Thursday, June 7, 2012

Ticks

From what I have been told by the people I work with in the forest industry is that this year is gearing up to be a real good one for tick populations. This being said, today at work I was left a fact sheet pertaining to Lyme Disease in the result of a tick bite, also it squashes and confirms some of the rumours out their about the disease and how to deal with the blood sucking critters. For those of you who enjoy the outdoors, this is an informative read if you have a few minutes.
The stuff I am sharing is from the Public Health Agency of Canada.

What is Lime Disease

Lyme disease is an illness caused by the bacterium, Borrelia burgdorferi, which can be spread through the bite of certain types of ticks. Lyme disease in humans can have serious symptoms but can be effectively treated. Lyme disease is the most common vector-borne disease in the temperate zone and occurs in Europe, Asia, and throughout much of North America.

How do people get Lyme Disease 

Ticks live in and around wooded areas and they get infected when they feed on mice, squirrels, birds and other small animals that can carry the bacterium. Ticks then spread the bacterium to humans. Tick bites are usually painless and most people do not know that they have been bitten. Two types of ticks are responsible: the western blacklegged tick in British Columbia and the blacklegged tick in other parts of Canada. People can’t spread Lyme disease to each other. Although dogs and cats can contract Lyme disease, there is no evidence that they can spread the infection directly to people. Pets can, however, carry infected ticks into homes and yards. Hunters may be at greater risk, because they spend more time in habitats where ticks tend to live. However, Lyme disease cannot be contracted from butchering or eating deer meat or organs. 


What are ticks?

Ticks are small biting arachnids (related to scorpions, spiders and mites) that feed on blood. Ticks vary in size and colour; blacklegged ticks are very small. Before feeding, adult females are approximately 3-5 mm in length and red and dark brown in colour. Ticks feed on blood by attaching to animals including people with their mouth parts. Females are a little larger than males and when they’re full of blood can be as big as a grape. Males never expand in size because they do not engorge on blood. Larvae and nymphs (the juvenile life stages) are smaller still and, when unfed, are lighter in colour than adult ticks. People and pets can pick up ticks by brushing against vegetation like grass, shrubs and leaf litter.

Figure 1 - Female blacklegged ticks in various stages of feeding
Figure 1: This figure shows the size and colour of female blacklegged ticks in various stages of feeding by using a photograph of five female ticks superimposed on a plastic ruler and next to which a 10-cent coin has been placed. The photograph shows that unfed female ticks are a dark reddish brown colour, they become paler brown to yellow as they start to feed, then they become greyish as they continue to feed and are dark grey-brown when fully fed. As the ticks feed the abdomen of the tick enlarges so the tick increases size from approximately 0.3 cm when unfed to 0.6 cm when partially engorged. When fully fed the tick is approximately 1cm long and egg shaped.

Figure 2 - Unfed, partially fed and fully engorged nymphs of the blacklegged tick
Figure 2: This figure shows the size and colour of nymphs of the blacklegged tick in various stages of feeding by using a photograph of three nymphs superimposed on a plastic ruler and next to which a 10-cent coin has been placed. The photograph shows that unfed nymphal ticks are very small (0.15 cm long) and grey-brown in colour. As they engorge their abdomen enlarges and darkens until when fully fed the engorged nymph is approximately 0.3 cm long, almost black in colour and egg shaped.
There are areas in Canada where tick populations that transmit the agent of Lyme disease are established and these are known as Lyme disease endemic areas. Though western blacklegged ticks, Ixodes pacificus (sometimes called the deer tick), are widely distributed in British Columbia, populations are largest in the lower mainland, on Vancouver Island and in the Fraser Valley. Established populations of blacklegged ticks, Ixodes scapularis(sometimes called the deer tick), on the other hand, have been found in southeastern Quebec, southern and eastern Ontario, southeastern Manitoba and parts of New Brunswick and Nova Scotia.
Blacklegged ticks can be found in many parts of Canada, even where tick populations have not been identified. These ticks are likely introduced into these areas by migratory birds and about 10 per cent of these “bird-borne” ticks are infected with the Lyme disease bacterium. So, while it is possible to be bitten by an infected tick almost anywhere in Canada, the chances of this happening in places where tick populations are not established are very low.

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