Lesson 3 (Fleas & Tree Bugs)

Fleas (Siphonaptera) and True Bugs (Hemiptera)

Characteristics of Order Siphonaptera (Fleas)

• Siphonaptera means "tube wingless" (Siphon- = "tube", "-aptera" = "wingless").

• Small, wingless, and laterally flattened with a large abdomen.

• Mouthparts are designed for piercing and sucking.

• Both male and female fleas are blood feeders.

• Possess long and strong legs with the 3rd pair being the longest.

• Have a Holometabolous (complex) life cycle.

• Fleas are pathogenic in their own right and some can biologically vector pathogens.

Structural Features for Identification

• Genal Ctenidia/Combs: Dark spines on the ventral aspect of the head.

• Pronotal Ctenidia/Combs: Dark spines on the posterior aspect of the prothorax.

Sexual Dimorphism

• Females: Larger with rounded ventral and dorsal surfaces.

• Males: Flatter dorsal surface, greatly curved ventral surface; possess a coiled copulatory structure called aedeagus in the abdomen.

General Life Cycle

• Eggs: Laid on nests, beddings, or ground.

• Larvae (3 instars): Maggot-like with chewing mouthparts, feed on blood-filled feces of adult fleas and organic debris.

• Pupa: Exarate-type, covered by a silk-like cocoon.

• Adult females can start developing eggs after the 1st blood meal.

Life Cycle Trends by Family

• Family CERATOPHYLLIDAE: Infrequent and brief associations with the host; adults move between host to feed and back to nests to lay eggs.

• Family PULICIDAE: Adult fleas have prolonged association with the host; eggs are laid on the host and drop off later.

Flea Dirt

• "Flea dirt" is dark reddish-brown colored, blood-filled feces of fleas, found on the skin/fur and beddings of infested animals.

Family CERATOPHYLLIDAE

• Members spend more time in the nest/beddings of their host and feed only for short periods.

• Characterized by having no genal combs, but have many pronotal combs.

Common Genera

• Ceratophyllus

• Nosopsyllus

Ceratophyllus gallinae (Chicken Flea)

• Hosts: Domesticated poultry, wild birds.

• Pronotal combs: >24

• Elongated body.

• Spends more time in the nest of their hosts, feeds only for short periods.

• Not known to vector pathogens but are pathogenic in their own right.

Nosopsyllus fasciatus (Northern Rat Flea)

• Hosts: Rodents, humans.

• Pronotal combs: 18-20

• Elongated body.

• Cosmopolitan ectoparasite of rodents.

• Can vector Rickettsia typhi (murine typhus) and possibly Yersinia pestis (black plague).

Family PULICIDAE

• Parasitizes a wide range of mammals and has a worldwide distribution.

Common Species

• Ctenocephalides spp.

• Spilopsyllus cuniculi

• Echidnophaga gallinacae

• Pulex irritans

• Xenopsylla cheopis

• Tunga penetrans

Ctenocephalides felis felis (Cat Flea) & Ctenocephalides canis (Dog Flea)

• Hosts:

  • Both are intermediate hosts (IH) of Dipylidium caninum (via accidental ingestion).

  • Ctenocephalides felis felis transmits Rickettsia typhi (typhus) and Bartonella henselae (Cat-scratch fever).

Distinguishing Features of Ctenocephalides Species

Flea Allergy Dermatitis

Spilopsyllus cuniculi (Rabbit Flea)

• Pronotal combs present.

• Genal combs: 4-6 (directed obliquely).

• Rounded frons w/ tubercle.

• Hosts:

  • Life cycle is mediated by hormones of the rabbit host (population of rabbit fleas increases during breeding season).

  • Transmits Francisella tularensis (tularemia).

Echidnophaga gallinacea (Sticktight Flea)

• No pronotal or genal combs.

• Angled frons.

• Hosts:

  • Often found on the head, comb, or wattles of poultry (or any area of the body that is towards sunlight), causing ulcerations.

  • Females tend to burrow on the skin and form nodules.

Pulex irritans (Human Flea)

• Hosts:

  • IH of Dipylidium caninum (via accidental ingestion).

  • Eggs are usually laid in the environment rather than on the host. If the host dies, the flea moves immediately to find a new one.

Xenopsylla cheopis (Oriental Rat Flea)

• Hosts:

  • Transmits Yersinia pestis (Bubonic/Black Plague).

Distinguishing Features of Pulex irritans and Xenopsylla cheopis

Tunga penetrans (Jigger/Chigoe)

• Hosts:

  • Females slash the skin of the host and burrow into the wound, leaving only the last abdominal segments on the skin surface.

  • The host skin proliferates during healing (producing a nodule) and covers the flea except the last abdominal segment.

Prevention and Control of Fleas

• Spot-on treatments (Fipronil, Imidacloprid, Nitempyram) or oral anti-flea medication (Selanomectin) will prevent adults from jumping on the host.

• Vacuuming to reduce eggs, larvae, pupae, and unfed adults in the environment.