EFFECT OF PARASITE INFESTATION ON THE BIOCHEMICAL AND HAEMATOLOGICAL CHARACTERISTICS OF SOME CLARIID (SILIRUFORMES) SPECIES OF THE ANAMBRA RIVER SYSTEM OF NIGERIA
A study based on monthly sampling of catches in Anambra river system (Otuocha station) was carried out between May 2013 and April 2014 to investigate the parasitofauna of wild clariid catfishes with reference to their prevalence, mean intensity and abundance; and also to ascertain the impact of these parasites on the physiology of its fish hosts. A total of 360 fish hosts, comprising of Clarias gariepinus (231) and Clarias anguilaris (129), were examined for parasites. Blood samples were collected from the caudal peduncle for haematological and biochemical enzymes assay using standard procedures. Six parasite species including two protozoans (Trichodina acuta and Epistylis sp.), two cestodes (Polyonchobothrium clarias and Monobothroides woodlandi) and two nematodes (Procamallanus laeviconchus and Rhabdocona congolensis) were recovered. The overall parasite prevalence is 41.1%, with protozoan parasites having the highest prevalence (25.5%), cestode (15.0%). Whereas nematode has the least parasite prevalent, infecting only 4.72% of the fish hosts. The relatively high overall parasite prevalence may be attributed to the relatively high level of domestic effluent into the river. Analysis of prevalence of parasitic infection of fish species by body weight and total length showed that parasite loads increased with increase in body weight and total length fish hosts. The study revealed that male fishes accumulate more parasites (P<0.05) than the female fishes. Monthly/seasonal patterns of parasite occurrence varied from one parasite to another. Whereas some parasites were found throughout the year, others were highly pronounced either in the rainy season or in the dry months. The influenrce of parasite prevalence on the condition factor (K) and hepatosomatic index (HSI) were highly significant (P<0.05). Whereas, condition factor showed negative correlations with increase in parasite intensity, HSI showed positive correlation with increase in parasite intensity. The study recorded a significant decrease in the mean values of red blood cell count (RBC), Haemoglobin concentration (Hb) and packed cell volume (PCV) (P<0.05) and significant increase in the mean values of white blood count (WBC) of the infected fishes when compared to the uninfected ones (P<0.05). Moreso, significant increase were observed in the mean values of aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), urea and creatinine of the infected fishes when compared to the uninfected fishes (P<0.05). The haematological and biochemical alterations observed in the infected fishes reflect anemia and tissue damages caused by parasites invasion.