Impact of Parasitic Diseases on Fishes of North West Himalayan Streams

Pathological disorders caused due to metazoan parasitic infestation were studied in the hill stream fishes of northwest Himalayan region. Host specificity was found to be one of the fundamental features of metazoan parasites which belonged to the class Cestoda, Nematoda, Trematoda and phylum Acanthocephala. The study indicates that a successful co-evolution of the host and its parasite has caused the adaptation of the later by developing evading mechanisms in order to avoid extinction. Besides this it was also observed that some parasites have even understood to benefit from the well developed antiparasitic armament in fish intestinal epithelia. Thus, parasites are exploiting the antiparasitic response mechanism of the host to optimize, host finding, invasion and survival in the host. Such interaction between host and parasites are considered phylogenetically old. Some monogeneans, cestodes, digeneans and acanthocephalans were found to resist pronounced cellular and host reactions which even improved the attachment of parasite into the host predilection site. Scanning Electron Microscopy and hitstopathological examination was conducted on parasites recovered from fishes in order to understand the host parasite interaction and the damage inflicted by parasite on hill stream fish species. key words: Host-parasite interaction, Acanthocephala, Cestode, Nematode, Trematode, North-West Himalaya, SEM.