Large Animal Toxicity Flashcards
What would you get on a SOAP assessment for acorn poisoning?
S: Depression, anorexia, bloat (rumen atony)
O: constipation (initially), brown urine, dehydration, foetid tarry diarrhoea (within 4-7 days)
A: Renal damage and haemorrhage, Mucoid and haemorrhagic enteritis, Protein loosing enteropathy
P: Rule out parasites (type 1 ostertagiasis) and mucosal disease (clinical signs). Bloods – show renal failure and Urinalysis –proteinuria, glycosuria and haematuria
No treatment – support with IVFT
What would you get on a SOAP assessment for bracken poisoning?
S: Anorexia, weakness, depression, lethargy, Pain on urination, Straining to urinate, halitosis
O: Haemorrhages from nasal passages/vagina, sudden death, chronic weight loss, diarrhoea
A: Bone marrow suppression, bladder tumours
P: Sudden death – check for anthrax. Bloods – pancytopenia. Support +/- transfusion.
Bladder- rule out pyelonephritis and babesiosis. Haematuria
What would you get on a SOAP assessment for oxalate poisoning?
S: Dull, bloat, muscular weakness, Inappetance, abdominal discomfort
O: Muscle fasciculation’s, constipation, Mild tachycardia, blood and crystals on preputial hairs.Abdominal distention (bladder rupture) or ventral oedema (urethra rupture)
A: Hypoglycaemia, Crystallisation of calcium oxalate in kidneys (tubular necrosis) and vasculature (vascular necrosis and haemorrhage), Depletion of ionised Calcium, hypocalcaemia.
P: Bloods –Calcium, kidney function, and electrolytes. Urinalysis –crystals, Treatment – calcium i/v and s/c. A mix of dicalcium phosphate and sodium chloride (1:3) may bind oxalate in the rumen.
Urolithiasis covered in lectures
What would you get on a SOAP assessment for brassica poisoning?
S: pallor, weakness, jaundice, Mental retardation of newborn, higher mortality when cold, Exercise intolerance, collapse, panting, haemoglobinuria, , tachycardia, diarrhoea, collapse and death
O: Wiry/fluffy coat of newborn, enlarged thyroid, Colic, staggering/drunken gait, cyanosis –darkened mm, tachycardia. Abortion storms, Dimethyl disulphide – oxidant.
A: Hypothyroidism and goitre. Fetus most sensitive- when mothers grazes in last 1/3 of pregnancy, Nitrate poisoning – forms methaemoglobin.
Ischaemia
P: Bloods transfusion and supportive
Iodine supplement- limited benefit
Test- serum T4 (poor guide), plasma organic iodine
Test – methaemoglobinuria and methaemoglobinaemia
1% Methylene blue i/v at 2-4mg/Kg repeated to effect
- What problems do you face in the diagnosis and treatment of these conditions in large animals?
· Need a good history – know what they have eaten
· Limited funds for testing
· Treatment often not effective so high losses
NSAIDS:
What are the toxic side effects?
What are the mechanisms of action?
What are the at risk groups?
What are the implications?
- Ischaemia and necrosis of the renal papillae and medulla by inhibiting PG and casuing vasoconstriction.
Repeated exposure leads to irreversible necrosis of the medullary loops of Henle and their associated capillaries.
GI ulceration – inhibit the secretion of gastric acid and promoting mucus, due to PG inhibition
- Inhibit Cox-1 and/or COX-2 causing inhibition of PG. See image below
- Renal disease patients, hypovolemic or dehydrated
- Don’t use in animals with prior renal disease.
AMG (aminoglycosides):
What are the toxic side effects?
What are the mechanisms of action?
What are the at risk groups?
What are the implications?
- Renal nephrosis - through inhibition of phospholipases leading to lysosomal dysfunction and lysis in the renal tubules and proximal tubule epithelium.
Nephrotoxicity – inhibit PG. Ototoxic
can potentiate competitive neuromuscular blocking actions
- Disturbance of bacterial protein synthesis through binding to the 30S part of the ribosome. Results in a reduction in the production of beta-lactamase by bacteria, - act synergistically with beta-lactam antibiotics.
- Renal disease – accumulates if function impaired.
Don’t use if susceptible to changes in renal perfusion/increased susceptibility to nephrotoxicity.
Dehydration/hypovolaemia.
Don’t use with NSAIDs – inhibit renal RG synthesis.
Avoid other nephrotoxic agents.
- Don’t use with NSAIDs
What is the mechanism involved in nephrotoxicity in equine rhabdomyolysis, white muscle and exertion muscle myopathy and in some snake bite reactions?
· Myoglobin build up
· renal vasoconstriction - Myoglobin is a potent inhibitor of the vasodilator nitric oxide and may trigger intrarenal vasoconstriction and ischemia in patients with borderline renal hypoperfusion . Besides, severe muscular injury can, for unknown reasons, activate the endotoxincytokine cascade, thus eliciting renal vasoconstriction.
· Once the myoglobin molecule is filtered by the glomerulus it enters the proximal tubular cells and is taken up by lysomes at acid pH. The heme pigment then splits into its globulin and ferrihemate components. Ferrihemate is transported out of the tubular cell at the expense of ATP. The tubular cell, thus is injured due to renal ischemia, hypoxia and a critical reduction of ATP stores
intrarenal cast formation - myoglobin interacting with Tamm-Horsfall protein creates casts (more vigorously in an acidic environment), obstructing the tubuli, along with sloughed destroyed cells from tubular necrosis
A farmer is considering extending the grazing season by using autumn/winter brassicas as a forage crop for the grazing cows. She asks you for your advice as to the likely problems and how they could be avoided. Identify the major problems associated with brassica feeding and the management strategies you would advice to avoid them.
· Nitrate poisoning - Prevention relates to avoidance and gradual introduction of suspect crops with adequate alternative feeds (especially cereal based feeds) available to prevent hungry animals gorging on high nitrate material. Forages can be readily tested for levels of nitrate and levels below 0.5% are safe for all classes of animal, levels between
· Goitrogens – avoid grazing in the last 1/3 of pregnancy, fetus most affected
· Dimethyl disulphide – only really if fed 75% Kale for at least 3 weeks, so mix feed or remove before 3 weeks.
