Toxicological and Pathological Review of Concurrent Occurrence of Nitrite Toxicity and Swine Fever in Pigs

BACKGROUND: Plant associated nitrate/nitrite poisoning in buffalo, cattle, goat and sheep had been reported from various parts of the world. Horses and pigs are considered less susceptible to nitrate poisoning. In this study epidemiology of rare outbreak of nitrate poisoning in combination with classical swine fever in a small pig farm was investigated for development of strategies to control and prevent such incidents in future. MATERIALS AND METHODS: Concurrent infection of nitrate toxicity and classical swine fever were recorded in district Nawanshahar, Punjab. Eight pigs suddenly fell sick and died 2 days after feeding barseem + oats and marriage waste food. Twelve pigs were sick exhibiting symptoms of anorexia, fever (104-105(o)F), depression, constipation followed by diarrhea, respiratory difficulty, tremors and staggering gait with recumbency in four completely off-feed pigs. Blotchy discolorations of the skin of extremities (ears and snout) were observed in three pigs. RESULTS: Hematological examination revealed marked leucopenia. Postmortem examination revealed dark brown colored blood evident on opening the carcass and presence of barseem, oats in stomach and intestines. Lymph nodes were swollen and hemorrhagic. Serosal surface of spleen show various infarcts and button ulcers were recorded in cecum and colon, pathognomic lesion of classical swine fever. Nitrate toxicity was confirmed on the basis of quantitative determination of nitrate in the biological material of sick and dead animals. Fodder samples were (barseem + oats) positive for diphenylamine blue (DPB) test, Nitrate concentration in offended barseem and oats were found to be 2612 ppm and 3344 ppm as nitrate nitrogen (No3-N), respectively. Excessive amount of nitrate in stomach contents (924-1365 ppm), liver (22-48 ppm) and kidney (17-22 ppm) of dead animals (n = 8) confirmed that death of pigs was due to toxicity induced by nitrate/nitrite. CONCLUSION: The green fodder should be used cautiously in pigs and screening of fodder with DPB test prior offering to animals is strongly recommended to contain the nitrate/nitrite toxicity risk.