Organophosphate and Carbamate Toxicosis
Basic Information 
Definition
Organophosphates and carbamates are cholinesterase-inhibiting chemicals. Organophosphates include dichlorvos, ronnel, diazinon, chlorpyrifos, and phosmet, and carbamates include carbaryl, aldicarb, methomyl, and carbofuran. Many other organophosphates and carbamates exist.
Synonym(s)
Organophosphates have been called organic phosphates, phosphorus insecticides, and nerve gas relatives.
Epidemiology
Species, Age, Sex
Organophosphates and carbamates inhibit the enzyme cholinesterase, which is used by the nervous system of all mammals. All animals are affected, so there is no species, age, or sex predilection.
Risk Factors
Farm animals are at a higher risk because of the common use of these chemicals in a farm setting.
Clinical Presentation
Disease Forms/Subtypes
There is great variation in the types of clinical signs observed from an excessive dose of either of these groups of compounds. Many times these compounds are so potent that animals will be found dead with no previous signs of illness.
History, Chief Complaint
Acute death may be the chief complaint. The history often indicates exposure to these two classes of chemicals because insecticides were being used or animals gained access to these chemicals inadvertently.
Physical Exam Findings
• The clinical signs observed are associated with muscarinic, nicotinic, and central nervous system (CNS) stimulation.
• Muscarinic receptor–associated effects include salivation, lacrimation, urination, diarrhea, miosis (pinpoint pupils), and lung edema.
• Bradycardia, bronchoconstriction, and bronchorrhea may also be observed.
• Nicotinic receptor–associated effects are related to the stimulation of autonomic ganglia and skeletal muscles. The clinical signs of nicotinic stimulation include muscle twitching, tremors, and seizures.
• CNS stimulation can cause depression, hyperactivity, and seizures.
Etiology and Pathophysiology
• Organophosphates and carbamates inhibit the enzyme acetylcholinesterase, which is within nerve tissue and at neuromuscular junctions. Acetylcholinesterase destroys the neurotransmitter acetylcholine.
• When the acetylcholine concentrations increase in nerve tissue or at the neuromuscular junction, the acetylcholine receptors become overstimulated.
• The cholinergic system is widely distributed within the CNS and peripheral nervous system. There is a wide range in clinical signs when the cholinergic system is upregulated.
Diagnosis 
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