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TETANUS
Lock jaw
Definition
• It is an acute highly fetal wound-infection toxemic
disease of all animals and human which caused
by the toxins of Clostridium tetani and
characterized by an increased reflex excitability of
the motor nerve centers with continuous
spasmodic contraction of all striated muscles and
clinically by hyperesthesia tetany, convulsion and
death.
Etiology
• C tetani, an anaerobe with terminal, spherical spores with typical
drumstick appearance, is found in soil and intestinal tracts.
• It produces a number of toxins among them the most important are:
• Neurotoxin or tetanospasmin: It is a protein in nature and
responsible for the characteristic signs of tetanus
• Hemolysin or tetanolysin: It is a potent lethal toxin. It is
responsible for the hemolysis around colonies on blood agar
• It is grows in blood agar producing colonies
surrounded by complete zone of hemolysis
after 24-48 hours.
• Spores can be killed by direct sunlight within 12 days, boiling water
within 10-15 minutes, 30%hydrogen peroxide within 10 minutes.
Epidemiology
• Distribution: tetanus occurs in all parts of the world in all farm
animals. It is mainly appears as sporadic cases. In Egypt, it
commonly occurs in all farm animals
• Animal susceptibility: Human and solipeds (Horse, mules
and donkeys) are the most susceptible followed by sheep,
goats, pigs and cattle. Dogs and cats are rarely susceptible.
• Factors influencing susceptibility:
• The disease may appear in all breeds, sexes and ages.
• The disease may appear any time of the year but outbreaks are
common following castration, shearing, dehorning and other similar
operations.
Epidemiology
• Transmission:
• Source of infection: C. tetani organisms are commonly present in the
feces of animals, especially horses, and in the soil contaminated by these
feces.
• Mode of transmission: The portal of entry is usually through deep
puncture wounds but the spores may lie dormant in the tissues for some
time and produce clinical illness only when tissue conditions favor their
proliferation.
• The portal of entry may be different according to the animal species such
as:
• Horses: Puncture wounds of the hooves are common sites.
• Cattle: Introduction to the genital tract at the time of parturition is the usual
portal of entry.
• Sheep: following castration, shearing, docking, vaccinations, or injections
of pharmaceuticals especially anthelmintics
Epidemiology
• The portal of entry may be different according to the animal
species such as:
• Neonatal born animals: tetanus occurs when there is infection
in the umbilical cord associated with insanitary conditions at
parturition.
• Pigs: pigs may be infected through umbilicus or through
castration wounds.
• Wounds of internal organs such as teeth eruptions and injuries
of intestinal mucosa due to worm infestations may give rise to
infection (idiopathic tetanus).
• Moreover, spores may stay dormant in tissues for several
months of even years until the conditions become favorable for
vegetation and proliferation of the organism and give rise to
idiopathic tetanus (activated latent infection).
Pathogenesis
• The spores of C tetani are unable to grow in normal tissue
or even in wounds if the tissue remains at the oxidationreduction potential of the circulating blood
• Suitable conditions for multiplication occur
• The bacteria remain localized in the necrotic tissue at the
original site of infection and multiply. As bacterial cells
undergo autolysis, the potent neurotoxin is released.
• The neurotoxin is absorbed by the motor nerves in the
area and passes up the nerve tract to the spinal cord,
where it causes ascending tetanus
Pathogenesis
• The toxin causes spasmodic, tonic contractions of the
voluntary muscles by interfering with the release of
neurotransmitters from presynaptic nerve endings
• the excess is carried off by the lymph to the bloodstream
and thus to the CNS, where it causes descending tetanus.
• Spasms affecting the larynx, diaphragm, and intercostal
muscles lead to respiratory failure. Involvement of the
autonomic nervous system results in cardiac arrhythmias,
tachycardia, and hypertension.
Clinical signs
• . The incubation period is about 7-10 days after injuries
but it may be 3 weeks or more in some cases
• . Tetanus usually appears as sporadic or individual cases
• The mortality depends up on:
• Nature of the wound: deep badly soiled lacerated wound are
accompanied with high mortality rate.
• The site of infection: wound near the head or neck are more
dangerous than those of the trunk or hind limbs.
• The incubation period (the infection doses): the shorter incubation
period and higher mortality would be expected.
• The adopted treatment: The course of the disease is different
among and within the animal species. Generally, the duration of the
fetal illness is usually 5-10 days in cattle and horse but sheep
usually die in the third day.
Clinical signs
• Initially, there is an increase in
muscle stiffness, accompanied by
muscle tremor.
• There is trismus with restriction of
jaw movements, prolapse of the
third eyelid, an erect cartridge of
the ears, retraction of the eyelids
and dilation of the nostrils, and
hyperesthesia with exaggerated
responses to normal stimuli
• stiffness of the hind limbs causing
an unsteady, straddling gait,
especially when backing or turning
and the tail is held out stiffly,
(hump-like)
Clinical signs
• The animal may continue to eat and drink in the early stages but mastication
is soon prevented by tetany of the masseter muscles, and saliva may drool
from the mouth. If food or water is taken, attempts at swallowing are
followed by regurgitation from the nose.
• Constipation is usual and the urine is retained, the rectal temperature and
pulse rate are within the normal range in the early stages but may rise later
when muscular tone and activity are further increased.
• As the disease progresses, muscular tetany increases and the animal
adopts a 'sawhorse' posture.
• the hind limbs are stuck out stiffly behind and the forelegs forward. Sweating
may be profuse and the temperature rises, often to 42°C. The convulsions
are at first only stimulated by sound or touch but soon occur spontaneously.
• finally, severe tetanic spasm during which respiration is arrested.
Clinical signs
• Idiopathic tetanus, in which classical signs of tetanus
occurs without wounds as in internal organs wounds as
liver abscess or intestinal erosion from parasites
• Ascending tetanus, this type occurs in not highly
susceptible animals as dog and cat where only nerve
trunk near the toxigenic site absorb toxins to produce
local muscular spasm
• Desending tetanus, this type occurs in highly susceptible
animal as equine and humans where toxins disseminated
via vascular channels to nerve endings in areas far away
from toxigenic site and toxin reach to CNS produce
generlized spasm begin from head to tail
prognosis
• The prognosis is poor when the wound present near CNS,
severe lacerated wound, high temperature, lock jaw,
drenching pneumonia, idiopathic tetanus and signs rapidly
progress.
Diagnosis
• Field diagnosis: Tetanus can be diagnosed from the
clinical signs which can be supported by history of nonvaccination, history of wound and recent obstetrical or
surgical interference.
Diagnosis
• Laboratory diagnosis:
• Samples: air-dried impression smears from spleen,
wound site, culture swab from wound site in anaerobic
transport media; spleen in sterile, leak proof container.
Diagnosis
• Laboratory examination:
• Direct microscopic examination of the lesions
smear by Gram stain: Demonstration of the
characteristic drumstick spores is diagnostic.
However, the results of this test are not
satisfactory because the organism cannot be
always demonstrated in the wound.
• Animal inoculation: It is the most reliable technique for the
laboratory diagnosis of tetanus. Two groups of mice can be used.
One group can be protected by subcutaneous inoculation of 750
IU/mouse of tetanus antitoxin two hours before challenge. Both
mice groups can be challenged by I/M inoculation in the hind leg
with 0.25 ml of the supernatant of 48 hour cooked meat broth of
the suspected sample. Rapid development of the clinical signs of
tetanus in the non-protected group indicates the presence of
tetanus toxins.
Treatment
• The main principles in the treatment of tetanus are to:
• Eliminate the causative bacteria
• Neutralize residual toxin
• Control muscle spasms until the toxin is eliminated or destroyed
• Maintain hydration and nutrition
• Provide supportive treatment
Treatment
• Elimination of the causative agent:
• Large doses of penicillin should be injected I/V as sodium
benzyl penicillin 35,000 IU/kg followed after 12 hours by
I/M inoculation of 2,000 IU/kg of procaine penicillin which
should be repeated every 12 hours for 5-7 days.
• The wound (if found) should be treated by removal of
necrotic tissue and irrigation with H2O2 or tincture of
iodine then application of penicillin ointment. Treatment
should be continued for 5 days and wound should be left
opened.
• Neutralization of the unfixed toxin:
• Administration of antitoxin for neutralization of unfixed
neurotoxin in large doses during early stages has a great
value in the treatment. Very large doses of antitetanic
serum (100,000 IU) should be injected I/V, I/M, and S/C
every 12 hours, respectively. Local inoculation of
antitetanic serum around the wound is indicated
Treatment
• Relaxation of the muscle tetany:
• Relaxation of muscle to control the convulsions
and avoid asphyxia can be done by
administration of tranquillizers such as
Chlorpromazine (0.4-0.8 mg/kg body weight
intravenously, 1.0 mg/kg BW intramuscularly,
three or four times daily)
Treatment
• Additional supportive treatment:
• Animal should be kept in dark quite well bedded
place.
• If the animal is able to eat, soft laxative diet
should be provided. In advanced cases, feeding
through stomach tube or intravenous is
necessary.
• In some cases, administration of enamas and
catheterization may relieve the animal
discomfort.
Control
• Proper skin and surgical instrument disinfection for
surgical procedures.
• Active immunization can be accomplished with tetanus
toxoid
• it should be treated with 1,500-3,000 IU or more of
tetanus antitoxin, which usually provides passive
protection for up to 2 wk. Toxoid should be given
simultaneously with the antitoxin and repeated in 30 days
• Foals from non-vaccinated mares should receive their first vaccination for
tetanus (tetanus toxoid) between 3 and 4 months of age. The second
vaccination should be given between 4 and 5 months of age, followed by a
third vaccination between 5 and 6 months of age.
• Foals from vaccinated mares should receive their first vaccination for tetanus
at 6 months of age, followed by booster vaccinations at 7 and 8 to 9 months
of age. Tetanus vaccination should be repeated annually thereafter.
• Brood mares should be vaccinated annually 4 to 6 weeks before foaling to
enhance the concentration of anti-tetanus antibodies in their colostrum.
• Adult non-vaccinated horses or horses with unknown status should receive
an initial series of 2 doses of tetanus toxoid administered 3 to 6 weeks apart,
followed by an annual booster.
• Adult vaccinated horses (those that have previously been vaccinated with
the 2-dose regimen), should receive an annual booster.
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