Background

Fish serves as an important part of human and animal diet. Fish is an important source of energy, protein and many other essential nutrients thus making up to about 17% of the world’s population intake of animal protein (Abila, 2003). In the same vein, fish oil contains omega-3-essential fatty acids important for the proper functioning of the brain, heart and immune system (Hohn, 1999). However fishes, both cultured and wild, usually carry zoonotic parasites such D. latum. Hence, fresh water fish can be an important source of parasitic infection to man and fish-eating mammals (Mohammed, 1996). Many reports have been documented on zoonotic fish parasites (Aloo, 2002; Gichohi, 2010; Kamundia, 2011). Additionally, the World Health Organization (1995) estimated that the number of people who have been infected is over eighteen million (18 million). The essence of this study is to provide information regarding the current status of fish parasite in Igbokoda River in order to enhance proper management and control fish parasite thereby preventing zoonotic fish diseases.

1 Results

Out of the two hundred (200) fishes examined, 74 (37%) were males and 126 (84%) were females. Of these, a total of 84 (42%) were infected in which prevalence of parasite in male and female were 36 (48.65%) and 48 (38.10%) respectively (Table 1). Table 2 shows the frequency distribution of parasites and the percentage. D. latum has the highest parasite prevalence of 32 (38%), followed by Camallanus 20 (23.80%), G. spinigerum 14 (16.66) Procamallanus 10 (11.90%) and Clinostomum with the lowest prevalence of 8 (9.52%). Table 3 presents the parasite prevalence with respect to weight of O. niloticus from Igbokoda River. O. niloticus having the lowest weight of < 50g had the lowest parasite prevalence of 16 (24.24%) while those having the highest weight of > 300g had the highest parasite prevalence of 100%.

2 Discussion

There is a high prevalence of infection, 84 (42%) in this study area. This means that undercooked fish from this Igbokoda River is capable of transmitting infections to consumers. This prevalence is high compared to the 16.0% reported from Asa River and its impoundment in Ilorin (Obano et al., 2011). The parasites recovered were D. latum, Camallanus spp, Procamallanus, Gnathostoma spinigerum, and Clinostomum. It has been reported that helminthes are generally found in all fresh water fishes, with their prevalence and intensity dependent on factors such as parasite species and their biology, host and its feeding habits, physical factors, hygiene of water body and availability of intermediate host (Martinez et al., 2008). In this study, D. latum has the highest prevalence. However, previous reports on O. niloticus revealed that Acanthocephalan have highest parasitic prevalence according to Yamba et al. (2016). Additionally, G. spinigerum is of zoonotic significance as man can be infected by eating inadequately cooked fish causing eosinophilic meningitis and deep cutaneous leisions, particularly around the digits and on the breast (Soulsby, 1982). Prevalence of Clinostomum sp. (9.52%) was low compared to that reported at Burkina-faso (Yamba et al., 2016). This low infection rate can be attributed to sanitary condition and location. The percentage parasitic infection was higher in males (48.65%) than females (38.10%). This disagree with the findings of Emere (2000) and, Emere and Egbe (2006) who reported that due to the physiological state of the females, most gravid females could have reduce resistance to infection by parasite. However, the observation agrees with the findings of Mhaisen et al. (2000) and Oniye et al. (2004) who reported more parasite prevalence in male than in female and this may be due to certain ecological factors emanating probably from feeding differences between males and females. The prevalence of parasite infection increases with increase in length and weight of the fish (Ugwuzor, 1985). In relation to the size (length and weight), it was observed that percentage infection increases with increasing size. Similar observation were reported by Ayanda (2009) and Olurin and Samorin (2006) that the longer and heavier the fish, the greater the susceptibility to parasite infection. This observation could be attributed to the fact that bigger fishes have larger surface area for infection to multiply in numbers than in smaller ones and also as a result of changes in diet from phytoplankton and zooplankton to insects, larvae, snails, worms and crustaceans for food as smaller fishes grow into bigger ones (Obano et al., 2011).

3 Materials and Methods

3.1 Study area

The study was conducted in Igbokoda which is situated in Ilaje-Ese Odo, Ondo State, Nigeria. It is located between latitude 6^o21’N and longitude 4^o48’E. Igbokoda has a prevailing ambient temperature of 25^oC and relative humidity of 89%. The two distinct seasons in the area are wet or raining and dry season. The wet season last from April to October and it is characterized by heavy rain with occasional floating of bank of river. The dry season lasts from November to March characterized by cool, dry wind harmattan in December and January and high temperature in February and March. The major occupation of the inhabitant are fishing and trading.

3.2 Sample collection

Nine (9) Tilapia (O. niloticus) used in this study was purchased from local fish vendors at Igbokoda river, Igbokoda, ondo state. The fish were transported in a plastic bucket containing clean water to Biology Department Laboratory. The length and weight of the fish were measured using meter rule and weighing balance respectively.

3.3 Identification

Each fish was dissected and the stomach lining and intestine of each fish was removed and opened and scraped and put into a test tube using an applicator stick, little portion of normal saline was added to the test tube containing the sample and homogenized. Another portion of normal saline was added to it until it reached two third of the test tube with the aid of applicator stick and homogenized, normal saline was added again till it form a meniscus and live to stand for 20 minutes to allow the parasite egg float. After 20 minutes, the cover slip was gently placed on a clean glass slide and stained with hematoxylin stain and view under X10 eye piece and X40 objective lens under the microscope (Paperna, 1996).

3.4 Statistical analysis

Data obtained were analyzed using SPSS version 17. Comparism of prevalence rate base on weight, sex, and Alength were determined using Chi-square analysis. P < 0.05 was regarded as statistically significant.

Authors’ contributions

Awosolu, O.B. conceived and designed the project and as well put up the manuscript; Simon-Oke proofread while Oyelere, A.A did the field and laboratory aspect of the project. All authors read and approved the final manuscript.

Acknowledgements

We sincerely appreciate the fishermen and women who assisted us at Igbokoda River and Market.

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