Toxin induced neurological disease in the horse

Question 1

What causes tetanus

Answer 1

Clostridium tetani exotoxin

Question 2

How does tetanus get into horses

Answer 2

associated with dirty wounds
C. tetani is ubiquitous in soil, ruminants faeces
spores are long lived and resistant to most disinfectants

Question 3

is tetanospasmin binding reversible

Answer 3

No - the nerves have to go through complete regrowth

Question 4

List the clinical signs of tetanus

Answer 4

tight facial expression
limb spasticity
fixed extended neck
tight jaw, larygeal spasm
dysphagia
elevated tail head
recumbencu
dyspnoea
hyperthermia
profuse sweating

Question 5

Describe how to treat tetanus

Answer 5

tetanus antitoxin can be given IV or intrathecal
muscle relaxants
Supportive care - IVFT, quiet environment
magnesium sulphate - blocks NMJ tranmission
clean, debride and provide antibiotics to any wounds

Question 6

Describe how to prevent tatenus

Answer 6

VACCINATION
dose mares 4 weeks before delivery - then dose foals @ 4-6 months with a booster 4 weeks after and a 3rd vaccine @ 12 months - then continue biannually

if mares are unvaccinated :
dose foals @ 1-3 months, then give 3 doses 4 weeks apart, another dose 12 months after - then continue biannually

Question 7

what causes botulism

Answer 7

clostridia botulinum

Question 8

How do animals get botulism

Answer 8

ingestion of toxins due to forage/ soil contamination or through wounds or injections

Question 9

what type of botulism is most common in horses

Answer 9

type B

Question 10

does botulism cross the BBB

Answer 10

No

Question 11

List the clinical signs of botulism

Answer 11

mydriasis
slow PLR
tongue hypotonia
dysphagia
weakness
muscle tremors
recumbency

Question 12

Describe how to diagnose botulism

Answer 12

feed challenge test
faecal samples, GI fluid analysis and liver samples -> only diagnosed in 30-40% of cases

Question 13

Describe the feed challenge test

Answer 13

give 8oz grain in a shallow pan - normal horse will finish in less than 2 minute, botulism horse takes significantly longer to finish

Question 14

Describe how to treat botulism in horses

Answer 14

serum anti-toxin
nutritional support
support recumbency

Question 15

what is stringhalt

Answer 15

disorder characterised by a sudden and exaggerated flexion of the pelvic limbs during the swing phase of locomotion

Question 16

Describe classical stringhalt

Answer 16

unilateral: toxic or trauma?

Question 17

Describe pasture-associated stringhalt

Answer 17

bilateral- outbreaks in horses at pasture

Question 18

what can cause stringhalt disease

Answer 18

ingestion of plant neurotoxin (dandelions) - leads to demyelination of the long nerves
OR
trauma to nerves

Question 19

how can we determine if stringhalt is from trauma or toxins

Answer 19

we can do nerve blocks + use CS and history

Question 20

Describe how to treat stringhalt disease

Answer 20

mechanical - OA treatment, split the lateral digital flexor tendon

Toxic- Phenytoin

Question 21

Describe rye-grass staggers

Answer 21

Tremorgenic mycotoxins (metabolites produced by endophyte fungi) are ingested
the fungi affect perennial rye-grass

Question 22

List the clinical signs of rye grass staggers

Answer 22

coarse muscle tremors
cerebellar damage
jerky hindlimb movement
base wide stance
exaggerated truncal sway
abortion in pregnant mares

Question 23

Describe how to treat rye-grass staggers

Answer 23

remove horse from pasture (resolution within 2 weeks)
reduce handling and provide quiet environment
provide water and feed