Tetanus in Domestic Species Flashcards by Kayla Stauffer

what is the causative agent of tetanus

clostridium tetani

How well did you know this?

Not at all

Perfectly

what type of bacteria is clostridial tetani

anaerobic bacterium

How well did you know this?

Not at all

Perfectly

how does clostridial tetani survive in the environment

spores in the soil

found in human and horse feces

How well did you know this?

Not at all

Perfectly

how does clostridium tetani infection come about

Organism invades wounds, changing from vegetative to replicative state in anaerobic environment

How well did you know this?

Not at all

Perfectly

what exotoxins are produced from clostridium tetani

Tetanolysin

Tetanospasmin

How well did you know this?

Not at all

Perfectly

what does tetanolysin do

Damages viable tissue, promoting anaerobic environment for bacterial growth

How well did you know this?

Not at all

Perfectly

what does tetanospasm do

Enters circulation, binds to receptors on motor nerve endings

Spastic paralysis

How well did you know this?

Not at all

Perfectly

what is the pathogenesis of tetanus

deep puncture wounds most important

toxin produced and onset of clinical signs may occur several days after deep wound or entry point

How well did you know this?

Not at all

Perfectly

what are entry points of clostridium tetani

Umbilical artery

Foot abscess

Injection site abscess

Wound

Post surgical entry and multiplication

How well did you know this?

Not at all

Perfectly

what is the pathogenesis of tetanospasmin

Transmission from infection site

Diffuses to muscles from infection

Spreads via lymphatics to blood

Binds receptors on motor end plates

Fragment of toxin internalized and moved along neutron by retrograde axonal transport to CNS

Pre-synaptic endocytosis

TeNT is 2,000 times more toxic at central inhibitory nerves than at peripheral synapses

How well did you know this?

Not at all

Perfectly

what is the mechanism of action of tetanospasmin

Binds pre-synaptic receptor

Entire toxin endocytosed in CNS

Damage to synaptobrevin protein

Inhibition of release of GABA at synaptic cleft as synaptic vesicle fusion inhibited

Spinal cord, brain stem, peripheral nerves, neuromuscular junctions, muscles all affected

Constant excitation of motor neurones
Hyperreflexia, hypertonia, sympathetic excitability

How well did you know this?

Not at all

Perfectly

what is the half life of the toxins produced

5-6 days

How well did you know this?

Not at all

Perfectly

is the condition reversible

Neuronal binding of toxin is irreversible

Recovery requires growth of new nerve terminals

Prolonged disease course (6-8 weeks)

Antitoxin should be given as soon as possible for management

How well did you know this?

Not at all

Perfectly

what are the target species of clostridium tetani

Ubiquitous organism but requires skin to break for entry

Horses, goats, sheep, monkeys and cattle are more sensitive

Dogs are relatively resistant and cats are more resistant

Greatest susceptibility in equids?

How well did you know this?

Not at all

Perfectly

when is tetanus commonly seen in cattle

commonly seen after castration (open + closed)

increased risk with ringing techniques

hoof injuries, umbilical or puerperal infection

How well did you know this?

Not at all

Perfectly

what is the fatality rate of tetanus in cattle

~80% in young calves

higher in adult

what are the clinical signs of tetanus in cattle

Generalized muscular rigidity and spasms

Hyperaesthesia

Third eyelid prolapse

Trismus (lockjaw)

Convulsions

Respiratory arrest and death

Opisthotonus

Bloated abdomen

No ruminal contractions

Fixed expression

Muscles of head are affected because cranial nerves are short, particularly CN V (trigeminal nerve)

how is tetanus diagnosed

clinical signs

history

anxious expression, rigid ears

salivation due to lockjaw

may become unable to swallow

what are the clinical signs of tetanus in dogs

Stiff gait

Facial muscles are contracted

Raised brows; anxious expression

Trismus

Ptyalism

May be concurrent wound

how is tetanus diagnosed in dogs

Clinical signs

History

what are the early clinical signs of tetanus in equids

May be unilateral/spastic gait in limb with pre-exisiting injury or foot abscess

Nictitating third eyelid *

Characteristic

Muscle hypertonia

Slapping of legs as horse walks forward
Hindlimb spastic paresis

Inability to lower head fully

Slow mastication and swallowing

Pyrexia

Hyperaesthesia

Not many other conditions
Sensitive to bright light, loud noises

what are the progression of clinical signs in tetnaus in horses

Fixed dilated nostrils and permeant protrusion of the third eyelid

Rigidly uptight ears
Increasingly shuffling gait in all limbs

Wide based stance

Complete trismus and ptyalism

Inability to raise relax anal sphincter results in impactions and colic

May fall over spontaneously; respiratory muscles compromise

Variable hyperaesthesia

what are the principle ddx for tetnus in equids

rhabdomyolysis

myotonia (QHs)

laminitis

electrolyte disturbances

Hypomagnesemia
Hypocalcemia
HYPP (QHs)
Hypernatremia

Seizures

Meningitis

Strychnine toxicity

how is a tetanus diagnosis confirmed

Diagnosis by exclusion of other ddx

Clinical signs

Poor vaccination history

Elimination of metabolic causes

Attempt to localize lesions

Perform specific tests for hypertonia and nictation

what is the prognosis for tetanus

Rate of onset/deterioration in clinical signs is correlated to prognosis Inability to support weight and balance at rest = poorer prognosis Unable to stand once fallen Complete inability to eat or drink requires more intensive nursing, greater costs and also poorer prognosis 5-6 weeks for new vesicles to generate

what is the decision tree for tetanus treatment

**Mild clinical signs:** * Nictitans membrane flashing, ears pulled caudally, slightly stiff gait but still walking and eating **Moderate clinical signs:** * Nictitans membrane flashing, ears pulled caudally, limbs stiff and walking with difficulty, trismus and generalized muscle spasm **Severe clinical signs:** * Capable of standing, but incapable of walking, severe trismus * Difficulty with prehension, chewing and swallowing **Terminal clinical signs:** * Animal recumbant * Incapable of standing * Incapable of eating

what are the treatment goals of tetanus

Debride and lavage any pre-existing wound to remove anaerobic environment and bacteria * Includes searching for foot abscesses Stop further absorption of tetanospasmin Provision of dark, quite stable —\> decrease stimuli Sedation Antibiotic therapy to eliminate bacterial challenge if not historical Maintenance rate IV fluid therapy may be required if unable to swallow (50 ml/kg/day) Enteral nutrition if unable to swallow Monitor urinary and fecal output Indwelling catheter may be needed and manual fecal removal Sling to partially support body mass Smaller patients easier to manage if recumbent

how would you sedate a horse being treated for tetanus

Acepromazine 0.05 mg/kg IM QID Diazepam 0.1 mg/kg IM q4-6h

what antibiotic therapy would you use to treat a horse with tetanus

Metronidazole 15 mg/lg IV perffered Or penicillin G at 20,000 IU/kg QID

how is tetanus prevented

Tetanus toxoid vaccination extremely effective Dose 1 at ~4 months with dose 2 after 4 weeks Booster dose at 1 year good antibody levels after 3 years Antitoxin 1500 IU might be indicated before high risk procedures if not vaccinated — provides 10-14 day protection Boost pregnant mare at 6-12 weeks before parturition date so as to increase colostral antibody levels to tetanus

what should you do if there is a wound on an unvaccinated horse

Lavage wound thoroughly to remove all organic material Drain foot abscess with hoof knife then soak Administer tetanus anti-toxin SC locally Start course of tetanus toxoid IM at same time Remember to give second part of primary course after 4 weeks Record in passport Boost after 12 months Immunopurified tetanus toxoid absorbed to aluminium phosphate

what is the equine tetanus vaccination schedule

**Primary course:** * Single IM dose from 3 months of age with second dose after 4-6 weeks and third 1 year after that Foals born to highly vaccinated mares should not be vaccinated until 6 months of age due to interference from maternally derived antibodies Thereafter bi-annual vaccination Foal born to unvaccinated dam Tetanus anti-toxin Umbilical care Tetanus toxoid start at 3 months