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224 Tasks for the Veterinary Assistant

Lice on the fly species, some larvae develop in tissue where
they can be seen as white, worm‐like creatures called
There are two kinds of lice: chewing lice that feed on maggots that feed on dead tissue. If not taken care of the
skin scales and sucking lice that feed on blood maggots will make a small wound quite large. Others will
(Figure 12.4). The sucking louse has a narrower head bite and suck blood, making multiple tiny sores often
than the chewing louse. Lice complete their entire life seen on tips of ears or across the nose. Others bite so
cycle on their hosts. Lice are about 3 mm in size and are hard that large welts develop and are quite painful. Flies
visible when crawling across bare skin. After mating, the also spread other parasites.
female attaches her eggs, called nits (see Figure 10.13),
by sticking them on the hair shafts of the host. Nits are
white and about 1 mm in size. The nits are also used to Ticks
identify a louse infestation. A small‐toothed comb is used Ticks are bloodsucking, disease‐spreading insects that
to comb through suspected hair which is then looked at engorge themselves on their host’s blood and then fall
under the microscope. Lice are transmitted by direct back into the environment. They lay their eggs in the
contact between an infected host and an uninfected environment where they hatch and hang out on brush
individual. Lice are species specific, but there is a species waiting for a mammal to pass by. The unfed nymph may
that prefer humans!
be as small as 3 mm, an engorged adult may be up to
three times larger. Their presence is noted when a tick is
Flies seen attached to the skin. Favored places are the ears
and face. Care is taken when removing ticks that have
Flies can affect hosts during two phases of their life cycle: attached to the host. They are grasped as close to the
adults and larvae. Adult flies vary from the small sand fly, body as possible and pulled in the direction they are
1–3 mm in size, to the larger horse fly, which can be up lying. If you lift and pull backwards, the heads break off
to 3.5 cm in length. The different species of adult flies and cause a sore. Ticks transmit diseases such as Rocky
feed on blood, tears, saliva, or mucus. The damage they Mountain spotted fever, ehrlichiosis, Mycoplasma infec-
cause to tissues may indicate their presence. Depending
tions, and Lyme disease. The Ixodes sp. or “black legged”
tick is the main culprit for Lyme disease (Figure 12.5).
This tick as an adult is half the size of other ticks, making
it very hard to find. They will attach to any mammal thus
making Lyme disease zoonotic.

FIGURE 12.4 Chewing louse. Source: Wikimedia Commons. Used FIGURE 12.5 Ixodes sp. or black legged or deer tick. Source:
under CC BY‐SA 3.0, https://commons.m.wikimedia.org/wiki/ https://commons.wikimedia.org/wiki/File:Adult_deer_tick.jpg.
File:Lice_image01.jpg. Public Domain.