Ticks and Lyme Disease

What Are Ticks?

Ticks are small, blood-feeding ectoparasites. This means that they are external parasites, living on the outer surface of their host where they insert their mouthparts and drink blood for several days. Tick larvae have six legs, while more mature ticks, those in the nymph and adult stages, have eight legs. Ticks rely on direct contact with their host, since they are unable to jump or fly. In most cases they are found in dense deciduous forests, in the abundant leaf litter, waiting to "hitch a ride". This environment is ideal for the tick, not only for the reason above, but also because the leaf litter keeps them from drying out, an act which they are sensitive to. Ticks choose mainly mammals and birds as their hosts, however, occasionally they can be found on reptiles, amphibians and humans. When the tick chooses it's host, it attaches and feeds on its blood. During this stage the appearance of the tick will change drastically from it's black and red color (at adult stage) to a blue-gray color. This color change is a result of the ticks blood sac becoming inflated and filled with blood. This inflation also causes the tick to increase in size.

This picture depicts a black-legged deer tick biting a human (left) as well as a tick which has increased in size as result of a blood meal (right).

The Tick Life Cycle

The tick life cycle consists of four stages and lasts about two years. These stages are classified as the egg, larva, nymph and adult stages. The young, juvenile nymph is only about the size of a pinhead, while a fully grown adult is at most approximately three-sixteenths of an inch. In order for each of the larva and nymph to progress into the next stage of their lives and for the adult to be able to reproduce, they must consume a blood meal. The host of these meals corresponds to the stage at which the tick is in at the time. In the first year, during the warmer months of spring and summer, the eggs hatch into the larvae, consuming a meal and then moult into nymphs. These nymphs are dormant during the colder, fall and winter months. During the next year, post-dormancy, the nymphs emerge and feed from the month of May right on through to July. This is the stage where most bacteria are transmitted to wildlife and/or humans. That upcoming fall is when the nymphs moult into adults. During fall of the adult stage, the female tick seeks to feed, mate and lay her eggs, after which she will die. However, the male adult tick is slightly different. The male seeks out a host and instead of feeding upon it; it waits there for a female to come to mate with.

Are There Ticks In Newfoundland?

The population of ticks found in Newfoundland is very small in comparison to other areas in North America. It is likely that most ticks found on the island came to be here by “hitching a ride” on an animal and are not a part of a permanent population. The tick found most commonly in Newfoundland, Ixodes scapularis, is also referred to as the Black-legged Deer Tick. This tick, according to experts, has most likely come to the island by way of migratory birds. These birds fly south for the winter, where they most likely pick up ticks such as Ix. scapularis, and then return home to the island in spring, bringing the ticks back home with them.

Since the prime host candidate for the Ix. scapularis is the White-tailed Deer, which cease to reside in Newfoundland, it is unlikely that the tick would choose to permanently populate the island. The island, as you all know, is, however, home to moose and caribou which may in time prove to be a sufficient enough host for the Ix. scapularis.

Researchers believe the idea of a tick population permanently residing in the province should not be rejected completely. This idea is disputed in arguing that since most of the island is uninhabited and made up of dense forested areas, it is near impossible to know whether or not there is a population of ticks thriving there already. It is also believed that there is the possibility of a known permanent population in the future.

Although there were 77 ticks collected across the island, not all of these tested positive for disease. In fact, the only tick species that did test positive for disease was the Ix. scapularis. Of the 62 Ix. scapularis collected, 6 of these tested positive for Lyme Disease and 1 tested positive for another type of disease called, Human Granulocytic Ehrlichiosis. Figure 1 (shown below) gives a visual of these results in approximate percentages.

What is Lyme Disease?

Lyme Disease is a tick-borne, bacterial illness which has become a great public interest in recent years. This disease is caused by a bacterium called a “spirochete”, the specific spirochete is named Borrelia burgdorferi. Therefore, the tick itself does not cause Lyme Disease, it is just a carrier for the bacterium that does.

This picture depicts the mircoscopic bacterium, Borrelia burgdorferi.

How Do You Become Infected With Lyme Disease?

The majority of Lyme Disease cases occur in the summer months with the nymphal stage is at its peak. In the winter months, the nymphal ticks are dormant and therefore the only infections contracted this time of year come from the adult Ix. scapularis. At this time of year the infection rate is low, not only because of the dormancy in nymphs, but also because of the size of adults. The adult Ix. Scapularis is much larger than the nymph ad therefore is more easily seen and therefore removed then the smaller nymphs. When a tick that has become infected by the bacterium, Borrelia burgdorferi bites a human the bacterium has a chance to transfer to the human. This happens once the tick has consumed its blood meal. At the end of the meal then tick “throws up” releasing the bacterium through its salivary glands.

How Do I Know If I Have Lyme Disease?

If you believe you may have Lyme Disease you should consult your family doctor or health care provider immediately. Do not rely on this list of symptoms for self diagnosis since not all patients will have all symptoms and many symptoms can occur with more then one illness. These symptoms also occur in different parts of the body at different times or stages throughout the disease. The following is a list of the most common symptoms with brief descriptions:

Erythema migrans (EM) – this is a circular rash that occurs 70-80% of the time. This rash begins at the site of the bite, usually within 3-30 days and then gradually expands outward over time. The rash site usually has a warm feeling and is not usually painful for the patient. The rash can sometimes also occur in other areas of the body, aside from the bite site.
Fatigue
Chills
Fever
Headache
Muscle and Joint Aches
Swollen Lymph Nodes

Note: These are sometimes the only symptoms of infection experienced

Bell’s palsy – this is a loss of muscle tone on one or both sides of the face
Severe headaches
Neck stiffness
Shooting pains that may interfere with sleep
Heart palpitations
Dizziness
Joint pain

Note: Many of these symptoms may resolve even without treatment

Arthritis
Severe joint pain and swelling
Neurological problems – such as tingling or numbness as well as problems with concentration and short term memory

Note: These symptoms occur after several months if the patient goes untreated

What Do I Do If I Find A Tick?

If a tick is found, either attached to an animal or someone you know, please proceed to the following links:

How To Remove A Tick

Form For Submitting A Tick

Further Information On Ticks

Dr. Hugh Whitney's Research On Ticks In The Province (Dr. Hugh Whitney is the Chief Veterinary Officer for the Provincial Government of Newfoundland and Labrador)

What is Human Granulocytic Ehrlichiosis?

If you have any further inquiries or comments on this subject feel free to contant me at

p33krm@mun.ca

References

Biology