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 oxidation-reduction 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 non-vaccination, 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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