Leptospirosis

• Leptospirosis is an infectious disease caused by pathogenic organisms belonging to the genus Leptospira called leptospires, that are transmitted directly or indirectly from animals to humans .
• Leptospirosis is a major direct zoonosis. Human-to-human transmission occurs only very rarely ;
• Leptospires can be either pathogenic (i.e. having the potential to cause disease in animals and humans) or saprophytic (i.e. free living and generally considered not to cause disease) ;
• Leptospirosis occurs worldwide but is most common in tropical and subtropical areas with high rainfall. The disease is found mainly wherever humans come into contact with the urine of infected animals or a urine-polluted environment ;
• The number of human cases worldwide is not known precisely. According to currently available reports, incidences range from approximately 0.1–1 per 100 000 per year in temperate climates to 10–100 per 100 000 in the humid tropics. During outbreaks and in high-exposure risk groups, disease incidence may reach over 100 per 100000 ⁴;
• Leptospirosis may present with a wide variety of clinical manifestations. These may range from a mild “flu”-like illness to a serious and sometimes fatal disease. It may also mimic many other diseases, e.g. dengue fever and other viral haemorrhagic diseases ⁴;
• Icterus (jaundice) is a relatively common symptom in leptospirosis but is also found in many other diseases involving the liver such as the various forms of hepatitis. Other symptoms (see Annex 5) are less common. They are, therefore, often not recognized as a presenting feature of leptospirosis ;
• The diagnosis is confirmed by laboratory tests, but these are not always available, especially in developing countries ;
• For these reasons, leptospirosis is overlooked and underreported in many areas of the world ;
• A doctor can diagnose leptospirosis through a blood test. The bacteria can also sometimes be detected in cerebrospinal fluid (the fluid lining the brain and spinal cord) and urine. Often, two blood tests taken more than two weeks apart are required to make the diagnosis .

Suspect case: evocative epidemiological context and clinical signs and symptoms consistent with leptospirosis: abrupt onset of fever, chills, conjunctival suffusion, headache, myalgia, jaundice, cardiac or renal failure, and pulmonary haemorrhage ⁶.

Probable case: suspected case and the presence of Leptospira immunoglobulins type M (IgM) in one serum sample detected by serology (e.g. Immunoglobulin M (IgM) enzyme-linked immunosorbent assay (ELISA)) ⁶.

Confirmed case: a suspected case confirmed by laboratory test as follows ⁶:

• seroconversion or a four-fold or higher rise in titre detected by serological techniques (e.g. microscope agglutination technique (MAT)2 or IgM ELISA) in consecutive serum samples; or
• detection of Leptospira DNA from a clinical specimen by polymerase chain reaction (PCR); or
• demonstration of Leptospira spp. in tissue.

The incubation period is usually 7–10 days, with a range of 2–30 days ³. The clinical manifestations are highly variable. In general, the disease presents in four broad clinical Categories ³:

• A mild, influenza-like illness;
• Weil’s syndrome characterized by jaundice, renal failure, haemorrhage and myocarditis with arrhythmias;
• Meningitis/meningoencephalitis;
• Pulmonary haemorrhage with respiratory failure.

Symptoms usually start from 5 to 14 days after contact with the bacteria that causes leptospirosis. However, symptoms can begin anywhere from 2 to 30 days after contact. Early symptoms can include ⁷:

• Fever
• Headache
• Muscle aches
• Red eyes
• Vomiting
• Diarrhea
• Abdominal pain
• Jaundice (yellowing of the skin and eyes)
• Skin rash
• Cough.

The typical course of leptospirosis with an acute septicaemic phase followed by the immune phase as shown in Figure 1 .

The diagnosis of leptospirosis should be considered in any patient presenting with an abrupt onset of fever, chills, conjunctival suffusion, headache, myalgia and jaundice. The diagnosis is more difficult when patients present with symptoms of cough, dyspnoea, nausea, vomiting, abdominal pain, diarrhoea, arthralgias and a skin rash  ³.

Conjunctival suffusion and muscle tenderness, most notable in the calf and lumbar areas, are the most distinguishing physical findings  ³.

Suspicion is further increased if there is a history of occupational or recreational exposure to infected animals or to an environment potentially contaminated with animal urine. Once the possibility of leptospirosis has been considered, appropriate diagnostic tests and clinical management should be instituted  ³.

Leptospirosis can be difficult to clinically distinguish from other causes of acute febrile illnesses or their severe complications; diagnosis may therefore be missed or delayed. A detailed history is important for identifying patients who have undertaken activities that place them at risk of exposure to infection. A travel history is also important for delineating possible diagnoses ⁸.

Differential diagnoses of leptospirosis include influenza, pneumonia, arboviral infections (ie dengue, chikungunya, Zika virus, Ross River virus), malaria, typhoid, rickettsia, Q fever, acute viral hepatitis, pyelonephritis and meningitis. Haemorrhagic complications can also mimic meningococcaemia or severe dengue.15 Co-infections have also been reported,16 particularly in post-flooding settings, when outbreaks of multiple diseases (eg leptospirosis, dengue, typhoid) can occur at the same time ⁸.

Leptospirosis most often affects people who work outdoors or with animals, or those who take part in recreational activities involving water or soil, like swimming, boating, and gardening. After floods or heavy rains, anyone who has been in contact with floodwater, contaminated freshwater (rivers and streams) or soil could be at risk for infection ⁷.

Some activities that increase your risk of leptospirosis include:

• Eating food that has been exposed to contaminated water or potentially urinated on by rodents.
• Drinking from potentially contaminated water sources, including floodwater, streams, rivers, or unsafe tap water.
• Bathing or wading in floodwater or contaminated fresh water, especially when putting your head under water or if you have an open wound or scratch.

Leptospirosis is treated with antibiotics, such as doxycycline or penicillin, which should be given early in the course of the disease ⁹.

Intravenous antibiotics may be required for persons with more severe symptoms. Persons with symptoms suggestive of leptospirosis should contact a health care provider ⁹.

The most important way you can prevent leptospirosis is to avoid touching or drinking water that may be contaminated. If that is not possible, follow these steps to reduce your risk of leptospirosis ⁷:

• If you suspect your pet or livestock have leptospirosis, contact a veterinarian. Symptoms of leptospirosis in dogs may include fever, fatigue, lack of appetite and increased or decreased urination. Symptoms of leptospirosis in livestock may include abortion, decreased milk production and weak offspring.
• Treat water to make it safe to drink by boiling or using an appropriate chemical treatment, especially if it has been collected from a source that could be exposed to urine from animals or contaminated by floodwater runoff.
• Cover cuts or abrasions with waterproof bandages or other coverings that seal out water.
• Do not wade, swim, bathe, submerse your head in, or swallow floodwater or any fresh water source that may contain animal urine or be contaminated by floodwater runoff.
• Wear waterproof protective clothing, shoes or boots near floodwater or other water or soil that may be contaminated with animal urine.
• Prevent rodent infestation by keeping food, water and trash in closed containers, and trapping any rodents you see.
• Avoid eating food that rodents may have had access to.