Leishmaniasis emergence in EuropeArchived

P.D. ReadyDepartment of Entomology, Natural History Museum, London, United KingdomEurosurveillance, March 2010, 15(10):pii=19505, 29-39

Leishmaniasis emergence in Europe is reviewed, based on a search of literature up to and including 2009. Topics covered are the disease, its relevance, transmission and epidemiology, diagnostic methods, treatment, prevention, current geographical distribution, potential factors triggering changes in distribution, and risk prediction. Potential factors triggering distribution changes include vectorial competence, importation or dispersal of vectors and reservoir hosts, travel, and climatic/environmental change. The risk of introducing leishmaniasis into the European Union (EU) and its spread among Member States was assessed for the short (2-3 years) and long term (15-20 years). There is only a low risk of introducing exotic Leishmania species because of the absence of proven vectors and/or reservoir hosts. The main threat comes from the spread of the two parasites endemic in the EU, namely Leishmania infantum, which causes zoonotic visceral and cutaneous leishmaniasis in humans and the domestic dog (the reservoir host), and L. tropica, which causes anthroponotic cutaneous leishmaniasis. The natural vector of L. tropica occurs in southern Europe, but periodic disease outbreaks in Greece (and potentially elsewhere) should be easily contained by surveillance and prompt treatment, unless dogs or other synanthropic mammals prove to be reservoir hosts. The northward spread of L. infantum from the Mediterranean region will depend on whether climate and land cover permit the vectors to establish seasonal biting rates that match those of southern Europe. Increasing dog travel poses a significant risk of introducing L. infantum into northern Europe, and the threat posed by non-vectorial dog-to-dog transmission should be investigated.

This review addresses the current situation of leishmaniasis in Europe on the basis of recently published documents (most of them during the last 10 years). According to WHO reports, the worldwide public health impact of leishmaniasis has been grossly underestimated for many years. In Europe only southern countries are affected, the high prevalence of asymptomatic human carriers of L. infantum suggesting that this parasite is a latent public health threat. This was demonstrated by the increase of co-infections with human immunodeficiency virus (HIV) and Leishmania that has been observed since the 1980s. Risks of emergence or re-emergence of leishmaniasis in Europe are considered under three scenarios:

1. the introduction of exotic Leishmania species into Europe via traveling of humans and domestic dogs, 
2. the natural spread of visceral and cutaneous leishmaniasis caused by L. infantum and L. tropica from the Mediterranean region of Europe to neighbouring countries, 
3. the re-emergence of disease in the Mediterranean region of Europe caused by an increase in the number of immunosuppressed people. Geographical distribution maps for Europe (updated to 2009) of human leishmaniasis due to L. infantum and L. tropica and also of the main vectors are given at country level.

These maps are interesting, however their low precision needs to be taken into account, i.e. Germany appears in grey colour, suggesting colonization by P. perniciosus, whereas only a single observation has been reported so far from that country, moreover on a site having undergone dramatic environmental modifications suspected to have led to the extinction of that population. Updated maps will be edited at lower scale (admin nuts3 level) for these vectors within the VBORNET programme. Risk prediction models based on compartmental mathematical (R0) models have been developed within the EU-founded research programme EDEN and huge amount of data have been compiled and made accessible, also by LeishRisk, another international collaborative project, for the peer-reviewed literature on leishmaniasis epidemiology. However, it is stressed that public health and veterinary surveillance data are still fragmentary and in accordance to WHO recommendations, it is stated that more surveillance is necessary in Europe to assess an emergence of leishmaniasis. The author put the emphasis on the need of better coordination of existing surveillance, on notification of leishmaniasis, as they are notifiable in some countries (Greece, Italy, Portugal, Turkey, parts of Spain) and not in others (France), and on surveillance of dog travel. As for the vectors, data sharing on their current distribution is now in place (VBORNET programme) but monitoring of presence and abundance provides also key data for assessing and managing risk of transmission.