Lecture 4: Tetanus

Definition of Biosecurity

A set of preventative measures designed to reduce the risk of introduction and subsequent transmission of infectious disease

Info needed to prevent instance and transmission of a disease

\-Cause (bacteria, viral, fungal)

\-How it is acquired and transmitted

\-Options for prevention

\-How to treat if prevention fails

Categories of diseases

\-Infectious: caused by microorganisms

\-Contagious: spread horse to horse

\-Zoonotic: animals to humans

Definition of incubation period

Time from exposure to onset of clinical disease

Definition of shedding period

Time that a disease can be spread from one horse to another. Can be before onset of clinical signs, or long after resolution.

Definition of carrier

Horse that can shed disease despite clinical recovery

Definition of latency

Occurs when the horse’s immune system is unable to eliminate the disease, but can contain it in a dormant state where it flairs up later and can shed at a later date. Often the cause of sudden disease breakouts.

Short v long incubation period

Short incubation period tends to spread rapidly, longer incubation period can provide more time to prevent and treat, but can obscure when horse was exposed.

Tetanus bacterial specifics

Anaerobic, gram +, spore forming

Ways tetanus is obtained

Puncture wounds, blunt trauma that damages tissues, eating contaminated soil or feces, gastric or intestinal ulcers

Tetanus acting pathway

Bacteria produces a toxin → travels through nervous system → binds and inhibits inhibitory neurons in spinal cord → causes skeletal muscle spasms

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2nd toxin causes tissue necrosis by depleting oxygen

List clinical signs of tetanus

Lameness, stiffness, hyperreflexia, difficulty swallowing, saw horse stance, stiff and extended tail, erect ears, sweating, pyrexia, flared nostrils, **3rd eyelid prolapse**

List 3 ways to diagnose tetanus

Evaluation of clinical signs, G+ rods seen on cytology of pus, anaerobic culture

Things to avoid when treating a horse with tetanus

Loud noises, bright lights, painful stimuli, sneaking up to the horse

Tetanus therapies

Antitoxin, wound therapy, oxygen/hyperbaric chamber, sedation, IV fluids, stomach tube, penicillin/metronidazole

Tetanus toxoid vaccine mechanism

Causes production of antibodies within two weeks, triggers active immunity, provides good lasting immunity.

Tetanus antitoxin mechanism

Used for tx or prevention, provides immediate, short term protection (3-4 weeks). Antitoxin binds to and neutralizes unbound toxins, but doesn’t reverse any that have already bound to the nervous system

Indications for giving the tetanus antitoxin

Give to newborn foals if the mare is not vaccinated, or if there is poor nursing during the colostrum phase. Give to all horses when there is a wound, especially in under vaccinated horses. Treatment of tetanus.

Tetanus cause of death

asphyxiation

Tetanus prognosis

50-80% mortality rate