VPT 421: Veterinary Toxicology (2+0)

ALPHANAPHTHYL THIOUREA (ANTU)

• This toxin causes local gastric irritation and most of the times vomited by the animals which can vomit and hence escape from toxicity.
• When the toxin is absorbed, it increases the permeability of the lung capillaries.
• ANTU kills by producing a marked hydrothorax and pulmonary edema.
• The animal literally drowns in its own fluids.
• The exact mechanism resulting in increased capillary permeability has not been determined.
• Reaction of ANTU with sulfhydryl groups may be a necessary part of the mechanism of toxic action, since it has been reported that sulfhydryl group blocking agents are effective antidotes in rats in some experimental conditions.
• Ruminants are resistant to poisoning.
• Dogs and pigs are occasionally poisoned.
• The symptoms include:
  • vomiting, hypersalivation, coughing and dyspnoea.
  • Severe pulmonary oedema, moist rales, cyanosis, weakness, ataxia, rapid weak pulse, cold extremities and subnormal temperature have been noticed.
• Animals continue to vomit as the disease progresses and the vomitus may consist entirely of blood.
• A watery fluid diarrhea becomes hemorrhagic if the patient survives the acute symptoms.
• The affected animal remains standing or sits on its haunches to relieve thoracic pressure. As the animals become weaker, they assume a position of sternal recumbency.
• In the terminal stages, the lungs are congested or filled with fluid and fluid may escape from the mouth.
• The animal becomes comatose and fails to respond to external stimuli.
• Most deaths occur in 2 - 4 hours after symptoms appear. Owing to the seriousness of ANTU toxicosis, measures to eliminate the gastrointestinal tract contents should be followed as soon as possible after exposure.
• Treatment includes use of emetics if no respiratory distress is noticed.
• Activated charcoal may possibly be of value in the lavage solutions and should be left in the lumen thereafter. If a thorough enterogastric lavage is not performed, then a saline cathartic should also be administered.
• Administration of n-amyl mercaptane and sodium thiosulphate, positive oxygen therapy and administration of osmotic diuretics and atropine are useful.
• The prognosis for animals suffering from clinically significant ANTU poisoning is poor .