Tick Borne Relapsing Fever

1/ Hi #IDFellows and #IDTwiter! Here is a Friday #IDCase: 23M Somali refugee recently arrived w/severe abd pain, confusion and fever of 41C. BP stable, HR 115. Similar symptoms occ 7d prior and resolved after 2-3d. Hgb 12.5, WBC 14, Plt 103. Mild LFT⬆️. Periph smear below 👇

2/ Which of the following is responsible for his illness?

3/ This is relapsing fever caused by Borrelia recurrentis! The image is from PMID: 32675137. B recurrentis has been associated with multiple outbreaks, particularly in settings with crowding and poor sanitation. NEJM reported a similar case in 2016

4/ Vector and epidemiology separate tick-borne relapsing fever (TBRF) from louse-borne relapsing fever (LBRF). TBRF is caused by multiple Borrelia spp and is spread by Ixodes and Ornithodoros ticks. @WuidQ did an excellent tweetorial on TBRF here

5/ Pediculus humanus, AKA the body louse, causes pediculosis (lice). There are two subspecies, P. h. capitis is assc with head lice and P. h. humanus sticks mostly on the body. LBRF inf occurs when scratching and crushing the arthropod, releasing the hemolymph into the bite!

6/ LBRF was epidemic during WWII with up to 50,000 deaths! Now it is confined mostly to Northeast Africa with cases occurring around Ethiopia and Somalia. Several cases have been associated with Somali refugees seeking asylum in European countries.


7/ Syndrome: 3d of fever approx. 7d after exposure. Fever recurs over the course of weeks. Assc symptoms include myalgias/arthralgias, headache and abd pain. The table below is from Mandell. Specific organ injury can occur. Mortality is high, up to 70%, when untreated.

8/ But why do fevers recur? These Borrelia have linear DNA plasmids that contain genes for outer membrane proteins. These are rearranged and variably expressed. When humoral response occurs, new clones with different membrane proteins emerge! PMID: 16796672

Wow Dwayne Johnson GIF

9/ LBRF can be diagnosed with a blood smear demonstrating spirochetes; sensitivity increases during febrile periods when spirochete burden is highest. Given low sensitivity of blood smear, acute and convalescent antibodies or PCR can be used for diagnosis.

10/ How would you treat this patient?

11/ Treatment is tetracycline 500 mg, Doxy 200 mg or PenG 800K U IM – LBRF can be treated in a single dose! Patients often experience acute worsening of fever, myalgias and possibly hypotension following initiation of treatment. This is due to the Jarisch-Herxheimer reaction.

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Originally tweeted by Infectious Diseases Fellows Network (@ID_fellows) on 30 October, 2020.

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