Arthropod-borne diseases are a major problem whenever outdoor activities bring arthropods and people into contact. The arthropods discussed here include arachnids (ticks) and insects. Most arthropod
bites and stings are minor, with the notable exception being
bee-sting anaphylaxis. Ticks cause the most disease transmission. Key hard tick vectors include black-legged (Ixodes), dog (Dermacentor), and lone star (Amblyomma) ticks, which transmit Lyme and various
rickettsial diseases.
Insect repellents,
permethrin sprays, and proper tick inspection reduce this risk significantly.
Lyme disease and the milder
southern-tick-associated rash illness (STARI) are characterized by the
erythema migrans
rash followed, in the case of
Lyme disease, by early, disseminated, and late systemic symptoms. Treatment is with
doxycycline or
ceftriaxone. Indefinite treatment of "
chronic Lyme disease" based on subjective symptoms is not beneficial.
Rickettsial diseases include
ehrlichiosis,
anaplasmosis, and
Rocky Mountain spotted fever, which are characterized by
fever,
headache, and possible
rash and should be empirically treated with
doxycycline while awaiting laboratory confirmation.
Tularemia is a
bacterial disease (Francisella) spread by ticks and rabbits and characterized by
fever and
adenopathy. Treatment is with
gentamicin or
streptomycin.
Babesiosis is a protozoal disease, mimicking
malaria, that causes a self-limited flu-like disease in healthy hosts but can be life threatening with immune compromise. Treatment is with
atovaquone and
azithromycin. Other tick-related conditions include
viral diseases (Powassan,
Colorado tick fever, heartland virus),
tick-borne relapsing fever (Borrelia), and
tick paralysis (toxin). Mosquitoes, lice, fleas, and mites are notable for their annoying
bites but are increasingly significant disease vectors even in the United States.