Acute leptospirosis, caused by the pathogenic Gram-negative spirochaete Leptospira interrogans, is rarely seen in the UK. However, because of this it is easily missed and may have serious consequences for both the individual and for public health.
Concerns have been raised that its incidence may be increasing, perhaps as a consequence of global climate change.
Exposure to the urine of animal hosts puts humans at risk of leptospirosis, often through contaminated fresh water or soil. Sewage workers and those taking part in water sports are particularly vulnerable. Human to human transmission is rare.
The bacteria L interrogans are robust, living for years in their animal hosts who then excrete the bacteria. It is also able to survive in the external environment for many weeks.
Animal hosts include rats, dogs, squirrels, pigs, cows and exotic pets.
The bacteria, which are coil-shaped, are able to spin and burrow into damaged tissue rather than unbroken skin. As well as through skin, aerosolised bacteria or bacteria in water may also enter through mucous membranes, conjunctiva, lungs or even the placenta.
Signs and symptoms
While, in some cases, the incubation period may be as long as a month, most texts suggest around one to two weeks. Signs and symptoms of the condition vary greatly and clinical suspicion is often raised by a careful history taking.
In many cases, leptospirosis is diagnosed by chance. Mild anicteric disease may present with flu-like symptoms or may even be asymptomatic.
'Weil's disease' is a term reserved for icteric leptospirosis, which tends to be severe and can lead to multi-organ vasculitis, organ failure and even death.
In both symptomatic mild and severe manifestations, the patient initially presents with non-specific symptoms suggestive of infection.
These include fever (38-40 degsC), rigors, dry cough, pharyngitis, diarrhoea and vomiting, severe headache, conjunctival injection, meningism, muscle pains, purpuric rash and tachycardia.
Other features may include hypotension, orchitis and cholecystitis. Depending on the serovar and patient factors including age, nutritional status and comorbidities, patients will either recover, or, after one or two days of apparent recovery, go on to develop icteric leptospirosis.
Icteric disease is associated with hepatocellular destruction and liver failure. Nephritis may be complicated by renal failure.
Pulmonary oedema and haemorrhage causes respiratory failure and is a common cause of death in Weil's disease.
Leptospirosis induced myocarditis may cause ventricular dysfunction and arrhythmias. Disseminated intravascular coagulation, haemolytic uraemic syndrome, thrombotic thrombocytopenic purpura are all possible complications in leptospirosis.
Laboratory tests are usually required to confirm a diagnosis of Weil's disease and to evaluate its severity as the clinical picture alone is not specific enough.
Important blood tests include FBC, electrolytes, renal and liver function, clotting studies and paired samples for leptospirosis serology.
Urine should be examined for spirochaetes although the urine is only positive in the first few weeks of infection.
Cerebrospinal fluid, blood and tissue biopsy may also be studied although negative results do not rule out leptospirosis. Pulmonary imaging and function tests, ECG, echocardiography and abdominal ultrasounds are also required.
Treatment of anicteric infection, sometimes referred to as uniphase infection, is usually symptomatic although antibiotics may be used. Icteric disease usually requires active treatment to reduce the risk of multi-organ failure and death.
In addition to supportive treatment and close monitoring of cardiac, pulmonary, liver and renal function, early use of antibiotics is imperative. Penicillin, erythromycin for those allergic to penicillin, or doxycycline are the drugs of choice. Third generation cephalosporins may also be used.
Supportive treatment includes careful fluid and electrolyte management, positive inotropes, ventilation and renal dialysis if there is severe acute tubular insult.
Some patients may suffer from acute confusion or even psychosis in which case sedation may be required. Depression and fatigue may be a long-term psychological sequaelae of leptospirosis.
- Dr Thakkar is a GP in Wooburn Green, Buckinghamshire
1. Leptospirosis information centre. www.leptospirosis.org/
2. Leptospirosis in humans. http://emedicine.medscape.com/article/788751-overview
3. Leptospirosis and Weil's disease. http://www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/ 1195733804526