Globalisation helps spread 'exotic' diseases

MEDICAL MATTERS: Infectious diseases now more common in Europe

DO YOU sometimes wish you could swap your ever-present but run-of-the-mill case of diabetes or asthma for something more exotic sounding? How about “well I’ve been diagnosed with Chagas disease” or “I’ve just shaken off the Chikungunya virus” as attention-grabbing conversation openers?

Well, be careful what you wish for: Europe is experiencing a growth of infectious diseases usually associated with other continents and other climates.

During a holiday in northern Italy some years ago, I became aware through local newspapers of alarm at the first ever outbreak of Chikungunya virus (CHIKV) in Europe. Some 334 cases of the disease were recorded in the northeastern province of Ravenna. According to a subsequent scientific analysis published in the journal Eurosurveillance, most cases were reported among people living in or visiting the initially affected villages of Castiglione di Cervia and Castiglione di Ravenna. Smaller clusters of local transmission were also detected in four towns in the same region, including the popular tourist spots of Ravenna and Rimini, which are located up to 50km from the initially affected villages.

CHIKV is spread by mosquitoes, specifically the bug Aedes albopictus. It looks as if the outbreak was caused by a double globalisation of both disease vectors and humans. In other words, a human host from a country where the disease is endemic transmitted the virus to local mosquitoes, which had adapted to a climate more temperate than their usual habitat.

While mainly a disease of Africa and Asia, the Italian outbreak and the virus’s re-emergence in countries in and around the Indian Ocean means CHIKV looks set to appear in other areas.

Is it a serious illness? Up to 25 per cent of people get no symptoms; those who do develop a high fever and severe joint pain. Other symptoms include headache, vomiting and muscle pains. Rarely fatal, the acute phase of CHIKV infection lasts about a week, although some people experience prolonged fatigue for longer periods. There is no specific treatment and there is no vaccine available to prevent infection.

Mosquitoes, sandflies and parasites aren’t the only culprits in this new wave of infections. The revolution in transport technologies and increasing global trade are driving the phenomenon. It seems globalisation is potentially a far greater challenge to public health in Europe than any future climate change.

Is Chagas disease something to fear? Only if you are travelling in Central and South America where about 7.5 million people carry the parasite Trypanosoma cruzior T cruzi. Named after the Brazilian physician Carlos Chagas, who discovered the disease in 1909, it is transmitted in the faeces of blood-feeding triatomine bugs.

Most people are not aware they have been acutely infected because the symptoms of fever and swollen glands are usually mild. But T cruzienters the human cells to reproduce, causing tissue inflammation. The infection is initially well controlled by the body's immune response, even though the parasite continues to move in and out of host cells.

However, up to 40 per cent of infected people go on to develop chronic Chagas disease, a nasty and sometimes fatal condition. Causing damage to heart muscle, the disease may lead to sudden cardiac death in endemic countries, mainly because of heart rhythm problems. Others develop heart failure and die within several years. In the gastrointestinal system, chronic inflammation leads to enlargement of the oesophagus and colon. Chronic constipation, tummy pain and swallowing difficulty are signs that Chagas is affecting these organs. Treatments include the drugs nifurtimox and benznidazole.

It seems likely infectious diseases, until now faced only by intrepid travellers, will become more common in Europe. A combination of higher summer temperatures, humidity and the greater movement of people and goods is the reason.