Performance of passive case detection for malaria surveillance: results from nine countries in Mesoamerica and the Dominican Republic

Background

In malaria elimination settings, available metrics for malaria surveillance have been insufficient to measure the performance of passive case detection adequately. An indicator for malaria suspected cases with malaria test (MSCT) is proposed to measure the rate of testing on persons presenting to health facilities who satisfy the definition of a suspected malaria case. This metric does not rely on prior knowledge of fever prevalence, seasonality, or external denominators, and can be used to compare detection rates in suspected cases within and between countries, including across settings with different levels of transmission.

Methods

To compute the MSCT, an operational definition for suspected malaria cases was established, including clinical and epidemiological criteria. In general, suspected cases included: (1) persons with fever detected in areas with active malaria transmission; (2) persons with fever identified in areas with no active transmission and travel history to, or residence in areas with active transmission (either national or international); and (3) persons presenting with fever, chills and sweating from any area. Data was collected from 9 countries: Belize, Colombia (in areas with active transmission), Costa Rica, Dominican Republic, El Salvador, Guatemala, Honduras, Nicaragua, and Panama (September–March 2020). A sample of eligible medical records for 2018 was selected from a sample of health facilities in each country. An algorithm was constructed to assess if a malaria test was ordered or performed for cases that met the suspected case definition.

Results

A sample of 5873 suspected malaria cases was obtained from 239 health facilities. Except for Nicaragua and Colombia, malaria tests were requested in less than 10% of all cases. More cases were tested in areas with active transmission than areas without cases. Travel history was not systematically recorded in any country.

Conclusions

A statistically comparable, replicable, and standardized metric was proposed to measure suspected malaria cases with a test (microscopy or rapid diagnostic test) that enables assessing the performance of passive case detection. Cross-country findings have important implications for malaria and infectious disease surveillance, which should be promptly addressed as countries progress towards malaria elimination. Local and easy-to-implement tools could be implemented to assess and improve passive case detection.

Effect of routine seasonal malaria chemoprevention on malaria trends in children under 5 years in Dangassa, Mali

BACKGROUND

Seasonal malaria chemoprevention (SMC) is a new strategy to prevent malaria in children under 5 years old. It has been recommended by the World Health Organization since 2012 in malaria-endemic areas with seasonal transmission. This study aimed to assess the changes in malaria indicators through two consecutive years of SMC routine implementation in children under 5 years old in Dangassa, where malaria is endemic with a long and high transmission season.

METHODS

From 2012 to 2016, a cohort study was conducted in Dangassa village. The study team based in the village followed all malaria clinical cases in children under 5 years old at the community health centre. During the study, SMC was routinely implemented in collaboration with the National Malaria Control Programme. The Cox regression model was used in order to compare malaria risk during the study.

RESULTS

The Cox regression model showed a significant reduction in malaria clinical incidence, both in 2015 (HR = 0.27 (0.18-0.40), 95% CI) and in 2016 (HR = 0.23 (0.15-0.35), 95% CI) of SMC implementation compared to October 2013. Gametocyte and fever prevalence was lower between September and October during SMC implementation (2015 and 2016) compared to the same period before SMC implementation (2013-2014). A slight increase of malaria incidence was observed in December at the end of SMC implementation.

CONCLUSION

SMC has significantly reduced both malaria incidence and gametocyte prevalence and improved haemoglobin levels in children under 5 years old after 2 years of routine implementation.