Insecticides Toxicity (Pyrethroids, Organochlorines, Organophosphates and Carbamates)
Insecticides like synthetic pyrethroids, organochlorines, organophosphates and carbamates toxicity are widely seen among livestock animals.
Synthetic Pyrethroids
Source
Insecticidal properties of pyrethrum flowers (Chrysanthemum; cinerariaefolium, C. rosium) are well recognized.
Natural pytrehrins are now restricted and almost being replaced by synthetic pyrethroids.
Most commonly used synthetic pyrethroid in India belong to alpha-cyano pyrethorid such as deltamethrin, cypermethrin, fenvalerate etc.
Non alpha cyano pyrethroid including allethrin, permethrin and are used to check proliferation of pest and insects and to boost agriculture production and disease control programmes. They can also be used to kill ectoparasites in animals.
Clinical Signs
Pyrethroid insecticides have been classified into two groups, Type I and II, on the basis of poisoning syndrome.
Type I produce tremor syndrome. Type II produced choreoathetosis and salivation (CS) syndrome.
The clinical manifestations observed after oral administration in rats include ataxia, abasia and gait abnormalities, choreoathetosis, “tip-toe” walk and increased salivation, lacrimation, piloerection, tremor and convulsions.
The mortalities occur within the first 3 hours and surviving animals recover within 7 days. Neurological behavioural syndromes of Type I and Type II pyrethroids are quite different.
Tremors, hyperthermia and decreased motor activity in Type I and pawing, borrowing, salvation, whole body tremor to choreoathetosis, hypothermia and lowered motor activity in Type II are evident.
Treatment
No selective antidote is available for the treatment of synthetic pyrethorid insecticide poisoning.
Sedation by barbiturate such as pentobarbitone 10 mg/kg, IV or IM; phenobarbitone, 25-50 mg/kg intramuscular in small animals; or chloral hydrate, 5mg/50 kg b.w. by oral route in large animals have beneficial effect to control convulsions.
Atropine sulphate (0.1 -0.5 mg/kg IM) can be given to check profuse salivation, lacrimation and nasal secretions.
Organochlorines or Chlorinated Hydrocarbons
Source
Chlorinated hydrocarbons are widely used for prevention and control of insects infestation around agricultural farms, house premises and on animals.
Animals may be poisoned by ingestion of contaminated feed, water and air. Sprayed foliage or fodder or direct spray are the major sources of poisoning of organo-chlorine pesticides.
These insecticides have tendency of persistence in environment and ability to accumulate in biologic food chains, and thus these residues upon consumption may cause chronic toxicity in man and animals.
These are non-specific stimulant to the central nervous system.
Clinical Signs
The clinical signs of poisoning of organochlorine insecticides are almost similar in all species, however, may vary in onset, severity and duration depending on quantity and type of the insecticide.
Clinical signs appear within a few minutes to several hours or even days and are characterized by hyperaesthesia, profuse salivation, lacrimation, diarrhea; urination, piloerection, In-coordination, jaw champing, respiratory distress, laboured breathing, clonic convulsions and fever.
Death may occur within minutes to few hours or even after several days. Respiratory failure is the main cause of death.
Treatment
There is no specific antidotal therapy for the treatment of organochlorine insecticide poisoning.
Barbiturates or sedatives such as pentobarbitone, 10 mg/kg IV or IM or phenobarbitone, 25-50 mg/kg intramuscular in small animals; or chloral hydrate, 5 gm/50 kg b.wt. by oral route in large animals have beneficial effect to control convulsion, Atropine sulphate (0.1-0.2 mg/kg; SC) an be given to check profuse salivation, lacrimation and nasal secretions.
The use of combination of cholestyramine with non-absorbable oils for maximum fecal elimination of these pesticides.
Organophosphates and Carbamates
Source
Organophosphorus and carbamate compounds are used as insecticide, pesticides, herbicides, exfoliants and soil nematodicides etc.
In agriculture practice and to control external and internal parasites in animals.
Livestock may be poisoned by improper dipping, dusting, spraying, accidental Ingestion or malicious use of these insecticides.
Organophosphate insecticides irreversibly inhibit the acetylcholinesterase (AChE) enzymes where as the carbamates inhibit the enzyme reversibly.
Clinical Signs
Characteristic signs of OPC and carbamates poisoning in animals include profuse salvation, lacrimation, diarrhoea, coughing, tremors and convulsions.
In coordination, laboured breathing, dyspnea, hyperaesthesia and CNS stimulation.
Depending upon dose, death of animal occurs within few minute to hours due to respiratory failure.
Treatment
Atropine sulphate is administrated at a dose of 0.2-0.5 mg/kg and the dosage can be increased up to 1 mg/kg in severe cases.
One fourth of the dose can be administrated as iv. and rest by IM or SC route which can be repeated at 3-6 hours interval as per clinical manifestation.
Excess atropinization should be avoided which may worsen the condition of animal. AchE reactivator, pyridine-2–aldoxime methiodine (2-PAM,pralidoxime) is a good adjunct to atropine sulphatein early stage of the poisoning and is administrated at the dose rate of 20-50 mg/kg as a 10% solution by slow IV infusion.
2-PAM or any other AchE reactivator is not recommended for the treatment of carbamate poisoning and also in the later stage of organophosphate poisoning.
Therapy with multivitamin, fluid (dextrose saline) electrolyte may also be recommended.
