Elsevier

Aquaculture

Volumes 376–379, 15 February 2013, Pages 146-150
Aquaculture

Studies on ulcerative disease caused by Aeromonas caviae-like bacterium in Indian catfish, Clarias batrachus (Linn)

https://doi.org/10.1016/j.aquaculture.2012.11.015Get rights and content

Abstract

Clarias batrachus (Linn) is a species of catfish of the family claridae. A survey was carried out for a period of one year from May 2008 to June 2009 to study the prevalence of bacterial ulcerative disease in C. batrachus, reared in a farm located at Walajapet, Vellore Dist., Tamil Nadu, India. To reproduce the infection in healthy catfish, organs such as liver, spleen and tissue were used to prepare the inoculum in NTE buffer. The inoculum was injected into healthy fingerlings through intramuscular injection and immersion challenge. The tissue supernatant from infected catfish was screened for isolation and identification of the causative organism responsible for ulcerative syndrome in catfish. Based on biological, biochemical, morphological and physiological characters the isolate isolated from infected catfish was tentatively identified as Aeromonas caviae-like bacterium. It was further confirmed by the analysis of 16S rRNA gene of A. caviae using PCR.

Highlights

► Study the prevalence of bacterial ulcerative disease in Clarias batrachus. ► Identification, causative organism for ulcerative syndrome in catfish. ► Confirmation of Aeromonas caviae by PCR.

Introduction

Indian walking catfish, Clarias batrachus (Linn), is an economically important fish species in south and south-east Asian countries, including India, because it is suitable for monoculture or polyculture with other catfish species. It is euryhaline across its native range, inhabiting fresh and brackish water as well as muddy marshes (Sen, 1985). Infectious diseases caused by viruses and bacteria are responsible for substantial financial loss to catfish farmers worldwide. Channel catfish virus (CCV) is an important fish virus causing economic losses in channel catfish Ictalurus punctatus. CCV is a cytopathic herpes virus that can cause an acute, hemorrhagic and lethal disease in the channel catfish (Fijan, 1968). This virus also causes an acute hemorrhagic disease in channel catfish fry and fingerlings (Buck, 1990, Plumb, 1977). Crumlish et al. (2003) challenged hybrid catfish (Clarias gariepinus × C. batrachus) with Aeromonas hydrophila under stressful conditions and reported high mortality of fish in high temperature stress. Chattopadhyay et al. (1992) isolated fifteen strains of A. hydrophila from three species of fish including C. batrachus with typical ulcers on the surface of the body. In the present study, high mortality of young C. batrachus with clinical sign of ulcers on the body surface was observed in a hatchery and grow out ponds. An attempt was made to isolate and identify the causative organism responsible for high mortality of catfish fry. Experimental pathogenicity was conducted to reproduce the infection in normal fish using the bacterial isolate isolated from naturally infected fish. Chauhan (2012) carried out a study on certain fungal diseases in culturable and non-culturable species of fishes of Upper Lake, Bhopal. Achlya and Saprolegnia were found to be the most virulent genera. Out of 2066 fishes examined, the most affected species was C. batrachus (24.6%). Sarkar and Rashid (2012) investigated pathogenicity of the bacterial isolate Aeromonas hydrophilla to catfishes, carps and perch. They reported a mortality of 60–100% in all the six species of catfishes studied at a water temperature of 30 °C.

Section snippets

Collection and maintenance of naturally infected fish

The young ones (fingerlings) of Indian catfish (C. batrachus) weighing approximately 3–5 g with clinical signs of ulcerative lesions having a depth of approximately 2 mm on the body surface and base of the fins were collected from a farm located at Walajapet, Tamil Nadu and transported within half an hour at 28 °C in live condition to the laboratory in a container with continuous aeration. In the laboratory, the infected animals were maintained in 100-l aquarium tanks containing ground spring

Results

The physicochemical characteristics of pond water were determined. Temperature, pH, and dissolved oxygen ranged from 26 to 31 °C, 7.2 to 7.4 and 4.6 to 6.0 mg/l, respectively, during the collection of infected fish. A high temperature of 31 °C was recorded during summer. Mortality of fish due to infection reached 95–97% within 3–5 days after the appearance of ulcer on the surface of infected fish. The clinical signs of infected fish include ulcerative lesions on the body surface, bases of the fins

Discussion

C. batrachus is considered as a potential aquaculture species in the Indian subcontinent. The population of catfish has been affected by many factors including diseases caused by viral and bacterial pathogens, even though it is a hardy species. High mortality of young C. batrachus was observed in nursery and grow-out ponds located in Tamil Nadu and Andhra Pradesh. Among the bacterial pathogens, motile Aeromonas caused high mortality in catfish (Lewis and Plumb, 1979, Meyer, 1975) and induced

Acknowledgments

The authors thank the management of C. Abdul Hakeem College for providing the facilities to carry out this work. This work was funded by the University Grants Commission, Government of India, New Delhi.

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