Summary

Leptospirosis is a potentially fatal zoonosis which is caused by spirochaetes of the genus Leptospira, considered as the most globally widespread zoonotic illness. It is now classified as an emerging or re-emerging infectious disease. At present, Sri Lanka has been identified as a leptospirosis endemic country with high (54) estimated annual incidence rate (AI) per 1,000,000 population. Sri Lanka has experienced 3 major epidemics in 2003, 2007-2008 and 2011 respectively during the last 15 years and the 2007-2008 epidemic was the largest ever reported epidemic with 7406 suspected cases and 204 deaths. The leptospirosis disease morbidity have a considerable impact on economy as the men aged 20-59 years are known to be at high risk of being infected with leptospirosis. The relative risk of dying is higher among men above 40 years which may have a negative effect on the productivity of leptospirosis endemic countries, especially affecting the agricultural economy. The spectrum of symptoms of leptospirosis is extremely broad ranging from asymptomatic, mild to severe. Many infections (85-90%) are asymptomatic, mild, anicteric febrile episodes; however 10-15% develop a severe form of the disease with multiple organ dysfunction.

Within pathogenic species, there are more than 200 serovars known to cause disease in different categories of hosts. The prevalence of each serovar and the serovars which cause severity could be different in each geographic region in the world. At present, there is limited information on genotypes and serovars prevalent in Sri Lanka. Recent studies in Sri Lanka have identified four pathogenic species, namely L.interrogans, L.kirschneri, L. borgpetersenii and L.weilii from patient isolates. Serogroups such as Tarassovi, Autumnalis and Pyrogenes have been described as the most common serogroups among human infections. L. borgpetersenii, L.kirschneri and L.interrogans have been identified in reservoir hosts (cattle) in Sri Lanka. The pathogenic serovars or Leptospira species which could cause severe leptospirosis is not yet defined

Despite the considerable morbidity and mortality due to leptospirosis, to date there is no vaccine available for human use in Sri Lanka. Even though there are licensed veterinary vaccines used in other countries such as Australia and New Zealand, none is available in Sri Lanka. It is noteworthy that such vaccines are developed based on the most prevalent serovars in those countries. The use of such veterinary vaccines has shown a reduction of leptospirosis infections among farming communities reflecting an indirect protective effect on humans. The knowledge on pre-existing/ circulating serovars/ species is very important for a vaccine to be either deployed or for a novel vaccine to be developed. Thus the information that would result in from the proposed study would not only be gathering fundamental and epidemiological information but more importantly a pre-requisite for either the deployment or for future development of a vaccine against leptospirosis

Objectives

1. General Objective:

   To determine the pathogenic Leptospira serovars and genotypes in severe leptospirosis in Sri Lanka

2. Specific Objectives

   1. To identify the Leptospira spp in patients with severe and mild leptospirosis infections
   2. To determine the probable serovar(s)/serogroup(s) associated with severe and mild leptospirosis
   3. To determine the DNA relatedness between serogroups and serovars among the species isolated from these human leptospirosis infections

Major Equipment Facilitated by Grant