Epidemiology - Leptospira interrogans Complex

Epidemiology

Leptospirosis is the most common zoonotic bacterial disease throughout the world.

◗ Geographical distribution

Leptospirosis is distributed worldwide, occurring with the greatest frequency in the tropics. This is not found in the polar regions. The condition is much more common in the Cannabian islands, the Pacific islands, Central and South America, and Southeast Asia including India.influenza-like illness with fever and myalgias. This phase lasts for 4–7 days. The first stage is followed by 1–3 days’ period of found to multiply in blood and any organ of the body but most commonly in the liver, kidney, and meninges.

◗ Reservoir, source, and transmission of infection

Leptospirosis is a zoonotic disease. Wild mammals are the pri-mary reservoirs of infection. Leptospires infect as many as 160 mammalian species including rats, dogs, cats, cattle, pigs, rac-coons, and other animals. Rodents are most important res-ervoirs, and rats are the most common source of infection worldwide. Leptospirosis in animals is usually a subclinical infec-tion. Leptospires are found for a long period in kidney of these animals; as a result, animals excrete a large number of leptospires in their urine without showing any evidence of clinical disease.

      Urine of the infected animals containing a large number of leptospires is the most important source of infection. Direct contact with the infected urine or urine-contaminated inani-mate objects results in human infections. Animal bedding, soil, mud, and aborted tissues are examples of such inanimate objects contaminated with infected urine. The infection is transmitted to humans:

·           Through intact mucous membrane or conjunctiva;

·           Through minor abrasions on the surface of the skin, water-logged skin,

·           Through the nasal mucosa and cribriform plate

·           By inhalation of aerosolized body fluids; and

·           By congenital infection (from infected mother to fetus through placenta).

The leptospires survive in soil for as many as 24 days and in fresh water for as many as 30 days. Differences between lepto-spires and treponemes are summarized in Table 44-6.