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Fungal Infection in Freshwater Fishes of Mymensingh Bangladesh

U. A. ZAHURA
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. B. R. CHOWDHURY
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

M. A. R. FARUK
Department of Aquaculture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh

Abstract/ Executive Summary:

Fungal infection in the cultured and wild freshwater fishes in some selected water bodies of Mymensingh area in Bangladesh was investigated during November 2000 to March 2001. A total of 16 culture ponds and 10 wild water bodies (ditches) were selected for this study. Ten fishes from each pond and wild were randomly sampled monthly to examine the incidence of fungal infection. Barbodes gonionotus, Cirrhinus cirrhosus and Pangasius hypophthalamus among the cultured fishes, while Channa punctatus, Nandus nandus, Puntius ticto and Anabas testudineus among the wild were the most affected fish species. Clinically, cotton wool type lesions on the fish body surface, ulceration and erosion of skin and muscles were observed. Mycotic granuloma, presence of fungal hyphae, haemorrhages and cell necrosis were the major histopathological findings of the affected tissues due to Aphanomyces sp. infection. In total, 19 fungal isolates were recovered belonging to the genera of Aphanomyces, Saprolegnia and Achlya. Only Aphanomyces invadans could be identified up to species level.

Keywords: Fungal infection, Freshwater fishes, Bangladesh

Location: Mymensingh district

Start Date: 00-11-2000

End Date: 00-03-2001

Program Area: Animal Health and Management

Commodity: Aquatic animal

Objectives:

To isolate and identify the fungi for cultured and wild fishes in Mymensingh area of Bangladesh.

Methodology:

Diseased fishes were obtained from the selected sites of Mymensingh area around Bangladesh Agricultural University campus. In each sampling, 10 fishes from farmer’s pond and 10 from wild were sampled randomly during November 2000 to March 2001. The clinical signs of fishes were recorded on the spot and immediately brought to the laboratory. The infecting fungi were then isolated and infected tissues were fixed in 10% neutral buffered formalin for histopathological examination. Prevalence of infection was calculated. Isolates were obtained on to a petridish by inoculating samples (approximately 0.5 cm³) of infected fish muscle taken either from the lesions, beneath the lesion or mycelium fragments into petridish containing Glucose Peptone-Penicillin Oxolinic (GPPen Ox) broth. The petridish was left for 10 h at 25°C until the appearance of fungi from the muscle block. The hyphal strands were then cut out using aseptic technique and transferred to a petridish of GP-pen strep agar. In this way, bacterial growth was inhibited and fungus was able to grow free of bacterial contamination. An agar block containing fungal hyphae from the edge of the colony was then placed upside down on a petridish of GP- agar and repeatedly sub cultured until an axenic stock was obtained. Sporulation and identification of fungi: An agar plug (3-4 mm in diameter), cut from an actively growing edge of a colony was placed on to 40 ml of Glucose Peptone-Yeast (GPY) broth incubated for 4 days at 20⁰C. The mycelial mats were then passed through 5 petridishes containing autoclaved pond water (APW) and left overnight at 20°C in APW to induce sporulation. The incubated petridishes were examined directly under compound microscope at magnification ´10 to identify the distinguishing characters of isolated fungi. The isolated fungi were identified and characterized according to their asexual characteristics. Fungal isolates were maintained in 200 ml GP broth in glass flasks at 10°C. Histopathological study: Muscle tissues of affected fish were collected for histopathological examination after taking sample for fungal isolation. Tissues having lesion and tissues adjacent to the lesions were carefully taken with a fine scalpel and forceps immediately after killing the fish. Tissue samples were fixed in 10% buffered formalin solution, embedded in paraffin and sectioned at 5μm. The sections were stained with haematoxylin and eosin (H & E).

Source of Information: Indian J. Fish., 51(1) : 61-68, Jan.-Mar., 2004

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In the present study, Saprolegnia spp. and Achlya spp. were successfully recovered for the first time in Bangladesh. These isolates could not be identified up to species level. There is need for further work in this line to identify these fungal isolates.

Knowledge Management: Journal