Seasonal Prevalence and Host-Related Patterns of Neoechinorhynchus iraqensis Infection in Planiliza abu and Silurus triostegus from Al-Gharraf River, Wasit Province, Iraq

Abstract

The present study aimed to determine the seasonal prevalence and mean intensity of the acanthocephalan parasite Neoechinorhynchus iraqensis of two freshwater fish species Planiliza abu and Silurus triostegus from Al-Gharraf River, Wasit Province, Iraq. Fish were sampled monthly from January to December 2025 from three fixed stations along the river. In total, 720 fish, consisting of 360 P. abu and 360 S. triostegus were examined. The parasites were recovered from the intestine and relaxed in chilled distilled water, fixed in 70% ethanol, stained with Semichon's aceto-carmine, cleared, mounted and identified by reference to the standard morphological characters. Overall prevalence was 19.17% (138/720). Infection was significantly higher in P. abu (24.72%; 89/360) than in S. triostegus (13.61%; 49/360) (chi-square = 14.34, df = 1, p < 0.001). The prevalence was highest in summer, lowest in winter, and higher in spring. P. abu had the highest prevalence in June (53.33%) while S. triostegus had the highest prevalence in the month of June-July (30.00%). The monthly prevalence of P. abu and S. triostegus were strongly and positively correlated with water temperature (r = 0.900, r = 0.883, respectively and p< 0.001 for both). The results showed that host feeding ecology and the changes of thermal conditions during the seasons could be important factors in the transmission of N. iraqensis in the Al-Gharraf River system. The study gives new epidemiological data for Iraqi freshwater fish parasitology and gives a support to the integrated monitoring of fish parasites, fish ecology and environmental variables.