Urban control of Echinococcus multilocularis in France
Résumé
ln Europe, most cities are currently colonized by red foxes. (Vulpes vulpes) which are considered to be the main vector of the parasite Echinococcus multilocularis. The risk of transmission to humans is thus particularly worrying. The distribution of baits containing a wormer (praziquantel) has already shown promising results in rural areas and on small plots in urban areas. The purpose of this study was to assess the feasibility of such a treatment in Iwo medium-sized cities and their outskirts: Pontarlier and Annemasse. After five annual treatments over Iwo and a half years be!ween 2006 and 2009, the spring-time prevalence in foxes, as determined by ELISA tests on samples of faeces collected in the field, decreased from 13.3% to 2.1% in Annemasse. No prevalence differences were detected around Pontarlier (stable prevalence 10.9% - 7.0%). Working with veterinary clinics in the two towns also allowed us to screen the dog population in search of the parasite. More than one thousand samples were collected, among which only two were positive, one in each city. Thus, although bait distribution targeted toward fox populations has decreased E. multilocularis prevalence, it failed to prevent (indirectly) dog infection. Costs and benefits of these kinds of actions are discussed. What is at stake is the question of optimizing such actions by focusing treatments on higher risk areas (parks, urban gardens, green corridors, river banks, railways, etc.) with a higher bait distribution frequency (one per month). ln parallel, in 2006 the town of Nancy wanted to reduce the risk of human contamination by financing trappers to cull the fox population. The direct regulation of foxes though is a sensitive subject; in fact some people emphasize it as the final solution whereas it is considered to be cruel and useless by others. ln such a context, it is difficult to advice authorities without scientific facts. Therefore, we decided to implement a protocol of fox culling through night shooting whose aim is to assess the cost/benefits of such a control method. The study area is a 20km radius circle centred on Nancy. The northern half is devoted to fox culling while no change on the hunting pressure is made in the south. Each year of the study, which will last from 2008 until 2011, a batch of fox will be sampled homogeneously on each area from October to April. Intestines will be tested using the scrapping technique to assess the presence of Echinococcus worms. During the first session, the fox prevalence was 39% and 45% (north and south respectively) and reached 31% (north) and 40% (south) in the second year. ln the same time, fox populations were monitored by night counting showing IKAs of 6.1 and 4.9 foxes per 10km in the north whereas in the south theses indices were 4 and 3.7 for session one and Iwo respectively. Consequently, the culling protocol tested around Nancy seems to be poorly effective both on the fox population and on the fox prevalence. We still have to wait for the results of the third session to have a better comprehension of the real impact of fox culling.