The Role of Nile Tilapia (Oreochromis niloticus) in the Life Cycle of Toxocara spp.

The present study aimed to experimentally assess Nile tilapia as potential paratenic host of Toxocara spp. A total of 15 Nile tilapia (Oreochromis niloticus) were fed with 300 embryonated Toxocara canis eggs by oral gavage, while five others of the control group received distilled water. The fish were individually analyzed at 16, 24, 48, 72, and 240 h after inoculation. Water contamination was assessed, and tissue migration by liver, gastrointestinal tract (GIT), eyes, and central nervous system. A murine model was used as the paratenic host for egg infectivity assessment. Eggs and larvae were found in plastic tank water and fish GIT, ranging from 23 to 86% per fish. Eggs and larvae were recovered from the tank water (76.3%) and fish GIT (23.7%). The counting of eggs and larvae observed was negatively correlated with number of eggs and larvae in the water tank (rho = -0.698, p = 0.003). Shedding of embryonated eggs was first detected at 16 and up to 240 h, with significant egg and larvae yield decrease on water-shedding (p = 0.001) and in the GIT (p = 0.007). Although no T. canis larva was recovered in fish tissues, egg infectivity after fish GIT transit was experimentally confirmed by mice assessment. In conclusion, despite shedding viable embryonated eggs through the gastrointestinal tract, tilapias may not play a role as a suitable paratenic hosts for Toxocara spp., posing low risk of zoonotic transmission by fish meat consumption.

Influence of temperature and exercise on growth performance, muscle, and adipose tissue in pacus (Piaractus mesopotamicus).

The aim of this study was to evaluate the effects of temperature and swimming exercise on fish growth in pacus (Piaractus mesopotamicus). Pacus weighing 0.9 - 1.9g and 2.7 - 4.2cm in standard length were cultivated at an initial density of 120 fish m-3 in 3 recirculation systems containing 6 water tanks at a volume of 0.5m3 each at temperatures of 24, 28 and 32°C. At each temperature, three tanks were modified to generate exercise activity in the specimens and force the fish to swim under a current speed of 27.5cms-1. At the end of the experiment, the following metrics were evaluated: fish performance, morphometry (length, width, height and perimeter in different body positions), and the diameter and density of muscle and subcutaneous ventral adipose tissues. At 28°C, pacus were both heavier and had greater weight gain after 240 days of cultivation. Additionally, exercise improved the feed conversion. An increase of 4°C (30°C) did not provide any improvement in the performance of the fish. However, swimming exercise improved the performance of pacus, providing increases of 38% and a 15% improvement in feed conversion. Both temperature and exercise influenced the body morphology (especially in the caudal region) and the cellularity of white and red muscle fibers and adipocytes.

Austrodiplostomum compactum (Lutz, 1928) (Digenea, Diplostomidae) in the eyes of fishes from Paraná river, Brazil / Austrodiplostomum compactum (Lutz, 1928) (Digenea, Diplostomidae) em olhos de peixes do rio Paraná, Brasil

Parasitological indexes of Austrodiplostomum compactum (Digenea, Diplostomidae) in fishes from the Paraná River, Presidente Epitácio region, state of São Paulo, Brazil, and their relationship with climate and water quality are evaluated. Fifty-one specimens of Plagioscion squamosissimus, 39 Geophagus surinamensis, 27 Hoplias malabaricus and 23 Cichla sp. were collected between June 2007 and June 2008. Water quality and rainfall indexes were measured monthly. P. squamosissimus had the highest parasite rate, with 98% total prevalence, intensity of infection varying between 1 and 255 and parasite mean abundance totaling 40.5 ± 9.9. H. malabaricus had the next parasite rate, with 66.6% total prevalence, parasite intensity between 2 and 184 and mean abundance totaling 22.4 ± 20.9. Cichla sp. had a total prevalence of 52.1%, intensity between 1 and 21, and mean abundance 4.3 ± 2.9. Finally, G. surinamensis had a total prevalence of 46.1%, intensity between 1 and 53 and mean abundance 7.1 ±8.8. A survey of diplostomid infection in Brazil and the role of piscivore fish as an important host have also been discussed.

Este estudo avaliou os índices parasitológicos de Austrodiplostomum compactum (Digenea, Diplostomidae) em peixes do rio Paraná, região de Presidente Epitácio, Estado de São Paulo, Brasil e sua relação com o clima e qualidade da água. Cinquenta e um espécimes de Plagioscion squamosissimus, 39 Geophagus surinamensis, 27 Hoplias malabaricus e 23 Cichla sp. foram coletados de junho de 2007 a junho de 2008. Qualidade da água e pluviosidade foram medidas mensalmente. O peixe mais parasitado foi P. squamosissimus com 98% de prevalência total, intensidade de infecção variando de 1 a 255 e abundância média de 40,5 ± 9,9. O segundo peixe mais parasitado foi H. malabaricus com 66,6% de prevalência total, intensidade de 2 a 184 e abundância média de 22,4 ± 20,9. Cichla sp. apresentou 52,1% de prevalência, intensidade de 1 a 21 e abundância média de 4,3 ± 2,9. Finalmente, G. surinamensis apresentou 46,1% de prevalência, intensidade de 1 a 53 e abundância média de 7,1 ± 8,8. Um levantamento de infecções por diplostomídeos no Brasil e o papel de peixes piscívoros como importantes hospedeiros é também discutido.