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Questions and Answers
Which of the following parasites is known to cover its surface with host serum proteins to evade the host's immune system?
What is the primary mechanism of evasion used by African trypanosomes living freely in the bloodstream and body fluids of the host?
What is a harmful effect of African trypanosomiasis on the host?
What is a possible consequence of drug treatment that leads to massive killing of parasites in a host?
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Which of the following is an example of a superinfection that can occur in leishmaniasis?
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Which of the following types of parasites is responsible for mechanical damage to the host's small intestine, leading to intestinal occlusion?
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What is thought to be produced by the African trypanosome when it is in the central nervous system?
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What is a possible consequence of the immune response in African trypanosomiasis?
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Which of the following is a harmful effect of a parasite on its host?
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Which of the following diseases is known to lead to a degree of immune suppression in the host?
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Which group of parasites requires further development within the body of a snail host before they become infective?
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What is the term for the severe loss of weight that can occur in animals and humans infected with African trypanosomiasis?
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What is the term used to describe the presence of an endoparasite in a host?
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What is the term used to describe the presence of an ectoparasite in a host?
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What is the term used to describe the lysis of erythrocytes, leading to haemolysis and anaemia in malaria?
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Which of the following parasites is transmitted through soil and requires further development in soil before becoming infective?
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What is the primary function of a biologic vector?
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What type of parasite hides inside host cells to evade the immune system?
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What is the result of an allergic reaction to ectoparasite infestation?
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What is the primary mechanism of parasite-induced immunosuppression?
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What is the role of a parasite reservoir in the parasite life cycle?
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What is the primary effect of parasite infection on human health?
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What type of parasite infestation can lead to anaphylactic shock?
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What is the primary mechanism of disease pathology in parasite infections?
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Study Notes
Extracellular Parasites
- Some parasites cover their cell surface with host serum proteins to avoid recognition by the host's immune system
- Examples include:
- Schistosoma worms covering themselves with host serum albumin
- Rodent trypanosomes covering themselves with ablastin (IgE)
- Antigenic variation in African trypanosomes helps them evade the host's immune system
- Cyst formation by Entamoeba and other amoeboid parasites is another mechanism of evasion
Harmful Effects of Parasites on the Host
- Wasting (cachexia, spoliatrices) due to African trypanosomiasis and leishmaniasis
- Superinfections, such as bacterial infections in the case of (muco)cutaneous leishmaniasis
- Production of toxic compounds, such as aromatic amino-acid analogues by African trypanosomes in the central nervous system
- Immunodepression, making the host more susceptible to other diseases, as seen in malaria and bilharziasis
- Allergic reactions, such as depigmentation in onchocerciasis (river blindness)
- Anaphylactic shock, induced by the sudden release of large amounts of parasite internal antigens into the bloodstream
- Mechanical damage, such as:
- Haemolysis and anaemia due to malaria
- Intestinal occlusions due to ascaris infection
- Irritative reflexes, such as intestinal contractions in ascaris infection
- Irritation of skin and tissues by ecto- and endoparasites
Difference between Infection and Infestation
- Infection: the presence of an endoparasite in a host
- Infestation: the presence of an ectoparasite in a host
Factors of Parasitic Infection
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- Source of infection
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- Infective stage of the parasite
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- Portal of entry
-
- Presence of susceptible host
Sources of Infection or Infestation
- Soil-transmitted group:
- Ascaris lumbricoides
- Trichiuris trichiura
- Hookworms
- Strongyloides stercoralis
- Snail-transmitted group:
- Trematodes (flukes)
- Schistosomes
- Arthropod-transmitted group:
- Plasmodium
- Filarial worms
- Sand fly (Leishmania)
- African trypanosomiasis (Tsetse fly)
- American trypanosomiasis (Reduvid bug)
Vectors and Parasite Reservoir
- Vectors: hosts that transmit parasites to humans
- Biologic vectors: essential in the life cycle
- Mechanical or Phoretic vectors: not essential in the life cycle
- Parasite reservoir: the biotope where the parasite lives
- Types of parasite reservoir:
- Human reservoir
- Animal reservoir (domestic and wild animals)
Effects of Parasites to Humans
- Parasites secrete toxins and steal vital nutrients from the body
- Parasites can irritate or exacerbate other health problems
- Everyone is at risk of parasitic infections
How Do Parasites Survive Inside an Immunocompetent Host?
- Ectoparasites:
- Infestation leads to local lesions of minor to moderate importance
- Leads to allergic reactions and immunological reactions that harm the host, not the parasite
- Intracellular parasites:
- Try to escape immunological reactions by hiding inside host cells
- Examples include:
- Toxoplasma in lymphocytes
- Plasmodium in erythrocytes
- Leishmania in macrophages
- T.cruzi in muscle cells
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Description
Learn about the strategies used by parasites to evade the host's immune system, including covering themselves with host serum proteins, antigenic variation, and cyst formation.
