The Problem of Floods and Leptospirosis

Leptospirosis is a zoonotic disease which is spread by pathogens belonging to the genus Leptospira. One of the recurrent themes that has been observed in India is the occurrence of deaths attributed to Leptospira outbreaks following floods and heavy rainfall. For example, almost 100 people were suspected to have succumbed to the disease following the 2005 floods in Mumbai ( Naturally, when incessant rains hit Mumbai again in June 2015, the civic and health authorities were worried about the impending crisis of Leptospirosis related deaths (

Public Health Response: Antibiotic Prophylaxis

In order to respond to this impending crisis in Mumbai, there was a large-scale move to provide Doxycycline prophylaxis to the people who were at high risk of contracting Leptospirosis. Despite this measure, if newspaper reports are to be trusted, there were 15 deaths attributed to the disease in the days following the heavy rains in Mumbai.

Where is the evidence?

This raises the question whether antibiotic prophylaxis of Leptospirosis is an evidence-based policy decision or not. In a case control study done in the aftermath of the Surat floods in 2006, it was revealed that overall, the use of prophylactic Doxycycline was not a protective factor when it came to reducing the occurrence of Leptospirosis in people who were exposed to the flood waters.(1)

There are very few studies exploring this particular question and the most credible of these came from the Cochrane Collaboration, in the form of a systematic review that examined the role played by prophylactic antibiotics in prevention of Leptospirosis. (2)

The review covered only three trials, demonstrating the relative paucity of evidence in this domain. Out of these three trials, one trial mirrored the Mumbai situation, where post-exposure prophylaxis was given to people after a flood; the other two trials were related to pre-exposure prophylaxis, one in a group of deployed soldiers in a Leptospirosis endemic area and another in a group of indigenous residents of a Leptospirosis endemic area.

What does it mean?

The review found that there were, overall, no benefits from the use of prophylactic doxycycline in people at high risk of Leptospirosis. However, it reported that there might be some rationale in prescribing to those travelling to endemic regions. The review also found that those who took the prophylactic doxycycline were also more likely to suffer from nausea, vomiting and abdominal pain without accruing significant benefits in prevention of seroconversion or limitation of the sequelae of the disease. It must be mentioned the reviewers noted that the quality of the trials included in the review were unsatisfactory. While the review raises some doubt as to the need for routinely implementing doxycycline chemoprophylaxis in people at high risk of Leptospirosis, it also raises the need to produce more refined evidence, which can be contextualised in the Indian setting.

Risks versus Benefits:

This is especially significant because the mass scale use of antibiotic monotherapy carries an inherent risk of inducing resistance in microbes and the benefits of such a policy should definitely outweigh the potential risks of emergence of antimicrobial resistance. Further research is also needed to understand how the use of Doxycycline on a large scale may impact antibiotic susceptibility of microbes in a particular setting.

RCZI’s Role: Unraveling the Riddles

The RCZI has taken up the initiative to find more answers to the riddle of Leptospirosis by initiating a review to identify the gaps in the knowledge and policy implications of control of Leptospirosis. As the National Leptospirosis Control Programme comes of age, and steps out of its pilot stage and takes on a national role, the RCZI intends to generate evidence and support the prevention and control endeavours of this still under-recognised zoonotic threat.


1. Bhardwaj P, Kosambiya JK, Desai VK. A case control study to explore the risk factors for acquisition of leptospirosis in Surat city, after flood. Indian J Med Sci. 2008 Nov;62(11):431-8. PubMed PMID: 19265232.

2. Brett-Major DM, Lipnick RJ. Antibiotic prophylaxis for leptospirosis. Cochrane Database of Systematic Reviews 2009, Issue 3. Art. No.: CD007342. DOI: 10.1002/14651858.CD007342.pub2. Available from: