School-age children with no symptoms of malaria could serve as super-spreaders of the disease, an observation that could open a new chapter in malaria control heard a meeting. The new results of a study conducted in Uganda were released at the American Society of Tropical Medicine and Hygiene’s annual virtual meeting last month (November 18).
“Understanding who transmits malaria is very important in areas where malaria control is successful,” said Teun Bousema, co-author of the study and professor of tropical infectious disease epidemiology, specializing in the biology and epidemiology of Plasmodium falciparum at Radboud University Medical Center in the Netherlands.
Bousema tells SciDev.Net that those who run control programs need to know if malaria can return and who in the human community can cause mosquito infections to determine when disease control can become less stringent or when it is very unlikely to recur.
“In a way, our study is a blueprint of what to expect in other countries where mosquito control is very successful. Malaria will not go away completely. It will persist in some populations,” added Chiara Andolina, co-author of the study and a PhD student at Radboud University Medical Center who presented the results at the meeting. “We now have the first direct evidence that even in locations under very tight malaria control, a small number of asymptomatic super-spreaders can quietly maintain transmission – and finding and treating it could prove very difficult.”
The researchers studied the transmission of malaria in children with symptoms of malaria and in children who showed no symptoms in the Tororo district in eastern Uganda. Malaria control measures have been targeted in the area, including regular distribution of insecticide-treated bed nets, spraying insecticides with internal debris, and access to effective anti-malarial drugs.
The researchers conducted regular tests for signs of malaria parasites in 531 people, including children aged five to 15, over a period of 24 months.
According to the results presented at the meeting, a school-age child who showed no symptoms despite seven different variants of the malaria parasite Plasmodium falciparum was “responsible for 24.7 percent of all infected mosquito infections observed”.
“In this unique longitudinal study, we find that asymptomatic infections occur [with no symptoms] School-age children are responsible for the majority of relay events, “the study adds.
They are very susceptible to infection and will hold their infections longer because they have some level of immunity that prevents symptoms but not infections. Malaria-free school initiatives can have important implications. Not only for school children but, as we show, also for the general public, as they are important carriers of the infection. “
Teun Bousema, Co-Author, Professor of Tropical Infectious Disease Epidemiology, Radboud University Medical Center, The Netherlands
Andolina tells SciDev.Net that such children can be easily attacked with interventions such as medication that can prevent them from getting parasites in the first place, as they are readily available in their schools. Lauren Cohee, a pediatric infectious disease specialist at the University of Maryland School of Medicine in the United States, says the results provide insights into malaria control.
“The extent to which transmission can be controlled by a small number of highly infectious people is surprising and may open a new chapter in malaria control,” Cohee added. However, Cohee explains that traditionally the yardstick for measuring malaria control efforts has been how many lives are saved or how many deaths are averted. “While this is clearly a key metric, policymakers should consider the impact of control measures on transmission,” added Cohee.