Michael Abrahams | Spotlight on leptospirosis

Leptospirosis is a zoonotic (spread from animals to humans) disease with epidemic potential, and it is caused by a spiral-shaped bacterium (spirochete), Leptospira interrogans. Human-to-human transmission occurs only very rarely. More than one million people worldwide get leptospirosis each year, and almost 60,000 of those die from it.

Jamaica is now experiencing an outbreak of the disease, which is not surprising, as the commonest precipitating factor for a leptospirosis outbreak is heavy rainfall and flooding. For example, the largest recorded outbreak of the disease was in Fiji in 2012, following two successive severe flooding events in the western region of the country, which resulted in 1,217 suspected cases and 44 reported deaths. Similarly, as in Jamaica, leptospirosis outbreaks are occurring in the provinces of Cebo and Negros Occidental in the Philippines, after the central part of the country was heavily impacted by Typhoon Tino (international name Kalmaegi) in early November, causing widespread flooding and landslides.

The disease is most often found in tropical and warmer climates and may be problematic even in the absence of a specific natural disaster. For instance, it is a perennial problem in the state of Kerala, India (where it is referred to as “rat fever”), which experiences two monsoon seasons annually, and a surge is now being observed.

Floods are associated with outbreaks of leptospirosis because humans usually acquire the infection through direct contact with the urine or reproductive fluids of infected animals, or through a urine-contaminated environment, and flooding can increase this exposure. Flood water, and the mud and soil in contact with it, are often contaminated with these substances, and the Leptospira bacteria can survive in these environments for weeks to months. So, after these disasters, the likelihood of contracting the disease is increased. Contact with skin (especially if cuts or abrasions are present), or mucous membranes (the linings of the eyes, nasal cavities, and mouth), or ingestion of contaminated food or water will allow the bacteria to enter the body and infect it.

People at risk of contracting the disease include the homeless and people in shelters and other situations where crowding and unsatisfactory sanitation and hygiene are present, as is the case after a disaster such as a hurricane. Others include those engaging in recreational activities such as swimming or wading in contaminated rivers, lakes or canals, and people in affected areas engaging in occupations such as gardening, outdoor cleaning, sewage management, sanitation, maintenance, farming (including working in rice and sugar-cane fields), butchering, working at veterinary clinics and engaging in military operations.

Although commonly associated with rats, almost any mammal can be infected and transmit the infection to humans. However, the symptoms in infected animals vary widely. For instance, cats rarely display symptoms, dogs tend to present with fever, depression, lethargy and loss of appetite, horses with fever and eye infections (uveitis), and cows, goats, sheep and pigs with reproductive issues such as abortion (pregnancy loss) and stillbirth. Even marine mammals can be affected. This year, there has been an outbreak among California’s sea lions. The disease causes severe abdominal pain in these animals as it affects their kidneys and gastrointestinal tracts, and those infected are often seen pressing their flippers against their bellies. Interestingly, animals in the carrier state may shed the bacteria intermittently for many years or even a lifetime.

Leptospirosis presents in two phases. The first is the leptospiremic (or acute) phase. During this phase, the bacteria spread through the bloodstream, causing flu-like symptoms such as fever, chills, headache, muscle aches (particularly in the calf muscles), cough, sore throat, nausea, vomiting, diarrhoea, abdominal pain, and conjunctival suffusion (red eyes). This phase typically lasts five to seven days.

The second phase is the immune phase, during which an immune response occurs, causing inflammation which can lead to organ damage. At this time, symptoms that had resolved can return, signifying more intense complications. These may include a return of fever and headaches, and meningitis (inflammation of the meninges, the lining of the brain and spinal cord), which can cause a stiff neck. Severe illness can develop into Weil’s syndrome, which includes jaundice, kidney failure, and liver damage. Pulmonary haemorrhage (bleeding in the lungs) can also occur. This phase can last for an additional week.

Diagnosis is usually based on blood tests, in conjunction with clinical presentation and epidemiological data (a history of possible exposure and presence of risk factors). The infection is treated with antibiotics, and recovery usually takes a few days to a few weeks, although severe cases can take months, and some people may have persistent symptoms for years. Because the symptoms of leptospirosis may mimic those of other infections, such as influenza, dengue, and other viral haemorrhagic diseases, seeking medical attention at the onset of any of the above-mentioned symptoms is crucial for making the correct diagnosis, preventing severe cases and saving lives.

Unfortunately, although animal vaccines exist, there is no universally available human vaccine for leptospirosis due to the bacteria’s high number of different strains or serovars (over 200) and challenges in identifying a single, broad-spectrum antigen (substance which induces an immune response in the body leading to the production of protective antibodies) that protects against them all. Commercial vaccines against human leptospirosis are available only in a few countries, such as Japan, China, Cuba and France, and are of limited value, only protecting against specific Leptospira strains, and are reserved for high-risk populations and people in specific occupations.

Prevention is key. While in affected areas, avoiding contact with contaminated water, wearing protective clothing and gear and avoiding animals is essential. Wounds should be covered with waterproof dressings if possible. If dead animals are to be handled, gloves should be worn. Water in affected areas should be boiled and treated before being consumed. Attention must be paid to handwashing and other hygienic practices. Surfaces in contact with food must be cleaned and disinfected, and food protected from rodents. Rodent control and effective sanitation measures must also be employed. We must protect ourselves.

Michael Abrahams is an obstetrician and gynaecologist, social commentator, and human-rights advocate. Send feedback to columns@gleanerjm.com and michabe_1999@hotmail.com, or follow him on X , formerly Twitter, @mikeyabrahams