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.
Highlights
Malaysia has been identified by the World Health Organization (WHO) as one of 21 countries with the potential to eliminate human malaria by 2020 [1]
Author summary In Malaysia, malaria caused by the human-only malaria parasites has been all but eliminated, and the major obstacles to a malaria-free status are emerging malaria caused by zoonotic transmission of Plasmodium knowlesi parasites and outbreaks caused by imported parasites
One such outbreak occurred in 2019 in a village in northern Sabah. This outbreak was unusual, as it was found to be caused by P. malariae, an often-benign human malaria parasite rarely seen in Malaysia
Summary
Malaysia has been identified by the World Health Organization (WHO) as one of 21 countries with the potential to eliminate human malaria by 2020 [1]. Imported malaria poses a major challenge to Malaysia’s efforts to eliminate the disease. Among all the states of Malaysia, Sabah has the highest number of malaria cases, the majority of which are caused by the zoonotic parasite, Plasmodium knowlesi [1,2,3,4,5]. Cases of malaria caused by human-only malaria parasite species have decreased dramatically, with only 23 cases of Plasmodium falciparum and eight cases of Plasmodium vivax recorded in Sabah 2017 [1], whereas in the same period 3,614 cases of P. knowlesi were reported [6]. Responsible for far fewer cases of clinical malaria than P. falciparum and P. vivax globally, it can cause long-term chronic infections and possesses the ability to recrudesce due to the persistence of subclinical parasitemia [9]. Our findings highlight the challenges posed by imported malaria for the achievement of malaria elimination
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