Rapid assessment method for prevalence and intensity of Loa loa infection

Abstract

OBJECTIVE: To assess the validity of observations on eye worm and Calabar swellings for the rapid assessment of the prevalence and intensity of loiasis at the community level. METHOD: A total of 12 895 individuals over the age of 15 years living in 102 communities in Cameroon and Nigeria took part in the study. A standardized questionnaire was administered to participants from whom finger-prick blood samples were collected and examined for Loa loa microfilariae. Rapid assessments of the prevalence and intensity of loiasis were made on the basis of a history of eye worm or Calabar swellings. FINDINGS: There was a strong correlation between the indices of the rapid assessment procedures and the parasitological indices of L. loa endemicity. The rapid assessment indices were effective in diagnosing high-risk communities (sensitivity 94-100%; specificity 66-92%). The highest sensitivity (100%) and specificity (92%) were obtained with a rapid assessment procedure based on a history of eye worm lasting 1-7 days together with confirmation by the guided recognition of a photograph of adult L. loa in the eye. CONCLUSION: Rapid assessment of the prevalence and intensity of loiasis at the community level can be achieved using a procedure based on the history of eye worm lasting 1-7 days together with confirmation by the guided recognition of a photograph of an adult L. loa in the eye.

Keywords

• Loiasis/diagnosis
• Loiasis/parasitology
• Loiasis/epidemiology
• Loa/growth and development
• Eye foreign bodies/parasitology
• Inflammation/parasitology
• Endemic diseases/epidemiology
• Ivermectin/adverse effects
• Sensitivity and specificity
• Reproducibility of results
• Cameroon
• Nigeria