Characterization of tungiasis infection and morbidity in Kenya reveals increase in disease burden during COVID-19 school closures (preprint)

Background: Tungiasis is a common but extremely neglected tropical skin disease caused by the sand flea Tunga penetrans. Female sand fleas penetrate the skin, particularly at the feet, and cause severe inflammation with pain and itching, acute and chronic morbidity. This study aimed to characterize disease burden in two highly affected regions in Kenya, to test the use of simple thermography to detect tungiasis-associated inflammation and to create a new two-level classification of disease severity that may be used for mapping, targeting, and monitoring interventions in future. Methods: : From February 2020 to April 2021, 3,532 pupils age 8-14 years were randomly selected in 35 public primary schools and examined for tungiasis and associated pathology. Of the infected pupils, 266 were randomly selected and their households visited. An additional 1,138 family members were examined. Infra-red thermography was used to assess inflammation. An all-pathology score was created combining the number of locations on the feet with acute and chronic pathologies and infra-red hotspots. Results: : Based on multilevel mixed effects logistic models, the odds of infection with tungiasis among school pupils was three times as high in Kwale than in Siaya (adjusted odds ratio (AOR)0.28, 95% CI 0.1-0.6);three times higher in males than in females (AOR2.9, 95%CI 2.2-3.7) and three times lower among pupils sleeping in a house with a concrete floor (AOR0.32,95%CI 0.24-0.44). The odds of finding an infected person among the household population during active school terms was approximately a half of that when schools were closed due to COVID-19 (AOR0.44, 95% CI 0.3-0.7). Infection intensity was positively correlated with inflammation (Spearman’s rho =0.68, p<0.001) and all-pathology score (rho 0.86, p<0.001). Based on the two-level classification, severe cases were associated with a threefold higher level of pain (OR2.99, 95% CI 2-4.4) and itching (OR3.31, 95% CI 2.2-4.9) than mild cases. Conclusions: : Thermography was a valuable addition for assessing morbidity and the proposed two-level classification of disease severity clearly separated patients with mild and severe impacts. The burden of tungiasis severely increased during COVID-19 restrictions and reinforced that underlying risks are found in the home environment more than in school.