What is Leptospirosis?
Leptospirosis is a bacterial infection with worldwide distribution. It can affect most mammals (Bharti and others 2003) but some species seem more susceptible, such as the dog and the human. It is a spirochaete infection and the infecting organism was traditionally identified by serological testing, however modern methods using DNA hybridisation have been developed although many of these only allow identification to the species level (Jung and others 2015). The two most common serovars (L. canicola and L. icterohaemorrhagiae) have been the basis of leptospirosis vaccination in dogs for many years. There is now serological evidence of exposure to a much wider range of serovars including L. Grippotyphosa, L. Australis and L. Sejroe (Ellis 2010).
Why do we need to worry about Leptospirosis?
Leptospirosis is reported to be re-emerging disease worldwide (Goldstein 2010; Sykes et al. 2011; Harkin 2009; Hartskeerl et al. 2011) and human cases are reported to be increasing (Harkin 2009; Hartskeerl et al. 2011). In the UK, there were 10 cases of human infection reported in the second quarter of 2015. Four cases were reported after travelling (Public Health England, 2015). Infection in humans is typically acquired through recreational exposure (water sports, caving, kayaking, rafting, triathlons), occupational exposure (veterinarians, abbatoir workers, farm workers, hunters, scientists, shelter workers) or in endemic countries particularly associated with heavy rainfall and poor standard of living (Haake and Levett, 2015). Infection with Leptospires can cause life-threatening disease in humans with infected humans typically presenting with mild flu-like signs but they can develop severe disease which can include hepatic failure, kidney failure, haemorrhagic problems and potentially pulmonary haemorrhage syndrome (Haake and Levett, 2015).
Vaccination against L. canicola and L. icterohaemorrhagiae has been used since 1970 but the prevalence of clinical disease has been increasing since mid 1990s (Langston and Heute, 2003).
How do animals get infected?
Leptospires are spread by shedding of bacteria in the urine of maintenance or reservoir hosts who usually do not develop clinical signs. The bacteria can persist in renal tubules for a long time and thus contribute to ongoing environmental contamination. Cats can shed leptospires in urine and it is believed they may function as reservoir hosts (Fenimore et al. 2012; Rodríguez-Vidigal et al. 2014). Infection in incidental hosts can occur through direct contact with mucous membranes or damaged skin or more commonly indirectly via contact with soil or surface water which has been contaminated with urine from infected animals (such as rodents, foxes, hedgehogs or other dogs). Male dogs from rural environments with access to rivers or lakes and who work are at higher risk, however any dog can be affected, including those in suburban and urban environments (Goldstein 2010; Sykes et al. 2011; Greene et al. 2012).
The incidence of infection increases with higher rainfall or flooding (Goldstein 2010; Sykes et al. 2011; Greene et al. 2012; Raghavan et al. 2012) and then viable bacteria can persist for several months in moist soil or stagnant water (André-Fontaine 2006, Greene et al. 2012, Sykes et al. 2011).
When am I likely to see clinical cases?
There is an increase in cases in late summer and early Autumn in North America and in general increased rainfall is linked to an increased prevalence of leptospirosis (Prescott and other 2002, Ward 2002 and Ward and others 2004).
What happens once the leptospires get into the body?
Once the leptospires get into the body through damaged skin or intact mucosal membranes (including conjunctivae) they spread rapidly and can be found in the blood for up to 10 days after clinical signs start. After this period of leptospiraemia the organisms localise in protected tissue sites (liver, gravid uterus, spleen, central nervous system, eye) including the proximal renal tubules from where they can be shed for months (Dziezyc 2000, Langston and Heuter 2003, Levett 2001, Goldstein 2005, Greene and others 2006).
What are the typical clinical signs of leptospirosis?
There is a wide spectrum of clinical signs from subclinical disease, chronic disease to severe acute infection with multi-organ failure which can be terminal (Langston and Heuter 2003).
Clinical signs can affect a number of organ systems and include (Claus and others 2008, Dziezyc 2000, Greene and others 2006, Kohn and others 2010, Langston and Heuter 2003, Major and others 2014, Schweighauser and Francey 2008):
- Pyrexia
- Vomiting, diarrhoea, altered appetite, abdominal pain
- Shivering
- Muscle pain / weakness
- Dehydration, oliguria, anuria (sometimes polyuria/polydipsia)
- Shock, tachycardia, arrhythmias
- Lethargy
- Bleeding disorders
- Coughing, dyspnoea/tachypnoea (rhinitis, tonsillitis in some cases)
- Icterus, hepatic encephalopathy
- Conjunctivitis, scleral injection, uveitis (which can be delayed for many weeks to months)
Leptospires commonly infect kidneys and liver and the diagnosis should be considered in patients presenting with acute icterus, hepatic or kidney injury. Leptospires less commonly infect the lungs, spleen, endothelial cells, eye, muscle (heart and skeletal), meninges, pancreas and the genital tract. Therefore, leptospirosis should be considered as a differential diagnosis for patients with disease affecting any of these organ systems. Leptospiral pulmonary haemorrhage syndrome (LPHS) is an emerging severe form of the infection reported in humans and dogs. Kohn et al, 2010, reported 62% of dogs with leptospirosis had respiratory signs and 70% had abnormalities on thoracic radiographs. Leptospirosis should be considered even in vaccinated dogs.
How can leptospirosis be diagnosed?
Non-specific changes in the minimum database are common and identify organ involvement.
Reported haematological abnormalities include:
• Leukocytosis is typically seen, with occasional marked leukaemoid reactions, however leukopenia can be seen in the acute leptospiraemic phase
• Mild to severe thrombocytopenia is common
• Mild to moderate anaemia
Typical biochemical abnormalities in infected dogs reported by Kohn et al, 2010 include:
• Increased urea and creatinine 88-92%
• Increased ALT 78%
• Increased ALP 90-91%
• Increased bilirubin 73-83%
• Also reported: hypo and hyperkalaemia, hyperphosphataemia, hypoalbuminaemia
Urinalysis: isosthenuria, glucosuria, haematuria, pyuria, granular casts and proteinuria
Coagulation tests: variable results which can be suggestive of disseminated intravascular coagulation (DIC).
Thoracic radiographs can show typical features of leptospiral pulmonary haemorrhage syndrome (LPHS) such as caudo-dorsal interstitial infiltrate which progresses to reticulo-nodular and then alveolar infiltrates (Baumann & Flückiger 2001). Clinical signs of respiratory disease are not present in all dogs with radiographic changes (Kohn et al. 2010) and computed tomography may be more sensitive than radiographs (Gendron et al. 2014).
Abdominal ultrasonography can demonstrate changes in organs affected by leptospirosis such as hyperechoic renal cortices, renomegaly, pelvic dilation, medullary hyperechogenicity and peritoneal fluid development (Forrest et al. 1998). Other findings might reflect other organ involvement e.g. pancreatic hypoechogenicity, hepatomegaly, splenomegaly, lymphadenopathy and thickening of the gastric( and rarely intestinal) wall (Rentko and others 1992, Birnbaum and others 1998, Adin and Cowgill 2000, Mastrorilli and others 2007, Kohn and others 2010).
The changes described above are non-specific and may raise an index of suspicion for leptospirosis but the diagnosis can only be confirmed with specific testing.
Although culture of the organism can be considered gold-standard it is difficult and can take up to six months and therefore it is not appropriate for clinical practice. Dark-field microscopy needs to be performed on fresh urine samples and has poor sensitivity and specificity (Harkin and others 2003, Branger and others 2005).
Serological tests have been the most widely used confirmatory diagnostic test,in particular the microscopic agglutination test (MAT). MAT testing can be performed against a variety of different serovars and agglutination is assessed. MAT reactivity to a serovar is consistent to exposure to a serovar belonging to the serogroup tested but not necessarily to the servoar tested (Levett 2001) and it can reflect vaccination, acute or chronic infection and carrier status (Schuller and others 2015). Ideally the panel of serovars tested should be based upon knowledge of the relevant serovars in each geographical location, unfortunately this information is not available for all locations. Current recommendations are that serovar panels in Europe should include serogroups Australis, Autumnalis, Canicola, Grippotyphosia, Icterohaemorrhagiae, Pomona, Pyrogenes and Sejroe (Scanziana and others 2002, André-Fontaine 2006, Giesen and others 2007, Ellis 2010). False negative results can be obtained if the infecting serovar is not included in the panel (Sykes and others 2011; Greene and others 2012). The MAT can also be negative in acute infection and therefore the recommendation is that paired samples are collected one to two weeks apart to try and confirm infection with a recent study demonstrating this was necessary to make the diagnosis in 45% of cases (Tangemen and Littman 2013). The criteria widely accepted are a titre of >1:800 for one or more serogroups or a fourfold (two-titre steps) increase in MAT on paired samples (Schuller and others 2015). Patient-side tests to detect anti-leptospiral IgM and/or IgG are becoming more widely available but they have similar limitations to MAT testing and it is recommended that the tests be confirmed by MAT testing (Abdoel and other 2011, Schuller and others 2015).
PCR tests have been developed which are specific for detection of pathogenic Leptospira spp. DNA and can be used in a variety of samples including blood, urine and tissue biopsies. Leptospires are found in the blood during the first 10 days of infection depending on the infecting strain and the host response (Greenlee and others 2010) and subsequently the organisms will be found in urine. The recommendations of the European Consensus panel was that PCR should be performed on both blood (EDTA and Heparin tubes) and urine (plain tube), before administration of antibiotics in patients suspected to have leptospirosis regardless of the duration of clinical signs. These samples should be tested separately and not pooled and the sample requirements of the laboratory the samples are being submitted to should be followed. Urine PCR is the test of choice for detection of renal carriers (Harkin and others 2003; Rojas and others 2010; LLewellyn and others 2013)
Commercial PCR tests for leptospirosis do not currently provide information on the infecting serovar nor the infectious load. The current recommendations are that PCR and MAT testing are used in conjunction whilst further research is performed on the sensitivity and specificity of PCR testing (Schuller and others 2015). Vaccination does not result in positive PCR results (Midence and other 2012).
How is leptospirosis treated?
Antibiotics are the mainstay of treatment combined with supportive care directed at the organ systems affected and complemented by high standards of general nursing care. There is controversy in human patients about the need for antibiotic treatment (Gulati and Gulati 2012; Guidugli and others 2000; Brett-Major and Coldren 2012) however the World Health Organisation currently recommends antibiotic treatment even in early cases (WHO 2003) as does the European consensus statement on leptospirosis in dogs and cat (Schuller and others 2015).
Treatment schedule recommended is:
• Doxycycline at 5mg/kg q 12hr or 10mg/kg q 24hrs for 14 days
• Intravenous penicillin derivative can be used initially in patients with gastrointestinal signs e.g. ampicillin at 20-30mg/kg q 6-8hr or 20-30mg/kg amoxicillin q 6-8hr or penicillin at 25000-40000u/kg q 6-8hr
o Dose adjustment is recommended in dogs with acute kidney injury e.g. double dosing interval
o Dogs must receive a full 14-day course of oral doxycycline to eliminate renal colonization after the penicillin course as whilst penicillin is effective in resolving clinical signs it is unreliable for eliminating organisms from the kidneys and will not prevent development of a chronic renal carrier state (Sykes and others 2011; Greene and others 2012).Resistance of leptospires appears rare however urinary shedding of live organisms can persist for months in chronic renal carriers, so preventing this is essential.
It is recommended to treat all in-contact dogs with doxycycline at the doses above for 2 weeks but treatment of in-contact cats is currently not recommended.
Supportive treatment is beyond the scope of this article and for more specific treatment advice the practitioner should refer to recent review articles or textbooks for the specific organ failures present in each case. There is some suggestion that glucocorticoids may reduce mortality in humans with LPHS but this requires further evaluation in dogs (Shenoy and others 2006).
How do we know if treatment was successful?
Dogs presenting with kidney injury associated with leptospirosis can take months for recovery to happen and in approximately 50% of dogs impairment persists for more than one year (Kis and others 2012)and therefore long term monitoring of renal function is recommended. The European Consensus recommends reassessment one week, one month, three months and six months after discharge from the hospital (Schuller and others 2015).
Urinary PCR may be useful following treatment to ensure that the organisms have been eliminated from the kidneys, however a positive result could represent dead leptospires following antibiotic treatment and is not always correlated with viable organisms (Sykes and others 2011). Leptospires are shed intermittently and therefore false-negative results may occur (Greene and others 2012). However, PCR is currently the best test available for urinary shedding (Greene and others 2012; Sykes and others 2011) but there are currently no recommendations from the consensus panels for urine screening during follow up (Sykes and other 2011, Schuller and others 2015).
How can we prevent infection?
Vaccination is the most logical way to try and control infection and reduce the prevalence of clinical disease and carrier status. Bivalent vaccines containing the serovars Icterohaemorrhagiae and Canicola have been in widespread use for many years and infection with these serovars is now rare based upon MAT testing. Leptospirosis has been reported in European dogs vaccinated with bivalent vaccines (Kohn and others 2010). Quadrivalent leptospirosis vaccines (Canicola, Icterohaemorrhagiae, Pomona and Grippotyphosa) were introduced in the USA in 2001 and are now available in Europe. The current European vaccines contain either three serovars (Canicola, Icterohaemorrhagiae, and Grippotyphosa) or four serovars (Canicola, Icterohaemorrhagiae, Grippotyphosa and Bratislava). The European consensus statement recommends the use of quadrivalent vaccines (Schuller and others 2015)and the schedule is summarised in the key points below with annual revaccination. Vaccination is recommended as soon as clinical recovery is seen (Schuller and others 2015). There have been concerns raised about reactions to quadrivalent vaccines but one study has not shown vaccines with leptospiral antigen to be more associated with reactions than other vaccines (Moore and others 2005), however veterinarians should report any suspected adverse drug reactions to the authorities.
In addition, veterinarians should educate owners about trying to reduce re-infection and by reducing access to potential sources of infection including external water sources and wildlife carriers. Leptospirosis is a zoonotic infection and owners should be advised to practice good hand hygiene after normal handling, to wear gloves when clearing up urine and to use routine household disinfectants to inactivate urine e.g. 10% bleach. The time for urine to be clear of leptospires is variable (Juvet and others. 2011) and currently there are no strict timelines to advise owners. Precautions should also be employed in veterinary practices as described by Schuller et al, 2015 including clear identification of infected patients, minimal movement in the hospital, barrier nursing, management of contaminated waster and reducing exposure of susceptible people.
Can cats get leptospirosis?
Cats can be infected with leptospires but infection is not always associated with clinical signs (Fessler and Morter 1964, Luciani 2004, Arbour and others 2012). The author has recently presented three cats with suspected clinical leptospirosis and would encourage veterinarians to consider testing in cats with acute and chronic kidney disease (Rodriguez and other 2014) and liver disease (Murphy and others 2016)
Key Points
European consensus statement (Schuller and others 2015)on leptospirosis in dogs and cats key recommendations include
• Leptospirosis should be considered a possible diagnosis regardless of the patients signalment
• Paired MAT titres are recommended and should be interpreted in conjunction with vaccination history
• PCR testing of blood and urine before antibiotics is recommended in dogs with clinical suspicion of leptospirosis regardless of duration of clinical signs
• PCR should be interpreted in conjunction with MAT results and the clinical context
• Antibiotics are recommended in dogs suspected to have leptospirosis even before a diagnosis is confirmed
o Doxycycline 5mg/kg q 12hr or 10mg/kg q 24hrs for 14 days
o IV Penicillin based drug (see above for doses) if gastrointestinal signs initially followed by 2 weeks of doxycycline
• Use of renal replacement therapy should be considered for severe renal leptospirosis
• In contact dogs should be treated with the same schedule of doxycycline as infected dogs with no current indication to treat in-contact cats
• Dogs should be re-examined (clinical assessment, blood pressure, blood analysis) at
o < 1week after discharge
o q 1-3 weeks until stable
o q 1, 3 and 6 months
• Use of quadrivalent vaccines is recommended to increase the spectrum of protection
o Basic vaccination with 2 injections following manufacturers schedule followed by annual re-vaccination for all at risk dogs regardless of breed
o Re-start any vaccination schedule which is > 18months since vaccination with 2 injections as above
Conclusion
Leptospirosis is an important disease and because of its multisystemic nature should be considered as a differential in patients with consistent clinical signs. Early diagnosis and treatment can result in favourable outcome. Vaccination is recommended to try and reduce clinical disease.
References
Abdoel 2011
Adin and Cowgill 2000
Andre Fontaine 2006
Bharti, A.R. et al., 2003. Leptospirosis: a zoonotic disease of global importance. The Lancet. Infectious diseases, 3(12), pp.757–71.
Baumann and flucktiger
Birnbaum 1998
Branger 2005
Brett Major
Coldren
Dziezyc 2000
Ellis 2010
Forrest 1998
Giesen 2007
Giudligi
Goldstein 2005
Goldstein 2010
Greene 2006
Greene 2012
Greenlee 2010
Gulati
Haake, D. A., & Levett, P. N. (2015). Leptospirosis in Humans. Current Topics in Microbiology and Immunology, 387, 65–97. http://doi.org/10.1007/978-3-662-45059-8_5
Harkin 2003
Harkin 2009
Hartskeerl 2011
Langston and Heuter 2003
Levett 2001
Llewellyn 2013
Jung Lenice Roteia Cardoso, Bomfim Maria Rosa Quaresma, Kroon Erna Geessien, Nunes Álvaro Cantini. Identification of Leptospira serovars by RFLP of the RNA polymerase beta subunit gene (rpoB). Braz. J. Microbiol. [Internet]. 2015 June [cited 2016 Oct 25] ; 46( 2 ): 465-476. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1517-83822015000200465&lng=en. http://dx.doi.org/10.1590/S1517-838246220120018.
Kohn 2010
Mastrorilli 2007
Midence and others 2012
Moore guptill 2005
Prescott and others 2002
Rentko 1992
Rojas 2010
Scanziani 2002
Shenoy
Sykes 2011
van de Maele I., Claus A., Haesebrouck F., Daminet S. Leptospirosis in dogs: a review with emphasis on clinical aspects Veterinary Record 2008;163:14 409-413 doi:10.1136/vr.163.14.409
Tangeman and Littman 2013
Ward 2002
Ward and others 2004
Public Health England Health Protection Report Vol 9 No 28 – 14 August 2015 https://www.gov.uk/government/uploads/system/uploads/attachment…/hpr2815.pdf