Lyme Disease
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If the viral disease AIDS were not present, the most infectious "new" disease would be Lyme Disease. This bacterial infection has reached epidemic proportions in a number of areas in the United States. This exercise will seek to show you how this disease is passed to humans through a series of animal "hosts".
Show ImageJ application.
Go to File, Open Samples and open the images SpiroM and SpiroTEM. The first of these SpiroM shows a blood smear with several red blood cells. The faint "squiggly line" in the field is a type of bacterium called a spirochete. Its actual name is Borelia burgdorferi and it is the organism that causes Lyme Disease. Because of the spirochete is so small it can be best seen through a Transmission Electron Microscope. This is the view that you get in the file SpiroTEM . The TEM view also gives you a more accurate indication of the length of this spirochete. Using the Freehand Line
tool CALIBRATE the image and then measure the length of the spirochete in each view. Compare your results with an average spirochete length of 30 micrometers.
(Put your results in the Results Table)
Someone infected with this spirochete will exhibit flu-like symptoms of chills and fever accompanied by aches and pains in muscles and joints. This generally happens within about twenty days. There may also be a circular rash where the spirochete was injected. Antibiotic treatment at this stage is usually very effective and the spirochete is killed. However, if the victim is unaware of the severity of the illness, and if the infection is left untreated, their may be neurological and cardiac abnormalities accompanying a new series of rashes weeks or even months after the original infection. This can be followed by damage to the central nervous system producing behavioral malfunctions as well as long term arthritic problems.
The disease spreading organism is the deer tick (Ixodes scapularis). Larvae hatch from eggs that have been laid in the Spring by the adult female.
The larval stage feeds for a short period of time during the summer and it is usually during this feeding period that it acquires the spirochete. The host is typically a mouse. The larvae is dormant over the winter and molts into the Nymph stage in the spring.Go to File, Open Samples and open the image NymphSEM. Calibrate the image and measure the length of this tick. (Go to the Image Calibrate in the Open Samples if you need instructions on this procedure) Compare the larval stage of the tick to the nymph stage. What is the major difference between the two other than length? (Put your results in the Results Table) The nymph stage of the tick has a longer feeding time and it is when the tick is in this stage as a parasite --typically on white-footed mice -- that it will often bite humans and pass-on the disease. The nymph that you measured is around a millimeter in length so you can see how it would be difficult to spot this little pin-headed structure on your skin. At the end of the summer the nymphs will molt into adults and it is now possible to distinguish the two sexes.
Go to File, Open Samples and open the image MalDVSt. The first image in this stack shows two adult male Ixodes ticks. The one on the left is ventral side up and the one on the right is dorsal side up. Using the slider key will show a slightly enlarged image of the dorsal male with a few of the parts labeled. The scutum is a shield like device over the abdomen of the animal. The pedipals help to anchor the tick to its prey and the basis capitulum is a "head-like" structure containing certain sensory organs. Use the slider key to move on to a ventral view with the associated labels. The anus is for waste removal and the hypostome has the serrated teeth that you saw in the previous light microscopic views of the adult.
The principal host for the adults is the white-tailed deer. The adults mate on the deer with the male dying soon afterward. The female uses her blood meal from the host to survive the winter and nourish the up to 2000 eggs she will lay in the spring.
Optional/Extra Credit
1.
2.
You have two ventral images showing the female hypostome with a series of teeth covering the hypostome. Describe the appearance, arrangement and function of these teeth.
Reference
The follow are WEB reference sites for information on Lyme Disease
The Luxembourg Health Server Listing of various links to Lyme Disease Information.
The Lyme Disease Foundation Also includes links to NIH and information on West Nile Disease.
Lots of Links on Lyme Disease Over 7,000 Categorized Links on Lyme Disease
RESULTS TABLE
(You can also Go to File, Open Samples and Open the image Results which is a copy of this Results section. While this page cannot be printed out - at this time - it can be saved as a JPEG file to your desktop. You can then open it with any graphics program,type out the answers and then print it out from your program.
You can also enter the results on this image using the Text
Tool. To do this first go to Edit, Options, Fonts and select something like Geneva - 12 pt - Bold. Then click on the Results Image in the answer space and draw out the yellow rectangle that appears and start typing. When you are finished go to Edit and Select Draw. What you have typed should now be present.
1. Spirochete length:
A. Blood smear__________µm B. TEM___________µm
Explanation:
2. Larvae/Nymphs A. LarvaeLM_____________ B. LarvaeSEM_____________
C. NymphSEM____________Main distinction between Larvae and Nymph other than size?
3. Comparison of "head" structures in the light microscope view of the adult male and female.
4. Distinguishing characteristics between the male and female Ixodes. (Be as specific as possible in what you are describing and where the structure is located.)
Optional/Extra Credit:
1. Female pedipalp structures. Their possible function and your rationale for believing this to be the case.
2. Female hypostome:
Describe the appearance, arrangement and function of the teeth covering the hypostome. Could the tick hyposotome be used as a classification device to determine what type of tick you are looking at? Comment?
