PHENOTYPIC AND MOLECULAR BASED IDENTIFICATION OF MAJOR PARASITIC DISEASES IN CULTURED FISHES
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Date
2022
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KARNATAKA VETERINARY, ANIMAL AND FISHERIES SCIENCES UNIVERSITY, BIDAR
Abstract
Aquaculture is the rapid growing food producing sector in India. Disease is one of
the major limiting factors responsible for huge economic loss in aquaculture.
Aquaculture is prone to various diseases from infectious agents like Virus, Bacteria and
Parasites. The information available on the parasites is scant in India hence this study
was undertaken by aiming for parasitic disease in aquaculture environments. A total 120
samples were screened for 7 major groups of parasites such as, Protozoans, Myxozoans,
Microsporidians, Trematodes, Nematodes, Cestodes and Crustacean parasites. The
identification was done on the basis of morphological level by using brightfield
microscope and molecular level by following standard molecular diagnostic techniques.
Out of 120 samples, 10 fishes were found to be infected with Lerneae, 4 fishes with
Argulus, 4 fishes with Ichthyophthirius multifiliis, 3 fishes with Dactylogyrus, 1 fish with
Camallanus and 1 fish with Tetrahymena. The prevalence of infection was found to be
8.33%, 3.33%. 3.33%, 2.55%, 0.83% and 0.83% in Lernaea, Argulus, Ichthyophthirius
multifiliis, Dactylogyrus, Tetrahymena and Camallanus respectively. Identification of
the parasites to their species level by using the microscopic method was highly difficult
due to its high degree of morphological intraspecific diversity and interspecific
similarities and there is a high risk of misidentification as different species. Therefore,
in this study, molecular technique i.e polymerase chain reaction was employed to
identify the parasites to their species level. The phylogenetic analysis revealed that
Lernaea showed maximum homogeneity with L. cyprinaceae from Russia, Argulus with
A. japonicus from Japan, Dactylogyrus with D. inexpectatus from USA, I. multifiliis with
isolates from Canada, China and Philippines, Tetrahymena with T. pigmentosa from
USA and Camallanus with C. cotti from China.