Leptospirosis
Leptospirosis | |
---|---|
Other names | Rat fever, dengue[9] |
Prevention | Personal protective equipment, hygiene measures, doxycycline[7] |
Treatment | Doxycycline, penicillin, ceftriaxone[8] |
Prognosis | Risk of death ~7.5%[10] |
Frequency | One million people per year[7][11] |
Deaths | 58,900 per year[11] |
Leptospirosis is a
More than ten genetic types of Leptospira cause disease in humans.
Efforts to prevent the disease include protective equipment to block contact when working with potentially infected animals, washing after contact, and reducing rodents in areas where people live and work.[7] The antibiotic doxycycline is effective in preventing leptospirosis infection.[7] Human vaccines are of limited usefulness;[15] vaccines for other animals are more widely available.[16] Treatment when infected is with antibiotics such as doxycycline, penicillin, or ceftriaxone.[8] The overall risk of death is 5–10%.[10] However, when the lungs are involved, the risk of death increases to the range of 50–70%.[8]
It is estimated that one million severe cases of leptospirosis in humans occur every year, causing about 58,900 deaths.
Signs and symptoms
The symptoms of leptospirosis usually appear one to two weeks after infection,[7] but the incubation period can be as long as a month.[21] The illness is biphasic in a majority of symptomatic cases. Symptoms of the first phase (acute or leptospiremic phase) last five to seven days. In the second phase (immune phase), the symptoms resolve as antibodies against the bacteria are produced.[8] Additional symptoms develop in the second phase.[22] The phases of illness may not be distinct, especially in patients with severe illness.[23] 90% of those infected experience mild symptoms while 10% experience severe leptospirosis.[24]
Leptospiral infection in humans causes a range of
There will be a resolution of symptoms for one to three days.[7] The immune phase starts after this and can last from four to 30 days and can be anything from brain to kidney complications.[25] The hallmark of the second phase is inflammation of the membranes covering the brain.[7] Signs and symptoms of meningitis include severe headache and neck stiffness.[7] Kidney involvement is associated with reduced or absent urine output.[7]
The classic form of severe leptospirosis, known as Weil's disease, is characterised by liver damage (causing jaundice),
Cause
Bacteria
Leptospirosis is caused by
A total of 66 species of Leptospira has been identified. Based on their genomic sequence, they are divided into two clades and four subclades: P1, P2, S1, and S2.[27] The 19 members of the P1 subclade include the 8 species that can cause severe disease in humans: L. alexanderi, L. borgpetersenii, L. interrogans, L. kirschneri, L. mayottensis, L. noguchii, L. santarosai, and L. weilii.[13][27] The P2 clade comprises 21 species that may cause mild disease in humans. The remaining 26 species comprise the S1 and S2 subclades, which include "saprophytes" known to consume decaying matter (saprotrophic nutrition).[27] Pathogenic Leptospira do not multiply in the environment. Leptospira require high humidity for survival but can remain alive in environments such as stagnant water or contaminated soil. The bacterium can be killed by temperatures of 50 °C (122 °F) and can be inactivated by 70% ethanol, 1% sodium hypochlorite, formaldehyde, detergents and acids.[28]
Leptospira are also classified based on their serovar. The diverse sugar composition of the lipopolysaccharide on the surface of the bacteria is responsible for the antigenic difference between serovars.[13] About 300 pathogenic serovars of Leptospira are recognised. Antigenically related serovars (belonging to the same serogroup) may belong to different species because of horizontal gene transfer of LPS biosynthetic genes between different species. Currently, the cross agglutination absorption test and DNA-DNA hybridisation are used to classify Leptospira species, but are time-consuming. Therefore, total genomic sequencing could potentially replace these two methods as the new gold standard of classifying Leptospira species.[13]
Transmission
The bacteria can be found in ponds, rivers, puddles, sewers, agricultural fields and moist soil.
The number of cases of leptospirosis is directly related to the amount of rainfall, making the disease seasonal in temperate climates and year-round in tropical climates.[7] The risk of contracting leptospirosis depends upon the risk of disease carriage in the community and the frequency of exposure.[21] In rural areas, farming and animal husbandry are the major risk factors for contracting leptospirosis.[5] Poor housing and inadequate sanitation also increase the risk of infection.[21] In tropical and semi-tropical areas, the disease often becomes widespread after heavy rains or after flooding.[7]
Leptospira are found mostly in mammals.
Humans are the
Rarely, leptospirosis can be transmitted through an organ transplant.[33] Infection through the placenta during pregnancy is also possible.[34][35][36] It can cause miscarriage and infection in infants.[37] Leptospirosis transmission through eating raw meat of wildlife animals have also been reported (e.g. psychiatric patients with allotriophagy).[38]
Pathogenesis
When animals ingest the bacteria, they circulate in the bloodstream, then lodge themselves into the kidneys through the
Humans are the
Through the
Leptospira LPS only activates
Although there are various mechanisms in the human body to fight against the bacteria, Leptospira is well adapted to such an inflammatory condition created by it. In the bloodstream, it can activate host plasminogen to become
Leptospira spreads rapidly to all organs through the bloodstream.
Diagnosis
Laboratory tests
For those who are infected, a
The kidneys are commonly involved in leptospirosis. Blood
For those with liver involvement,
For those with severe headache who show signs of meningitis, a lumbar puncture can be attempted. If infected, cerebrospinal fluid (CSF) examination shows lymphocytic predominance with a cell count of about 500/mm3, protein between 50 and 100 mg/ml and normal glucose levels. These findings are consistent with aseptic meningitis.[21]
Serological tests
Rapid detection of Leptospira can be done by quantifying the IgM antibodies using an enzyme-linked immunosorbent assay (ELISA). Typically, L. biflexa antigen is used to detect the IgM antibodies. This test can quickly determine the diagnosis and help in early treatment. However, the test specificity depends upon the type of antigen used and the presence of antibodies from previous infections. The presence of other diseases such as Epstein–Barr virus infection, viral hepatitis, and cytomegalovirus infection can cause false-positive results.[21] Other rapid screening tests have been developed such as dipsticks, latex and slide agglutination tests.[8]
The microscopic agglutination test (MAT) is the reference test for the diagnosis of leptospirosis.
Molecular tests
Leptospiral DNA can be amplified by using polymerase chain reaction (PCR) from serum, urine, aqueous humour, CSF, and autopsy specimens.[21] It detects the presence of bacteria faster than MAT during the first few days of infection without waiting for the appearance of antibodies.[25] As PCR detects the presence of leptospiral DNA in the blood it is useful even when the bacteria is killed by antibiotics.[39]
Imaging
In those who have lung involvement, a chest X-ray may demonstrate diffuse alveolar opacities.[21]
Diagnostic criteria
In 1982, the
Prevention
Rates of leptospirosis can be reduced by improving housing, infrastructure, and sanitation standards. Rodent abatement efforts and flood mitigation projects can also help to prevent it.[21] Proper use of personal protective equipment (PPE) by people who have a high risk of occupational exposure can prevent leptospirosis infections in most cases.[21]
There is no human vaccine suitable for worldwide use.
The prevention of leptospirosis from the environmental sources like contaminated waterways, soil, sewers, and agricultural fields, is disinfection used by
Treatment
Most leptospiral cases resolve spontaneously. Early initiation of antibiotics may prevent the progression to severe disease. Therefore, in resource-limited settings, antibiotics can be started once leptospirosis is suspected after history taking and examination.[21]
For mild leptospirosis, antibiotic recommendations such as doxycycline, azithromycin, ampicillin and amoxicillin were based solely on in vitro testing.[8] In 2001, the WHO recommended oral doxycycline (2 mg/kg up to 100 mg every 12 hours) for five to seven days for those with mild leptospirosis. Tetracycline, ampicillin, and amoxicillin can also be used in such cases.[43] However, in areas where both rickettsia and leptospirosis are endemic, azithromycin and doxycycline are the drugs of choice.[8] It should be noted doxycycline is not used in cases where the patient suffers from liver damage as it has been linked to hepatotoxicity.[44]
Based on a 1988 study,
Outpatients are given doxycycline or azithromycin. Doxycycline can shorten the duration of leptospirosis by two days, improve symptoms, and prevent the shedding of organisms in their urine. Azithromycin and amoxicillin are given to pregnant women and children.[21] Rarely, a Jarisch–Herxheimer reaction can develop in the first few hours after antibiotic administration.[8] However, according to a meta-analysis done in 2012, the benefit of antibiotics in the treatment of leptospirosis was unclear although the use of antibiotics may reduce the duration of illness by two to four days.[8][48] Another meta-analysis done in 2013 reached a similar conclusion.[8][49]
For those with severe leptospirosis, including potassium wasting with high kidney output dysfunction, intravenous hydration and potassium supplements can prevent dehydration and
Prognosis
The overall risk of death for leptospirosis is 5–10%.[10] For those with jaundice, the case fatality can increase up to 15%.[28] For those infected who present with confusion and neurological signs, there is a high risk of death.[21] Other factors that increase the risk of death include reduced urine output, age more than 36 years, and respiratory failure.[21] With proper care, most of those infected will recover completely. Those with acute kidney failure may develop persistent mild kidney impairment after they recover.[21] In those with severe lung involvement, the risk of death is 50–70%.[8] Thirty percent of people with acute leptospirosis complained of long-lasting symptoms characterised by weakness, muscle pain, and headaches.[21]
Eye complications
Eye problems can occur in 10% of those who recovered from leptospirosis
Epidemiology
It is estimated that one million severe cases of leptospirosis occur annually, with 58,900 deaths. Severe cases account for 5–15% of all leptospirosis cases.
The disease is observed persistently in parts of Asia, Oceania, the Caribbean, Latin America and Africa.[28] Antarctica is the only place not affected by leptospirosis.[28] In the United States, there were 100 to 150 leptospirosis cases annually.[54] In 1994, leptospirosis ceased to be a notifiable disease in the United States except in 36 states/territories where it is prevalent such as Hawaii, Texas, California, and Puerto Rico.[55] About 50% of the reported cases occurred in Puerto Rico. In January 2013, leptospirosis was reinstated as a nationally notifiable disease in the United States.[54] Research on epidemiology of leptospirosis in high-risk groups and risk factors is limited in India.[56]
The global rates of leptospirosis have been underestimated because most affected countries lack notification or notification is not mandatory.
History
The disease was first described by Adolf Weil in 1886 when he reported an "acute infectious disease with enlargement of spleen, jaundice, and nephritis."[18] Before Weil's description, the disease was known as "rice field jaundice" in ancient Chinese text, "autumn fever", "seven-day fever",[59] and "nanukayami fever"[60] in Japan; in Europe and Australia, the disease was associated with certain occupations and given names such as "cane-cutter's disease", "swine-herd's disease", and "Schlammfieber" (mud fever).[59] It has been known historically as "black jaundice",[61] or "dairy farm fever" in New Zealand.[62] Leptospirosis was postulated as the cause of an epidemic among Native Americans along the coast of what is now New England during 1616–1619. The disease was most likely brought to the New World by Europeans.[63]
Leptospira was first observed in 1907 in a
Leptospirosis was subsequently recognised as a disease of all mammalian species. In 1933, Dutch workers reported the isolation of Leptospira canicola which specifically infects dogs. In 1940, the strain that specifically infects cattle was first reported in Russia.
In 1982, there were about 200 serovars of Leptospira available for classification. The
Other animals
Infected animals can have no, mild, or severe symptoms;[19] the presenting symptoms may vary by the type of animal.[16][19] In some animals the bacteria live in the reproductive tract, leading to transmission during mating.[16]
Animals also present with similar clinical features when compared to humans. Clinical signs can appear in 5–15 days in dogs. The incubation period can be prolonged in cats. Leptospirosis can cause abortions after 2–12 weeks in cattle, and 1–4 weeks of infection in pigs. The illness tends to be milder in reservoir hosts. The most commonly affected organs are the kidneys, liver, and reproductive system, but other organs can be affected.
ELISA and microscopic agglutination tests are most commonly used to diagnose leptospirosis in animals. The bacteria can be detected in blood, urine, and milk or liver, kidney, or other tissue samples by using immunofluorescence or immunohistochemical or polymerase chain reaction techniques. Silver staining or immunogold silver staining is used to detect Leptospira in tissue sections. The organisms stain poorly with Gram stain. Dark-field microscopy can be used to detect Leptospira in body fluids, but it is neither sensitive nor specific in detecting the organism. A positive culture for leptospirosis is definitive, but the availability is limited, and culture results can take 13–26 weeks for a result, limiting its utility. Paired acute and convalescent samples are preferred for serological diagnosis of leptospirosis in animals. A positive serological sample from an aborted fetus is also diagnostic of leptospirosis.[28]
Various antibiotics such as doxycycline, penicillins, dihydrostreptomycin, and streptomycin have been used to treat leptospirosis in animals. Fluid therapy, blood transfusion, and respiratory support may be required in severe disease. For horses with ERU, the primary treatment is with anti-inflammatory drugs.[28][16]
Leptospirosis vaccines are available for animals such as pigs, dogs, cattle, sheep, and goats. Vaccines for cattle usually contain Leptospira serovar Hardjo and Pomona, for dogs, the vaccines usually contain serovar Icterohaemorrhagiae and Canicola. Vaccines containing multiple serovars do not work for cattle as well as vaccines containing a single serovar, yet the multivalent vaccines continue to be sold.[16] Isolation of infected animals and prophylactic antibiotics are also effective in preventing leptospirosis transmission between animals. Environmental control and sanitation also reduce transmission rates.[28][16]
References
This article was submitted to WikiJournal of Medicine for external academic peer review in 2019 (reviewer reports). The updated content was reintegrated into the Wikipedia page under a CC-BY-SA-3.0 license (2022). The version of record as reviewed is:
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External links
- "Leptospirosis". U.S. Disease Control and Prevention Center. 21 November 2018.
- "Leptospira". NCBI Taxonomy Browser. 171.