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1. Session 4: Insecta of Medical
Importance - Siphonaptera
[Fleas

2. Learning Objectives
By the end of this session, students are expected
to be able to:
• Describe general characteristics of fleas
• Describe fleas of medical importance and
disease they cause
• Describe life cycle of fleas
• Describe control measures of fleas

3. Definition and General Characteristics
of Fleas
• Fleas are small wingless insects 2.0-2.5 mm which feed
on the blood of mammals and birds.
• Adults feed on their host while larvae live on any
nutritive debris, particularly dried blood and the faeces
of adult fleas
• The females ingest more blood than males.
• Fleas occur in a wide range of host including
domesticated animals.
• They are brown in colour with laterally compressed
bodies.
• The males are smaller than the females.

4. Cont..
• The small chintinous head may bear eyes and; all
have antennae and suctoral mouth parts.
• Each segment of the three-segmented thorax
bears a pair of powerful legs terminating in two
curved claws.
• Fleas are powerful jumpers and can jump from
one host to another.
• Copulate frequently to be able to produce large
numbers of eggs.
• Life span is about 1year.

5. CATEGORIES OF FLEAS
1.Combless fleas
• Pulex species (P. irritant & P. simulans)
• Xenopsylla spp. (X. cheopis, X. brasiliensis, X. astia)
• Tunga penetrans (Chigoe, Jigger, Nigua). Sometimes are
known as Sand flea or Burrowing flea.
2.Combs fleas
• Leptopsylla segnis
• Ctenocephalides spp. (C. canis, C. felis)
• Nosopsyllus fasciatus

6. Pullex irritants

8. Combs fleas
• Possess a pronotal prothoracic comb but lacks
a genal comb
• Originally Europe and in tropics
• Are the parasite of rats

9. Cont….
• It does not bite man readily
• Possess both pronotal and genal comb
• Are the parasites of dogs & cats –
Ctenocephalides spp. and parasites of mouse
and rat – Leptopsylla segnis
• May be ingest eggs of Diphyllidium caninum -
Ctenocephalides spp.

10. Ctenophalides felis and Ctenophalides
canis
• Genal and pronotal comb
of C.canis
• Genal and pronotal
comb of C.felis

11. Cont…

12. Fleas of Medical Importance and
Disease they Cause
• The medically important fleas belong to three
general category; Pulex, Xenopsylla and Tunga
Examples of species and the diseases they
cause in each genera.
o Pulex Irritans
• It is a nuisance insect of man which
occasionally plays a minor role in the
transmission of diseases.
• It causes discomfort and irritation

13. Tunga penetrans
• Tunga penetrans (jigger flea or chigoe)
• The female penetrates into the tissues of the
human host and becomes a jigger.
• A jigger can lead to various physical discomfort,
disability and other medical conditions (like
tetanus, and nerve damage).
o Xenopsylla Species
• Are responsible for the transmission of plague
and murine typhus.

14. Life Cycle of Fleas
• Fleas have a four-part life cycle consisting of
eggs, larvae, pupae, and adults.
• However, the chigoe flea (Tunga penetrans)
has different life cycle

15. Life Cycle of Pulex and Xenopsylla
Species
• Life Cycle of Pulex and Xenopsylla Species
below.
• Eggs are shed by the female in the
environment .
• Eggs hatch into larvae in about 3-4 days and
feed on organic debris in the environment.
• The number of larval instars varies among the
species.
• Larvae eventually form pupae .

16. Cont…
• The larval and pupal stages take about 3-4 weeks
to complete.
• Afterwards, adults hatch from pupae and seek out
a warm-blooded host for blood meals.
• The primary hosts for Ctenocephalides felis and
Ctenocephalides canis are cats and dogs,
respectively, although other mammals, including
humans, may be fed upon.
• The primary hosts for Xenopsylla cheopis are
rodents, especially rats.
• Humans are the primary host for Pulex irritans

17. Life Cycle of Pulex and Xenopsylla
Species

18. Eggs:
• Are small, ovoid, white or cream coloured
• Laid in hairs or in the habitat of the host.
• Are deposited in small batches under rugs, in
floor cracks, or on the ground near under
buildings. Those deposited on the host usually
drop off before hatching
• Hatch to form larva.

19. Larvae:
• Emerges from eggs as an active wormlike
within 2 – 12 days
• Are white, eyeless, it has a sucking mouth
• Takes 7 – 30 days during which time
undergoes 2 -3 molts.
• The last changes being within the Cocoon.
• May die at 36⁰c for 24 hours.
• Feed on dried blood and human faeces

20. Cont…

21. Pupae:
• Within the Cocoon lasts in 14 – 21days but at
low temperature may extend over a year
• When the development completed the adult
breaks out of the cocoon

22. Adult
• Emerges from pupal cocoon
• Adult feed on their hosts
• The life span is about a year under favorable
conditions of cool, moist temperature, but the
maximal period apart from the host is 38 –
125 days depending upon the species.

23. Life Cycle of Tunga Penetrans
• Eggs are shed by the gravid female into the
environment .
• Eggs hatch into larvae in about 3-4 days and feed on
organic debris in the environment.
• Tunga penetrans has two larval stages before forming
pupae .
• The larval and pupal stages take about 3-4 weeks to
complete.
• Afterwards, adults hatch from pupae and seek out a
warm-blooded host for blood meals.
• Only mated females burrow into the skin (epidermis) of
the host, where they cause a nodular swelling

24. Cont…
• After penetrating the stratum corneum, they
burrow into the stratum granulosum, with
only their posterior ends exposed to the
environment .
• Females shed about 100 eggs over a two-week
period, after which they die and are sloughed
by the host’s skin.
• Secondary bacterial infections are common
with tungiasis

25. Life Cycle of Tunga Penetrans

26. Explain the disease transmitted by
Fleas
• Cause irritation: Pulex irritans, Ctenophalides spp.
• Transmitters of bubonic plaque: Xenopsylla cheopis
• Transmitters of endemic typhus; murine typhus or flea
borne typhus; Rickettsia typhi:
• Xenopsylla cheopis, Nosopsyllus fasciatus,
Ctenophalides spp.
• Transmitters of Cestode infections and intermediate
host of Dog tapeworm (Diphylidium caninum):- Pulex
irritans and Ctenophalides felis.
• Rat tapeworm (Hymenolepis species):- Nosopsyllus
fasciatus, Xenopsylla cheopis, Leptosylla segnis

27. Cont…
• Female Tunga penetrans requires an end parasitic
existence for egg development.
• The pregnant female burrows into the skin of its host,
often around the toes, fingers, or other parts of the
body.
• The greatly enlarged flea produces an irritating and
often painful swelling just under the skin.
• Due to irritation causes tissue damage, which may lead
to secondary bacterial infection.
 Pulex irritans is the human flea.
• By its frequent and prolonged feeding on the blood of
its host, it causes discomfort and irritation.

28. Cont…
In the genus Xenopsylla, the rat fleas Xenopsylla
cheopis, X astia, and X brasiliensis they are carriers
of:
– Bubonic plague.
– Flea-borne murine typhus (endemic typhus)
• Ctenocephalides species (fleas of cats and dogs) they
serve as hosts for the tapeworms D. caninum, H.
diminuta, and H. nana.
• When ingested by flea larvae, the eggs develop into
the infective cysticercoid lavae form.

29. Flea bites on the back of a human

30. Control Measures of Fleas
• Killing of rodents should be done after killing
fleas, otherwise the fleas will leave the dead
rodents and jump onto man and result in
increased disease transmission.
• Fleas may be controlled in the following
methods

31. Chemical Control
• For the control of rodent fleas xenopsylla cheopis
and Pulex irritans,
o Insecticides.
o organochlorides DDT, HCH, or Dieldrin.
o organophosphate and carbamate insecticides
• Diaznon
• Fenthion (Baytex)
• Malathion
• Fentrothion (Sumithion) or
• Carbaryl (Sevin)

32. Cont…
o House fumigation with insecticides
• Use of pesticid

33. Personal Protection
• To protect humans from flea bites, repellents,
e.g.
 Dimethylpthalate (DIMP),
 Diethyltoluamide (DEET) or
 benzyl benzoate emulsion (BBE)

34. Key Points
• Fleas are small wingless insects 2.0-2.5 mm which feed
on the blood of mammals and birds.
• Fleas occur in a wide range of host including
domesticated animals.
• The medically important fleas belong to three genera;
Pules, Xenopsylla and Tunga.
• Fleas have a four-part life cycle consisting of eggs,
larvae, pupae, and adults.
• Fleas could be dangerous for they transmit plague,
murrain fever and cause jiggers.
• Control of fleas involves use of chemicals and personal
protection

35. Evaluation
• What are the general characteristics of fleas?
• What are the two species of fleas and the
disease they cause?
• What are the methods of control of fleas?

36. References
• CDC (2009). Parasites and Health: Bed Bugs. Retrieved on
4th May 2005 from
http://www.dpd.cdc.gov/dpdx/HTML/Bedbugs.htm.
• Cook, G. (2000). Manson’s Tropical Diseases (22nd ed.).
London: WB Saunders Company Ltd.
• Hagner, R, Root M, Augustine L. & Huff G. (1939).
Parasitology, with Special Reference to Man and Domestic
Animals New York Inc.: D. Appleton-Century Company.
• Harwood, R.F. & James, M.T. (1979). Entomology in Human
and Animal Health (7th ed.). Pulman: Washington State
University.
• Mike, S. (2004). Medical Entomology for students. London:
Oxford University Press

37. Cont…
• Monica, C. (1998). District Laboratory Practice in Tropical
Countries. Part 1. Tropical Health Technology. NOIDA, India:
Gapson Papers Ltd.
• Monica, C. (2000). District Laboratory Practice in Tropical
Countries. Part 2. Tropical Health Technology. UK:
Cambridge University Press.
• Service, M.W. (1986). Lecture Notes on Medical Entomology
for students. London: Blackwell Scientific Publications.
• United Republic of Tanzania. (2007). Training Course on
Laboratory Diagnosis of Malaria: Malaria Control Series 17.
National Malaria Control Programme of the Ministry of
Health and Social Welfare