MECHANISM OF ACTION:
In the rumen nitrate is reduced to nitrite and following absorption haemoglobin is oxidised to methaemoglobin.
TOXICITY:
• Great variations both inter- and intraspecies
• Nitrate - c. 0,5 g/kg sheep - 5g/kg cattle
• Nitrite - c. 20 mg/kg sheep - 100mg/kg cattle
For soluble oxalate poisoning, go to Urogenital Menu.
SYNDROMES:
Nitrate/nitrite poisoning.
SYSTEMS AFFECTED:
Haemopoietic system.
CLINICAL SIGNS:
Acute poisoning:
Respiratory System:
• Hyperpnoea
• Dyspnoea
• Anoxia precipitated by exercise
Central Nervous System:
• Ataxia
• Tremors
• Weakness
• Terminal convulsions (brain anoxia)
Cardiovascular System:
• Cardiovascular failure, syncope
• Cyanosis
• Methaemoglobinaemia: Blood & mucous membranes a dirty chocolate brown colour
• Rapid weak pulse (drop in blood pressure)
Gastrointestinal Tract:
• Diarrhoea
• Salivation (vomition)
Abortion - especially last trimester
For soluble oxalate poisoning, go the Urogenital Menu.
NECROPSY:
Macroscopical findings:
• Cyanosis• Tarry, dark, red-brown to brown blood• Tissues and mucous membranes brown (Not apparent in every case)
• Congestion
• Petechial and ecchymotic haemorrhages on mucosal, visceral and serosal surfaces.
HISTOPATHOLOGY:
• Nothing unusual or pathognomonic
For soluble oxalate poisoning, go the Urogenital Menu.
TREATMENT:
1. Methylene blue. Acts as intermediate electron acceptor that accelerates the reaction between NADPH and methaemoglobin.
2. Ascorbic acid. Also used in dogs for paracetamol poisoning.
