Tetanus

 TETANUS

(Locked Jaw, Saw horse disease)

It is a highly fatal infectious disease of all domestic animals caused by the neurotoxins and characterized by hyper anaesthesia, tetany and convulsions

Aetiology)

The disease is caused by Cl. tetani, which are G +ve long slender rod measuring about 2-5 µm x 0.5 um. Their spores are about 2-3 times the diameter of the cell and are situated terminally giving the 'drum stick' appearance. The organisms are having round ends and can occur in singles or in chains. Some strains have been identified but all are almost antigenically similar. In gelatin stab culture, the growth is good at the bottom of the tube and poor growth near the top. These characteristics are due to the anaerobic nature of the organisms. The spores are resistant to the environmental conditions and can persist in the soil for years.

Epidemiology

Tetanus occurs in all farm animals of the world. Commonly it is seen as a sporadic disease but occasionally it can occur as an outbreak in young cattle, young pigs and lambs and mortality rate is up to 80%. Horses are highly susceptible followed by sheep, cattle and pigs. Carnivores are rarely affected but birds are resistant: Human beings are also susceptible! The organisms are commonly found in the soil and faeces of man and animals especially those of horses.

Pathogenesis)

The organisms go to the deeper part of the wound and multiply when there is Towering of the local tissue oxygen tension) They produce 3 types of toxins, viz. tetanospasmin is the neurotoxin  which is responsible for the disease, tetanolyain is the haemolysin and fibrinolysin. The neurotoxin gets into the peripheral nerve and migrates through the nerve into spinal cord and then to brain. It does not produce any lesion. It may potentiate the normal sensory stimuli leading to the convulsions and tetany The dithis due to hshiyxia becurring as a result of fixation of the muscles of respiration

Clinical findings

Incubation period is of 1-3 weeks and sometimes it can be upto several months. In sheep, the clinical signs can be seen between 3 and 10 days after shearing or docking In all animal species, the clinical findings are almost similar. Initially the locked jaws appearance, i.e, difficulty to open the mouth occurs leading to hampered ingestion of feed and water. There is continuous drooling of saliva. The animal stands with tail raised, erected ears, dilated nostrils and retracted eyelids and feels difficulty in movement Prolapse of the third eyelid is an important early sign seen commonly in horses. Constipation and retention of urine can occur due to inability of the animal to have posture of defacation and micturition. Tetany occurs and as it progresses, the animal adopts a saw horse appearance. In the beginning temperature, heart and respiratory rates are normal. In young animal bloat can occur due to strong and frequent contractions of the rumen.

The animal stands and walks with difficulty and falls down and once it is down. mostly it will not get up. Due to light, sound or other stimuli, the animal becomes hyper anaesthetic and tetany and convulsions occur. Excessive sweating and marked opisthotonus are developed. The hind limbs are stuck out stiffly behind and forelimbs forwards. During tetany or convulsion the animal may dié due to asphyxiation. At this stage, the body temperature is very high (106-108°F) due to convulsions.

In horses and cattle, the course of the disease is of 5-10 days and in sheep and other/ animals it is of 3-4 days. The animals, which survive the convalescent period, recover from the disease but the chances of survival are low. Gross or histopathological lesions are of little importance.

Diagnosis

History of occurrence of wound few days to few weeks before illness, clinical signs of hyper anesthesia, convulsions and prolapse of the third eyelid and serological test, viz. radio immuno assay (RIA), ELISA, etc. have been used for the diagnosis of tetanus)

Tetanus should be differentiated from hypocalcaemic tetany (eclampsia) in mare which is confined to the lactating animal and administration of calcium cures this condition) In acute laminitis in horses, convulsions are not seen. In cerebrospinal meningitis hypersensitivity to sound and movement are not seen, Lactation tetany of

cattle does not reveal prolapse of the third eyelid and bloat are absent. In enzootic muscular dystropy of lambs, tetany does not occur while in enterotoxaemia sudden death of well fed and well grown young calves is noticed.

Treatment

There are 3 main principles of treatment, viz. eliminating the causative agent, neutralizing the toxins and to relax the muscle tetany so as to avoid asphyxiation. To overcome the aetiological agent and to prevent the further release of the toxins, antibiotics like penicillin is given @ 20,000-40,000 IU/kg body weight i/m. If the wound is present, penicillin can be injected around and into the wound also. To neutralize the toxin, antitetanus serum (ATS) is injected @ 3 lakh IU/horse i/v, s/c or im, at 12 hr intervals, 3 times. It is available as ATS in various strengths of 750, 1500, 5000, 10,000 and 50,000 IU/vial. It is advisable to administer ATS into and around the wound and after allowing it for sometime, the wound should be cleaned with hydrogen peroxide. Once the clinical signs are seen, ATS may not be very effective.

To overcome tetany and convulsions, 30-45 g of chloral hydrate, 200-300 ml of /

10% magnesium sulphate solution, i/v, s/c or ataractic drugs like chlorpromazine @

0.88 mg/kg, i/v or 2.2 mg/kg Um can be used for muscle relaxation. If the muscle

relaxants are given properly along with ATS and good nursing care then one can save the life of the animal.) The affected animal should be kept in a dark room with abundant space. Avoiding sound, providing good bedding, giving enema repeatedly, passing the cathetar and removing the urine repeatedly, passing the stomach tube and feeding the animal repeatedly are valuable managemental practices to be adopted for managing the tetanus.

If necessary, tracheotomy can be performed?

Prevention and control

Proper sterilization of surgical instruments is very essential and before surgery, ATS (1500-3000 IU) should be administered. The animals should be vaccinated with tetanus toxoid (which is nothing but formaline inactivated tetanus toxin), @ 5-10 ml i/m repeated after 6-8 weeks and given once more after one year. If necessary, it can be repeated every year. Vaccinating the pregnant ewes in the last 2 or 3 weeks of pregnancy may prevent tetanus in the new born lambs.