9%) followed by adolescents (19/45, 42.2%) and children under five years of age (4/45, 8.9%). This report illustrates that symptomatic and submicroscopic cases pose a challenge during P. malariae outbreaks and that PCR is a valuable tool for their identification. The rapid identification and control of imported malaria is crucial for the continued control of malaria in Malaysia.

Profiling the imported human malaria in Sarawak, Malaysia in 2011–2019

“…Malaria outbreaks caused by imported cases have been observed locally and in several countries. In 2019, an outbreak of P. malariae infections was reported in a rural village in Sabah, linked to a logging worker from Indonesia [65]. In Russia, more than 500 autochthonous vivax malaria cases were recorded in Moscow between 1999 and 2008, after large‐scale imported cases were detected [66].…”

International modified Delphi study on malaria preventive behaviour: new themes, contexts and framework for future research onPlasmodium knowlesimalaria

“…The complexity of zoonotic P. knowlesi malaria necessitates a paradigm shift in understanding disease transmission and burden prevention in the future. Even though artesunate is the first-line treatment for P. knowlesi malaria, many people reside in areas where tertiary care is inaccessible 22. While most cases were uncomplicated, fatalities have been reported in Sabah, Malaysia 23.…”

“…While most cases were uncomplicated, fatalities have been reported in Sabah, Malaysia 23. Furthermore, in areas with a limited diagnostic capacity, the similar P. knowlesi and P. malariae morphologies often result in a misdiagnosis22; and the similar morphology of early P. knowlesi and P. falciparum trophozoites also requires careful identification to avoid misdiagnosis 24. Because the rapid reproduction ability of P. knowlesi exacerbates the threat to at-risk communities,23 the P. knowlesi expert review group proposed evidence-based investigations of human-to-human transmission, entomology mapping overlaying human incidence and environmental factors, laboratory diagnostic development and clinical management as research priority areas 2…”