Vector Borne Diseases

Rickettsia

Gram (-), minimal peptidoglycan, obligately intracellular parasites found in cytoplasm, phagocytosis, phagosome.

Rickettsia rickettsiii

Vector: Various hard ticks, in the US primarily: American Dog, brown, and wood tick. Host: wild rodents. Range: N and Central America.

Identification: mricoimmunofluroscence (MIF) test, immunofluorescence antibody(IFA) assay.

Rocky Mountain Spotted Fever

Sym: Early: fever headache, nausea, vomiting, anorexia. Late: coma, cerebral edema, necrosis of extremities, multiorgan failure.

Prog: 20-30% w/o treatment, 6.2% after first 3 days, 1.3% begun by 3rd day,

Epidemiology: delayed treatment, children < 10 years, persons with G6PD deficiency

Rickettsia prowazekii

Vector: human body louse, squirrel fleas or lice. Hosts: humans, southern flying squirrels.

Range: world-wide where there is clustering of large populations in unhygienic.

Identification: primarily by serology: IFA or IHC.

Epidemic (louse borne) typhus

Sym: fever, chills rash, cough, vomiting, altered mental status, coma, and seizures.

Prognosis: untreated mortality 20-60%.

Epidemiology: Transmitted person ot person via the human body louse.

Brill-Zinsser disease

Reoccurrence of typhus months or years after treatment. Due to reactivation of dormant ricketssia in the tissues during times of stress.

Generally less severe and rarely fatal. Contagious.

Ehrlichia and Anaplasma

Intracellular bacteria that parasitize granulocytes, monocytes, red blood cells and platelets. Remain within the phagocytic vesicle.

Two distinct forms: Small bodies and larger bodies.

Ehrlichia chaffeensis

Vector: Lone Star Tick. Host: White-tailed deer. Range: Eastern United States.

Identification: PCR, immunofluorescent antibody test for IgG.

Human Monocytic Ehrichiosis

Sym: fever, chills, headache, bleeding, muscle pain, organ failure, rash.

Prognosis: 2-5% mortality, most cases are asymptomatic.

Epidemiology: very rarely transmitted through transfusions or organ transplant.

Anaplasma phagocytophilum

Vector: blacklegged tick and western. Host: white-footed mouse. Range: Northeast and upper MIdwest. Also found worldwide.

Identification: PCR, immunofluorescent antibody test fo IgG.

Human Granulocytic Anaplasmosis

Sym: fever, chills, severe headache, loss of appetite, vomiting, diarrhea, progressing to renal or respiratory failure.

Prognosis: <1%. Epidemiology: very rarely transmitted by blood transfusions. Older ager and Immnosuppression with poorer outcomes.

Coxiella burnetii

Weakly staining Gram (-) intracellular rod shaped bacteria. 2 variants: small cell and large cell.

Range: worldwide. Identification: IFA test. US Select Agent.

Acute Q Fever

Sym: fever, chills or sweats, fatigue, pregnancy loss, low infant birth weight, chest pain.

Prog: 50% asymptomatic, <5% symptomatic require hospitalization.

Epidemiology: At risk: veterinarians, meat processing plant workers, dairy workers.

Chronic Q Fever

Sym: occurs months to years, osteomyelitis, vascular infection, chronic hepatitis

Prog: <5% mortality with modern treatment, fatal w/o treatment, long term antibiotic.

Epidemiology: occurs in patients with predisposing conditions. (pregnancy, heart disease)