View source for Anaplasma phagocytophilum

* Causes '''human granulocytotropic anaplasmosis'''

== Background ==
=== Microbiology ===
* Small, obligate intracellular Gram-negative bacterium
* Related to ''[[Ehrlichia]]'' and ''[[Rickettsiae]]''
* Tropism for neutrophils

== Epidemiology ==
* Transmitted by ''[[Ixodes scapularis]]'' and ''[[Ixodes pacificus]]'' ticks

== Clinical Presentation ==
* Incubation period of 1 to 2 weeks
* Usually an acute undifferentiated fever
* Can be mild or severe
* Fever, headache, malaise, and myalgias are common
* Can also cause nausea, vomiting, diarrhea, cough, arthralgias, nuchal rigidity, and confusion
* Less than 10% have rash, most of which is concurrent Lyme disease
* 36% of cases require hospitalization, and it is severe in 3 to 7%
* Severe complications include respiratory failure, septic shock, rhabdomyolysis, hemorrhage, and opportunistic infections
** Rare meningoencephalitis
* Higher case-fatality rate in Shandong Province in China, for no clear reason (16% versus 2.6%)
* Thrombocytopenia, lerkopenia, and mild anemia are common
** Return to normal range within 14 days, but with persistent left shift
* Abnormal liver enzymes are common in the first 7 days

== Diagnosis ==
* 20-80% of patients will have circulating neutrophils with detectable '''morulae''' on blood film (in neutrophils/granulocytes)
* Serology used to diagnose, by measuring IgG levels ≥1:64 or a fourfold rise
** IgM testing less sensitive and specific
* Culture not done routinely
* PCR possible

== Management ==
* Doxycycline 100 mg po bid

{{DISPLAYTITLE:''Anaplasma phagocytophilum''}}
[[Category:Rickettsioses]]