Tick bites

1. Tick-borne infectious illnesses...

Given the high frequency of tick bites, and in some cases a high prevalence of tick carriers, tick-borne illnesses in humans represent a relatively rare event.

Babesiosis-is caused by a tiny parasite Babesia microti which lives inside red blood cells. The deer tick (Ixodes scapularis) bites the white footed mouse which harbors the Babesia. If the same tick bites a human, the Babesia may be transmitted. If a human is infected, illness generally begins weeks to months later. The illness usually involves prolonged fever, joint pain, and nausea and vomiting. Only rarely is it life-threatening. Diagnosis is made by microscopic analysis of blood smears, although some antibody tests are coming available as well. Often, the immune system will clear the illness on its own, however, for individuals without a functional spleen, the elderly, or moderate to severely ill individuals, treatment is available in the form of antibiotics, and sometimes blood transfusions.

Colorado Tick fever-is caused by a virus which is carried by the wood tick(Dermacentor andersoni). Infection is limited almost exclusively to the Western U.S. and Western Canada. Infected humans develop symptoms within a few days of the tick bite. Most often these early symptoms are fever, muscle, head and back aches. The virus tends to involve the bone marrow where it decreases the marrow's ability to make white blood cells (which fight infection) and platelets (which help stop bleeding). Rarely, other areas of the body may be involved such as the heart, lungs, liver, testicles, skin and lymph nodes. The few serious reported cases have involved excessive bleeding or inflammation of the brain. Most people recover fully. There is no specific therapy against this virus.  If the platelet count is dangerously low, a platelet transfusion may be needed.

Ehrlichiosis- Ehrlichia species are microscopic organisms which live within white blood cells. Infected persons are inoculated with the Ehrlichia through tick bites, but just where the ticks get the Ehrlichia is not known. Once in the human, the effect is widely variable. Sometimes a rash will develop about a week after the tick bite. The bone marrow may become involved resulting in anemia (low blood count), thrombocytopenia (low platelet count--platelets are needed to stop bleeding), or affect other blood cell lines. In some cases the lungs, liver, brain, and kidneys have been involved, and fatal cases have occurred. Diagnosis is made after a high level of suspicion prompts antibody tests. Treatment with specific antibiotics (usually doxycycline) is effective.

Lyme Disease- Lyme+disease is caused by infection with the bacterium Borrelia burgdorferi. Lyme disease is transmitted to humans by infected ticks. Not all ticks will carry Lyme disease though, specifically the deer tick or black-legged tick in the East and the Western black-legged tick in the West. Deer ticks like to hide in shady places, tall grasses, and woods. The tick needs to be embedded in the skin for 36 to 48 hours to transmit Lyme disease. There are early and late symptoms of Lyme disease. The earliest symptom is an enlarging rash at the site of the tick bite called erythema migrans. Later symptoms include arthritis, heart block, facial paralysis, meningitis, and encephalitis. Treatment for early and late Lyme disease is with antibiotics. 

Powassan encephalitis- This exceptionally rare illness is caused by the powassan virus, which may be transmitted by tick bites (Wood tick (Dermatocentor andersoni) and Deer tick (Ixodes species)) directly to humans, or by drinking the unpasteurized milk of infected goats. Usually, several weeks after exposure, a febrile illness develops which progresses to encephalitis with possible paralysis and seizures.

Relapsing fever- This illness is caused by different species of the same genus of organisms which cause Lyme Disease. Various "non-burgdorferi" Borrelia species are transmitted to humans from bites of "soft body ticks". These ticks apparently take much shorter meals (10-30 minutes) and often feed at night leaving their victims without any hint that they have been bitten. Typical symptoms include rash, muscle aches, joint aches, headaches and fever. Severe illness involving the heart, lungs or brain may also occur. The name is derived from the pattern of the fever which may recur multiple times if not treated.

Rocky Mountain Spotted Fever- This illness is a serious and often severe illness caused by the organism called "Ricketssia ricketsii". Various ticks transmit the disease to humans (Dog tick, wood tick, Lone Star Tick). Symptoms include fever, headache, muscle aches, nausea, vomiting, and diarrhea. A rash often develops which characteristically involves the palms and soles (very few illnesses cause rashes on the palms and soles--syphilis and hand-foot -mouth disease are two others) . Illness may involve many organ systems including the brain, heart, and lungs. In severe illness, shock and death may ensue. Treatment is with specific antibiotics, most commonly doxycycline, and other specific supportive care as needed.

Tick-borne encephalitis (not in the U.S.)-This virus is spread by the ticks of the Ixodes genus in all European countries, some of which vaccinate against the illness. As well, tick-borne-encephalitis specific immune globulin may be given after tick bites in Europe. No other treatment is available. In infected individuals, a nonspecific febrile illness progresses to involve the brain--with consequent paralysis, seizures, discoordination, and nerve pain.

Tularemia- Tularemia is the name for any of a number of syndromes caused by the bacterium Francisella tularensis. Ticks bites are only one source of this infection. Often, the illness is contracted from the infected animal in a more direct route or through bites by other insects. Rabbits especially are known to be sources of infection. Illness may involve skin ulcers at the bite site, lymph node infection, severe throat involvement, and inflammation of the lungs, liver and/or spleen. The illness responds to specific antibiotics, most often tetracycline or gentamicin.

2. Bacterial Superinfections...

Tick removal often results in some tearing of the skin at the site of the tick bite due to the adherent ability of the tick. Any skin break is a potential site of bacterial infection. Superinfection simply means bacterial infection in addition to the original illness or problem. Typical bacteria are staphylococcal and streptococcal species. After tick removal, cleansing of the site with soap and water and application of an antibiotic ointment will minimize the risk of bacterial superinfection. Redness surrounding the bite site, or drainage from the area is concerning for bacterial superinfection and should prompt a visit to your child's physician.

3. Tick Paralysis...

This rare disorder is caused by the release of a neurotoxin by the bite of a wood tick or dog tick. The tick must remain on the affected individual for a number of days to cause the paralysis. The symptoms fade quickly after removal of the tick in its entirety. Therefore, if a child has no symptoms at the time of tick removal, then there is no risk of this complication.

How to remove a tick...

The only safe way to remove a tick is to physically pull it from the skin. Attempts to smother or drown the tick are not effective. Efforts to burn the tick off may result in burns to the child and may increase the likelihood of transmission of tick-borne infectious illnesses. The tick should be grasped by the head with a pair of tweezers or similar device. Commercially available notched scoops allow an acceptable alternative. Do not grasp the tick by the body as the resulting squeeze may force fluids from the tick onto the bite site and increase the risk of transmission of tick-borne illnesses.

Preventing tick bites...

updated 08/25/2000

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