Wednesday, June 22, 2016

Silent infections

Just out in PLOS Neglected Tropical Diseases is a study that followed around 400 Bangladeshi children for their first two years of life. They found that more than three-quarters (77%) of the children became infected with Cryptosporidium spp at least once before reaching two years of age. Even more surprising is that 67% of these infections were asymptomatic, meaning that the children did not have diarrhea or other symptoms. The authors found that children with Cryptosporidium spp. infection had more than a 2-fold increased risk of severe stunting at age two compared to uninfected children. Aysmptomatic Cryptosporidium spp infections have previously been found to cause stunting among children in Peru, and asymptomatic Giardia infections in Brazil have also been linked to stunting. Silent infections are not limited to protozoa, a global case-control study found that 72% of children under five years with no clinical signs of diarrhea (controls) were infected with at least one pathogenic virus, bacteria, protozoan, or helminth and 31% were infected with two or more of these enteric pathogens. In Dhaka, Bangladesh, a median of 3 enteric pathogens was detected in non-diarrhea stool samples from children 0-12 months old. These studies contribute to growing evidence that asymptomatic infection with enteric pathogens is extremely common and has detrimental impacts on child growth among children in developing countries. Controlling silent infections in these settings will be difficult with treatment alone, suggesting prevention is necessary with environmental and behavioral interventions.