Fleas

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Insect Structure and Function

Insect Life Cycles

Insecta Flashcards

Flea Structure

Flea Life Cycle

Flea Larvae - Wikimedia Commons

A thorough understanding of the flea life-cycle is important in order to be able to advise owners of adequate treatments to control flea infections on their animals and within the home environment.

The time for the egg to develop into the adult flea takes 3-4 weeks in summer

Duration of the life cycle is dependent on environmental temperature

1. Adults

Uses changes in light intensity, warmth and carbon dioxide to locate host

Once on host, the flea will usually remain
- With animals in close contact there may be a small degree of transfer between hosts
- The majority of adult fleas are acquired from the environment

The adult flea takes frequent blood meals. 97% of fleas will feed within 1 hour of finding a host and feed for about 10-25 minutes.

Flea dirt (faeces) are produced in large quantities

The life span of the flea is determined by the grooming activity of the host
- Usually the adult flea lives for between 7 and 10 days

2. Eggs

The adult lays eggs 1-2 days after locating a host

Approximately 15 eggs are layed in the coat per day

Eggs are ivory white, oval and approxiamtely 0.5mm long

The eggs drop to the ground within hours
- In reality this usually happens when the animal jumps of the sofa or makes sudden movements. Flea eggs will therefore cluster in these hot spots around the house. These areas should be paid particular attention when treating the environment in the case of a flea infestation.

3. Larvae

Larvae are small, about 2-5mm in length

Larvae are yellow/white (look like maggots) and are covered in bristles

They have chitinous mouthparts and anal struts which can be used for identification

Larvae are negatively phototropic so try to move away from light sources
- E.g. under furniture, into thick mats or carpet

Larvae feed on skin debris from other animals, flea dirt and other organic debris

High humidity is needed for survival

Freezing temperatures will kill larvae

4. Pupae

The larvae pupate forming pupae of 5mm in length

A silken cocoon surrounds the pupae
- Slightly sticky so small particles adhere to it
- These quickly become camouflaged in the environment

Methoprene, the juvenile development hormone coordinates the growth of the immature stages
- Activates genetic switches
- Determines the sequence of tissue and organ development

Newly developed adults do not leave the cocoon straight away
- The pupal window is the time that it takes for the adult to emerge
- Temperature determines when the adult fleas emerge
- Some fleas may wait several months before emerging

Newly emerged unfed adults can survive days without feeding but once they have fed, if they fall off the host they can only survive hours

Flea Habitat and Control

Habitats

Only approximately 5% of the flea population will be on the animal at any one time (and usually it is a much smaller percentage)

The rest of the population are in the environment
- E.g. Eggs, larvae, pupae and unfed adults

Fleas accumulate in certain hot spots where the animal spends the majority of its time
- E.g. Warm, shady, humid ares
- E.g. Outdoors in warmer climates or inside in temperate climates

Very large numbers of eggs are found in areas where cats land after jumping as they have been dislodged
- E.g. Beside sofas

Control

Flea Dirt - Wikimedia Commons

Single or occasional treatments will only give temporary relief from fleas as the majority of the population is in the environment

Appropriate action must be taken to stop re-infestation

The animal must be rid of its resident flea population

The animal should be protected against subsequent re-infestation
- From within the home
- From outside the home

The environmental reservoir population should be eliminated
- Animal treatment to deplete reservoir
  - Adulticides
  - Adulticides with larvicidal effects
  - Insect growth regulators (IGR's)
- Direct chemical treatment of domestic environment
  - Insecticides
  - Insect growth regulators
  - Inorganic chemicals
  - Entomophagous nematodes (These are parasitic nematodes which predate other parasite eggs)

To prevent resistance occurring, control methods should not rely solely on chemical methods
- Hygiene such as regular vacuuming and washing of the animal's bedding should also occur for the most effective treatment