What Is Leptospirosis?


Leptospirosis is a bacterial infection  that can occur in both humans and animals, when the bacteria Leptospira interrogans bypasses immune barriers. Leptospirosis can progress in different ways; a person with the infection may experience common symptoms that are shared by otherdiseases or can be asymptomatic (exhbiting no visible symptoms). Leptospirosis can be treated easily if a diagnosis is made early on. However, if left untreated, the infection can cause severe organ damage. Some end-stage complications of leptospirosis include kidney failure, meningitis (inflammation of the spinal cord and the membrane lining the brain), respiratory distress, liver failure and even death.1 This article will discuss the causes of leptospirosis, mention symptoms that can help you recognise the presence of the infection and outline how leptospirosis is diagnosed and treated. 

Causes of leptospirosis

Leptospirosis is caused by a bacteria known as L. interrogans. It is an example of a zoonotic disease - meaning that the infection is spread from animals to humans. Infection occurs following direct or indirect contact with an infected host animal. There are multipleanimals that can act as a reservoir for L. interrogans, such as bats and seals. Yet, the most common host animal  that causes leptospirosis in humans is the brown rat. These animals carry the bacteria in their renal tubules (nephrons) and shed the pathogen into the environment in their urine. Cuts and abrasions, as well as mucous membranes, such as the conjunctival, oral, or genital surfaces, can serve as entry points for the bacteria. Exposure can occur through direct contact with an infected animal or indirectly, by coming into contact with soil or water that has been contaminated with infected animal urine, especially during heavy rainfall. Therefore, people living in areas with poor sanitation and housing aremost at risk of infection.2 

Signs and symptoms of leptospirosis

Signs and symptoms of leptospirosis range from mild to life threatening. However, as multiple organs are affected, the signs and symptoms of leptospirosis are often confused with other illnesses.

It usually takes 7-12 days before the onset of symptoms after infection, although it can take as littleas 3 days.An infected person is likely to experience fever, chills, and headaches. Muscle pain and tenderness are also common and usually affect the lower back and the calves. In addition, one cardinal symptom that is indicative of leptospirosis and is uncommon in other infectious diseases is conjunctival suffusion.This is when blood vessels in the conjunctiva of the eye dilate without exudating pus. Other signs of infection can include subconjunctival hemorrhage, jaundice and a dry cough. Severe cases of leptospirosis can cause dysfunction of the liver,kidneys, lungs, and brain.2   

Management and treatment for leptospirosis

The standard drug of choice for the treatment of early leptospirosis is doxycycline, an antibiotic. Doxycycline can also be taken as a form of chemoprophylaxis (a way to prevent infection) if a person knows they have been in  contact with an infected animal. For late and severe cases of infection, intravenous penicillin has been considered the first-line treatment. However, ceftriaxone is an anti-biotic that is easier to administer so it is becoming the drug of choice to deal with severe leptospirosis .3


What are the phases of leptospirosis?

There are two types of leptospirosis:anicteric and icteric.

  • Anicteric leptospirosis. This is the mild form of leptospirosis, which progresses as a flu-like illness and can resolve by itself. 90% of all cases of leptospirosis belong to this category
  • Icteric leptospirosis.  Icteric leptospirosis can occur if a person becomes sick again after recovering from anicteric leptospirosis. This is considered the second phase of the infection,which is also known as Weil’s disease. This type of leptospirosis is more severe and canlast for several weeks. It is less common than  anicteric leptospirosis

How is leptospirosis diagnosed?

There are several different methods used in the diagnosis of leptospirosis. These include:

General clinical laboratory findings

A range of laboratory tests can be performed to diagnose leptospirosis:

  • Blood tests can be performed to measure the rate of erythrocyte sedimentation, which will be increased, as well as  the number of white blood cells
  • Liver function tests can reveal an elevated level of aminotransferases, bilirubin, and alkaline phosphatases
  • Renal function tests can show elevated plasma creatinine levels
  • Proteins (proteinuria), hyaline, pus (pyuria), blood (micohaematuria), and granular casts can be found in your urine when performing a urine analysis
  • A lumbar puncture procedure can show increased pressure within the skull and a high level of white blood cells in the cerebrospinal fluid, which surrounds the brainA peripheral blood smear can reveal a high white blood cell count but a low platelet count 

Direct microscopy 

L. Interrogans bacteria are directly observed under the microscope from samples of body fluids from an affected individual. In the dark, using phase contrast microscopes, the bacteria are seen as bright, thin and active motile rods. Specimens are usually stained with a histochemical stain or with immunostaining.


L. Interrogans bacteria can be cultured in a fluid medium. However, it can take nearly three months for these bacteria to grow into a culture that can be observed. Hence, it is impractical to use this method for immediate diagnosis of leptospirosis.

Molecular methods

For rapid diagnosis, direct polymerase chain reaction (PCR) can be used to detect the DNA of L. Interrogans bacteria and therefore, the presence of the bacteria in the body.   


Antibodies formed against L. interrogans can be detected from the sixth day of infection. A microscopic agglutination test (MAT), an enzyme linked immunosorbent assay (ELISA), an indirect haemagglutination assay (IHA), and a leptodipstick assay can be used to detect antibodies and diagnose leptospirosis. 

How can I prevent leptospirosis?

The risk of contracting leptospirosis can be greatly reduced by  avoiding contact with infected animals and with water contaminated with animal urine. Those who are regularly exposed to contaminated water or soil should wear protective clothing and footwear.4

Who is at risk of leptospirosis?

Individuals who come into contact with animals that are likely to contract L. Interrogans, or those who risk exposure to contaminated water, soil and vegetation, are more likely to have leptospirosis . Cases of leptospirosis can rise after tropical cyclones or floods because people  are more likely to encounter contaminated water, drinking it or bathing in it. Individuals with certain occupations, such as those working outdoors or with animals, are more susceptible to the infection. The groups that are at risk include farmers,especially those harvesting sugar canes and bananas,fishermen, people working in the vicinity of contaminated water, vets and slaughterhouse workers. People who participate in recreational activities that involve potential host animals or direct contact with contaminated water sources also have a high risk of infection.5

How common is leptospirosis?

Leptospirosis is found mostly in the South American continent, predominantly in Brazil and Argentina. This is because common animal species that can act as reservoirs for L. interrogans are found there. Yet, cases have been isolated in North America, in Italy, in the Netherlands, in Japan, and in Madagascar.6 It is thought to be the most widespread zoonotic disease in the world. Due to the disease being under-reported, there is no reliable figure that can be attributed to the global incidence of the disease. However, from systematic reviews and epidemiological models, it can be estimated that the number of leptospirosis cases is one million annually, with almost 60,000 deaths.7

When should I see a doctor?

It is advisable to see a doctor if you experience or observe the following: yellow skin and eyes, a rash, an inability to urinate, swollen ankles and eyes, chest pain, and a coug with blood.


Leptospirosis is a bacterial infection caused by Leptospira interrogans, which affects both humans and animals. The bacteria is transmitted from animals, such as bats, to humans. Infected individuals usually present with fever, chills, headache, muscle pain, and jaundice. Leptospirosis is diagnosed using laboratory methods, ranging from direct observation of signs and symptoms to microscopy and molecular methods, such as PCR, ELISA, and MAT, the latter being considered the gold standard. While leptospirosis in the early stages can be treated with doxycycline, late and severe cases are treated with intravenous penicillin.


  1. Centres for Disease Control and Prevention. Leptospirosis. [Online].; 2019 [cited 2023 March 21. Available from: https://www.cdc.gov/leptospirosis/index.html.
  2. Haake DAaPNL. Leptospirosis in humans.” Current topics in microbiology and immunology. PubMed Central. 2015 387. https://pubmed.ncbi.nlm.nih.gov/25388133/ 
  3. Faucher JF HBEJ. The management of lBudihal SVaKP. Leptospirosis diagnosis: competancy of various laboratory tests. Journal of clinical and diagnostic research. 2014; 8. https://pubmed.ncbi.nlm.nih.gov/24596774/ 
  4. NSW Health. A NSW Government website. [Online].; 2021 [cited 2023 March 25. Available from: https://www.health.nsw.gov.au/Infectious/factsheets/Pages/leptospirosis.aspx#:~:text=At%20risk%20groups%20include%20farmers,at%20risk%20of%20leptospirosis%20infection 
  5. Giovanni Cilia FBSAaFF. Insight into the Epidemiology of Leptospirosis: A Review of Leptospira Isolations from “Unconventional” Hosts. Animals. 2021; 11(191). https://pubmed.ncbi.nlm.nih.gov/33466962/ 
  6. Nick Day DF. Leptospirosis: Epidemiology, microbiology, clinical manifestations, and diagnosis. UpToDate. 2022 October. https://www.uptodate.com/contents/leptospirosis-epidemiology-microbiology-clinical-manifestations-and-diagnosis 
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Fuanyi Awatboh

M.Sc. in Epidemiology and Control of Infectious Diseases, University of Buea, Cameroon

I am a professional Quality Assurance Mentor with Global Health Systems Solutions. My job is to enhance HIV testing, Care, and treatment by making sure that all entry points in the three hospitals under me follow standard testing algorithms, have all necessary tools and equipment needed for testing, train testers if need be, and monitor that all positive cases are under treatment among other duties. I have also mentored laboratories to increase their quality of service and standards of operations.

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