Phenoxy derivatives of fatty acids (2,4-D)

Question 1

3 sources of exposure

Answer 1

• Accidental ingestion of concentrates or sprays (cattle)
• Grazing freshly sprayed pastures (cattle)
• Access to freshly sprayed lawns (pets)

Question 2

T/F: Generally, srayed forages in the recommended concentrations do not cause poisoning

Answer 2

TRUE

Question 3

What do phenoxy derivatives of FAs do to plant metaboisms?

Answer 3

Alter the metabolism of plants–> increases their toxicity by increasing accumulation of nitrate or cyanide

Question 4

T/F: Phenoxy derivatives of FAs also decrease palatability of some poisonous plants, decreasing poisoning

Answer 4

FALSE–they increase palatability of some poisonous plants, increasing poisoning

Question 5

Are phenoxy derivatives of FAs stable in the environment?

Answer 5

NO

Question 6

Are phenoxy derivatives of FAs degraded by rumen flora, thus altering it?

Answer 6

Nope

Question 7

T/F: Phenoxy derivatives of FAs are an irritant to GI mucosa

Answer 7

TRUE

Question 8

Which species are the most susceptible to phenoxy derivatives of FAs?

Answer 8

Cattle and dogs

Question 9

T/F: Cattle are more sensitive to phenoxy derivatives of FA’s than other species

Answer 9

FALSE–it’s dogs

Question 10

What does toxicity depend on?

Answer 10

Species and duration of exposure

Question 11

What’s the acute oral LD₅₀ in dogs?

Answer 11

Approximately 100mg/kg

Question 12

Where are phenoxy derivatives of FAs readily absorbed from? Where are they poorly absorbed from?

Answer 12

• Readily absorbed from GI tract or by inhalation
• Poorly absorbed from skin

Question 13

Where are phenoxy derivatives of FAs distributed?

Answer 13

All over body, including liver, kidney, and brain

Question 14

T/F: Meat residues in cattle and sheep are likely even with exposure to low concentrations of 2,4-D

Answer 14

FALSE–residues unlikely unless exposed to very high concentrations

Question 15

What are the half lives of phenoxy derivatives of FAs?

Answer 15

Generally short (few hours), but longer in dogs (up to 3-4 days)

Question 16

How is 2,4-D mainly metabolized? How is it excreted?

Answer 16

• Metabolized mainly by hydrolysis
• Excreted mainly unchanged in urine by tubular secretion

Question 17

T/F: Alkalinization of urine enhances renal excretion

Answer 17

TRUE

Question 18

Mechanism of action (3)?

Answer 18

• Irritation of GI mucosa
• Affect skeletal muscle membranes in dogs
• Uncouple oxidative phosphorylation, and depress ribonuclease synthesis (unknown relationship to clinical signs)

Question 19

What are the general clinical signs of 2,4-D toxicity?

Answer 19

Generally non-specific; mainly GI and NM

Question 20

Clinical signs in ruminants?

Answer 20

• Anorexia, rumen atony, may be bloat and diarrhea and ulcers in buccal mucosa
• Depression, muscle weakness and emaciation with no convulsions

Question 21

Clinical signs in dogs?

Answer 21

• Anorexia, vomiting, bloody diarrhea
• Myotonia and weakness of the muscles especially posterior muscles and ataxia w/ rigidity of skeletal muscles
• At high doses, onset is rapid (< 1 hr), opisthotonos may occur and posterior paralysis in addition to severe GI signs

Question 22

Clinical signs in swine?

Answer 22

Vomiting, diarrhea, muscle weakness and depression

Question 23

Various lesions of 2,4-D toxicosis?

Answer 23

• Nonspecific
• Mainly GI damage and degeneration of liver and kidney
• Rumen stasis with ingested food is a characteristic finding

Question 24

Laboratory diagnosis?

Answer 24

• Elevated ALP, LDH, CPK
• Chemical analysis
  
  • Analytical methods are expensive and time consuming
  • Specimens are suspected forage, water, kidney, urine, liver, stomach, feces

Question 25

Diagnosis?

Answer 25

• Difficult from clinical signs and lesions b/c they are nonspecific
• History of ingestion is important
• Chemical analysis might be helpful
• Rule out other diseases

Question 26

Treatment?

Answer 26

• No specific antidote
• Detoxification
  
  • Wash skin w/ soap + water
  • Activated charcoal
• Supportive/symptomatic treatment
  
  • IV fluids
  • Antidiarrheals and rumenatorics