Determinants of clinical leptospirosis in Nepal

Leptospirosis is an important zoonotic disease in Nepal; however, there is a lack of information on sources of leptospirosis infection for people and associated risk factors. We implemented a case-control study nested within a cross-sectional survey to investigate zoonotic risks of human leptospirosis among adult, febrile patients seeking treatment in healthcare centres in Kaski District, Nepal, from April to October 2013. The study population was 239 febrile patients; the data consisted of paired blood samples; questionnaires on clinical symptoms; occupational, environmental and animal exposures; and a blood sample from animals in the household. In total, 63 cattle, 92 buffalo, 181 goats, 20 dogs and 14 rodents from 119 households were blood sampled. Serology was performed on the samples using the microscopic agglutination test (MAT) for a panel of 20 serovars with a starting dilution of 1:50. Clinical leptospirosis was defined as a titre of 1:400 or stronger, or a 4-fold or greater rise between acute and convalescent titres, or evidence of seroconversion for one or more serovars represented by a titre of <1:50 in the acute sample and a titre of ≥1:100 in the convalescent sample. The prevalence of clinical leptospirosis was 5.4% (95% CI 2.6%-8.3%). The most common symptoms among recruited participants were loss of appetite and lethargy followed by chills, profuse sweating and backache. No individual clinical symptom nor combination of any two symptoms was significantly associated with clinical leptospirosis. However, owning goats (OR 1.3, CI 95% 1.05-1.66), working in rice fields (OR 1.3, CI 95% 1.11-1.72) and male gender (OR 4, CI 95% 1.12-17.26) significantly increased the risk of clinical leptospirosis in humans. Findings suggest that leptospirosis should be considered in the clinical differential diagnosis among febrile adult patients in Nepal, especially for men, goat owners and/or those who work in rice fields.