Helminths Introduction

Soybean Cyst Nematode and Egg, Scanning Electron Micrograph - Wikimedia Commons

The term helminth is commonly used to describe parasitic worms, all with eukaryotic cell structures. The two main groups are the Nematodes (roundworms) and the Platyhelminthes (flatworms).

Soybean cyst nematode and egg

• Nematodes: typically long and slender, the nematodes are dioecious (male and female individuals) and are generally found attached to the intestinal wall
  • Hookworms- widely endemic in the tropics, hookworms hatch on soil and enter the host through the feet. Pathogenesis involves intestinal irritation and haemorrhage.
  • Giant roundworms- found worldwide, hosts are infected by ingesting eggs from faeces of infected individuals. Symptoms include intestinal irritation and malnutrition
  • Pinworms- found in temperate areas, eggs hatch in the intestine after ingestion
  • Pork worm- found worldwide, pork worms can infect most carnivorous animals, causing trichinosis.
  • Filarial worms- various species found in tropical and subtropical areas depending on distribution of insect vectors, causes allergic reactions and potentially blindness
• Platyhelminthes
  

  Scolex, with hooks, of T. solium tapeworm
  • Trematodes- commonly known as the 'flukes,' trematodes are non-segmented and have alternate sexual and non-sexual generations in different hosts. They are mostly hermaphroditic except the blood flukes, which are dioecious.
  • Cestodes- commonly known as the 'tapeworms,' these consist of an enlarged head section ('scolex'), with suckers or hooks for attachment in the intestine and successive flat segments forming a chain of 'proglottids'