Facing up to the increased risk of tick-borne disease

In tick-borne disease endemic areas medical personnel are well aware of the dangers faced by the local population, the differential diagnosis and treatment of clinical disease. However not all UK practice nurses — or GPs — are familiar with ticks, their removal and associated diseases, which may delay treatment

Tick-borne disease is on the increase throughout the northern hemisphere. There are two families of ticks, the soft or argasid ticks and the hard or ixodid ticks. Hard ticks, (which are related to spiders and scorpions, not insects), are endemic throughout much of Northern Europe, including the Highlands of Scotland and the New Forest. Several ixodid ticks act as vectors for transmission of disease but in the context of Northern Europe the predominant disease-bearing species is Ixodes ricinus (the castor bean tick). Although the extent of infestation is extremely variable, within an affected area there may be localised hotspots. People living and working in tick-infested areas have some awareness of these creatures but 'activity tourists' and holidaymakers may be unaware of the hazard. Despite the growth in this area of tourism, little research has been published on the tick-borne diseases suffered by the activity tourist.¹

TICK BORNE DISEASE

The major tick-borne disease in the northern hemisphere is Lyme disease, but a number of different diseases spread by tick bites that pose a threat to man are present in the tick population. Among these diseases are Tick Borne Encephalitis (TBE) a virus from the same family as yellow fever; babesiosis, a zoonotic disease affecting cattle, sheep, dogs and rodents, caused by parasites; and the bacterial diseases bartonellosis, ehrlichiosis and anaplasmosis.

There is continual westwards dispersion of Lyme disease and other pathogens transmitted by tick bite from East to West, and both Lyme disease and babesiosis are established in the British Isles. In parallel with this westerly spread, the latitude is gradually extending further north, and there is also an increase in the altitude at which ticks are active, possibly due to climate change.^2-4

This is of great concern to the UK since many tick-borne pathogens are now endemic in coastal Europe and only the North Sea provides a barrier to the spread of these diseases which no doubt will arrive at some point. Of greatest concern is TBE, which is a notifiable disease throughout the EU. Lyme disease is not a notifiable disease in the UK although Borrelia burgdorferi is a notifiable pathogen.

TICK LIFE CYCLE

Pathogens — bacterial, viral, and the protozoan parasite — are common in the small mammal population, such as bank voles and harvest mice, in the UK. The newly hatched tick larva, about the size of a poppy seed or full stop, typically takes its only blood meal from one such animal and thus acquires the infective organism(s), which is passed to the next, nymph, phase. Using special sensors on its forelegs, the nymph quests (seeks) a blood meal from a mammalian host, which may include man. During this feeding process it injects the infective organism. Once sated, after approximately 36 to 48 hours, the engorged tick falls off the host and buries itself in the leaf litter where it develops into the infected adult. This too requires a single blood meal after which the female develops eggs, which are buried in the ground and emerge after incubation as larvae in a continual cycle.

TBE virus is passed rapidly by the tick to the host whereas transmission of Borrelia occurs between 24 and 36 hours after attachment.⁵

All tick stages must be considered dangerous because although most organisms are passed between larval, nymph and adult stages of development, one of the most dangerous pathogens, TBE, is passed through the ovary of the infected female tick to the egg and then to the larva. While you may think that you would feel a tick biting, and therefore be able to swat it away before it becomes attached, ticks secrete a powerful local anaesthetic in their saliva so their bites are not felt; an anticoagulant component is secreted into the wound to facilitate feeding and yet another component of the saliva forms a cement plug that holds the tick in place until it has finished feeding.6.7

Ticks favour a damp, temperate microclimate near the roots of vegetation and can be found in forests, meadows, parks and even gardens. The larvae tend to concentrate at low levels whereas the larger nymphs and adults migrate upwards where they are more likely to contact larger host animals.

Not all ticks become infected from the primary host and not all infected bites develop into clinical disease. Some ticks have been shown to be co-infected with up to four different pathogens and co-infection does occur in humans making it more difficult to diagnose and treat than an infection by a single pathogenic entity.

GROUPS AT INCREASED RISK

Visitors to endemic areas whose reason for visiting necessitates prolonged contact with foliage in tick infested areas are at increased risk, as are the elderly and children.

Activity holidays, including camping, hiking, fishing, hunting as well as pursuits such as paint balling and high rope trails in forests, are a tourism growth area, facilitated by cheap flights to previously seldom visited destinations. The average stay of an activity tourist is usually short, but if the activity involves crawling through bracken and moorland the potential exposure may be intense. People visiting friends and relations in their home country for extended periods, often with young children and babies, are also at risk. An added concern is that TBE can be contracted from unpasteurised dairy products such as cheese and milk.⁸

In tick-borne disease endemic areas medical personnel are well aware of the dangers faced by the local population, the differential diagnosis and treatment of clinical disease. However not all UK GPs and practice nurses are familiar with ticks, their removal and associated diseases which may delay treatment — and reflect unfavourably on the professions involved.⁹

Seasonality

Most activity tourism pursuits take place during the peak tick activity period between end of March and the middle of November. This has a bearing on when cases of Lyme disease, TBE and anaplasmosis are likely to present, due to incubation period of the organisms concerned: if peak tick activity occurs in mid-to-late August, for example, the number of consultations for Lyme disease may be expected to peak in early-to-mid September.

• Lyme disease has an average incubation period of 15 days from bite to symptoms.
• TBE has an average incubation period 7-10 days in the range 2-28 days.^10,11
• Lyme disease and TBE may occur at any time of year.^12,13

PREVENTION

Vaccine is available against TBE, and should be recommended for travellers intending to visit areas where TBE is endemic (Table 1).

Adult and paediatric vaccines (TicoVac and TicoVac Junior) are available in the UK. They are specific to European subtype TBE with presumed efficacy against the Far Eastern subtype of TBE. Vaccination is recommended in the Green Book for travellers to forested parts of the endemic areas, for all people who hike, camp, hunt and undertake fieldwork.

The vaccine schedule is for three injections, the first two between one and three months apart with the third, five to twelve months later. An accelerated schedule can also by administered, with the first two injections two weeks apart and the third between five and twelve months later. Booster doses are suggested after three years for people who are still at risk.

REPELLENTS AND CLOTHING

There is no vaccine available for prevention of Lyme disease, Babesiosis or other tick borne diseases and therefore the priority is bite prevention.

Anyone travelling to tick infested areas and involved in an activity holiday where there is a danger of exposure to ticks should ensure that they use a proven repellent on all exposed skin. Examples include long acting diethyl toluamide (DEET) formulations ≥35% DEET or products containing ≥20% Picaridin.^14,15

Long trousers tucked into socks and closed toe shoes or boots, long sleeved shirts, a hat and neckerchief are recommended, depending on what activity is undertaken, and these can be pre-treated with permethrin solution, which is lethal to ticks.^12,13

TICK REMOVAL

Tick bites often occur in inaccessible areas of the body, including the scalp, groin, navel and axillae. TBE is transmitted quickly, probably within two to three hours of attachment but Lyme disease transmission requires the tick to have been feeding for >24 hours. Because bites are painless, it is important to check the body thoroughly, including between the toes, for the presence of a feeding tick (or ticks). It is important to remove the embedded tick promptly, either using a proprietary device (which should be included in the traveller's first aid kit) or sharp fine tweezers to grasp the tick just behind the head and to gently withdraw it. Care should be taken to remove the tick gently so as not to break the animal leaving its mouthparts in situ. Once the tick has been removed the area should be washed with a disinfectant such as chlorhexidine or cleaned with an alcohol skin wipe.

Removal methods such as applying heat from a cigarette end, grease (butter, petroleum jelly) or alcohol should never be used: they encourage the tick to regurgitate the contents of its gut and saliva into the wound, increasing the chance of infection. Using fingernails to 'pinch' out the tick poses similar risks to the person who has been bitten and to the person removing the tick, as the infective agent can enter the body through splits in the skin or nail bed.

If you remove a tick from a patient, it should be retained and sent to the Tick Recording Scheme at Public Health England, Porton Down — see Further Information.

CLOTHING

It is good practice to remove outdoor clothing (especially if damp outside) before entering the main living area to avoid bringing ticks indoors.

Ticks may live on or in clothing worn outdoors and can survive a hot wash cycle. The most effective way to kill ticks on clothing is by drying the clothes in a tumble drier. Ticks are very sensitive to humidity and the dry hot air kills all stages very effectively.¹⁶

PETS AS SENTINELS

Domestic pets can become seriously ill from the tick borne diseases, borreliosis, babesiosis and anaplasmosis.^17-18 The presence of ticks on animals is, however, a good indicator of the extent of tick infestation in the areas where the pet roams and provides a warning to the owner of the risk.¹⁹ Unfortunately pets are also a means of bringing the infestation into the home, and preventative application of fipronil to domestic pets is recommended.²⁰

DIAGNOSIS AND REFERRAL

The most important step in the diagnosis of potential tick-borne infection is to obtain a detailed history.

Patients should be routinely asked if they have had any recent holidays or trips to endemic areas. However, less than 50% of tick-borne disease patients remember being bitten. It is also possible to contract more than one tick borne disease from a single bite from a tick co-infected with more than one organism, so diagnosis can be a difficult and time-consuming process, and should be confirmed by serological testing.

The classical diagnostic feature of early Lyme disease is an expanding red rash with a pale centre — a typical bull's eye rash (erythema migrans), although this does not occur in everyone. Other symptoms include lethargy, fatigue, vague aches and pains, nausea and vomiting. For example, a mild fever, aching joints following a two-day deer stalking trip to the Highlands two or three weeks ago may prompt suspicion of Lyme disease and suggest the need to commence appropriate antibiotics before lab results are obtained.

Early diagnosis and treatment of Lyme disease with antibiotics is very effective and decreases the likelihood of the patient developing chronic disease. In its later stages, chronic Lyme disease causes a variety of life changing conditions including neuroborreliosis, cardiac conduction problems, paralysis, blindness, meningitis, multiple arthritic joints, dermatitis and cardiac damage. Deaths from complications of Lyme disease have been recorded in the UK.²¹

Public Health England has a suggested referral pathway for patients with symptoms of Lyme disease. ( www.hpa.org.uk/webc/HPAweb_C/1317141297288.) Obtaining the relevant laboratory confirmation can take several weeks and false negatives in the early stages of Lyme disease are common, but circumstantial evidence is sufficient to suspect Lyme disease or TBE, and treatment should be commenced immediately according to clinical protocols.

Symptoms of TBE include high temperature, headache, stiff neck; you may suspect TBE if this cluster of symptoms presented in a patient with a history of having been camping in the woods in Russia and fishing the River Varzuga. If the patient has not been vaccinated, these symptoms and history should prompt urgent referral for possible TBE.

Treatment for TBE is as for most viral illness: support and alleviation of symptoms. No specific drug therapy is available.

INCREASING AWARENESS

Many people believe that the risks of tick borne diseases are overstated and frequent comments appear on bulletin boards to that effect. Organisations such as Lyme Disease Action and Borreliosis and Associated Diseases Awareness (BADA UK) have produced a number of publications for both public and professional use.

CONCLUSION

If the opportunity presents before travel, offer advice, especially to activity tourists, on avoiding bites through the correct application of suitable insect repellent, wearing pre-treated clothing if appropriate, and checking the body for the presence of ticks.

However, the most likely contact that the practice nurse will have with the vulnerable traveller will be for the removal of embedded ticks and treatment of symptoms on their return.

REFERENCES

1. Hagen K. [Risk of infections among orienteers]. Tidsskr Nor Laegeforen. [Review]. 2009 Jun 25;129(13):1326-8.

2. Jaenson TG, Lindgren E. The range of Ixodes ricinus and the risk of contracting Lyme borreliosis will increase northwards when the vegetation period becomes longer. Ticks Tick Borne Dis. [Research Support, Non-U.S. Gov't]. 2011 Mar;2(1):44-9.

3. Jaenson TG, Jaenson DG, Eisen L, Petersson E, Lindgren E. Changes in the geographical distribution and abundance of the tick Ixodes ricinus during the past 30 years in Sweden. Parasit Vectors. [Research Support, Non-U.S. Gov't]. 2012;5:8.

4. Palo RT. Tick-borne encephalitis transmission risk: its dependence on host population dynamics and climate effects. Vector Borne Zoonotic Dis. 2014 May;14(5):346-52.

5. Patton TG, Dietrich G, Brandt K, Dolan MC, Piesman J, Gilmore RD, Jr. Saliva, salivary gland, and hemolymph collection from Ixodes scapularis ticks. J Vis Exp. [Video-Audio Media]. 2012(60).

6. Chmelar J, Anderson JM, Mu J, Jochim RC, Valenzuela JG, Kopecky J. Insight into the sialome of the castor bean tick, Ixodes ricinus. BMC Genomics. 2008;9:233.

7. Chmelar J, Calvo E, Pedra JH, Francischetti IM, Kotsyfakis M. Tick salivary secretion as a source of antihemostatics. J Proteomics 2012 Jul 16;75(13):3842-54.

8. Kriz B, Benes C, Daniel M. Alimentary transmission of tick-borne encephalitis in the Czech Republic (1997-2008). Epidemiol Mikrobiol Imunol. 2009 Apr;58(2):98-103.

9. Fitzpatrick K. Mum claims GP sent daughter to vets to remove tick from her head. Manchester Evening News. 2014 June 5th 2014.

10. Dryden MS, Saeed K, Ogborn S, et al. Lyme borreliosis in southern United Kingdom and a case for a new syndrome, chronic arthropod-borne neuropathy. Epidemiol Infect. 2014 May 9:1-12.

11. Kaiser R. Tick-borne encephalitis: Clinical findings and prognosis in adults. Wien Med Wochenschr. Comparative Study Review. 2012 Jun;162:239-43.

12. Miller NJ, Rainone EE, Dyer MC, Gonzalez ML, Mather TN. Tick bite protection with permethrin-treated summer-weight clothing. J Med Entomol 2011;48(2):327-33.

13. Couch P, Johnson CE. Prevention of Lyme disease. Am J Hosp Pharm 1992;49(5):1164-73.

14. Pages F, Dautel H, Duvallet G, Kahl O, de Gentile L, Boulanger N. Tick repellents for human use: prevention of tick bites and tick-borne diseases. Vector Borne Zoonotic Dis 2014 Feb;14(2):85-93.

15. Carroll JF, Benante JP, Kramer M, et al. Formulations of deet, picaridin, and IR3535 applied to skin repel nymphs of the lone star tick (Acari: Ixodidae) for 12 hours. J Med Entomol 2010 Jul;47(4):699-704.

16. Carroll JF. A cautionary note: survival of nymphs of two species of ticks (Acari: Ixodidae) among clothes laundered in an automatic washer. J Med Entomol 2003;40(5):732-6.

17. Cary NR, Fox B, Wright DJ, Cutler SJ, Shapiro LM, Grace AA. Fatal Lyme carditis and endodermal heterotopia of the atrioventricular node. Postgrad Med J 1990;66(772):134-6.

18. Jennett AL, Smith FD, Wall R. Tick infestation risk for dogs in a peri-urban park. Parasit Vectors 2013;6:358.

19. Day MJ. One health: the importance of companion animal vector-borne diseases. Parasit Vectors 2011;4:49.

20. Leschnik M, Feiler A, Duscher GG, et al. Effect of owner-controlled acaricidal treatment on tick infestation and immune response to tick-borne pathogens in naturally infested dogs from Eastern Austria. Parasit Vectors 2013;6:62.

21. Dubrey SW, Bhatia A, Woodham S, et al. Lyme disease in the United Kingdom. Postgrad Med J 2014;90:33-42.