ศาสตร์เกษตรดินปุ๋ย : ขอบคุณแหล่งข้อมูล : หนังสือพิมพ์ The Nation
Often unrecognised and thus left untreated, Lyme disease is one of the most common tick-transmitted illnesses and is currently on the rise, especially in the northern parts of the USA, Europe, north Asia and the Far East.
Lyme disease is caused by various species of the Borrelia bacteria that infect mammals and birds. The pathogen is transmitted to humans during a painless bite of an infected tick of the Ixodes genus and usually occurs after a quite long period of attachment (more than 24 hours) of the insect to the skin. Following a tick bite, the risk of Borrelia infection is however quite low, between one and five per cent and most ticks are fortunately detected and removed before 24 hours of attachment.
Infestation happens in places where ticks are present such as grassy and wooded areas with high humidity levels. Those exposed to forestry activities or who engage in outdoor sports in such locations are at higher risk of contracting the disease. Ticks can also transmit other microbes that induce disease in humans.
Symptoms occur after a few days or weeks after the bite and then typically evolve in successive phases. An initial small reddish spot is visible at the site of the bite and, in about 50 per cent of the cases, a characteristic painless, non-itchy rash – named erythema migrans – slowly expands to 20 to 30 centimeters around it, often leaving the centre of the skin lesion to return to its original color.
In endemic areas of Lyme disease, this type of rash strongly suggests early Lyme infection. Flu-like manifestations also often occur in parallel with the rash and include fever, headache, muscle and joint pains, nausea and fatigue. Left untreated, complications could happen after several weeks, months or even years and include joint pains especially at the knee (arthritis), various neurological disorders such as meningitis (inflammation of the brain), abnormal muscle movements and/or paralysis due to nerves inflammation as well as heart rhythm problems.
The main challenge of Lyme disease is to recognise it when this is no rash or when complications start, usually several months or years after suffering from the tick bite. Undiagnosed, the patient may be treated inadequately for chronic arthritis or neurological illnesses over a long period. In such a case, the late diagnosis exposes the patient to serious morbidity with very poor quality of life.
The diagnosis is confirmed by serology tests that identify antibodies to the Borrelia bacterium.
Treatment should be started as soon as possible and is quite effective at the early stages of the infection. Antibiotics, especially doxycyclin and amoxicillin, are used in oral form for 2 weeks in early Lyme disease and in intravenous infusion for up to four weeks when complications have appeared.
There is currently no vaccine against Borrelia infection. Prevention first starts by avoiding areas infested by ticks known to carry the pathogen.
Those working in endemic areas or practicing adventure sports in such environments should always wear long trousers and long-sleeved shirts, use tick repellents and carefully check their whole body after returning from the wild. Ixodes ticks are smaller than common dog ticks and may be as small as the head of a pin. They often attach in difficult-to-see areas such as the armpits, scalp and groin. If you find a tick, use tweezers to slowly remove the insect from its head and disinfect the bite site.
If a rash or any suggestive symptoms occur, consult a medical professional for further tests and possibly treatment. In some high-risk individuals to whom the tick has remained attached for more than 24 hours, a single dose of doxycyclin might be given to prevent the occurrence of the infection but has to be taken less than 72 hours after the tick bite.
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@example.com.