Vossler Flashcards
(9 cards)
What are some characteristics of parasitic diseases?
High prevalence in developing countries; in lower socioeconomic population
Low mortality and morbidity (except Malaria)
Limited drug-development
No vaccines
Environmental changes, human behavior and population movement have a great effect on transmission, distribution, prevalence, and incidence of parasitic diseases in a community
What are Neglected Parasitic Infections in the United States (NPIs)?
1- Chagas disease ('kissing bug')
2- Cysticercosis (pig)
3- Toxocariasis (dog & cat)
4- Toxoplasmosis (cat)
5- Trichomoniasis (sexually transmitted)What is the difference between a definite host and an intermediate host?
A Definitive host (DH) that harbors the adult or sexually mature stages of the parasite (or in whom sexual reproduction occurs) e.g. man is DH for Enterobius vermicularis (pinworm), while female Anopheles mosquito is DH for Plasmodium species (malaria parasites) -transmission from host to host can occur directly
An Intermediate host (IH) that harbors larval or sexually immature stages of the parasite (or in whom asexual reproduction occurs) e.g. man is IH of malaria parasites -transmission to the definitive host requires a vector (which may be the ingestion of the intermediate host which is infected with the parasite)
List different mechanisms of parasites defense mechanisms from protective host responses
antigenic concealment antigenic variation antigenic shedding antigenic mimicry immunological subversion(immunosupression) immunological diversion
What is the most important survival strategy that parasites have?
Their complicated life cycle
What are the key concepts of host immune responses to parasites?
(1) Heterogeneity with respect to lifecycles and antigenic expression is a key feature of parasitic agents
(2) Many parasitic infections are chronic in nature
(3) The mechanisms of evasion differ substantially from bacterial infections
(4) Many parasites undergo significant genetic and antigenic variation within a relatively short time
(5) The innate immunity in the natural hosts may be genetically determined -parasites have developed a variety of strategies to evade adaptive defenses that are more complicated than those for evading innate defenses
(6) Humans, as well as animals, differ widely in their ability to handle complex antigens such as those found in parasites
Why are eosinophilia and the IgE antibody response characteristic of parasitic infections?
The term eosinophilia is defined as an increase in peripheral blood eosinophilic leukocytes
Eosinophilia is associated with many disorders -several causes are known, with the most common being some form of allergic reaction or parasitosis
A hypothesis exists that the primary function of eosinophils is to defend hosts against infection by relatively large organisms such as parasitic helminths
Degranulation is a cellular process that releases antimicrobial cytotoxic molecules from secretory vesicles called granules found inside some cells including mast cells and eosinophils -mast cells are located in connective tissue, including the skin, the linings of the stomach and intestine, and other sites; degranulation occurs when IgE binds to an antigen and the Fc portion of IgE binds to the cell inducing degranulation
IgE immunoglobulin is an important component of host-protective immune responses against the helminthic parasites
IgE can be increased withparasiticinfections, so a total IgE test is sometimes used as a screening test if a parasitic infection is suspected
What are the modes of parasite transmission?
Direct ingestion of infective larvae, eggs or cysts
Ingestion of the intermediate host
The parasite actively penetrate the principal host
Maternal transmission (Toxoplasma gondii) Vector borne transmission – Plasmodium (malaria)
What is the pathogenesis of parasitic disease?
Parasitic diseases may be gastrointestinal, blood borne, or tissue infections in nature
Due to the wide variety of parasites that infect man the pathogenesis is highly variable
Unlike many bacterial or viral diseases, parasitic infections tend to be chronic in nature and may last for many years
When a parasite enters a host, there are several possible results: (1) there may be no infection at all (thanks to host’s innate immunity), (2) the parasite may invade the host, become established, and then be killed and eliminated by host defense mechanisms
(requires antibody formation and cell mediated immunity), (3) the parasite may overwhelm and kill the host (due to rapid multiplication of parasite, invasion of vital organ (s) or immunocompromised host
The parasite may establish a long lasting infection in which the host begins to eliminate the parasite but cannot remove it completely -
ranges from host controlling disease to host ultimately succumbing to the infection and dying from it
The host may mount a response that attacks not only the parasite but also host tissues -most of the pathology associated with a parasitic infection results from the immunologic responses to the offending organism and may be more dangerous for the host than the invader
