Preventing malaria after heavy flooding incidents

As temperatures grow warmer around the globe, we’ve witnessed an increase in the intensity and frequency of extreme weather events. Nearly half of the global disasters over the past two decades have been caused by extreme precipitation and flooding, including 64% of the events in the African region.

While heavy rainfall may wash away existing breeding sites, malaria vectors – mosquitos – quickly establish new breeding sites in the seemingly infinite number of small pools of stagnant water left behind by flooding, causing a surge in malaria cases months after the disaster.

A new study led by researchers at the University of North Carolina at Chapel Hill and the Mbarara University of Science and Technology (MUST) shows that preventatively treating children 12 and under with 3 monthly rounds of dihydroartemisin-piperaquine (DP) after severe flooding reduces the incidents of malaria. The results were published in the journal Clinical Infectious Diseases on September 9, 2021.

“These findings provide a proof-of-concept for using short periods of targeted chemoprevention to reduce the incidence of malaria after severe flooding,” said Ross Boyce MD, the lead author and an Assistant Professor in the Division of Infectious Diseases and Department of Epidemiology at the at the University of North Carolina at Chapel Hill School of Medicine.

Boyce and colleagues hypothesized that children DP – which has a long half-life that provides protection against malaria for 2-3 weeks after each dose – might serve as a valuable tool to mitigate malarial epidemics after flooding incidents.

To test their theory, they worked with a local non-governmental organization (NGO) to plan and carry out a chemoprevention intervention in Izinga village, which is situated between two flood-affected rivers in the Kasese District of western Uganda where UNC has a long-standing partnership. The Kasese District experienced severe flooding in May 2020, and has a climate where malaria vectors thrive.

A total of 554 children in Izinga were given at least one round of chemoprevention with 75% of them participating in at least two rounds. Two neighboring villages where there was no intervention served as controls. The incidence of malaria over the subsequent six months was 53% lower in Izinga than in the neighboring villages with an estimate of more than 300 cases averted at a cost of about $15 per case averted.

“These results, while achieved on a small scale are very exciting,” says Boyce. “We showed that we can prevent the excess burden of malaria attributable to flooding with a relatively brief and cost-effective intervention that utilizes an already-approved drug.” Given the well-documented associations between malaria infection and long-term cognitive performance in children, the benefit may be well beyond anything we were able to capture in this study.

“I am particularly proud of the way our team was able to carry out the study under challenging conditions, including a a global pandemic. If we can do it, then I’m confident that organizations like the Red Cross or Doctors Without Borders could do the same in response to similar disasters. For us, the next step is moving forward with a larger, randomized trial to confirm our results and determine the optimal combination of interventions, which might include bed nets, chemoprevention, and even treatment of breeding sites.”

Dr. Boyce ‘s malaria work in Uganda is supported by an award from the National Institutes of Health (K23AI141764). He has received additional funds from a Caregivers at Carolina Award made by the Doris Duke Charitable Foundation (Award 2015213) that were used to support this study.