parasitic adaptaqtion

parasitology

1. Topic Submitted to Presented by Roll no. Semester Department of Zoology Parasitic adaptation Prof. Saeed Ahmad Noor Ullah . Z-30 8 th Govt. Superior Science College Pesh .

2. PARASITIC ADAPTATIONS The survival of a parasite in the body of the host depends upon its abiity to adapt to the surrounding environment at the site of its infection, this is called microenvironment. To adapt to this microenvironment, certain morphological, anatomical and physiological changes occur and because of which the parasite survives in the host. Such changes which facilitate a parasite to adapt to parasitic mode of life in the host itself are called parasitic adaptations .

3. Taenia solium Different types of parasitic adaptations are as follows: 1.Body shape and size Body shape and size  of he parasite depends upon the space available at the site of infection. e.g., Intracellular parasites are very small in size – Plasmodium. Enerozoic parasites are usually large in size – Taenia solium , Ascaris lumbricoides . Hepatophagic parasites are moderately large and flat – Fasciola . Parasites dwelling in the blood vessels are slender and elongated – Schistosomes .

4. 2. Locomotory struturres  almost absent in the parasitic forms , as they need not move in search of food. 3. A parasite in the body, if occurs, without attaching to the surrounding tissues , it gets carried away to a nonspecific site or to the exterior of the body , in which case, is survival is not possible. Thererfore , to remain at the specific site of infection , they attach to the surrounding tissues. For this purpose , all the parasites are provided with adhesive structures like hooks. e.g., Echinostomes , Monogenetic trematodes are equipped with  suckers . Trematodes and Cestodes are equipped with rostellum . Taenia solium  (a cestode ) is equipped with   rostellum , hooks and suckers. taenia scolex with hooks and suckers

5. 4.In the case of intestinal parasites , there is every possibility, that they are either harmed , injured or digested by the gastrointestinal secetions of the host. To protect from the harmful effects of digestive enzymes , the parasite’s body surface is covered with cuticle ( Nematodes  – Ascaris lumbricoides ) or Tegument  ( Flatworms –   Taenia soium ). Intestinal worms may also secrete some  antienzymes  that neutralize the digestive enzymes of the host. e.g.,  Taenia soium . Teguent in Taenia cuticle in ascaris

6. 5. In the bodyof a host where parasites live , the amount of oxygen may very high( lungs) or relatively less (intestine and liver ). The catabolic  activity of parasites living in oxygen rich environment  are predominantly of  aerobic type . e.g., Human lung fluke –  Paragonimus   vestermoni . The parasites live in less or no oxygen content are  facultative anaerobes . They can carry  on aerobic respiration if oxygen is available and anaerobic respiration  in the absence of oxygen. e.g.,  Ascaris   lumbricoides . Some parasites live as  obligatory  anaerobes  as the availability of oxygen is very rare for them. e.g .,  Taenia solium , Entamoeba histolytica .

7. 6.The reproductive potential of parasites is veery high. e.g., Taenia soium lays about 35,000 eggs/day. Fasciola hepatica lays about 10,000 eggs/day, Ascaris lumbricoides lays  about  2,00,000 of eggs/day. Inspite of  numerous risks during development, such high reproductive potential ensures  the continuation of parasitic race.

8. Redia of liver fluke 7.In addition to the production of enormous number of eggs , there will be multiplication of larval stages resulting in the production of  several infecting agents. This process called as polyembryony occurs in trematodes . e.g., The life cycle of trematode includes five    larvalstages viz., miracidium , sporocyst, redia , cercaria   and metacercaria . Of these , sporocyst exhibits polyembryony   producing a number of rediae   and redia exhibits polyembryony producing a number of cercariae . Thus the life cycles of endoparasites are very complex as  they  exhibit high host- paarasite specificity. Larval stages of liver fluke

9. 8. Infective stages of the monogenetic parasites like   Entamoeba histolytica   need to survive outside the body of host in the open environment. Hence, they are exposed to harsh environmental conditions , they are to tide over the unfavorable  conditions , they are enclosed in a protective envelope forming cyst. 9. Due to the presence of the parasites , host’s immunological system gets activated producing specific antibodies to eliminate parasites. However , parasites elude the action of antibodies generally by a process of molecular mimicry , in which the parasites covered by molecules that are similar to that of the host. These are considered by host’s antibodies as self molecules and fail to counteract.

10. 9. Some parasites  e.g., Plasmodium and HIV constantly change        the antigenic polypeptides. The parasitic antigens change in different stages of development. Hence , it is not easy for the host to switch on the required defense mechanisms or to produce suitable  vaccines against  these diseases.

11. THANKS