Paratuberculosis in small ruminants in the Sudan: prevalence and risk factors.

Background: Paratuberculosis (PTB), caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a contagious and chronic enteric disease of ruminants and many non-ruminants leading to emaciation and death of the animal. PTB is poorly investigated in sheep and goats in Sudan, where these animals contribute significantly to food security and poverty alleviation as sources of income. They also play an important role in the national economy through animal exports. The objectives of this study were to investigate the prevalence of PTB and associated risk factors in small ruminants. Blood and faecal samples were collected from 818 sheep and goats aged > 1 year in 111 flocks distributed over five states (Blue Nile, West Kordofan, Khartoum, the Gezira and White Nile) of the country from November 2020 to October 2022. Serum samples were tested by an enzyme-linked immunosorbent assay (ELISA) for detection of MAP antibodies and the faecal samples were tested for MAP DNA using a recombinase aided amplification (RAA) assay.

Results: The overall true animal-level prevalence of PTB was 10.7% by RAA (4.2% in sheep, 6.5% in goats) and 1.7% by ELISA (0.7% in sheep, 1.0% in goats). At the flock level, prevalence was 41.8% by RAA and 8.5% by ELISA. While no significant associations were found between animal-level factors and PTB, several flock-level factors including breed homogeneity, source of new animals, management system, animal movement, separation of sick animals, and flock history of PTB were significantly associated with MAP detection (P < 0.05).

Conclusions: The high flock-level prevalence of MAP DNA indicates a potential risk for environmental dissemination, especially under open grazing systems. Despite the relatively low seroprevalence, molecular detection suggests subclinical infection may be underdiagnosed. These findings highlight the importance of using combined diagnostic methods for effective PTB surveillance and control. Improved flock management practices are recommended to reduce MAP transmission and environmental contamination.