Studies on Some Parasitic Diseases in Oreochromis niloticus Fish Hatchery with Emphasis to Life Stages

This study was conducted on 210 Oreochromis niloticus (O. niloticus) of different life stages including (100 fry, 100 fingerlings and 10 broodstocks) obtained from a private fish hatchery at Kafer El-Sheikh Governorate, Egypt; during August 2014. The hatchery complains 30% mortality among fry and fingerlings while no mortalities was recorded among broodstocks. Parasitological examination revealed heavy infestation with Triochodina species (sp.) in all examined life stages at a prevalence rate 100%. In addition, Gyrodactylus sp. was recorded in gills of fry, fingerlings and broodstocks at a rate of 5, 12, and 10 %, respectively. Kidneys and gills of all examined life stages showed heavy infestations with Myxosporean sp., with 100 % prevalence rate. Haemogregarina sp. was described in the blood of fingerlings and gill tissues of broodstocks. Additionally, Encysted metacerceria was observed in gills of broodstocks. The recovered parasites were demonstrated hisopathologically in the gill and kidney tissues of the examined fish. The histopathological examination revealed that the infested gills exhibited serious lesions such as hyperplasia and hypertrophy of the lining epithelial cells of the gill filaments, fusion and necrosis of secondary lamellae and vasodilatation. The lining epithelium of the renal tubules showed degenerative and necrotic changes with the presence of various developmental stages of myxosporidia. In conclusion, fry and fingerlings exhibited high mortalities, while no mortality was recorded among broodstocks, regardless the intensity of infestation and severity of pathological alterations which was intense in broodstocks

Modulation of genotoxicity and endocrine disruptive effects of malathion by dietary honeybee pollen and propolis in Nile tilapia (Oreochromis niloticus)

The present study aimed at verifying the usefulness of dietary 2.5% bee-pollen (BP) or propolis (PROP) to overcome the genotoxic and endocrine disruptive effects of malathion polluted water in Oreochromis niloticus (O. niloticus). The acute toxicity test was conducted in O. niloticus in various concentrations (0–8 ppm); mortality rate was assessed daily for 96 h. The 96 h-LC50 was 5 ppm and therefore 1/5 of the median lethal concentration (1 ppm) was used for chronic toxicity assessment. In experiment (1), fish (n = 8/group) were kept on a diet (BP/PROP or without additive (control)) and exposed daily to malathion in water at concentration of 5 ppm for 96 h “acute toxicity experiment”. Protective efficiency against the malathion was verified through chromosomal aberrations (CA), micronucleus (MN) and DNA-fragmentation assessment. Survival rate in control, BP and PROP groups was 37.5%, 50.0% and 100.0%, respectively. Fish in BP and PROP groups showed a significant (P < 0.05) reduction in the frequency of CA (57.14% and 40.66%), MN (53.13% and 40.63%) and DNA-fragmentation (53.08% and 30.00%). In experiment (2), fish (10 males and 5 females/group) were kept on a diet with/without BP for 21 days before malathion-exposure in water at concentration of 0 ppm (control) or 1 ppm (Exposed) for further 10 days “chronic toxicity experiment”. BP significantly (P < 0.05) reduced CA (86.33%), MN (82.22%) and DNA-fragmentation (93.11%), prolonged the sperm motility when exposed to 0.01 ppm of pollutant in vitro and increased the estradiol level in females comparing to control. In conclusion, BP can be used as a feed additive for fish prone to be raised in integrated fish farms or cage culture due to its potency to chemo-protect against genotoxicity and sperm-teratogenicity persuaded by malathion-exposure

Antiparasitic and Antibacterial Functionality of Essential Oils : An Alternative Approach for Sustainable Aquaculture

Using synthetic antibiotics/chemicals for infectious bacterial pathogens and parasitic disease control causes beneficial microbial killing, produces multi-drug resistant pathogens, and residual antibiotic impacts in humans are the major threats to aquaculture sustainability. Applications of herbal products to combat microbial and parasitic diseases are considered as alternative approaches for sustainable aquaculture. Essential oils (EOs) are the secondary metabolites of medicinal plants that possess bioactive compounds like terpens, terpenoids, phenylpropenes, and isothiocyanates with synergistic relationship among these compounds. The hydrophobic compounds of EOs can penetrate the bacterial and parasitic cells and cause cell deformities and organelles dysfunctions. Dietary supplementation of EOs also modulate growth, immunity, and infectious disease resistance in aquatic organisms. Published research reports also demonstrated EOs effectiveness against Ichthyophthirius multifiliis, Gyrodactylus sp., Euclinostomum heterostomum, and other parasites both in vivo and in vitro. Moreover, different infectious fish pathogenic bacteria like Aeromonas salmonicida, Vibrio harveyi, and Streptococcus agalactiae destruction was confirmed by plant originated EOs. However, no research was conducted to confirm the mechanism of action or pathway identification of EOs to combat aquatic parasites and disease-causing microbes. This review aims to explore the effectiveness of EOs against fish parasites and pathogenic bacteria as an environment-friendly phytotherapeutic in the aquaculture industry. Moreover, research gaps and future approaches to use EOs for sustainable aquaculture practice are also postulated