Beware of the Rat

A common and potentially severe infectious disease caused by Leptospira bacterium and transmitted through the urine of an infected animal, it is considered a re-emerging disease with Laos, Thailand and Vietnam the most affected countries, reporting more than 10 cases per 100,000 people annually. 

The pathogen infects many domestic and wild animals (rodents in particular) in addition to humans. Infected animals release the bacteria through urine, which contaminates the water and humid surroundings. With countless fresh markets and food stalls spread over the city streets, rats are the main reservoir and vector of the illness and the prime culprits in expatriate infestation in urban areas. In Thailand, the disease is called rokh chi nu, which translates as illness from rat urine.

People living in urban slums are heavily exposed to leptospirosis especially during the rainy season. People in occupations with significant exposure to animals are at higher risk of the disease, namely farmers, slaughterhouse workers, rice field workers as well as sewage workers.

Expats or travellers in the Asian region need to be aware of the leptospirosis risk especially if they are involved in the farming or livestock industry or in humanitarian assistance to slum dwellers. Also at risk are those who enjoy such outdoor water sports as adventure triathlon, rafting, fresh water fishing, cable wakeboarding and swimming in rivers or ponds.

Predominantly a water-borne disease, the germs enter the body through minor skin lesions or the mucosa of the eye or nose as well as through the ingestion of contaminated water.

The first symptoms usually occur 1 to 2 weeks after the contamination. In about 60 per cent of the cases, the infection is unnoticed. For the remaining 40 per cent, the symptoms vary from mild, influenza-like illness to a severe infection with fever, headache, weakness, chills, muscles pain, vomiting, diarrhoea and stomach pain that can be mistaken for other tropical diseases such as dengue, malaria and Japanese encephalitis. 

In about 10 per cent of symptomatic cases, severe forms of leptospirosis occur leading to multiple organ damage. The clinical picture typically progresses in two phases. The first is an initial, acute flu-like syndrome from which the patient apparently starts to recover. The second occurs after a couple of days, with the patient becoming seriously ill again and presenting alarming manifestations, which may result in liver failure (liver enlargement, spontaneous bleeding and jaundice (yellowing of the skin and the whites of the eyes), kidney failure (reduced urination, swollen legs and feet, flank pain), heart failure (abnormal heart beats, congested lungs, weakness and dizziness) or in a brain infection (with vomiting, stiffness of the neck and disorientation). 

The bacteria can also invade the lungs and trigger a rapid life-threatening pulmonary haemorrhage. 

Treated after too long a delay or poorly managed, severe leptospirosis leads to permanent organ damage or death in 5 to 20 per cent of the cases. 

Any suspicion of leptosporosis requires rapid hospital transfer to carry out lab tests. Treatment is immediately initiated even before the lab results are back to prevent potential complications. Minor cases are treated with oral antibiotics while severe forms receive high-dose intravenous penicillin in addition to intensive support care that may include haemodialysis to deal with kidney impairment.

A few vaccines exist in some countries but are only effective on the specific local strain of Leptospira bacterium and are thus useless in other areas where the pathogen strain is different. In practice, only at-risk professionals are concerned by the vaccination.

Other preventive measures include the reduction in rat populations though this is nigh impossible in many agglomerations. As with any water-borne infection strict hygiene is primordial. Children should not walk barefoot in potentially infested puddles within the neighbourhood. People with significant recreational exposure must avoid as much as possible contact with contaminated water and remain aware of the early manifestations of the illness. 

 

DR GERARD LALANDE is managing director of CEO-Health, which provides medical referrals for expatriates and customised executive medical check-ups in Thailand. He can be contacted at [email protected]