Leptospira seroprevalence and associated risk factors among slaughterhouse workers in Western Bahr El Ghazal State, South Sudan

by David Onafruo, Anou Dreyfus, Joseph Erume, Clovice Kankya, Ambrose Jubara, Ikwap Kokas, Terence Odoch, Musso Munyeme, Lordrick Alinaitwe, Estella Kitale, Peter Marin, Esther Sabbath, Jörn Klein

Leptospirosis is a neglected re-emerging and occupational zoonotic disease worldwide. In Africa, contact with livestock is postulated as a potential source of environmental contamination and a source of human Leptospira exposure, though pathways remain unknown. Recently, we confirmed Leptospira exposure and shedding among slaughtered cattle in Western Bahr El Ghazal. In the current study, we sought to determine corresponding occupational leptospiral seropositivity, associated risk factors and the prevalence of febrile illness among slaughterhouse workers.

Between 27^th February and 30^th March 2023, we collected blood and interviewed 250 consenting slaughterhouse workers of the same facilities from which the cattle samples were collected. The workers were screened for leptospiral antibodies using the Microscopic agglutination test (MAT), based on a panel of 12 including those previously reported in livestock in South Sudan and the East African Region.

Of the 250 participants, 16 were seropositive 16/250, (6.4%, 95% CI = 3.2–10.2). Two seropositive individuals 0.8% (2/250) had MAT titers ≥ 800, indicative of probable recent leptospiral infection. Moreover, 42.4% (106/250) of the respondents reported experiencing fever in the past one month and 36.0% (90/250) sought medical attention. Among those seeking medical care for febrile illnesses, diagnostic tests revealed 9.2% (23/250) with malaria, 7.6% (19/250) with typhoid, 16.8% (42/250) with both malaria and typhoid coinfections, 1.6% (4/250) with brucellosis, and no cases of leptospirosis had been considered. Most seropositive individuals reacted to serovar L. borgpetersenii Tarassovi 2.4% (6/250) and L. interrogans sv Australis 2.4% (6/250). The factors associated with seropositivity included flaying, with persons who flay animals having 14.9 times, (95% CI, 2.5–88.9) greater odds of being seropositive than persons who do not flay animals (P = 0.003), people who wore an apron/overall were 10.6 times (95% CI, 1.6–67.6) more likely to be seropositive than people who did not wear an apron/overall (P = 0.012). An increase in the number of carcasses handled per day by one increases the odds of exposure by 2.7 times (95% CI, 1.6–4.5), (P = 0.001).

Finding seropositive workers in cattle slaughter facilities in Western Bahr El Ghazal, South Sudan, and similar serogroups as previously found in the cattle slaughtered at these facilities implies activities like animal slaughter that bring humans into close contact with animals could be one pathway for human Leptospira exposure in South Sudan. This could also highlight leptospirosis as a potential public health threat to those in frequent contact with cattle, including farmers, those in animal transportation, and veterinarians. The role of leptospirosis in cases of undifferentiated fever in South Sudan may also be worth investigating, especially in cases where occupational exposure is suspected. Further research including animals, the general public, farmers, and hospitalized patients is proposed to fully understand the burden of human leptospirosis. Including the serovar and serogroup Tarassovi and Australis in future vaccine development and serodiagnostic panels for South Sudan is highly recommended.