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Diagnosis of Rickettsial Diseases

Updated: Jan 28, 2022

By Umar Mohammad

December 4, 2021

Updated 12:00 PM EST

[Photo Credit: CDC]

What is it?

Rickettsial diseases are caused by a variety of bacteria from the order Rickettsiales - a taxonomic term used to classify organisms. These bacteria are transferred through their primary vector, usually ticks, and like with most diseases, their severity is dependant upon their geographical region and season (usually spring and summer). Their effects are quite significant, considering the vulnerability of the public, regardless of age, or low-cost antibacterial treatment. Their symptoms are also akin to other diseases, which makes it quite the challenge during diagnosis.

Types of Rickettsial diseases:

  • Rocky Mountain Spotted Fever (Rickettsia rickettsii) This disease is caused by the American dog tick (Dermacentor variabilis), the brown dog tick (Rhipicephalus sanguineus), and the Rocky Mountain wood tick (Dermacentor andersoni). Although it isn’t contagious, a delay in antibiotic treatment could seriously harm one’s organs. Symptoms can include headaches, high temperatures, paining joints/muscles, nausea, and red rashes around the wrists and ankles. It’s widespread in the US and has an incubation period of 2-14 days. Its fatality rate is 5-10 percent.

  • Rickettsiosis This particular disease is caused by the Gulf Coast tick and is a form of spotted fever, whereby rashes are formed. It is akin to the Rocky Mountain Spotted Fever in terms of symptoms but isn’t as detrimental. The slight difference in symptoms is that Rickettsiosis has a scab where the tick attached itself to its host.

  • Human monocytic ehrlichiosis (Ehrlichia chaffeensis) The tick that causes this one is the Lone star tick (Amblyomma americanum). The incubation period of this disease is about 5-14 days, and again, akin to its ‘siblings’ it has similar symptoms. However, the fatality rate is significantly lower, at around 2%.

All the diseases have the same treatment which is a certain amount (depending on age and weight) of doxycycline, twice in one day. There is no vaccine available against rickettsial infections. The general preventative measure advised by experts is to wear long-sleeved protective clothing, along with a broad-brimmed hat during high-risk activities, such as trekking or camping (depending on the region). Avoid tick habitats. Ticks usually live in higher altitudes, woody and grassy areas with a variety of hosts. These organisms reside in mice too so anything that attracts mice will eventually bring in ticks. As most insects do, they prefer damp, dark, humid environments with food sources (potentially you).


[1] Biggs, Holly M., et al. “Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States.” MMWR. Recommendations and Reports, vol. 65, no. 2, 13 May 2016, pp. 1–44

‌ [2] Randel, Amber. “Guidelines for the Diagnosis and Treatment of Tick-Borne Rickettsial Diseases.” American Family Physician, vol. 76, no. 1, July 2007, p. 137,

[3] Bonvissuto, Danny. “What Are Rickettsial Diseases?” WebMD, WebMD, 27 June 2018,

[4] SA, Adelaide. “Rickettsial Infections - Including Symptoms, Treatment and Prevention | SA Health.”, 2021,

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