The Yin and Yang of botulism and tetanus Flashcards
What is the difference between localised and generalised tetanus?
Localised = to one area of the body. Note that this will progress to generalised tetanus
Generalised = whole body affected
How is tetanus diagnosed?
- Diagnosis is generally based on clinical signs and history
- can attempt culture but ususally difficult due to not being able to find the wound and low bacterial numbers
- serum tests looking for antibody to the exotoxin - not very helpful
What is the incubation period of tetanus?
3-10 days, but can be several months
What are the clinical signs that are associated with tetanus?
- Muscle rigidity in all species
- protrusion of the nititating membrane across the eye
- spastic paralysis of the fore and hindlimb muscles
- unsteady, straddling gait and the head and tail are held stiffly extended
- hyperae4sthetic and a sudden noise or touch induses spasm
- tetany of the masseter muscles (lockjaw)
- wrinkling of the skin on forhead and pricking of the ears
Are clinical signs the same across all species?
Similar presentations, however it takes different amounts of time to progress depending on the species.
What animals are susceptible to tetanus?
- Mammals vary in their susceptibility to tetanus toxin
- Resistance is related to the inability of the toxin to penetrate and bind nervous tissue
- Highly susceptible: Horses, guinea pigs, humans, mouse, rabbits, will succumb to low doses of toxin (horses are the most susceptible). The horse has been assigned an arbitrary value of 1, with 1 indicating the most susceptible
- Susceptibility values relate to the comparative amount of toxin required to produce clinical illness, with increasing values indicating decreasing susceptibility
- Less susceptible: Dogs, cats, cattle, pigs, sheep, goats
- Extremely resistant: Most birds and cold-blooded animals
How would you treat a case of tetanus?
- Vigorously clean wound and debride - to stop bacteria lberating exotoxin
- Antitoxin - beware of anaphylaxis. The toxin binds irreversibly but antitoxin mobs up free toxin but does nothing for the bound toxin
- Antibiotics - penicillin, metronidazole which kills the bacteria and stops more exotoxin liuberation
- DO NOT IGNORE localised tetanus, as it WILL progress to generalised untreated.
- Supportive care - feeding, muscle relaxants, pain relief
How can tetanus be avoided in horses?
- Clean wound aggressively
- Antitoxin should be given to ANY horse with a penetrating wound (often given to mares post foaling)
- There is a vaccine available - toxoid. Requires a booster every 1-2 years.
What are the risks of tetanus associated with in production animals?
o Pigs: Castration
o Lambs: Castration, shearing, docking, vaccinating, injections
o Cattle: Genital tract post-parturition, Post-castration, Neonatal tetanus via umbilical cord cause of tetanus and neonatal death in all species including humans
What is botulism and what is it caused by?
- Neurological disease caused by Clostridium botulinum
- Causes an ascending flaccid paralysis that is often fatal if supportive treatment is not given
Where is Clostridium botulinum found?
- Usually found as spores in soil and aquatic environments worldwide
- Under appropriate physical conditions, the spores germinate and the vegetative bacteria produce an exotoxin that is released upon bacterial cell lysis
Explain the pathogenesis of botulism
- Binds to presynaptic membrane of peripheral nerves but different animals have different affinity for toxin
- Toxin passes through cell membrane by receptor-mediated endocytosis
- Blocks ACh release from nerve ending
- Results in flaccid paralysis of skeletal muscle and parasympathetic dysfunctiuon, respiratory failure is usual cause of death
- the binding of the toxin is irreversible - once the toxin enters a cell the antitoxin is unable to reach it
How would a human or an animal get botulism?
Humans
- The toxin is preformed in foodo
- Usually involves high protein foods (rich in proteases)
- Foods contaminated by rotting vegetation or other foodstuffs as rotting provides the nutrients and the enzymes to enable full activation of the toxin before it is ingested
- Botox treatments: Illegal sources or incorrectly administered
Sheep and cattle
- Improperly stored silage,
- or silage/hay contaminated by the bodies of small rodents which are a good source of protein and enzymes, or from carcasses
- Problem in the phosphorus deficient areas, when animals (especially cattle) may eat the bones of dead animals (pica) in an attempt to alleviate the deficiency
- Occasionally reports of botulism in animals when standing in floodwaters and drinking water containing dead animals and toxin e.g. Centennial Park Ducks
What are the clinical signs associated with botulism?
- Severity depends on amount of toxin ingested
- Incubation period is < 6 days
- Ascending, symmetrical flaccid paralysis (Generalised LMN disease, weak and unable to stand)
- Signs of decreased cholinergic function: Constipation, urinary retention, decreased salivation and lacrimation, dilated pupils
In chickens
- the disease is known as “limber neck”. Birds will be seen with their heads or necks dragging
In horses and dogs
- Signs may vary but are predominantly related to progressive muscular paralysis
- General weakness, dysphagia, decreased tongue tone and tongue may hang out the side of the mouth, colic or inability to rise
Cattle
- Recumbent, drooling with laboured breathing
Cats
- Resistant to the effects of botulinum toxin
- Botulism is rare
- Rare in lions and domestic cats
How many types of botulinum exotoxin are there, and does the vaccination cover all types?
There are 8 toxin types, and protextion against one C. botulinum type does NOT protect against the others. There are species variation in toxin types.
