Deadly risk of rat fever | Daily News


Deadly risk of rat fever

Rat fever (leptospirosis) is an infectious disease caused by pathogenic bacteria called leptospira, which are maintained in the kidneys of certain animals such as rats, pigs, cattle, rodents, canines, wild mammals and livestock. These organisms are transmitted directly or indirectly from animals to humans, consultant epidemiologists attached to the Epidemiology Unit of the Health, Nutrition and Indigenous Medicine Ministry said.

Some animal species have a commensal relationship with certain types of leptospira (serovars) i.e. they are natural hosts for those serovars. These animals continuously excrete leptospira with urine, though they do not suffer from the disease. If other animals including humans are infected by the same serovars, they often become ill. If a natural host for a particular serovar is infected with another serovar, it may also develop the disease. Serovars found in rats and bandicoots are often identified as the cause for serious illness in humans.

Humans are incidental or accidental hosts of the bacteria. Exposure through water, soil, or foods contaminated by urine of affected animals is the most common route. A leptospire-contaminated environment caused by, for example, local agricultural practices (paddy cultivation) and poor housing and waste disposal gives rise to many sources of infection.

“Leptospira enter the body through abraded or traumatised (injured) skin or nasal, oral, or eye mucous membranes. Ingestion of contaminated water can also lead to infection. After infection, they enter the blood and invade practically all tissues and organs,” they said.

The diagnosis of leptospirosis should be considered in any patient presenting with an abrupt onset of fever, chills, conjunctival suffusion, headache, muscle tenderness (notable in the calf and lumbar areas) and jaundice. The case fatality rate is reported to range from less than five percent to 30 percent, and important causes of death include renal failure, heart failure and widespread haemorrhage.

Liver failure is rare despite the presence of jaundice.

Knowledge of local epidemiology and varied clinical presentation, and high index of suspicion are essential to make a diagnosis. Suspicion should be further increased if there is a history of occupational or recreational exposure. Confirmatory diagnosis is mainly performed by detecting antibodies (e.g., MAT).

However, simple investigations such as full urine report (albumin+) and the differential count of white blood cells (polymorpholeucocytosis) would help clinicians to make a probable diagnosis and also to decide on the need for admission to hospital.

For epidemiological and public health reasons also, laboratory support is important. Identifying serovars (serotyping) is costly, time consuming and the results are not likely to affect treatment of an individual patient. However, the resulting information is useful in investigating its source or potential reservoir, and planning and evaluating interventions.



Leptospirosis is a potentially serious but treatable disease. Treatment with effective antibiotics should be initiated as soon as the disease is suspected. Clinicians should never wait for the results of laboratory tests before starting treatment with antibiotics because serological tests do not become positive until about a week after the onset of illness, and the culture may not become positive for several weeks. Supportive care with strict attention to fluid and electrolyte balance is essential. Dialysis is indicated in renal failure. Heart failure can occur if medical treatment is not given on time.

Serovar-specific antibodies produced following infection are protective and a patient is immune to re-infection with the same serovar as long as the specific antibody titre is high enough. However, it will not protect against infection with other serovars. The bacteria live in the environment over a period of one month.

Preventive measures must be based on knowledge of high-risk groups and local epidemiological factors. It is important to raise awareness about the disease among the risk groups, healthcare providers and the general population, so that the disease can be recognised early and treated as soon as possible. If you are involved in occupations such as farming, mining, or cleaning drains and canals, please inform your area MOH or PHI. They will explain the specific measures that can be taken to prevent contracting leptospirosis.


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