Tick Surveillance in Great BritainArchived

Jameson LJ, Medlock JM.Medical Entomology & Zoonoses Ecology, Microbial Risk Assessment, Emergency Response Department, Health Protection Agency , Salisbury, Wiltshire, United kingdom .Vector-Borne and Zoonotic Diseases, 2010 Sep 17, ahead of print. doi:10.1089/vbz.2010.0079

The ability for public/veterinary health agencies to assess the risks posed by tick-borne pathogens is reliant on an understanding of the main tick vector species. Crucially, the status, distribution, and changing trends in tick distribution and abundance are implicit requirements of any risk assessment; however, this is contingent on the quality of tick distribution data. Since 2005 the Health Protection Agency has promoted an enhanced tick surveillance program. Through engagement with a variety of public and veterinary health agencies and practitioners (e.g., clinicians and veterinarians), wildlife groups (deer society, zoos, animal refuge centers, and academics), and amateur entomologists, >4000 ticks from 900 separate records across Great Britain have been submitted, representing 14 tick species (Ixodes ricinus, Ixodes hexagonus, Ixodes acuminatus, Ixodes arboricola, Ixodes canisuga, Ixodes frontalis, Ixodes lividus, Ixodes trianguliceps, Ixodes ventalloi, Carios vespertilionis, Dermacentor reticulatus, Haemaphysalis punctata, Hyalomma marginatum, and Amblyomma species). The majority of ticks submitted were I. ricinus (81%), followed by I. hexagonus (10%) and I. frontalis (2.5%). Predominant host groups include companion animals (411 records), humans (198 records), wild birds (111 records), and large wild mammals (88 records), with records also from small/medium wild mammals, livestock, the environment and domestic/aviary birds. The scheme has elucidated the detection of two non native tick species, the expansion of previously geographically restricted D. reticulatus and produced ground data on the spread of I. ricinus in southwest England. It has also provided a forum for submission of ticks from the concerned public and particularly those infected with Lyme borreliosis, thus raising awareness among public health agencies of the increased peri-urban tick problem in Britain. Our results demonstrate that it is possible to run a cost-effective nationwide surveillance program to successfully monitor endemic tick species, identify subtle changes in their distribution, and detect the arrival and presence of exotic species.

VBORNET comment: 2010-12-07

This paper is a really nice analysis of results provided by a national tick surveillance program conducted from 2005 and 2009 in Great Britain by HPA. This study shows that useful information on tick distribution and ecology can be obtained from passive surveillance based on punctual records from public, veterinarians, clinicians, wildlife charities and academics from across Great Britain. This is a good example of how it may be possible to organize and encourage all these actors to report any single fact that may be included in a national database and then acquire an epidemiological significance. However, such type of sampling presents some biases (which the authors seem to be aware of) like host preferences or distribution changes since samples mainly come from individuals or professionals related to public health problems or pet issues. For example, the apparent extension or at least increase of abundance of Ixodes ricinus in the south-western part of the country is difficult to be interpreted since we do not know if the historical sampling effort was the same as the HPA recent one. The solution to resolve such issue of heterogeneous data and methods may be to develop distribution models based on presence data for both periods and see if the predicted suitable areas are different or not. Because one of the explanations proposed by the authors is the increase of the deer population in this region, likely vertebrate host density should be included in the models.