Raising the Bar for Malaria Research: Investigating Monkey malaria under three different lenses

By Leah Melita G. de Ocampo, published in RITM Update Volume 2 Issue 2 (July to September 2015)

Raising the Bar for Malaria Research
In the photo: Entomologists at work. The entomologists of the Monkeybar Project conducting preliminary mosquito trapping using E-net, carabao-baited trap (CBT) and Human Landing Catch (HLC)

It is not every day that we see basic and social scientists, monkeys, drones, and Global Positioning System (GPS) devices in one project.

A research with the nickname ‘Monkeybar’ project made this possible.

Scientists and researchers from the United Kingdom, Malaysia, and the Philippines are working together in this project to investigate the malaria parasite Plasmodium knowlesi, commonly known as “monkey malaria”.

This 5-year research project funded by the United Kingdom- Medical Research Council (UK-MRC) Environment & Social Ecology of Human Infectious Diseases (ESEI) aims to find out how P. knowlesi is transmitted from monkeys to humans via mosquitoes. It will define biomedical, environmental, and social risk factors for human infection. The Research Institute for Tropical Medicine (RITM) leads the conduct of the study in the Philippines, which started in 2013.

The Fifth Human Malaria Parasite

Scientists have yet to know exactly how the monkey malaria crossed over to the human population, but deforestation and changes in land use are seen as some of the contributing factors why this happens.

First isolated and described in the early 1930s, this malaria parasite was only known to infect long- and pig-tailed macaques in the Southeast Asia.

The first case of natural human infection of P. knowlesi was documented in 1965, followed by another case in 1971. It was not until 2004 when the next report appeared, showing an alarming number of cases of monkey malaria infections in humans in Malaysia. Human infections have also been reported in Thailand, Vietnam, Myanmar, Singapore, Cambodia, Indonesia, and the Philippines over the last decade.

Considered as the fifth human malaria parasite, P. knowlesi poses a serious public health problem as it multiplies in the human body every 24 hours, leading to severe malaria which can eventually result to death. Prompt diagnosis and treatment is needed; however, the guidelines for diagnosing and treating monkey malaria currently do not exist.

In Malaysia, around two thousand people are being infected by P.knowlesi yearly, making it a major public health problem in the country. The Philippines and P. knowlesi have a different story though. In the Philippines, the number of cases is very low–only 28 documented cases– with no reported deaths at all, said Dr. Effie Espino, head of the RITM Parasitology Department and Principal Investigator of the Monkeybar Project in the Philippines.

The ‘Holistic’ Approach

The Monkeybar project combines three disciplines —Primatology, Entomology, and Sociology—to get a holistic understanding of the monkey malaria situation in its study sites in Sabah, Malaysia, and the Palawan, Philippines.

The researchers have adapted the ecohealth approach to understand the nature and transmission of P. knowlesi. Scientists have yet to know exactly how the monkey malaria crossed over to the human population, but deforestation and changes in land use are seen as some of the contributing factors why this happens.

“The aim of the study is to look at risk but the exploration of the risk is not just biomedical but also the social aspect and ecological aspects of how a person puts him/herself at risk of infection,” explained Espino.

An EcoHealth approach focuses on investigating the complex interactions of the different components of the ecosystem, and how these interactions influence human health. Ms. Torno added that combining the fields of Primatology, Entomology, and Social Sciences enables them to get a “holistic” view of the situation.

According to Dr. Espino and Ms. Torno, this study is the first of its kind in RITM, and the first time that the Philippines has participated in a study as in-depth as the Monkeybar.

Convergence of Different Fields

The RITM team is collaborating with the University of the Philippines Los Banos (UPLB) for the Primatology and Social Science component of the research, while the Medical Entomology Department of RITM handles the Entomology component of the study.

The Primatology team studies two troops of monkeys in 3 sitios in Brgy. Bacungan, Puerto Princesa City, and follows their movement for a period of 12 months. The team identifies the movement patterns of the monkeys by transect walks, and their infection rate through fecal analysis. Meanwhile, the Entomology Team looks at the dynamics of the transmission of the virus to humans from mosquito vectors by studying their indoor and outdoor biting habits. They are collecting vector samples from three different ecotypes to determine where exactly the mosquitoes bite.

They apply various trapping techniques to identify the predominant malaria vector species in the site, their density and distribution, and their behavioral preferences. To identify the social risk factors that will make humans vulnerable to being infected, the study utilizes different social science methods such as focused group discussions, key informant interviews, GPS logging, transect walks, and photovoice. The community’s livelihood patterns, perceptions on febrile illnesses and malaria, and their treatment-seeking patterns are documented through these methods. A notable method used in the social science component is the use of the Global Positioning System (GPS) devices to monitor the geolocate participants’ movements. This is also a first of its kind in the Philippines.

“We have a cohort of seven households, and we follow them for 12 months. We give them a GPS device which they wear when they leave the house. They wear these the whole time they’re out of their houses. When they see a monkey, they press the button so their location is recorded,” explained Dr. Espino.

This research highlighted the importance of using a multidisciplinary approach in understanding a certain phenomenon.

“Before, we treat investigations separately Prima [tology] is different from Entomology, and Entomology is different from Social Science. We exist in different worlds. We thought we could exist as separate individuals, but no. We have to get together and come up with an understanding based on all possible scenarios, not just onesided,” said Ms. Torno.

Impact to Public Health

Currently, the research is on its final year in the Philippines. The team is in the process of analyzing the different types of data they have collected.

The team of scientists involved in this project targets to come up with recommendations to the policy for malaria program, and generate a risk map that could serve as guide for the local government units in the communities involved for malaria prevention and control.