Exam 1 - Equine Neurology: Bacterial & Toxic Diseases

Question 1

what is a common name for tetanus?

Answer 1

lock jaw

Question 2

what is tetanus?

Answer 2

bacterial neurologic disease characterized by extensor muscle rigidity & death

Question 3

what species is most susceptible to tetanus?

Answer 3

horses

Question 4

what organism causes tetanus?

Answer 4

clostridium tetani

Question 5

what is the etiology of tetanus?

Answer 5

common soil inhabitant & strict anaerobe

Question 6

how does c. tetani commonly gain access to the horse’s body?

Answer 6

puncture wound

Question 7

what is the pathogenesis of the tetanolysin toxin of tetanus?

Answer 7

damages tissues & creates an environment favorable for anaerobes & facilitates infection

Question 8

what 2 toxins are produced/released by clostridium tetani?

Answer 8

tetanolysin & tetanospasm

Question 9

what is the pathogenesis of the tetanospasm toxin in tetanus?

Answer 9

diffuses locally & via the bloodstream to peripheral nerve terminals throughout the body

travels retrograde up neurons

into CNS after 1-14 days

Question 10

how does tetanospasm work?

Answer 10

binds irreversibly to pre-synaptic neurons blocking release of inhibitory transmitters causing spastic paralysis

Question 11

when do clinical signs typically develop in tetanus infections?

Answer 11

usually 7-10 days after the wound but can be as short as 1 day or as long as 60 days

Question 12

what are the main clinical signs of tetanus in the horse?

Answer 12

prolapsed 3rd eyelid, generalized whole body rigidity, saw horse stance, elevated tail, hypersensitivity

Question 13

if an animal presents with a prolapsed eyelid, what 2 differentials immediately come to mind?

Answer 13

tetanus & HYPP

Question 14

what is the saw horse stance characterized by?

Answer 14

ears held pricked up

paralysis of breathing muscles

stiff legged gait

tail held out & stiff

Question 15

what are the advanced clinical signs associated with tetanus?

Answer 15

clonic-tonic spasms

severe muscle contractions - rhabdomyolysis

autonomic signs - tachycardia, sweating

recumbency & death

Question 16

how is tetanus diagnosed?

Answer 16

clinical signs, history, & ruling out other diseases

Question 17

in tetanus, when may you see a patient with a prolapsing nictitating membrane upon stimulation?

Answer 17

early in the course of the disease process

Question 18

what are some differentials for tetanus?

Answer 18

myopathy
meningitis
rabies
HYPP
trauma
laminitis
colic

Question 19

what are the 4 principles of treating tetanus?

Answer 19

1. provide a safe, quiet environment
2. eliminate organism & unbound toxin
3. sedation & muscle relaxation
4. general support

Question 20

what should the environment be like for a tetanus patient?

Answer 20

large, well-bedded stall, padded if possible

minimize light, noise, & other stimuli

cotton in the ears

hang water & feed

Question 21

how is tetanus eliminated from the body?

Answer 21

clean/debride wound

tetanus antitoxin into wound

penicillin

Question 22

how are the exotoxins eliminated or inactivated in tetanus treatment?

Answer 22

use the antitoxin which bounds any residual unbound toxin

Question 23

T/F: tetanus antitoxin can rarely cause acute hepatic necrosis (theiler’s disease)

Answer 23

true

Question 24

what should be included in general support for a tetanus patient?

Answer 24

iv fluids, parenteral or enteral nutrition, & pain control

Question 25

what is the prognosis for tetanus?

Answer 25

usually poor, fatality >75%

Question 26

what are poor prognostic markers of a tetanus patient?

Answer 26

rapid onset/progression of clinical signs & absence of vaccination

Question 27

how is tetanus prevented in the horse?

Answer 27

annual vaccine - tetanus toxoid tetanus antitoxin for non-vaccinated horse with wound or foal from non-vaccinated mare & give toxoid concurrently

Question 28

botulism affects what horses?

Answer 28

adults & foals

Question 29

what is botulism called in foals?

Answer 29

shaker foal syndrome

Question 30

what age of foals are typically affected by shaker foal syndrome?

Answer 30

foals 1-3 months old - can occur in outbreaks

Question 31

what is the etiology of botulism?

Answer 31

clostridium botulinum

Question 32

what is the mechanism of infection of botulism?

Answer 32

toxins are absorbed into circulation & neuroparalytic botulinum toxins reach presynaptic nerve terminals which blocks exocytosis of acetylcholine at the presynaptic membrane of the neuromuscular junction

Question 33

how do horses get clostridium botulinum?

Answer 33

they ingest it or have wound contamination

Question 34

how do horses get botulism from forage toxicity?

Answer 34

toxin is in the contaminated feed (decaying vegetable matter, decomposing animal, bird carcass) hay/silage - anaerobic conditions, pH remains above 4.5

Question 35

T/F: the presence of animal & bird carcasses in processed food materials is incriminating evidence for diagnosing botulism

Answer 35

true

Question 36

how do foals get botulism?

Answer 36

toxicoinfectious form - associated with type b forms in inflammatory lesions such -intestinal ingesta -wounds -gi ulcers -liver abscesses

Question 37

what are the common toxic forms of botulism in horses?

Answer 37

a, b, c, & d

Question 38

T/F: clinical signs of botulism are acute in onset

Answer 38

true

Question 39

what are common clinical signs of botulism in horses?

Answer 39

muscle tremors, slow eating, mydriasis (dilated pupil), poor muscle tone, depressed reflexes, weak tongue/eyelid tone, & urine & fecal retention

Question 40

what are the clinical signs of shaker foal syndrome?

Answer 40

suckling foals tend to show repeated episodes of trembling just before becoming recumbent - rapidly progressive

Question 41

what are the advanced clinical signs of botulism?

Answer 41

recumbency, dyspnea, cyanosis, & death

Question 42

how is botulism diagnosed?

Answer 42

typically presumptive based on multiple cases of recumbency/tetra-paresis with evidence of appetence but oral/pharyngeal dysplasia isolation from feed, patient feces, or wounds

Question 43

what tests detect botulinum toxins?

Answer 43

ELISA, PCR, & mouse inoculation assays

Question 44

what is paramount for success in botulism treatment?

Answer 44

nursing care!!! hydration, nutrition, & metabolic support/status

Question 45

what does the prognosis of botulism depend on?

Answer 45

amount of toxin affecting the animal & ability of specific antitoxin

Question 46

what are poor prognostic markers of botulism?

Answer 46

inability to stand lower survival rates for adult horses

Question 47

T/F: survival rates for severely affected foals treated with polyvalent antiserum/intensive support can be as high as 50-90%

Answer 47

true

Question 48

why is botulism a public safety risk?

Answer 48

humans are susceptible - especially infants don't take infants to site of outbreak

Question 49

how is botulism prevented in foals?

Answer 49

vaccination of mares with clostridium botulinum type b toxoid twice in the last trimester of pregnancy **especially in areas where shaker foal syndrome is common**

Question 50

what is the best treatment for botulism for the toxins?

Answer 50

IV polyvalent botulism antitoxin expensive & needs to be administered in the early stages of disease

Question 51

why should tetracyclines & aminoglycosides be avoided when treating botulism?

Answer 51

potential exacerbation of neuromuscular blockade

Question 52

what antibiotics should be given IV for a patient with botulism?

Answer 52

penicillin or metronidazole

Question 53

when should oxygen be supplemented in a patient with botulism?

Answer 53

if PaO2 is low

Question 54

T/F: some foals with shaker foal syndrome require mechanical ventilation

Answer 54

true

Question 55

T/F: the survival rate for adult horses with botulism is higher than foals with botulism

Answer 55

false - adults have lower survival rates

Question 56

what happens to your botulism patient's prognosis if you don't have the specific antitoxin on hand?

Answer 56

prognosis is POOR