High burden of intestinal protozoan infections revealed by molecular diagnostics among schoolchildren in the Marshall Islands: species diversity, genotyping, and risk factors.

OBJECTIVES

Intestinal protozoan infections remain a significant public health challenge in resource-limited Pacific Island settings, yet molecular epidemiological data for the Republic of the Marshall Islands (RMI) are scarce.

METHODS

We conducted a cross-sectional molecular epidemiological study of waterborne protozoan infections among 215 primary schoolchildren in Majuro Atoll, RMI. Stool samples were examined using PCR-based assays targeting Cryptosporidium spp., Entamoeba spp., and Giardia lamblia, with species identification and genotyping by PCR-RFLP, nested multiplex PCR, and assemblage-specific PCR. Risk factors were assessed by logistic regression.

RESULTS

Molecular detection revealed high prevalences of E. histolytica (97.2%), G. lamblia (87.0%), and Cryptosporidium spp. (2.8%). E. dispar was detected in all samples (100%) and E. moshkovskii in 75.3%. Three Cryptosporidium species were identified: C. parvum (66.7%), C. bovis, and C. felis, indicating zoonotic transmission. Giardia Assemblage B predominated (53.5%). PCR demonstrated substantially higher sensitivity than conventional microscopy, detecting 13-fold more G. lamblia and 35-fold more E. histolytica infections. Risk factor analysis identified significant associations between E. histolytica infection and urban residence, and between Cryptosporidium infection and consumption of food picked from the ground (OR = 6.107; 95% CI: 1.174-31.782; P = 0.032).

CONCLUSION

These findings reveal a previously underestimated burden of intestinal protozoan infections in the Marshall Islands, highlighting the need for molecular surveillance, targeted hygiene education, and improved water sanitation.