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We report two outbreaks of nitrate and nitrite poisoning in Paraíba, Northeast Brazil. The first, due to Pennisetum purpureum (elephant grass), and the second, due to P. purpureum and Brachiaria spp. (brachiaria grass), both occurred during a prolonged drought. In the first outbreak, the irrigation of the pastures with wastewater and sewage contributed to nitrate accumulation. The second outbreak occurred in pastures cultivated in the border of a dam, that had been submerged for long time accumulating large amounts of organic matter in the soil. Other probably risk factors for nitrate accumulation included the use of chemical fertilizers and herbicides and burning of the vegetation. In the first outbreak, four calves out of a total of 42 cattle died, and in the second outbreak 49 out of 243 cattle, including adults, yearlings, and a 2-day-old calf died. The clinical signs included dyspnea, cyanosis, ataxia, and falls, leading to death. The presence of nitrates was detected in both outbreaks using the diphenylamine test. Quantitative tests were performed in the second outbreak using a portable nitrate meter, and high nitrate concentrations were found. The characteristic macroscopic findings and absence of microscopic lesions and response to treatment with methylene blue were key to the diagnosis of poisoning by nitrates and nitrites. We conclude that poisoning by nitrates and nitrites in ruminants in the semiarid region of Northeastern Brazil is frequent due to the cultivation of grasses in the border of dams that had been covered by water for long periods or in areas irrigated by wastewater and/or sewage. In addition, the use of a portable measuring device is an effective alternative for the quantification of nitrates in pastures.(AU)

Relatamos dois surtos de intoxicação por nitrato e nitrito na Paraíba, Nordeste do Brasil. O primeiro por Pennisetum purpureum (capim-elefante), e o segundo por P. purpureum e Brachiaria spp. (capim braquiária); ambos ocorreram durante uma estiagem prolongada. No primeiro surto, a irrigação das pastagens com água poluída e esgoto contribuiu para o acúmulo de nitrato. O segundo surto ocorreu em pastagens cultivadas na borda de uma barragem, que há muito tempo ficavam submersas, acumulando grande quantidade de matéria orgânica no solo. Outros prováveis fatores de risco para o acúmulo de nitrato incluíram o uso de fertilizantes químicos e herbicidas e a queima da vegetação. No primeiro surto, quatro bezerros de um total de 42 bovinos morreram, e no segundo surto 49 de 243 bovinos, incluindo adultos, jovens de um ano e um bezerro de 2 dias de idade morreram. Os sinais clínicos incluíram dispneia, cianose, ataxia e quedas, levando à morte. A presença de nitratos foi detectada em ambos os surtos pelo teste de difenilamina. Testes quantitativos foram realizados no segundo surto usando um medidor portátil de nitrato, e altas concentrações de nitrato foram encontradas. Os achados macroscópicos característicos e a ausência de lesões microscópicas e a resposta ao tratamento com azul de metileno foram fundamentais para o diagnóstico de intoxicação por nitratos e nitritos. Concluímos que a intoxicação por nitratos e nitritos em ruminantes na região semiárida do Nordeste do Brasil é frequente devido ao cultivo de gramíneas nas bordas de barragens que estiveram cobertas por água por longos períodos ou em áreas irrigadas por água poluída e/ou esgoto. Além disso, o uso de medidor portátil é uma alternativa eficaz para a quantificação de nitratos em pastagens.(AU)

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We report two outbreaks of nitrate and nitrite poisoning in Paraíba, Northeast Brazil. The first, due to Pennisetum purpureum (elephant grass), and the second, due to P. purpureum and Brachiaria spp. (brachiaria grass), both occurred during a prolonged drought. In the first outbreak, the irrigation of the pastures with wastewater and sewage contributed to nitrate accumulation. The second outbreak occurred in pastures cultivated in the border of a dam, that had been submerged for long time accumulating large amounts of organic matter in the soil. Other probably risk factors for nitrate accumulation included the use of chemical fertilizers and herbicides and burning of the vegetation. In the first outbreak, four calves out of a total of 42 cattle died, and in the second outbreak 49 out of 243 cattle, including adults, yearlings, and a 2-day-old calf died. The clinical signs included dyspnea, cyanosis, ataxia, and falls, leading to death. The presence of nitrates was detected in both outbreaks using the diphenylamine test. Quantitative tests were performed in the second outbreak using a portable nitrate meter, and high nitrate concentrations were found. The characteristic macroscopic findings and absence of microscopic lesions and response to treatment with methylene blue were key to the diagnosis of poisoning by nitrates and nitrites. We conclude that poisoning by nitrates and nitrites in ruminants in the semiarid region of Northeastern Brazil is frequent due to the cultivation of grasses in the border of dams that had been covered by water for long periods or in areas irrigated by wastewater and/or sewage. In addition, the use of a portable measuring device is an effective alternative for the quantification of nitrates in pastures.

Relatamos dois surtos de intoxicação por nitrato e nitrito na Paraíba, Nordeste do Brasil. O primeiro por Pennisetum purpureum (capim-elefante), e o segundo por P. purpureum e Brachiaria spp. (capim braquiária); ambos ocorreram durante uma estiagem prolongada. No primeiro surto, a irrigação das pastagens com água poluída e esgoto contribuiu para o acúmulo de nitrato. O segundo surto ocorreu em pastagens cultivadas na borda de uma barragem, que há muito tempo ficavam submersas, acumulando grande quantidade de matéria orgânica no solo. Outros prováveis fatores de risco para o acúmulo de nitrato incluíram o uso de fertilizantes químicos e herbicidas e a queima da vegetação. No primeiro surto, quatro bezerros de um total de 42 bovinos morreram, e no segundo surto 49 de 243 bovinos, incluindo adultos, jovens de um ano e um bezerro de 2 dias de idade morreram. Os sinais clínicos incluíram dispneia, cianose, ataxia e quedas, levando à morte. A presença de nitratos foi detectada em ambos os surtos pelo teste de difenilamina. Testes quantitativos foram realizados no segundo surto usando um medidor portátil de nitrato, e altas concentrações de nitrato foram encontradas. Os achados macroscópicos característicos e a ausência de lesões microscópicas e a resposta ao tratamento com azul de metileno foram fundamentais para o diagnóstico de intoxicação por nitratos e nitritos. Concluímos que a intoxicação por nitratos e nitritos em ruminantes na região semiárida do Nordeste do Brasil é frequente devido ao cultivo de gramíneas nas bordas de barragens que estiveram cobertas por água por longos períodos ou em áreas irrigadas por água poluída e/ou esgoto. Além disso, o uso de medidor portátil é uma alternativa eficaz para a quantificação de nitratos em pastagens.

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Background: Nitrate and nitrite poisoning is associated with pasture intake that has high nitrate levels and leads to acute methemoglobinemia. Pasture may accumulate nitrate under certain conditions, such as excessively fertilized soil or environmental conditions that enhance the N absorption (rain preceded by a period of drought). After ingestion of plants, this substrate reaches the rumen and, in physiological conditions, is reduced to nitrite and afterward to ammonia. The aim of this study was to evaluate changes in cholinesterase activities and oxidative stress caused by subclinical poisoning for nitrate and nitrite in cattle fed with Pennisetum glaucum in three different fertilization schemes.Materials, Methods & Results: In order to perform the experimental poisoning, the pasture was cultivated in three different paddocks: with nitrogen topdressing (urea; group 1), organic fertilizer (group 2) or without fertilizer (group 3; control). Nitrate accumulation in forage was evaluated by the diphenylamine test. After food fasting of 12 h, nine bovine were randomly allocated to one of the experimental groups and fed with fresh forage (ad libitum) from respective paddock. In different time points from beginning of pasture intake (0, 2, 4, 6 and 9 h) heart rate and respiratory frequency were assessed, as well as mucous membrane color and behavioral changes. Blood samples from jugular vein into vials with and without anticoagulant were collected. From blood samples, serum nitrite levels, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzyme activity were evaluated, as well as oxidative stress through the following parameters: levels of nitrate/nitrite (NOx ), thiobarbituric acid reactive substances (TBARS) and reactive oxygen species (ROS), beyond the antioxidant system by enzyme activity measurement of catalase (CAT) and superoxide dismutase (SOD).[...]

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Background: Nitrate and nitrite poisoning is associated with pasture intake that has high nitrate levels and leads to acute methemoglobinemia. Pasture may accumulate nitrate under certain conditions, such as excessively fertilized soil or environmental conditions that enhance the N absorption (rain preceded by a period of drought). After ingestion of plants, this substrate reaches the rumen and, in physiological conditions, is reduced to nitrite and afterward to ammonia. The aim of this study was to evaluate changes in cholinesterase activities and oxidative stress caused by subclinical poisoning for nitrate and nitrite in cattle fed with Pennisetum glaucum in three different fertilization schemes.Materials, Methods & Results: In order to perform the experimental poisoning, the pasture was cultivated in three different paddocks: with nitrogen topdressing (urea; group 1), organic fertilizer (group 2) or without fertilizer (group 3; control). Nitrate accumulation in forage was evaluated by the diphenylamine test. After food fasting of 12 h, nine bovine were randomly allocated to one of the experimental groups and fed with fresh forage (ad libitum) from respective paddock. In different time points from beginning of pasture intake (0, 2, 4, 6 and 9 h) heart rate and respiratory frequency were assessed, as well as mucous membrane color and behavioral changes. Blood samples from jugular vein into vials with and without anticoagulant were collected. From blood samples, serum nitrite levels, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzyme activity were evaluated, as well as oxidative stress through the following parameters: levels of nitrate/nitrite (NOx ), thiobarbituric acid reactive substances (TBARS) and reactive oxygen species (ROS), beyond the antioxidant system by enzyme activity measurement of catalase (CAT) and superoxide dismutase (SOD).[...](AU)

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Se presentó el caso de un paciente asistido en el servicio de urgencia de nuestro hospital con síntomas de alguna afección neurológica, el mismo fue ingresado con el diagnóstico presuntivo de apoplejía isquémica. El cuadro clínico del paciente empeoró, presentó entonces cianosis importante. Al interrogar a sus familiares, se conoció la existencia en su hogar de nitrato de potasio (sal de nitro) y la posibilidad de su ingestión accidental como sal común, interpretada como una metahemoglobinemia tóxica, a la que se impuso tratamiento con azul de metileno y oxigenación hiperbárica a 2 ATA durante 50 minutos de isopresión por cuatro días con resultados excelentes(AU)

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Four diets, each containing different levels of ascorbic acid were fed to duplicate groups of steelhead trout (Salmo gairdneri) in two four-week periods. Tolerance to nitrites increased when the concentration of ascorbic acid was high. Flow-through bioassays in fingerlings showed that when the temperature increased the percent of methemoglobin in their blood also increased. The tolerance to nitrite toxicity was less in large fish than in those smaller fed the same concentration of ascorbic acid. Possibly ascorbic acid acts in the reduction of methemoglobin to hemoglobin, and also it has a protective effect against stress in the fish. A "safe" level of 200 mg/kg of ascorbic acid in practical diets was reached.

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