Too close for comfort
Neglected Tropical Diseases Europe has largely been spared the scourge of neglected tropical diseases, but as insects that spread the parasites continue to thrive, an increasing number of cases are being diagnosed concerningly close to home.
“The problem is that for a lot of vector borne diseases, such as dengue fever, there is no quick fix,” explains Richard Allan, Director of the Mentor Initiative a humanitarian organisation that specialises in vector borne and tropical disease. “There are no drugs that can be given on mass to protect communities, and cure is complicated. Control is all about managing your environment - and that’s a real challenge.”
But it’s a challenge the world needs to face. According to the World Health Organisation the number of cases of dengue fever has increased from 0.4 million in 1996 to 3.2 million in 2015, and the epidemic is no longer contained in a handful of countries. Before 1970, only nine countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries with hundreds of cases reported in France, Italy, Spain and Greece.
Map showing the distribution of the dengue mosquito: Aedes albopictus, in Europe. Click to enlarge.
Dengue fever was historically found mostly in tropical settings, transmitted by Aedes aegypti mosquitoes. Aedes Albopictus, was only identified as a vector in 2005. It is an invasive species originally from S E Asia, that is able to outcompete local mosquito species in Africa and is rapidly establishing itself across the more temperate climates of Europe and America.
The vector responsible is aedes aegypti, a mosquito which has migrated from tropical and subtropical climates, to Mediterranean Europe. Whilst aedes aegypti is not well suited to the seasonal climate of Northern Europe, it’s hardy relative, aedes albopictus, which also carries the virus that causes dengue fever, is. “Every year there are sightings of the tiger mosquito [aedes albopictus] in the UK,” confirms Mr. Allan. “There have been no cases of dengue fever being contracted in the UK, but it’s just a matter of time.”
Another disease that is on the increase is leishmaniasis. Until now, leishmaniasis has been largely endemic in Asia, Latin America, Africa and the Middle East, where sand flies that spread the parasite live in cracks of buildings and breed in areas of refuse. Since the outbreak of the Syrian war, The Mentor Initiative report that the number of cases of leishmaniasis has grown from 40,000 annually to more than 200,000 at its peak in 2013.
Leishmaniasis has a number of different variants that cause horrific skin lesions and ulcers. “The images are the stuff of horror films,” says Mr. Allan. “We’ve seen children who literally have no face below the eye sockets.” In addition, the disease also occurs in another form that destroys vital organs and eventually kills. This less common visceral form of the disease is also increasing to very concerning levels.
The Mentor Initiative have helped to protect thousands of Syrians through the distribution of insecticide-treated sand fly nets and window and door curtains, alongside the spraying of homes. Whilst this helps to control the disease locally, the sand flies continue to breed and spread their disease much further afield. Cases of leishmaniasis are being reported across the Middle East and as far afield as Southern Europe.
So what can be done? In the last few months, breakthroughs in the development of a vaccine for dengue fever and the zika virus have offered some hope, but these are still years away from being rolled out for public health use. Whilst research goes on, the insects continue to thrive, spread disease and devastate countless lives.
The good news is; the disease is controllable through integrated vector management. If resources and finances are channeled to urban populations where the diseases thrive, we can control them. But success relies on public and political commitment at a serious scale.