13.Explain how plasmodium species evade immune system when entering blood stream
from the hepatic stage? (2 marks)
14. Describe how malaria parasites cause cell and tissue damage? (4 marks)
15. Briefly explain three stages of malaria disease manifestation. (6 marks)
16. Mention the three major groups of metazoans. (3 marks)
17. Mention three groups of trematodes according to the site where they inhabit in the host.
(3 marks)
18. How does a person get infected with Ascaris lumbricoides? (2 marks)
19. Give two species of pathogenic hook worms for human being. (2 marks)
20. State how Necator americanus hookworm parasite causes anemia? (2 marks)
21. Mention three basic factors necessary for transmission of parasitic diseases. (3 marks)
22. Mention three factors that contribute to the spread of parasitic infection in tropical and
developing countries. (3 marks)
23. Explain how the following could contribute to the spread of parasitic diseases
a. Development /change in land use (2 marks)
b. Population migrations (2 marks)
24. Outline three host factors required for a parasitic infection to develop a disease. (3
marks)
25. Explain how the following mechanisms of parasites could cause injury to their hosts?
a. Competition for the host’s nutrients. (2 marks)
b. Toxins and secretions. (2 marks)
c. Mechanical interference. (2 marks)
13. Plasmodium species can evade the immune system when entering the bloodstream from the hepatic stage by multiple mechanisms. First, they can modify their surface antigens to avoid recognition by the immune system. They can also infect and replicate within liver cells, which are not efficiently targeted by the immune system. Additionally, Plasmodium species can suppress the immune response by releasing immunosuppressive molecules.
14. Malaria parasites cause cell and tissue damage through several mechanisms. They invade and multiply within red blood cells, causing their destruction and the release of toxic byproducts. This leads to anemia and the release of parasite proteins that can trigger an inflammatory response. They can also sequester within blood vessels, disrupting blood flow and causing tissue hypoxia. In severe cases, malaria parasites can infect organs such as the brain, leading to potentially fatal complications.
15. The three stages of malaria disease manifestation are as follows:
- The incubation period: This is the time between the bite of an infected mosquito and the onset of symptoms. It can range from 7 to 30 days, depending on the species of Plasmodium.
- The symptomatic period: This is when clinical symptoms of malaria appear, such as fever, chills, headache, and muscle aches. The severity of symptoms can vary depending on the species of Plasmodium and the individual's immune response.
- The recovery period: With appropriate treatment, individuals can recover from malaria. However, some species of Plasmodium can persist in the liver as dormant forms and cause relapses of the disease.
16. The three major groups of metazoans are Nematodes (roundworms), Platyhelminthes (flatworms), and Annelids (segmented worms).
17. The three groups of trematodes according to the site where they inhabit in the host are intestinal flukes, liver flukes, and lung flukes.
18. A person can get infected with Ascaris lumbricoides by ingesting the eggs of the parasite, which are found in contaminated food or water. The eggs then hatch in the intestines, and the larvae migrate to the lungs through the bloodstream. The person then coughs up the larvae, which are then swallowed and mature into adult worms in the intestine.
19. Two species of pathogenic hookworms for human beings are Ancylostoma duodenale and Necator americanus.
20. Necator americanus hookworm parasite causes anemia by attaching to the intestinal wall and feeding on the host's blood. It secretes anticoagulant substances and enzymes that break down the host's red blood cells, leading to blood loss and iron deficiency anemia.
21. The three basic factors necessary for the transmission of parasitic diseases are:
- Presence of a susceptible host
- Presence of a capable parasite
- Presence of a suitable environment for parasite survival and transmission
22. Three factors that contribute to the spread of parasitic infection in tropical and developing countries are:
- Poor sanitation and lack of access to clean water
- Poverty and overcrowding, which increase the risk of exposure to parasites and limit access to healthcare
- Lack of education and awareness about prevention and control measures for parasitic diseases
23. a. Development/change in land use can contribute to the spread of parasitic diseases by altering the habitats of both parasites and their hosts. For example, deforestation can lead to increased contact between humans and animal reservoirs of parasites, increasing the risk of zoonotic transmission. Changes in irrigation practices can create new breeding sites for parasitic vectors such as mosquitoes.
b. Population migrations can contribute to the spread of parasitic diseases by introducing new parasites to regions where they were previously absent. Migrants may bring parasites with them, or they may be exposed to new parasites in their new environment. Migrations can also disrupt existing control measures and health systems, leading to increased transmission.
24. Three host factors required for a parasitic infection to develop a disease are:
- Host susceptibility: Some individuals may be genetically predisposed to be more susceptible to certain parasites. Certain underlying health conditions or immunosuppression can also increase the risk of developing disease.
- Host immune response: The effectiveness of the host's immune response plays a crucial role in determining the outcome of a parasitic infection. An inadequate or dysregulated immune response can lead to chronic infection and disease.
- Host behavior and exposure: The likelihood of getting infected with a parasite depends on factors such as lifestyle, occupation, travel patterns, and behaviors that increase exposure to parasites.
25. a. Competition for the host's nutrients: Parasites can compete with the host for essential nutrients, causing nutritional deficiencies in the host. For example, parasitic worms like hookworms feed on the host's blood or intestinal contents, leading to malnutrition and anemia.
b. Toxins and secretions: Parasites can produce toxins and secretions that can directly damage host cells and tissues. These substances can cause inflammation, tissue necrosis, and impair organ function. For example, the toxins produced by Plasmodium falciparum, the parasite that causes severe malaria, can lead to organ failure and death.
c. Mechanical interference: Parasites can physically disrupt the tissues or organs they infect. For example, filarial worms can cause lymphatic obstruction, leading to swelling and damage to the lymphatic system. Large infestations of insects such as lice or ticks can cause irritation, skin lesions, and secondary infections.