Synonyms: Lock Jaw
• a non contagious, non-febrile, infectious disease
• Animals affected by potent toxins
• spasmodic contractions of skeletal muscles
ETIOLOGY:
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• Clostridium tetani
• a gram positive - young culture
• motile, a long, slender, rod shaped, rounded ends
• Old culture - gram negative
• Terminal spores with a drumstic appearance
• Spores - resistant & persists - soil for many years.
• Normal inhabitant - intestine of herbivores
• Flagellar (H) - thermo labile & somatic (O) - thermo stable
• Grows under strict anaerobic condition
• Spores - destroyed - 115◦C - 20-60 min.
• Vegetative - destroyed by heat
• Release three types of toxins under anaerobic condition:
• Tetanospasmin - potent neurotoxin
• Tetanolysin – haemolysin toxin
• Fibrinolysin – muscles & tissue lysis toxin
PREVALENCE:
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• More common - tropic > temperate
• Soluble calcium - cause sufficient local tissue damage to permit spore germination
• Sporadic - India
Transmission :
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• Through skin penetration - parturition, retained placenta, uterine prolapse, shearing, docking, castration, spaying, & any damage to the skin
• Ingestion & inhalation
Host affected
• Horses & mules - highly susceptible
• Cattle - less susceptible than man & horses
• Sheep, goats, pigs - more susceptible > cattle
PATHOGENESIS:
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• Organism entry ® broken skin / injured wounds ® For the tetanus to develops need some favorable conditions :
• Body tissues – access to spores
• Creation of oxidation reduction potential drop – anaerobic condition
• Germination of spores & toxin production
• Spores germinate to become - vegetative growth ® Cellular autolysis ® releases toxins; Tenospasmin,
tetanolysin & fibrinolysin -
• The carboxy terminus polypeptide - heavy chain - storing toxin & the light chain liberates the toxic action
• Toxins ® absorbed & spread ® blood stream -, exert neuro-toxic effects in peripheral nervous system - via motor nerves - central nervous system - Brain & spinal cord
• The toxin - at the wound site - bind to adjacent motor axonal terminals & enter blood circulation to bind axon terminals at the remote site
• Toxins bind with - “protogon” - nerve tissues – made of cerebrocide & oligosaccharides like N-Acetyl galactosamine & galactose. Acts on the inhibitory synapses intervene in the action of inhibitory transmitter -cause hyperirritability & spasm.
• Toxins in blood – spastic paralysis
• Toxin invasion – nervous system-
• Death - asphysixation ¬fixing of respiratory muscles
• Mortality - horse 50% & cattle 50- 80%.
CLINCAL SIGNS:
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Horses:
Hypersensitiive, trismus
Saw horse stance, prolapse of the third eye lid, erection of ears, immobility of the ears – predominant
Head, neck & leg - extended position.
Spasm - facial muscle, masseter muscle - trismus.
Mastication & prehension – difficulty - drooling of saliva .
Very sensitive to light & noise
Trembling & profuse sweating.
Death ® asphyxia in 3-10 days.
POST MORTEM FINDINGS:
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• Rigor mortis develop very quickly
• Congestion - spinal cord, medulla, nerve
• Hyperaemia - lungs due to asphyxia
• Haemorrhages -skeletal muscles
• Loss of cross striation and atrophy of the myofibrils
Differential diagnosis:
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• Strychnine poisoning: Absence of wound, chemical analysis - bowel content - toxins.
• Grass tetany: Grazing pasture - Low Mg level, no wound, response to magnesium therapy
• Milk Fever: Sternal / lateral recumbence, low Calcium level, absence of wound & response to calcium therapy.
• Rabies: History of dog bite wound, changes in the behavior, salivation, bleating, biting tendency, no wound, ascending paralysis & death.
• Status Epilepticus: Constant seizure, no wound, response to anti- convulsion therapy.
DIAGNOSIS:
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• Gram staining : C.tetani, drumstic appearance of spore.
• Biological Inoculation: Challenging of mice, rabbit & guinea pig with cultured C.tetani
• Culture examination: Gas Pak system in anaculture- cooked meat broth or into blood agar media - 24 hours at 37◦C -swarming growth / spore formation- haemolysis
• Toxin neutralization with serum anti tetanus toxin
• Blood picture: Neutrophilic leucocytosis with left shift
• Acute case- Serum creatinine Phosphokinase (CRK)
• Thoracic radiography - small animals for aspiration pneumonia
CONTROL:
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Neutralization of free toxin by ATS:
• Has less value ¯ toxic condition - short term prophylaxis (1500IU)
• transient immunity - 21 days - quicker action.
• ATS mainly acts on free toxin not on the bound toxin.
• Can be applied on the local wound
• Prior to I/V application 0.1 to 0.2 ml injected intradermal / s/c route – no adverse effect.
• wheal formation at the site of injection.
• TAT - from healthy horses by hyperimmunisation with C.tetani culture Ag
• Can be given in mares & foals
• Colostral immunity last for 10 weeks.
TETANUS TOXOID (TT):
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• an anatoxin - active immunity
• Recommended for healthy animals - preventive vaccines
• Serum Institute of India Ltd.- TT
• a sterile, whitish, turbid, uniform suspension of tetanus toxoid adsorbed on aluminium phosphate & suspended in isotonic sodium chloride solution.
• Potency of this toxoide is 0.5ml of human dose contains:
• Tetanus Toxoid - >5LF units
• Adsorbed on Aluminium Phosphate (AlPo4) - > 1.5mg
• Thiomersal - 0.01% preservative
• TT can be given with ATS at different sites
MANAGEMENT:
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• Wound - cleaned, debrided with H2O2 - tissue O2 tension & prevent bacterial growth
• Administration ATS / antibiotics - at the site of wound
• Hyperbionic O2 tissue oxygen level & inactivate bacteria
• Horse & dog: Nasogastric tube feeding
• Enema & catheter -relieve stagnant urine & faecal matters
• Tympany - rumenotomy
• Castration - done hygienic area
• Indwelling tube - avoid disturbances – due to repeated passing of stomach tube.
• Moist & soft feed given.
• Provided with clean water, feed & bedding material
TREATMENT:
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• Penicillin G 22,000 IU/kg bw 3-4 times I/V or I/M.
• Procaine Penicillin I/m twice daily
Relaxation of muscles
• Chlorpromazine 0.04-0.1mg/kg bw
• Promazine 0.5-1mg/kg bw
• Acetyl Promazine 0.03mg/lb bw
• Sodium pentobarbital 5% solution 2-4ml /kg bw I/V
• Diazepam 0.01-0.4mg through I/V
• Use of phenothiazine in combination with Pentobarbital is considered
• Diazepam relax muscle to potentiate GABA mediated CNS inhibition but it has to be given at short interval
