Epidemiology of leptospira species among slaughterhouse workers and slaughtered cattle in the Bahr El Ghazal Region, South Sudan

Abstract

Leptospirosis, a neglected zoonotic disease caused by pathogenic Leptospira spp., poses significant public health risks, particularly to high-risk occupational groups such as slaughterhouse workers. Despite previous research on animal seroprevalence in South Sudan, data on human exposure using the gold-standard microscopic agglutination test (MAT) has been lacking. This doctoral study investigated the epidemiology of Leptospira spp. among slaughterhouse workers and slaughtered cattle in South Sudan’s Bahr El Ghazal Region using a cross-sectional design between February 27 and March 30, 2023. Blood samples from slaughterhouse workers (n = 250) and cattle (n = 402) were tested using MAT with a panel of 12 Leptospiral serogroups, including those previously reported in livestock in South Sudan and the East African Region. Urine samples from cattle (n = 400) were analyzed via real-time quantitative Polymerase Chain Reaction (RT-qPCR). MAT results showed a 6.4% seropositivity among workers and 81.8% in cattle, with Leptospira serovars Tarassovi and Australis predominating in humans, while serovars, Tarassovi and Kenya in cattle. The prevalence of urinary Leptospira shedding in cattle was 6.0% by PCR. Probable recent infections (MAT titer ≥800) were detected in 0.8% of workers and 33.1% of cattle. Key occupational risk factors among workers included flaying, wearing an apron/overall, and handling a higher number of animals per day. In cattle, older age, female sex, and exotic breed were associated with higher seropositivity. Genotypic characterization using Oxford Nanopore Technology (ONT) was challenged by low Leptospira-specific DNA concentrations. Bayesian modeling estimated the true prevalence at 10% in workers and 85% in cattle, with a 78% likelihood of infection occurring within slaughterhouses. These findings underscore the endemic nature of leptospirosis in the region and its significant unrecognized occupational risks. Given the risk of human exposure, acute and chronic leptospiral infections in humans and cattle, enhanced research and surveillance are essential to guide effective control. Strengthening diagnostic capabilities and implementing preventive measures will help mitigate future outbreaks, enhance public health outcomes, and improve productivity in South Sudan.

Keywords: Leptospirosis, Leptospira species, Slaughterhouse