25 – Arsenic and Mercury Flashcards
1
Q
What are the different forms of mercury?
A
- Elemental metal mercury
- Inorganic salts: mercuric chloride
- Organic mercury: methyl mercury
*in environment: most is converted to methyl mercury and bioconcentrated in the biota
2
Q
Mercury: absorption
A
- Metal mercury: well absorbed by inhalation
- Inorganic: relatively poor
- Organic: well absorbed through GIT and skin (lipophilic in nature)
3
Q
Mercury: metabolism
A
- Most forms are converted to inorganic forms, but ultimately to methyl mercury in the environment
4
Q
Mercury: distribution
A
- Liver and kidney accumulate significant quantities
- Fetus acts as ‘sink’ and will accumulate excessive toxic amounts sparing the mother from clinical disease
5
Q
Mercury: excretion
A
- Inorganic: urine
- Organic: bile and feces
6
Q
What is mercury’s mechanism of action?
A
- Inorganic: causes corrosive damage and tissue necrosis
o Binds with sulfhydryl groups reducing metabolic activity and causing degenerative change - Organic: interferes with metabolic activity causing degenerative changes, but has NO corrosive action
7
Q
What are the 2 syndromes seen clinical with mercury?
A
- Inorganic: gastric intestinal and neurological syndrome
- Organic: only neurological
8
Q
Mercury: GIT signs
A
- *inorganic only
- Anorexia
- Vomiting
- Salivation
- Diarrhea
- Stomatitis, ulcer
9
Q
Mercury: CNS signs
A
- Ataxia, tremors
- Blindness
- Terminal convulsions
- Depression
- Paresis or paralysis
10
Q
Mercury: kidney signs
A
- Hematuria
- Proteinuria
- Uremia
11
Q
Mercury: cardio-vascular signs
A
- Epistaxis
- Cyanosis
- Dyspnea
12
Q
Mercury: skin signs
A
- Alopecia
- Keratinization
13
Q
Mercury: GIT pathology
A
- Gastroenteritis, stomatitis
- Mucosal hemorrhage and edema
- Ulcers
14
Q
Mercury: kidney pathology
A
- Interstitial nephritis
- Tubular necrosis
15
Q
Mercury: lung pathology
A
- Edema
- Bronchitis
- Hydrothorax
16
Q
Mercury: liver pathology
A
- Mild necrosis
17
Q
Mercury: CNS pathology
A
- Encephalomalacia
- Degeneration: neurons, myelin
18
Q
What are the DDx for mercury: GI signs?
A
- Lead
- Salt
- Inorganic arsenic
- OP/carbamate
- Vit D
- Chlorinated hydrocarbon insecticides
- Herbicides
- Mycotoxins (T-2 toxin)
- Lincomycin
19
Q
What are the DDx for mercury: CNS?
A
- Organic arsenic
- Lead
- Salt
- Chlorinated hydrocarbon insecticides
- OP/carbamate
- Blue green algae
- Urea
20
Q
What are the DDx for mercury: kidney?
A
- Oxalates
- Oak
- Cadmium
- Lead
- Arsenic
21
Q
How do you treat mercury poisoning?
A
- *Long half life (70days) and degenerative changes in many organs limits treatment success
- Sodium thiosulfate
- Egg whites
- Milk
- Astringents
- Fluids
- Chealtors (penicllamine or British antilewisite) may be effective
22
Q
What are the economics to consider with Mercury?
A
- Insidious nature and irreversible effects LIMITS livestock treatment options
- Extended milk and meat residues
- Highly teratogenic nature
- *usually do euthanasia and disposal
**see it more in wildlife (ex. carnivorous fish)
23
Q
*Arsenic: inorganic vs. organic
A
- Organic
o Low mortality
o No GIT
o CNS present - Inorganic
o Near 100% mortality
o Severe GIT
o May or may not have CNS (usually die before hand)
24
Q
What are some sources of arsenic?
A
- Dips, sprays
- Herbicides
- Heart worm medication
- Feed additive: arsanilic acid
25
Arsenic: absorption
- Readily through skin or GIT
26
Arsenic: distribution
- Energy rich tissues: liver, kidney, GIT epithelium
- Chronic exposure: high levels in hair and hoof
27
Arsenic: metabolism
- Inorganic forms: usually methylated
28
Arsenic: excretion
- In bile or urine depending on form
- Half-life: only a few days
29
What is arsenic’s mechanism of action?
- Inorganic: chemical irritation and tissue degeneration
- In general: metabolic poison resulting in impaired cellular respiration and uncoupling of oxidative phosphorylation
- Degenerative changes develop in MANY organ systems with high-energy requirements
30
Inorganic arsenic: acute syndrome
- High mortality
- Sudden onset
- Vomiting
- Abdominal pain
- Weakness
- Ataxia
- Recumbency
- Shock
- Diarrhea
- Death within 3-4 hours
- Terminal convulsions may be observed
31
Inorganic arsenic: subacute syndrome
- Range 2-7 days
- More neurological malfestations present
o Muscle tremors
o Incoordination
o Clonic convulsions
o Hind end paralysis
- GIT
o Vomiting, diarrhea, salivation, grinding teeth, anorexia, thirst
- *usually dehydrated and in shock
32
Inorganic arsenic: chronic
- Same systems affected, but vague manifestations
- Unthrifty animals
- Poor growth
- Indigestion
- Reduced milk production
- Abortion
- Buccal cavity ulceration
33
How do you diagnosis arsenic?
- Clinical manifestations (GIT and neurological)=inorganic
- Analysis liver, kidney, hair or food samples
- Severe gastroenteritis and degenerative changes in most organ systems may be evident
34
How do you treat arsenic poisoning?
- At high levels=animals die
- Sodium thiosulfate
- British anitLewisite
- Astringest
- Fluid therapy=essential for shock
- *selenium in small animals=antagonizes arsenic (don’t give too much)
35
Inorganic arsenic: DDx for CNS
- Lead
- Mercury
- Salt
- Selenium
- Chlorinated hydrocarbon insecticides
- Ops
- Cyanide: bright red blood
- Nitrate/nitrite: chocolate brown blood
- Blue green algae
36
Inorganic arsenic: DDx for GI
- Urea
- Lead
- Selenium
- OP/carbamate
- Chlorinated hydrocarbon insecticides
- Mycotoxins (T-2 toxin)
- Many plants
- Herbicides
37
Inorganic arsenic: chronic poisoning DDx
- Copper deficiency: molybdenum toxicity
- Selenium
- Fluorosis
- Ergot
- PCB (polychlorinated bicanols?)
38
Organic arsenic: 3 forms
- *less toxic
- Arsanilic acid
- Roxarsone
- Nitrophenylarsonic acid
- *improper feed formulation is the source of the problem
o Usually rapidly eliminated and limits food residue concerns (creates diagnostic problems with tissue analaysis)
o About 75% is eliminated within 24hrs after exposure is terminated
39
Organic arsenic: clinical manifestations
- Depending on level of food: may take weeks to develop
- GI tract is not affected so animals continue to consume food until late stages of the disease
40
Acute poisoning: organic arsenic
- With about one week
- Incoordination, ataxia
- Paralysis
- Blindness
- *not anorexic and NO GI signs
- *chronic: similar but to lesser degree and failure to gain weight
41
How do you diagnosis organic arsenic poisoning?
- History of exposure and clinical manifestations (neurological)
- Feed analysis recommend
- Interpret tissue analysis with caution due to arsenic being rapidly excreted
- Animals will make an UNEVENTFUL recovery if feed is removed EARLY
42
Organic arsenic: DDx
- Methyl mercury (take off feed, if recover in a few days=arsenic)
- Salt
- 2.4-D
- Organophosphates
- TOCP
- Chronic selenium
- Plants: lupines, Zygadenus
43
Organic arsenic economics
- If poisoning recognized early and feed withdrawn=animals will recover rapidly and can be shipped in future since withdrawal times are VERY SHORT
