LYME DISEASE. Current concepts

LYME BLOG

A lot of ticks! The important tick in transmission of Lyme is the tiny deer tick: Ixodes Scapularis. This is the tick that transmits Lyme infections. It also spreads Babesiosis and Human granulocytic anaplsmosis HGA, now called Ehrlichiosis.
It has a complex life. It has a two year life cycle. It starts as an egg and then passes through three stages, larva, nymph, then adult in the second year. It must have a blood meal at each stage to pass on to the next. Both nymph and adult transmit disease. Each stage has a preferred host for its blood meal. 

For Larva the preferred host is the white footed mouse. Nymphs who winter over present in the early spring of the second year prefer small mammals as host but will feed on humans. Adults more common later in the second year prefer larger mammals such as deer. They sit on leaves and grasp onto whoever gets near. Adult females will attach to dogs and humans and climb up legs and embed in protected areas. Skin folds etc. Adult ticks while small are easier to find than the smaller nymphs, but both can have Lyme rickettsia. The tick is found embedded in the skin with a small erythema around it.

    

How do ticks get borrelia bergdorfen? It circulates between Ixodes ticks and vertebrates in an enzootic cycle. Tick larva must feed on the blood of an animal infected with the spirochete which ends up in the tick larva mid gut. The spirochetes survive as the larva molts into a nymph. The nymph feeds on another small vertebrate passing the spirochete from its mid gut to the small mammal, thus completing the cycle. The spirochete will stay in the mid gut of the nymph as it progresses to an adult and female Adults feeding on larger mammals will pass the spirochete, but this ends the tick to animal to tick to animal etc spirochete cycle.

B. Bergdorfen is a spirochete with an outer membrane, an inner membrane and seven to eleven flagella to propel it. It is slow growing, with doubling time of 24 to 48 hours. Doxycycline does not kill it but alters its membrane and causes it to be unable to reproduce. It lives in the mid gut of the tick. When the tick embeds itself on you and starts getting its blood meal, the spirochete starts its trip out of the midgut and into the salivary gland of the tick and into you. This takes time. At least 24-48 hours. Key point. The chances of Lyme are very small if the tick is removed in the first 24 hours. Also the tick should not be compressed when removed. You do not want the contents of its body put into you. This may be a reason not to use Vaseline and soaps to help remove it. Bottom line: Look and remove ticks promptly. 

Problem is that in the early spring the nymph form is VERY small and often hard to see. They can give you Lyme.  

You go out into the grassy areas around your house. A deer tick nymph or female adult grabs you, it climbs up your leg to your bottom and embeds! You feel nothing. Once embedded it starts its meal of your blood. B Bergdorfen the rickettsia in its midgut is stimulated to migrate up to the tick salivary glands and into you. The trip takes at least 24 hours and maybe 48 hours. You have the first stage of Lyme. The tick is still embedded and there is a small red ring around the area.  

Help! You may try and pull off the tick, but often you may need medical help. If the tick has been on you less than 48 hours, I will remove the tick and reassure you that the chance of Lyme is very small. I will tell you the symptoms of Lyme: headache, fatigue, red circular rash with clear center, muscle aches, joint pain. If you develop these come back for treatment. At this time blood tests for Lyme will be negative. The two tests done are not as accurate as we would like and can give false negative and false positive results. Some practioners prescribe you a single dose of doxycycline as a preventative. This probably does not work because doxycycline is a bacterostatic drug, not bactericidal, so more than one dose is needed. There is little evidence a single dose does more than perhaps stop the erythema migrans red circular rash.  

If the tick has been embedded a longer period and if it is filled with your blood and you live in an area with a lot of Lyme they will recommend that you be treated, even if there are no other symptoms.  

If you have signs of an early localized infection with the development of a round circular rash often over 10cm in diameter with a central clear area you must be treated. This is erythema migrans and occurs about 70% of the time. It is the symptom of local skin spread of the spirochete and Lyme is very treatable in this early stage.

This stage of Lyme needs to be treated with antibiotics: Doxycycline 100mg twice a day for at least 14 days and better 20 days. Doxycycline alters one of the Lyme membranes and prevents the spirochete from reproducing. This is curative for early Lyme.

What is the progress of the Lyme spirochete, Borrelli Bergdorfen, once it has entered through the tick wound and is ready for action. It first spreads locally and thus the erythema migrans target rash. While your immune system will try to destroy it, it can resist this and quickly spread through your blood stream. This will cause an early disseminated Lyme in about one to four weeks. Erythema migrans rash may appear in different areas. Joint pains may start. It can have neurological findings. Bell’s palsy, paralysis of the facial nerve, may occur. You are sick. Headaches, fatigue etc. Antibiotic treatment with doxycycline is effective in cases of early disseminated Lyme but may require a longer course.  

After several months untreated or inadequately treated Lyme can develop into late disseminated Lyme. This is an area that there is a lot of medical confusion about. People with this need to see physicians who specialize in the treatment of late Lyme. It can disseminate as arthritis with joint pains, muscle weakness, cardiac as conduction delays, neurologic with headaches, memory loss, etc. Not fun. 

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