By Kelly A. Reynolds, MSPH, PhD
The summer of 2017 was wrought with devastating hurricanes in the Atlantic and Gulf of Mexico. As communities work to rebuild infrastructure and their lives, additional public health impacts continue to unfold, including concerns of microbial outbreaks. One post-disaster hazard to both humans and animals includes leptospirosis, a dangerous bacterial infection associated with bathing in or consuming contaminated water.
What is leptosporosis?
Leptospirosis is a bacterial infection, caused by Leptospira. There are over 200 known pathogenic strains that cause disease in animals and humans. The bacteria can be free-living in the environment, surviving for weeks or months in water, or they may be closely associated with an animal host carrier. A wide variety of domestic and wild animals can carry the Leptospira bacterium, including cows, pigs, dogs, horses and rodents. The organism is typically spread through the urine of infected animals that contaminates soil, water and food.
Rodents are most often implicated as sources of contamination during waterborne outbreaks. They shed millions of Leptospira cells in their urine and are in frequent contact with recreational and drinking-water source supplies. Cattle are also significant sources, contributing billions of bacterial cells to the environment due to the large volume of urine excreted.(1) Animals and humans infected with Leptospira may be contagious but show no outward signs of illness. For others, symptoms are similar to the flu, including fever, headache, chills, vomiting, jaundice, diarrhea and rash.(2) Similarly, symptoms in dogs range from fever, vomiting, stomach pain, diarrhea, loss of appetite, weakness, depression, muscle pain and stiffness or the inability to have puppies.
Once infected, signs of disease may begin as early as two days following exposure; the organism could take up to a month to incubate and be noticed. Sometimes leptospirosis symptoms subside but flare up again after a period of time. The second round of illness, known as Weil’s disease, is typically much more serious and can rapidly progress to kidney or liver failure or meningitis. Although rare, one to five percent of Weil’s disease cases result in death. The severity of symptoms is highly dependent on the virulence of the bacterial strain and host susceptibility. In the developing world, many people are misdiagnosed with malaria, dengue or other related illnesses. Misdiagnosis can lead to a delay in proper treatment and worsening or deadly outcomes.
Water is the primary vehicle of transmission for Leptospira. Flooding events can increase contamination and exposure probabilities since transmission to humans is through the skin, eyes, nose or mouth. Open wounds create vulnerable pathways for infection as does wading in, or drinking, contaminated water. Persons at highest risk of leptospirosis are those participating in adventure racing or triathlon events which often involve recreational water exposures. In addition, anyone exposed to flood waters is at increased risk. Given its association with animal urine, Leptospira is present in soil and water and the disease is endemic in many regions.
Drinking water and urban water supplies have been linked to several outbreaks. Drinking-water consumption has been associated with leptospirosis as early as 1984, following an outbreak in Italy, with 33 confirmed illness cases and two deaths.(3) Exposure was from a fountain believed to be contaminated by a drowned hedgehog. In 2002, another outbreak involved 69 residents from a nurses hostel in India, with trucked-in drinking water stored in an underground tank. A high population of rats and mice in the region were thought to be the source of contamination. In both the developed and developing world, re-contamination of treated water is a concern with this pathogen. Stored water can provide an environment that is time and temperature permissive for bacterial growth and increased contamination, particularly in warm climates.
In January 2013, leptospirosis was listed as a nationally notifiable disease, meaning that the Council of State and Territorial Epidemiologists (CSTE) recommends state health departments to report cases to the CDC’s National Notifiable Diseases Surveillance System (NNDSS). Increased surveillance and reporting will help to identify trends in the emergence of leptospirosis. The US reports approximately 40-120 human cases per year but increased weather events are expected to drive these numbers higher.
Most recently, the impacts of Hurricane Harvey in Houston, TX and the Gulf Coast region and Hurricane Irma in the Virgin Islands and Florida are being closely monitored relative to microbial disease outbreaks. Hurricane Maria’s public health impact in Puerto Rico is still being assessed. The disaster is currently thought to have caused at least 45 deaths, where a third of the community remains without running water and 90 percent without electricity. Reports from the state epidemiologist in Puerto Rico indicate 74 suspected leptospirosis cases and four related deaths.(4) (One death was associated with consumption of contaminated water from a nearby stream in the absence of running household water and scarce bottled water supplies.(5)
Global climate change is believed to be contributing to the emergence of leptospirosis, where increased temperatures extend survival times, enhance growth rates and enable habitat expansion for the bacteria. As we continue to learn how to better prepare for future disasters, we must consider the impact of contaminated drinking water and the need for point-of-use treatment solutions.
Treatment and control strategies
Clinical diagnosis and treatment of Leptospira infections can be difficult. Antibiotics such as doxycycline or penicillin are available but most effective only if given soon after symptoms begin. Diagnosis may be delayed due to similar morbidity to other common diseases. Often, sick individuals are unaware of the rapid progression of leptospirosis. A vaccine is available for dogs but there is not yet one approved in the US for prevention of the disease in humans. Humans may be given antibiotic treatment prophylactically in instances of suspected exposure. Even with treatment, symptoms may last several days to several weeks. If left untreated, patients may suffer for several months and are at increased risk of severe or fatal outcomes.
Prevention of leptospirosis is preferred and begins with consumption of only clean water. Even safe, treated water, however, is subject to contamination during distribution and storage. Natural disasters, including earthquakes and hurricanes, lead to flooding and disturbances in the drinking-water infrastructure that may result in long-term contamination of water post-treatment.
Fortunately, Leptospira are relatively easy to kill in water. For decontamination of small, personal water supply needs (i.e., during backpacking excursions or temporary emergency situations), drinking water can be boiled or treated with iodine or chlorine tablets at the point of use. Portable UV sterilizers, such as UV pens, can also be effective when used as directed. Leptospira ranges from 0.2 to 0.3 microns in diameter and from six to 30 microns in length. Thus, due to its small diameter and long, spiral shape, filters must have a pore size of less than 0.1 micron to remove Leptospira. Likewise, for routine POU water treatment, systems rated for removal or disinfection of bacteria and designed with a pore size of less than 0.1 micron are expected to be effective against Leptospira and are essential for protection during unexpected events leading to unintended consequences.
(1) Barragan V, Nieto N, Keim P, Pearson T. Meta-analysis to estimate the load of Leptospira excreted in urine: beyond rats as important sources of transmission in low-income rural communities. BMC Res Notes. 2017;10(1):71. doi:10.1186/s13104-017-2384-4.
(2) Centers for Disease Control and Prevention. Signs and Symptoms | Leptospirosis | CDC. https://www.cdc.gov/leptospirosis/symptoms/index.html. Accessed October 19, 2017.
(3) Cacciapuoti B, Ciceroni L, Maffei C, et al. A waterborne outbreak of leptospirosis. Am J Epidemiol. 1987;126(3):535-545. http://www.ncbi.nlm.nih.gov/pubmed/3618584. Accessed October 21, 2017.
(4) Moreno C. Doctors Fear A Potentially Deadly Disease Outbreak In Puerto Rico | Huffington Post. https://www.huffingtonpost.com/entry/leptospirosis-outbreak-puerto-rico-hurricane_ us_59e905aae4b0f9d35bc969ac. Accessed October 21, 2017.
(5) Press CN. Puerto Rico investigates post-hurricane disease outbreak – CBS News. https://www.cbsnews.com/news/puerto-rico-hurricane-maria-disease-outbreak-leptospirosis. Accessed October 19, 2017.
About the author
Dr. Kelly A. Reynolds is an Associate Professor at the University of Arizona College of Public Health. She holds a Master of Science Degree in public health (MSPH) from the University of South Florida and a doctorate in microbiology from the University of Arizona. Reynolds is WC&P’s Public Health Editor and a former member of the Technical Review Committee. She can be reached via email at email@example.com