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).

• 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'