Leptospirosis, Biology


It is zoonotic disease characterized by interstitial nephritis, haemolytic anaemia and abortions.

Etiology: The disease is caused by Leptospira interrogans. Severe form of disease occurs in calves and lambs whereas adults show less severe form. In dairy animals, abortion occurs in about 30% of affected animals.

Pathogenesis: The organisms reach liver from the intestinal tract and multiply there. The organisms produce haemolysin which causes intravascular haemolysis, haemoglobinuria, jaundice and escape of blood in to milk. Abortions occur in later stage of pregnancy when organisms enter into placenta.

Clinical signs: It occurs in acute, subacute or chronic form in dairy animals. In acute form, animals have fever, anorexia, acute haemolytic anaemia, haemoglo­binuria, jaundice, petechial haemorrhages on mucosae, dyspnoea, abortions and blood in milk.

The pregnant animals usually abort. In human beings, fever, haemoglobinuria, jaundice and pale mucous membranes are common symptoms.

Diagnosis: It is diagnosed by clinical symptoms and confirmed by isolation of organisms from blood, kidney, pleural fluid of aborted foetus, or urine. These materials can be inoculated to hamsters, which die within 2 days in positive cases. Serological tests like agglutination and fluorescent antibody tests can also be used for its confirmation. The disease is to be differentiated from nutritional haemoglobinuria (PPH). The later is associated with no rise in body temperature; milk is normal and is seen mostly 4-6 weeks before and after parturition. In bacillary haemoglobinuria, abortions are absent and milk is normal. Anaplasmosis does not reveal haemoglobinuria while animals have history of tick infestation. In babesiosis, milk is normal and animals have history of tick infestation like anaplasmosis. In chronic copper poisoning, body temperature and milk remain normal.

Treatment: The cases should be treated before there is damage of liver or kidney. For cows, 10-15 mg streptomycin can be given per kg body weight intramuscularly twice daily for 3-4 days. If organisms are present in urine, it is to be given in double doses. Tetracyclines @ 2-5 mg/kg body weight BID for 4 days are also effective. As supportive therapy, liver tonics and haematinics should be prescribed for early recovery. If animals are very anaemic, 6-8 liter of blood can be transfused to save life.

Control: Control of leptospirosis is difficult owing to involvement of wild animals and rodents in the disease transmission. Vaccines are available against this disease for dogs. But vaccine against cows or buffaloes or other farm animals is not available in India.

Posted Date: 9/19/2012 1:46:16 AM | Location : United States

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