What are the general characteristics of organophosphates and carbamates?
-wide variety of products
-some products are so safe they are directly applied to animals
-others are considered weapons of mass destruction due to danger levels
What is the pathophysiology of OP/carbamate toxicity?
-inhibit acetylcholinesterase enzymes in nervous and muscle tissue
-effect is excess ACh and overstimulation of post-synaptic neuron or muscle
-OP induces irreversible AChE binding; must produce all new AChE to recover
-carbamates bind AChE reversibly
What are the muscarinic clinical signs of OP toxicity?
-salivation*
-lacrimation*
-urination*
-diarrhea*
-miosis
-vomiting
-colic
-dypsnea
What are the nicotinic clinical signs of OP toxicity?
-muscle fasciculation
-weakness
What are the CNS signs of OP toxicity?
-nervousness
-ataxia
-apprehension
-seizures
What causes death due to OP toxicity?
-respiratory collapse
-continuous seizures
How is OP toxicity diagnosed?
-history and clinical signs
-measurement of AChE inhibition activity in blood or brain tissue
-measurement of OP/CM compounds in feed, stomach/rumen contents, or tissues
What are the two main treatments for OP toxicity?
*atropine:
-muscarinic ACh receptor blocker
-doses repeated to effect
-stop dosing when pupils re-dilate, salivation stops, and animal brightens
*2-PAM:
-reactivates AChE
-want to give as soon as possible
-best used for OP toxicity only; not CM
What other treatments can be used in the case of OP toxicity?
-decontamination; stomach evacuation if under 2 hours, activated charcoal if over 2 hours
-bathing in dermal contact cases
-diazepam to reduce muscle tremors and seizures
-anesthesia and barbiturates to control seizures
-ventilation
What are the general characteristics of pyrethrins/pyrethroids?
-come from chrysanthemums
-pyrethrins are natural derivatives; pyrethroids are synthetic derivatives
-pyrethroids are more toxic
-typically combined with piperonyl butoxide
-oral route is worse than topical
What is the pathophysiology of pyrethroid toxicity?
-force sodium channels to remain open longer
-sodium channels kept open produce hyper-excitable neurons
-chloride, calcium, and GABA channels are also impacted
What are the clinical signs of pyrethroid toxicity?
-salivation
-vomiting
-hyperexcitability
-muscle fasciculation
-weakness
-seizures
-dyspnea
-recumbency
-death
Which systems can be affected by chronic pyrethroid exposure?
*pre-pubertal females:
-disruption of reproductive endocrine function
-disruption of reproductive development
*adult bulls:
-poor sperm production in bull studs
How is pyrethroid toxicity diagnosed?
-history and clinical signs
-measurement of insecticide residues in tissue or blood
What is the treatment for pyrethroid toxicity?
-most signs resolve with time
-symptomatic/supportive care; esp. seizure control
-activated charcoal
-avoid oil-based oral treatments
-bathing for dermal exposures
What are the characteristics of organochlorines?
-among the most ecologically toxic chemicals ever used
-most are banned from use in the US; may still be able to get lindane lice treatment
-class that contains DDT
What is the pathophysiology of organochlorine toxicity?
-general CNS stimulants
-alter the polarization of the neuron and reduce the excitation threshold; easier for neuron to fire
-prevent GABA from binding its receptor; prevents inhibition of excitatory signals
How do organochlorines affect birds?
bioaccumulate in fat and affect egg shell thickness
What are the clinical signs of organochlorine toxicity?
-salivation
-vomiting
-hyperexcitability
-ataxia
-tremors
-apprehension
-seizures
-abnormal movements
How is organochlorine toxicity diagnosed?
-history and clinical signs
-measurement of toxin in blood or tissue
-fat biopsy is a relevant sample due to accumulation
What is the treatment for organochlorine toxicity?
-symptomatic and supportive care
-seizure control
-activated charcoal
-bathing and clipping hair
-REPORT; OCs are tightly regulated in US
What are the characteristics of neonicotinamides?
-used in flea/tick medications and crop applications
-class of insecticide considered safe for non-target species
-includes imidacloprid, dinotefuran, and nitenpyram
What is the pathophysiology of neonicotinamide toxicity?
binds post-synaptic nicotinic receptors
What are the clinical signs of neonicotinamide toxicity?
-neuro. signs
-depression
-tremors
-impaired pupillary function
-ataxia
-hypothermia
-death
-hepatotoxicity
