Introduction Flashcards
True/False: Parasites are microscopic organisms that live inside blood cells of the host. No other forms exist.
False. Parasites have a remarkable range of size and shape, ranging in size from cestodes over 30 feet in length to microscopic forms that are found inside human cells.
Define Commensalism
one population (or individual) gains from the association and the other is neither harmed nor benefited.
Define autoinfection
a reinfection in which the patient is his own best source of infection from a source already present in the body
Define diarrhea
abnormal frequency and liquidity of fecal discharges.
Define ectoparasite
a parasite that lives on the outside of the body of the host infestation
Define eosinophilia
The formation and accumulation of an abnormally large number of eosinophils in the blood
Define definitive host
the host which harbors the adult or sexually reproducing stages of a parasite
Define intermediate host
that host which harbors the immature, larval, or asexually reproducing forms of the parasite
Define reservoir host
an animal which replaces man as a host in the life cycle of a parasite
Define mutualism
symbiosis in which both populations (or individuals) gain from the association and are unable to survive without it.
Define parasitism
symbiosis in which one population (or individual) adversely affects the other, but cannot live without it. 2. infection or infestation with parasites
Define symbiosis
in parasitology, the living together or close association of two dissimilar organisms, each of the organisms being known as a symbiont. The association may be beneficial to both (mutualism), beneficial to one without effect on the other (commensalism), beneficial to one and detrimental to the other (parasitism), detrimental to one without effect on the other (amensalism), or detrimental to both (synnecrosis).
Define vector
a carrier, usually an arthropod, which transmits an infective agent from one host to another
Define virulence
the degree of pathogenicity of a microorganism as indicated by the severity of the disease produced and its ability to invade the tissues of a host. It is measured experimentally by the median lethal dose (LD50) or median infective dose (ID50). By extension, the competence of any infectious agent to produce pathologic effects.
Name three methods by which one may acquire a parasitic infection.
Ingestion of the parasite; Active penetration of the parasite; Injection by a vector
True/False: All intestinal parasites have a similar life cycle. One swallows the egg, eggs hatch and the parasite lives in the intestinal tract.
False. Some parasite have a simple “hand-to-mouth” life cycle, but others must migrate through the body, notably lungs, to complete their life cycle.
True/False: Young, healthy, adults (soldiers for example) are not at much risk of acquiring parasitic infections because they are in excellent physical condition and good general health.
False. Parasites can infect anyone who is exposed. Those victims who are physically debilitated or have poor immune systems may fare worse, but all can be infected when exposed.
True/false: Diarrhea is a minor side effect of some parasitic infections, and can be ignored since it is self-limiting.
False. Diarrhea can lead to dehydration and fluids must be replaced. This can lead to debilitation and shock in extreme cases.
Name some of the damaging effects a parasite can have on its host.
Blood loss, diarrhea and dehydration, they can trigger an immune response that can damage the host as well as defend against the parasite, tissue destruction (parasite eats your tissues), can make you feel poorly and lose appetite and lose nutrition indirectly.
Which class of white blood cells may show increased numbers in parasitic infections?
Eosinophils
True/False: Indirect evidence of parasitic infections obtained by serological testing is the best method of diagnosis.
False. Direct evidence is the best method. Direct evidence includes identification of a passed worm, microscopic examination of stool to identify parasite eggs or microscopic protozoa, etc.
You have a patient who has a lab result showing a titer of 1:128. What does this mean in 1000 words or less?
The lab has made serial dilutions of the patient’s serum, and tested each dilution. The last dilution that showed a positive result was the tube containing serum diluted 128 times.
What is the primary lab instrument used to diagnose parasitic infections?
A microscope, and a pair of really well-trained eyeballs. More technically impressive methods are used to supplement this basic starting point, but microscopy is really the foundation for this work.
Why does the lab recommend obtaining multiple stool specimens over a period of days?
Some parasites tend to appear in the stool periodically in “showers”. For example, a specimen obtained on a Monday might not have any evidence, and by Wednesday the specimen is loaded with cysts of a parasite.
