Lyme borreliosis (Lyme disease)
Rodents and other mammals and birds are host animals for Borrelia bacteria. Transmission of infection to humans occurs through a vector. Vectors in Norway are sheep ticks (Ixodes ricinus) and seabird ticks (Ixodes uriae). The disease can manifest itself in different ways with a distinction between disease in parts of or the entire body.
Erythema migrans (EM) is a local, characteristic rash that may appear 3-30 days after a bite. In addition, there may be flu-like symptoms such as malaise, fatigue, headache and swollen lymph nodes without evidence of systemic infection. Fever is uncommon.
Lyme neuroborreliosis is the most commonly reported disorder in Norway and Europe. It can appear from two weeks to several months after the bite and commonly causes facial paralysis. Diagnosis and treatment is challenging and is constantly subject to discussion.
A Swedish study (Stingstudien) published in 2011 showed that the risk of becoming infected with Lyme disease after being bitten was low.
Most Lyme disease cases are reported among residents of Vestfold and south along the coast and up to Møre og Romsdal.
The figure below shows cases of Lyme disease reported to the Norwegian Surveillance System for Communicable Diseases (MSIS) in 2008-2016. The cases are distributed in the county where they live and where they are believed to have been infected. The disease can affect all age groups, including children.
|Figure 1 County of residence (bar) and site of infection (line) for reported cases of Lyme disease in Norway. Illustration: Norwegian Institute of Public Health.|
The most important preventive measure to avoid disease is to avoid being bitten. There is no vaccine against Lyme disease.
Diagnosis is usually carried out by detecting specific antibodies to Borrelia burgdorferi.
Detected antibodies can confirm infection, but can also be due to antibodies from previous infections or from earlier encounters with the microbe without symptoms. In certain disease states, it may also be necessary to analyse samples with PCR tests.
Most medical microbiological laboratories in Norway offer antibody detection for Borrelia infection. If the primary laboratories need to perform further tests they can contact their regional laboratory or the reference laboratory at Sørlandet Hospital in Kristiansand.
The Norwegian Institute of Public Health is sometimes asked by people who have been bitten by ticks if the tick can be examined for Borrelia infection. No laboratories in Norway perform these examination.
Phenoxymethylpenicillin, amoxicillin and doxycycline are considered to be equally good treatment for local disease / erythema migrans. Treatment duration is 14 days.
For acrodermatitis chronica atrophicans (ACA) and arthritis, three weeks of doxycycline treatment (amoxicillin for children under 8 years) is recommended. For suspected neuroborreliosis or heart borreliosis, parenteral antibiotic therapy is usually recommended and a neurologist or cardiologist should be consulted. The treatment is effective, but fails in a few cases.
Routine antibiotic treatment after tick bites is not recommended, but if a patient develops a fever, rash or sores near the bite within the first month, medical advice should be sought. Local irritation and wound infection should not be confused with erythema migrans (EM).
There is no vaccine against the Borrelia species present in Norway or other European countries.
Lyme disease is notifiable to the Norwegian Surveillance System for Communicable Diseases (MSIS). Only cases that meet the notification criteria should be reported.
Changes in notification criteria over the years make it difficult to compare today's figures with historical data. The differences in criteria between countries also cause problems when comparing national figures.