Page 224 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 193

Lice common in livestock

Anoplura (sucking lice)

Haematopinus sp. are found on cattle, pigs and
horses. Linognathus sp. are found on cattle,
sheep, goats and dogs (Figure 3.46). Solenoptes
sp. are found on cattle.

Mallophaga (biting lice)
Damalinia sp. are found on cattle, sheep, goats Figure 3.47 Lateral view of a flea. (C) (Ctenocephalides
and horses (Figure 3.46). Felicola sp. are found sp.) cat and dog fleas. The fleas are specialized for
on cats (usually young or debilitated individu- jumping. Most fleas are not host specific and will
als). Trichodectes sp. are found on dogs and can be readily infest a wide range of hosts. Illustration: Louis
a vector for the tapeworm (Dipylidium caninum). Wood.
Heterodoxus sp. are found on dogs. Lipeurus sp.,
Menopon sp. and Menacaullus sp. all affect poultry However, flea infestation can result in significant
but do not occur worldwide.
skin irritation, especially in hosts that become
hypersensitive to the flea saliva. The latter is
commonly seen in cats and dogs and may be
Fleas
associated with a significant amount of hair loss,
because of over grooming. Fleas are vectors for a
There are estimated to be over 2500 species of number of viral, bacterial and rickettsial diseases
fleas worldwide. Fleas are small flightless insects in humans and animals (Table 3.11). The orien-
that spend much of their life cycle in the envi- tal rat flea, Xenopsylla cheopsis was considered to
ronment. The parasitic adults live by consuming be a key vector for Yersinia pestis (the cause of
the blood of avian and mammalian hosts. Adult bubonic plague) in the middle ages.
fleas are usually about 3 mm long, brown in
colour with flattened bodies (Figure 3.47) to
enable them to move through their host’s fur or other insects
feathers. They lack wings but have long hind legs
adapted for jumping and mouthparts adapted There are a wide range of other insects which
for piercing skin and sucking blood. The eggs are capable of causing disease in domestic and
and larvae develop in the environment with wild animals, some of these are outlined in Table
the length of the life cycle depending on envi- 3.11. The morphology and life cycles of some
ronmental conditions and temperature. Larvae insects of veterinary importance are given in
are maggot-like and have chewing mouthparts Figures 3.48a and 3.48b. There are some spe-
to feed on organic debris. Each species of flea cies of fly which spend part of their normal
is adapted for a specific host species but, most life cycle inside live animal hosts, for example,
will bite a range of other hosts, for example, the bot flies which are members of the fam-
dog and cat fleas (Ctenocephalides sp.) often bite ily Oestridae. The life cycle of the horse bot is
humans. Fleas are principally a nuisance to illustrated in Figures 3.49a and 3.49b. Other
their hosts, causing itching and over grooming. flies, especially the blow flies, may lay eggs in

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