A new review of Lyme disease research assesses the potential reasons for the continued lack of success in prevention and control of Lyme disease and points to key areas where public policy could make all the difference.
Lyme disease is an infectious disease caused by a spirochete (spiral shaped bacterium) known as Borrelia burgdorferi and most commonly spread by ticks. Despite the infectious agent and mode of ptransmission being known for over three decades the cases of Lyme disease are continuing to climb. The highest rates are seen in the Northeastern United States but many people from different regions and countries also suffer from the disease.
The most obvious sign of initial Lyme disease infection is a chracteristic rash around a tick bite known as Erythema migrans, or a "bullseye" rash, so named because it is circular and red around the outside with a pale centre. Symptoms of the disease are multiple, ranging from fatigue, weakness and headache, to cognitive, mood, and neurological disorders. The large number and systemic nature of symptoms has contributed to controversy. Some experts say Lyme disease is acute and easily treated with a relatively short course of antibiotics, while others suggest a chronic form may develop. Certainly there are no shortage of individuals who suffer chronic symptoms following Lyme infection - which makes this latest study of prevention all the more important.
In the article appearing in the January issue of the Journal of Medical Entomology titled "What Do We Need to Know About Disease Ecology to Prevent Lyme Disease in the Northeastern United States?" authors from Colorado State University and the Centers for Disease Control and Prevention (CDC) assess the potential reasons for the continued lack of success in prevention and control of Lyme disease in the northeastern United States, and they identify conceptual areas where additional knowledge could be used to improve Lyme disease prevention and control strategies.
Important areas highlighted by the investigators include: 1) identifying critical tick infestation rates required to maintain transmission of B. burgdorferi, 2) understanding how habitat diversity and forest fragmentation impacts the risk of exposure to B. burgdorferi and the ability of interventions to reduce risk, 3) quantifying the epidemiological outcomes of interventions focusing on ticks or vertebrate reservoirs (most notably deer), and 4) refining knowledge of how human behaviour influences Lyme disease risk and identifying barriers to the adoption of personal protective measures and environmental tick management.
Clearly some of these areas are more open to human intervention than others. Greater understanding of how forests and other habitats influence Lyme disease risk may lead to government agencies in at risk countries implementing management strategies that favour a reduction in Lyme disease and other tick-borne infections.
Much of the risk lies however in the behaviour of individuals and this is an area that the study authors chose to focus on in some depth.
They report that the most promoted method of Lyme infection prevention is the use of repellent sprays on clothing and/or exposed skin. Data on how effective repellents are is limited however and there is the issue of how safe these chemicals are with many based on insecticides like DEET. This chemical has is neurotoxic to humans as well as ticks and it's use in repellents has been associated with insomnia, mood disturbances, impaired cognitive function and even seizures. Specialised clothing is now available which is pre-treated with the insecticide permethrin. This may be a safer choice as it avoids liberal spraying of toxic chemicals on oneself, the fumes of which are easily inhaled.
The authors highlight research suggesting that one of the most effective methods of personal Lyme prevention is to wear clothing that is well sealed and leaves as little bare skin as possible - and to remove this clothing quickly and take a bath within two hours of returning from a forest or other area known to be a high risk for tick-borne infection. Of course checking your entire body for ticks should also be included in this strategy.
Perhaps not surprisingly the scientists found that despite efforts to warn the public of the potential for contracting Lyme disease in high risk areas and providing prevention advice - the percentage of people heeding the warnings remains relatively low. Studies of human behaviour suggest this is likely due to a perceived risk that is lower than the actual risk. It is therefore important that the message that Lyme disease is a serious health concern and increasingly common is communicated to the public, along with the best prevention strategies based on the latest research.
Source: Eisen RJ Piesman J Zielinski-Gutierrez E Eisen L (2012) What Do We Need to Know About Disease Ecology to Prevent Lyme Disease in the Northeastern United States? Journal of Medical Entomology 49(1):11-22