ISOLATION AND IDENTIFICATION OF PATHOGENIC FUNGI SPECIES FROM TILAPIA FISH (Tilapia zillii) SOLD IN SELECTED AREAS OF NIGER STATE

Abstract

Isolation and identification of pathogenic fungi species from Tilapia fish (Tilapia zilli) sold in selected areas of Niger State was investigated. The fish were obtained from Tagwai dam and Agaie/Lapai dam as points of catch and there nearby supply markets as points of sale, between the months of February - May 2017. Forty (40) fishes were collected, Ten (10) from each point. The mean total length (TL) and body weight of fish (n=40) was 25.35 cm and 182± g respectively. Fungi were isolated from three different sites on each of the fish (the gills, the mouth and the head). Sterile swabs were used to pick samples from the fish parts and were inoculated on to Potato Dextrose Agar (PDA). The inoculated plates were incubated for 5 - 7 days at 28 ± 2⁰C. Pure cultures were made onto Sabouraud’s Dextrose Agar (SDA) plates. Eleven different fungi species were isolated, which occurred two hundred and ten (210) times. The percentage occurrence of each isolate showed that Aspergillus niger had the highest occurrence of 32 (15.23%), Aspergillus flavus 27 (12.85%), Aspergillus fumigatus 21 (10.00%), Penicillium citrinum 17 (8.09%), Penicillium expansum 22 (10.47%), Mucor sp 21 (10.00%), Fusarium sp (8. 57%), Rhizopus sp 21(10.00%), Saprolegnia sp 16 (7.61%), Ichthyophonous sp 8 (3.80%) and Blastomyces sp 7(3.33%). Out of the two hundred and ten(210) fungal isolates obtained, based on the different sampled points, it showed that 91 (43.33%) were isolates from the two points of catch and 119 (56.66%) fungal isolates were from the two points of sale. The fungal isolates from the gills 87 (41.42%), from the mouth 66 (31.42%) and 57 (27.14%) from the head showed a significantly (p≤ 0.05) higher infection in the gills and mouth as compared to the head from the statistical analysis. The high infection rates of the fish sampled are indication of the poor hygienic awareness by this fish handlers.This research showed that most of the fungi isolated are those associated with causing infection in fishes of freshwater, especially T. zilli and that the fungal load of each fish increases from the point of catch to the point of sale, due to the way and manner of handling. The Proper means of handling fish should the employed in order to control the fungal load.