Lead Flashcards
What is the most common poisoning of livestock?
lead
- but it affects all species
what is the cause of the biochemical or subcellular effects of lead?
affinity of lead for SH (sulfhydryl) or imidazole groups
The binding of lead to various macromolecules impair which functions?
enzymes - substrate
mitochondria - decrease ATP
reproduction - chromosomal damage
immune system - immunosuppression
In which organ systems are the cellular and clinical affects most aparent?
GI
nervous
hemopoetic
What are the GI effects of lead?
irritation, gastroenteritis, rumestasis in cattle
diarrhea/constipation
What are the nervous effects?
encephalopathy
- capillary damage causes hemorrhage and congestion in the brain followed by edema and malacia
blindness and peripheral nerve degeneration
no direct harm to brain
affects vascular supply –> edema and swelling
What are the hemopoetic effects?
anemia reduced iron uptake RBC fragility heme synthesis altered by enzymes containing SH
What are the effects on the kidey?
degenerative changes
- tubular necrosis, nephritis, fibrosis and yaline degen
- acid fast inclusions bodies are present
What are the effects on the liver?
mild degen
little clin significance
What are the MSK effects?
osteoporosis
- common in sheep
What are the affects on the resp system?
impaired neuro = impaired swallowing mech and cause aspiration pneumonia
What are the acute and subacute syndromes characterized by? two general systems?
GI and neuro
How long does the acute syndrome last? which age?
lasts 24h
usually younger animals
one or two in herd
What are the clinical signs of acute poisoning?
behaviour
- mania, frenzy, charging fences, bellowing, head pressing
locomotor
- staggering an muscle tremors
nervous phenomena
- champing jaws, blindess, snapping eyelids
- hyperesthesia
- intermittent tonic-clonic convulsions
- opisthotonus
GIT
- frothing, salivation (impaired swallowing
- rumen stasis
- abdominal pain
- abnormal eructation
How long does the subacute poisoning last? which age?
adults typically 3-4d
What are the clinical signs of subacute poisoning?
behavioural
- dullness
- head pressing
locomotor
- abnormal gait
- incoordination, muscle tremors, staggering, often stand immobile, occasionally circle
nervous
- blind, depression, hyperesthesia, head bobbing, convulsions absent
GIT
– grinding teeth, rumen stasis, salivation, anorexia, diarrhea/constipation, abdominal pain
What is the main difference between subacute and acute?
lasts longer and no convulsions with subacute
What are signs/type is specific to sheep?
osteoporosis
usually subacute
What type and signs are specific to horses?
chronic
- colic, pharyngeal paralysis (roaring)
- aspiration pneumonia
- no convulsions
What type and signs are specific to pigs?
primarily GIT - vomiting
few CNS signs
what type and signs are specific to dogs/cats?
similar to pigs
- vomiting
- hyperexcitability
- convulsions
- altered hysterical bark
What are some sources of lead?
paint, oil, lubricants, lead toys, lead shot, batteries, used crankcase, old shingles, industrial contam
What is the absorption and distribution?
higher absorption in young animal
cumulative half life is many month enters blood distributes rapidly to liver and kidney (1d) displace Ca does not accumulate in brain
gut>blood>kidney>liver>bones
What Vitamin from sun can increase absorption?
Vit D
What is the excretion?
kidney
milk - minor
Why are young animal more susceptable?
low iron milk diet
iron competes with lead
What can be submitted antemortem to confirm Dx?
heparinized blood (WHOLEBLOOD) in RBC
rumen contents
fecal contents
What can be submitted postmortem?
liver and kidney (best)
rumen, fecal (variable)
brain (poor)
What is detected on clin path?
anemia basophilic stippling increased ESR anisocytosis hypochromia leptocytes altered enzymatic activity
kidney damage
- proteinuria, glucouria
What else can be seen diagnostically?
increased radiographic density
growth plates in bone
stomach or rumen contents
What is the treatment for food animals?
discouraged
- food safety
- prognosis
- potential repro problems
What are some treatment chelation therapys?
penicillamine (oral) british antiLewistie IV - short acting, lipid soluble - penetrate CNS Calcium EDTA (IV) - no longer approved for livestock succimer (oral) - best for dogs but hard to get
What other treatment options are there for lead?
thiamin (IV) - chelates and cheap MgSO4 (oral) - acts as laxative and binds lead sedation rumen lavage rumenotomy zinc supplementation rumen transplant
What is the best treatment?
calcium EDTA + thiamin (IV)
What is used for supportive therapy?
force feeding
oral fluids
mannitol (helps reduce swelling in the brain)
edema
What is the epidemiology of lead?
young animals in season when batteries are changed (harvesting)
- may and august
what is the economic implications of lead?
expensive in cattle meat and milk residues lack of approved medications reportable disease in alberta - must cull
