Lecture 3: Diseases of the nervous system

Question 1

What is the mechanism of action for clostridium tetani

Answer 1

1. Tetanospasmin binds to renshaw cells within the central nervous system
2. Irreversible blockade of GABA/glycine
3. Leads to continued stimulation of the action potential

Question 2

What are some clinical signs of tetanus

Answer 2

Third eyelid prolapse, lockjaw, sawhorse stance, elevated tail head, hyperesthesia, muscular spasms, recumbency, convulsions, death by respiratory failure

Question 3

How do you dx tetanus

Answer 3

Clinical signs and finding anaerobic site of infection

Question 4

How long does it take to develop and replace new synapses with tetanus infection

Answer 4

6-8 weeks

Question 5

What is treatment for tetanus

Answer 5

1. Antibiotics- metro, penicillin
2. Drain abscess
3. Antitoxin- Colorado serum company
4. Sedatives/ muscle relaxants
5. Vaccinate

Question 6

How long is passive immunity from tetanus antitoxin

Answer 6

7-14 days

Question 7

What is a rare side effect of tetanus antitoxin that could contain parvovirus

Answer 7

Acute fatal hepatic necrosis (Theiler’s disease)

Question 8

What symptoms is more common in non-survivors of tetanus

Answer 8

Dysphasia, dyspnea and recumbency

Question 9

Survivors of tetanus will stabilize in __-__ days

Answer 9

5-7 days

Question 10

What are the 3 ways horses can get exposed to clostridium botulinum

Answer 10

1. Preformed toxin eaten
   - type B- decomposing vegetation
   - type C- decomposing carcasses in feed
2. Grows in intestine- type B- shaker foal
3. Grows in anaerobic wound- type B

Question 11

What is the pathogenesis/ MOA of botulinum

Answer 11

Blocks acetylcholine release at NMJ resulting in descending symmetrical progressively flaccid paralysis

Question 12

How can you dx botulinum

Answer 12

1. Identify toxin in feed, serum, GI contents, feces, debris
2. Grain test- should consume 8oz grain in under 2 minutes

Question 13

What are some clinical signs of botulism

Answer 13

Dysphasia, poor tongue and lip tone, weakness, lethargy, head carriage, muscle tremors, recumbency, death from respiratory failure

Question 14

What is tx for botulism

Answer 14

1. Antitoxin
2. Supportive care

Question 15

Botulism antitoxin is not effective after botulinum toxin has been ___

Answer 15

Translocated into the cells

Question 16

What is the prognosis for botulinum

Answer 16

70-99% mortality, 48% survival

Question 17

T or F: horses with botulinum in which treatment is started after they are already down usually die

Answer 17

True

Question 18

How do you prevent botulinum

Answer 18

Type B vaccine

Question 19

What is the pathogenesis/ MOA of rabies

Answer 19

Virus travels to CNS via neurons and reaches salivary glands via associated cranial nerves

Question 20

What are the reservoir hosts for rabies

Answer 20

Skunks, raccoons, bats, and red fox

Question 21

What is the incubation period for rabies

Answer 21

9 days- 1year

Question 22

What is the most common clinical sign of rabies in horses

Answer 22

Colic

Question 23

What is the furious form of rabies

Answer 23

Aggressive behavior, photophobia, hydrophobia, tremors, hyperesthesia, convulsions

Question 24

What is the dumb form of rabies

Answer 24

Depression, anorexia, head tilt, salivation, circling, ataxia, dementia

Question 25

What is the paralytic form of rabies

Answer 25

Ascending paralysis, ataxia

Question 26

How do you dx rabies and what is standard

Answer 26

1. Immunofluorescence of brain- standard 2. Histo of Negri bodies 3. CSF may be normal or pleocytosis

Question 27

What is the first thing you do for suspected rabies case

Answer 27

Contact state vet

Question 28

After contacting state vet what are the next steps in rabies treatment/biosecurity

Answer 28

1. Quarantine 6 months 2. Aggressive wound care- scrub and clean for 15 mins 3. Unvaccinated can’t be vaccinated for 6 months 4. Vaccinated horses should be boostered immediately

Question 29

What is prognosis for rabies

Answer 29

100% fatal

Question 30

What is metabolic encephalopathy characterized by

Answer 30

Abnormal mental status and elevation of ammonia in blood

Question 31

What is the pathogenesis of metabolic encephalopathy

Answer 31

1. Glutamine and urea broken down to ammonia 2. Ammonia overwhelms hepatocytes and crosses into circulation and crosses BBB 3. Ammonia is converted to glutamine which has an osmotic effect resulting in cerebral edema

Question 32

What cell is indicative of metabolic encephalopathy

Answer 32

Type II astrocytes

Question 33

What are some clinical signs of metabolic encephalopathy

Answer 33

Behavior changes, depression, head pressing, circling, mild ataxia

Question 34

What can cause hyperammonemia

Answer 34

1. Hepatic dysfunction: liver failure or PSS 2. Excessive ammonia produced in intestinal tract

Question 35

What can cause renal (uremic) encephalopathy

Answer 35

Accumulation of metabolic wastes in the brain

Question 36

How do you dx metabolic encephalopathy

Answer 36

1. Blood-ammonia levels 2. Liver enzymes may or may not be elevated

Question 37

What is tx for metabolic encephalopathy

Answer 37

Lactulose

Question 38

What does a true seizure look like

Answer 38

Repetitive and rhythmic muscle movements, premonitory signs and aura, postictal signs, not aware or responsive, rapid eye movement

Question 39

What is affected in partial seizure

Answer 39

Discrete area of cerebrum affected

Question 40

What is affected in generalized seizure

Answer 40

Arises from both cerebral hemispheres simultaneously

Question 41

What is a status epilepticus

Answer 41

Succession of seizures without regaining consciousness or continual seizures for 5 minutes

Question 42

What cardiovascular events mimic seizures

Answer 42

Syncopal episode from arrhythmia, ruptured chordae tendinae, myocardial infarction

Question 43

What circulatory shock events mimic seizures

Answer 43

Hemorrhage, volume depletion

Question 44

What electrolyte disorders mimic seizures

Answer 44

Hypocalcemia, hypo magnesium

Question 45

What muscle diseases mimic seizures

Answer 45

HYPP, recumbency myopathy, exertional rhabdomylosis

Question 46

What development abnormality can be a differential for seizures

Answer 46

Hydrocephalus

Question 47

What metabolic abnormalities are differentials for seizures

Answer 47

Hyperammonemia, hypo/hyperosmolality, electrolyte disorders

Question 48

What neoplasms can be differentials for seizures

Answer 48

Cholesterol granuloma, PPID

Question 49

What are some iatrogenic differentials for seizures

Answer 49

Air embolism, intracarotid injection, fluphenazine

Question 50

What is a differential dx for idiopathic seizures

Answer 50

Epilepsy

Question 51

What are some differential dx for infectious seizures

Answer 51

Encephalitis, meningitis

Question 52

What are some toxic differential dx for toxic

Answer 52

Locoism, moldy corn

Question 53

What is used for immediate control of seizures

Answer 53

Diazepam- increase GABA

Question 54

What drugs can be used for prevention of seizures

Answer 54

Phenobarbital, potassium bromide, phenytoin