Epidemiological profile of imported malaria cases in the prevention of reestablishment phase in Sri Lanka

msp1, msp2, and glurp genotyping to differentiate Plasmodium falciparum recrudescence from reinfections during prevention of reestablishment phase, Sri Lanka, 2014-2019

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

The association between climatic factors and waterborne infectious outbreaks with a focus on vulnerability in Pakistan: integrative review

Climate change affects the spread of waterborne infectious diseases, yet research on vulnerability to outbreaks remains limited. This integrative review examines how climate variables (temperature and precipitation) relate to human vulnerability factors in Pakistan. By 2060, mean temperatures are projected to rise from 21.68°C (2021) to 30°C, with relatively stable precipitation. The epidemiological investigation in Pakistan identified Diarrhea (119,000 cases/year), Malaria (2.6 million cases/year), and Hepatitis (A and E) as the most prevalent infections. This research highlighted vulnerability factors, including poverty (52% of the population), illiteracy (59% of the population), limited healthcare accessibility (55% of the population), malnutrition (38% of the population), dietary challenges (48% of the population), as well as exposure to water pollution (80% of the population) and air pollution (55% of the population). The findings suggest that the coordinated strategies are vital across health, environmental, meteorological, and social sectors, considering climatic variability patterns and population vulnerability determinants.

Plasmodium ovale infection in Sri Lanka: distant exposure and incidental detection of hyperparasitemia: a case report

BACKGROUND

Plasmodium ovale malaria, which was previously endemic to tropical Africa and the Southwest Pacific islands is now being reported from parts of Asia. In Sri Lanka, the indigenous transmission of malaria has not been documented since October 2012. Since then, there have been several imported cases of malaria, including P. ovale, which have been detected sporadically. The reporting case of P. ovale was imported and detected incidentally in 2021, with several atypical presentations.

CASE PRESENTATION

A 40-year-old Sri Lankan medical doctor developed continuous fever with chills, rigors, and dysuria a day following removal of a large lipoma at the root of the neck under general anaesthesia. When the fever has been responding to antibiotics, on the 4th postoperative day a mild thrombocytopenia on complete blood count was detected. A blood smear which was done on the 5th postoperative day incidentally found a malaria parasite and confirmed as Plasmodium ovale with a density of 6535 parasites/microliter on the same day. He never had malaria in the past, but he had worked in South Sudan 1 year ago and visited India six months ago. On the 6th postoperative day, he was treated with chloroquine, and hyperparasitemia reduced rapidly by the next day. As the fever recurred with clinical deterioration, he was treated with different antibiotics. During the course of the illness, he did not develop pallor, or icterus except for a palpable soft spleen. The parasite count was zero on the 9th postoperative day and his fever subsided on the next day. Further, he was treated with primaquine to prevent future relapse and transmission.

CONCLUSION

A long incubation period, incidental detection of P ovale in a blood smear, and hyperparasitaemia are the atypical presentations of this case. Postoperative bacterial infection and stress may have reactivated the dormant malaria (hyponozoites) in this patient with an unusual picture. Coinfection of malaria with bacterial sepsis is a challenge in the management of the patient. As the Anopheles mosquito vector exists in Sri Lanka, the risk of indigenous transmission is high from such imported cases of P. ovale.

A malaria death due to an imported Plasmodium falciparum infection in Sri Lanka during the prevention of re-establishment phase of malaria

BACKGROUND

Sri Lanka has maintained a rigorous programme to prevent the re-establishment of malaria ever since the disease was eliminated in October 2012. It includes efforts to sustain case surveillance to ensure early diagnosis and management of malaria. Yet, in April of 2023 the death occurred of an individual with imported malaria.

CASE PRESENTATION

The deceased was a 37-year-old Sri Lankan male who returned to Sri Lanka on the 10th of April after a business trip to several countries including Tanzania. He was febrile on arrival and consulted three Allopathic Medical Practitioners in succession in his home town in the Western Province of Sri Lanka, over a period of 5 days starting from the very day that he arrived in the country. Malaria was not tested for at any of these consultations and his clinical condition deteriorated. On the evening of 14th of April he was admitted to the medical intensive care unit of a major private hospital in the capital city of Colombo with multiple organ failure. There, on a request by the treating physician blood was tested for malaria and reported early the next morning as Plasmodium falciparum malaria with a high parasitaemia (> 10%). The patient died shortly after on the 15th of April before any anti-malarial medication was administered. The deceased had been a frequent business traveller to Africa, but with no past history of malaria. He had not taken chemoprophylaxis for malaria on this or previous travels to Africa.

DISCUSSION

The patient's P. falciparum infection progressed rapidly over 5 days of arriving in Sri Lanka leading to severe malaria without being diagnosed, despite him seeking healthcare from three different Medical Practitioners. Finally, a diagnosis of malaria was made on admission to an intensive care unit; the patient died before anti-malarial medicines were administered.

CONCLUSIONS

This first death due to severe P. falciparum malaria reported in Sri Lanka after elimination of the disease was due to the delay in diagnosing malaria.

Reactive Case Detection Strategy for Malaria Control and Elimination: A 12 Year Systematic Review and Meta-Analysis from 25 Malaria-Endemic Countries

Reactive case detection (RACD) is the screening of household members and neighbors of index cases reported in passive surveillance. This strategy seeks asymptomatic infections and provides treatment to break transmission without testing or treating the entire population. This review discusses and highlights RACD as a recommended strategy for the detection and elimination of asymptomatic malaria as it pertains in different countries. Relevant studies published between January 2010 and September 2022 were identified mainly through PubMed and Google Scholar. Search terms included "malaria and reactive case detection", "contact tracing", "focal screening", "case investigation", "focal screen and treat". MedCalc Software was used for data analysis, and the findings from the pooled studies were analyzed using a fixed-effect model. Summary outcomes were then presented using forest plots and tables. Fifty-four (54) studies were systematically reviewed. Of these studies, 7 met the eligibility criteria based on risk of malaria infection in individuals living with an index case < 5 years old, 13 met the eligibility criteria based on risk of malaria infection in an index case household member compared with a neighbor of an index case, and 29 met the eligibility criteria based on risk of malaria infection in individuals living with index cases, and were included in the meta-analysis. Individuals living in index case households with an average risk of 2.576 (2.540-2.612) were more at risk of malaria infection and showed pooled results of high variation heterogeneity chi-square = 235.600, (p < 0.0001) I² = 98.88 [97.87-99.89]. The pooled results showed that neighbors of index cases were 0.352 [0.301-0.412] times more likely to have a malaria infection relative to index case household members, and this result was statistically significant (p < 0.001). The identification and treatment of infectious reservoirs is critical to successful malaria elimination. Evidence to support the clustering of infections in neighborhoods, which necessitates the inclusion of neighboring households as part of the RACD strategy, was presented in this review.

Factors related to human-vector contact that modify the likelihood of malaria transmission during a contained Plasmodium falciparum outbreak in Praia, Cabo Verde

Background

Determining the reproductive rate and how it varies over time and space (RT) provides important insight to understand transmission of a given disease and inform optimal strategies for controlling or eliminating it. Estimating RT for malaria is difficult partly due to the widespread use of interventions and immunity to disease masking incident infections. A malaria outbreak in Praia, Cabo Verde in 2017 provided a unique opportunity to estimate RT directly, providing a proxy for the intensity of vector-human contact and measure the impact of vector control measures.

Methods

Out of 442 confirmed malaria cases reported in 2017 in Praia, 321 (73%) were geolocated and informed this analysis. RT was calculated using the joint likelihood of transmission between two cases, based on the time (serial interval) and physical distance (spatial interval) between them. Log-linear regression was used to estimate factors associated with changes in RT, including the impact of vector control interventions. A geostatistical model was developed to highlight areas receptive to transmission where vector control activities could be focused in future to prevent or interrupt transmission.

Results

The RT from individual cases ranged between 0 and 11 with a median serial- and spatial-interval of 34 days [interquartile range (IQR): 17-52] and 1,347 m (IQR: 832-1,985 m), respectively. The number of households receiving indoor residual spraying (IRS) 4 weeks prior was associated with a reduction in RT by 0.84 [95% confidence interval (CI) 0.80-0.89; p-value <0.001] in the peak-and post-epidemic compared to the pre-epidemic period.

Conclusions

Identifying the effect of reduced human-vector contact through IRS is essential to determining optimal intervention strategies that modify the likelihood of malaria transmission and can inform optimal intervention strategies to accelerate time to elimination. The distance within which two cases are plausibly linked is important for the potential scale of any reactive interventions as well as classifying infections as imported or introduced and confirming malaria elimination.

Spatial analysis to evaluate risk of malaria in Northern Sumatera, Indonesia

Background

As Indonesia aims for malaria elimination by 2030, provisional malaria epidemiology and risk factors evaluation are important in pursue of this national goal. Therefore, this study aimed to understand the risk factor of malaria in Northern Sumatera.

Methods

Malaria cases from 2019 to 2020 were obtained from the Indonesian Ministry of Health Electronic Database. Climatic variables were provided by the Center for Meteorology and Geophysics Medan branch office. Multivariable logistic regression was undertaken to understand the risk factors of imported malaria. A zero-inflated Poisson multivariable regression model was used to study the climatic drivers of indigenous malaria.

Results

A total of 2208 (indigenous: 76.0% [1679] and imported: 17.8% [392]) were reported during the study period. Risk factors of imported malaria were: ages 19–30 (adjusted odds ratio [AOR] = 3.31; 95% confidence interval [CI] 1.67, 2.56), 31–45 (AOR = 5.69; 95% CI 2.65, 12.20), and > 45 years (AOR = 5.11; 95% CI 2.41, 10.84). Military personnel and forest workers and miners were 1,154 times (AOR = 197.03; 95% CI 145.93, 9,131.56) and 44 times (AOR = 44.16; 95% CI 4.08, 477,93) more likely to be imported cases as compared to those working as employees and traders. Indigenous Plasmodium falciparum increased by 12.1% (95% CrI 5.1%, 20.1%) for 1% increase in relative humidity and by 21.0% (95% CrI 9.0%, 36.2%) for 1 °C increase in maximum temperature. Plasmodium vivax decreased by 0.8% (95% CrI 0.2%, 1.3%) and 16.7% (95% CrI 13.7%, 19.9%) for one meter and 1 °C increase of altitude and minimum temperature. Indigenous hotspot was reported by Kota Tanjung Balai city and Asahan regency, respectively. Imported malaria hotspots were reported in Batu Bara, Kota Tebing Tinggi, Serdang Bedagai and Simalungun.

Conclusion

Both indigenous and imported malaria is limited to a few regencies and cities in Northern Sumatera. The control measures should focus on these risk factors to achieve elimination in Indonesia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04262-y.