Travel makes tick diseases tougher to diagnose, paper finds
Climate change and increased travel are leading to significant diagnostic challenges and shifting epidemiology.
After being battered by the COVID crisis, international travel should be back up to its pre-pandemic levels by the end of 2024, according to the UN Tourism organization. While that’s good news for the travel industry, it could make the work of diagnosing tick-borne diseases harder. Add in the spread of ticks into new areas as the climate changes and the challenge is even greater.
John Kelly and Oliver Koch, two researchers at Western General Hospital in Edinburgh, illustrated the problem with a study of a widely-travelled 74-year-old man. The patient came to a hospital there with a four-day history of fever, muscle pain, chills, and tiredness.
He had recently returned from a fishing trip in Frontenac Provincial Park in Eastern Ontario, but after checking his symptoms, doctors could find no clear sign of infection. He had no headaches, joint pain, rashes, or swollen lymph nodes. A neurological exam to evaluate his brain and nervous system functions was normal. A test for respiratory viruses was negative.
The only concerning signs were low white blood cells and platelets, mild liver and kidney issues, and high level of CRP, a liver protein that increases when inflammation is present.
Citation
Kelly, J., & Koch, O. (2023). Human granulocytic anaplasmosis in a Scottish traveller returning from Canada. Travel Medicine and Infectious Disease, 56, 102675. https://doi.org/10.1016/j.tmaid.2023.102675
The man mentioned he had been bitten by an insect during the fishing trip but did not notice any tick bites. To complicate matters, he had traveled to Australia three months earlier. Then just three weeks before admission to hospital, he was on holiday in Argyll, Scotland where he went walking outdoors. While there, he had noticed some tick bites but didn’t immediately develop any rash.
Medical staff tested for several potential infections including hepatitis, toxoplasma, and leptospirosis. All were negative. Then, after four days in the hospital, the man felt better and was discharged.
The next day, he noticed a rash on his elbow and was treated with doxycycline for suspected Lyme disease. It was only after further testing that they finally found the real culprit: another tick-borne disease called anaplasmosis.
Anaplasmosis is caused by a bacteria called Anaplasma phagocytophilum, which attacks white blood cells. It’s a tick-borne disease that’s most common in North America but also seen in Europe. The researchers say the patient’s travel history suggests he likely got infected in Canada.
Anaplasmosis can be treated with doxycycline, but serious cases can lead to severe illness and organ failure, especially in older people or those who are treated late.
Kelly and Koch say the case highlights the importance of a detailed travel history when diagnosing patients, as well as the need for doctors to be aware of how tick-borne diseases are spreading.