Quick refreshers on key topics , by Frank Ruedisueli

ABSTRACT Ectoparasites are arthropods that live outside the host and either attach to or burrow into the host ' s skin . Arthropods of particular veterinary interest are lice , fleas , mites and flies .

This article focuses on Anoplura and Mallophaga lice , as well as green bottle and blue bottle flies . It includes an overview of their morphology , life cycle , effect on their host and the related treatment .

Keywords ectoparasites , lice , flies , life cycle , myiasis , fly strike , treatment

Ectoparasites are arthropods that live on the outside of the host , either attaching to or burrowing into the skin [ 1 ] . They include lice , fleas , mites and flies . Lice , fleas and flies are classed as insects , while mites ( along with ticks ) are classed as arachnids .

Two species of lice are of clinical significance in the dog : Linognathus setosus ( a sucking louse ) and Trichodectes canis ( a biting louse ). In the cat , the main louse of concern is Felicola subrostratus .

Anoplura

L . setosus lice ( Figure 1 ) are wingless arthropods of around 2 mm in length . The head is narrower than the thorax and abdomen , and the mouth parts are adapted for sucking blood . The louse does not have eyes , but has segmented antennae equipped with chemoreceptors [ 2 ] . To feed off the host , the louse uses specialised terminal mouth parts to attach to and pierce the skin and to suck blood [ 2 ] .

Lice

Lice are permanent parasites , in that they spend their entire life cycle on the host [ 2 ] . They are dorsoventrally flattened and wingless . There are two groups of veterinary relevance : Anoplura ( sucking lice , in mammals ) and Mallophaga ( chewing lice , in birds and mammals ).

Their claws ( single or double ) are specifically shaped to attach to the host ' s hair / feathers ; these adaptations mean they are host-specific parasites . Further characteristics include five-segmented antennae , the absence of eyes ( or primitive eyes ) and the laying of operculated eggs .

Figure 1 . L . setosus ( male ), seen with an electron microscope [ 2 ] . The circled areas in the main image are shown magnified on the right .

44 Veterinary Nursing Journal