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Hyalomma m. marginatum

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Dartmoor Tick Watch 2009 - Final Report

 

The total of all ticks collected in 2009 on and around Dartmoor was 3,443. The breakdown of tick species and their life cycle stages is shown in Table 1.

Tick Male Female Nymph Larva Totals
Sheep tick 318 588 799 1443 3148
Hedgehog tick 3 149 83 53 288
Vole tick     4   4
Ornate cow tick 1       1
Rabbit tick*     1   1
Hyalomma** 1       1
Overall totals: 323 737 887 1496 3443

Table 1. Overall final tick numbers, Dartmoor 2009
* The first confirmed rabbit tick recorded on the UK mainland
** An "alien" tick, imported on a horse from Portugal.

There were at least sixty-three collectors involved, including six veterinary practices which are each counted as one collector, however several members of staff were involved at some of the practices.

Ticks were collected from cats, dogs, hedgehogs, sheep, ponies and people, as well as from grass, leaf litter and bracken.

The results in Table 1 are of interest for the overall numbers and for the locations that the ticks came from (see Figure 1). This  information will be used by the Health Protection Agency's Tick Recording Scheme. They are not, however, representative of the naturally occurring frequency of all the life cycle stages because most individuals did not collect the smallest stage (larvae) from animals or themselves. For example, only one larva was collected by a walker, on himself, whereas blanket "dragging" in three given habitats collected 1,417 larvae. This is significant because a female tick lays e.g. 1,000 eggs that hatch into larvae. Of these, perhaps only 100 larvae survive to feed and metamorphose into nymphs and of these only 2 feed and metamorphose into adults, male and female. There is a high mortality rate due to starvation, predation and possibly weather conditions.

On the other hand, quite a few of the smaller stages, particularly hedgehog tick nymph and larval stages, were collected by veterinary staff. A noteworthy example was the 132 hedgehog ticks collected from a one-month old puppy that had never left a garden: this included 67 nymphs and 50 larvae as well as 14 females (with no males).

The locations from where ticks were collected are shown in Figure 1.

 

Figure 1. Diagrammatic map of locations where ticks were found.
Many areas were not sampled.

Figure 1 does not show tick sites in Torquay or Haldon Forest to the east for practical reasons in preparing the drawing. The alien tick imported from Portugal is also not included. Most of the moor was not sampled systematically, with results dependent on walkers and dog-owners who took part in the project. It is clear that the Plymouth area (at bottom left on Fig. 1) yielded ticks from several locations - this would probably be true for much of the area around the moor where sheep and deer can be found. These locations also include people's gardens, where hedgehogs and rodents carry ticks.

 

                                                                                                                                               

 

The ticks collected twice-monthly from different habitats are shown in Table 2. These were collected by dragging a white woollen blanket over the ground.

  Male Female Nymph Larva   Totals
             
Brisworthy 5 3 135 37   180
Ringmoor Down 3 6 180 25   214
Yarner Wood Y2 18 19 382 1354   1773

Table 2. Tick totals from different habitats, 2009.

The habitats were:

  1. Brisworthy, an area of semi-sheltered bracken next to Brisworthy Plantation that ranges from 260 to 280 metres in elevation,
    Ordnance Survey grid reference: SX 557 659

  2. Ringmoor Down, an area of high, exposed, open grass that is 300 metres in elevation,
    Grid reference: SX 566 666

  3. Yarner Wood (Y2 area), a sheltered woodland 170 to 180 metres in elevation with an east facing aspect, generally sheltered,
    Grid reference: SX 781 788.

                                                                                                                                               

 

The ticks in the Yarner Wood Y2 sample area are shown in Table 3 and Figures 2 & 3.

Tick stage Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec   Totals
Larvae 0 0 1 21 236 290 133 310 311 50 3 0   1355
Nymphs 24 21 17 37 81 31 40 40 25 49 7 10   382
Female 0 0 0 2 3 3 5 3 1 1 0 1   19
Males 0 1 0 3 1 2 4 5 2 0 0 0   18

Table 3. Sheep ticks collected at Yarner Wood (Y2 sample area).

 



Figure 2. The periodicity of all sheep tick life cycle stages in Yarner Wood Y2 sample area, 2009
 

a. Larvae
 
b. Nymphs
 
c. Females  d. Males

Figure 3. The periodicity of tick life cycle stages in Yarner Woods Y2 sample area, 2009

 

The ticks in Figures 2 & 3 were collected from a sampling area of 452 square metres from an area known as the Horse Circle, an old, cleared area in the wood for training horses. They were collected by dragging a blanket (1 m wide x 1.5 m long) 452 metres slowly over the ground. If these results are extrapolated to encompass the entire wood then the results obtained are shown in Figure 3.

Due to bad weather and commitments, only one rather than two samplings were made in Feb. 2009.

In November and December 2009 a second sampling was done but no ticks were collected, probably due to prior very wet weather conditions.

 

Figure 4. Extrapolated figures showing the periodicity of all tick life cycle stages in Yarner Wood (entire wood), 2009

The total area of Yarner Wood is calculated to be 140.44 hectares using Memory Map. The wood measures 2.04 km east-west by 1.09 km north-south (in statute units, 347 acres, 1.26 miles east-west and 0.66 miles north-south).

The data shown in Fig. 4 are those from the highest single sampling in any one month. No allowance is made for locations in the wood where ticks would probably not be found e.g. on hard tracks, water surfaces, and the cross-sectional area of the trees.

                                                                                                                                               

 

Another source of ticks throughout the year came from two dogs, principally from Barney, a long-haired golden Retriever, and to a lesser extent from his companion, Charley, a shorter-haired yellow Labrador. The owners were very diligent in removing ticks on a regular basis. The dogs were exercised regularly at Steps Bridge and the "Steps Bridge" entry in Table 3 shows these ticks. However, there is the possibility of cross-over because the dogs were also walked at widely different places on the moor and some ticks came from these other locations. The "Overall" entry in Table 4 refers to all the ticks removed from the two dogs.

 

  Male Female Nymph Larva   Totals
             
Steps Bridge 178 201 0 0   379
Overall 226 270 3 0   499

Table 4. Sheep ticks collected by Barney and Charley, two dogs.

 

Figure 5. Sheep ticks collected from two dogs, exercised at Steps Bridge and other Dartmoor locations.

 

                                                                                                                                               

 

The ticks in the Brisworthy sample area are shown in Table 5 and Figure 6.

Tick stage Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec   Totals
Larvae --- 0 0 1 18 0 7 0 11 0 0 0   37
Nymphs --- 5 30 50 18 7 9 5 2 9 0 0   135
Female --- 0 0 2 0 1 0 0 0 0 0 0   3
Males --- 0 0 5 0 0 0 0 0 0 0 0   5

Table 5. Sheep ticks collected at Brisworthy.


Figure  6. The periodicity of all sheep tick life cycle stages at the Brisworthy sample area, 2009

Further analysis of the Brisworthy ticks appears not to warrant separate figures, the results for the life cycle stages are shown in Table 4. There was no sampling in January.

                                                                                                                                               

 

The ticks in the Ringmoor Down sample area are shown in Table 6 and Figure 7.

Tick stage Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec   Totals
Larvae --- 0 0 0 20 0 5 0 0 0 0 0   25
Nymphs --- 0 0 17 69 64 8 4 4 16 0 0   182
Female --- 0 0 1 0 2 0 0 1 4 0 0   8
Males --- 0 0 1 0 0 0 0 0 2 0 0   3

Table 6. Sheep ticks collected at Ringmoor Down.


Figure  7. The periodicity of all sheep tick life cycle stages on the Ringmoor Down sample area, 2009

Further analysis of the Ringmoor Down ticks appears not to warrant separate figures, the results for the life cycle stages are shown in Table 5. There was no sampling in January.

                                                                                                                                               

 

It is not understood why  the Brisworthy and Ringmoor Down results show so few larvae compared to the Yarner Wood results. As stated above,  under Table 1, there are normally far more larvae produced than any other stage in the tick life cycle. It would be expected that there would be many more times as many larvae as there were nymphs. It is possible that they were not "questing" i.e. waiting high on the vegetation for potential hosts to pass by at the same time as the nymphs and adults, although this was not true for the Yarner Wood results. The samples were always collected at the same time of day - late-morning into early afternoon. The larvae may have a different diurnal rhythm to the other life stages.

It can be seen from all the habitat results that there were two peaks of activity to some extent before and after either June or July, depending on the habitat. This was confirmed anecdotally by a sheep farmer who collected ticks for the project - mainly from his sheep dogs but also from sheep, especially in 2008 (these are not included in these results for 2009).

                                                                                                                                               

 

An attempt has been made to present the results in a more user-friendly form in Table 7. This resulted in a monthly tick "index" where the number presented represents the notional distance between ticks on the ground, assuming that they are equally distributed on a square grid. This was done using the highest result in a given month, thus showing the worst-case scenario for each habitat.

Habitat Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Ringmoor Down
open grass - high moor
n/s* None None 7.3 4.2 3.9 10.5 15.8 15.8 9.5 None None
Brisworthy - bracken
edge of high moor
n/s* 13.1 4.6 4.8 3.9 7.9 6.2 10 6.2 9.1 None None
Yarner Wood
sheltered, not so elevated
7.5 4.5 6.7 3.4 1.0 1.2 2.1 1.3 1.3 2.8 6.7 6.4

Table 7. Dartmoor tick indices.
Notional distances (metres) between ticks assuming they are distributed in a square grid pattern
(n/s* - not sampled).

 

The tick "index" may be a useful tool for risk assessment when planning outdoor activities on the moor.

                                                                                                                                               

 

Anecdotes

Something not seen in scientific reports - this section lists some anecdotal evidence about ticks that has accrued during the project.

  1. We are seeing more ticks this year, especially on the faces of dogs running through undergrowth.

  2. More ticks last year (Farmer).

  3. Ticks don't get so big on horses.

  4. Ticks were quiet this summer until September (Source: PH1-Yarner).

  5. A tick found on the shin despite being well-covered with boots, trousers and gaiters.

  6. More ticks on someone last year compared to this year.

  7. Are some people more attractive to ticks than others (same for midges, horseflies etc.)?

  8. Talking about wearing shorts, person with boots, tucked-in long trousers and long-sleeved shirt-  ticks found around neck area!

  9. Believe ticks may jump.

  10. Ticks seem to come on the breeze sometimes, airborne?

  11. More ticks in Yarner Wood after roe deer got more numerous.

  12. Believe ticks may jump.

  13. Ticks were on a dog last winter

  14. Account of incidence of red water disease (Babesiosis) cattle some years ago in Milton Combe

  15. Incidence of a tick fever in cattle that attacked white blood cells (Ehrlichiosis).

  16. Ticks don't get so big on horses (again).

  17. One nymph was seen to "jump" 4-5 cm away from its position on the blanket as I tried to pick it off, this happened twice in quick succession with the same tick! Not seen previously - due to static electricity? Definitely not the "hoppers" seen on 22 Dec.

  18. Many more ticks now compared to ten years ago.

  19. One tick was lost after running like a spider (long experience - SAMP2)

  20. One tick wafted more than 1.5 meters away (more than the length of the collecting blanket) on a gentle breeze while dropping it about 2 cm into the collecting dish - therefore, small ticks (proven unfed nymphs and presumably also lightweight larvae) CAN travel on the wind and blow into houses? (as per PH1's wife's anecdote, 17 Oct) 

  21. Ticks seen in the snow before (KM)

  22. There were more ticks around last winter, it was not so cold.

  23. Static electricity was generated by removing and replacing the lid of the plastic collecting dish. In one instance, four ticks collected first 'jumped' up to the lid when it was replaced, second instance was on removing the lid when one tick was suspended by static charge about 4 cm from the lid and from the base, then it 'flew' away on a breeze.

  24. Ticks on sheep tend to be around the mouth area.

  25. The large ticks survive longer in the collecting dishes (contain more water?).

  26. I have read that ticks meet and mate on the host - this is true, as seen on the Photos page (third row up from bottom) - BUT, equally true, unfed male and female ticks collected separately on Ringmoor Down and beside Brisworthy Plantation mated when put into the collecting dishes together.

  27. Eating garlic keeps ticks at bay - it changes body odour, also good against mosquitoes.

  28. Rubbing a finger tip in a circular motion around an attached tick can cause it to release and drop off.

  29. "Ticks can fly" - by lifting legs up on one side, standing more or less on just one or two legs and catching the breeze deliberately. I have seen something similar when collecting off the blanket:

    1. Is it an escape mechanism?

    2. It was suggested today that perhaps they reach passing sheep in this manner - so that it is perhaps a host-finding mechanism?

    3. Another possibility is that this could be a dispersal mechanism under appropriate conditions, similar to small spiders parachuting away?

  30. KR - Headless nymph without 1st pair of legs walked off the microscope slide and across the dissecting microscope stage during preparation.

  31. "Ticks can fly" - by lifting legs up on one side, standing more or less on just one or two legs and catching the breeze deliberately. Seen again by the previous reporter (see 2 June 2009).

  32. Small ticks can escape from the plastic Petri dishes ..... (again)

  33. Ticks prefer clean skin, don't shower before going on the moor?

  34. Ticks prefer women, coinciding with monthly cycles - this was disputed by an older lady who gets a lot of ticks!

  35. Covering up doesn't help some individuals.

  36. More ticks this year than ever before? Concurs with ....

  37. More ticks this year than ever before? (Bodmin Moor area).

  38. There are getting to be more ticks every year.

  39. Ponies get ticks all year round.

  40. Two foresters told me they had seen fewer ticks in Yarner Wood this year ..... maybe it depends on habitat factors?

  41. Warden said fewer ticks/tick bites this year - too wet for them?

 

                                                                                                                                               

 

Acknowledgements .....

I am grateful to the companies who sponsored this project, namely Millipore (UK) Ltd, Agar Scientific Ltd,  Whatman plc, Plymstock ComputersCompassworks, Dartmoor News, Brian Reece Scientific Ltd, without whose material support it would not have been possible. Also, to the various individuals who went to the trouble of collecting and sometimes mailing ticks to me or storing them, often in their freezers, until I could collect them.

Particular thanks go to Estover Veterinary Hospital, Plymouth, and Woodlands Veterinary Centre, Ivybridge, for their continued efforts in collecting ticks. It was from Estover that the only ornate cow tick was collected and from Woodlands that the first rabbit tick to be confirmed on the UK mainland was collected. Special thanks go also to David & Corrina Legassick for various numbers of ticks from sheep and sheep dogs and to Stephen & Janet Jenkins for the 499 ticks collected from Barney and Charley, their dogs.

Collectors - from the web site's "Thank you" page

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