South Asian Journal of Parasitology

Background: Tilapia fish is the third most farmed fish in the world, accounting for about 4% of global agricultural production. Few studies have examined the relationship between intestinal helminth infections and physicochemical characteristics of aquatic environments, including temperature, pH, dissolved oxygen, salinity and total dissolved solids, which may influence parasite occurrence and transmission.

Aim: This study compared the prevalence of intestinal helminth parasites in Tilapia guineensis from Iwofe and Bonny stations of the New Calabar River, Rivers State, Nigeria, in relation to fish morphometry and the physicochemical parameters of the water.

Study Design: A random sampling technique was adopted in which each Tilapia guineensis encountered at the selected study sites had an equal probability of being purchased for the experiment, irrespective of the fishers and sellers, provided that the fish were available for purchase at the time of the visit.

Place and Duration of Study: Hydrobiology Laboratory, Department of Animal and Environmental    Biology, Faculty of Sciences, University of Port Harcourt, Port Harcourt, Nigeria, between May and July 2021.

Methodology: Thirty-five (35) T. guineensis were randomly obtained from local fishers at each station (total n = 70), transported under cooling conditions, and examined for intestinal helminths and morphometric indices using standard parasitological and morphometric techniques. Water physicochemical parameters were assessed using standard hydrobiological methods.

Results: The overall helminth prevalence was 27 (38.5%), with a higher infection rate at Iwofe Jetty, 21 (30%), compared with Bonny Jetty, 6 (8.56%). Female fish showed a slightly higher prevalence, 12 (41.1%), than males, 15 (36.6%). The highest prevalence, 14 (51.86%), occurred in fish weighing 40-65 g, while the lowest, 1 (3.7%), was recorded in fish weighing >89.9 g; however, infection was not significantly related to weight (P > 0.05). By length, prevalence was highest in fish >17 cm, 7 (50%), and lowest in the 13-14.0 cm group, 4 (20%), with no significant difference (P > 0.05). Turbidity at Bonny (192.33 NTU) was significantly higher than at Iwofe (16.53 NTU), while dissolved oxygen concentrations were low at both stations (Iwofe: 3.17 +/- 0.90 mg/L; Bonny: 3.23 +/- 1.02 mg/L). Other water parameters, such as salinity and total dissolved solids, were within acceptable ranges.

Conclusion: Degraded water quality, particularly high turbidity and low dissolved oxygen at Bonny, likely contributed to lower helminth prevalence and fish weight, whereas relatively stable conditions at Iwofe favoured higher parasite prevalence. The presence of intestinal helminths raises public health and food safety concerns, emphasising the need for One Health-based environmental and public health management strategies.