Germs can hamper child growth without symptoms of illness

Muhammad Zahir Hassan Nabil

Children’s growth may be affected by certain diarrhoea-causing germs, even if they are not showing symptoms of illness.

The pathogen Cryptosporidium is a major cause of childhood diarrhea in low- and middle-income countries. New findings from a study with icddr,b suggest that some children with Cryptosporidium infection experienced growth faltering without the usual symptoms of diarrhoea, dehydration and coughing.

Substandard sanitation can harm children's growth without signs of illness. Photo: GMB Akash / icddr,b

“We already have evidence that Cryptosporidium infection is linked to growth faltering,” says Dr ASG Faruque, icddr,b senior scientist and senior author of the study published in Clinical Infectious Diseases.

“What is new and interesting is that, infections caused by one variant Cryptosporidium meleagridis or C. meleagridis were nearly all asymptomatic, that is, infected children experiencing growth faltering had no symptoms of illnesses,” he explains.

Scientists across the world have been investigating whether diarrhea in early childhood reduces the height of children, also known as stunting. Diarrhoeal diseases are still the second leading cause of death for children under five years of age, according to World Health Organization (WHO).

Dr Tahmeed Ahmed, icddr,b senior director of nutrition and clinical services and senior co-author of the study, observes that for those surviving, early childhood is a critical time to be affected by stunting.

“What we need now is scaling up of hygiene practices and a vaccine against this germ as a long term measure,” adds Dr Tahmeed, who has been working over decades on maternal and child nutrition.


Cryptosporidiosis: Burden in Bangladesh and worldwide

A recent study with icddr,b explored whether children’s growth faltering was linked with pathogen-specific diarrhoea. It found that growth deficit was associated with episodes of diarrhoea related to Cryptosporidium among other pathogens.

“It is true that diarrhoea affects children’s growth but evidence from Bangladesh suggests that certain diarrhoea-causing pathogens are more specifically responsible for impairing child growth,” says Dr Rashidul Haque, icddr,b senior scientist and co-author of the study published in American Journal of Epidemiology.

Tackling sanitation and hygiene in urban slums in Dhaka is challenging. Photo: GMB Akash / icddr,b

Evidence from countries in the global South according to a recent MAL-ED (Etiology, Risk Factors and Interactions of Enteric Infections and Malnutrition and the Consequences for Child Health and Development) study has indicated that 65% of children experienced Cryptosporidium infection during the first two years of life.

“Cryptosporidium was associated with severe diarrhea and dehydration, and in two South Asian sites, with stunted growth at age two,” read findings published in Clinical Infectious Diseases.

According to the 2016 Global Burden of Diseases, Injuries, and Risk Factors (GBD) study, Cryptosporidium infection was the fifth leading cause of diarrhoea in children younger than 5 years that caused more than 48,000 deaths.

Cryptosporidium parvum. Photo: microbiologybytes. CC BY-SA 2.0

Findings published in Lancet Global Health found that each episode of diarrhoea caused by Cryptosporidium infection was associated with stunted growth in children.

Cryptosporidium was significantly associated with moderate-to-severe and less-severe diarrhoea in children under 2 years, note findings published in PLOS NTDs as part of the Global Enteric Multicenter Study (GEMS) conducted in the sub-Saharan Africa and India, Pakistan, Bangladesh, Nepal, Afghanistan regions.


How to prevent a less known foe?

Cryptosporidium was first described as a pathogen causing diarrhoea in animals in 1907. Since its identification as affecting humans in the 1970s, icddr,b remained at the forefront of conducting research on how patients were infected due to this pathogen in Bangladesh. Evidence from as early as the 1980s shows that infections were common, especially in young Bangladeshi children.

Dr Rashidul Haque mentions that currently there is no vaccine or effective drug to prevent and treat this infection.

“However, parasite-specific antibodies in breast milk may help develop passive immunity in children,” he adds.

Drinking boiled water and breastfeeding protects children from many enteric infections. Photo: Syed Hasibul Hasan / icddr,b

According to Dr Haque, findings published in Clinical Infectious Diseases from earlier studies with icddr,b indicated that certain antibodies found in breast milk help children prevent Cryptosporidium infection.

“In settings like Bangladesh with often compromised water, sanitation and hygiene, drinking boiled water is a simple measure to prevent Cryptosporidium infection. But its importance is still not understood by many,” observes Dr Haque.