Isolates of the fish parasitic copepod Lernaea from four different freshwater fishes viz., catla (Catla catla), guppy (Poecilia reticulata), platy (Xiphophorus naculatus) and gold fish (Carassius auratus) were selected for the study. The isolates had considerably differing anchor shapes and were likely to be grouped as different species. Partial nucleotide sequences of the 18S and 28S rDNA regions of the Lernaea isolates were determined. Phylogenetic trees generated by the neighbour joining method revealed that the Lernaea isolates examined in this study were of similar genotype and were identified to be Lernaea cyprinacea.

Aims: Aeromonas hydrophila is a zoonotic pathogen displaying resistance to multiple antibiotics. Here, we aim to develop a candidate biocontrol agent against A. hydrophila. Methods and Results: In this study, we isolated and characterized the phage vB-AhyM-AP1 from sewage. It showed lytic activity against A. hydrophila strains. One-step growth curve revealed that the latent period lasted for 40 min. The burst size of one lytic cycle was 1413 PFU per infected cell. Temperature stability studies showed that the phage vB-AhyM-AP1 was active over temperatures ranging from 4 to 45°C for 1 h. pH stability studies indicated that the phage remained active within a pH range of 5-10 after 24 h of incubation. Stability tests in salt solutions showed that the phage was stable at salinities ranging from 0Á1 to 2%. The phage also showed stabilities in organic solvents when incubated for 10 min. The Illumina Hiseq sequencing of its genome indicated that the phage vB-AhyM-AP1was a jumbo phage with a genome size of 2, 54 490 bp and GC content of 40Á3%. The phylogenetic analysis of the terminase large subunit and major capsid protein indicated that the phage closely clustered with other Tevenvirinae phages. The genome encoded 455 ORFs and 22 tRNAs. The phage resulted in a reduction of 0Á8 log units of viable A. hydrophila cells in biofilms grown on PVC coupons maintained in a low nutrient medium for 10 days. Conclusions: The phage showed lytic activity against planktonic and biofilm cells of A. hydrophila. Genome-based prediction showed it to be a strictly lytic phage without any virulence or antibiotic resistance genes indicating safety for environmental and clinical applications. Significance and Impact of the Study: The multidrug-resistant strains of A. hydrophila pose a significant health risk to both cultured fishes and consumers leaving few options for treatment. Phage vB-AhyM-AP1 may be used as a candidate biocontrol agent against A. hydrophila strains.

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Anchor worm (Lernaea spp.) infestation is one of the major parasitic diseases affecting carp culture all over the world, particularly in the Indian subcontinent resulting in huge economic losses. The present study evaluated the loss in terms of mortality and growth reduction in Catla catla fingerlings under experimental infection of Lernaea sp. In the experimentally infected tanks, mortality of catla fingerlings ranged from 50-100% as compared to no mortality in control tanks. Furthermore, fish that survived in the Lernaea infected tanks showed an average weight loss of 23.65%.