PARASITOLOGY

PARASITOLOGY

n SUMMARY

The presence and survival of a parasite can be the cause of pathology to the host. The

multiplication of a protozoan within a cell and the subsequent release of the offspring which

then re-invade new cells leads to cycle of continuous cell damage. In the gut mucosa this

can bring about a change in the gut architecture and lead to a malfunctioning condition.

Migration of the larger parasites through tissue and organs leads to permanent scarring of

the tissues.

Once a parasite has established itself within the tissue, an innate inflammatory reaction

follows. This could lead to either the destruction of the parasite or encapsulation within fibrous

tissue. The permanent presence of a parasite can lead to destruction and atrophy of the

surrounding tissue and malfunctioning of either the local tissues or the organ.

The trematodes that are the cause of a great deal of human disease are Paragonimus,

Opisthorchis and Schistosoma. They inhabit the lungs, the liver and both mesentric and

bladder blood vessels, respectively. Humans are infected via their direct or indirect contact

with water. Fasciolais a trematode that mostly infects domestic animals, in particular sheep.

There are cases of humans living in sheep-rearing areas becoming infected with Fasciola.

The metacestodes of Echinococcusdevelop into large hydatid cysts and the disease that

causes is known as hydatidosis.

End of chapter questions

PATHOLOGICAL EFFECT OF THE PARASITE UPON THE HOST

Question 7.1 What main products produced by the parasite’s metabolism can become

toxic to the host?

Question 7.2 What effects can gut parasites have upon the host tissues?

Question 7.3 What chemical and physiological changes can occur as result of a parasitic

infection?

Question 7.4 What are prostaglandins and leukotrienes and what is their function?

Question 7.5 What are the main characteristics of inflammation?

Question 7.6 Describe all the reactions that are part of the process of inflammation.

Question 7.7 What is a pyrogen and what are the functions of pyrogens?

Question 7.8 What interleukins are associated with inflammation?

REACTIONS TO PARASITIC HELMINTHS

Question 7.1 What cells are normally associated with reactions to parasites?

Question 7.2 Which cells usually are the first to ‘attack’ a parasitic infection?

Question 7.3 How do phagocytic cells destroy non-self material?

Question 7.4 Describe the sequence of events that eventually leads to the cellular

destruction of a helminth parasite.

Question 7.5 Describe what happens to liver tissue when invaded by parasites.

Question 7.6 What is neurocysticercosis?

Question 7.7 Describe the changes that occur within the spleen.

Question 7.8 Discuss the various pathological conditions that can be caused by parasites.

HUMAN TREMATODE PATHOGENS

Question 7.1 Describe the life-history of three trematodes that infect humans.

Question 7.2 What diseases do these parasites cause?