SRI LANKA: Rise in rat fever among farmers causes concern

Photo: Christine Jayasinghe/IRIN

These fishermen-turned-farmers standing knee-deep in an irrigation pond in Kattakaduwa in northwestern Sri Lanka are vulnerable to the potentially fatal leptospirosis bacteria

COLOMBO, 18 December 2008 (IRIN) - Health authorities in Sri Lanka are concerned about a spike in the number of reported cases of Leptospirosis, known as rat fever, among farmers and are redoubling efforts to halt the spread of the potentially fatal disease.

Rice farmers, usually males between the age of 20 and 60, are the most vulnerable and are being provided with a free prophylactic antibiotic by the government. They are also being advised on basic precautions against contracting the infection.

Almost 7,000 cases of Leptospirosis, 83 percent of them men, have been reported this year, against 2,198 in 2007, according to statistics maintained by the Health Ministry's Epidemiology Unit. About 200 people have died of rat fever this year.

"Leptospirosis is a seasonal, occupation-related disease mainly associated with agricultural activities," said Sudath Samaraweera, consultant community physician at the Epidemiological Unit. "The risk of exposure to the bacteria goes up usually after the rainy season because the contaminated areas are widened."

The bacterium is found in the kidneys of rats, dogs and cattle and is excreted in urine. Anyone who is exposed to water contaminated with the infected urine can contract the disease if they have an open wound or skin abrasion, or they drink the water. The disease is characterised by high fever, headaches and muscle pain. If left untreated, it can lead to death.

The disease runs in roughly a five-year cycle with a peak number of infections experienced this year. Even for a peak year, however, this year's increase is unprecedented and unexpected.

"We think one reason for the sharp increase is the large number of people who are now engaging in agriculture," said Samaraweera, adding that the high rainfall this year and the changing virulence of the organism may also have contributed to the current outbreak.

In a bid to increase national food production, many abandoned rice fields are being rehabilitated by the government and former farmers, who had found other ways of earning a living, are being encouraged to return to their fields. That ties in with the predominant number of males who contract the disease as women tend to be employed in the fields only at harvest time.

Significantly, the highest number of reported cases of rat fever is in the capital Colombo and Gampaha and Kalutara Districts, all mainly urban areas in the Western Province. Samaraweera pointed out that it was in these areas that farming was being revived with former unfarmed fields being sown with rice again.

However, farmers need not be discouraged, he stressed. "They need not be afraid of engaging in cultivation. If they adhere to precautionary measures such as covering wounds before going to [rice] paddy fields, not using canal water to wash their mouth or to drink, and also get prophylactic medicine from the Public Health Inspector in the area, the risk is very low," said Samaraweera. "If they get sudden onset high fever, it is advisable to go to the local hospital for treatment. Effective treatments are available and complete recovery is possible if commenced early."

Researchers have found that first-time cultivators had a low level of natural immunity to the disease. Often, they also neglected to observe traditional practices for controlling rodents such as using glyricidia flowers and coconut palms, which act as rat repellents, in the fields. Traditional farmers encourage predators, such as owls, by planting the stalks of coconut palm fronds around the fields for the birds to perch on, a practice not always followed now.

Health education

The government's two-pronged strategy for educating farmers about disease prevention involves both health and agricultural out-reach officers.

Health officers are giving the antibiotic doxycycline to those at high risk of contracting the disease, while agricultural advisers encourage better environmental management, including using established methods of controlling the rat population.

They also encourage synchronised farming so that all fields in a particular area are cultivated at the same time. This tactic is aimed at limiting the amount of food available for rats, which would otherwise multiply rapidly if food was available for an extended period.

cj/bj/mw