Lice, Ticks and Lyme disease Flashcards
Where do ticks occur ie their geographical location?
- Distribution of I. ricinus in GBm as recorded by the PHE tick recording scheme and the biologicla records centre
Why do ticks act as a vector for human disease?
small organisms such as mosquitoes or ticks that can carry pathogens from animal to person or person to person
Ticks can also cause zoonotic diseases (Zoonoses) what is this?
An infectious disease that can be passed between animals and man
Tell me about Lyme disease
- most common human tick-borne disease in the Northern hemisphere
When was lyme diseases first identified?
Lyme, connecticut, 1970s
Reported cases of lyme disease in the US in 2014
What is the causative agent of Lyme disease?
Borrelia spp. spriochaetes
What are the lyme disease species which are known to be pathogenic to humans?
B. burgdorferi sensu stricto: USA, Europe
B. afzelii: Europe, Asia
B. garinii: Europe, Asia
B. spielmanii: Europe
B. bavariensis: Europe
B. mayonii: USA 2015
What species of lyme disease is pathogenicity yet to be proved for?
B. valaisiana
B. lusitania
In the UK, what three species cause lyme disease and rank them in order
B. garinii > B. afzelii > B. burgdorferi s.s.
Lyme borreliosis transmission cycle
generally transmitted by bites of ticks
larvae generally do not cause infection
larvae feed on small organisms and can acquire infection at that stage where it then becomes a nymph
this continues up its development to the adult form
What is the external anatomy of Borrelia spirochaete?
And what are some important proteins?
OspA and OspC get turned on/off depending on where the pathogen is
P17 is an ECM protein in many tissues in the body, in particular the joints
P83 protein
P66 protein
VIsE protein
Tell me about the pathogen transmission for the outer surface protein for ticks
Tick feeds for at least 12-17 hours – this causes a change in Osp expression
OspC needed to transmit Borrelia to mammalian host, inhibits phagocytosis - OspC binds to tick salivary gland epithelial cells so facilitates infection as more present on saliva
What are the main three stages of lyme disease
- Early lyme disease
- Early disseminated lyme disease
- Late disseminated lyme disease
Tell me about what happens in early lyme disease and the symptoms
Local infectio: Days to weeks after tick bite
Flu-like symptoms: fever, malaise, myalgias, headaches (1-7d)
Erythema migrans rash (EM) expands around bite site (>7 days)
‘classical’ bulls eye rash
not present in 30-50% cases
Many asymptomatic
Tell me about early disseminated lyme disease, what occurs and the symptoms
Disseminated infection
Weeks to months after infection
Through blood or lymphatics
bacteraemia often very low
Multiple secondary Erythema Migrans lesions
Lymphocytoma (esp. children)
Earlobes, nipples, genital area
Neuroborreliosis
Facial / cranial palsy
e.g. Bell‘s palsy
Polyarthralgia or true arthritis
Tell me about Late disseminated lyme disease, when it occurs and the symptoms
persistent symptoms- serious as often not obviously related to ticks
Months to years after infection
late Neuroborreliosis
more widespread PNS and CNS involvement; MS-like; encephalopathy; cognitive problems; psychiatric problems
Lyme arthritis
inflammatory ahrthritis; especially knee joints
Lyme Carditis
conduction abnormalities; atrioventricular block
Acrodermatitis chronica atrophicans (ACA)
What are the different borrelia species which alter disease?
rank them as well
Borrelia garinii
- No rash in ~30%
- Neurotropic
Borrelia afzelii
- Dermatotropic; esp. ACA
- Neurotropic
Borrelia burgdorferi s.s.
- Musculoskeletal; esp. arthritis
- => In USA, B. burgdorferi s.s. predominates, most common late symptom is Lyme arthritis
- => In Europe, B. garinii and B. azelii predominate, neurological complications
B. garinii > B. afzelii > B. burgdorferi s.s
regional variations in genosepcies distribution
What are the treatment options for those with lyme disease?
If treated promptly and adequately, Lyme disease rarely progresses beyond the early, acute stage.
Treat Erythema Migrans empirically (laboratory diagnosis not required) but asymptomatic or flu like presentations may be missed
Oral antibiotics usually adequate for:
- Early lyme
- Lyme arthritis
- Lymphocytoma
Lyme carditis and neuroborreliosis need intravenous antibiotics
How is lyme disease diagnosed, what three ways and tell me abit about each one?
Clinical diagnosis sufficient for cases of early Lyme presenting with an EM rash
Laboratory diagnosis:
- Serology is mainstay: but needs confirmatory assay
- PCR of blood/serum of limited use (low bacteraemia)
- PCR of Erythema Migrans biopsy or ACA lesion
- Culture of pathogen is gold-standard, but Borrelia is slow-growing
Alternative tests
- Lymphocyte transformation tests / EliSpots
Tell me about serology tests at PHE
What does the Ab repertoire increase with?
disease progression
What are some limitations towards lyme disease?
Antibody response slow to develop, false negatives possible in early disease.
IgM appear 2-3 weeks after onset (may persist for months/years)
IgG produced several weeks to months after onset
Antibiotics can suppress antibody development
Known cross reactions:
other spirochaetes
other bacteria with flagella
acute EBV cause polyclonal stimulation of Borrelia antibodies
autoimmune diseases
In late-presenting Lyme, positive serology test does not prove current infection. How to diagnose late Lyme?
What is the true incidence of Lyme disease?
UK figures are based on laboratory confirmed LD infections
Cases presenting to GPs with EM rash are not centrally recorded
Lyme is not a notifiable disease in UK
–> Figures will be an underestimate of true incidence of LD.
In USA, Lyme is a notifiable disease
Published figures still believed to be an underestimate
30,000 cases => 300,000 cases
There is a controversy, that nearly every area of lyme disease knowledge attracts disagreement between medical professions and patients. Give some examples of some disagreements
- Cause of persisting symptoms
- Incidence and prevalence in the UK
- Modes of transmission
- Diagnostic criteria and methodologies
- Antibiotic treatment duration
- Role of complementary therapies
- Role of co-infections
- Is there chronic Lyme disease?
Chronic lyme, post treatment lyme disease?
No consistent, agreed definition of ‘Chronic Lyme’
Persistent, untreated active infection e.g., late neuroborreliosis; ACA
Persistent symptoms following treatment for Lyme boreliosis
Post-Lyme disease treatment syndrome (PTLDS)
Patients who have had Lyme disease in past but current
presentation may be unrelated to Borrelia infection
Patients with non-specific symptoms but no evidence of current or past borrelial infection
What is the quest for ‘chronic lyme’?
Is this chronic Lyme?
patient with non-specific symptoms (fatigue, pain, muscle, or joint pain, ‘brain fog’ etc)
no credible clinical history
negative conventional diagnostic tests
