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manifestations and supportive
serological or molecular testing . This can be straightforward in Lyme disease with classical manifestations and likely exposure to ticks in the US or Europe , but in those without erythema migrans and where a history of tick exposure is not evident , the diagnosis may be difficult .
This How to Treat covers why Lyme disease is only seen in Australia in returned travellers . It also covers how to diagnose and manage not only Lyme disease but other infections with similar presentations . It aims to ensure patients are not overtreated for an infection that is not present in
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National Institute of Allergy and Infectious Diseases / bit . ly / 3ChFyUe |
early disseminated disease and late disease ( see table 1 ).
Early localised disease usually manifests within 3-30 days following the tick bite . Erythema migrans — a red rash usually with a central clearing ( bulls-eye appearance ) — is the hallmark of Lyme disease . However , up to 30 % of infected people may not develop this rash . 15 The rash appears at the site of the bite — initially , as a red papule or macule — and slowly expands to reach between 5cm ; it may even reach 30cm or larger in diameter . The rash may be warm , itchy or sensitive to touch , although it is usually asymptomatic and generally dis-
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Australia and that other appropriate |
appears spontaneously within 3-4 |
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possibilities are considered in the dif- |
weeks . Other signs and symptoms of |
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ferential diagnosis . |
early localised Lyme disease include |
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EPIDEMIOLOGY
IXODES sp . ticks are primarily found
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fever , chills , fatigue , myalgias , arthralgias and lymphadenopathy .
Early disseminated disease occurs
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in temperate regions of the North- |
days to weeks following transmission |
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ern Hemisphere , including parts of |
of B . burgdorferi sl , with multiple ery- |
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Europe , the upper Midwestern and |
thema migrans lesions the most com- |
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north-eastern parts of the US , as well |
mon manifestation . These secondary |
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as parts of Asia , including China and |
skin lesions develop , on average , |
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Japan . The prevalence of Ixodes sp . |
3-5 weeks post-bite and are simi- |
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ticks and B . burgdorferi sl infection is |
lar to the primary erythema migrans |
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reliant on the presence of natural ani- |
lesion , although they are multiple and |
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mal hosts in these regions . However , |
smaller . Other organs may be affected |
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there are many other factors influenc- |
in disseminated disease which can |
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ing Ixodes sp . populations , including |
result in cranial nerve palsies , menin- |
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seasonality and rainfall . 2 |
gitis and carditis . |
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Surveillance studies of ticks in Aus- |
Late disease manifests in the weeks |
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tralia have not detected any organisms from the B . burgdorferi sl complex . While some Ixodes sp . ticks are found in Australia , none of the spe- |
Figure 2 . Lyme disease ( B . burgdorferi ). |
to months following untreated B . burgdorferi sl infection . The most common manifestation of late disease is arthritis . Lyme arthritis is often a large joint |
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cies known to carry organisms of the B . burgdorferi sl complex have been found in Australia . 3 , 4 This — coupled with a lack of convincing human cases with erythema migrans — has led to the general consensus that there is no locally acquired classic Lyme disease in Australia . 5 Similarly , there is no evidence of Ixodes sp . tick or B . burgdor- |
Table 1 . Stages and clinical features of Lyme disease
Stage of infection
Clinical features
Early localised ( onset 3-30 days ) Erythema migrans ( see figures 3 , 4 and 5 ) Fever and chills Lymphadenopathy Lethargy Myalgias Arthralgias
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subsequent reduction in Lyme disease cases was observed . 12 However , there is a growing body of evidence suggesting that the density of other small mammals , such as the white-footed mouse , is an important determinant for the density of infected Ixodes sp . ticks . 13 This suggests that the incidence and risk of Lyme disease are |
monoarthritis , but it can also present with oligoarthritis . Symptoms are similar to typical septic arthritis , with a swollen and warm joint , but the pain is often milder . Neurological manifestations include encephalitis and polyneuropathy , but these are much rarer in children .
Clinical presentations may also
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feri sl complex in New Zealand . 6
While there is no classic Lyme disease in Australia , there are several locally acquired tick-borne illnesses that have some overlap in clinical manifestations ( fever and rash ) but are caused by very different bacteria . Australian Tick typhus , caused by Rickettsia australis , can be found along the eastern coast of Australia ( North Queensland to Victoria ); Flinders Island spotted fever , caused by Rickettsia honei , is found in south-eastern Australia ( Victoria , Tasmania and
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Early disseminated ( onset days to weeks )
north-eastern US ), Ixodes pacificus ( found on the west coast of the US );
Multiple erythema migrans Fever Headache Myalgias Arthralgias Neurological : cranial nerve palsies , meningitis
Late ( onset weeks to months ) Arthritis ( see figure 6 ) Encephalitis Polyneuropathy Acrodermatitis chronica atrophicans
The rate of B . burgdorferi sl infection in Ixodes sp . ticks is thought to be
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dependent on many variables and that an understanding of the Ixodes sp . life cycle and variety of animal hosts is important in the mitigation of risk of infection to humans .
PATHOGENESIS
B . BURGDORFERI sl is an obligate parasitic bacterium that cannot survive as a free-living organism in the environment . As it infects the intestine of the Ixodes sp . tick , transmission occurs during attachment of the tick to the human or animal host . It is more likely
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vary depending on the causative genospecies . Early localised Lyme disease can occur in all three genospecies . B . burgdorferi ss is most commonly associated with the manifestations of early disseminated and late disease . B . afzelii , however , is associated with acrodermatitis chronica atrophicans : the most common skin manifestation of late Lyme disease . 16
LYME DISEASE – LIKE ILLNESS
LYME disease – like illness is a term
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Flinders Island ); and Scrub typhus , |
Ixodes ricinus and Ixodes persulcatus |
highly variable , with one study find- |
to be transmitted if the tick is attached |
used to describe the unexplained |
caused by Orientia tsutsugamushi , is found in northern Australia . 7 Q fever ( Coxiella burnetti ) may be transmitted by various modes , including by tick |
( found in Europe and Asia ).
Ixodes sp . ticks have four stages in their life cycle : egg , larva , nymph and adult . The ticks can acquire a B . burg-
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ing between 8.3 % and 34.2 % of ticks in Northern Germany infected with B . burgdorferi sl . 9 Tick infection rates are at their highest when they are in abun- |
for a longer period , particularly more than 72 hours . 10
B . burgdorferi sl can invade many different tissues in susceptible hosts .
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constellation of symptoms that are experienced most commonly following a tick bite in the absence of travel to a region known to have ticks |
bites , and is found predominantly in |
dorferi sl infection during a blood meal |
dance in the summer months . Infec- |
In early disease , B . burgdorferi sl repli- |
infected with B . burgdorferi sl . Symp- |
eastern Australia . |
from an infected animal . The bacteria |
tion rates are also known to increase |
cates in the dermis at the site of the tick |
toms are often chronic and include |
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AETIOLOGY
B . BURGDORFERI sl complex that
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infect the intestines of the Ixodes sp . tick . This may occur at any stage in the tick ’ s life cycle after it hatches from the |
with each developmental stage , meaning the more mature a tick is , the more likely it is to transmit B . burgdorferi |
bite , causing the classical skin changes of erythema migrans : an expanding circular , target-like rash . If the condi- |
headaches , fatigue , arthralgia , disordered thinking and sensory disturbance . The term ‘ debilitating |
cause Lyme disease in humans are |
egg , although the further along in the |
sl . This risk of transmission is high- |
tion is not treated , the organism may |
symptom complexes attributed to |
helical shaped spirochaetes ( see fig- |
life cycle the tick is , the more likely it |
est from the bite of an adult Ixodes sp . |
then gain access to the lymphatic or |
ticks ’ ( DSCATT ) was designed by |
ure 2 ). There are three main genospe- |
is to become infected with B . burgdor- |
tick that has been attached for a longer |
blood vessels and disseminate , causing |
the Department of Health and Aged |
cies within this complex that cause |
feri sl . Once infected , the tick may then |
duration ( longer than 72 hours ) with a |
a wide range of clinical manifestations . |
Care as an construct to represent the |
the conditions : B . burgdorferi sensu stricto ( ss ) in North America and B . garinii and B . afezelli in Europe and Asia . These organisms have a natural reservoir in Ixodes sp . ticks , small |
transmit B . burgdorferi sl to the next animal ( or human ) to which it attaches .
Risk factors
The risks of developing Lyme disease
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larger degree of engorgement . 10
There is an association between Lyme disease and the prevalence of the natural animal hosts of Ixodes sp . ticks . In north-eastern US , the link
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B . burgdorferi sl has several mechanisms that allow immune evasion , including surface proteins that interfere with complement-mediated killing , antigenic variation and production of |
patient groups with chronic debilitating illnesses that many associate with a tick bite . DSCATT is not a diagnosis but is used to describe patients with ongoing symptoms once all other |
mammals , birds and deer , but humans are a dead-end host . Consequently , B . burgdorferi sl cannot be transmitted person to person , and there is no evi- |
are highly dependent on exposure to vector-competent ticks ( that is , Ixodes sp .) and visiting countries where Lyme disease is present . Ixodes sp . ticks are |
between the incidence of Lyme disease and the density of I . scapularis ticks and white-tailed deer is well documented . Interestingly , the adult |
proteases that allow dissemination and chronic infection . 14 Tissue pathology is generally a result of the inflammatory response by the immune system . |
possible causes have been excluded . 17
DIAGNOSIS
THE diagnosis of early Lyme dis-
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dence of vertical transmission during pregnancy . 8
The four main species of ticks that are vectors for B . burgdorferi sl include Ixodes scapularis ( found in
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found in heavily wooded and grassy areas , where they perch on the ends of grass or low-hanging branches waiting to attach to and feed on passing animals . |
I . scapularis , which is more likely to be infected with B . burgdorferi sl than younger ticks , feeds primarily on white-tailed deer . 11 In areas where the density of deer was reduced , a |
SIGNS AND SYMPTOMS
LYME disease can be classified into
three stages : early localised disease ,
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ease can be made clinically in a patient with a history of tick bite from an endemic region , followed by the appearance of typical or multiple erythema migrans . Tick PAGE 26 |