Quick refreshers on key topics , by Frank Ruedisueli

ABSTRACT Helminths are divided into three types : nematodes ( roundworms ), cestodes ( tapeworms ) and trematodes ( flukes ).

All three types occur in companion animals , although flukes are not common in cats and dogs in the UK and mainly affect ruminants .

This article focuses on the life cycle and treatment of nematodes , with special attention given to Toxocara canis and Toxocara cati .

Keywords helminths , nematodes , roundworms , hookworms , heartworms , life cycle , treatment

This article covers nematodes in general , with examples linked to the species listed in Table 1 , in particular Toxocara canis ( which infects dogs ) and Toxocara cati ( which infects cats ).

Physiology

Nematodes have a cylindrical shape , in comparison to the flattened body plan of cestodes ( see article on cestodes , from page 54 ). They are elongated , non-segmented parasitic worms , which can vary in size by species and life stage , from 300 µ m microfilariae to 1 – 25 cm adults .

Nematodes are sexually dimorphic and so have distinct male and female characteristics ; some , such as male spicules , can be used to identify species [ 1 ] . Unlike cestodes , nematodes have a digestive tract [ 1 ] .

50 Veterinary Nursing Journal