This is a bacterial infection resulting from exposure to the Leptospira interrogans bacteria, and therefore is also known as leptospirosis. The vast majority of cases are mild and recovery is complete. This is fortunate as the there are millions of infections every year worldwide as it is probably the most common infection passed from animals to humans. Thankfully this infection is rare in the UK and only the severe form is generally known as Weil’s disease.
Infection is caused by exposure to the bacteria in drinking water or while swimming in freshwater, usually in the presence of urine from an infected animal. The bacteria enter at certain locations, including broken skin, membranes lining the airway, mouth, lungs and sometimes via sexual intercourse. Dry undamaged skin is a good barrier to the bacteria and the risks from saltwater are almost nil.
Human leptospirosis can be difficult to recognise as symptoms can vary considerably between patients, depending on their age and health, the strain of bacteria and the amount of bacteria that enter the body. The time from infection to symptoms is typically 3 to 21 days, with most patients developing illness after about 3 to 14 days. The symptoms classically then occur in 2 phases and affect the whole body.
In mild cases the infection is similar to flu, with both phases lasting 3-5 days with slight recovery in the middle. Not all symptoms may be present but a severe headache is common and other symptoms include: sore throat, dry cough, red eyes, muscle pains, fatigue, fast heart rate, nausea and vomiting. There may also be symptoms similar to that of meningitis. These include a red non blanching rash anywhere on the body, neck stiffness and an aversion to light similar. To tell whether the rash is non blanching, push a glass against it and if it is non blanching then the rash will not become paler under the glass. This is the same for the rash in meningitis. Both conditions need immediate medical assessment.
In severe cases, the illness develops rapidly and there may or may not be a period of apparent recovery. Symptoms include severe forms of the above and also jaundice (yellowing of the skin and whites of the eyes), chest and abdominal pain, kidney and liver problems and psychological changes, such as depression and agitation. Bleeding from mouth and eyes, organ failure and death can also occur, but with medical treatment the chances of survival are good.
On average in Europe and mainland USA about 20% of wild rats carry strains of leptospira, but other rodents can be carriers. The single most important factor in avoiding infection is knowing where infection is likely and avoiding these locations. Hence local knowledge is important, but also infection requires close contact to infected water. Simply being near and infected animal carries no risk. Where someone has a ‘risk exposure’ and then shows characteristic illness during the incubation period (3 to 21 days), a blood test for leptospirosis should be requested and antibiotics started at the same time.
Remember that water can also enter the mouth via the hands, so even when preparing for a dive in at risk areas, when washing equipment or wading through shallow water, good hygiene and covering broken skin with waterproof dressings should be followed.
Where can I find more information on leptospirosis?