Page 227 - The Veterinary Laboratory and Field Manual 3rd Edition

196 Susan C. Cork and Mani Lejeune

Figure 3.49a The life cycle of the equine stomach bot (Gasterophilus intestinalis). (A) Adult fly lays eggs
on the horse’s hair (usually the lower limbs). (B) The horse ingests the bot eggs while grooming. (C) The
eggs hatch in the horse’s mouth or throat and the larvae migrate to the stomach to pupate (D) (see also
figure 3.49b). The pupae pass out of the horse’s system in the faeces (E/F). Pupae hatch and adult flies
emerge when the weather conditions are appropriate. Illustration: Louis Wood.

diseased tissue or fresh wounds of animals lead-
ing to maggot infestation or myiasis. Myiasis
may lead to severe tissue damage if maggots are
left to invade healthy tissue so wounds should
be regularly checked for the presence of mag-
gots. Identification of insects takes skill and
experience and it is necessary to have access to
a good dissecting microscope and identification
keys.

Figure 3.49b Horse stomach opened out to illus-
trate the appearance of the larvae of the horse bot Identification of insects
fly (Gasterophilus sp.) which develop and overwin-
ter in the horse’s stomach before passing out in the Using identification keys, it is possible to iden-
faeces to emerge as adult flies. Small numbers of tify most of the common ectoparasites to genus
bots probably do very little harm but high numbers level but for species identification samples may
may damage the gastric mucosa. need to be stored for later submission to a spe-
cialist institute. The classification of lice, flies
and other insects of veterinary importance is
outlined in Figure 3.37 and key species are listed

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