December 9, 2011
PHILADELPHIA — New data from Kenya indicate that there is an under-recognized burden of parasitism in younger children that may be linked to a decreased response to standard childhood vaccinations, according to a presenter here at the American Society of Tropical Medicine and Hygiene 60th Annual Meeting.
Children are at high risk for soil-transmitted helminths (STHs) and protozoal infections, and these parasitic infections have detrimental effects on weight, height and head circumference growth rates in children aged 0 to 36 months. Certain parasitic infections during childhood may also be linked to decreased response to standard childhood vaccinations, according to results of a study by A. Desiree LaBeaud, MD, of the Children’s Hospital Oakland Research Institute in California, and colleagues.
“Vaccines are among the most cost-effective strategies for infectious disease prevention in the world. But unfortunately, there is a disparity, and children in developing nations are often much less responsive to vaccinations compared with their counterparts in developed nations,” LaBeaud said during a presentation. “While there are many reasons for this, including cold chain issues, infrastructure, HIV/AIDS and malnutrition, chronic parasitic infection plays a large role in weakened vaccine response.”
To document the prevalence of parasites and their effects on growth and response to childhood vaccines in young children in coastal Kenya, the investigators collected stool, urine and blood samples from children at 6-month intervals until age 3 years and tested for STHs (Ascaris, Trichuris, hookworm and Strongyloides), protozoa (malaria, Giardia) and schistosomiasis. Height, weight and head circumference were measured at each visit. A total of 545 infant–maternal pairs were enrolled in the study that began in 2007, and infections in both mothers and infants were documented.
Of 545 children, 32% were infected with one parasite, and 8% of the children were infected with more than one parasite. Hookworm was the most prevalent STH (11%), followed by Trichuris (10%), Ascaris (4%) and Strongyloides (2%). Giardia was the most prevalent protozoan (13%), followed by malaria (12%). Immunoglobulin G4 testing revealed that 4% of the children had schistosomiasis.