A case control study of cutaneous leishmaniasis outbreak in Diyala, Iraq, 2018: how many exposed cases could we have prevented? (Preprint)

BACKGROUND In 2018, an outbreak of cutaneous leishmaniasis occurred in Diyala province in Iraq. Several risk factors were identified in a prior study; however, the impact of removing modifiable risk factors on the occurrence of cutaneous leishmaniasis were not measured. OBJECTIVE This study aims to measure the impact of removing modifiable risk factors of cutaneous leishmaniasis on the occurrence of the disease. METHODS We conducted a population-based unmatched case-control study in two conveniently selected districts in Diyala province. All cases were included. Controls were chosen preferentially according to the site where cases occurred. A structured questionnaire was used to collect data. The unadjusted odds ratios (OR) and 95% confidence intervals for each risk factor was calculated by using binary logistic regression. We also calculated the attributable fraction and 95% CI of the modifiable risk factors. A P-value of < 0.05 was considered statistically significant. RESULTS Data from 844 persons (cases=432, 51.2%) persons were analyzed. Cases were more likely than controls to report a history of previous displacement, electricity supply less than 12 hrs, living in rural areas, living in a clay house, having their indoor not painted, presence of rodents inside the house, having (chicken only, sheep only, and both) and (mixed, dogs and sheep, dogs and chicken) within a distance less than 100 m, fogging, bed net usage, and sleeping outside / mixed (inside and outside) than controls. Data show that 70%-80% of % cases exposure was associated with displacement, presence of rodents inside the house, and presence of animals within 100 M of the house, presence of animals (whether chicken only/sheep only/both or mixed, dogs and sheep, dogs and chicken), and sleeping outside. About 40%-50% of the exposed cases occurred because of living in a clay house, living in rural areas, having the indoor not painted, having electricity supply less than 12 hrs, and using bed net. CONCLUSIONS Prevention and control of CL requires a multifaceted approach that rely on changing environmental conditions, housing conditions, as well as human behavior. Fogging and bed net use were not effective because the underlying housing characteristics and human behavior provided a good culture for the disease.