Lead Flashcards
Where do cattle often get into lead?
-batteries
-weights
-toys
-lead shots
-ceramic glaze
-industrial products
-historic use: pipes, paint, gasoline, lead arsenate pesticides
Lead mechanism in cattle
Multisystemic poison
1. targets CNS (astrocytes, neurons, CNS epithelial cells) =cerebral hemorrhage and edema
- disrupts Ca homeostasis
- disrupts NTs
Toxicokinetics of lead in cattle
- 90% bound to RBCs
*submit fresh whole blood for Dx - unbound lead goes to liver, kidneys, brain, spleen, bone, teeth
**long term storage in bone - excretion in feces, milk
- Transplacental transfer
Lead poisoning in cattle
*most common poisoning in grazing cattle
-herd level problem
-linked with management= lead from batteries on pasture but pre 1970s from oil
Epidemiology of lead poisoning in cattle
Occurs when turnout on pasture or recent pasture change
*May- July has highest cases
*multiple cases/herd
*more cases in young but could be bias submissions
Toxicity in calves vs cattle
Lethal dose lower in calves vs adults
*calves have higher GIT absorption, they are more curious, and because they are smaller they have better accessibility
How much lead in single car battery?
20lbs (9kg)
Clinical features of lead poisoning in cattle
-found dead
-acute or subacute neuroexcitation: bruxism, hypersalivation, jaw clamping, blindness+ aimless wandering (head pressing), circling, focal seizures/whole body convulsions, odd behaviour away from herd
4 groups of lead poisoning in the herd
- dead or dying
- subacute poisoning
- asymptomatic but exposed
- asymptomatic and not exposed
Physical exam findings in lead poisoning in cattle
- Blindness (no menace +/- PLR) =polioencephalomalacia
- GI hypomotility or atony= dehydration, anorexia
- Tachycardia, dyspnea
- +/- hyperthermia
Management of lead toxicity in cattle
- Clinical signs indicate polio so treat:
-thiamine = will not work for lead
-if lead suspected= euthanasia - Subacute= try chelation therapy
*issue is not always available, economically feasible to treat, and chelation will not work/bind to lead in reticulum or bone
Diagnosis of lead toxicity in live cattle
Whole blood= purple or green top tubes!
-lead analysis
Diagnosis of lead toxicity in dead cattle
Lead analysis of liver, kidney, rumen contents, and brain
Necropsy findings in lead toxicity in cattle
Non specific
-check reticulorumen for lead particles!! (#1)
-enteritis
-petechial hemorrhage
*calves have thymic hemorrhage and pale muscles
-if unsure submit brain
-differentials for polioencephalomalacia (cerebral cortical necrosis on histology!)
Differentials for lead toxicity in cattle
Herd management for lead toxicity
Must test the entire herd because many cattle will be asymptomatic but have significant amounts of lead
-Reportable disease in BC, AB
-Find source and prevent access
-serial blood testing of asymptomatics
*lead half life is mths to yrs because storage in bone and particles in reticulum
Lead toxicity of cattles impact on public health
-highly unlikely of acute lead poisoning from animal tissues (*there are min levels of lead in meat, milk and offal)
-low chronic exposures in children= cognitive deficits
Where do companion animals become exposed to lead?
-Leaded paint (old houses, soil, home renovations)
-water
-toys, metal trinkets, gold balls
-captive birds chewing on lead solder
Clinical signs of lead toxicity in companion animals
Tend to be subchronic=lower amounts ingested than from batteries
-GI (anorexia, vomiting, diarrhea, weight loss)
-CNS (dull, anxious, bark change, abnormal stance or behavious, tremors, seizures)
Clinical pathology of lead toxicity in companion animals
Basophilic stippling = aggregation of RNA in cytoplasm (CHRONIC issue only)
and
Siderocytes= impaired heme synthesis
Management of lead toxicity in companion animals
-remove source of lead (endoscopy)
-supportive care
-chelation therapy for symptomatic patients
Diagnosis of lead toxicity in companion animals
-history of home renovations
-radiograph ID of lead in GIT or metaphyses
-elevated blood lead
-consider lead in cases of non specific GI signs
Metal toxicosis in pet birds
From chewing on things in environment
-zinc of lead cages, toys, bowls, pennies, paint etc.
Clinical features of pet bird lead toxicity
GI (anorexia, regurg, diarrhea)
Neuro (ataxia, seizures, blindness)
Feather plucking
PU/PD
Green tinged urates
Anemia, basophilic stippling
Management of metal toxicosis in pet birds
-symptomatic and supportive care
-surgical or endoscopic removal of source
Diagnosis of metal toxicosis in birds
-radio opaque material in ventriculus
-whole blood lead
-check levels in liver and kidneys
Lead poisoning in predatory birds
High incidence of lead in eagles and raptors
-they scavenge on carcasses and ingest lead ammunition
*can result in acute neuro signs and death OR chronic impaired ability to perform normal behaviours= emaciation and death
