In the Journals

Decreased malarial transmission leads to increased susceptibility among children

Decreases in the proportion of children admitted to the hospital for malaria from 1998 to 2008 were associated with a significant increase in malarial admissions among older children between 2009 to 2014, according to recent research in PLoS Medicine.

The researchers wrote that this association suggests that reduced exposure to malarial parasites early in life decreases opportunities for children to develop immunities to malaria, thus reducing their protection later in childhood.

“Some parts of Africa have seen marked reductions in malaria transmission with associated reductions in malaria-related morbidity and mortality,” Polycarp Mogeni, MSc, of the KEMRI-Wellcome Trust Research Programme in Kilifi, Kenya, and colleagues wrote. “Children acquire immunity to malaria following repeated infections, and hence, there is an inverse relationship between the intensity of malaria transmission and age of susceptibility to malaria. The objective of the analysis was to describe trends of malaria admissions by age group and examine the efficacy of community insecticide-treated net use.”

The researchers studied data from 69,104 children aged 3 months to 13 years from Kilifi County Hospital in Kenya. To gauge trends in malaria prevalence, the researchers analyzed longitudinal data from 1990 and 2014. Community-level use of insecticide-treated nets was compared with prevalence of admissions for malaria infection to determine if bednet usage effectively reduced malaria among children.

Study results showed that the proportion of malaria-positive admissions decreased from 56% in 1998 to 7% in 2009. The researchers, however, found that prevalence then rose to 24% by 2014, with older children accounting for most of the increase after 2009.

The researchers also cited an association with community-level use of insecticide-treated nets and a lower risk for children to present with malaria.

“As countries and regions make progress in malaria control, maintaining control measures will be essential: In fact, further progress will be required to offset the increasing rates of malaria in older children,” Mogeni and colleagues wrote. “Achieving insecticide-treated net coverage close to 100% shows promise as a strategy but will require novel strategies, particularly among groups that seem less keen to use insecticide-treated nets, such as adolescent males and young adults.”

In a related editorial, Lorenz von Seidlein, MD, of the Mahidol-Oxford Tropical Medicine Research Unit in Thailand and Jakob Knudsen, MA, of the Royal Danish Academy of Fine Arts Schools of Architecture, Design and Conservation, in Copenhagen, Denmark, wrote that Mogeni and colleagues’ proposal to increase bednet supply and usage may not be enough to decrease malaria transmission.

“Following the notion that bednets are a good thing and, therefore, more bednets must be even better, the authors propose universal coverage,” von Seidlein and Knudsen wrote. “The indoor climate in the typical African home in the hot–humid zone is uncomfortable. In such an environment, an uncomfortable room will become unbearable by hanging up a bednet. The residents have to choose between the discomfort caused by bednets or mosquito bites. Under these circumstances, the continued distribution of additional bednets is unlikely to increase bednet usage as hoped.

“More effort should be made on community engagement and education to discuss novel architecture of new houses being built in Africa, to gradually integrate housing characteristics that improve ventilation while minimizing vector entry.” – by David Costill

Disclosure: von Seidlein reports receiving a stipend as a specialty consulting editor for PloS Medicine and serves on the journal’s Editorial Board with one of the researchers.

Decreases in the proportion of children admitted to the hospital for malaria from 1998 to 2008 were associated with a significant increase in malarial admissions among older children between 2009 to 2014, according to recent research in PLoS Medicine.

The researchers wrote that this association suggests that reduced exposure to malarial parasites early in life decreases opportunities for children to develop immunities to malaria, thus reducing their protection later in childhood.

“Some parts of Africa have seen marked reductions in malaria transmission with associated reductions in malaria-related morbidity and mortality,” Polycarp Mogeni, MSc, of the KEMRI-Wellcome Trust Research Programme in Kilifi, Kenya, and colleagues wrote. “Children acquire immunity to malaria following repeated infections, and hence, there is an inverse relationship between the intensity of malaria transmission and age of susceptibility to malaria. The objective of the analysis was to describe trends of malaria admissions by age group and examine the efficacy of community insecticide-treated net use.”

The researchers studied data from 69,104 children aged 3 months to 13 years from Kilifi County Hospital in Kenya. To gauge trends in malaria prevalence, the researchers analyzed longitudinal data from 1990 and 2014. Community-level use of insecticide-treated nets was compared with prevalence of admissions for malaria infection to determine if bednet usage effectively reduced malaria among children.

Study results showed that the proportion of malaria-positive admissions decreased from 56% in 1998 to 7% in 2009. The researchers, however, found that prevalence then rose to 24% by 2014, with older children accounting for most of the increase after 2009.

The researchers also cited an association with community-level use of insecticide-treated nets and a lower risk for children to present with malaria.

“As countries and regions make progress in malaria control, maintaining control measures will be essential: In fact, further progress will be required to offset the increasing rates of malaria in older children,” Mogeni and colleagues wrote. “Achieving insecticide-treated net coverage close to 100% shows promise as a strategy but will require novel strategies, particularly among groups that seem less keen to use insecticide-treated nets, such as adolescent males and young adults.”

In a related editorial, Lorenz von Seidlein, MD, of the Mahidol-Oxford Tropical Medicine Research Unit in Thailand and Jakob Knudsen, MA, of the Royal Danish Academy of Fine Arts Schools of Architecture, Design and Conservation, in Copenhagen, Denmark, wrote that Mogeni and colleagues’ proposal to increase bednet supply and usage may not be enough to decrease malaria transmission.

“Following the notion that bednets are a good thing and, therefore, more bednets must be even better, the authors propose universal coverage,” von Seidlein and Knudsen wrote. “The indoor climate in the typical African home in the hot–humid zone is uncomfortable. In such an environment, an uncomfortable room will become unbearable by hanging up a bednet. The residents have to choose between the discomfort caused by bednets or mosquito bites. Under these circumstances, the continued distribution of additional bednets is unlikely to increase bednet usage as hoped.

“More effort should be made on community engagement and education to discuss novel architecture of new houses being built in Africa, to gradually integrate housing characteristics that improve ventilation while minimizing vector entry.” – by David Costill

Disclosure: von Seidlein reports receiving a stipend as a specialty consulting editor for PloS Medicine and serves on the journal’s Editorial Board with one of the researchers.