VLD 421: Veterinary Clinical Biochemistry and Laboratory Diagnosis-II (0+1)

INSECTICIDES

Appreciation and Differentiation of Symptoms caused by Insecticides

1	Organochlorine	Acute toxicity: Vomition, profuse frothy salivation, mydriasis, diarrhoea, urination. Slowly twitching starts first from eyelids, face, neck and extends to fore parts and the hind parts of body. Animals become restless, lose control over movements, stagger, move in circle, and strike against obstacles or jump over unseen objects. Abnormal postures, such as resting the sternum on the ground while remaining upright in the rear, or keeping the head down between the forelegs is often seen. In advanced stages, intermittent clonic-tonic seizures, opisthotonus, paddling and clamping of jaws are common. Death may occur within minutes, hours or after several days which is due to respiratory failure. Chronic toxicity: In chronic toxicity, clinical signs may be similar to those of acute toxicity, perhaps because of release of insecticide stored in fat depots of the body. In addition to acute nervous signs there may be interrupted oestrus cycle, decreased weight gain, decreased appetite, decreased milk or egg production or reproductive problems.
2	Organophosphorus	Acute toxicity of organophosphates varies widely with compounds and species of animals and exposure. Local exposure: Exposure to vapour, aerosol or inhalation of organophosphorus results in nasal discharge, and wheezing. Exposure to eye results in lachrimation, constriction of pupil (miosis) and increased intraocular pressure with conjunctival hyperaemia. Systematic toxicity: Initial toxic symptoms include apprehension, hyperexcitation, and salivation leading to dyspnoea and open mouth breathing, diarrhoea, miosis, excess bronchial secretions, etc. muscle fasciculations, tremors, twitchings, spasms, hypertonicity causing a stiff gait or rigid stance. Animals fall on ground and show clonic or clonic-tonic convulsions. Central nervous signs may include ataxia, stimulation followed by depression (due to excessive stimulation), few minutes to several hours. Death mainly occurs due to respiratory failure from bronchoconstriction, excessive respiratory secretions, paralysis of respiratory muscles and central depression of respiratory center in medulla oblongata.
3	Carbamate	Acute toxicity: Clinical signs are similar to organophosphorus compounds but likely to be less severe or much shorter in duration. Chronic toxicity: Incoordination, ataxia, recumbancy and teratogenic effects.
4	Pyrethroids	Pyrethroids are classified as Type I and Type II on the basis of clinical signs on rats. Type I pyrethroids in rats produce, incoordination, hyperactivity, fine tremors progressing to gross whole body tremors, hyperthermia, etc. Type II insecticides produce nervous  syndrome in rats characterized by pawing and burrowing behaviour, salivation, coarse tremors progressing to sinuous writhing (choreothetosis) and clonic seizures. Mildy affected animals as well as those in the early stages of toxicosis often display hypersalivation, vomition, diarrhoea, mild tremors, hyperexcitability or depression. Severely affected animals can have hyperthermia or hypothermia, dyspnoea, severe tremors, disorientation and seizures. Death may occur within 24-72 hr due to respiratory failure. Dermal exposure may also produce allergic reactions i.e. dermatitis, burning and itching sensation in the skin and blisters formation.
5	Amitraz	Clinical signs include bradycardia, ataxia, depression, disorientation, vomiting, anorexia, diarrhea and seizures.