Tick and Mosquito Borne Illnesses

What are tick and mosquito borne illnesses?

Ticks and mosquitos can carry many different disease-causing bacteria and viruses. The two most common are Lyme disease and West Nile virus.

What are the causes and risks of Lyme disease?

Lyme disease (LD) is caused by tick bites after being in tick-infested areas or from close contact with an animal that carries infected ticks.

• The longer the tick remains attached to a host, the greater the risk of bacterial transmission.
• Risk of being bitten by a tick is highest in the spring and fall.
• Hunters, hikers, and other people who frequent wooded and/or grassy areas are at increased risk.
• Risk of developing LD is increased when tick attachment lasts longer than 72 hours.

What are the causes and risks of West Nile virus?

West Nile virus (WNV) is transmitted to humans by infected mosquitoes.

• Although in most people the infection is asymptomatic or results in a self-limited, mild flu-like illness, WNV infection can cause epidemics of meningitis, encephalitis, and acute flaccid paralysis.
• Performing outdoor activities in areas where WNV is endemic increases risk for mosquito bites and WNV infection.
• The risk for neuroinvasive illness and death resulting from WNV infection increases in those aged 50 years and older. Patients who are immunocompromised, or have cancer or kidney disease, are more likely to develop a severe infection.

What are the signs and symptoms of tick and mosquito borne illnesses? 

Lyme disease

• Early localized Lyme disease, which develops 3–30 days after a tick bite: primary erythemamigrans, fever, headache, myalgia, arthralgia, fatigue, and general or regional lymphadenopathy.
• Early disseminated Lyme disease, which develops a few days to 10 months after a tick bite: development of additional erythemamigrans lesions, arthralgia (typically in knee joints) stiff neck, photophobia, sensory loss, asymmetric back pain, poor memory, difficulty concentrating, hyporeflexia, nonpainful paresthesia, meningitis, nerve palsies, myocarditis, cardiac conduction blocks, chest discomfort, dyspnea, light-headedness, syncope, Bell’s palsy, encephalitis, peripheral neuropathy, conjunctivitis, anorexia, and nausea.
• Late Lyme disease, which develops months to years after a tick bite: chronic arthritis (especially in knee joints), severe fatigue, subacute encephalopathy, axonal polyneuropathy, mood and personality changes, sleep disturbances, headaches, paresthesia, and interstitial keratitis.

West Nile virus

• Over 80 percent of individuals with WNV remain asymptomatic.
• Symptoms of WNV fever include sudden onset of fever, cough, malaise, eye pain, headache, myalgia, lack of appetite, nausea, vomiting, diarrhea, a diffuse maculopapular skin rash, joint pain, swollen lymph node, generalized weakness; symptoms typically resolve after a few days, but can progress to neuroinvasive illness.
• Patients may develop one-sided weakness, paresthesias, sensory loss, and diffuse pain.
• Patients who develop encephalitis can experience mental status changes, (e.g., disorientation or confusion), changes in level of consciousness ranging from lethargy to coma, cranial nerve palsies, optic neuritis, and seizures.
• Patients who develop meningitis can experience severe fever, headache, photophobia, and nuchal rigidity.
• Acute flaccid paralysis usually appears as a sudden onset of weakness without sensory deficits.

How are tick and mosquito borne illnesses treated?

Treatment of LD is primarily with antibiotics (e.g., doxycycline) and symptom relief is achieved with analgesics, antipyretics, and anti-inflammatory medications. Although antibiotic therapy is curative in most patients, a minority of patients have symptom relapse or have persistent symptoms after antibiotic treatment. Prompt administration of antibiotics after known tick exposure can prevent the development of LD.

When should I call my healthcare provider?

For tick borne illnesses, call your doctor if:

• A tick is attached to your body and you are unable to remove the entire tick.
• You have a circular red rash that expands over the course of several days, especially if you know you were recently exposed to ticks.
• You feel very tired or have sore joints, irregular heartbeats, neck pain or a severe headache.
• You are pregnant or nursing and you think you may have been exposed to ticks.

For mosquito borne illnesses, call your doctor if:

• You have a severe headache, a stiff neck, disorientation or confusion, and you were recently exposed to mosquitos.