Spatial concentration and seasonal clustering of Leishmania tropica in Mosul, Iraq: a retrospective patient data-based analysis

Abstract

Cutaneous leishmaniasis remains a major public health issue in Iraq, with potential influences including local environment, vector ecology, environmental change, human migration, and travel. We reviewed 191 hospital records deemed suitable for analysis in Mosul, obtained from Mosul General Hospital for the period 2025-2026. Available variables were sex, age, diagnostic result, date, and address. Diagnosis in routine practice was based on lesion smear together with clinical and laboratory assessment. Categorical variables were summarized as frequencies and percentages. Age was described by mean, standard deviation, median, interquartile range, and range. Group comparisons were performed using Pearson's chi-square test or Fisher's exact test for categorical variables and the Mann-Whitney U test for age. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for selected 2x2 comparisons. 191 records, 175 were positive and 16 were negative, yielding a positivity of 91.6% (95% CI, 86.8%-94.8%). Positive records were predominantly male in absolute number (63.4%), but positivity did not differ significantly by sex within the tested hospital population (Fisher's exact p = 0.424). The age of positive records ranged from 0.5 to 75 years, with a mean of 23.3 ± 20.2 years and a median of 20 years (IQR, 5-36). The largest age stratum was 25-44 years (24.6%), followed by 5-14 years (22.3%) and 1-4 years (18.9%). Female positive records were younger than male positive records (median, 12 vs 25 years; Mann-Whitney U p = 0.033). Positive records were concentrated in November-February (66.9%), with peaks in November and December. When months were collapsed into November-February versus March-October, a higher proportion of positivity was observed in the cooler-month cluster (OR, 2.59; 95% CI, 0.92-7.31), although this did not reach formal statistical significance (Fisher's exact p =< 0.005). At the locality level, Muhalbia, Alshoora, Hamamali, Qaeera, and Talabta accounted for 53.1% of all positive records. showed a strongly focal distribution of cutaneous leishmaniasis records in both time and place. These findings support geographically targeted surveillance and control within the hospital catchment while underscoring the limits of hospital-record data for estimating population-level incidence