Aug 27, 2008

Animal-to-man leptospirosis on upswing

By LJ Anderson / Daily News Columnist

On the face of it, it sounded like the adventure of a lifetime: compete in the Eco-Challenge-Sabah 2000 multi-sport endurance race in the Segama River in Borneo, Malaysia. And, it might well have been, but the results from the race also included confirmation by the Centers for Disease Control and Prevention (CDC) of a leptospirosis outbreak, with 80 of 189 athletes contacted by the CDC (304 competed) meeting the case definition for leptospirosis, and 29 of those hospitalized. It pays to know what pathogens might be in the water when you engage in adventure travel, and especially if you immerse yourself in unfamiliar waters.

Leptospirosis is a disease caused by exposure to Leptospira, bacteria that live freely or attach to an animal host. Passed from animals to humans, people may contract it via skin abrasions or the nose, eyes and mouth from contaminated fresh water or soil where infected rodents have excreted urine. In the developing world, leptospirosis is primarily a rural disease seen in humid and tropical regions, but increasingly, it is appearing in residents of rat-infested urban slums. The resulting disease causes a flu-like illness, ranging from mild to severe. It is often misdiagnosed, and if left untreated, may lead to serious problems, including renal failure, and can be potentially fatal. Leptospirosis is an underreported disease whose true prevalence is unknown.

For Americans, it tends to be associated with recreational exposure but leptospirosis in U.S. slums has also been reported. Several states, including Hawaii and California, voluntarily collect data, although notification to the CDC is not required. Nationally, it affects less than 100 to 200 people per year, and half of those cases are in Hawaii. For example, in 2004 heavy rains caused overflow from a nearby stream to flood a lab at the University of Hawaii. After wading into his flooded laboratory in sandals, a professor developed fever, chills and vomiting - common symptoms of leptospirosis. Surfers swimming near the mouth of rivers have also contracted the disease, and warnings regarding leptospirosis are posted at freshwater streams throughout Hawaii. Cases in California have mostly been associated with freshwater recreational exposure, and include settings such as swimming in muddy ponds to duck-hunting in flooded rice fields. Sometimes cases are discovered after travelers return from exotic locations. For example, several Americans who had river-rafted in Costa Rica were diagnosed with leptospirosis after exhibiting symptoms upon their return home.

Alan Katz, MPH, MD, is graduate chair and professor of epidemiology in the Department of Public Health Sciences at the University of Hawaii in Honolulu. His research interests include leptospirosis.

Q: Why is leptospirosis a reportable disease in Hawaii?

A: From the mid-1970s until the cessation of national surveillance for leptospirosis in 1995, Hawaii consistently had the highest annual incidence rate of leptospirosis in the United States. Since we have long recognized the occurrence of leptospirosis in Hawaii, we have continued to keep it reportable so we can keep track of trends in disease occurrence.

Q: How big of a public health problem is leptospirosis in the rest of the United States, and worldwide?

A: Leptospirosis is considered the most widespread zoonotic illness - an illness transmitted from animals to people - in the world. The World Health Organization recently classified leptospirosis as a "re-emerging" infectious disease. There have been recent outbreaks in Nicaragua, Borneo, Ireland, Israel, Costa Rica, Brazil and India. In the summer of 1998, there was an outbreak in Illinois among triathletes who were exposed to water in Lake

Springfield.

Q: How does leptospirosis usually present itself in a patient, and is it difficult to diagnose?

A: This is one of the key challenges. Leptospirosis has protean (ed note: changes form) manifestations and may go unrecognized due to its nonspecific signs and symptoms.

Confirmation of the diagnosis is also difficult because of problems associated with isolating the organism, and with serological testing during the acute phase of the illness.

Common presentations are flu-like symptoms: fever, chills, headache, muscle ache, decreased appetite, nausea and vomiting. It can also present as meningitis or pneumonia.

Q: Are there typical situations in which people have been initially exposed to Leptospira?

A: Most of the cases we see in Hawaii relate to recreational exposures: swimming in fresh water (the organism doesn't survive well in brackish water so the ocean is safe), hiking (from exposures to wet mud that contains infected animal (usually rat urine), or occupational exposures.

Taro farmers are at increased risk in Hawaii, and rice farmers are at increased risk in Asian countries due to the way the crops are surrounded with increased amounts of fresh water.

Q: Do you have any advice for visitors to Hawaii with regard to preventive measures?

A: Some general prevention measures listed on our Department of Health Web site (http://hawaii.gov/health/about/reports/leptobrochure.pdf) include: "Do not swim or wade in freshwater streams or ponds in Hawaii, especially when you have open cuts or sores. Swimming with your head underwater also increases your risk of infection through the eyes, nose and mouth. Do not drink pond or stream water without boiling or chemically treating it."

The incubation period for leptospirosis is usually seven to 12 days, so if you become ill after swimming or hiking in Hawaii, let your doctor know. Early antibiotic treatment can help shorten the course of the illness.



LJ Anderson writes on health matters every Wednesday.

She can be reached at lj.anderson@yahoo.com or www.ljanderson.com.