Life After Lyme Disease

May is officially Lyme disease awareness month and this is one of the key times of year when cases of this condition rise, as ticks start feeding voraciously in preparation for the breeding period.  Lyme disease is now one of the most prevalent insect-borne diseases in the Northern Hemisphere, and is passed to humans through the bites of infected ticks.  Although all species of ticks can pass on diseases scientist have identified the genus Ixodes as being the prime carriers of the bacteria which causes Lyme disease, Borrelia burgdorferi.  These ticks are common throughout many parts of the United States and key habitats include woodland and wild land edges, where they can find an abundance of their main prey, deer and small rodents.  Ticks will also feed on any domestic pets and humans they come into contact with, and because they are so small they can be difficult to detect.

Identifying Lyme Disease

In the majority of cases Lyme disease manifests a characteristic circular skin rash known as erythema migrans, but one of the main issues with Lyme disease is that in many cases it only presents generic symptoms such as fatigue, headaches and depression.  This means it can be very difficult to diagnose Lyme disease if the patient is not aware they have been exposed to ticks.  If left untreated Lyme disease can develop into some serious symptoms as the infection spreads throughout the body, and this can cause serious problems in the joints, central nervous system and heart.

Tick crawling on white t-shirt

Treating Lyme Disease

Current Infectious Diseases Society of America (IDSA) regulations regarding the treatment of Lyme disease have recently been reviewed, and no changes were made to longstanding advice for treating this condition which recommends short term use of antibiotics.  In many cases this can clear up infections of Borrelia burgdorferi, but some patients may find that the bacteria is able to linger in the body, and this is known as chronic Lyme disease.  Although chronic Lyme disease is not officially recognized as a condition by the IDSA, many physicians do treat these kinds of cases with long term antibiotics.  Many sufferers have also found that some alternative treatments such as herbal therapies can be effective to help eradicate this bacterium from the body.

Preventing Lyme Disease

Because Lyme disease can be difficult to diagnose and treat it is a good idea to put in place some preventative measures, to reduce the risks of contracting this disease in the first place.  Here are just a few preventative techniques:

• Avoid brush and tall grass – ticks lay in wait for prey on undergrowth and grasses that are around knee to ankle height, so avoid sitting down on the ground and walking through brush and grasses when you are out and about in high risk tick areas.
• Wear Appropriate Clothing – when you are walking through areas with abundant tick populations make sure you cover up and wear trousers tucked into socks and long sleeved tops to reduce the area of skin exposed to ticks.  Also wear light clothing so that you can help spot any ticks that have attached themselves to you.
• Tick Checks – always check your clothes for ticks before you get back in your car or return to your accommodation.  Once in a private place conduct a thorough full body examination if you have been walking in high risk tick areas just to ensure you have not picked up any of these tiny creatures.  Don’t forget to check key areas such as your groin, scalp, and behind your ears and pets will also need a thorough check to ensure they are not bringing ticks into your home.

Prevention is better than the cure when it comes to Lyme disease, as this prevalent tick-borne condition can be difficult to diagnose and treat and can lead to some unpleasant and potentially harmful long term symptoms.

Experts have identified a number of strategies that have been shown to reduce tick abundance and therefore help to reduce the spread of Lyme disease, but there are currently no state-wide measures in place to deal with this growing problem.

Deer Population Control

Reducing the numbers of deer populations in high risk Lyme disease zones is a controversial strategy, but in many areas these animals are seen as one of the prime carriers of the infected ticks. This has been shown to be a potentially effective strategy as can be seen by examples such as Monhegan Island, Maine.  Here the populations of white tailed deer were totally eliminated during 1999 and 2000, and by 2004 no blacklegged ticks were found at all on the rodents on the island.  However it has not been shown conclusively that these techniques can have a significant effect on reducing the numbers of infected ticks in non-isolated areas such as mainland USA.

White Tailed Deer

Host-Target Methods

A more humane and potentially more effective method is currently being trialed, and this is called host-targeting.  This involves setting up deer feeding stations that are equipped with applicators that dispense pesticides, and also baited devices that can kill ticks feeding on rodents such as rats, mice and shrews, which are also prime carriers of infected ticks.  Host-targeted methods have performed well in testing, and initial trials have shown that the using pesticide treatments at deer feeding stations reduced populations of the known carriers of Lyme disease, the blacklegged tick ((Ixodes scapularis), by as much as 69%.  Rodent baited pesticide devices also showed well in the trials, and were also effective at reducing populations of blacklegged ticks.

Pesticides

Pesticides, in particular acaricides (targeted at the Acari group which includes mites and ticks), have been used effectively to suppress tick populations in residential areas.  This works well in combination with efforts to remove brush, dense landscaping, leaf litter and woodpiles around domestic dwellings, and in general open up areas to reduce habitats for both ticks and the prey they feed on such as deer and rodents.  The pesticides cyfluthrin, deltamethrin and carbaryl have been shown to be particularly effective at killing the nymph stage of the blacklegged ticks (Ixodes scapularis), but homeowners are not always willing to use pesticides heavily around their own properties.  There are also some concerns that pesticides could be overused and this could affect fragile ecosystems.

Landscape Management

Landscape management practices can also be used to reduce tick abundance, and strategic one year intervals of controlled wild grassland and brush burning were found to reduce the populations of tick adults and larvae significantly.  Burnings scheduled for the spring time were found to be particularly effective.

There is no way of completely eliminating the presence of ticks in wild and residential environments, but there are a number of strategies available that could help to significantly reduce tick abundance, and help to in turn reduce the risks of Lyme disease being passed to humans and domestic animals.

Tiny adult tick

Domestic animals are prone to a number of insect-borne diseases including Lyme disease, and recent figures show that nearly as many as 30% of all canines in high risk areas will have been exposed to the bacteria which causes Lyme disease, Borellia burgdorferi.  Lyme disease can be a difficult condition to diagnose and treat as many people are not aware of this condition and how it can affect their pets, and after infection the majority of canine patients are never fully cured of the bacteria, despite receiving treatment.  The severity of Lyme disease can vary from mild but persistent symptoms of fatigue and joint pains through to more serious forms of the disease which can cause fatal health breakdowns such as kidney failure.

Prevention

When it comes to Lyme disease in domestic animals prevention is the key, and this means that pet owners will need to understand about the life cycle of ticks, so that they can put effective tick control methods in place.  Ticks follow an annual lifecycle and are not harmful to pets and in all of their development stages.  During the summer ticks are generally in the immature stage and by late summer they actually stop feeding and enter the pupation stage so at this point there is a lower risk of infection, but many pet owners mistakenly believe the summer months are key times to protect against ticks.  In reality the most important stage of the tick’s development occurs in around February to March time, when the adult stage peaks and the ticks begin to feed voraciously in preparation for breeding in early spring.  This is the key time of year when ticks present a high risk of carrying the Lyme bacteria over to pets, and owners should begin using tick control methods when the adults emerge in late fall, and continue right through to early summer.

It is also important that pet owners use the right tick control methods, and for those living in high risk areas it is best to stick to veterinary-quality products as these offer a much higher level of effectiveness against ticks (90% or above) than the equivalent over-the-counter versions, so although this will cost more and will have to be sourced from your vet you will be able to provide more protection for your pet against Lyme disease. 

Adult tick feeding on a dog

Diagnosis

One of the problems with diagnosing Lyme disease is that ticks are very tiny, even in the adult stages, and so it can be difficult to tell whether your pet has been bitten or not.  If you live in a high risk area for ticks and your pet is regularly exposed to thick vegetation, wild areas and woodland edges then the likelihood of them being bitten is very high, so if your pet displays any unusual symptoms it is worth asking your vet about the possibility of Lyme disease.

Lyme Vaccinations for Pets

Bacterial vaccinations have evolved in recent years but there is still of lot of hesitancy from both vets and pet owners in using these methods to prevent against insect-borne conditions such as Lyme disease.  This is because there is a lot of misinformation about how effective these vaccinations can be, but recent studies have shown the new vaccine technologies can provide safe, effective ways to reduce the risks of pets contracting Lyme disease.

DNA sequencing test results

Diagnosing Lyme disease has always been a problem, as many of the symptoms are similar to a whole host of other conditions and traditional serological testing methods are unreliable in the early stages. Doctors have to rely on combining a list of symptoms with identifying the risks of patient exposure to ticks (which carry the bacteria responsible for Lyme disease), and as this condition can incubate in the body for months or even years before it manifests this can make diagnosis even more difficult.

A recent report published in the latest April 2010 edition of the American Journal of Clinical Pathology may bring some hope to medical staff dealing with Lyme disease around the world, as a team at the Milford Hospital, CT (headed by Connecticut physician Sin Hang Lee, MD) have now revealed a new way of diagnosing  this disease by using DNA testing to identify whether or not the patient has any of the bacteria which cause Lyme disease present in their blood. In clinical testing this DNA procedure proved to be highly successful at identifying low levels of the Lyme bacteria, which were often missed by the previous methods of serological testing.

Early Lyme Diagnosis

Lyme disease can easily be treated in the early stages by using standard antibiotics, but if left untreated this bacteria can spread through the body causing a whole host of painful and potentially debilitating conditions such as Lyme arthritis, chronic fatigue and even serious problems with the central nervous system and heart such as neuro borrelia and arrhythmia.  This is why it is so important to diagnose Lyme disease as quickly as possible, as it can save months of unnecessary pain and discomfort for patients and can prevent any serious complications from developing.

Model of DNA Strand

The DNA test discovered by the Connecticut research team is highly sensitive and specifically aimed at identifying Lyme disease, and is most effective in the early stages of the condition when the bacteria are circulating freely in the blood system. Several leading medical insurance companies have already recognized the potential of this new testing method and have provisionally agreed to cover the costs of this procedure for their members.

What Causes Lyme Disease?

Lyme disease is spread by the bite of infected black legged ticks, which are common in many areas of Europe and throughout the mid and eastern United States. Lyme disease is caused by the Borrelia burgdorferi bacteria which is transmitted through tick saliva into the body of the host, where it typically has an incubation period of around 3 to 30 days (although it has been known to remain undetected for years before manifesting symptoms in the host). The Lyme bacteria infection can spread through the body via the blood stream and also lymph nodes, and can be carried to major organs and other areas of the skin.

As well as preventing under-diagnosis of Lyme disease and ensuring that sufferers are treated as quickly as possible this new DNA technique could also help to prevent over-diagnosis of this condition, and this can reduce the unnecessary use of strong antibiotics in patients who have been misdiagnosed with Lyme disease.

Insects that feed on animals are primary carriers of a number of unpleasant diseases, and many of these can be transmitted from animals to humans such as Lyme disease, which is caused by the bacteria Borrelia burgdorferi.

Humans have a significant impact on fragile ecosystems all around the world, and research suggests that increasing urbanization and modern forest management techniques can all have a significant impact on the spread of tick-borne disease.  We often think of dramatic environmental disruptions happening in far away places such as the rainforests or Arctic glaciers, but similar problems are occurring with ecosystems right in our own backyards, and this can result in a number of problems such as an increased risk of exposure to infected ticks carrying the bacteria which causes Lyme disease.

Urbanization spreading into wild areas

Urbanization

Ticks mostly feed on woodland mammals such as mice, rabbits and deer, and because their chosen prey is more abundant at woodland and forest edges this is also where the population densities of ticks are the most concentrated.  Spreading urbanization has put woodland and forests under threat and pushed the boundaries between residential and wild areas even closer, and this means that there are more and more people living and working in high risk areas for Lyme disease.

Forest Management

Both ticks and their prey need certain habitats in order to survive, and researchers at the Washington University’s Tyson Research Center discovered that in the Missouri Ozarks (predominantly oak and other hardwood forests) those areas which were managed by the Missouri Department of Conservation and the Nature Conservancy were actually more at risk from tick-borne diseases crossing to humans and domestic animals, as selective logging and managed burns of the woodland created much more sustainable habitats for the prey ticks fed from, in particular deer and small mammals such as rabbits which both prefer the tender fresh green growth that is abundant in newly cleared woodland areas.

Woodland management can create ideal habitats for ticks

Researchers were keen to determine exactly which species were the main feeders of infected ticks in a typical woodland enviroment, and so collected ticks from a variety of sites in the managed woodland and wilder areas, and analyzed the DNA in the blood the ticks had fed on to identify which animal the blood came from, and whether or not any pathogenic bacteria were present.  This research provided some interesting results and it was found that stable deer populations did not significantly effect the spread of tick-borne diseases, but that concentrated populations brought about by plentiful food and protected habitats caused a dramatic increase in the impact and spread of tick-borne diseases such as Lyme disease.

The Importance of Tracking Emerging Diseases

With Lyme disease and other insect-borne diseases it is important we fully understand under what conditions the carriers of these pathogens can multiply and spread, as this will help health authorities and governments to identify and track emerging patterns of these potentially harmful diseases and put measures in place quickly to minimize the impact on humans.  For example the research from the Ozarks showed that managed environments caused explosions in deer populations, which in turn led to the increased risk of Lyme disease passing to humans and other animals, and this could be a significant piece of evidence to drive measures against the spread of ticks in the future, particularly when you consider that some state agencies actually encourage deer populations by planting out food for them.  In Missouri alone it was estimated that there were over 1.4 million deer, and this seems to be a similar pattern in woodland across the US, and researchers have estimated that there could be as many as 30 million deer currently living wild in the the mid and eastern United States.  It is likely that alongside these increasing deer and rabbit populations levels of other small mammals such as squirrels, shrews and mice are also booming, which can also be key prey sources for ticks, and all of this could explain why tick-borne diseases are spreading despite many efforts to hold them in check.

White footed mouse - Peromyscus leucopus

The Borrelia burgdorferi bacterium responsible for Lyme disease can infect humans, birds and mammals, and is transmitted to different hosts by tick bites. There are a number of animals that can carry the Borrelia burgdorferi bacterium and they can pass this on to uninfected ticks, but in many cases of zoonotic diseases (those transmitted from wild animals to domestic animals and humans) there is one natural animal host in particular responsible for incubating the bacterium. In the case of Lyme Disease researchers had historically considered mice (in particular white-footed mice) to be the main animal reservoir for this disease in North America, as past studies have shown that almost 90% of all ticks feeding on infected mice pick up the Borrelia burgdorferi bacterium, which is an infection rate almost double of any other species. Also mice are very common animals that occupy diverse habitats from woodland to residential districts, which would increase the spread of this disease across a larger area and this combined with the high infection rate would support the assumption that mice were the primary reservoir of Lyme disease.  Current vaccination strategies aimed at bringing Lyme disease under control throughout northern America have been based on the assumption that white footed mice are the main source of the Borrelia burgdorferi infection cycle.

New Studies

However new evidence from studies undertaken by biologists from the University of Pennsylvania have revealed that Lyme disease may have a much more complicated host pattern than first thought, and that there are actually a wide number of vertebrate species that contribute to transmitting the Borrelia burgdorferi bacterium. In a recent in-depth study carried out in the high risk tick infection area of the Hudson Valley, researchers discovered that both mice and deer (another species that is commonly linked to Lyme disease), did not actually factor very highly in the cycle of transmitting the Borrelia burgdorferi bacterium infection. The research revealed that just 25% of infected ticks were fed by mice, much less than the 55% of infected ticks discovered to have been fed by shrews in the same area. This evidence indicates that other factors such as animal population density had a huge influence on the spread of the Borrelia burgdorferi bacterium, and that focusing on just one species such as the white-footed mouse was not an effective way to combat the spread of this disease.

Combating Lyme Disease

Zoonotic pathogens (such as the Borrelia burgdorferi bacterium that causes Lyme disease) that can cross easily between human and animal species are a major threat to ecological systems all around the world, and areas where residential and wild land converge such as at forest and woodland boundaries are particular high risk zones. It is very important that researchers understand exactly how the diseases spread to

Woodland edges are high risk areas for Lyme Disease

different species and across to humans, so that they can work with governments and health authorities in finding new strategies to help protect the public and minimize the spread of infection both in wild and domestic animals. Identifying the main animal host or hosts of pathogens such as Lyme disease can be a key weapon in combating the impact of zoonotic emergences, as strategies can be implemented that interrupt the transmission of infection such as between the ticks and the primary animal hosts, thereby breaking the infection cycle and preventing the disease from spreading to new areas.

Lyme disease is a condition transmitted by the saliva of ticks when they feed on a host (human or animal), and is caused by the Borrelia burgdorferi bacteria.  It is thought that the Western blacklegged tick and the deer tick are the primary carriers of the Borrelia burgdorferi, and these are common throughout northern America and southern Canada, and high risk areas of infection for humans include forest and woodland edges and open grassy areas.

Diagnosing Lyme Disease

Testing for the Borrelia burgdorferi infection

Lyme disease typically manifests in the early stages as a skin rash, often with a characteristic ‘bulls eye’ inflammation pattern, which can take between 3 to 30 days to develop.  However it has been estimated that in as many as 30-50% of cases no rash will develop at all, and this can make diagnosis in the early stages very difficult.  If left untreated Lyme Disease can develop into more serious symptoms, which can include meningitis, heart problems, arthritis, nerve damage (peripheral neuropathy) and inflammation of the spinal cord and brain (encephalomyelitis).  Lyme disease can be challenging to diagnose, as many of the symptoms are common across a wide range of other conditions, and there are as yet no conclusive tests for identifying the disease in its early stages (serological testing is only useful when the disease has progressed further). Many patients with Lyme disease are not correctly diagnosed in the early stages, and this can lead to months and even years of unnecessary suffering.  Lyme disease can actually be treated very successfully with either oral or injected antibiotics if caught in the early stages, but if left untreated the condition can become very serious and then it can be much more difficult to combat the disease and its symptoms once it has turned chronic.  Many physicians are still relying on serological testing to identify the condition, but this is simply not reliable enough and has been shown to fail to detect the Borrelia burgdorferi infection in as much as 20% of clinical tests.  One of the reasons current tests are ineffective in the early stages of the condition is that it can take as much as six weeks after the initial infection for the Borrelia burgdorferi bactera in the blood to reach large enough levels to show up in testing.  Also this bacteria can sometimes lie dormant for long periods of time, and this can make a diagnosis difficult if it emerges later on, as the patient may not connect the condition with any exposure to ticks that occurred in the past.

Blood test for Lyme Disease

This is why it is so important that physicians are educated in the process of identifying and diagnosing Lyme disease in its early stages, and the key to this is not clinical tests but possessing a good epidemiological understanding about the risks of patient exposure to infected ticks.

Surveillance

Physicians also play a vital role in the surveillance of ticks and can help to identify new endemic areas quickly by being able to diagnose the disease effectively, and also by reporting all suspected and confirmed cases to the local Health Authority.  This process has helped researchers to pinpoint infected tick emergence in Canada, and has shown tick populations spreading in Ontario, Nova Scotia, Manitoba, Quebec and British Columbia. Through enhanced surveillance and increased awareness of symptoms and treatments, physician can play a crucial role in minimizing the impact of Lyme disease as it spreads to new areas.

Image of adult blacklegged tick

Lyme disease is a tick-borne infection, and is primarily spread to humans through bites from deer ticks, Western blacklegged ticks and possibly lone star ticks.  These tick species carry the Borrelia burgdorferi bacterium which causes Lyme disease, and feed on a number of small to medium size mammals and birds including small rodents, deer and household pets.

Birds

Birds play a major role in the spread of Lyme disease as they can pick up a tick carrying the Borrelia burgdorferi bacterium in one location, and because it takes a long time for ticks to feed they could be hundreds or even thousands of miles away before the tick finally drops off.  The seasonal migration of birds in Northern America is key to the spread of Lyme disease and over 650 species of bird migrate to different parts of the world annually, either taking part in long distance migration to places such as Africa, Eastern Europe and South America, or short distance migration of just a few hundred miles.  Many birds such as White-throated Sparrows and robins spend the winter in Northern America before moving on to summer feeding grounds in Canada, and there are also a number of transitory birds that pass through Canada as a stop over on the way to other feeding grounds, and many of these could potentially be carrying infected ticks or the Borrelia burgdorferi bacterium itself, which they could pass on to uninfected ticks in the areas they feed in.

The spread of ticks carrying Borrelia burgdorferi bacterium into Southern Canada

Reforestation

A number of factors can influence the spread of any insect species, but the main culprit for the spread of ticks is thought to be reforestation.  Ticks are hardy creatures, but they do require the right habitats to live in. For example the blacklegged tick thrives in cool, moist conditions and the majority can be found in forested areas with dense shrub layers to provide shade and moisture, and tend to condense along the forest and woodland edges, where food is most abundant.  They can also survive in denser underground planting in some landscaped residential areas.

In recent years many areas that were previous cleared for farmland in northern America have been reverted back to small patches of woodland and forest, creating ideal environments not just for ticks, but for the animals they feed on such as deer and small rodents.  This increase in wild tick populations would not normally be a major problem but as urbanization is also increasing, with residential developments encroaching on wild areas, more and more infected ticks are coming into contact with humans, and these woodland border areas in which ticks are prevalent are now coexisting alongside residential areas, creating high risk zones for Lyme disease crossing to humans.

Reforestation is thought to be having a significant impact on the increasing spread of Lyme disease from North America into Canada, and studies by the Public Health Agency of Canada have so far tracked new infected tick emergence in Ontario, Nova Scotia, New Brunswick, Quebec and Manitoba. 

Steps to Prevent the Spread

The Public Health Agency of Canada and other organizations are calling for national surveillance to be put in place to monitor the changing patterns of tick behavior, to identify new endemic areas quickly and effectively in order to notify the public and local health authorities and ensure education is put in place to minimize the impact of Lyme disease.  Doctors are now required to report any suspected and confirmed cases of Lyme disease to the Public Health Agency, and this enhanced surveillance combined with greater physician and public awareness are crucial steps to help mimize the impact of the disease as it spreads into Canada.

An Ixodia tick is a very small tick which is much smaller than dog or cat ticks. The juvenile deer tick is about the size of a pinhead, the biggest adult deer tick can grow to about three-sixteenths of an inch.

A Lyme disease infection can happen after a deer tick is attached to a human or other host for twelve to twenty-four hours. An infected deer tick has Borrelia that lives in the tick’s midgut. Ticks are parasites that insert their mouthparts into their hots and drink blood for several days. When an infected tick attaches itself to a host and feeds, the Borrelia enters the salivary gland and proceeds into it”s human hosts blood stream.

The tick larvae and nymphs usually become infected with Borrelia burgdorferi when they feed on infected small animals, in particular the white-footed mouse. The bacteria remain in the tick as it changes from larva to nymph or from nymph to adult. Infected nymphs and adult deer ticks then start feeding on other small rodents, other animals, and humans, and transmit the bacteria to them. Adult ticks preferentially feed on the white-tailed deer, which thereby becomes an significant source of Borrelia burgdorferi in regions of infestation. The tick’s life cycle takes two years to complete (see diagram below).

The deer tick’s life cycle is comprised of three distinguishing stages: larvae, nymphs, and adults and lasts aproxinately two years.

In the spring and summer of the first year, eggs hatch into larvae which feed once and molt into nymphs. Nymphs become dormant for the fall and winter.

In the second year, nymphs emerge to feed from May through July. At this time, the nymph may transmit bacteria to humans or to wild or domestic mammals.

In the fall, nymphs molt into adult ticks. The females feed on deer and various large mammals, mate, lay their eggs, and then die. If females don’t feed in the fall, they will try to find a large mammal host during the following spring. Male deer ticks attach to a host to wait for females, but do not take a blood meal.