Leptospirosis

What is leptospirosis?

Leptospirosis is an infectious disease caused by pathogenic organisms belonging to the genus Leptospira (Leptospires are bacteria which can be either pathogenic (i.e. having the potential to cause disease in animals and humans) or saprophytic (i.e. free living and generally considered not to cause disease), that are transmitted directly or indirectly from animals to humans.

Leptospirosis is a major direct zoonosis.

Human-to-human transmission occurs only rarely.

Which animals are considered as reservoirs of leptospirosis?

• Virtually all mammalian species can harbour leptospires in their kidneys and act as source of infection to human beings and other animals.
• However, cattle, buffaloes, horses, sheep, goat, pigs, dogs and rodents are common reservoirs of leptospires.
• Rodents were the first recognized carriers of leptospirosis. They are the only major animal species that can shed leptospires throughout their lifespan without clinical manifestations, i.e. prolonged carrier state. -They are incriminated as a primary source of infection to human beings.
• Although serovars Ichterohaemorrhagiae, Copenhageni, Grippotyphosa and Ballum have been often associated with rodents, other serovars have also been isolated.
• Pigs and cattle can excrete very large amounts of leptospires in the carrier state (i.e., chronic leptospiral colonization of the renal tubules) and can be an important source of human infection.

How do leptospires enter the body of humans and animals?

• Leptospires can gain entry into humans through cuts and abrasions in the skin, through intact mucous membranes (nose, mouth, eyes) and perhaps through waterlogged skin.
• They may occasionally enter the human body via the inhalation of droplets of urine or via drinking-water.

High risk groups

Agricultural workers such as rice eld planters, sugar cane and pineapple eld harvesters, labourers engaged in canal cleaning operations and livestock handlers are subjected to exposure with leptospires.

Symptoms

• A mild, influenza-like illness.
• Weil’s syndrome characterized by jaundice, renal failure, hemorrhage and myocarditis with Arrhythmias.
• Meningitis/meningoencephalitis.
• Pulmonary hemorrhage with respiratory failure.
• Dengue fever.
• Typhoid.
• Icterus (jaundice).
• Pulmonary hemorrhage.
• Viral hepatitis and other viral hemorrhagic diseases.

What is the mode of transmission of leptospirosis?

Human leptospiral infections result primarily from direct or indirect exposure to the urine of infected animals. Moisture is an important factor of the survival of the leptospires in the environment.

Prevention and control

Prevention

• The infection source.
• The route of transmission between the infection source and the human host.
• Infection or disease in the human host.

Control

• The reduction of certain animal reservoir populations, e.g. rats.
• The separation of animal reservoirs from human habitations by means of fences and screens.
• The immunization of dogs and livestock.
• The removal of rubbish and keeping areas around human habitations clean.
• Encouraging people not to leave food around, especially in recreational areas where rats may be present.

Leptospirosis in India

India with an 8,129 km long coastline and with endowment of plenty of natural resources has one of the major important coastal, agro-ecosystem that supports livelihood of several million people and contributes substantially to the national economy. Due to the rapid ecological changes in the region during the past decade many new zoonotic diseases have emerged and resulted in epidemics leading to signicant morbidity and mortality in humans. Leptospirosis is one among them. The change in the distribution and incidence rate of leptospirosis has occurred proportionately to the alterations in the eco-system. Reclamation of wastelands, aforestations, irrigation, changes in crops and agricultural technology have been important factors. The areas which would have remained free of this infection have converted into potentially endemic zones either by the changes brought out by man or the nature.

The outbreaks of leptospirosis have been reported from coastal districts of Gujarat, Maharashtra, Kerala, Tamil Nadu, Andhra Pradesh, Karnataka, Andamans & Nicobar, Dadar & Nagar Havelli, Daman & Diu & Puducherry from time to time. In addition, the cases have been reported from Goa and Odisha. The high burden of disease has been reported from Andaman & Nicobar, Gujarat (4 districts affected) Kerala (14 districts affected), Maharashtra (4 districts and Mumbai city affected ), Karnataka (9 districts affected) and Tamil Nadu (2 districts and Chennai city affected).

Related Resources

1. Diagnosis, Case Management Prevention and Control of Leptospirosis - National guidelines