Understanding Leptospirosis

Leptospirosis, also known as fall fever or mud fever, affects both animals and humans. This disease occurs worldwide, and the highest prevalence is in tropical climates and in warm and wet environments with poor sanitary conditions (6). Leptospirosis is an increasingly recognized cause of acute febrile illness throughout the tropical and sub-tropical regions of the world (2).Leptospirosis is presumed to be the most widespread zoonosis in the world; it is caused by pathogenic spirochaetes of the genus Leptospira (1–4). Humans are accidental hosts and usually become infected through contact with water or soil contaminated by the urine of infected animals such as rodents, dogs, cattle, and pigs. Exposure of skin or mucous membranes to leptospires can lead to infection. Clinical signs and symptoms are variable and range from subclinical to potentially fatal manifestations. Leptospirosis should be suspected in febrile children with contact with flood water (1). Interestingly, in this setting, many exposed people have asymptomatic seroconversion and some also undiagnosed fever; a small but important minority may develop severe disease. (3) The significant household clustering of Leptospira infection in slum communities, indicating that the household environment and related factors are important determinants for transmission of urban leptospirosis (4)

Leptospirosis is an emerging zoonosis that is often under-recognized in children and commonly confused with dengue in tropical settings. Unrecognized leptospirosis can be a significant cause of ‘‘dengue-like’’ febrile illness in children. Increased awareness of pediatric leptospirosis, and an enhanced ability to discriminate between leptospirosis and dengue early in illness, will help guide the appropriate use of healthcare resources in often resource-limited settings. In a semi-rural region of Thailand, leptospirosis accounted for 19% of the non-dengue acute febrile illnesses among children presenting during the rainy season. None of the children with leptospirosis were correctly diagnosed at the time of hospital discharge, and one third (33%) were erroneously diagnosed as dengue or scrub typhus (2)

Heavy rains were followed by an increase in laboratory-confirmed cases of Leptospirosis (5) Leptospirosis has become an urban health problem as slum settlements have expanded worldwide.  Deficiencies in the sanitation infrastructure where slum inhabitants reside were found to be environmental sources of Leptospira transmission (7)

This disease continues to have a major impact on people living in urban and rural areas of developing countries with inestimable morbidity and mortality.  It is widely recognized that the incidence of leptospirosis is remarkably underestimated and the disease underdiagnosed in endemic regions. Leptospirosis is estimated to affect tens of millions of humans annually with case fatality rates ranging from 5 to 25%. In endemic areas of leptospirosis, factors such as lack of sanitary conditions, mud flooring, together with rainy seasons and flooding catastrophes contribute to periodic outbreaks (3,8).

 Reference:

1. S Karande, M Bhatt, A Kelkar, M Kulkarni, A De, A Varaiya : An observational study to detect leptospirosis in Mumbai, India, 2000: Arch Dis Child 2003;88:1070–1075
2.  Libraty DH, Myint KSA, Murray CK, Gibbons RV, Mammen MP, et al. (2007) A Comparative Study of Leptospirosis and Dengue in Thai Children. PLoS Negl Trop Dis 1(3): e111 doi:10.1371/journal.pntd.0000111
3. ER Cachay and JM Vinetz: A Global Research Agenda for Leptospirosis: J Postgrad Med. 2005 ; 51(3): 174–178
4. Maciel EAP, de Carvalho ALF, Nascimento SF, de Matos RB, Gouveia EL, et al (2008) Household Transmission of Leptospira Infection in Urban Slum Communities. PLoS Negl Trop Dis 2(1): e154. doi:10.1371/journal.pntd.0000154
5. Yu-Ling Chou, Chang-Shun Chen, and Cheng-Chung Liu : Leptospirosis in Taiwan, 2001–2006 : Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 14, No. 5, May 2008
6. Ken Brown and John Prescott: Leptospirosis in the family dog: a public health perspective: CMAJ • February 12, 2008 • 178(4)
7. Reis RB, Ribeiro GS, Felzemburgh RDM, Santana FS, Mohr S, et al. (2008) Impact of Environment and Social Gradient on Leptospira Infection in Urban Slums. PLoS Negl Trop Dis 2(4): e228. doi:10.1371/journal.pntd.0000228
8. M J Pappachan, M Sheela, K P Aravindan : Relation of rainfall pattern and epidemic leptospirosis in the Indian state of Kerala: J Epidemiol Community Health 2004;58:1054–1055