Strongyloides stercoralis is a soil-transmitted
threadworm that is endemic in many tropical and subtropical areas of the world.
Now, researchers reporting in PLOS Neglected Tropical Diseases have
conducted a nation-wide parasitology survey of the Cambodian population and
concluded that nearly a third of the studied population is infected with S.
The threadworm is transmitted through infected larvae in the
soil and, like hookworms, infect humans through the skin. The worm can cause
long-lasting and potentially fatal infections in people. Larvae are not
detected by standard coprological diagnostics, so S. stercoralis has
been under-detected and overlooked for decades.
In the new work, Peter Odermatt, of the Swiss Tropical and
Public Health Institute, and colleagues used a diagnostic test that
detects S. stercoralis IgG antibodies in the urine. 7,246
enrolled study participants took the test and provided data on demography,
hygiene, and knowledge about helminth infection.
Overall, 30.5% of participants were infected with
threadworms. The rate in individual provinces ranged from 10.9% to 48.2%, with
prevalence rates below 20% in only five south-eastern provinces. The risk of
infection increased with age, and open defecation was associated with a higher
risk while knowledge about helminth infections lowered a person’s risk. In
addition, S. stercoralis infection was positively associated
with night temperatures, rainfall and distance to water, and negatively associated
with land occupied by rice fields. Advanced spatial statistical modeling
allowed predicting S. stercoralis in unsurveyed locations,
which lead to a unique result, namely a country-wide risk profile for S.
stercoralis infection in Cambodia.
“Our study represents a clear risk map of S.
stercoralis of a highly endemic setting,” the researchers say.
“Based on these data the population at risk can be quantified and planning
of concrete control approach become realistic.” Subsidies to support the
high cost of drugs, or affordable generics, are needed to start tackling the
worm, they add.
Forrer A, Khieu V, Vounatsou P, Sithithaworn P, Ruantip S, et al. (2019) Strongyloides stercoralis: Spatial distribution of a highly prevalent and ubiquitous soil-transmitted helminth in Cambodia. PLOS Neglected Tropical Diseases 13(6): e0006943. https://doi.org/10.1371/journal.pntd.0006943