Production Animal Clinical Toxicology

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Organochlorine or Chlorinated Hydrocarbons

Chemicals

• DDT
• lindane
• aldrin
• dieldrin
• chlordane
• hepta-chlor
• and others

Sources

• were commonly used as insecticides but now use extremely restricted

Clinical Signs

• onset may occur within hours or days
• initially - apprehension
• hypersensitivity
• muscle fasciculation face and neck
• may progress to intermittent spasms of muscles
• increased salivation
• walk blindly
• marked terminal pyrexia - T exceeding 43EC
• effect on hypothalamus as well as muscular activity
• coma before death

Carbamates

Chemicals

• carbaryl
• promacyl
• methiocarb

Sources

• insecticides
• acaricides
• molluscicides
• herbicides

Clinical Signs

• generally similar to those for organophosphate toxicity
• signs may be more severe but animals may recover quickly

Xanthorrhea

Plant

Xanthorrhea spp. - grasstree, yucca, "blackboy"

Clinical Signs

• only cattle affected as only they can reach flowering spike
• urinary incontinence; urine may be red from ingested plant pigment
• tendency for hindquarters to lurch sideways always to one side
• if lose balance animal falls heavily on side, hence the common name "wamps"
• recovery occurs if animals removed before becoming severely affected

Cycads

Plants

Cycas spp. - zamia palms

Macrozamia spp. - burrawangs, wild pineapples

Bowenia spp.

Clinical Signs

• sheep, horses, pigs, man acute hepatic, gastrointestinal disorder frequently associated with ingestion of nuts
• cattle chronic neurological disorder possibly associated with ingestion of leaves
• proprioceptive defects in hindquarters
• inability to place legs precisely
• drag hindlimbs, knuckle over and fall on haunches
• may develop hindlimb paralysis
• will not recover

Nicotine Alkaloids

Plants

Nicotiana spp. (21) - wild, native tobaccos

Duboisia hopwoodii - pitchiri, pituri

Clinical Signs

• primary effect on neuro-effector junctions
• both stimulant and depressant effects
• confusion in clinical signs
• incoordination, ataxia, trembling
• unwilling to move, back arched
• appear to have defective vision
• when go down are initially on brisket, then may become laterally recumbent, violent kicking by all limbs may dig a considerable hole
• if on brisket and left alone may recover
• driving aggravates symptoms and increases risk of mortality

Flood Plain Staggers and Stewart's Range Syndrome

Plants

• a. Flood Plain Staggers (NSW)
• Agrostis avenacea - native blown grass, blowaway grass
• b. Stewart's Range Syndrome (SA)
• Polypogon monspeliensis - annual beard grass

Epidemiology

• cattle and sheep both affected
• similar to annual rye grass staggers
• nematode (Anguina spp.) carries a bacterium (C. toxicus) into seed head of Agrostis spp. or all parts of Polypogon spp. resulting in elaboration of tunicamycin-like toxins

Clinical Signs

• indistinguishable from annual rye grass staggers

Others

Marsilea drummondii (nardoo)

Cheilanthes tenuifolia (rock fern)

Pteridium spp.

• all contain thiaminase and can induce polioencephalomalacia

Centurea solstitialis (Yellow star, St. Barnaby's thistle)

• induces nigropallidal encephalomalacia in horses

Hypochaeris radicata (flatweed, cat's ear, false dandelion)

• possible cause of stringhalt in horses

Lupinus spp.

• in green stage contain quinolizidine alkaloids in seeds
• affects both horses and sheep, but not important
• sheep show staggering, convulsions, dyspnoea
• horses twitch subcutaneous muscles, are depressed, may lift forefeet high when walking

Claviceps paspali (ergot of paspalum)

• produces ergot alkaloids
• gangrenous ischaemia: rare and generally only in cattle
• neurological symptoms more common
• hypersensitive, nervous
• muscular tremors of both trunk and limbs
• incoordination, difficulty standing

Staccys arvensis (stagger weed)

Malva parviflora (small-flowered mallow)

• both cause staggers in cattle, sheep horses

Gomphrena celosioides (gomphrena weed, soft khaki weed)

• horses only
• incoordination, dragging of toes