I know, I should have posted this in the summer!  The fact of the matter is though, a great many outdoorsmen and women are hitting the field and woods this time of year.  It has not frosted yet so tick problems need to be a real consideration.  Many people forget or are surprised by the fact that even though summer is over, tick season is still going full force!  Let’s see what you are up against.

Types of ticks:

Generally speaking there are two families of ticks.  Many different species fall into these two families.  They are the hard ticks (family Ixodidae) and the soft ticks (family Argasidae).  Since almost all major North American tick borne illnesses are transmitted by the hard ticks, we will concentrate on those.

The hard ticks are wide ranging, found all over the US, Canada and Mexico.  Basically, if you go outside, you will encounter a hard tick.  The 8 different illnesses I want to discuss are:

1.  Tick paralysis
2.  Babesiosis
3.  Colorado tick fever
4.  Relapsing fever
5.  Ehrlichiosis
6.  Tularemia
7.  Rocky Mountain Spotted Fever
8.  Lyme disease

Fortunately, none of these illnesses are all that common.  They are frequently misdiagnosed so I wanted to remind everyone that they are out there.  We will start with Tick Paralysis.

Tick Paralysis

Tick paralysis is the only one of the tick diseases that is not caused by an infectious agent.  It is caused by a neurotoxin secreted by the tick.  It can occur in anyone but tends to be seen more in young females.  It is transmitted by both the American Dog tick (Dermacentor variabilis)  and the Rocky Mountain wood tick (Dermacentor andersoni) .  The illness begins 5-6 days after tick attachment with restlessness, fatigue, irritability, and a tingling or pinprick sensation (paresthesias) in the extremities.  In 1-2 days, an ascending, flaccid paralysis ensues beginning in the lower extremities.  Sensation remains intact.  There is no fever or rash.  Without proper diagnosis, this illness can prove fatal by paralysis of the respiratory muscles.  The treatment is simple, remove the tick.  With tick removal, resolution of the paralysis can be expected in 1-2 days.

Babesiosis

Babesiosis is a disease cause by a parasite (Babesia microti) that lives inside red blood cells.  The disease progresses from a gradual onset of malaise (unwell feeling), fatigue and anorexia (loss of appetite) to symptoms of fever, headache, nausea and vomiting, depression, chills, and dark urine.  There may be enlargement of the spleen (splenomegaly).  Diagnosis is made by repeated blood smears, antibody testing and RNA/DNA testing.  This illness may be transmitted by a blood transfusion.  The disease is worse in immunocompromised individuals and those without a spleen.  Treatment is with specialized antibiotics and exchange transfusion in severely ill individuals.

Colorado tick fever

This is a viral illness transmitted by the wood tick.  It is a benign and self limited disease.  The onset of symptoms is 0-14 days.  The illness begins with an abrupt onset of fever within about 2 weeks of exposure.  The fever can be accompanied by severe headaches, eye pain, body aches (myalgias), photophobia, vomiting and abdominal pain.  The fever pattern is called biphasic (2-3 days of fever, 1-2 days of relapse, then 2-3 days more of fever).  A rash may be present in up to 12% of patients.    Rarely, there may be serious complications with brain, heart and liver.  Treatment is generally supportive including fever control and fluid support.  There may be a blood transfusion risk with persistent viral infection.

Relapsing fever

The main bacteria genus that causes is Borrelia with 3 different species involved.  Relapsing fever has high fever periods that are separated with normal periods of up to 2 weeks.  The fever is usually accompanied by wracking chills, headaches, joint and muscle pain, abdominal pain, nausea and vomiting and altered sensorium.  The initial fever terminates with drenching sweats and severe thirst.  Each subsequent relapse is less severe.  Relapsing fever is dangerous in pregnancy due to the high incidence of spontaneous abortion (miscarriage).

Diagnosis is difficult in this illness because routine labs are of little help.  A good history, clinical exam and a high index of suspicion are required.  Occasionally blood smears and dna testing can help.  Treatment is with tetracycline and erythromycin.  Caution is necessary during treatment due to the possibility of a fatal blood pressure reaction.

Ehrlichiosis

This is my personal favorite as I fell victim to this several years ago.  This disease is caused by  intracellular bacteria called Ehrlichia chaffeensis, Ehrlichia ewingii, and Ehrlichia muris eauclairensis.  Ehrlichia chaffeensis and E. ewingii are carried by the lone star tick (Amblyomma americanum)  and E. muris eauclairensis by the black legged tick (Ixodes scapularis) also known as the deer tick .   There is usually a 7 day incubation period followed by a sudden onset of high fever, headache, chills and body aches.  There may or may not be a rash.  Outcomes are better if treatment is began early.  Late treatment can result in brain swelling (encephalitis), respiratory failure, uncontrolled bleeding, organ failure and death.  There are blood tests that can detect ehrlichiosis but they may take days or weeks to return.  The recommended treatment is an antibiotic called doxycycline.  It can be life saving.

Tularemia

Commonly known as rabbit fever, this disease is caused by the bacteria Francisella tularensis.  This disease is similar to anthrax in that the symptoms vary depending on the organisms entry into the body.  It can enter through the skin, lungs or be ingested.  This agent can also be weaponized and used as a bioweapon.  If it enters through the skin via a bite or other mechanism, there is usually a slow growing skin ulcer and lymph node involvement.    Inhalation causes pneumonia and ingestion causes a sore throat, abdominal pain and vomiting.  Treatment is with tetracycline and other antibiotics.

Rocky Mountain Spotted Fever

One of the more publicly recognized tick illnesses is that of RMSF.  It is caused by Rickettsia rickettsii and can range from a subclinical illness to a fulminate fatal illness.  It is spread by several tick species.  The illness begins 2-14 days after a tick bite with fever, chills, headache and body aches.  A rash develops in 90% of people after about 5 days.  The rash begins on the hands and feet and spreads inward covering most of the body.  It does not itch and itching suggests another cause.

Diagnosis is made by clinical examination but a skin biopsy may show the organism.  Other lab tests may take days or weeks to return.  RMSF has about a 5% mortality but treatment with doxycycline can be life saving.

Lyme disease

Probably the best know tick disease is Lyme disease.  It was first recognized in Lyme, Connecticut in 1977.  There are three stages to Lyme disease.

1. Stage 1 – Rash called erythema migrans occurs about 1 week after a tick bite.  This rash is distinctive and is described as looking like a bullseye.  The rash occurs at the site of the bite and itches.  

2. Stage 2 – multiple nerve type involvement occurs at this stage including Headache, poor concentration, memory loss, irritability, facial muscle weakness, difficulty walking, dementia and vision problems.  The patient can also develop migrating arthritic pain and hepatitis.  The arthritis may develop up to 2 years after infection if untreated.

3. Stage 3 – 1 year after erythema migrans.  It is characterized by chronic nerve involvement.

Diagnosis is difficult as routine labs and cultures may not help and antibody tests are usually negative in the first weeks of infection and have to be repeated.  Treatment requires high doses of antibiotics for as long as three weeks.  Adequate response may not be seen for several months after completion of therapy.