Abstract
Background
Sri Lanka, an island nation, has eliminated endemic malaria transmission. Maintaining elimination in the continued presence of vectors requires vigilance in screening people ...travelling from high malaria-risk areas and a rapid response with focal screening for infections identified in the community. Such screening requires accurate and very rapid assays that enable an immediate response. Both microscopy and rapid diagnostic tests (RDTs) have limitations including sensitivity and speed in screening large numbers, while polymerase chain reaction (PCR) is practical only as laboratory confirmation. This study assessed the utility of ‘Gazelle’, a novel rapid malaria assay based on magneto-optical detection of haemozoin, a by-product of malaria parasite metabolism.
Methods
Between October 2020 and March 2021, two groups of individuals were screened for malaria by four methods, namely, microscopy, Rapid Diagnostic Test (RDT), Gazelle and PCR. Passive case detection was carried out for confirmation of diagnosis amongst individuals suspected of having malaria. Individuals at high-risk of acquiring malaria, namely persons returning from malaria endemic countries, were screened by active case detection.
Results
Of the 440 individuals screened for malaria, nine malaria positives were diagnosed by PCR, microscopy and the HRP2 band of RDT, which included five
Plasmodium falciparum
infections, two
Plasmodium ovale
, and one each of
Plasmodium vivax
and
Plasmodium malariae.
Gazelle correctly detected the
P. vivax, P. ovale
and
P. malariae
infections within the 2 min test time, but did not detect two
P. falciparum
infections giving a sensitivity of 77.8%. Specificity was 100%.
Discussion
The Gazelle, a portable bench top device proved useful to screen a large number of blood samples for non-falciparum parasites within 5 minutes of sample input. Species differentiation, and improvement in
P. falciparum
detection, will be important to broaden utility.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Sri Lanka has reached zero indigenous malaria cases in November 2012, two years before its targeted deadline for elimination. Currently, the biggest threat to the elimination efforts are the risk of ...resurgence of malaria due to imported cases. This paper describes two clusters of imported malaria infections reported in 2013 and 2014, one among a group of Pakistani asylum-seekers resident in Sri Lanka, and the other amongst local fishermen who returned from Sierra Leone. The two clusters studied reveal the potential impact of imported malaria on the risk of reintroducing the disease, as importation is the only source of malaria in the country at present. In the event of a case occurring, detection is a major challenge both amongst individuals returning from malaria endemic countries and the local population, as malaria is fast becoming a "forgotten" disease amongst health care providers. In spite of a very good coverage of diagnostic services (microscopy and rapid diagnostic tests) throughout the country, malaria is being repeatedly overlooked by health care providers even when individuals present with fever and a recent history of travel to a malaria endemic country. Given the high receptivity to malaria in previously endemic areas of the country due to the prevalence of the vector mosquito, such cases pose a significant threat for the reintroduction of malaria to Sri Lanka. The challenges faced by the Anti Malaria Campaign and measures taken to prevent the resurgence of malaria are discussed here.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Sri Lanka sustained its malaria-free status by implementing, among other interventions, three core case detection strategies namely Passive Case Detection (PCD), Reactive Case Detection (RACD) and ...Proactive Case Detection (PACD). The outcomes of these strategies were analysed in terms of their effectiveness in detecting malaria infections for the period from 2017 to 2019.
Comparisons were made between the surveillance methods and between years, based on data obtained from the national malaria database and individual case reports of malaria patients. The number of blood smears examined microscopically was used as the measure of the volume of tests conducted. The yield from each case detection method was calculated as the proportion of blood smears which were positive for malaria. Within RACD and PACD, the yield of sub categories of travel cohorts and spatial cohorts was ascertained for 2019.
A total of 158 malaria cases were reported in 2017-2019. During this period between 666,325 and 725,149 blood smears were examined annually. PCD detected 95.6 %, with a yield of 16.1 cases per 100,000 blood smears examined. RACD and PACD produced a yield of 11.2 and 0.3, respectively. The yield of screening the sub category of travel cohorts was very high for RACD and PACD being 806.5 and 44.9 malaria cases per 100,000 smears, respectively. Despite over half of the blood smears examined being obtained by screening spatial cohorts within RACD and PACD, the yield of both was zero over all three years.
The PCD arm of case surveillance is the most effective and, therefore, has to continue and be further strengthened as the mainstay of malaria surveillance. Focus on travel cohorts within RACD and PACD should be even greater. Screening of spatial cohorts, on a routine basis and solely because people are resident in previously malarious areas, may be wasteful, except in situations where the risk of local transmission is very high, or is imminent. These findings may apply more broadly to most countries in the post-elimination phase.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Sri Lanka after eliminating malaria in 2012, is in the prevention of re-establishment (POR) phase. Being a tropical country with high malariogenic potential, maintaining vigilance is important. All ...malaria cases are investigated epidemiologically and followed up by integrated drug efficacy surveillance (iDES). Occasionally, that alone is not adequate to differentiate Plasmodium falciparum reinfections from recrudescences. This study evaluated the World Health Organization and Medicines for Malaria Venture (MMV) recommended genotyping protocol for the merozoite surface proteins (msp1, msp2) and the glutamate-rich protein (glurp) to discriminate P. falciparum recrudescence from reinfection in POR phase.
All P. falciparum patients detected from April 2014 to December 2019 were included in this study. Patients were treated and followed up by iDES up to 28 days and were advised to get tested if they develop fever at any time over the following year. Basic socio-demographic information including history of travel was obtained. Details of the malariogenic potential and reactive entomological and parasitological surveillance carried out by the Anti Malaria Campaign to exclude the possibility of local transmission were also collected. The msp1, msp2, and glurp genotyping was performed for initial and any recurrent infections. Classification of recurrent infections as recrudescence or reinfection was done based on epidemiological findings and was compared with the genotyping outcome.
Among 106 P. falciparum patients, six had recurrent infections. All the initial infections were imported, with a history of travel to malaria endemic countries. In all instances, the reactive entomological and parasitological surveillance had no evidence for local transmission. Five recurrences occurred within 28 days of follow-up and were classified as recrudescence. They have not travelled to malaria endemic countries between the initial and recurrent infections. The other had a recurrent infection after 105 days. It was assumed a reinfection, as he had travelled to the same malaria endemic country in between the two malaria attacks. Genotyping confirmed the recrudescence and the reinfection.
The msp1, msp2 and glurp genotyping method accurately differentiated reinfections from recrudescence. Since reinfection without a history of travel to a malaria endemic country would mean local transmission, combining genotyping outcome with epidemiological findings will assist classifying malaria cases without any ambiguity.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This case report discusses recrudescence of imported Plasmodium falciparum malaria, in the presence of P. falciparum Kelch13 (PfK13) propeller mutation, in a patient diagnosed and fully treated with ...artemether-lumefantrine under direct observation in Sri Lanka. This patient presented with a history of 5 days of fever following his arrival from the Democratic Republic of Congo (DRC). He had visited Rwanda 1 week before arrival to Sri Lanka. Treatment was commenced with artemisinin-based combination therapy, artemether-lumefantrine, which is the first-line drug recommended for uncomplicated falciparum malaria. Blood smears were negative for parasites by the third day of treatment. Approximately 2 weeks later, he developed fever again and was diagnosed as having a recrudescence of falciparum malaria. He was treated and responded to the second-line antimalarial dihydroartemisinin-piperaquine. Molecular testing of blood taken from the first infection revealed the presence of amino acid substitutions K189T and R561H within the PfK13 gene. R561H mutation is associated with delayed parasite clearance in Southeast Asia. Although seldom reported from DRC, an emergence and clonal expansion of parasites harboring R561H allele has been reported from Rwanda recently; thus, it is likely that this patient may have got the infection from Rwanda. Sri Lanka eliminated malaria in 2016. However, in the backdrop of continuing imported malaria cases, early diagnosis and prompt treatment is essential to prevent the re-establishment of the disease.
Sri Lanka has achieved 'malaria-free' status and is now in the phase of prevention of re-introduction of malaria. Imported malaria remains a challenge to resurgence of the disease. The diagnostic ...challenges encountered and the rapid response initiated to manage a Plasmodium infection, which was later confirmed as Plasmodium knowlesi, the first reported case from Sri Lanka, is discussed.
An army officer who returned from Malaysia in October 2016 was found to be positive for Plasmodium both by microscopy and rapid diagnostic test (RDT) by the Anti Malaria Campaign Sri Lanka (AMC) during his third visit to a health care provider. Microscopy findings were suspicious of P. knowlesi infection as the smears showed parasite stages similar to both Plasmodium malariae and Plasmodium falciparum. Nested PCR at AMC confirmed Plasmodium genus, but not the species. In the absence of species confirmation, the patient was treated as a case of P. falciparum. The presence of P. knowlesi was later confirmed by a semi-nested PCR assay performed at the Environmental Health Institute, National Environmental Agency in Singapore. The parasite strain was also characterized by sequencing the circumsporozoite gene. Extensive case investigation including parasitological and entomological surveillance was carried out.
Plasmodium knowlesi should be suspected in patients returning from countries in the South Asian region where the parasite is prevalent and when blood smear results are inconclusive.
Full text
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This study determines the use of nested PCR as a diagnostic tool to supplement field microscopy in symptomatic individuals suspected of being positive for malaria, and it explores its role in active ...case detection to identify asymptomatic parasite carriers. In symptomatic individuals, compared with PCR, microscopy had a sensitivity of 86.6% (95% confidence interval CI = 77.8-92.4) and specificity of 100% (95% CI = 96.9-100). During active case detection, two asymptomatic persons were diagnosed as having vivax malaria by polymerase chain reaction (PCR) but not microscopy. Currently, PCR is being carried out in Sri Lanka only for population surveys to estimate the hidden reservoir of malaria. Based on the results of this study and because of cost considerations, pooled PCR will be used in the future to screen samples from clinically suspected foci to increase the proportion of malaria cases detected. This strategy will assist the success of the malaria elimination program in Sri Lanka.
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