At long last, the summer months have arrived. You resurrect your shorts and your walking poles (if you are so inclined, or intend to be) and whitewash that pale face in preparation for those searing UV rays. The great outdoors await! However, if you are planning any grassland adventures this summer, it’s probably best you spare a thought, and some vigilance, for Lyme disease.
Lyme disease, or borreliosis, once confined to the wilds of the USA, is now a prevalent occurrence in Europe and Asia, and arises from tick-borne bacteria from the Borrelia genus (most commonly B. burgdorferi, B. afzelii and B. garinii species are involved). In Ireland, the risk of infection is especially high in geographical areas where humans, animal populations and ticks coalesce.
Historically, there has been a general lack of awareness of Lyme disease amongst the medical profession in Ireland (it was rarely seen here), but now doctors are being urged to get up to speed with the symptoms of infection and keep an open mind to the possibility of Lyme disease occurring in their community.
When viewed under the microscope, the bacteria have a corkscrew-like shape, with flagella enclosed between its outer and inner membranes, and the movement of these flagella give Borrelia its spiralling locomotion. As the flagella are enclosed, it is thought that this helps the bacteria to swim through viscous media (capable of arresting other bacterial types) and to avoid aspects of immune detection.
The genetic material of Borrelia contains a linear chromosome, and a large number of smaller linear and circular DNA. Gene expression varies greatly depending on the environment, allowing the bacteria to adapt to both mammalian and tick physiology, and also complicating the design of vaccines based on the protein products of these genes (Tilly et al. 2008).
Some studies report that the bacteria can generate a sugary biofilm which protects them from host defences and therapeutic interventions. Borrelia species could cross the blood brain barrier and may be capable of infecting neurons in the central nervous system (Smith et al. 2014). This, and the inflammatory response generated against the microbe, may aggravate the CNS and could account for the Lyme neuroborreliosis observed in patients who have gone untreated for prolonged periods.
One of the reasons that Lyme disease is often misdiagnosed is that the infection can generate symptoms which mimic several other conditions. These include flu-like symptoms, fatigue, headaches, fever and joint pain
Diagnosing the symptom mimic
One of the reasons that Lyme disease is often misdiagnosed is that the infection can generate symptoms which mimic several other conditions. These include flu-like symptoms, fatigue, headaches, fever and joint pain. If left untreated, infection can lead to neurological and cognitive abnormalities, musculoskeletal pain, and arthritis, all of which are more likely to be caused by other conditions. Added to this, patients may not remember being bitten by a tick a few weeks previously, or may not have developed the tell-tale bulls-eye rash (erythema migrans), and so it is perhaps understandable that the disease gets overlooked. Compounding the issue is the relatively low-tech diagnostic tools that are currently used for diagnosis of Borrelia infection. Serological tests measure the body’s antibody response to the bacteria, but antibody concentrations sufficient enough for measurement may not be present in early infection, and the tests do not distinguish between active and prior infection (Marques AR 2015). The tests are specific for B. burgdorferi, so they may not detect responses to other Borrelia species.
Don’t get ticked off
The good news is that once diagnosed in good time, infection is usually cleared by standard oral or intravenous antibiotics such as doxycycline, amoxicillin or cefuroxime. In a small percentage of cases, a patient’s symptoms of infection may linger for six months or more after treatment completion, and these cases are classed as having Post-treatment Lyme Disease Syndrome (PTLDS). It is not sure whether this arises from lingering infection, or residual damage associated with infection (www.cdc.gov). In any case, prevention of Lyme disease is the best cure, so covering exposed skin and wearing insect repellent while taking to the woodlands and parklands is a good way of preventing tick bites and possible infection.
- Tilly K et al. Biology of Infection with Borrelia burgdorferi. Infect Dis Clin North Am. 2008 June; 22(2): 217–234
- AJ Smith et al. Chronic Lyme Disease: Persistent Clinical Symptoms Related to Immune Evasion, Antibiotic Resistance and Various Defense Mechanisms of Borrelia burgdorferi. Open Journal of Medical Microbiology, 2014; 4, 252-260
- Marques AR. Laboratory Diagnosis of Lyme Disease – Advances and Challenges. Infect Dis Clin North Am. 2015 June; 29(2): 295–307