Microscopy underestimates submicroscopic malaria infections in Ethiopia's southern rift valley: a community-based cross-sectional study.

BACKGROUND

Efforts to control malaria face several challenges, including the presence of parasite reservoirs within the community that contribute to disease transmission. This study aimed to assess malaria prevalence among community members using microscopy and nested polymerase chain reaction (PCR) to detect parasite reservoirs in malaria-endemic settings.

METHODS

A community-based cross-sectional study was conducted in malaria-endemic districts of the Gamo Zone in the southern Rift Valley of Ethiopia. The research was conducted as part of a baseline assessment for a trial evaluating the impact of house screening and ivermectin treatment of domestic animals on malaria incidence. Capillary blood samples were collected from the study participants to prepare blood films and dried blood spots. Malaria parasite detection and species identification were performed using both microscopy and nested PCR.

RESULTS

Of 4745 participants screened by microscopy, malaria prevalence was 2.7% (126/4745; 95% CI: 2.2-3.2%). Nested PCR was performed on 1183 samples, including 97 microscopy-positive and 1,086 microscopy-negative samples. PCR confirmed 67% (65/97) of microscopy-positive cases, yielding a PCR-corrected microscopy prevalence of 1.4% (65/4745). Submicroscopic infections were detected in 6.1% (66/1086) of microscopy-negative samples. Malaria prevalence across Kebeles ranged from 0.5-2.3% by microscopy and 4.1-9.6% by PCR. Species misclassification by microscopy was common: 19.5% of P. falciparum infections were misidentified as P. vivax, 14.0% of P. vivax as P. falciparum, and 33.0% of microscopy-positive samples were PCR-negative.

CONCLUSION

These findings emphasize that community-based malaria diagnosis using microscopy underestimates malaria prevalence, highlighting the need for improved diagnostic methods.