Rat Fever deadly but preventable | Daily News

Rat Fever deadly but preventable

Rat Fever (Leptospirosis) is an infectious disease caused by pathogenic bacteria called lepto spires, which are maintained in nature in the kidneys of certain animals such as rats, pigs, cattle, rodents, canines and wild mammals, livestock, canines and wild mammals. 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.

According to the Consultant Epidemiologists, some animal species have a commensal relationship with certain types of leptospires (serovars) i.e. natural hosts for those serovars. These animals continuously excrete leptospires in 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.

Man is an incidental or accidental host. Exposure through water, soil, or foods contaminated by urine of affected animals is the most common route. Leptospire-contaminated environment caused by, for example, local agricultural practices (paddy cultivation) and poor housing and waste disposal give rise to many sources of infection. Leptospires enter the body through abraded or traumatized (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.

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 calf and lumbar areas) and jaundice. Case fatality rate is reported to range from less than 5 percent to 30 percent and important causes of death include renal failure, heart failure and widespread hemorrhage. 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. Confimatory diagnosis is mainly by detecting antibodies (e.g. MAT). However, simple investigations like urine full report (albumin +) and white blood cells/ differential count (polymorpholeucocytosis) would help the clinicians to make a probable diagnosis and also to decide on the need for hospital admission. 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/ 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 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 etc. can occur if medical treatment 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 the high risk groups and the local epidemiological factors.

It is very important to raise awareness about the disease among the risk groups, health care providers and general population, so that the disease can be recognized early and treated as soon as possible.

If you are involved in occupations such as farming, mining, cleaning drains and canals etc. please inform your area MOH or PHI. They will explain how to avoid getting the disease. There are specific measures that help to prevent leptospirosis.


Rat Fever cases

A total of 1844 Rat Fever cases had been reported from all parts of the country during this year. The highest number of cases, 436, had been reported from the Ratnapura district while the second highest number of cases, 200 had been reported from the Galle district. Kalutara district recorded a total of 174 cases of Rat Fever while Badulla district recorded 131 cases during the same period. The highest number of Rat Fever cases in this year, 665 was reported in January and the second highest number, 452 reported in February.


Symptoms normally appear within 5 to 14 days following exposure to the germ. The range is between 2 to 30 days. Leptospirosis may present with a wide variety of clinical manifestations. These may range from a mild flu-like illness to a serious and sometimes fatal disease. It may also mimic many other diseases such as dengue fever, influenza, meningitis, and hepatitis. Jaundice is a relatively common symptom in Leptospirosis but is also found in many other diseases involving the liver. The main and common symptoms of Rat Fever are abrupt onset of high fever, mild flu, chills, conjunctival suffusion, muscle tenderness (notable in calf and lumber areas), intense headache, jaundice area and decrease of passing urine.

Sri Lankan context

In Sri Lanka, leptospirosis is reported throughout the year. High humidity and heavy rainfall intensify outbreaks because of widespread contamination by rodent urine in flood water (Rodents are displaced from their burrows and drains by the flood water). Annually there are two peaks in the disease incidence, at the time of the monsoons, a smaller one during March - May and a larger one during October - December. This seasonal variability should be taken into consideration while planning prevention and control activities. Vulnerable people are farmers, persons who clean drains, persons who work in mines, marsh lands, canals and persons who swim or play in contaminated water.


* Removal of rubbish and keeping areas around human habitation clean to control rodents. Wild rats living in open environment are more dangerous than the domestic rats.

* Keep animals away from gardens, playgrounds, sandboxes, and other places where children play

* Where appropriate, protective clothing, knee-high boots, gloves etc. should be worn and wounds covered with waterproof dressing

* Use boiled water (chlorination is seldom useful, as virulent organisms withstand up to 4 ppm; filtered water is also not safe)

* Avoid walking in flood water

* Doxycycline has been reported to give some protection against infection and disease. All vulnerable people in high risk categories should contact the nearest PHI or MOH office and obtain Doxycycline tablets (free of charge) and they should take two tablets before they start their work. They should drink plenty of water while working. The tablets give around 90 percent protection for a period of one week. Then they should take two tablets again until they finish their work.

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