Anaplasmosis

Vector & transmission: A. phagocytophilumis transmitted by infected Ixodes scapularis (Lyme disease tick) in Eastern USA and by Ixodes pacificus (Western black-legged tick) on West Coast of USA, and in rare cases by infected blood during transfusion.

Geographic distribution: upper Midwestern, Northeastern and West Coast United States

Reservoir host: several mammals including livestock, deer, elk, rodents and pets

Symptoms: fever, headache, muscle pain, malaise, chills, nausea/abdominal pain, cough, confusion, a rare rash. If treatment is delayed, or in elderly, and immunocompromised individuals, anaplasmosis may develop in severe form which could culminate in death.

Diagnosis & treatment: initial diagnosis is based on clinical symptoms and history of tick bite or exposure to tick-infested areas. The appropriate laboratory test depends on the stage of the illness: PCR and blood smear for early disease stage, while serology with paired serum samples for late disease stage. Specialized laboratory can also perform bacterial culture and Immunohistochemistry assay. Doxycycline is the recommended antibiotic for the treatment of anaplasmosis.

Babesiosis

Vector & transmission: the parasite is mostly transmitted by the infected nymphal stage of Ixodes scapularis (Lyme disease tick). It can also be transmitted via infected blood during transfusion. Lastly, congenital transmission has been reported, although it is rare.

Geographic distribution: upper Midwestern and Northeastern United States

Reservoir host: primarily white-footed mouse

Symptoms: Infection with B. microti can range from being asymptomatic, to flu-like symptoms, including and not limited to fever, chills, sweat, headache, body aches, nausea and fatigue. It can cause hemolytic anemia due to the lysis of parasite-infected red blood cells. It can be life-threatening in elderly, immunocompromised individuals as well as individuals without spleen or that suffer for other severe conditions.

Diagnosis & treatment: Diagnosis of babesiosis is performed with blood smear. The recommended treatment for ill patients are: atovaquone together with azithromycin; or Clindamycin together with quinine.

Heartland Virus

Disease causing agent: Heartland virus, genus Phlebovirus

Vector & transmission: the virus is transmitted by infected Amblyomma americanum (lone star tick).

Geographic distribution: Midwestern and Southern United States

Reservoir host: unknown

Symptoms: fever, fatigue, headache, nausea, diarrhea, decreased appetite and muscle/joint ache. Symptoms may resemble those of human ehrlichiosis or anaplasmosis.

Diagnosis & treatment: The diagnosis is based on clinical signs and history of tick bite in particular if between May and September (peak tick season). Routine tests are not currently available for the detection of Heartland virus. However, suspected cases can be tested for presence of viral RNA or of IgM and IgG antibodies against Heartland Virus. No vaccine or antivirals are currently available to treat Heartland virus infection. Hospitalization and supportive care are often required to alleviate the symptoms.

Human Ehrlichiosis

Disease causing agent: Ehrlichia chaffeensis, Ehrlichia ewingii and Ehrlichia muris-like (few cases), an intracellular bacterium

Vector & transmission: the bacterium is transmitted by infected Amblyomma americanum (lone star tick). It can also be transmitted via infected blood during transfusion.

Geographic distribution: Southeastern and South Central United States

Reservoir host: white-tailed deer

Symptoms: most common symptoms include fever, headache, chills, malaise, muscle pain, nausea, vomiting, diarrhea, confusion, conjunctival injection. Rash is more prevalent in children then adults.

Diagnosis & treatment: diagnosis is based on clinical symptoms and history of tick bite or exposure to tick-infested areas. A complete blood test resulting in low platelets and white blood cell counts, or elevated levels of liver enzymes may help in the diagnosis of human ehrlichiosis. Other specific laboratory tests are available. If human ehrlichiosis is suspected, doxycycline should be prescribed immediately.

Lyme Disease

Vector & transmission: the bacterium is transmitted by infected Ixodes scapularis (Lyme disease tick) and Ixodes pacificus (Western black-legged tick). Infected nymphs are mostly responsible for transmission of Lyme disease.

Geographic distribution: Northeastern, Mid-Atlantic and North Central United States, and some areas on the Pacific Coast

Reservoir host: white-footed mouse

Symptoms: early symptoms may include fever, chills, fatigue, muscle and joint pain, swollen lymph nodes, and erythema migrans (EM) rash at the location of tick bite. The EM rash usually appears in approximately 80% of the cases between 3 to 30 days after a tick bite. Later symptoms include severe joint pain, neck stiffness, headache, secondary appearance of EM rash on other parts of the body, bell’s palsy, irregular heartbeat, nerve pain and short-term memory loss.

Diagnosis & treatment: diagnosis is based on clinical symptoms and history of tick exposure. Two step laboratory testing is recommended by the Centers for Disease Control and Prevention(CDC). The first test involves enzyme immunoassay (EIA) or an indirect immunofluorescence assay (IFA). If the test is positive or ambiguous, a second test, a western blot (WB) is recommended. Both EIA/IFA and WB have to be positive to consider the patient positive for Lyme disease. Lyme disease can be treated with antibiotics as prescribed by a physician. Doses of antibiotics may vary depending on early vs. late stages of Lyme disease and patient’s health condition.

Powassan Virus

Vector & transmission: the virus is transmitted by infected Ixodes scapularis (Lyme disease tick) and Ixodes pacificus (Western black-legged tick). Humans are “dead-end” host because humans cannot transmit the virus to feeding ticks.

Geographic distribution: Great Lakes region and Northeastern United Sates

Reservoir host: small to medium sized rodents, but I. scapularis specifically feeds on white-footed mouse

Symptoms: In most people the infection is asymptomatic. Possible symptoms include fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties and seizures. Although, POW infection can be fatal upon infecting the central nervous system, and can cause swelling of the brain and meninges (membrane surrounding brain and spinal cord).

Diagnosis & treatment: diagnosis is based on clinical symptoms and history of exposure to ticks. If infection with POW virus is suspected, a blood test and spinal fluid test to check for antibodies against the virus is recommended. There is no vaccine or antivirals to treat POW virus disease. Hospitalization and supportive care are often required to alleviate the symptoms.

Rocky Mountain Spotted Fever (RMSF)

Vector & transmission: the bacterium is transmitted by infected adults and nymphs of Dermacentor variabilis (American dog tick), Dermacentor andersoni (Rocky mountain wood tick) and in the Southwestern United States, Rhipicephalus sanguineus (brown dog tick).

Geographic distribution: Continental United states

Reservoir host: small rodents

Symptoms: early symptoms may include fever, headache, nausea, vomiting, abdominal and muscle pain. In most cases of RMSF, a rash develops a few days after onset of fever.

Diagnosis & treatment: diagnosis is based on clinical symptoms along with onset of rash, history of exposure to tick bites, and time of year (May to August). A physician may request a blood test to confirm RMSF. Antibiotics should be prescribed immediately upon suspicion of infection with RMSF. The recommended antibiotic for RMSF treatment is doxycycline. 

Southern tick-associated rash illness (STARI)

Geographic distribution: Southeastern and Eastern United states

Vector & transmission: infected Amblyomma americanum (lone star tick).

Reservoir host: unknown

Symptoms: symptoms include a “bull’s-eye” rash (a red rash expanding up to 8 cm) at the site of A. americanum bite, and sometimes accompanied by flu-like symptoms.

Diagnosis & treatment: diagnosis is based on clinical symptoms, and associated tick bite. Since an etiologic agent has not been associated with STARI, there is no blood test available for its diagnosis. There are no recommendations for treatment of STARI, but physicians my treat it with antibiotics.

Tularemia

Vector & transmission: bite of infected Dermacentor variabilis (American dog tick), Dermacentor andersoni (Rocky mountain wood tick), Amblyomma americanum (Lone star tick) and Chrysops spp. (deer flies). Tularemia can also be transmitted through direct contact with infected animals, and through ingestion or inhalation of bacteria.

Geographic distribution: all states of United States, except Hawaii

Reservoir host: rabbits, hares, rodents and other small wild animals

Symptoms: symptoms vary upon route of infection. There are different forms of the disease: Ulceroglandular, glandular, oculoglandular, oropharyngeal, pneumonic and typhoidal. General symptom may include fever, chills, headache and nausea.

Diagnosis & treatment: Tularemia is hard to diagnose due to its similarity of symptoms with other common infections. Information on tick or deerfly bites, and a blood test and bacterial culture may confirm the diagnosis. A physician may prescribe antibiotics for treatment, which may last from 10 to 21 days depending on severity of tularemia infection.