Copper in Cultured Shrimp Litopenaeus vannamei and Its Reduction in Hepatopancreas After Exposure to Sublethal Nitrite Levels

This research was to evaluate the load and mobility of Cu in juvenile Litopenaeus vannamei after exposure (48 h) to sublethal concentration of nitrite (5.3 mg/L NO₂^--N) at a salinity of 3.0 g/L. The hypothesis is that such exposure causes a Cu mobility in the tissues of shrimp. The Cu concentration in exoskeleton, hepatopancreas, muscle and hemolymph in the control group were 38.9 ± 3.0, 2478 ± 256, 11.9 ± 0.2 µg/g (dw) and 95.4 ± 19.1 µg/mL, while in the nitrite exposure, were 46.0 ± 0.1, 1546 ± 173, 11.3 ± 0.3 µg/g (dw) and 118.2 ± 10.5 µg/mL, respectively. Only hepatopancreas exhibited a significant (p < 0.05) reduction (37.6%) between the control and the nitrite exposure. This is evidence that nitrite has a significant effect on Cu accumulation in hepatopancreas when shrimp are exposed to sublethal levels in a salinity of 3 g/L. Results confirm the hypothesis that Cu mobility was only significant in hepatopancreas.

Acute Toxicity of Ammonia, Nitrite and Nitrate to Shrimp Litopenaeus vannamei Postlarvae in Low-Salinity Water

Shrimp farming in low salinities waters is an alternative to increasing production, and counteracting disease problems in brackish and marine waters. However, in low-salinity waters, toxicity of nitrogen compounds increases, and there is no available data of its acute toxicity in shrimp postlarvae. This study determined the acute toxicity of ammonia, nitrite and nitrate in Litopenaeus vannamei postlarvae in 1 and 3 g/L salinity, as well as the safety levels. The LC₅₀ confirms that nitrite is more toxic than ammonia and nitrate in low salinity waters, and that its toxicity increases with a decrease in salinity. The safe levels estimated for salinities of 1 and 3 g/L were 0.54 and 0.81 mg/L for total ammonia-N, 0.17 and 0.25 mg/L for NO₂-N, and 5.6 and 21.5 mg/L for NO₃-N, respectively.

High prevalence of Toxoplasma gondii antibodies in domestic pigs in Oaxaca State, Mexico

Pigs are important in the epidemiology of toxoplasmosis in North America. Seroprevalence of Toxoplasma gondii infection in 525 domestic pigs (337 backyard raised, 188 farm raised) in Oaxaca State, Mexico was determined using the modified agglutination test (MAT, cutoff 1:25). Antibodies to T. gondii were found in 58 (17.2%) of the 337 backyard pigs with MAT titers of 1:25 in 10, 1:50 in 12, 1:100 in 18, 1:200 in 6, 1:400 in 6, 1:800 in 3, and 1:1,600 in 3. Seropositive pigs were found in 39 (37.9%) of 103 homes in all 7 municipalities surveyed. Seroprevalence of T. gondii infection in backyard pigs varied with age, gender, geographic region, climate, and altitude. High seroprevalence was found in pigs ≥ 9-mo-old (40%), in females (40%), in pigs from the Istmo region (33.3%), and in those raised in a tropical climate (65%). Seroprevalence was higher (24.5%) in pigs raised at 100-660 m above sea level than in those at 20-60 m of altitude (14.2%). With respect to farm pigs, only 1 (0.5%, MAT titer 1:100) of 188 pigs from 5 farms was positive for anti- T. gondii antibodies. The results affirm that the management system (outdoor vs. indoor system with biosecurity) is a key factor in the epidemiology of porcine toxoplasmosis. Because there is no national system of determining the T. gondii infection status at the time of slaughter, precautions should be taken while handling pig carcasses, and all pork should be cooked thoroughly before human consumption.