Cultured Nile Tilapia Oreochromis Niloticus Research Articles

Feral parasites: African monogeneans recorded in ferine Nile tilapia in Oaxaca, Mexico

Monogenean parasites associated to cultured Nile tilapia Oreochromis niloticus have been co-introduced globally. In this survey, we assessed how prevalent these ectoparasites are in both rustic fish farms in Oaxaca, Mexico and in feral tilapia in the vicinity of these farms. We provide molecular data (D2 + D3 domains of the large subunit of the 28S rDNA gene and the Internal Transcribed Spacers, ITS1 + 5.8S + ITS2 rDNA) to confirm the taxonomic identity of the parasites and —eventually— to trace their anthropogenic introductions and assess their ecological impact. We demonstrate that four African monogeneans infect farmed and feral tilapia in Oaxaca. The dactylogyrids Cichlidogyrus sclerosus and C. tilapiae were recorded on farmed tilapia, and C. sclerosus on feral fish in the vicinity of farms. The gyrodactylids Gyrodactylus cichlidarum and G. yacatli infected feral tilapia, both near and further away from farms. The present survey suggests that the deficient biosafety protocols in rustic tilapia farms enable parasites to escape from fish farms and potentially spill-over to native fishes. Considering monogeneans associated to tilapia are known pathogens and very successful invaders, an effort should be made to assess their impact on native fishes — particularly in very biodiverse regions, like Oaxaca.

Prevalence of parasitic infections on cultured Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) In Bong County, Liberia

This study investigated the prevalence rate, relative abundance and mean intensity of par­asites infecting cultured Nile tilapia Oreochromis niloticus L. in three fish farms, Gbarnga, Warta and CARI in Bong County, Liberia. Organs from thirty fish samples were exam­ined from September 2016 to February 2017, along with water quality parameters. Results showed the occurrence of seven parasites including protozoans, monogeneans, digeneans, cestodes, hirudineans, nematodes and crustaceans which were organ specific in terms of infection. The prevalence of the parasites varied seasonally, with the highest numbers oc­curring in November-January. The low prevalence rate, relative abundance and mean in­tensity of the parasites showed no threat to fish farmers in Liberia. All the water quality parameters were at desirable levels for the culture of the fish except nitrite, which was beyond the threshold for sustainable fish culture. It is therefore concluded that although parasitic infections in the three farms in the Bong County were low, best farm management practices are essential.

Co-infection of Lactococcus garvieae and Tilapia lake virus (TiLV) in Nile tilapia Oreochromis niloticus cultured in India.

Tilapia lake virus (TiLV) and Lactococcus garvieae are 2 major pathogens of cultured Nile tilapia Oreochromis niloticus. In June-July 2018, a disease outbreak was reported in Nile tilapia cultured in brackish water floating cages in Kerala, India. Affected fish died gradually, and cumulative mortality reached ~75% within 1 mo. In the present study, TiLV and L. garvieae were isolated from the infected fish and confirmed. Nucleotide analysis of the partial sequence of segment 3 revealed that the present TiLV isolate showed 100% similarity with TiLV MF574205 and 97.65% similarity with TiLV KU552135 isolated in Israel. The partial 16S rDNA nucleotide sequence of L. garvieae shared 99% similarity with the 16S rDNA nucleotide sequence of L. garvieae isolated from Nile tilapia in Brazil. Eight virulence genes (hly1, hly2, hly3, NADH oxidase, adhPav, LPxTG-1, LPxTG-4, adhC1) were amplified in the present isolate. In the experimental challenge study, the onset of mortality started earlier in fish co-infected with TiLV and L. garvieae (3 d post-infection [dpi]) compared to other groups. Cumulative mortality (90% at 12 dpi) was significantly higher in the co-infected group than in fish infected with TiLV (60% at 12 dpi) and L. garvieae (40% at 12 dpi) alone. This study reveals that synergistic co-infection with TiLV and other bacteria may increase mortality in disease outbreaks. To the best of our knowledge, this is the first reported co-infection of L. garvieae with TiLV associated with mass mortality in Nile tilapia in India.

Eubiotic effect of a dietary potassium diformate (KDF) and probiotic (Lactobacillus acidophilus) on growth, hemato-biochemical indices, antioxidant status and intestinal functional topography of cultured Nile tilapia Oreochromis niloticus fed diet free fishmeal

An 84 days experimental trial was undertaken to examine the influence of potassium diformate (KDF) and Lactobacillus acidophilus and their interaction on growth, biochemical of blood parameters, enzymes of antioxidant response and intestinal topography of Nile tilapia, Oreochromis niloticus, fingerlings fed fishmeal free diets. Six functional diets were formulated to contain two levels of L. acidophilus (0, 1.47 × 107 CFU kg−1), with each level being supplemented with 0, 5 g and 10 g KDF kg−1 diet, respectively. Fingerlings O. niloticus (n = 540; initial weight 4.29 ± 0.06 g) were randomly allocated into six groups (30 fish group−1 in triplicates). The results showed that the best values of growth, feed efficiency and biological parameters were recorded by fish fed diets containing 1.47 × 107 L. acidophilus CFU kg−1 and 10 g kg−1 KDF. Lower pH values in stomach and gut were noted in fish fed diet supplemented with 1.47 × 107 L. acidophilus CFU kg−1 and 10 g kg−1 KDF. Diets supplemented with L. acidophilus, KDF or in combination improved the hemoglobin, red blood cells and white blood cells count with insignificant differences among groups. The activities of serum alanine and aspartate aminotransferase decreased significantly (P < 0.05) by the addition of L. acidophilus and KDF in fish diets. Furthermore, addition of KDF and L. acidophilus significantly (P < 0.05) improved the serum total protein and albumin, but globulin not affected. The lowest value of uric acid was recorded in fish fed 5 g kg−1 KDF without addition of L. acidophilus, while there were no significant (P > 0.05) differences in creatinine content were found among treatments. Diets supplemented with L. acidophilus and/or KDF significantly (P < 0.05) improved phosphorus and calcium content. However, the activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and catalase (CAT) were highest in fish fed diet contained either 5 g or 10 g kg−1 KDF and 1.47 × 107 L. acidophilus CFU kg−1 (D4 and D6). Villi length and width in the middle intestine and number of goblet cell were shown to be promoted in fish fed diets 10 g KDF kg−1 or 10 g kg−1 KDF and 1.47 × 107 L. acidophilus CFU kg−1diet. In conclusion, the administration of a mixture of a probiotic and KDF is beneficial, as it effectively improves the gut morphology and the total antioxidant enzyme activity resulting in an overall enhancement of the fish growth performance.

Prevalence, molecular characterization, virulotyping, and antibiotic resistance of motile aeromonads isolated from Nile tilapia farms at northern Egypt

Objective: This study was aimed to survey Aeromonas spp associated with cultured Nile tilapia Oreochromis niloticus (O. niloticus) showing signs of motile Aeromonas septicemia (MAS) at different fish farms; molecular characterization and identification of test isolates; and to test the isolates for their antimicrobial and virulence activities that contribute to its pathogenesis. Design: Observational study Animals: 280 Nile tilapia Procedures: Clinically diseased 280 Nile tilapia, were collected from different localities at Kafr El-Sheik and Dakahlia governorates. The clinical picture and gross lesions were recorded. Aeromonas spp were isolated and presumptively identified using API20E. The identification was confirmed using PCR. Hemolysin (hylA), lipase, and aerolysin (aerA) virulence genes were detected among isolates obtained from different sampling sites. Besides, antimicrobial activity was reported for the identified A. hydrophila. Results: General septicemic signs were evident on Nile tilapia including, skin hemorrhages and ulcerations, bilateral exophthalmia, congested internal organs with significant mortalities. The prevalence of bacterial infection among naturally diseased Nile tilapia was 79.17, 70, and 58.33 in Kafr El-Sheikh, El- Manzala, and Gamsa fish farms, respectively. The most prevalent bacterial isolates were aeromonads (29.84 %), of all, 65.63 A. hydrophila, 18.75 A. caviae, and 15.63 A. sobria. All isolates were positively amplified using a species-specifying primer to determine A. hydrophila. Virulence genes detection revealed that five A. hydrophila isolates (83.3 %) harbored the aerA gene. Meanwhile, hylA and lipase genes positive isolates were lower reaching 16.7 % for both genes. A. hydrophila was highly sensitive to ciprofloxacin, amikacin, trimethoprim, and chloramphenicol, and MAR index of A. hydrophila isolates was ranged from 0.16-0.42 Conclusion and clinical relevance: Our findings demonstrate that Aeromonas spp are among the bacterial pathogens implicated in summer mortalities in tilapia fish farms in Egypt. Besides, determination of the prevalence, virulence genes, and antibiotic resistance pattern associated with the disease outbreaks is critical data that warrant the development of strategies to proper monitoring and farm management practices.

Prevalence, molecular Cاharacterization, virulotyping, and antibiotic resistance of motile aeromonads isolated from Nile tilapia farms at northern Egypt

Objective: This study was aimed to survey Aeromonas spp associated with cultured Nile tilapia Oreochromis niloticus (O. niloticus) showing signs of motile Aeromonas septicemia (MAS) at different fish farms; molecular characterization and identification of test isolates; and to test the isolates for their antimicrobial and virulence activities that contribute to its pathogenesis. Design: Observational study. Animals: 280 Nile tilapia. Procedures: Clinically diseased 280 Nile tilapia, were collected from different localities at Kafr El-Sheik and Dakahlia governorates. The clinical picture and gross lesions were recorded. Aeromonas spp were isolated and presumptively identified using API20E. The identification was confirmed using PCR. Hemolysin (hylA), lipase, and aerolysin (aerA) virulence genes were detected among isolates obtained from different sampling sites. Besides, antimicrobial activity was reported for the identified A. hydrophila. Results: General septicemic signs were evident on Nile tilapia including, skin hemorrhages and ulcerations, bilateral exophthalmia, congested internal organs with significant mortalities. The prevalence of bacterial infection among naturally diseased Nile tilapia was 79.17, 70, and 58.33 in Kafr El-Sheikh, El- Manzala, and Gamsa fish farms, respectively. The most prevalent bacterial isolates were aeromonads (29.84 %), of all, 65.63 A. hydrophila, 18.75 A. caviae, and 15.63 A. sobria. All isolates were positively amplified using a species-specifying primer to determine A. hydrophila. Virulence genes detection revealed that five A. hydrophila isolates (83.3 %) harbored the aerA gene. Meanwhile, hylA and lipase genes positive isolates were lower reaching 16.7 % for both genes. A. hydrophila was highly sensitive to ciprofloxacin, amikacin, trimethoprim, and chloramphenicol, and MAR index of A. hydrophila isolates was ranged from 0.16-0.42 Conclusion and clinical relevance: Our findings demonstrate that Aeromonas spp are among the bacterial pathogens implicated in summer mortalities in tilapia fish farms in Egypt. Besides, determination of the prevalence, virulence genes, and antibiotic resistance pattern associated with the disease outbreaks is critical data that warrant the development of strategies to proper monitoring and farm management practices.

Mass Mortality in Cultured Nile Tilapia Oreochromis niloticus in Kafr El-Sheikh Province, Egypt Due to Saprolegniosis with Emphasis on Treatment Trials

Mass Mortality in Cultured Nile Tilapia Oreochromis niloticus in Kafr El-Sheikh Province, Egypt Due to Saprolegniosis with Emphasis on Treatment Trials

Prevalence and seasonal variation of ectoparasites in cultured Nile tilapia Oreochromis niloticus in Saudi Arabia.

The prevalence, mean intensity and abundance of ectoparasites (monogeneans and trichodinids) from Nile tilapia Oreochromis niloticus were investigated during different seasons of two consecutive years, from January 2011 to December 2012. A total of 360 O. niloticus was collected from three fish farms located in the central region of Saudi Arabia. Prevalence, mean intensity and mean abundance of monogeneans on fish gills were found to be significantly (p<0.01) higher in farm(C) (81.67, 495.23, 405.84%) than farm (A) (7.5, 81.25, 8.34%) and farm (B) (4.17, 62.5, 5%) respectively. Similarly, the same parameters for trichodinids on gills were found to be significantly (p<0.01) higher in farm (C) (97.5, 97.5, 97.5%), followed by farm (A) (39.17, 234.37, 35.00%) and farm (B) (6.67, 347.92, 30.00%) respectively. The results of monogenean parameter on fish skin were found to be significantly (p<0.01) higher in farm (C) (66.67, 443.68, 294.16) followed by farm (A) (16.67, 124.58, 21.67%) then farm (B) (0.83, 25, 0.83%) respectively. Similar results for trichodinid parameters on the skin were found to be higher (p<0.01) in farm (C) (97.5, 875, 857.5%), then farm (A) (26.67, 399.70, 215.01%) and farm (B) (4.17, 154.17, 12.5%) respectively. These results indicated that water quality and nutritional qualities were the major factors that affecting parasite occurrence, while the effect of temperature, seasonality and stocking density might have a secondary role on ectoparasite occurrence. Further studies should investigate that how the nutritional and water qualities affect the immunity of the fish to resist parasite infection.

Efficiency of using green algae as biological controllers against toxic algal taxa in cultured Nile tilapia Oreochromis niloticus, based on histopathological examinations

The incidence of harmful cyanobacterial blooms in surface waters has increased in frequency and outbreaks have become more severe. This research aimed at studying the effect of a culture of two green algal species as biological control of the growth of toxic blue-green algae. Nile tilapia of an initial mean weight of 55 g fish−1 (SE 5) were used for each of four treatments in triplicate. All algal seedings were done at 4 × 103 cells ml−1. Treatment I (untreated) served as a control, Treatment II was seeded with Microcystis aeruginosa, Treatment III was seeded with green algae Chlorella ellipsoidea and Scenedesmus bijuga, and Treatment IV was seeded with a mixture of M. aeruginosa and C. ellipsoidea and S. bijuga. After 10 days, Treatment IV showed 3.4% viable cell survival, compared to 35% and 55% in Treatments II and III, respectively. Histopathological examination revealed mild degenerative changes and focal necrosis, as well as a depletion of haematopoietic tissues in Treatment IV compared to Treatment II. These findings suggest the efficacy of C. ellipsoidea and S. bijuga in controlling the growth of M. aeruginosa and minimising its side effects on cultured Nile tilapia.

Physiological and microbiological indices as indicators of evaluating dietary fungi degraded date pits as a probiotic for cultured Nile tilapia Oreochromis niloticus fingerling and its effect on fish welfare

The main goal of this study is to explore the potentiality of using blood haemoglobin, plasma glucose, plasma triglycerides, plasma cholesterol, growth rate and intestinal bacterial count as biomarkers to evaluate the dietary supplementation of fungi-degraded date pits (FDDP) as growth promoters as well as probiotic for fingerling Nile tilapia Oreochromis niloticus reared in a recirculating system. Five isoenergetics–isonitrogenous diets containing 0, 0.5, 1.0, 1.5 and 2.0g/100g of fungi Trichoderma reesei-degraded date pits (FDDP), as a replacement for dietary α-cellulose, were used to feed triplicate groups of fish fingerlings (2.0g initial weight), for 9weeks. Tilapia weight gain (4.27g/g), was superior only in fish fed on diets containing 0.5g/100g FDDP, when compared with those fish fed on other diets. Blood haemoglobin was found to be unchanged in fish fed on different percentages of FDDP diets. Plasma glucose was high in fish fed on 0.5% FDDP, the accompanied plasma hypertriglyceridemia, could possibly be due to hepatic neo lipogenesis. Cholesterol levels in fish plasma fed on experimental FDDP diets at all concentrations were highly and significantly decreased which may indicate the attenuated ability for transporting lipid out of liver. Although significant correlation among the physiological indices and the dietary FDDP have been observed, blood haemoglobin, plasma triglycerides and cholesterol are shown as more sensitive indicators followed by plasma glucose and then growth rate. The present study showed a possible potential of using FDDP to lower the bacterial population densities in O. niloticus intestine without affecting the fish weight or health welfare condition, that could be an excellent approach in designing subsequent probiotic researches on FDDP. Oestradiol was measured in all tested diets and was found to increase linearly with FDDP content in diets, which indicates that a FDDP may has phytoestrogenic roll.

Enhanced mortality in Nile tilapia Oreochromis niloticus following coinfections with ichthyophthiriasis and streptococcosis

Ichthyophthirius multifiliis Fouquet (Ich) and Streptococcus iniae are 2 major pathogens of cultured Nile tilapia Oreochromis niloticus (L). Currently there is no information available for the effect of coinfection by Ich and S. iniae on fish. The objective of this study was to determine the effects of parasite load and Ich development size on fish mortality following S. iniae infection. Low mortality (< or =20%) was observed in tilapia exposed to Ich or S. iniae alone. Mortalities increased from 38% in tilapia exposed to Ich at 10,000 theronts fish(-1) to 88% in fish at 20,000 theronts fish(-1) following S. iniae exposure. The median days to death were significantly fewer (7 d) in fish exposed to Ich at 20,000 theronts fish(-1) than fish exposed to 10,000 theronts fish(-1) (10 d). A positive correlation (correlation coefficient = 0.83) was noted between tilapia mortality and size of Ich trophonts at the time of S. iniae challenge. Fish parasitized with well-developed trophonts (Day 4, 2 x 10(7) microm3 in volume) suffered higher mortality (47.5%) than fish (10.0%) infested by young trophonts (Hour 4, 1.3 x 10(4) microm3 in volume) after S. iniae challenge. The results of this study demonstrated that both parasite load and trophont size increased susceptibility and mortality of tilapia to S. iniae infection.

A Piscirickettsiosis‐like Syndrome in Cultured Nile Tilapia in Latin America with Francisella spp. as the Pathogenic Agent

In 2004, cultured Nile tilapia Oreochromis niloticus in several Latin America farms began to succumb to a disease similar to the piscirickettsiosis-like syndrome previously reported in tilapia in Taiwan and the United States. Mortality increased during 2005; reductions in tilapia biomass ranged from 5% to 80% in individual ponds and averaged 50% overall. All ages of fish have been involved. Clinical signs include lethargy, loss of appetite, petechia, exophthalmia, and abnormal swimming behavior. Gross lesions have included splenomegaly, renomegaly, and numerous white nodules observed in the spleen, kidney, testes, heart, ovaries, and occasionally the liver. A previously unreported black granulomatous lesion was reported in up to 30% of the fillets. Histologically, granulomatous infiltrates were observed in the kidney, spleen, liver, testes, ovary, and choroid gland, and rarely in the brain and heart. A small pleomorphic bacterium was observed in Giemsa-stained blood smears and spleen imprints. The bacterium did not grow on standard microbiological media and has not been isolated in cell culture. We obtained a near-complete 16S ribosomal DNA sequence with high similarity to Francisella spp. sequences previously identified in tilapias Oreochromis spp. (Taiwan), Atlantic cod Gadus morhua (Norway), and three-line grunts Parapristipoma trilineatum (Japan).