Ionophore Toxicosis Flashcards
What can ionophores be used for in cattle, poultry and goats?
Anticoccidial
What can ionophores also be used for in cattle?
Growth promoter feed additive
Which ionophore is approved to improve efficiency of milf production in dairy cattle in the US?
Monensin
What are 2 things ionophores can reduce in ruminants?
- Bloat
- Rumen acidosis
What can ionophores prevent in cattle?
Tryptophan-induced atypical bovine pulmonary emphysema
What are 6 examples of ionophores?
- Monensin
- Lasalocid
- Salinomycin
- Narasin
- Semduramicin sodium
- Laidlomycin propionate potassium
Are ionophores soluble in water?
In organic solvents?
Oils?
- Slightly
- Yes
- Yes
How do ionophores cross cell membranes?
Form lipid-soluble complexes with polar cations (Na+, K+, Ca2+, Mg2+)
Which is the most commonly found ionophore?
Monensin
What is the most common source of ionophore toxicity in chickens, cattle and swine?
Eating feeds that contain more than the recommended levels of ionophores.
What is the most common source of ionophore toxicity in horses, sheep and dogs?
Eating feeds with added ionophores, accidentally or intentionally.
Which animals are susceptible to ionophore toxicity?
All animals
Which species is the most sensitive to ionophore toxicosis?
Which is intermediate?
Which is least?
- Most: horses
- Intermediate: cattle
- Least: poultry
Concurrent administration of what 5 drugs can increase the toxicosis of ionophores?
- Tiamulin
- Chloramphenicol
- Erythromycin
- Sulfonamides
- Cardiac glycosides
Ruminants absorb about 50% but monogastric animals absorb most of which ionophore?
Monensin
What type of blood and tissue levels are seen with monensin?
Relatively small
Does monensin accumulate in tissues of animals when given in high doses?
No
Where and how are ionophores metabolized?
Excreted?
- Rapidly by P-450 oxidative demethylation enzymes in the liver
- Mainly in bile
Why are ionophores metabolized more slowly in horses compared to other species?
Horses have the lowest oxidative demethylase levels compared to other domestic species.
What do ionophores disrupt?
Transmembrane electrochemical gradients
What are the main targets of ionophores?
What are 3 examples of these targets?
- Mitochondria of highly energetic tissues
- Myocardium, skeletal muscles, kidney
What does the influx of the sodium-ionophore complex cause?
Increasing intracellular sodium accompanied by increasing intracellular calcium
Does ionophore toxicosis lead to increased or decreased cytoplasmic calcium levels?
Increased
Why does cell death occur with ionophore toxicosis?
Disrupting of homeostatic mechanisms
Catecholamine release from ionophore toxicosis results in what?
Oxidation products and free radicals causing sarcolemmal membrane damage.
What are 4 examples of excitable cell types where disruption of ion concentrations resulting from ionophore toxicosis can alter their functions?
- Neurons
- Myocardium
- Skeletal muscles
- Smooth muscles
Is the onset of ionophore toxicosis in horses slow or rapid?
Rapid
Anorexia, profuse sweating, colic, depression, incoordination, hyperventilation, tachycardia, tachyarrythmias, prostration and death can result from what type of toxicosis in horses?
Ionophore toxicosis
Which of the following is not a sign of ionophore toxicosis in cattle: anorexia, diarrhea, depression, tachycardia, labored breathing, ataxia, prostration, death
Tachycardia
What are 2 clinical signs of ionophore toxicosis specific to poultry?
- Resting on the knees with wings and leg directed outward
- Decreased egg production
Ataxia, muscle weakness of hind limbs, respiratory paralysis, dysuria, constipation and depression are clinical signs of ionophore toxicosis seen in which species?
Dogs
What is main lesion seen in horses with ionophore toxicosis?
Another lesion that can be seen?
- Cardiac muscle lesions
- Skeletal muscle lesions
Skeletal muscle lesions are the main lesions seen with ionophore toxicosis in what 3 species?
- Sheep
- Swine
- Dogs
Both skeletal and cardiac muscle lesions are seen with which 2 species?
- Cattle
- Poultry
What do chemical analysis methods or ionophores detect?
Ppb levels
What is the best type of sample for ionophore detection?
What are 3 other possibilities for samples?
- Feed
- GI contents, liver, feces
With ionophore toxicosis, what 4 enzymes can have elevated levels?
- Creatine phosphokinase (CPK)
- Aspartate transaminase (AST)
- Lactic dehydrogenase (LDH)
- Alkaline phosphatase ( ALP)
What 2 electrolyte levels are decrease during the first 12 hours of ionophore toxicosis?
What electrolyte level has no change?
- Ca2+, K+
- Na+
What happens to PCV during ionophore toxicosis?
Increases
Diagnosis of ionophore toxicosis is made with what 4 elements?
- History (feed-related problem)
- Clinical signs
- Lesions
- Lab diagnosis
What does a general differential diagnosis for ionophore toxicosis include?
Other myopathy and neuropathy conditions
What are 3 differential diagnoses are included with horses?
One with cattle?
- Horses: colic, blister beetle ingestion (cantharidin toxicosis), azoturia
- Cattle: Vit E/selenium deficiency
What are 3 plants that can cause skeletal muscle signs similar to ionophore toxicosis?
- Coffee senna
- Coyotillo
- White snakeroot
What are 4 plants that can cause cardiotoxic signs similar to ionophore toxicosis?
- Oleander
- Taxus spp.
- Milkweed
- Vetch
Nutritional myopathy, coffee senna toxicosis, botulism, Na+-water deprivation toxicosis, mycotoxicosis, round-heart disease and downer syndrome (viral arthritis) are all differential diagnoses of ionophore toxicosis for which species?
Poultry
Is there any specific antidote for ionophore toxicosis?
No
What should be done right away with ionophore toxicosis?
Remove medicated feed
What are 3 things that can be given to decrease the absorption of ionophores?
- Activated charcoal
- Mineral oil
- Saline cathartics
What are 2 things that can be given to correct hypovolemia and support cardiovascular and renal functions with ionophore toxicosis?
- IV fluid
- Electrolyte therapy
How long should cardiac function be monitored with ionophore toxicosis?
Several months
T/F: It is ok for horses to resume normal work 2 weeks after ionophore toxicosis.
False - Horses should not be ridden or stressed for several months.
What may decrease muscle damage from ionophore toxicosis, especially in cattle and swine?
Vitamin E/selenium
Horses that survive ionophore toxicosis may suffer from what?
Myocardial scarring and necrosis
Will horses that survive ionophore toxicosis always fully recover?
No, horses may not reach previous performance levels.
