Mother that's not a mole, its got legs'. This memorable phrase arose during a consultation with an elderly lady and her daughter in a suburb of London. The offending 'mole' turned out to be a tick. Tick bites can be a problem anywhere where people spend time in gardens and parks.
Ticks are second only to mosquitoes as the most common vectors for disease transmission to man. British-reported cases of Lyme disease rose from 292 in 2003 to 813 in 2008.1 Many cases remain unreported, as Lyme disease is not notifiable in England and Wales.
Returning travellers account for 15-20 per cent of cases and a few cases are occupational (farmers, deer handlers, zoo and forestry workers, gamekeepers and vets).
Named after an outbreak of arthritis affecting children in the Lyme district of Connecticut, Lyme disease is caused by the bacteria Borrelia burgdorferi.
Heat and movement attract ticks. Brushed from vegetation onto exposed skin they can travel across the body. Bites may be in the groin, axillae or perianal area. More than 80 species of ticks carry human disease in their saliva.
A recent finding that Ixodidae persulcatus (adult and nymph bites) are more infectious than Ixodidae ricinus (adult only bites) may mean that GPs need a lower threshold for antibiotic prophylaxis - particularly in high incidence areas, with multiple bites, or if a tick has been feeding for more than 24 hours.
Prompt removal with blunt or curved forceps applied to the sides of the tick's head as close to the skin as possible and steady traction (not twisting) is most effective. Application of antiseptic before and after may reduce infection risk. Applying chemicals to ticks may increase salivation and infection.
Ticks secrete anticoagulant, analgesic and anti-inflammatory agents, so only 40 per cent of patients recall a bite.
Like other spirochaete diseases (syphilis and leptospirosis), there are three stages; early (stage 1), medium (stage 2) or late manifestations (stage 3). These stages may overlap.
The pathognomonic erythema chronicum migrans rash is only present in 32 per cent of patients.1 The non-pruritic, spreading erythematous rash sometimes has a central clearing (bullseye) and appears days or weeks after a bite.
Acute symptoms include: myalgia, arthralgia, lethargy, fatigue, headache, stiff neck, fever, lymphadenopathy and hepatomegaly. Treated or not these symptoms resolve in three to four weeks. Rashes may recur.
These acute symptoms are common meaning Lyme disease is underdiagnosed. Prompt treatment would prevent medium and late symptoms occurring.
Medium-stage Lyme disease is a multi-organ disease; 60 per cent get a brief arthritis. Hepatitis, hepatomegaly, dry cough, testicular swelling, or secondary erythema chronicum migrans can occur.
Ophthalmic presentations include conjunctivitis, choroiditis, or iridocyclitis and even optic neuropathy with papilloedema. Cardiac involvement causes pericarditis or a myocarditis.
B burgdorferi crosses the blood-brain barrier eliciting an inflammatory response with various neurological symptoms. Local bite pain may evolve into myalgia or arthralgia then migrate to a specific derma-tome or peripheral nerve distribution.
This radicular neuritis (Bannwarth's syndrome, meningopolyneuritis) may mimic disc herniation, sciatica, herpetic neuralgia, diabetic neuropathy or polymyalgia rheumatica. It is poorly responsive to analgesia and worse at night.
A cranial neuritis, often confused with Bell's palsy, is a common presentation. Other cranial nerve palsies can occur.
Lyme disease can cause vertigo; meningeal symptoms, headache and central sleep apnoea.
Months or years later, dilated cardiomyopathy or erosive arthropathy can occur. Acrodermatitis chronica atrophicans is a dermatosis secondary to damage to sympathetic nerves.
There may be sympathetic reflex dystrophy, dermatomyositis, and late neuroborreliosis (for example, chronic progressive encephalitis or encephalomyelitis).
Differential diagnoses include other multifocal CNS diseases, such as MS, systemic lupus erythematosus, sarcoid, Behcet's, polyarteritis nodosa, syphilis and Hughes syndrome.
Early diagnostic tests for Lyme disease are unreliable; serum IgM peaks at three to six weeks and IgG may not appear for months or years. Many subspecies of B burgdorferi mean serology tests are too specific. Nucleic acid amplification techniques may improve diagnosis.
CSF examination is essential if neuroborreliosis is suspected. In Sweden, where cases had doubled in five years, 17 per cent of CSF samples were positive even when serology was negative.3
One study found positive serology in children with other neurological problems.4
Penicillin is effective for erythema migrans, and associated meningitis and acrodermatitis chronica atrophicans.
Oral doxycycline for two weeks is effective for acute Lyme disease, and as effective as IV ceftriaxone for neuroborreliosis but is contraindicated in children.5,6 Severe cardiac ocular and neurological symptoms need IV treatment.
In adults a treatment delay of more than six weeks, female sex, and high CSF cell count are poor prognostic indicators.6
Prognosis was good in Swedish children reviewed at six months.7 Their residual sequelae (11 per cent) were cosmetic and functional relating to facial palsy.7
Some patients with a history of Lyme disease complain of persistent pain, fatigue, memory and concentration problems and need long-term symptomatic support from their GPs. Several patient support groups exist.
|Areas of Lyme disease prevalence1,2|
1. HPA Lyme Disease 26.05.09 www.hpa.org.uk
3. Henningson AJ, Malmvall BE, Ernerudh J et al. Neuroborreliosis - an epidemiological,clinical and healthcare cost study from an endemic area in the south-east of Sweden. Clin Microbiol Infect 2009; epub ahead of print.
4. Bennet R, Lindgren V, Zweygberg Wirgart B. Borrelia antibodies in children evaluated for Lyme neuroborreliosis. Infection 2008; 36; 463-6.
5. Ljostad U, Skogvoll E, Eikeland R, et al. Oral doxycycline versus intravenous ceftriaxone for European Lyme neuroborreliosis: a multicentre, non-inferiority, double-blind randomised trial. Lancet neurol 2008; 7: 690-5.
6. Ljostad U, Mygland A. Remaining complaints 1 year after treatment for acute Lyme Neuroborreliosis: frequency, pattern and risk factors. Eur J Neurol 2009; epub ahead of print.
7. Skogman BH, Croner S, Nordwall M et al. Lyme neuroborreliosis in children: a prospective study of clinical features, prognosis and outcome. Pediatr Infect Dis J 2008; 12: 1089-94.