Genus Leptospira: Resistance and Pathogenesis

In this article we will discuss about Genus Leptospira:- 1. Introduction to Genus Leptospira 2. Resistance of Genus Leptospira 3. Pathogenesis and Disease 4. Laboratory Diagnosis 5. Treatment.

Contents:

1. Introduction to Genus Leptospira
2. Resistance of Genus Leptospira
3. Pathogenesis and Disease of Genus Leptospira in Man
4. Laboratory Diagnosis of Genus Leptospira
5. Treatment of Genus Leptospira

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1. Introduction to Genus Leptospira:

Leptospirae are small, delicate, slender, flexuous organisms. They are composed of tight coils and curved into a hook at both ends like hockey stick. There are many pathogenic leptospirae. They are highly organised than other bacteria.

In addition to cell wall and cyto­plasm, they contain from one to twelve filaments which are responsible for corkscrew-like motility. They may be seen readily under dark field illumination method in the infected urine or tissue—wriggling and twisting. They grow at 22 to 37°C in liquid media containing animal serum.

2. Resistance of Genus Leptospira:

Leptospira withstands low temperature and survives in water over a period of many months. They are very sensitive to desiccation and acids. Exposure to 56°C kills the organism in 30 minutes. They are lysed in bile.

3. Pathogenesis and Disease of Genus Leptospira in Man:

Infected rats, dogs, cattle, pigs are the main source of leptospira. They discharge them into their surrounding environment (water, soil, foodstuffs) with the urine. Contaminated water and foodstuffs are transmission factors.

Human beings acquire the disease after swimming in contaminated water, drinking contaminated water or milk from infected cows. Leptospiral jaundice is an occupational disease for people in constant contact with water contaminated by rats. The same hazards occur during work in rice fields (Japan, Indonesia).

The pathogenic leptospirae are responsible for the Zoonotic diseases which are subdivided into icteric and anicteric leptospirosis. Icteric leptospirosis (leptospiral jaundice, Weil’s dis­ease) is caused by 1. icterohaemorrhagiae.

This organism enters the host body by the gastrointestinal tract and by injured skin and mucous membrane. The disease is characterised by a sudden onset of high pyrexia, headache and pain in the muscles. The disease involves the central nervous system. Jaundice develops and the liver becomes enlarged and painful.

Haemorrhagic eruptions, nose bleeding, gastric and intestinal haemorrhages may occur and the spleen becomes enlarged. Nephritis and anuria are also observed.

Leptospiraemia developed in the first seven days of the disease plays an important role in the pathogenesis of leptospirosis. At the end of the first week, the organism accumulates in the liver, spleen, lymph node and bone marrow. Then they penetrate the kidneys and are discharged in the urine for 4 to 6 weeks.

Anicteric leptospirosis (Water fever) is characterised by a sudden onset, fever, severe headache and pain in the bones and muscles. The patient looses his appetite. Nausea and lassitude are observed. The spleen and liver are enlarged. A typhoid condition, mental depres­sion; delirium, dulled consciousness and insomnia occur.

4. Laboratory Diagnosis of Genus Leptospira:

1. By direct dark field microscopy of blood smear, by blood or urine culture;

2. By agglutination and lysis reactions with convalescent sera (dilution not less than 1: 400) which are of diagnostic value and by complement fixation test or indirect haemagglutination test.

Prophylaxis can be done by destruction of rats; by general sanitation; by prohibition of infected swimming pool; Prophylactic vaccination with vaccine prepared from a suspension of more common types of Leptospira.

5. Treatment of Genus Leptospira:

Penicillin, chlortetracycline, oxytetracycline are drugs of choice.