Leptospirosis, still a menace

Cases of leptospirosis are seen throughout the year, but an outbreak is possible during the rainy season when rodents are displaced in large numbers, says DR. S. RATNAM.

THE rainy season has started - a period when one must be careful about leptospirosis. There have been a number of articles on the disease in leading dailies, but these have focussed on theoretical knowledge. I would like to share my practical experiences with the disease.

Earlier, leptospirosis was identified as a rare disease. In 1980, 25 cases were identified by me through serology and isolations of the causative leptospires between October and December (the rainy season) at the Stanley and Government General Hospitals, Chennai.

Delayed awareness?

Earlier, there were shortcomings in diagnosis, hence a lack of awareness. Second, this disease was overlooked as it mimics other diseases like influenza, dengue, typhoid and other enteric manifestations, malaria, viral jaundice and renal disease in their clinical presentation. Respiratory and cardiac arrest are also contributory of leptospirosis. Third, the virulence of the infecting serovar and the immune status of the population determines the gradations of clinical expressions which range from fever to severe hepatorenal failure and death.

Leptospirosis in India

In 1905, Chowdry presented 585 cases of the disease in the Andaman islands, calling it "malaria with jaundice". Thereafter, reports were published occassionally from the Andamans, Calcutta, Bombay, Delhi and Chennai. But after 1980 there were continuous reports on clinical and epidemological aspects of leptospirosis in scientific journals and the mass media from Chennai city, which spread awareness about this disease. In the Andamans, this disease was also called as "Andaman haemorrhagic fever" with a predominance of haemorrhagic signs. In Kerala, it was the same type as seen in the Andamans. In Chennai city, the most severe form was jaundice and a haemorrhagic type. Of late, eye disorders as late complications of leptospirosis have been recorded in Madurai. Cardiac arrhythmias in Mysore are the latest reports on the manifestations of the disease.

Clinical signs vary from case to case. Most common symptoms are fever, muscular pain, headache, gastrointestinal disturbances, jaundice, haemorrhagic signs, renal, respiratory and cardiac signs - in descending order. Experimental studies have been carried out to understand the intensity of damage caused on different organs of laboratory animals.

When this disease occurs

Cases are seen sporadically throughout the year. But an outbreak occurs during the rainy season because of widespread contamination by infected rodent urine in flood water. Rodents are displaced from their burrows and drains by the water. High humidity and heavy rainfall intensify the outbreak.

Diagnosis

In the early stages of infection, demonstration of leptospires in the bloodstream is a reliable index. Detection is always based on the concentration of organisms in the blood. In a mild and influenza type of illness, only a few organisms are seen in the bloodsteam which leads to a false and negative result. It also necessitates at least 100 fields of search through dark field examination per sample. Here too, the fibrin and extrusions of red blood corpuscles simulate leptospires and lead to false positive reults. The Browninan movement of pseudospirochaetes can confuse even the most experienced scientist. Naturally this may lead to a false boosting of a positive result. This happens in most laboratories. A dark field examination as a sole test for confirmation is not to be relied on. Unfortunately, most laboratories do only this test.

Isolation of leptospires is the only authentic method of confirmation but these are delegate organisms. Hence the isolation rate is poor. Isolation is also time consuming. The demonstrable level antibody can be seen four to six days after the appearance of the first clinical sign, at a low level. Demonstration of a rise in antibody levels either through MAT or ELISA is essential by repeating the sampling at least four days after taking the first sample. These tests are seldom useful for clinicians to execute prompt therapy, since most antibiotics are effective only if given within four days of illness. In Chennai, the MAT test is available at the Veterinary University, Madhvaram, the MGR Medical University, Guindy and the microbiology department of the Madras Medical College.

The IgM dip stick ELISA is commercially available from Organon Teknika (Infar India) and Pan Bio (Australia). Using this test could help detect leptospirosis during the acute (early) phase of the illness.

Prevention

Prevention of leptospiral infection is difficult though theoritically advisable. Leptospires can adapt many hosts either as a carrier or reservoir. It also survives in a moist environment for a considerable period of time. Further, there are more then 240 leptospiral serovars available.

Rodent control is relatively difficult. Rats and bandicoots distribute more virulent leptospires through their urine into the environment than other animals. Hence more severe cases are seen in the metropolitan cities.

Chlorination is seldom useful, as virulent leptospires withstand up to 4 ppm in potable water. Filtered water is not safe. Using boiled or ultraviolet irradiated water is advisable. Water tanks must be sealed if possible. Food articles must be stored in properly fitting containers. Bathroom and kitchen waste pipes must be blocked at night.

Floods flush out rodents from the drainage system and the water gets polluted with the urine. Each millilitre of urine contains several millions of organisms. Exposure causes leptospires to enter abraded skin or an intact mucous membrane. Try avoiding walking in flood water. If you have to, wear gum boots. Any illness subsequent to exposure to such an environment must be viewed to suspect leptospirosis and prompt antibiotic therapy (Doxycycline) taken. Personal hygiene is important. Heavy drinking and smoking predispose damage to the liver and the kidneys which in turn become vulnerable to leptospiral infection.

Take care this monsoon.

The writer is with the Radioisotope Laboratory, Madras Veterinary College, Chennai - 600 007.

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