Spring/Summer brings many things to central Minnesota. After the winter season, most people look eagerly for spring and the ability to more readily get outside and enjoy our “North Woods” area. Along with the ability to easily get out into the woods and fields of central Minnesota, comes the likelihood of also associating with some of the local pests, specifically the ticks.

The Vector
In our area, the vector for the above diseases (that is, the agent or thing that carries, and can transmit these infections) is the deer tick (Ixodes scapularis—also called the black-legged or bear tick). The deer tick is different from, and smaller than, the common or dog tick, which does not transmit these infections. (Please see picture for visual comparison of ticks).

The ruler shown in picture is a 1" scale.  

The deer tick has a two-year life cycle. Eggs are laid by adult female ticks, following a blood meal, in the spring or fall. Most eggs hatch into larvae in late May or June with a lesser hatch peak in August through September. The larvae feed on mice (the white-footed mouse is a reservoir, or source, for the Lyme bacteria) and other small mammals (such as chipmunks), as well as birds, in late May through September. Larvae then molt into the nymph stage in late summer or fall, and go dormant until the following spring. The nymphs feed on small rodents and other small mammals and birds from mid May through mid July, and then molt into adults completing the 2-year life cycle.

Larvae and nymphs typically become infected with Lyme bacteria when they feed on infected small animals, especially the white-footed mouse. The bacteria remain in the tick as it changes from larva to nymph, or from nymph to adult. It is typically the infected nymphs and adult female ticks that then bite and transmit the Lyme bacteria to other small rodents, other animals, and humans during the course of their normal feeding behavior.

Although infection can be transmitted by both the nymph and the adult tick, probably the more common route is for the nymph to transmit infection. This is so, because of its small size, and the likelihood that it will not be seen on the skin. The tick, at any stage of development, needs to be attached for at least 24 to 48 hours before it is likely to transmit Lyme infection, but probably a lesser length of time to transmit Ehrlichiosis (anaplasmosis) (see below). Several studies have shown that the risk of Lyme infection from a KNOWN significant tick bite is only 1% to 3%. In our area, it appears that up to 15-20% of the deer ticks are infected with Lyme bacteria, and therefore capable of spreading Lyme disease. In the northern Twin Cities area the rate of tick infection appears to be lower at 5-15%. Data from the Minnesota Department of Health indicate that there were 473 reported cases of Lyme disease in Minnesota in 2003, compared to 867 cases in 2002, and 461 cases in 2001. Crow Wing County had the largest number of Lyme cases in 2003 in Minnesota with 60 cases originating here, compared to 187 cases in 2002.

In theory, Lyme disease could be spread through blood transfusions or other contact with infected blood or urine. However, no such transmission has been documented. There is no evidence that a person can get Lyme disease from the air, food or water, from sexual contact, or directly from wild or domestic animals. There is no evidence that Lyme disease can be transmitted by insects such as mosquitoes, flies, or fleas.

The Lyme Disease Bacterium
Lyme disease, first recognized in the United States in 1975 after a mysterious outbreak of arthritis near Lyme, Connecticut, is caused by Borrelia burgdorferi, a bacterium of the spirochete (or corkscrew-shaped) family of bacteria. The bacteria live in the gut of infected deer ticks, and can be transmitted to the animal or person being fed upon when the tick has been attached for over 24 to 48 hours.

Lyme Disease Infection
Lyme disease has been divided into three stages. If treated with appropriate antibiotics, it does not progress from one stage to the next.

Stage I: 3-30 days after tick bite

• A unique rash develops in 60% to 80% of people. The rash (called erythema migrans) looks like a red ring or bull's-eye that may start where the person was bitten, and expands in size. It can also occur at other sites on the body away from the bite site. Some of the rash, however, is not the classic bull's-eye (see next bullet).
• Look for a rash that expands over several days to greater than 2 inches across (whether bull's-eye in appearance or not). A rash the size of a dime or quarter is not Lyme disease and more likely represents local skin reaction to the tick's saliva.
• The rash is neither painful nor itchy.
• It lasts 2 weeks to 2 months.
• Frequently a ‘flu like' illness, with fever, chills, fatigue, muscle and joint aches, and headache can develop, and persist for several days.

Stage II: 2 to 12 weeks after the tick bite

• This stage develops in only about 15% of people who have not received treatment for the early disease.
• The main symptoms are related to the nervous system: for example, weak facial muscles (Bell's Palsy), stiff neck (aseptic meningitis), and weakness or numbness of the extremities (polyneuritis).
  
• A few people can develop abnormalities of heart rhythm (myocarditis)

Stage III: 6 weeks to 2 years after the tick bite

· This stage develops in about 60% of the people who have not received treatment for the disease.

· Often these people have had no stage-II symptoms.

· The main symptom of this stage is recurrent attacks of painful, swollen joints (arthritis). It usually affects the knees. The arthritis can become chronic.

Diagnosis of Lyme Disease
The diagnosis of Lyme disease is often made on clinical grounds alone (including a history of tick bite, or of being in a deer tick area, or symptoms and signs associated with the illness). We do have blood tests that may help us in making the diagnosis of Lyme disease, but often these serology tests take 4 to 6 weeks to become positive after infection has occurred. Further research is ongoing to develop a rapid and reliable test for Lyme disease that will become positive early on in the disease process, and enable your physician to more accurately make the correct diagnosis, and more rapidly begin proper treatment for the infection. Right now a serum (blood) test is used to screen for antibodies against the Lyme bacteria, and a second test (called the Western Blot test) is used to confirm the presence of Lyme disease if the screening test is positive.

Treatment and Prognosis in Lyme Disease
Lyme disease, once properly diagnosed by your physician, can be treated successfully by oral antibiotics in almost every instance (A typical adult course of treatment is doxycycline, 100 mg twice a day for three weeks.). Intravenous antibiotics may be necessary in particularly severe or advanced cases of Lyme disease. Particularly in the early stages of the infection, patients who are treated with adequate doses of antibiotics usually recover rapidly and completely. Most patients who are treated in later stages of the disease, also respond well to antibiotics, and full recovery is the rule. In a few patients who are treated for Lyme disease, symptoms of persisting infection may continue or recur, making additional antibiotic treatment necessary. Varying degrees of permanent damage to joints or the nervous system can develop in patients with late chronic Lyme disease. Typically these are patients in whom Lyme disease was unrecognized in the early stages, or for whom the initial treatment was unsuccessful. Rare deaths associated with Lyme disease have been reported, with Lyme disease listed as a contributor, not a primary cause of death.

A recent study by Nadelman, reported in the New England Journal of Medicine (NEJM 2001; 435:79-84), showed that a single dose of doxycycline (200 mg) given within 72 hours of a known tick bite can prevent Lyme disease. It does not, however, speak to the possible other tick associated infections (see below), and with infection rates of from only 1% to 3% with KNOWN tick bites, most people would not need this treatment. In its March/April 2004 MDH Disease Control Newsletter, the Minnesota Department of Health does not recommend this treatment (please see that article for details).

 Human Granulocytic Ehrlichiosis (HGE)/Now Called: Human Anaplasmosis (HA)

Another tick associated infection we see in central Minnesota is Human Granulocytic Ehrlichiosis (HGE) now known as Human Anaplasmosis (HA). This infection is not nearly as common as Lyme disease (there were 78 reported cases of HGE (HA) in Minnesota in 2003, down from 149 cases reported in 2002, and 93 cases in 2001), but is spread in the same fashion, and by the same ticks as Lyme disease. This infection is caused by a bacterium of the Rickettsial family (now classified as Anaplasma phagocytophilium), the same family from which Rocky Mountain Spotted Fever occurs. HGE (HA) was first described by Dr. Johan Bakken from Duluth, and since then has been studied aggressively. We do not have nearly the amount of information on HGE (HA) as we do on Lyme disease, but some characteristics are defined:

• The infection is spread by the deer tick, as is Lyme disease, and co-infection with both HGE (HA) and Lyme disease is possible. In Minnesota in 2003, 5 cases, about 6% of HGE (HA) infected patients, also had objective evidence of Lyme disease (EM rash) . Symptoms usually develop several days to weeks after an infectious tick bite and present as acute fever, body aches, headaches, loss of appetite and weight loss (similar to a prolonged flu like illness).

• There is a characteristic blood count pattern that is often seen in this infection with low white blood counts, low platelets, and elevated liver function tests, and this can help your physician make the diagnosis.
  
• Treatment, fortunately, is the same as in Lyme disease, and the antibiotic that treats Lyme infection (doxycycline), will also treat the HGE infection.

Babesiosis
A third tick associated infection is Babesiosis. This infection is far less frequent than either Lyme disease, or HGE, but is also spread by the deer tick.

• The infection is caused by a protozoan parasite (Babesia microti) that invades and lives in the red blood cells.
  
• The parasite causes red blood cells to break down (hemolysis), and causes anemia in the host.
  
• The infection is most common in the eastern USA (New York and Connecticut), but it is present in Minnesota (1 case reported in 2003, 7 cases reported in 2002, and 5 cases were reported in 2001).
  
• Incubation of the infection in the host is from 5 to 33 days, but most infections are without symptoms.
  
• Those most susceptible to this infection are those who are immunocompromised, especially those people who have no spleen (asplenic). When symptoms are present they include:
  • Hi fever (to 104*F)
  • Chills and Sweats
  • Nausea, vomiting, abdominal pain
  • Weakness, headache
    
• As with Lyme and HGE infection, co-infection with B. microti is possible
  

• Treatment for Babesiosis is with antibiotics, but medication other than doxycycline is needed to treat Babesiosis.

Prevention of Tick Associated Infections
As is always the case, an ounce of prevention is worth a pound of cure! Taking precautions when out in tick country can substantially reduce your risk of getting a tick associated infection. Understanding how ticks find their hosts is helpful in avoiding the ticks. Ticks search for host animals from the tips of grasses and shrubs (not from trees) and transfer to animals or persons that brush against vegetation. Ticks only crawl; they do not fly or jump. Ticks found on the scalp usually have crawled there from lower parts of the body. Ticks feed on blood by inserting their mouth parts (not their whole bodies) into the skin of a host animal. These following precautions may save you a lot of headache and worry:

• If possible, avoid tick-infested areas (grassy, brushy, and wooded areas), especially in May, June, and July. The ticks attach to the host at or near ground level.
  
• Wear light-colored clothing so that ticks can be spotted more easily.
  
• Tuck pant legs into socks or boots and shirt into pants, and wear long sleeved shirts.
  
• Tape the area where pants and socks meet so that ticks cannot crawl under clothing.
  
• Use insect repellent containing DEET on clothes and on exposed skin, other than the face, or treat clothes (especially pants, socks, and shoes) with permethrin, which kills ticks on contact.
  
• Walk in the center of trails to avoid over hanging grass and brush.
  
• Perform tick checks frequently when out in the woods, by using the buddy system, and check your partner from head to toe, removing any ticks found.
  
• Finally, at the end of the day, do a complete body check, including hairy areas, and remove any ticks found. This is especially important for parents to perform with their children.

Vaccination for Lyme Diseas e
Although there previously was available a three-shot immunization series for Lyme disease, in February of 2002 the vaccine was removed from the market by its manufacturer. There was a theoretical risk of arthritis being caused by the vaccine, and although no conclusive proof of vaccine caused arthritis has been shown, the possible association significantly decreased sales of the vaccine, and motivated the company to remove the vaccine from the market. As of this writing, there are no plans to put the vaccine back on the market, and there is no known activity at other companies to develop a different Lyme vaccine.

Tick Removal
Finally, if you have been unsuccessful in avoiding the ticks, and one has decided to make you its next meal, the following tips may be helpful in successfully removing any feeding ticks.

The simplest and quickest way to remove a tick is to pull it off. Use fingers or tweezers to grasp the tick as close to the skin as possible (try to get a grip on its head). Pull gently and steadily upward until the tick releases its grip. Do not twist the tick or jerk it suddenly. Such maneuvers can break off the tick's head or mouth parts. More important than technique, however, is to remove the tick as soon as possible!

Sometimes the tick's body comes off, but the head stays in the skin. You should remove the head also. Although the embedded head parts are not considered to significantly increase the risk of acquiring one of the tick associated infections, they can be a source of secondary skin infection. Use a sterile needle to remove the head, just as you would to remove a sliver. If this is not successful, a trip to your physician's office may be necessary.

Wash the area of the tick bite and your hands with soap and water after you remove the tick, and then watch for any signs of the tick associated infections reviewed above.

Here are some removal techniques to avoid ! A recent study showed that attached ticks do not back out when covered with petroleum jelly, fingernail polish, or rubbing alcohol. It was thought that this would block the tick's breathing pores and take its mind off eating. Unfortunately, ticks breathe only a few times per hour. The study also found that touching the tick with a hot match did not make the tick detach. In fact the hot match could make the tick vomit infected secretions into the wound!

There is so much to enjoy in our wonderful North Woods environment, that I hope you will not let the remote possibility of tick bites and even more remote possibility of tick associated infection deter you from taking full advantage of our area. If you follow the precautions listed above, and use the information above to appropriately make decisions regarding possible tick associated infections, you should be able to fearlessly go where ever you wish here in North-Central Minnesota!

*My thanks to David Neitzel Minnesota State Department of Health, section of Epidemiology, for reviewing this article and making significant contributions to its content and accuracy.