The month in which your child is born matters more than you think.
For the first time, researchers have proved the birth month could dictate whether or not the child will get life-threatening malaria episodes in their childhood.
The researchers, from the Kemri/Wellcome Trust, examined the medical records of hundreds of children to understand why some easily contract malaria, compared to others of the same age group living in the same endemic area.
They found that children born between January and March are most vulnerable to clinical malaria. Those born in October to December showed the highest natural protection against the disease.
Clinical malaria refers to cases with known symptoms and a positive rapid diagnostic test confirming the presence of the plasmodium parasite in the blood.
The scientists explained why the October-December birth months offer protection.
“Being born during Q4 in this cohort means that infants may acquire their first infection at the age of four to six months towards the end of maternal protection, assuming that the main transmission season in Junju starts around April,” they said.
Alternatively, it is possible their mothers got infected during the second trimester. Malaria infections during pregnancy can alter an infant’s susceptibility to clinical malaria.
Maternal nutrition, which changes with seasons, also affects a child's health.
The researchers looked at a sample of 544 children, aged from one year to 12, between 2006 and 2018 in Junju, Kilifi county. They excluded those with sickle cell traits, which is well-known to protect against severe malaria.
“Apart from age and exposure, our analysis suggests that the time of year when an individual is born has a protective effect against clinical episode and that this effect can last for many years of early childhood,” they said.
“We found that individuals born during the last quarter of the year (October to December) had a reduced risk of experiencing clinical episodes. They also manifested a lower number of total episodes compared to other age-matched children under similar exposure conditions.”
Their study, “Individual-level Variations in Malaria Susceptibility and Acquisition of Clinical Protection”, is published in the Wellcome Open Research journal.
The Kenyan authors include Francis Ndungu, Jedida Mwacharo, Joyce Mwongeli, Joshua Wambua, Edward Otieno and Philip Bejon of Wellcome Trust in Kilifi.
Children with the second-highest level of protection are those born from April to June, followed by the July–September group.
Those with the lowest protection and therefore most vulnerable to clinical malaria are those born between January and March.
The scientists also said nutritional intake during pregnancy, which in many parts of Kenya changes significantly between seasons, can have a lasting effect on the child’s susceptibility to disease.
“Unfortunately, we cannot say whether the effect that we observe is due to in utero exposure during pregnancy or first exposure under waning maternal protection,” the researchers said, calling for more studies.
Another important finding was that a clinical malaria episode in children does not protect them against similar attacks in future.
In fact, the researchers found that children who contract malaria have a higher risk of getting the disease again compared to similar aged children.
It is not clear if this is due to genetic susceptibility to clinical malaria, or whether exposure to the parasite early in life actually led to impaired immunity to malaria, which in turn leads to further episodes of malaria in the future.
A 2019 study in Kilifi confirmed that individuals who carry asymptomatic infections are at an increased risk of experiencing a symptomatic episode in the near future.
The researchers also noted that as children grew older, they gained more immunity against clinical malaria, regardless of the number of past infections.
“The overall negative effect of the interaction between age and number of previous episodes therefore strongly suggests an independent protective effect of age, regardless of the previous number of episodes,” they said.
(Edited by V. Graham)
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