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To test whether effluents released from white spot syndrome virus (WSSV)-infected farm ponds are a pathway for spreading WSSV, WSSV-negative Pacific whiteleg shrimp, Litopenaeus vannamei , were exposed to WSSV-containing water under conditions of fluctuating water temperatures. White spot disease outbreaks occurred at the shrimp ponds before and during the experiment. Two cages were placed inside each test pond, and one was placed at the outlet canal. Each cage was stocked with 30 shrimp. Hemolymph from stocked shrimp was collected at intervals of 24, 48, 72, 120, 168, and 360 h after exposure and analyzed for presence of WSSV DNA by nested polymerase chain reaction. At diurnal variation of water temperature from 28.0 to 33.4 C, WSSV was detected as early as 120 h (ca. 11% of shrimp hemolymph pools) and 168 h (ca. 18% of shrimp hemolymph pools). WSSV was detected by 360 h (ca. 33% of shrimp hemolymph pools) in all cages, when water temperature varied from 24.9 to 28.5 C during a 48-h period. Cumulative mortality in cages inside ponds was ≤50.0 and 86.7% at the outlet canal. These data show that grow-out operations during the summer-autumn transition are at risk of WSSV outbreaks. The experiment demonstrated that WSSV can be spread by shrimp farm water drainage.

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Wastewater can be reused after a treatment process and compliance with high quality standards that guarantee its safe use. The wastewater treatment plant of the Autonomous University of Aguascalientes (AUA), like others, uses primary, secondary, and tertiary processes. The tertiary process followed is chlorination and is used to eliminate microorganisms from the secondary process. Although water of acceptable quality is obtained with chlorine, there is evidence that toxic substances are generated when reacting with organic matter, so alternatives to the use of chlorination have been analyzed. In the present study, silver nanoparticles were synthesized from the aqueous extract of the Opuntia ficus indica fruit peel (OfAgNPs), by reducing a 2 mM solution of AgNO3. OfAgNPs were characterized by UV-visible spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic absorption spectroscopy, and dynamic light scattering, in addition to his electrophoretic mobility. The OfAgNPs are spherical, with an average particle size distribution of 64.28 ± 11.82  nm, relatively stable at room temperature, negatively charged ( − 25.1 ± 0.03  mV), and composed of 61.29% silver. The activity of OfAgNPs was evaluated in water from the effluent of the AUA treatment plant, before and after chlorination, and inhibition of bacteria Escherichia coli var 1, Enterobacter aerogenes var 1, Citrobacter freudi var 2, atypical E. coli, and aerobic mesophilic microorganism was tested.