populations of pigeon (Columba livia domestica), with records almost exclusively from Canterbury Cathedral, Rochester. Castle and King's College, Cambridge.
VECTOR-BORNE AND ZOONOTIC DISEASES Volume 11, Number 4, 2011 ª Mary Ann Liebert, Inc. DOI: 10.1089/vbz.2010.0079
Tick Surveillance in Great Britain Lisa J. Jameson and Jolyon M. Medlock
Abstract
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 nonnative 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. Key Words: Dermacentor reticulatus—Ixodes—Surveillance—Tick(s)—Vector.
Introduction
T
icks play a significant role as vectors of pathogens to both humans and animals throughout Europe ( Jongejan and Uilenberg 2004). In Great Britain (GB) there is a general consensus that the distribution and abundance of ticks is changing (Scharlemann et al. 2008), although the lack of reliable quantitative data makes the extent of this hard to determine. Better knowledge of the current distribution and abundance of ticks along with their host preference is essential to properly assess the risk posed to public and veterinary health by ticks and the pathogens they could potentially carry. The paucity of such data potentially hinders our ability to predict the effects of future climatic and environmental change on British ticks, particularly with contemporary dis-
tribution data on disease vectors considered to be a baseline requirement of any vector-borne disease risk assessment (Medlock and Jameson 2010). Before 2005 there existed no formal tick surveillance program in GB and limited contemporary data on nationwide tick biting, with the majority of surveys focusing in a particular geographic area or on a distinct host group. The many tick records collected during the 20th century were collated by the Biological Records Centre (BRC; www.brc.ac.uk), and this largely historical dataset was published by Martyn (1988). This data source suggests that 20 species of tick (Table 1) are considered to be resident in GB. The majority (17 species) belong to the family Ixodidae (hard ticks), which can be further separated into the following genera: Ixodes, Haemaphysalis, and Dermacentor. The three remaining species belong to
Medical Entomology & Zoonoses Ecology, Microbial Risk Assessment, Emergency Response Department, Health Protection Agency, Salisbury, Wiltshire, United kingdom.
403
404
JAMESON AND MEDLOCK Table 1. Number of Tick Records by Species in Great Britain, 1860–2001 (Biological Records Centre)
Resident
Exotic
Tick species
Common name
Records
Argas reflexus Carios maritimus Carios vespertilionis Dermacentor reticulatus Haemaphysalis punctata Ixodes acuminatus Ixodes apronophorus Ixodes arboricola Ixodes caledonicus Ixodes canisuga Ixodes frontalis Ixodes hexagonus Ixodes lividus Ixodes ricinus Ixodes rothschildi Ixodes trianguliceps Ixodes unicavatus Ixodes uriae Ixodes ventalloi Ixodes vespertilionis Amblyomma clypeolatum Hyalomma aegyptium Hyalomma marginatum Rhipicephalus sanguineus
Pigeon tick Marine argasid Short-legged bat tick Ornate cow tick Red sheep tick Southern rodent tick Marsh tick Tree-hole tick Northern bird tick Fox tick Passerine tick Hedgehog tick Sand martin tick Sheep tick Puffin tick Vole tick Cormorant tick Seabird tick Rabbit tick Long-legged bat tick Asian tortoise tick Tortoise tick Two-host tick Brown dog tick
17 18 124 90 84 15 68 229 29 99 196 740 74 1708 43 279 27 129 17 81 1 63 5 16 4152
the family Argasidae (soft ticks) in two genera: Argas (Horak et al. 2002 subgenera Argas and Carios) and Carios (Hillyard 1996). A number of other tick species belonging to the genera Aponomma, Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes, and Rhipicephalus have been recorded following importation on a variety of hosts, including migratory birds, humans, companion animals, livestock, and reptiles (Martyn 1988, Pietzsch et al. 2006, 2008, Jameson and Medlock 2009, Jameson et al. 2010); however, there is no evidence to support their ongoing survival and long-term establishment in GB. In GB particular attention has been given to Ixodes ricinus, the most abundant and widespread species and the main vector of Borrelia burgdorferi s.l., Anaplasma phagocytophilum (Guy et al. 1998), Babesia divergens (Zintl et al. 2003), and Louping ill virus (Laurenson et al. 2007). There is, however, a dearth of information on many other species of British tick; given their potential vector status for a number of potentially emerging pathogens, a greater understanding of their biology, ecology, and distribution is required. The majority of British tick species are specialist parasites of wildlife (Medlock et al. 2009), and the historical records provide evidence of their specialism (Martyn 1988). Nine species are parasites of birds that have been found in a variety of nesting sites from medieval buildings in southern England to sea cliffs on St. Kilda. There are certain species that appear to be confined to particular hosts: for example, Ixodes lividus occurs solely on sand martin (Riparia riparia), remaining in their colonies over winter; Ixodes rothschildi infests burrownesting coastal birds such as puffins (Fratercula arctica); and Ixodes unicavatus has only been recorded from cormorants (Phalacrocorax carbo) and shags (Phalacrocorax aristotelis). Argas reflexus, the pigeon tick, is associated with long-standing
populations of pigeon (Columba livia domestica), with records almost exclusively from Canterbury Cathedral, Rochester Castle and King’s College, Cambridge. Two species, Carios maritimus and Ixodes uriae, typically parasitize seabirds and are less host specific. The remaining three species are more terrestrial in their habits: Ixodes arboricola favors tree-hole nesting birds like great tit (Parus major) and blue tit (Cyanistes caeruleus); Ixodes frontalis parasitize passerines; and Ixodes caledonicus feed on birds nesting on cliffs and buildings, like pigeon and corvids. Eight species are specialist ticks of wild mammals. Two species, Ixodes vespertilionis and Carios vespertilionis, are bat parasites, the former favoring horseshoe bats and the latter, pipistrelles. Ixodes apronophorus prefers wetland habitats where it parasitizes water voles (Arvicola terrestris) and, historically, coypu (Myocastor coypus), with records centered on the Norfolk Broads and Wicken Fen. Two species, Ixodes acuminatus and Ixodes ventalloi, have only been reported from Cornwall, the Isles of Scilly, and the Island of Lundy. The former inhabits the burrows of small rodents, whereas the latter infest rabbits (Oryctolagus cuniculus) and several of its predators. The remaining three species are among the commonest British ticks. These include Ixodes canisuga, a parasite of badger (Meles meles), fox (Vulpes vulpes), and the domestic dog (Canis familiaris); the nidicolous Ixodes trianguliceps, which infests the nests of burrowing small mammals; and Ixodes hexagonus, a ubiquitous tick of hedgehog (Erinaceus europaeus). The apparent restricted distribution of many of these species is, however, likely a reflection of the limited investigation and recording effort, rather than a fragile existence in disseminated foci. In 2005 the Health Protection Agency (HPA) digitized all collated tick records held by the BRC, making the data freely
TICK SURVEILLANCE IN GREAT BRITAIN
405
Table 2. Number of Records and Ticks Submitted to the Health Protection Agency Surveillance Program Species Amblyomma sp. Carios vespertilionis Dermacentor reticulatus Haemaphysalis punctata Hyalomma marginatum Ixodes acuminatus Ixodes arboricola Ixodes canisuga Ixodes frontalis Ixodes hexagonus Ixodes lividus Ixodes ricinus Ixodes trianguliceps Ixodes ventalloi Ixodes species Total
Records
Male
Female
Nymph
Larvae
Total
1 3 8 1 1 1 11 6 71 72 8 680 21 2 76 962
0 0 14 0 1 0 0 0 0 7 0 630 0 0 4 656
0 4 33 1 0 1 4 1 102 303 5 1717 2 0 43 2216
1 0 0 0 0 0 33 8 3 71 1 807 3 2 38 967
0 16 0 0 0 0 0 0 2 22 5 229 37 0 22 333
1 20 47 1 1 1 37 9 107 403 11 3383 42 2 107 4172
available via the National Biodiversity Network (NBN) gateway (www.nbn.org.uk) and established a tick surveillance program with the following main objectives to (i) promote the surveillance of ticks in GB, (ii) monitor tick distribution on a nationwide scale, (iii) determine the diversity of ticks commonly infesting humans and animals, (iv) detect exotic/unusual tick species, and (v) collect a bank of specimens for future pathogen analysis. This article reports on the data collected between 2005 and 2009 and, where possible, provides a comparison with historical data to determine if changes in behavior, distribution, or diversity of species are detectable using this method of surveillance. It is anticipated that this approach could be used as a model for any country interested in a cost-effective system for nationwide monitoring of ticks.
Results Between 2005 and 2009 a total of 4172 ticks were collected through the tick surveillance program constituting 962 separate records (Table 2), the majority (63% of records; Fig. 1) from human and companion animal hosts. Fourteen tick species were represented, 12 known to occur in the United Kingdom as established species (I. ricinus, I. hexagonus, I. acuminatus, I. arboricola, I. canisuga, I. frontalis, I. lividus, I. trianguliceps, I. ventalloi, C. vespertilionis, Dermacentor reticulatus, and Haemaphysalis punctata), and 2 considered nonnative (Amblyomma sp., and Hyalomma marginatum). Seventy-one percent of the records and 81% of ticks submitted were I. ricinus. The second most common tick species was I. hexagonus (7.5% of records, 10% of all ticks), followed by I. frontalis (7.5%
Materials and Methods The majority of records were created following receipt of tick specimens sent to the HPA from members of the public, veterinarians, clinicians, wildlife charities, and academics from across GB. Upon arrival tick samples were stored at 808C until species determination. Ticks were identified to species level using morphological keys of Arthur (1963), Hillyard (1996), and Snow (1978). Additional data were also collected: date and location of collection, predominant habitat, and tick host. Anecdotal comments were often also provided in a comments section. A small proportion of records were also accepted from local recording schemes on the condition that sample specimens were sent to HPA for verification of identification proficiency. Where records were acquired through field surveys of vegetation, dragging was performed using a cotton cloth in accordance with Milne (1943). Data were stored in a database and mapped at the highest possible resolution (between 100 m and 10 km) using ESRI ArcGIS. Nationwide maps were developed on a 10 km resolution on the British national grid.
FIG. 1.
Number of records submitted by host type.
406
JAMESON AND MEDLOCK Table 3. Host Associations of Ixodes ricinus
Collected from
Common name
Records
Male
Female
Nymphs
Larvae
Total
Canis familiaris Homo sapiens Cervidae Felis cattus Environment Ovis aries Bos taurus Apodemus sylvaticus Not known Equus caballus Sylvia communis Erinaceus europaeus Dog/humana Sciurus carolinensis Capra hircus Total
Domestic dog Human Deer Cat Environment Sheep Cattle Wood mouse Not known Horse Whitethroat Hedgehog Dog/human Squirrel Goat
299 163 82 42 32 14 13 8 5 5 3 2 2 1 1 672
293 20 148 11 90 34 25 0 0 0 0 0 1 0 8 630
782 46 415 54 122 175 64 0 3 6 0 10 15 0 23 1715
15 254 20 3 452 11 0 0 6 1 5 5 3 24 3 802
7 91 2 1 115 1 0 11 0 0 0 0 0 0 0 228
1097 411 585 69 779 221 89 11 9 7 5 15 19 24 34 3375
Additionally, one female I. ricinus was found on fox (Vulpes vulpes) and wren (Troglodytes troglodytes); one nymph on blackbird (Turdus merula), great tit (Parus major), rabbit (Oryctolagus cuniculus), reed warbler (Acrocephalus scirpaceus), and vole; and one larva on chaffinch. a Recorder included ticks collected from the same location but removed from separate hosts in the same collection tube.
of records, 2.5% of ticks). Details of their host associations are shown in Tables 3–5. Fifty-three percent of all ticks submitted were female, followed by nymphs (23%), males (16%), and larvae (8%). The relative proportions of the tick stages varied enormously between the different tick species, and this is largely a reflection of their life history and host associations. For example, 96% of male ticks submitted were I. ricinus, 46% from dogs and 23% from deer, with male adults constituting only 5% of I. ricinus submitted from a human host. Female adult ticks were submitted from 11 different tick species, and for some this constituted the most frequent tick stage recorded, for example, 95% of I. frontalis. Nymphs were submitted from nine tick species, the majority (83%) were I. ricinus, followed by I. frontalis (7%) and I. arboricola (3%), and were the only tick stage submitted for I. ventalloi and Amblyomma sp. For I. arboricola, nymphs constituted 89% of submissions for this species. The majority of larval ticks were I. ricinus (69%), with the larval stage being the most frequently submitted stage for I. trianguliceps (88%), C. vespertilionis (80%), and I. lividus (45%). The most common host associated with I. ricinus was the domestic dog (Table 3), representing 44% (n ¼ 229) of all records and 32% (n ¼ 1097) of all ticks. A further 24% (n ¼ 163)
of records were from humans, 12% from deer (n ¼ 82), and 6% from cats (n ¼ 42). In terms of the number of ticks submitted, large numbers were submitted from dragging (n ¼ 779), deer (n ¼ 585), and humans (n ¼ 411). Females were the most common stage collected from deer, and nymphs most frequently collected from humans and by dragging. Considerable numbers of adult I. ricinus were also submitted from livestock, including cattle (25 #, 64 $) and sheep (34 #, 175 $); no immatures were submitted from cattle, and low numbers from sheep. Regarding the other host associations, I. ricinus were submitted from a range of medium and small mammals and birds, notably 23 females from a single goat and 24 nymphs from a single squirrel. I. hexagonus, known as the hedgehog tick, was submitted from a variety of hosts (Table 4). In keeping with its vernacular name, 29% of records and 33% of ticks (mostly females and nymphs) were from hedgehog. In addition, large numbers of records were submitted from companion animals: 56% of records and 60% of ticks (mostly females collected from dogs). Only two records of I. hexagonus were collected from humans. I. frontalis is typically a tick of passerines, and indeed all records submitted were from birds (Table 5). The majority of records were from collared dove (Streptopelia decaocto, 27%)
Table 4. Host Associations of Ixodes hexagonus Collected from Canis familiaris Erinaceus europaeus Felis cattus Environment Lutra lutra Homo sapiens Meles meles Mustela putorius Total
Common name
Records
Male
Female
Nymph
Larvae
Total
Domestic dog Hedgehog Domestic cat Environment Otter Human Badger Domestic ferret
27 21 11 3 3 2 2 1 70
1 6 0 0 0 0 0 0 7
186 86 7 1 9 2 7 3 301
23 34 5 1 1 0 2 5 71
1 8 3 1 3 0 0 6 22
211 134 15 3 13 2 9 14 401
Additionally, one female I. hexagonus was found on a chicken (Gallus domesticus) and a rat.
TICK SURVEILLANCE IN GREAT BRITAIN
407
Table 5. Host Associations of Ixodes frontalis Collected from Streptopelia decaocto Carduelis chloris Passer domesticus Columba palumbus Parus major Troglodytes troglodytes Turdus merula Sylvia atricapilla Sylvia communis Cyanistes caeruleus Turdus philomelos Total
Common name
Records
Male
Female
Nymph
Larvae
Total
Collared dove Greenfinch House sparrow Wood pigeon Great tit Wren Blackbird Blackcap Whitethroat Blue tit Song thrush
19 16 9 3 3 3 3 2 2 1 1 62
0 0 0 0 0 0 0 0 0 0 0 0
32 23 14 9 3 3 4 2 1 0 3 94
0 0 1 0 0 0 0 0 1 0 0 2
0 0 0 0 0 0 0 0 0 2 0 2
32 23 15 9 3 3 4 2 2 2 3 98
Additionally, one female I. frontalis was found on the following species: barn owl (Tyto alba), bullfinch (Pyrrhula pyrrhula), dunnock (Prunella modularis), long-tailed tit (Aegithalos caudatus), lesser redpoll (Carduelis cabaret), robin (Erithacus rubecula), scarlet-headed blackbird (Amblyramphus holosericeus), tree sparrow (Passer montanus), and unrecorded bird species.
and greenfinch (Carduelis chloris, 23%). Regarding the host associations of other species, all A. vespertilionis were found on pipistrelle bats; D. reticulatus were collected from humans, horses, dogs, and the environment via dragging; Ha. punctata from a human; I. acuminatus from a hedgehog; I. arboricola from blue tit, great tit (P. major), barn owl (Tyto alba), and yellowhammer (Emberiza citronella); I. canisuga from badger and dog; I. lividus from sand martin; I. trianguliceps from wood mouse (Apodemus sylvaticus), bank vole (Myodes glareolus), harvest mouse (Micromys minutus), and pygmy shrew (Sorex minutus); I. ventalloi from rabbit and blackbird (Turdus merula); Hy. marginatum from a horse; and Amblyomma sp. from a human.
FIG. 2.
Although the surveillance was not designed specifically to assess the seasonality of tick activity, appraisal of the seasonality of tick submissions through the 5 years and the seasonal nature of tick submissions by species present some interesting insights. Figure 2 shows the seasonal nature of tick records submitted to the HPA during the first 5 years of the scheme. Little can be said for submissions during 2005 as the program was still in its infancy; however, in the years following there are definite peaks in submissions during April– June of each year, often with a second peak (2006, 2007, and 2008) of submissions in September–October. Undoubtedly, the large number of I. ricinus submitted will impact greatly on this perceived seasonality of submissions.
Monthly submission of ticks to Health Protection Agency (HPA) 2005–2009.
408
JAMESON AND MEDLOCK Analyses of the habitat type supplied with each submission highlighted 48 submissions from either humans and/or their domestic animals while in their garden. In total, these records constituted 174 ticks: 112 I. ricinus (10 #, 31 $, 71 nymphs; 31 records); 52 I. hexagonus (41 $, 10 nymphs, 1 larva; 12 records); 9 Ixodes species (2 $, 2 nymphs, 5 larvae; 4 records). Ninetythree ticks were removed from human hosts (88 I. ricinus and 5 Ixodes sp.); 39 from dogs (22 I. ricinus, 13 I. hexagonus, and 4 Ixodes sp.); 39 from hedgehogs (1 I. ricinus and 38 I. hexagonus); and 2 from domestic rabbits (1 I. ricinus and 1 I. ventalloi). Sixteen garden-associated submissions reported the regular occurrence of wildlife (e.g., deer) all of which were subsequently identified as I. ricinus.
FIG. 3. Combined monthly submissions (2005–2009) of Ixodes ricinus records from humans (black) and dogs (gray).
Figure 3 shows the number of I. ricinus records submitted from humans and dogs. Clearly, there is a notable spring peak (April–June) of submissions and a smaller second peak in the autumn (September–October) for both humans and dogs, perhaps more apparent in dogs. By analyzing the data from dogs only, separating out the numbers of ticks (Fig. 4a) and records (Fig. 4b) submitted by month and by stage, it is evident that both female and male ticks on dogs were submitted in greater numbers during the spring (April–June), with a second peak in October. Larvae were only submitted in any number in July, with nymphs reported in each month from March to November. Although this apparent seasonality conforms to our understanding of I. ricinus seasonality (MacLeod 1939), care must be taken though in interpreting these data as this is not a true reflection of tick abundance. The numbers of ticks submitted per record (by stage) are given in Figure 4c. The highest number of male and female I. ricinus on a single dog was 18 and 49, respectively. Similarly, the data from humans can be analyzed further by the numbers of ticks (Fig. 5a) and records (Fig. 5b) submitted by month and by stage. What is immediately noticeable is the higher numbers of nymphs submitted from humans than from dogs and the seasonal peaks in nymphs (March–July) and larvae ( June–October) on humans. It is interesting that although nymphs often peak in habitats in lowland Britain during April and May (MacLeod 1939), peak submissions of nymphs on humans occurred in the latter 2 months ( June– July). Similarly, larvae were found on humans for large parts of the summer, but the numbers of larvae submitted peak in July–August, which conforms to our understanding of larval activity (MacLeod 1939). Unlike ticks submitted from dogs, those from individual humans usually numbered less than five (Fig. 5c). The highest number of female, male, nymphal, and larval I. ricinus on a single human was 6, 4, 27, and 31, respectively. Figure 6a and b provides an update to the nationwide distribution of I. ricinus mapped at 10 km resolution. The former illustrates presence data at a 10 km square for 2005– 2009; the latter illustrates new areas where I. ricinus have been reported in the last 5 years compared to the extensive historical data (between 1878 and 2001). It is notable that many of the squares where I. ricinus has been detected by the HPA scheme but have not been recorded in the historical dataset occur in the southwest of England (Fig. 6b).
Discussion The additional 962 records (4172 ticks) that the surveillance program have provided demonstrate that this method of recording is valuable for nationwide monitoring of the most common species but perhaps have limited use for rarer or more host-specific species. The proportion of tick species submitted (81% I. ricinus and 10% I. hexagonus) is not unexpected with the majority of records from humans and companion animals. Considering historical records of I. hexagonus on humans previously outnumbered those on dogs (Martyn 1988), it is surprising that only two I. hexagonus ticks were submitted from humans particularly given that >200 I. hexagonus ticks were submitted from dogs. Perhaps I. hexagonus ticks are more particular with their host preference than previously thought, or due to their nidicolous nature avail themselves to inquisitive companion animals more than humans. It is also worth considering that the preceding figures on host associations of I. hexagonus are biased toward records collected from humans during World War II, when I. hexagonus was a common biting nuisance in Anderson bomb shelters excavated in gardens (Arthur 1963). The dominance of certain life stages of each tick on different hosts is most likely influenced by a combination of seasonality and collector bias. For example, the preponderance of I. ricinus nymphs submitted from humans compared to dogs can be explained twofold. Ixodes ricinus females are more easily seen and therefore more likely to be brushed off before attaching to a human and therefore not collected and submitted to the HPA. It is also this visibility that makes them more likely to be detected on dogs than the smaller, less conspicuous nymph, which will be feeding on dogs to engorgement perhaps unnoticed and therefore not removed and submitted. The results of the program have drawn to our attention the public concern over the occurrence of host-seeking ticks in residential gardens. Although this is commonplace in parts of North America, it is a fairly new phenomenon in GB. In total, there were 48 submissions of ticks collected from humans and their domestic animals (records from cats were excluded due to their roaming nature) while in their garden. The majority of these gardens bordered woodland and/or pastures where animals graze, and 16 submissions specifically mentioned deer or other wildlife frequenting their garden. On occasion, individuals reported feeding wildlife in their gardens, or their garden being used as a laying up refuge for deer. Of particular interest is that although I. hexagonus ticks are being introduced into residential gardens and seek hosts other than wildlife they do not appear to be posing a significant biting nuisance
FIG. 4. (a) Numbers of I. ricinus submitted from dogs by month and stage. (b) Number of records submitted monthly by stage from dogs. (c) Numbers of ticks submitted per record (by stage) from dogs. L, larva; N, nymphs; M, males; F, females.
FIG. 5. (a) Numbers of I. ricinus submitted from humans by month and stage. (b) Number of records submitted monthly by stage from humans. (c) Numbers of ticks submitted per record (by stage) from humans. L, larva; N, nymphs; M, males; F, females.
409
410
JAMESON AND MEDLOCK
FIG. 6. (a) Distribution of I. ricinus records mapped at 10 km resolution. Since 2005; 1990–2004; 1969; þpre-1950. (b) Comparison of TRS and historical I. ricinus mapped at 10 km resolution. HPA; to humans. This indicates that only under exceptional conditions will I. hexagonus choose to commonly parasitize humans in contrast to I. ricinus, which can be a significant biting nuisance to humans in gardens. One reason for individuals submitting a specimen is concern either for themselves, a relative, or their pet animal having an infectious disease following a tick bite. Thirty reports specifically raised concerns regarding an infectious disease, and of those, only 13 specifically mentioned Lyme borreliosis. This indicates either a lack of concern or more probably a lack of awareness within GB. In contrast, only a small number (8) of specimens were not identified as ticks, demonstrating that while there may be limited awareness or concern for tick-borne diseases, in general, recorders could distinguish ticks from other invertebrates. Before availability of such surveillance data, it was unclear why the majority of Lyme borreliosis cases in the United Kingdom are reported between July and September, when nymphal activity is at its lowest, thus suggesting an involvement of larvae. However, while the total numbers of nymphs are lower in these months compared to their peak months of April–June, the months when humans most com-
1970–1990; historical;
1950– both.
monly report nymph biting are July and August. This may be explained by the increased exposure of humans to tick habitats during this time both in the United Kingdom and abroad during their summer vacation. Increasing incidence of I. ricinus identified in the southwest of England may be linked to an increase in roe deer (Capreolus capreolus) populations, which are known to have expanded in the region in the last 30 years (Ward 2005). With reports of urban deer populations (McCarthy and Rotherham 1994) and additional predicted expansion of this and other deer species, it is not unreasonable to expect further changes in the distribution or abundance of I. ricinus. All unusual findings were followed up with an investigatory field visit. Two incidents worth special attention are a female Ha. punctata found on a human in Hampshire and the detection of an established population of D. reticulatus in Essex ( Jameson and Medlock 2009). A preliminary investigation was conducted to determine if a population of Ha. punctata had established on Martin Down, 14 km south of Salisbury. This was the first record of this species from the area in 60 years, indicating that an isolated population may still be surviving. An initial survey in June 2009 found no ticks, but a
TICK SURVEILLANCE IN GREAT BRITAIN further survey will be conducted in summer 2010. Historical records of D. reticulatus are mostly restricted to western Wales and the southwest of England (Martyn 1988), where established populations are known to occur (Tharme 1993). A few additional records of this tick in southeast England (Reigate, Surrey, and Loughton, Essex) have been reported with no evidence of establishment or subsequent reports (Tharme 1993). Following two separate submissions to the scheme from different hosts (domestic dog and horses), a field-survey was conducted. One site, common land within a 20 m radius on the northeast outskirts of the village of Great Wakering (08470 5200 E, 518330 0800 N), was found to hold an established population of D. reticulatus (18 adults: 7 #, 11 $). All ticks were found questing
