What is leptospirosis?
Leptospirosis, or Weil’s disease, is an infectious disease caused by Leptospira bacteria. It is a zoonotic infection meaning that it is transmitted from animals to humans. Leptospirosis in humans is mainly contracted through either direct or indirect contact with urine of the infected animal. It can also be spread through contact with the infected animal’s kidneys or products of conception. The infected animals are usually asymptomatic but leptospirosis can be a very severe infectious disease in humans and even lead to multi-organ failure. Overall leptospirosis is a rare infection but the incidence is on the rise. Apart from occupational hazards among animal workers, the infection can be transmitted though pets, pests like rats and contaminated fresh water sources.
Leptospira Bacteria Infection
Leptospirosis can be divided into two distinct syndromes – anicteric and icteric. The anicteric syndrome is self-limiting where the immune system is able to deal with the infection. Treatment may be prescribed but the disease does not usually progress to very severe complications. The iceteric syndrome is the more severe manifestation which can lead to multi-organ failure. It is also known as Weil’s syndrome which should not be confused with Weil’s disease, another name for leptospirosis.
Leptospira bacteria enter the human body either through :
- a break in the skin or mucous membranes
- inhaled bacteria in the lungs
- placenta during pregnancy
The bacteria quickly enterW the bloodstream and spread throughout the body. It multiplies within small blood vessels at various sites in the body. This can cause inflammation of the blood vessel wall known as vasculitis. The blood flow to the area is affected to some degree which in turn can cause some localized symptoms depending on the organ affected. This is the period of acute infection marked by generalized symptoms such as fever, chills and muscle pains (myalgia). At this point there are no antibodies in the blood formed against the bacteria.
During the immune phase, the immune system forms antibodies against the multiplying bacteria. This allows the immune system to launch a more coordinated attack against the bacteria and eliminate it from the body. Some bacteria may be able to escape the immune action and continue to reside in certain areas like within the eye, kidney and brain for prolonged periods of time.
Weil’s syndrome, or icteric leptospirosis, is the most severe form of leptospirosis. It is marked by major dysfunction of several organs and there may even be multi-organ failure. The kidneys, liver and brain are the most severely affected. The mortality rate significantly increase in Weil’s syndrome.
The symptoms of leptospirosis develops on average about 10 days after infection. However, it may arise as early as 2 days or as late as 4 weeks after infection. The initial stages, anicetric phase, tends to present with generalized infectious symptoms and some localized symptoms. It may resolve completely but can recur with Weil’s syndrome (icteric phase) where there are also the symptoms of organ failure.
The main symptoms of leptospirosis includes :
- Muscle pain
- Cough (sometimes blood-streaked sputum)
- Chest pain
- Nausea and vomiting
- Abdominal pain
- Skin rash
- Enlarged lymph nodes
These symptoms may often be mistaken for many other more common infectious diseases. Less common symptoms at the outset which may be more indicative of leptospirosis includes :
- Red eyes
- Enlarged spleen and/or liver
- Altered consciousness
- Peripheral neuropathy
- Blood in urine
- Pus in urine (cloudy urine)
- Protein in urine (foamy urine)
- Bleeding abnormalities like nosebleeds
Weil’s syndrome may present with the symptoms of liver and kidney failure and sometimes meningitis.
Causes of Weil Disease
Leptospirosis (Weil disease) is caused by an infection with leptospires, bacteria known belonging to the genus Leptospira. There are several different pathogenic species of these bacteria. The main pathogenic species which causes leptospirosis in humans is Leptospira interrogans. These naturally occurring bacteria are motile and found in fresh water and mud. It can infect a number of different animals and is usually carried in the kidneys. Leptospira bacteria do not usually cause symptoms in these infected domestic and wild animals. It is then transmitted to humans through contact with the infected animal’s urine.
Animals that transmits Leptospira
A number of animals can be infected with the Leptospira bacteria. Although it is an occupational hazard, like in farm workers dealing with infected cattle or pigs, most incidents occur with recreational contact with animals such as rats and dogs. Contact with the urine increases the chances of infection. Although just about any animal can be infected with Leptospira bacteria, the following mammals are the most likely to transmit the infection to humans :
People coming into contact with infected animals are at risk of contracting the infection. It is passed though contact with the animal’s urine or water and soil contaminated with the urine. People who may be at greater risk of contracting the infection are those who have close contact with animals, their organs and products of conception. However, drinking or swimming in contaminated water can also lead to human transmission despite their having been no direct contact with the animal. Infection is often caused in the home environment by making contact with infected pets. However, farm workers and related occupations are at a greater risk in general.
Tests and Diagnosis
A diagnosis of leptospirosis is made with blood tests. There are two types of tests that can be conducted :
- Antibody blood test to confirm the body’s immune response to the bacteria.
- Blood culture where the bacteria are grown in a laboratory from a sample of the patient’s blood.
A number of other tests also need to be conducted to evaluate the pathological effects of leptospirosis. This is mainly to evaluate liver and kidney function with tests such as liver function test (LFT) and urinalysis respectively.
Administration of antibiotics is the main mode of treatment for leptospirosis. It can also be used as a short-term preventative measure (prophylaxis) in patients who are likely to contract the infection. Although anicteric infection is self-limiting, leptospirosis should not be left untreated as it can develop into the more severe Weil syndrome (icteric) and lead to a host of potentially fatal complications.
The antibiotic of choice in treating leptospirosis is doxycycline, along with ampicillin and amoxycillin in mild infections. It can be administered orally in these cases. For more severe infections, penicillin G or ampicillin are administered intravenously. Other antibiotics that may be considered includes erythromycin, cefotaxime and ceftriaxone.
Prevention of Leptospira Infection
Leptospirosis vaccines have not proven to be extremely effective in humans but is available in some countries. It offers short term protection and has to be administered every year. However, animal vaccines are very effective and may be used for immunization campaigns. Low dosage doxycycline may be used as a preventative measure in high risk patients but for a short period of time. Other preventative measures include :
- Avoiding fresh water sources in high risk areas.
- Always keep cuts properly covered especially if in contact with fresh water sources.
- Handling animals like rodents with gloves.
- Wash hands thoroughly after touching animals.