Systemic infections Flashcards
Anaplasmosis / Ehrlichiosis
Anaplasma phagocytophilum
Ehrlichia chaffeensis
Gram negative.
Tick-borne transmission via deer (Ixodes and Amblyomma).
Intracellular rods that replicate in vacuoles.
Neither have LPS or peptidoglycan!
Anaplasmosis and Ehrlichiosis cause a granulocytic disease. They invades neutrophils and alters their function substantially (Ehrlichiosis also targets monocytes).
Endemic to: East coast. Lifecycle involves deer hosts.
Symptoms: After 1-2 weeks. Causes fever, headache, anorexia, leukopenia, thrombocytopenia, anemia. Variable symptoms, ranging from asymptomatic to life-threatening.
Diagnosis: Morulae in neutrophils seen on blood smear.
Tx: Oral doxycycline (also covers Lyme disease).
Rifampin is an alternative (does not cover Lyme disease).
Rocky Mountain spotted fever
Rickettsia rickettsia
Gram negative.
Tick-borne transmission via rodent (Dermacentor).
Intracellular coccobacilli that replicate in cytosol.
Polymerizes actin to move from cell to cell in epithelium.
Endemic to: Entire USA. Lifecycle involves rodent hosts. Transovarial transmission means tick larvae are born infected.
Symptoms: After 2-14 days. Petechial rash after 3-5 days. Thrombocytopenia, pro-coagulant coagulopathy, leukopenia, hyponatremia.
Diagnosis: No conclusive test. History is key. Tick bites and tick season are risk factors.
Tx: Oral doxycycline (not other tetracyclines). If allergic or pregnant, use chloramphenicol.
Lyme disease
Borrelia burgdorferi
Gram negative. Tick-borne transmission via deer (Ixodes). Extracellular spirochetes. No LPS. Antigenic variation, complete evasion.
Endemic to: Eastern USA. Most common vector-borne disease in northern
Symptoms: Red bull’s eye (erythema migrans >5 cm) during first 2 weeks. After days to months, fever, myalgia, palsy, AV node block, arthralgia. After months to years, arthritis, encephalopathy.
Diagnosis: ELISA, WB. Observing EM is sufficient.
Tx: doxycycline. If pregnant or if a child, use amoxicillin. For CNS involvement, use ceftriaxone.
Syphilis
Treponema pallidum
Human only pathogen. STD.
Gram negative spirochetes.
Three phases:
Primary – 10-90 days after encounter. Painless lesion, highly infectious, regional lymphadenopathy.
Secondary – 6wk-6mo after encounter. Diffuse, non-itchy rash on body and palms/soles. Myalgia and arthralgia. Fever. Can remain latent (non-symptomatic) for years.
Tertiary – Gumma (fibrous granulomas that destroy bone and skin), neurosyphilis, cardiovascular syphilis, tabes dorsalis (demyelination of spinal cord sensory and motor tracts, painful).
Can be transmitted congenitally. Symptoms are failure to thrive, fever, saddle nose, rash, peg-shaped teeth, deafness, blindness, joint swelling.
Diagnosis: anti-cardiolipin test (not very specific). Serology is a better choice.
Tx: Penicillin. Alternatives are ceftriaxone, erythromycin, doxycycline.
