[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Arthropod vectors](https://durgical.com/en/microbiology/groups/arthropod-vectors/) › Amblyomma, Rhipicephalus and Ornithodoros

# Amblyomma, Rhipicephalus and Ornithodoros

- Parasite
- Exam priority: high

Ticks are blood-feeding mites that stay attached for days. They carry spotted fever, Lyme disease and more; quick, correct removal matters.

Updated Nov 13, 2026

Also called: ticks, garrapatas, brown dog tick (Rhipicephalus sanguineus), soft ticks (Ornithodoros)

## Quick facts

**Type**
Parasite · [Arthropod vectors](https://durgical.com/en/microbiology/groups/arthropod-vectors/)

**Gram / shape**
Oval body without segments

**Spread**
Hard ticks climb vegetation

**Causes**
Spotted fever rickettsioses · Lyme disease

**Treatment**
Remove the tick at once with fine-tipped tweezers

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- Life cycle
- In Colombia
- Memory aid
- What the colours mean

- Clinical Virulence factors
- Diseases it causes
- Clinical picture
- Diagnosis

- Treatment Treatment
- Prevention

- Study Test yourself

- Connections Connections

## Key points

- Hard ticks stay attached for days; remove them early and correctly.
- Fever and rash after a tick bite: start doxycycline at any age without waiting for tests.
- Colombia: spotted fever by R. rickettsii, historic Tobia outbreak; Amblyomma patinoi in Villeta.
- Tick paralysis: ascending flaccid paralysis that resolves after removal; search the scalp.
- Ornithodoros soft ticks: relapsing fever, brief night bites.
- Ixodes: Lyme disease, babesiosis, anaplasmosis.

## At a glance

**Shape**
Oval body without segments; hard ticks have a dorsal shield (scutum) and forward mouthparts; soft ticks are leathery with mouthparts underneath

**Family**
Ixodidae (hard ticks: Amblyomma, Rhipicephalus, Dermacentor, Ixodes); Argasidae (soft ticks: Ornithodoros)

**Type**
Arachnids (Acari), obligate blood-feeding ectoparasites and vectors

**Size**
Larvae under 1 mm; engorged adult females up to about 1 cm or more

## Morphology

- Larvae have 6 legs; nymphs and adults have 8, as in all arachnids.
- The hypostome has backward teeth and is cemented into the skin, so hard ticks stay attached for days.
- Soft ticks feed for minutes to an hour, usually at night, and hide in nests, cracks and burrows.

## Transmission

- Hard ticks climb vegetation and wait for a passing host (questing), then attach in protected skin folds.
- Pathogens pass in saliva during feeding; the longer the attachment, the higher the risk for many infections.
- Some ticks pass pathogens to their eggs, so even larvae can be infected.
- Soft ticks bite briefly at night inside houses, caves or animal shelters; bites are often painless and unnoticed.

**Reservoir:** Wild and domestic mammals: rodents, dogs, cattle, horses, capybaras; Ticks themselves, which can stay infected through their stages and to their eggs

**Vector:** Amblyomma and Rhipicephalus carry spotted fever rickettsiae; Ixodes carries Borrelia burgdorferi, Babesia and Anaplasma; Ornithodoros soft ticks carry tick-borne relapsing fever Borrelia.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The engorged female drops to the ground and lays thousands of eggs, then dies.
- Six-legged larvae hatch, climb vegetation and take a first blood meal.
- The larva drops off, moults into an eight-legged nymph and feeds again.
- The nymph moults into an adult; females take a large final meal and mate.
- Many hard ticks use a different host for each stage (three-host ticks); Rhipicephalus sanguineus may complete it on dogs indoors.
- Soft ticks go through several nymph stages and feed many times, briefly, living for years.

## Virulence factors

- Saliva contains anaesthetic, anticoagulant and immune-dampening substances, so the bite is often unnoticed.
- Cement and toothed mouthparts keep the tick attached for days, which gives time for transmission.
- A neurotoxin in the saliva of some attached ticks causes tick paralysis.
- Mouthparts left in the skin can cause a granuloma that lasts months.

## Diseases it causes

- Spotted fever rickettsioses, including Rocky Mountain (Colombian) spotted fever by Rickettsia rickettsii [Rickettsial infections (spotted fever) →](https://durgical.com/en/conditions/rickettsial-infections/)
- Lyme disease (Borrelia burgdorferi, Ixodes ticks) [Lyme disease →](https://durgical.com/en/conditions/lyme-disease/)
- Tick-borne relapsing fever (Ornithodoros soft ticks) [Relapsing fever (tick-borne and louse-borne borreliosis) →](https://durgical.com/en/conditions/relapsing-fever/)
- Babesiosis [Babesiosis →](https://durgical.com/en/conditions/babesiosis/)
- Tularaemia [Tularaemia →](https://durgical.com/en/conditions/tularaemia/)
- Ehrlichiosis and anaplasmosis
- Tick paralysis: ascending flaccid weakness from a toxin in the saliva of an attached tick

## Clinical picture

- Painless bite; a red papule or small eschar at the site; in children, look on the scalp, behind ears and in folds.
- Fever, headache and rash within two weeks of a tick bite: think of rickettsiosis and treat early.
- Tick paralysis: ascending weakness over hours to days that mimics Guillain-Barré syndrome or botulism; it resolves soon after the tick is removed.
- Relapsing fever: recurring fever episodes separated by days without fever.

## Diagnosis

- Identify the tick (genus) if it was kept; testing the tick is not used to decide treatment.
- Search the whole body, including the scalp, for an attached tick in any child with ascending paralysis.
- Spotted fever: diagnosis is clinical first; paired serology or PCR confirm later.
- Relapsing fever: spirochaetes seen in blood smears taken during fever.

## Treatment

Remove the tick at once with fine-tipped tweezers: grasp it close to the skin, pull straight out with steady pressure, then clean the area; do not use heat, petroleum jelly or nail polish. Doxycycline is the drug of choice for suspected rickettsial disease at any age; tick paralysis improves after removal.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Prevention

- Long, light-coloured clothes tucked into socks in pasture and forest; repellents on skin and permethrin-treated clothing.
- Daily full-body tick checks after field work, including children's scalp and skin folds.
- Tick control on dogs, cattle and horses, and in kennels and houses.
- Seal cracks and rodent nests in houses to keep out soft ticks.

## In Colombia

Rocky Mountain spotted fever (fiebre de Tobia) was described in Tobia, Cundinamarca, in the 1930s, with very high fatality. Rickettsia rickettsii was isolated from Amblyomma patinoi ticks in Villeta, Cundinamarca, and this tick is considered its main vector to humans there.

## Memory aid

Pull, don't burn: a tick lifted straight out with tweezers ends the bite and, if it was paralysing, the paralysis too.

## Test yourself

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

## How should an attached tick be removed?

Grasp it with fine-tipped tweezers close to the skin and pull straight out with steady pressure, then clean the area; no heat, oils or nail polish.

## Which drug is used for suspected spotted fever, including in children?

Doxycycline, started early on clinical suspicion without waiting for laboratory confirmation.

## A child develops ascending flaccid weakness over two days. Which simple examination can change everything?

A full skin and scalp search for an attached tick: tick paralysis resolves after the tick is removed.

## Which tick is considered the main vector of R. rickettsii to humans in Villeta, Colombia?

Amblyomma patinoi, a member of the Amblyomma cajennense complex.

## Which disease do Ornithodoros soft ticks transmit?

Tick-borne relapsing fever, caused by Borrelia species.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/microbiology/amblyomma-rhipicephalus-and-ornithodoros/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

## Connections

## Related 8

- [Rickettsia rickettsii / Rickettsia typhi](https://durgical.com/en/microbiology/rickettsia-rickettsii-rickettsia-typhi/)
- [Borrelia burgdorferi](https://durgical.com/en/microbiology/borrelia-burgdorferi/)
- [Borrelia recurrentis and tick-borne relapsing fever borreliae](https://durgical.com/en/microbiology/borrelia-recurrentis-and-tick-borne-relapsing-fever-borreliae/)
- [Babesia spp.](https://durgical.com/en/microbiology/babesia-spp/)
- [Ehrlichia / Anaplasma](https://durgical.com/en/microbiology/ehrlichia-anaplasma/)
- [Francisella tularensis](https://durgical.com/en/microbiology/francisella-tularensis/)
- [Coxiella burnetii](https://durgical.com/en/microbiology/coxiella-burnetii/)
- [Trombicula, Cheyletiella and bird mites](https://durgical.com/en/microbiology/trombicula-cheyletiella-and-bird-mites/)

## Related conditions 5

- [Rickettsial infections (spotted fever)](https://durgical.com/en/conditions/rickettsial-infections/)
- [Lyme disease](https://durgical.com/en/conditions/lyme-disease/)
- [Relapsing fever (tick-borne and louse-borne borreliosis)](https://durgical.com/en/conditions/relapsing-fever/)
- [Babesiosis](https://durgical.com/en/conditions/babesiosis/)
- [Tularaemia](https://durgical.com/en/conditions/tularaemia/)

[← Back to the group: Arthropod vectors](https://durgical.com/en/microbiology/groups/arthropod-vectors/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [About Ticks and Tickborne Disease | Ticks | CDC](https://www.cdc.gov/ticks/about/index.html) (CDC, 2025); [What to Do After a Tick Bite | Ticks | CDC](https://www.cdc.gov/ticks/after-a-tick-bite/index.html) (CDC, 2025); [About Rocky Mountain Spotted Fever | Rocky Mountain Spotted Fever (RMSF) | CDC](https://www.cdc.gov/rocky-mountain-spotted-fever/about/index.html) (CDC, 2025); [Rickettsia rickettsii in Amblyomma patinoi Ticks, Colombia](https://wwwnc.cdc.gov/eid/article/21/3/14-0721) (Emerging Infectious Diseases (CDC), 2015).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/microbiology/amblyomma-rhipicephalus-and-ornithodoros/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/amblyomma-rhipicephalus-and-ornithodoros/