Leptospirosis is a disease that actually occurs in animals, but can also be transmitted to humans. In such cases, it is referred to as anthropozoonosis. Leptospirosis often goes unnoticed, but the disease should not be underestimated, because it can lead to death within a few days. How to recognize the symptoms and how to prevent infection, we explain here.
Which pathogen causes leptospirosis?
Leptospirosis is caused by helical bacteria called spirochetes. There are numerous different variants of the pathogen Leptospira interrogans, but they can only be distinguished by antigen-antibody reactions in serum (serovariants). Based on the genetic relationship, the leptospires can still be divided into 21 different species. The other family of spirochetes includes, among others, the pathogens of syphillis. The disease occurs in humans particularly frequently after natural disasters in tropical and subtropical countries, because the pathogens are at home in rats and mice and are excreted in their feces and urine. Spirochetes can survive for months in warm, moist environments such as mud, puddles, or brackish water.
Leptospirosis: How does infection occur?
The pathogens enter the body through minute injuries in the skin and mucous membranes. People can become infected with leptospirosis while swimming, camping or even boating. But the disease is also known to dog owners in this country: To avoid infection with leptospirosis, dogs should not drink from puddles, because in our temperate latitudes leptospirosis often occurs in spring and summer. The pathogens are extremely sensitive to cold and cannot survive outdoors in winter. Leptospirosis may be clustered in certain occupational groups such as canal workers, farmers, laboratory personnel or veterinarians. In Germany, up to 166 cases of the disease have been reported in humans in recent years, although it is assumed that the number of unreported cases is significantly higher. Human-to-human infection has been documented only in rare cases and is considered very unlikely.
Disease progression in two phases
Those who contract leptospirosis do not necessarily become severely ill. Overall, the symptoms of leptospirosis infection can vary widely. A mild course of the disease is just as possible as death within a few days. In between, different courses of the disease are possible, in which different organs can be affected. Often a leptospirosis disease proceeds in two phases:
In the first phase (acute phase), the pathogens are detectable in the blood and cause high fever in the patient. This phase lasts about a week. After the fever has temporarily subsided, the second phase (immune phase) is followed by further episodes of fever, although these are not as high and do not last as long as in the first phase. In the second phase of the disease, the pathogens may have settled in a wide variety of organs and cause late complications there. Most complications occur during this phase.
Symptoms and forms of leptospirosis
The World Health Organization (WHO) has divided leptospirosis into four groups of possible forms of the disease, which is considered the global standard:
- A mild, flu-like form with fever (39 to 40°C), chills, headache, and aching limbs. Often show symptoms of conjunctivitis.
- Weil’s disease (Weil’s disease): This form of leptospirosis shows severe liver and kidney involvement with jaundice, renal failure, bleeding and myocarditis with cardiac arrhythmias.
- Meningitis serous or meningoencephalitis (meningitis): typical signs are severe headache, sensitivity to light or stiff neck.
- Hemorrhage around the lungs with respiratory failure: such cases have been observed mainly during major epidemics and rarely in isolated cases.
Leptospirosis is considered to have a mild course in humans in over 90 percent of cases. The incubation period averages 7 to 14 days (although 2 to 30 days are possible).
Diagnosis of leptospirosis
To diagnose leptospirosis with certainty, either the pathogens must be detected directly (for example, in the urine) or antibodies against the pathogen must be detected in the blood.Antibody detection is performed with the MAT reaction (MAT = microagglutination test), it is considered the WHO standard method. In the MAT, the patient’s sera are diluted and mixed with live leptospiral strains. The presence of antibodies then results in visible clumps of leptospires, which are assessed microscopically. Other tests are available to differentiate leptospirosis from other diseases that must be excluded as part of a differential diagnosis. These include:
- The real flu
- Virus-induced jaundice
- Malaria
- Typhoid fever
- Yellow fever
- Dengue
- Hantavirus
- Non-bacterial encephalitis
Therapy: how is leptospirosis treated?
There is currently no single guideline for the treatment of leptospirosis, but there are nevertheless common procedures. If the disease is detected early, it can be treated well with antibiotics such as doxycycline, penicillin, ceftriaxone, or cefotaxime. In severe courses, methylprednisolone is sometimes used. If the kidneys are affected, dialysis may have to be done. If leptospirosis is detected directly or indirectly, the disease must be reported to the public health department (it is therefore notifiable).
Prevention – what can be done?
To prevent leptospirosis, rats and mice must be controlled. For at-risk groups, it is also advisable to prevent contact with potentially infected animals and water by wearing appropriate protective clothing (for example, gloves and goggles). An active vaccine for humans is available in France, but is not licensed in Germany. Vaccinating your own dog can also ensure that dog owners do not become infected with leptospirosis through their dog. Dogs usually receive vaccine protection with basic immunization, which is refreshed with the annual leptospirosis vaccination.
