Malaria has long been one of the world’s most persistent infectious diseases, particularly in tropical countries like Indonesia. Caused by the Plasmodium parasite and transmitted through the bite of the Anopheles mosquito, malaria has inflicted significant losses, both in human lives and the resources allocated for its control. In Indonesia, although malaria cases have steadily declined in recent years, major challenges remain—especially in areas classified as high-transmission zones. With the national target of malaria elimination set for 2030, the Indonesian government has become increasingly focused on more strategic and data-driven approaches to control the disease. One such emerging tool is serology.

Serology is a technique used to measure the body’s antibody response to malaria infection. Each time a person is exposed to Plasmodium, the immune system produces antibodies in response. This method enables researchers to determine how many individuals have previously been exposed to malaria—even if they show no symptoms. This approach is especially valuable in low-transmission settings, where many infections go unnoticed or unreported due to the absence of clinical symptoms.

Langkat, located in North Sumatra Province, is one of the regions of interest in malaria control efforts. While the number of malaria cases in Langkat has significantly declined, the region still faces several challenges in achieving elimination. One key concern is understanding the transmission patterns of Plasmodium falciparum and Plasmodium vivax, the two primary malaria-causing species in Indonesia. A serological study was conducted in 2019 in Langkat to explore the impact of both species on the local population. The research was carried out by Inke Nadia Diniyanti Lubis, Irbah Rea Alvieda Nainggolan, Meliani Meliani, Beby Syofiani Hasibuan, and Ranti Permatasari from Universitas Sumatera Utara Indonesia; Kumuthamalar Sangaran and Zulkarnain Md Idris from Universiti Kebangsaan Malaysia; Luqman Samsudin from District Health Office Malaysia; Sriwipa Chuangchaiya from Kasetsart University Thailand; and Paul Cliff Simon Divis from Universiti Malaysia Sarawak Malaysia.

The study involved 339 participants whose antibody responses to four specific antigens from P. falciparum and P. vivax were tested. The antigens used for P. falciparum were PfAMA-1 and PfMSP-119, while PvAMA-1 and PvMSP-119 were used for P. vivax. Enzyme-linked immunosorbent assay (ELISA) was employed to measure antibody levels in the blood, indicating prior exposure to malaria parasites. The findings revealed a relatively high seroprevalence of malaria in Langkat, despite its current status as a low-transmission area. Seroprevalence rates were 10.6% for PfAMA-1, 13% for PfMSP-119, 18.6% for PvAMA-1, and 7.4% for PvMSP-119. Although these figures are not extremely high, they suggest ongoing malaria transmission in the region, albeit at a lower level.

A more compelling outcome of this research was the insight into the intensity of transmission between the two parasite species. Seroconversion analysis indicated that the transmission rate of P. falciparum was slightly higher than that of P. vivax, although the difference was not statistically significant. This finding underscores that while P. falciparum is often viewed as more dangerous due to its association with severe malaria and fatalities, P. vivax also has significant transmission potential and should receive equal attention in malaria control strategies.

The study also identified risk factors associated with malaria transmission in Langkat. One prominent factor was residing in or working within forested areas. Forests are known habitats for Anopheles mosquitoes, increasing the risk for those frequently in such environments to contract P. vivax malaria. “Those who spent nights in the forest were significantly more likely to be seropositive for P. vivax, with an odds ratio of 3.93,” explained Inke Nadia. This suggests that individuals who live or work in forested areas are at greater risk of exposure. Interestingly, for P. falciparum, no significant risk factor was identified, indicating that its transmission may be more evenly distributed and not confined to specific behaviors or environments like forest exposure.

Inke Nadia emphasized that this study offers valuable insights for malaria control efforts in Langkat and beyond. Although P. falciparum and P. vivax differ in terms of infection severity and transmission dynamics, the serological results indicate that both species warrant equal focus in elimination strategies. Given their similar transmission patterns in Langkat, a more holistic approach to malaria control is essential—one that doesn’t exclusively target P. falciparum.

The identification of risk factors is also crucial for designing more precise prevention strategies. For instance, for individuals frequently working or staying in forests, it is vital to introduce preventive measures such as the use of bed nets, protective clothing, or insect repellent. These actions can reduce the risk of exposure, particularly to P. vivax. Furthermore, public education about malaria prevention—especially in high-risk areas—should be continuously strengthened. With the right information, communities can become more aware and take necessary steps to protect themselves from malaria.

“One of the major advantages of the serological approach is its ability to provide a more comprehensive picture of malaria transmission in a given area, even when active cases are declining,” said Inke Nadia. Serology enables detection of asymptomatic or undiagnosed malaria exposure, which is highly beneficial for monitoring the effectiveness of on-ground control strategies. With a deeper understanding of transmission patterns and existing risk factors, governments can design more targeted policies to reduce malaria cases and work toward elimination by 2030.

Although Langkat has made significant progress in reducing malaria cases, this study reminds us that the path to elimination remains long. Serological research provides a valuable tool to continuously monitor transmission and ensure that high-risk areas are not overlooked. This is where data-driven approaches play a crucial role, enabling researchers and authorities to track malaria trends and adjust policies accordingly.

On a broader scale, this study also contributes meaningfully to Indonesia’s national malaria elimination efforts. By using serology as a monitoring tool, the country can more rapidly identify areas with persistent transmission and adapt its interventions. This allows for more efficient resource allocation and accelerates progress toward the 2030 malaria elimination goal.