Traveling Ticks: Tickborne Illnesses and International Travel

Traveling Ticks are more than just ticking off a checklist before you get ready to travel! Climate change and changes in land usage have contributed to an expanded range of ticks (Beard 2016). There are species of ticks found on every continent and carrying a variety of vectors capable of infecting humans. Globally, ticks are the second most common vector to transmit illnesses after mosquitos (Parola 2018). We frequently ask children and their parents if they have had recent tick bites when they present for fever after a recent camping activity. However, it is often overlooked that tickborne illnesses are among the most common travel-related illnesses globally (CDC Traveller’s Health 2017). We have previously talked about two of the most common tick related illnesses in the US: Lyme and Rocky Mountain Spotted Fever.  Outside the US most tick-borne illnesses are mainly attributed to a few viruses and bacteria. (Jensenius 2004) Let’s take a moment to review Tickborne Illnesses and International Travel:

Tickborne Illnesses and Major Rickettsial Diseases: Basics

• Most of these illnesses are acquired from exposure to a rural area during travels including camping, hiking, safaris, and livestock. (CDC 2024)
• Generally, most ticks require >24 hours of attachment for there to be a risk of transfer of the infectious agent.
  • This is true of hard ticks, which carry the majority of bacteria and viruses which can infect humans (Rochlin 2020)
  • This is not true when the infectious agent is carried by a soft tick. They feed for shorter times, usually only a few hours, but can still cause illness. 
• In general many of the symptoms between these illnessess are similar and include fevers, headaches, rashes, and myalgias. (CDC 2022)
• Testing for many of these illnessess can take time during the acute phase as many are ELISA or PCR tests. Given that early treatment prevents complication and prolonged course it is generally advisable to treat prophylatically when you suspect a tick-borne or rickettsial illness. (Jensenius 2004)

Most common Tick-Borne Illnesses in International travel: 

(CDC Yellow Book 2024)

African tick-bite fever

• Causative Agent: Rickettsia africae, a member of the spotted fever family (Silva-Ramos 2021)
• Incubation period is 5-7 days (Frean 2019)
• Second most common cause of fever in travellers returning from Sub-Saharran Africa aftermalaria (Silva-Ramos 2021)
• More than 80% of recorded cases occur in European travellers especially those engaged in wildlife activities including hunting, hiking and safari. (Silva-Ramos 2021)
• Majority of cases arise from travel to South Africa.  (Frean 2019)
• The classic triad described is fever, eschar and rash. (Silva-Ramos 2021)
  • Fever and a characteristic eschar (tache noir) are seen 90% of the time. The eschar can be seen in multiples up to 50% of the time. 
  • The maculopapular rash is actually seen less than half of the time. 
• Additional symptoms can include headache, regional lymphadenopathy, myalgais, maculopapular rash, chills, and arthralgias. (Silva-Ramos 2021)
• Laboratory evaluation can show elevated LFT’s and CRP nearly 50% of the time. Leukopenia and thromboytopenia were occasionally seen. (Silva-Ramos 2021)
• Complications occur in less than 5% of cases and include pupuric cellulitis, neurologic syndrome, and myocarditis. (Silva-Ramos 2021)
• Treatment: doxycycline (Frean 2019)

Mediterranean spotted fever 

• Causative Agent: Rickettsia conorii, a member of the spotted fever family (Spernovasilis 2021)
• As this tick is carried by dogs, most travellers will report exposure to a dog. (Jensenius 2004)
• Mainly found in the Mediterrean area, however it has been rising in incidence in Africa, Middle East and India. (Rochlin 2020)
• Shares many of the same symptoms as African tick-bite fever.
• Incubation period is 5-7 days on average (Jensenius 2004) 
• The classic triad is also a fever, characteristic eschar (tache noir) and maculopapular rash. (Spernovasilis 2021)
• Additional symptoms in pedatrics include GI symptoms, local lymphadenopathy, hepatomegaly and splenomegaly.  (Spernovasilis 2021)
  • In adults they were shown to have higher rates of headache, arthralgias, and myalgias.
• Children seem to be less likely to experience severe presentaitons as compared to adults with comorbidities. (Spernovasilis 2021)
• Complications include neurological involvements, peripheral gangrene, and respiratory distress syndrome. In rare occurences patients can develop multiorgan failure. (Jensenius 2004) 
• Overall fatality rate is ~2%, but this is primarily adults and immunocompromised patients. (Jensenius 2004) 
• Treatment: doxycycline

Human granulocytic anaplasmosis 

• Causative Agent: Anaplasma phagocytophilum, a rickettsial bacteria (Sanchez 2016)
• Previously seen in the endemic regions of North America where lyme is common, it is now being seen more frequently in travelers to Europe and eastern Asia as well. (Rochlin 2020)
• Symptoms are nonspecific and typical of most rickettsial illnessess including fever, chills, headache, and myalgias. (Sanchez 2016)
• On labs leukopenia, thrombocytopenia, and mild elevations of liver function tests may also all be seen (Sanchez 2016)
• Treatment: doxycycline (Sanchez 2016)

Rocky Mountain spotted fever also called Brazilian spotted fever has been previously addressed in another PEM morsel. 

Other Rickettsial Disease of concern from non-tick vectors

(CDC Yellow Book 2024)

Murine Typhus

• Causative Agent: Rickettsia typhi and the principal vector is the Asiatic rat flea. Some individuals recall direct exposures to rats when travelling. (Jensenius 2004) 
• Murine typhus is widely distributed in tropical and subtropical environments, particularlly port cities. (Jensenius 2004)  
• Symtoms of marine typhus are very nonspecific including fever, constitutional symptoms and a difficult to visualize maculopapular rash. (Jensenius 2004)  
• Complications: aseptic meningitis, deafness, deep venous thrombosis (Jensenius 2004)
  • Complications are much less likely to occur in children
• Treatment: doxycycline

Scrub Typhus

• Causative Agent: Orientia tsutsugamushi (a member of the family Rickettsiaceae) and the principal vector is larval Leptotrombidium mites, also called chiggers. (Jensenius 2004)  
• Scrub typhus is one of the most common infectious disease in rural areas of south and southeastern Asia and the western Pacific. (Jensenius 2004)  
  • Scrub typhus had a significant impact on troops during World War II and the Vietnam War 
  • WHO reports that scrub typhus one of the world’s most underdiagnosed/underreported diseases that often requires hospitalization (Luce-Fedrow 2018)
• Symptoms of scrub typhus include an innoculation eschar, fever headache and lymphadenitis. (Jensenius 2004)  
• Complications: pneumonitis, acute respiratory distress syndrome (ARDS), myocarditis, septic shock, meningoencephalitis, pericarditis, and disseminated intravascular coagulation (Xu 2017)
  • Fatality can reach up to 70% if untreated depending on the strain. 
• Treatment: doxycycline

Non-Rickettsial tickborne illnesses which are also of particular concern:

(CDC Yellow Book 2024)

Tickborne Relapsing Fever

• Causative Agent: multiple species of Borrelia (Rochlin 2020)
• Worldwide, except for Australia! In the US, outbreaks have been linked to rental cabins near national parks. (CDC 2022)
• Divided into Soft tick relapsing fever and Hard tick relapsing fever, depending on what type of ticks carry the Borrelia sp (CDC 2022)
  • There is also a louse which carries a Borrelia sp. Capable of causing a relapsing fever. In this case it is called louse-borne relapsing fever.
• Soft ticks typically only latch for around an hour. Therefore this illness is an exception to the general rule that it takes > 24 hours of exposure for transmitting tickborne infections. 
• Symptoms include a relapsing, high fever (>103). Fever lasts for 3 days, followed by a 7 day afebrile period before experincing fever again. This cycle can repeat multiple times unless treated. (Rochlin 2020)
  • Additionally nonspecific symptoms of chills, headache, and myalgias and arthragias.
• Complications are rare but can include iritis, uveitis, cranial nerve and other neuropathies (CDC 2022)
• Diagnosis is usually confirmed on peripheral blood smear which will identify the spirochetes. (CDC 2022)
• Treatment: doxycycline (CDC 2022)

Tickborne Illness and Encephalitis

• There are 2 main causes of viral encephalitis from tickborne illnesses (Rochlin 2020)
  • Tick-Borne Encephalitis which is an increasing cause of viral-associated fevers in eastern, central, northern and increasingly western European countries, and in northern China, Mongolia, and the Russian Federation. 
  • Powssan Encephalitis which is overall much more rare and primarily seen in North American and parts of Russia.
• Time from tick bite to onset of symptoms generally ranges from 1 week to 4 weeks but can start within 2 days (CDC 2022)
• Tick-Borne Encephalitis can also be transmitted in unpasturized dairy. (Ricardi 2019)
• Tick-Borne Encephalitis has a biphasic pattern of symptoms. (Ricardi 2019)
  • Initial symptoms are nonspecific and include fever, malaise, headache, nausea, vomting and myalgias. These resolve within 1 week. Most patients do not have further progression, however 15% will develop more severe illness after a quiescent period of 1-20 days. In pediatrics, the more severe illness will often be characterized by signs of aseptic meningitis, but could also have symptoms of meningoencephalitis, acute flaccid parlaysis or a Guillan-Barre-like progression of paralysis.  
  • Mortality rate can be up to 20% of those who progress to the second phase depending on the exact viral strain. 
• Powssan Encephalitis is similar in presentations and mortality but without the biphasic pattern of symptoms. (Menoza 2024)
• For those that develop encephalitis neurologic sequalae has been reported up to 50-70% of cases. (Menoza 2024)
• Diagnosis depends on high clinical suspicion as well as testing of both serum and CSF. (Ricardi 2019)
• There is no notable treatment for these viruses and patients are primarily managed through supportive care. (Ricardi 2019)
  • There are 4 widely used vaccines in regions with endemic Tick-Borne Encephalitis which have decreased incidence of infections locally. (CDC 2022)

Tickborne Illness and Hemorrhagic Fevers

• Uncommon but notable occurrecnces are Tickborne illnesses which result in hemorrhagic fevers 
  • Crimean-Congo hemorrhagic fever
  • Omsk hemorrhagic fever
  • Kyasanur Forest disease
• Between all of these the distribution is relatively widespread, the most common of them being Crimean-Congo hemorrhagic fever which is found in Europe, Central Asia, India, Africa. (Rochlin 2020) 
• Crimean-Congo hemorrhagic fever (WHO 2022)
  • Causative Agent: Bunyaviridae virusIncubation period : 5-6 days on averageSymptoms start with fever, myalgias, headache and photophobia. There are usually GI symptoms in addition with associated abdominal pain. Petechial rash may develop including mucosal surfaces and often progressess to ecchymosis.Mortality rate is 30-40% and typically in the 2nd week of illness.
  • Treatment: Supportive care
• Omsk hemorrhagic fever/Kyasanur Forest disease (CDC 2013)
  • Causative Agent: Flavivirus
  • Incubation period : 3-8 days
  • Symptoms start with chills, fevers, headache and GI symptoms followed by symptoms of bleeding 3-4 days later including petechial rash, low hemoglobin and low WBC. 
  • Most recover in 1-2 weeks, however a second wave of symptoms does occur in some including fever and signs of neurologic involvement or encephalitis. 
  • Mortality rate is 3-5% for Kyasanur Forest disease and 0.5-3% for Omsk hemorrhagic fever
  • Treatment: Supportive care

Moral of the Morsel:

• Ticks are on the move! Climate changes and altered land use has expanded endemic regions for Tickborne Infections and other Rickettsial illnessess. 
• Remember the 3 T’s of Global Health: Travelling, Tourists and TICKS! When addressing a patient who presents for illness after recent travel always make sure to ask about tick bites, exposures, and any eschars!
• When in doubt, treat! Due to difficulty obtaining specific labs for identification of many of these illnesses, general guidelines are for emperic treament typically with doxycycline. Unless it is viral mediated, in which the treatment is supportive care. 

Thanks for checking out my Tick-Talk!

References

Beard, C.B., R.J. Eisen, C.M. Barker, J.F. Garofalo, M. Hahn, M. Hayden, A.J. Monaghan, N.H. Ogden, and P.J. Schramm. 2016. Chapter 5: Vector-borne diseases. The impacts of climate change on human health in the United States: A scientific assessment. U.S. Global Change Research Program.

CDC. Kyasanur Forest Disease (KFD). 2013. https://www.cdc.gov/vhf/kyasanur/treatment/index.html

CDC. Omsk Hemorrhagic Fever. 2013. https://www.cdc.gov/vhf/omsk/symptoms/index.html

CDC. Tickborne Disease Abroad. 2022. https://www.cdc.gov/ticks/tickbornediseases/abroad.html

CDC. Tick- and Louse-Borne Relapsing Fever. https://www.cdc.gov/relapsing-fever/index.html

CDC Traveler’s health. Diseases Spread by Ticks. 2017. https://wwwnc.cdc.gov/travel/page/diseases-spread-by-ticks

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Nicholson, W and Paddock, C. Rickettsial Disease. CDC Yellow Book 2024: Health Information for International Travel. https://wwwnc.cdc.gov/travel/yellowbook/2024/infections-diseases/rickettsial-disease

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Riccardi N, Antonello RM, Luzzati R, Zajkowska J, Di Bella S, Giacobbe DR. Tick-borne encephalitis in Europe: a brief update on epidemiology, diagnosis, prevention, and treatment. Eur J Intern Med. 2019 Apr:62:1-6.  PMID: 30678880. 

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