[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/) › Pulex, Xenopsylla and Ctenocephalides

# Pulex, Xenopsylla and Ctenocephalides

- Parasite
- Exam priority: medium

Small jumping insects that feed on blood. Their bites itch, and some carry plague and flea-borne typhus or a dog tapeworm.

Updated Nov 13, 2026

Also called: fleas, pulgas, human flea (Pulex irritans), oriental rat flea (Xenopsylla cheopis), cat and dog fleas (Ctenocephalides)

## Quick facts

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

**Gram / shape**
Brown body flattened from side to side

**Spread**
Plague · Flea-borne typhus · Dipylidium

**Causes**
Plague · Flea-borne · Dipylidiasis in young children

**Treatment**
Does not apply to the insect itself

On this page

- The basics Key points
- At a glance
- Morphology
- Transmission
- Life cycle
- 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

- Xenopsylla cheopis: plague and flea-borne typhus.
- Plague: blocked flea regurgitates Y. pestis into the bite.
- Flea-borne typhus: R. typhi in flea faeces; doxycycline.
- Ctenocephalides: intermediate host of Dipylidium; children swallow the flea.
- Flea bites in children: papular urticaria on the legs.

## At a glance

**Shape**
Brown body flattened from side to side, long jumping hind legs; Ctenocephalides has comb-like spines on the head

**Family**
Pulicidae

**Type**
Wingless blood-feeding insects (Siphonaptera); ectoparasites and vectors

**Size**
About 1–4 mm

## Morphology

- Side-to-side flattening lets the flea move between hairs; backward spines anchor it.
- Xenopsylla has no combs; Ctenocephalides has head and thoracic combs; Pulex has none and a rounded head.
- Adults of both sexes feed on blood; larvae are blind, legless and do not bite.

## Transmission

- Plague: a flea that fed on an infected rodent has its gut blocked by Yersinia pestis and regurgitates bacteria into the next bite.
- Flea-borne typhus: Rickettsia typhi is passed in flea faeces (flea dirt) rubbed into the bite or other skin breaks, or onto mucosa.
- Dipylidium: a child swallows an infected flea while playing with a dog or cat.
- Fleas jump from animals or infested floors onto people; there is no person-to-person spread of these infections by contact.

**Reservoir:** Rats and wild rodents (plague, flea-borne typhus); Cats, dogs and opossums (cat flea); Human dwellings with earthen floors and animals (human flea)

**Vector:** Xenopsylla cheopis is the classic vector of plague and flea-borne typhus; the cat flea Ctenocephalides felis also carries R. typhi and is the intermediate host of Dipylidium caninum.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The female lays eggs on the host; they fall off into bedding, carpets, nests and soil.
- Larvae hatch in days and feed on organic debris and the dried blood in adult flea faeces.
- After moulting twice, the larva spins a cocoon and pupates.
- The adult waits in the cocoon until vibration, warmth or carbon dioxide signal a host, then emerges.
- Adults feed on blood within hours; cycle length depends on temperature and humidity, from weeks to months.
- Flea larvae that eat Dipylidium eggs carry the cysticercoid into adulthood.

## Virulence factors

- Flea saliva causes itchy papules and hypersensitivity reactions (pulicosis, papular urticaria).
- Gut blockage by Y. pestis makes the flea hungry and bite repeatedly, spreading plague.
- Fleas stay infected with R. typhi for life.
- Cocooned pupae survive empty houses for months, so infestations return when people move back in.

## Diseases it causes

- Plague (Yersinia pestis) [Plague →](https://durgical.com/en/conditions/plague/)
- Flea-borne (murine) typhus (Rickettsia typhi) [Rickettsial infections (spotted fever) →](https://durgical.com/en/conditions/rickettsial-infections/)
- Dipylidiasis in young children (Dipylidium caninum)
- Pulicosis: itchy bites and papular urticaria
- Tungiasis is caused by another flea, Tunga penetrans [Tungiasis and furuncular myiasis →](https://durgical.com/en/conditions/tungiasis-and-furuncular-myiasis/)

## Clinical picture

- Groups of itchy red papules, often on the ankles and lower legs, sometimes with a central bite point.
- Papular urticaria: recurrent crops of itchy papules in children sensitised to flea bites.
- Flea-borne typhus: fever, headache and body aches; rash in about half of patients; few remember a flea bite.

## Diagnosis

- Identifying fleas from pets, bedding or rodents by combs and head shape.
- Flea dirt (dark specks that turn red on wet paper) on pets or bedding.
- Flea-borne typhus: serology for R. typhi; treatment starts without waiting for results.
- Dipylidium: rice-like moving proglottids in a child's stool or nappy, with egg packets.

## Treatment

Does not apply to the insect itself. Bites are treated with topical corticosteroids and oral antihistamines; flea-borne typhus with doxycycline; plague with aminoglycosides, fluoroquinolones or doxycycline started early; dipylidiasis with praziquantel.

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

In Pharmacology:

- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)
- [Streptomycin](https://durgical.com/en/pharmacology/streptomycin/)
- [Gentamicin](https://durgical.com/en/pharmacology/gentamicin/)
- [Praziquantel](https://durgical.com/en/pharmacology/praziquantel/)
- [Hydrocortisone](https://durgical.com/en/pharmacology/hydrocortisone/)
- [Cetirizine](https://durgical.com/en/pharmacology/cetirizine/)

## Prevention

- Treat pets with veterinary flea-control products and wash their bedding.
- Vacuum floors and furniture often to remove eggs, larvae and pupae.
- Rodent control and keeping wildlife away from homes; do not handle dead rodents without gloves.
- Repellents during outdoor work in plague or typhus areas.

## Memory aid

The rat flea brings the black death and the spotted fever; the cat flea brings a tapeworm to the toddler on the sofa.

## Test yourself

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

## How does a flea transmit plague?

Y. pestis blocks the flea's gut, so when it bites it regurgitates bacteria into the wound; it also bites more often because it stays hungry.

## How is Rickettsia typhi passed from flea to person?

In flea faeces that are rubbed into the bite or other skin breaks, or reach the eyes or airways.

## How does a child acquire Dipylidium caninum?

By swallowing a dog or cat flea that carries the cysticercoid, usually while playing with pets.

## Which flea is the classic vector of plague?

The oriental rat flea, Xenopsylla cheopis.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/microbiology/pulex-xenopsylla-and-ctenocephalides/)

## 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 6

- [Yersinia](https://durgical.com/en/microbiology/yersinia/)
- [Rickettsia rickettsii / Rickettsia typhi](https://durgical.com/en/microbiology/rickettsia-rickettsii-rickettsia-typhi/)
- [Dipylidium caninum](https://durgical.com/en/microbiology/dipylidium-caninum/)
- [Tunga penetrans](https://durgical.com/en/microbiology/tunga-penetrans/)
- [Pediculus humanus and Pthirus pubis](https://durgical.com/en/microbiology/pediculus-humanus-and-pthirus-pubis/)
- [Cimex lectularius and Cimex hemipterus](https://durgical.com/en/microbiology/cimex-lectularius-and-cimex-hemipterus/)

## Related conditions 3

- [Plague](https://durgical.com/en/conditions/plague/)
- [Rickettsial infections (spotted fever)](https://durgical.com/en/conditions/rickettsial-infections/)
- [Tungiasis and furuncular myiasis](https://durgical.com/en/conditions/tungiasis-and-furuncular-myiasis/)

[← 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 Plague | Plague | CDC](https://www.cdc.gov/plague/about/index.html) (CDC, 2024); [About Flea-borne Typhus](https://www.cdc.gov/typhus/about/murine.html) (CDC, 2025); [CDC - DPDx - Dipylidium caninum](https://www.cdc.gov/dpdx/dipylidium/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/pulex-xenopsylla-and-ctenocephalides/