1) Ascariasis:
i) Causative agent: The causative agent of ascariasis is the parasitic roundworm called Ascaris lumbricoides.
ii) Mode of transmission: Ascariasis is usually transmitted through ingestion of Ascaris eggs present in contaminated soil, food, or water.
iii) Life cycle of the parasite: The life cycle begins when Ascaris eggs are ingested by a human host. The eggs hatch in the intestines, and the larvae migrate through the bloodstream to the lungs. The larvae are then coughed up and swallowed, returning to the intestines where they mature into adult worms. The adult worms produce eggs that are passed in the host's feces, completing the life cycle.
iv) Effect on the host: Ascaris lumbricoides can cause abdominal pain, malnutrition, and obstruction of the intestines if a heavy infestation occurs. In severe cases, the worm can migrate to other organs like the bile duct, appendix, or pancreas, leading to complications.
v) Adaptive characteristics of the parasite: Ascaris lumbricoides has a durable and resistant outer layer on its eggs, allowing it to survive harsh environmental conditions and remain infective for a long period of time. The adult worms can also grow up to 30 cm in length, enabling them to absorb nutrients from the host's intestines efficiently.
2) Schistosomiasis:
i) Causative agent: Schistosomiasis is caused by different species of parasitic trematodes (flukes) belonging to the genus Schistosoma.
ii) Mode of transmission: Schistosomiasis is transmitted when humans come into contact with freshwater contaminated with the larvae of Schistosoma, which are released from infected snails.
iii) Life cycle of the parasite: The life cycle of Schistosoma involves two hosts - humans and snails. The eggs released by adult female Schistosoma in the human host's bloodstream are excreted in feces or urine. When the eggs reach freshwater, they hatch, releasing larvae called cercariae. The cercariae infect specific species of snails, where they develop into infective larvae called cercariae. These cercariae are then released from the snails into freshwater, where they can penetrate the human skin, entering the bloodstream to complete the life cycle.
iv) Effect on the host: Schistosomiasis can cause a variety of symptoms depending on the species of Schistosoma involved. Symptoms can range from mild itching and rash (during the penetration of cercariae through the skin) to chronic infections that lead to damage of the liver, spleen, bladder, and intestines. Long-term complications include anemia, organ failure, and increased susceptibility to other infections.
v) Adaptive characteristics of the parasite: Schistosoma parasites have a complex life cycle involving snail hosts that provides them with protection and a suitable environment for development. The parasites have evolved mechanisms to evade the host's immune system, including antigenic variation and altering the host's immune response. Additionally, the cercariae possess enzymes to help them penetrate and migrate through the skin, ensuring successful entry into the human host.
Name 2 diseases caused by parasitic worms and for each mention the;
i) causative agent
ii) mode of transmission
iii)life cycle of the parasite
iv) effect of the parasite on the host
v) adaptive characteristics of the parasite
1 answer