The following is a list of symptoms in the order that they generally appear, taken from http://www.aldf.com, the home of the American Lyme Disease Foundation.

Localized Early (Acute) Stage:

• Solid red or bull's-eye rash, usually at site of bite
• Swelling of lymph glands near tick bite
• Generalized achiness
• Headache

Early Disseminated Stage:

• Two or more rashes not at site of bite
• Migrating pains in joints/tendons
• Headache
• Stiff, aching neck
• Facial palsy (facial paralysis similar to Bell's palsy)
• Tingling or numbness in extremities
• Multiple enlarged lymph glands
• Abnormal pulse
• Sore throat
• Changes in vision
• Fever of 100 to 102 F
• Severe fatigue

Late Stage:

• Arthritis (pain/swelling) of one or two large joints
• Disabling neurological disorders (disorientation; confusion; dizziness; short-term memory loss; inability to concentrate, finish sentences or follow conversations; mental "fog") 
• Numbness in arms/hands or legs/feet

The first symptom of Lyme disease usually noted by individuals is an expanding rash, known as erythema migrans (EM).  This rash is believed to appear in 80-90% of all Lyme disease cases. General characteristics of an EM rash are:
  ·         Solid red expanding rash or blotch, OR the well-known ringed expanding rash (bull’s eye)
  ·         Usually radiates from the site of the tick bite
  ·         Generally appears 3-30 days after infection of the disease has taken place
  ·         Average size reflects a 5-6 inch diameter
  ·         Painful or itching at the site of the rash
  ·         Warm to the touch
  ·         Persists for 3-5 weeks after first noticed.
  Due to the tick’s preference for body creases (i.e. armpit, groin, back of knee, etc.) rashes are often localized in these areas.  In some cases,  multiple rashes will appear elsewhere on the body after the initial rash, or in absence of an initial rash.

Since 1982, more than 150,000 cases of Lyme disease have been reported to the CDC (Center for Disease Control and Prevention).  Due mainly to the fact that the disease have numerous and diverse manifestations, and the limitations of blood tests currently available, the diagnosis and treatment for Lyme disease can be challenging. 

The abundance of Lyme in the US is due primarily to the large number of white-footed mice and deer, the preferred hosts of the deer tick, as well as their proximity to human populations.  Many larval and nymphal deer ticks become infected with Lyme disease by feeding on and infected white-footed mouse, thus giving these mice the title of “reservoirs of infection”.  Studies conducted on the transmission of Lyme disease shows that an infected tick cannot or will not begin transmitting the spirochete until it has been attached and feeding for at least 36-48 hours.  For this reason, it is HIGHLY suggested that you examine yourself at least once a day for ticks.

Larval Stage – Eggs are generally laid by an adult female in the spring, and hatch into larvae later in the summer.  Peak activity is generally reached aroung August.  At this point, the larva will wait on the ground for a small mammal or bird to attach onto.  The larva will begin to feed and engorge over the period of a few days.  During this feeding, the possibility of becoming infected with the Lyme disease bacterium, spirochete, is found.  If the host has already been infected with Lyme disease, the larva will likely become infected.  Larva are not born with Lyme disease, but rather must become infected during their first blood meal.  Having already fed, larva will not seek another host until it reaches the next stage in its life cycle.  That being said, larvae do not pose a direct threat of Lyme disease transmission.

Nymphal Stage – Larva will molt, transforming into nymphs, after completing their first feeding and dropping off their host.  The nymphs remain inactive throughout the winter, becoming active around May.  At this time, the nymphs will begin to seek out a host by waiting on low vegetation for a small mammal or bird.  Similar to the larval stage, the nymph will then attach to its host, and feed for a few days.  If the nymph was infected with the Lyme disease bacterium, it may infect its new host.   If not previously infected, the nymph may become infected from its new host, assuming the host already carries the Lyme disease spirochete.

When humans are the hosts that come into contact with nymphs during their peak activity times (May through July), they often go unnoticed for quite some time.  This is due mainly to the fact that nymphs are about the size of a poppy seed until engorged.  The late detection of a feeding nymph is responsible for nearly all cases of human Lyme disease infection.

Adult Stage – As with previous stages, the nymph will drop off its host, and molt into an adult tick.  The adult tick will seek a new host through out the fall, and are capable of waiting up to three feet above the ground on high grass or leaves waiting for their preferred host, deer.  Other larger mammals will suffice, including humans, dogs, cats, horses, cattle, etc.  Peak activity for this stage of life occurs during late October and early November.  While studies in endemic areas show that 50% of adult deer ticks carry the Lyme disease spirochete, few cases are acquired from adult tick bites.  This is accredited to the fact that by the time a deer tick reaches the adult stage, it is already relatively large, and ticks that have latched onto their host are usually found and removed before the transmission of Lyme disease spirochete can occur.  The transmission of the disease generally takes an attached tick more than 36 hours.

Ticks, which are parasites that feed by drinking the blood of its host, are responsible for at least ten known diseases in humans in the United States, including Lyme disease.  Their method of feeding, which involved latching onto a warm blooded host, imbedding their mouthparts into the host’s skin, and sucking its blood, makes ticks the perfect vectors (any person, animal, or microorganism that carries and transmits an infectious agent).

A zoonosis is defined as any infectious disease which can be transmitted back and for from non-human species to humans, or from humans to non-human animals.  This sometimes takes place through a vector.  Of the 1415 pathogens currently known to affect humans, 61% are zoonotic, including Lyme Disease.

A vector insect, such as a tick, must first bite an affected individual or animal, before it is possible for the disease to be transmitted to an unaffected individual.  While the number of species of tick is very high, there are not many species that will interact with humans and animals causing them harm.  This is mainly due to that fact that most ticks have limited and specific hosts that they will feed off of.  The ticks that cause concern are those which are opportunistic feeders, meaning that they will feed on nearly any accessible hosts.  These ticks are the ticks that pose the largest treat of disease transmission and infection to humans.  Keep in mind that ticks generally are not born with disease agents, but instead must acquire them during feedings throughout their life cycle.

There are three separate stages in the life cycle of a tick, which are classified in order as larval, nymph, and adult.  The majority of disease transmissions are credited to the ticks in the nymphal stage of life, from the Ixodes group (which includes the deer tick).  The deer, or black-legged tick, and the western black-legged tick are the only known vectors of Lyme disease in the US.  Both species are hard-bodied ticks with a two year life cycle, and like all species of tick, require a blood meal to develop further.