Expression of immune-related genes in parasite-infected Tilapia nilotica (Oreochromis niloticus) from Egypt and molecular characterization of the parasites

Aquaculture is one of the world's most rapidly developing animal production sectors. Tilapia nilotica (Oreochromis niloticus) is the most popular fish known for quality and price. In the present study sixty fish samples of Tilapia nilotica (Oreochromis niloticus) of about 16-22cm length were collected from Tilapia breeding farms and twenty Nile tilapia fish samples were collected for tissue sampling rom each farm. Fish samples were thoroughly investigated for external parasites by visual inspection microscopically through fixed wet smears from the gills and skin. The DNA was extracted from the fish and 17 different parasite species were amplified for partial 18S rDNA and entire ITS1 regions using three sets of commonly recommended primers. The amplicons were confirmed through sequencing. The results exhibited that Trichodina sp. and Gyrodactylus hildae in gills, Cichlidogyrus aegypticus on skin while Acanthosentis sp. was found in the intestine of infected tilapia within Fuwa City, Kafr El sheikh Governorate. The parasites found in Mataria City, Dakahlia Governorate were Cichidogyrus halli on the gills, Zschokkella candia on muscles, and Clinostomum tilapiae in the intestine. The parasites Dactylogyrus sp. and Myxobolus fomenai were recovered from the skin and muscles, respectively, of infected Tilapia from King Mariout, Borg El-Arab City, Alexandria Governorate. Moreover, the expression level of IL-1β gene was up-regulated in muscle, skin, gills and intestine tissues of fish infected with parasites such as Z. candia, C. halli, C. tilapiae, Dactylogyrus sp., M. fomenai, C. aegypticus, Trichodina sp., G. hildae, and Acanthocentis. The similar up-regulation tissues expression trends of TNF-α and IFN-γ genes were found in fish infested with these parasites. The present study exlored molecular characterization of different parasites isolated in different locations of Egypt in Tilapia nilotica (Oreochromis niloticus) and up-regulation of the inflammatory response genes such as IL-1β, TNF-α and IFN-γ is an indicator of the sever inflammation due to these parasitic infestation in fish.