Prevalence and mean intensity of Clinostomum species infections in farmed Oreochromis species in Mpigi and Wakiso districts, Central Uganda

Abstract

Clinostomum species of fish cause economic losses through mortality, reduced growth, and diminished marketability. Yet, epidemiological data remains scarce in many developing countries on these digenean parasites. This cross‑sectional study assessed the prevalence and mean intensity of Clinostomum spp. in farmed Oreochromis spp. across 23 earthen pond and 7 cage farms in Wakiso and Mpigi districts, Central Uganda. A total of 286 tilapias (216 from ponds, 70 from cages; 259 O. niloticus, 27 O. leucostictus; 224 males, 62 females) were sampled. The fish were examined for Clinostomum larvae (metacercariae) using standard parasitology techniques in the laboratory at the College of Veterinary Medicine Animal Resources and Biosecurity, Makerere University. Eighty-six encysted yellow grubs were recovered in 9 pond fish from four farms in Mpigi District. Morphological analysis revealed 84 Clinostomum cutaneum larvae from the skin, and 2 Clinostomum complanatum from a gill cavity. The overall prevalence was 3.2% with a mean intensity of 9.5. Clinostomum cutaneum was the most common species with a prevalence of 2.8%, mean intensity of 9.3 while mixed infection with C. complanatum was at 0.4%. From the sampled tilapia, O. leucostictus showed a significantly higher prevalence and mean intensity of 11.1% and 23, respectively relative to O. niloticus at 2.3% and 2.8, respectively (p < 0.05). Female fish had a higher prevalence and mean intensity of 4.9 % and 12.7, respectively compared to the males at 2.7% and 3.3, respectively. However, these differences were not statistically significant (p > 0.05). Clinostomum spp. are therefore, prevalent in the study area, and appropriate control measures are required, as well as molecular confirmation of the species and risk factors associated with fish infections. Keywords: Aquaculture, Clinostomum, District, Metacercariae, Pond, Tilapia spp.