Mercury exists in two forms, organic and inorganic. Organic compounds are used as fungicides to treat seed grains prior to sowing. Poisoning occurs if swine are fed corn or cereals that have been treated or contaminated with such a fungicide. Inorganic mercury as mercury chloride is used as a disinfectant and in some paints, batteries and thermometers.

Clinical signs

Mercury is a cumulative poison so clinical signs vary depending upon the duration of intake as well as the dose and the type of mercury. As a poison mercury acts primarily on the gastro-intestinal tract causing vomiting and bloody diarrhoea. Dead (necrotic) pieces of tissue may be seen in the faeces. Damage to the kidney also occurs leading to signs of uraemia. Pigs stop eating and loose body condition. White crystalline deposits may be seen in the urine. Nervous signs maybe seen including ataxia, blindness, wandering, partial paralysis, coma and death.

Diagnosis

The clinical signs and post-mortem lesions may suggest mercury poisoning which may be confirmed by finding the source of poisoning and by laboratory analysis of mercury levels in the kidney and liver (normally less than 1ppm).

Treatment

• This is carried out by a combination of sodium thiosulphate 20% solutions given intravenously at 1ml/5kg body weight together with dimercaprol by intramuscular injection at a level of 3mg/kg body weight. Seek veterinary advice.
• Feed pigs with either milk or egg protein which act as an absorbent.