Diagnosis and Treatment of Acute Selenium Poisoning in Pigs

1 Incidence and Clinical Symptoms

In November 2002, a specialized household in Wuhua County, Guangdong, raised a total of 20 piglets from the same litter. The sow's milk was sufficient, the piglets nursed normally, and they grew well; at 10 days of age, each weighed about 1.5-2 kg. The owner injected each pig intramuscularly with 2 ml of sodium selenite vitamin E injection. On the morning of the next day, 2 pigs were depressed, unwilling to walk, refused to nurse, urinated frequently while standing, with a small volume and in a painful manner, had rapid and labored breathing, walked as if drunk, wandered aimlessly, and bumped their heads against walls or circled. The body surface, especially the ear margins and abdominal skin, was purplish red; the conjunctiva and lip mucosa were pale; the body temperatures were 36.5 degrees C and 35 degrees C respectively, and the heart rate was 120 beats/min. They died after about 6 h. At the same time, other smaller pigs successively showed the same symptoms and died, and by the morning of the 3rd day after injection, 12 pigs had died.

2 Necropsy Lesions

The laryngeal mucosa showed punctate hemorrhage; the trachea was congested and contained white foamy mucus; the lungs were dark red, congested, and edematous, with ecchymotic patches on the surface; the pericardium was dilated and contained pale yellow fluid, and the epicardium showed punctate hemorrhage; the liver was swollen and congested; the gallbladder was swollen and filled with thick bile; the kidneys were enlarged, with capsules that peeled off easily, pale grayish white, and showed punctate hemorrhage, while there were no hemorrhagic spots in the bladder; the intestinal tract was congested and purplish, and the intestinal lumen was filled with mucus; the stomach was filled with white milk, with hemorrhage at the gastric fundus, and the mucosa scraped off easily; the mesenteric vessels were engorged and appeared as purplish-brown dendritic branching; the lymph nodes showed no obvious visible changes.

3 Treatment

Sodium thiosulfate was first diluted with 2 ml of water for injection at 0.2 g per pig and injected intramuscularly once. After about 6 h, 0.1 g per pig was injected repeatedly. At the same time, vitamin B12 0.5 mg and vitamin B1 0.1 g were injected intramuscularly once; for severely affected pigs, 10% caffeine sodium benzoate 5 ml was injected intramuscularly once. After treatment, no further deaths occurred.

4 Summary and Discussion

Based on the incidence and therapeutic diagnosis, we suspected selenium poisoning.

4.1 Our county is a mountainous area deficient in selenium, and selenium deficiency disease has attracted widespread attention. However, acute selenium poisoning is more likely to cause livestock deaths, while chronic selenium poisoning affects the growth and development of livestock and poultry. For this reason, the author believes that the dosage should be strictly controlled when sodium selenite vitamin E injection is used clinically, so as to avoid poisoning. Under general circumstances, adding oral selenium preparations to feed can effectively prevent selenium deficiency; when there are no obvious symptoms of selenium deficiency, it is unnecessary to use selenium-containing injections, and even less necessary to use selenium-containing injections to prevent selenium deficiency.

4.2 According to relevant literature, the selenium requirement of pigs is only 1.0 mg/kg, and the toxic dose is 7.0 mg/kg. When pigs are injected intramuscularly with 1 mg/kg body weight, toxic symptoms appear, so the dosage should be controlled during use.

4.3 The mechanism of selenium poisoning is mainly that excess selenium replaces the sulfur of sulfur-containing amino acids in proteins, thereby inhibiting the metabolism of amino acids and the activity of sulfhydryl enzymes. Therefore, the author believes that treatment of selenium poisoning with sulfur preparations has a relatively good effect, as they can directly interact with selenium and thus play a detoxifying role; at the same time, sodium thiosulfate is inexpensive and convenient to use, and can be given both intravenously and intramuscularly, so it can be the first-choice drug for selenium poisoning.