Adaptations for Parasitism

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  • Adaptations for Parasitism -The pork tapeworm (Taenia Solium)
    • 'Parasites are organisms that live on or in another organism, called the host, and obtain nourishment at the expense of the host (harms the host)'
    • The tapeworm is ribbon-like and can be up to 10 metres long
      • It has a head (scolex), is muscular and has suckers and hooks
        • It's body consists of a linear series of thin segments
      • It has two hosts. The primary host is the human and the secondary host is the pig
        • The pig becomes infected if it feeds in areas contaminated by human faeces
          • Humans are infected by eating undercooked, infected prok
    • Although the tapeworm lives in the gut with an immediate source of food, it still needs to survive the hostile conditions there. So it has a number of problems to overcome;
      • Problem: It lives in the hosts digestive juices and mucus with extremes of pH; Attack by the hosts immune system
        • Solution: To prevent digestion/immune responses it has a thick cuticle and produces inhibitory substances on it's surface
      • Problem: Could be dislodged by preistaltic contractions of the muscular gut wall
        • Solution: Suckers and a double row of curved hooks  for attachment to the gut wall
      • Problem: Only room to accommodate one tapeworm
        • Solution: Each segment contains both male and female reproductive organs and vast numbers of eggs (40,000) produced by each segment
      • Problem: If the host dies, so does the parasite
        • Solution: It has two hosts (human and pig)
      • Problem: Transferring to the host and to increase the chance of some of the offspring reaching a new host
        • Solution: The eggs have resistant shells so they can survive outside the body until eaten by a secondary host
      • Problem: Have means of penetrating the host
        • Solution: Small eggs/cysts are ingested unnoticed
      • Problem: Mode of nutrition and gas exchange whilst in host
        • Solution: Long and thin shape creates short diffusion pathway with a large surface area to volume ratio so pre-digested food and oxygen absorbed over body surface
    • Harm
      • The adult tapeworm may cause weight loss and abdominal discomfort
        • The larvae of the pork tapeworm are the main cause of human cysticercosis. Once inside the stomach, the tapeworm hatches and penetrates the intestine, travels through the bloodstream and develop into cysts which can lodge in various organs, damaging surrounding tissues
    • Treatment
      • Adults can be treated with drugs (praziquantel). This induces severe spasm and paralysis of the worms muscles, preventing the hooks and suckers from holding onto the wall of the intestine
        • Simple precautions that can be taken to prevent infection from the tapeworm include:
          • Avoid spreading untreated sewage on land
          • Inspection of meat and meat producing facilities (Public health measures)
          • Making sure meat is well cooked


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