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# Rickettsial infections (spotted fever)

Rickettsial infections are tick- or louse-borne bacterial fevers with a rash. Spotted fever can kill quickly unless treated early with the right antibiotic.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Skin](https://durgical.com/en/anatomy/skin/)
- [Digital arteries](https://durgical.com/en/anatomy/palmar-digital-arteries/)

## Why it happens

- [Edema and effusions: the four mechanisms](https://durgical.com/en/general-pathology/edema-and-effusions-the-four-mechanisms/)
- [Hemorrhage: petechiae, purpura, ecchymosis, hematoma, and what blood loss does](https://durgical.com/en/general-pathology/hemorrhage-petechiae-purpura-ecchymosis-hematoma-and-what-blood-loss-does/)
- [Starling forces at the capillary](https://durgical.com/en/physiology/starling-forces-at-the-capillary/)
- [Blood vessels: artery, vein and capillary layers](https://durgical.com/en/histology/blood-vessels-artery-vein-and-capillary-layers/)

## What it is

Febrile illnesses caused by intracellular bacteria of the genus Rickettsia (and related genera) that infect the lining of small blood vessels. The most important in the Americas is spotted fever from Rickettsia rickettsii, known in Colombia as fiebre de Tobia; typhus group infections are included here.

## Who gets it

Rocky Mountain spotted fever occurs across the Americas, from the United States and northern Mexico to Brazil, Argentina and Colombia. In Colombia, outbreaks of R. rickettsii infection with high case fatality have been described in Cundinamarca (Tobia), Córdoba, Antioquia and other departments, and rickettsioses are often misdiagnosed as dengue or leptospirosis. Murine typhus occurs in cities with rats and fleas.

## Causes

- Spotted fever group: Rickettsia rickettsii (ticks such as Amblyomma and the brown dog tick); other species cause milder spotted fevers
- Typhus group: R. typhi (murine typhus, rat fleas) and R. prowazekii (epidemic typhus, body lice)
- Related agents: Orientia (scrub typhus, Asia-Pacific), Ehrlichia and Anaplasma

## Risk factors

- Tick exposure in rural or peri-urban areas, farming and outdoor work
- Contact with dogs, horses or other animals that carry ticks
- Crowding and body lice (epidemic typhus), rats and fleas (murine typhus)
- Children, who carry a high share of fatal cases in some regions
- Delay in starting doxycycline

## Pathophysiology

Bacteria enter through the bite and infect endothelial cells of small vessels. Their multiplication causes vasculitis, increased vascular permeability, oedema, haemorrhage and microthrombi. This explains the rash, low albumin, low sodium, low platelets and the damage to brain, lungs, kidneys and limbs in severe disease.

## Classification

- Spotted fever group (Rocky Mountain/Brazilian/Colombian spotted fever)
- Typhus group (murine and epidemic typhus)
- Scrub typhus and related agents (ehrlichiosis, anaplasmosis)

## Symptoms and signs

- Abrupt fever, severe headache, myalgias and malaise a few days to two weeks after a bite
- Nausea, vomiting and abdominal pain, especially in children
- Rash from around day 2-5: small pink macules on wrists and ankles that spread to the trunk and often involve palms and soles, later petechial
- Some patients have no rash or it appears late
- Eschar (black scab) at the bite site in some spotted fevers and scrub typhus

## Red flags

- Confusion, seizures or stiff neck
- Hypotension, shock or reduced urine output
- Breathing difficulty from pulmonary oedema
- Bleeding, falling platelets or rapidly spreading purpuric rash
- Dark or gangrenous fingers or toes

## Diagnosis

**Clinical**
A clinical diagnosis based on fever with headache and a possible tick or animal exposure in an endemic area; treatment must start on suspicion, without waiting for laboratory results.

**Tests**
Low platelets, low sodium, raised [liver](https://durgical.com/en/anatomy/liver/) enzymes and normal or low white count are typical. Paired serology (indirect immunofluorescence) shows a fourfold rise in convalescence; PCR or immunohistochemistry of blood or a [skin](https://durgical.com/en/anatomy/skin/) biopsy can confirm early. Tests to exclude dengue, malaria and leptospirosis.

**Imaging**
Not needed for diagnosis; [chest](https://durgical.com/en/anatomy/region/chest/) X-ray when respiratory involvement is suspected.

## Differential diagnosis

- Dengue
- Leptospirosis
- Meningococcaemia
- Malaria
- Measles and other viral exanthems
- Typhoid fever

## Goal of treatment

Start doxycycline as soon as the disease is suspected, in patients of all ages, and support organ function to prevent death.

## Treatment

**Medical**
Doxycycline is the drug of choice for all ages, including children, because delay increases mortality; chloramphenicol is an alternative in special situations.

**Acute**
Hospital care for severe disease: careful fluid management (risk of pulmonary and cerebral oedema), oxygen, vasopressors and organ support in intensive care.

**Follow-up**
Nursing: vital signs, mental status, urine output, platelet count, sodium and [kidney](https://durgical.com/en/anatomy/kidney/) function; inspection of fingers and toes; ask about and check for attached ticks.

## Complications

- Encephalitis, seizures and coma
- Non-cardiogenic pulmonary oedema and respiratory failure
- Acute kidney injury
- Gangrene of fingers, toes or limbs, and limb amputation
- Disseminated intravascular coagulation and shock
- Long-term neurological sequelae

## Prognosis

Early doxycycline makes death rare; untreated R. rickettsii infection has a high case fatality, and in Colombian outbreaks many patients died. Murine typhus is usually milder.

## Prevention

- Avoiding tick-infested areas, protective clothing and repellents
- Daily body checks and prompt removal of attached ticks
- Tick control on dogs and other domestic animals
- Rodent and flea control; louse control in crowded settings

## Test yourself

Think of the answer, then tap the question to see it.

## What is the classic pattern of the Rocky Mountain spotted fever rash?

It starts on wrists and ankles, spreads centrally to the trunk and often involves palms and soles, later turning petechial.

## What is the treatment of choice for suspected spotted fever in a child?

Doxycycline, started immediately on suspicion; it is used at all ages.

## Which cell does Rickettsia infect, explaining oedema and haemorrhage?

Vascular endothelial cells of small vessels, causing vasculitis and leaky capillaries.

## What is the local Colombian name for R. rickettsii spotted fever?

Fiebre de Tobia, after the Cundinamarca locality where outbreaks were first described.

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## Related conditions

- [Dengue](https://durgical.com/en/conditions/dengue/)
- [Leptospirosis](https://durgical.com/en/conditions/leptospirosis/)
- [Malaria](https://durgical.com/en/conditions/malaria/)
- [Meningococcal disease (meningococcemia)](https://durgical.com/en/conditions/meningococcal-disease/)
- [Measles](https://durgical.com/en/conditions/measles/)
- [Typhoid (enteric) fever](https://durgical.com/en/conditions/typhoid-fever/)
- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)
- [Disseminated intravascular coagulation](https://durgical.com/en/conditions/disseminated-intravascular-coagulation/)
- [Lyme disease](https://durgical.com/en/conditions/lyme-disease/)
- [Bartonella infections (cat-scratch disease, Carrion disease)](https://durgical.com/en/conditions/bartonella-infections/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Clinical Overview of Transmission and Epidemiology | Rocky Mountain Spotted Fever (RMSF) | CDC](https://www.cdc.gov/rocky-mountain-spotted-fever/hcp/clinical-overview/index.html) (Centers for Disease Control and Prevention, 2024); [Rocky Mountain spotted fever: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000654.htm) (MedlinePlus (U.S. National Library of Medicine), 2024).

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Source: https://durgical.com/en/conditions/rickettsial-infections/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/rickettsial-infections/