Eosinophils are a type of white blood as you stated. They are a
very minor fraction under normal circumstances. Typically they account
for 2-5% of all the white blood cells seen in a lab test called CBC
<complete blood count>. This test includes a WBC <white blood cell
count> which in humans is considered normal in the range of 5,000 to
10,000 white cells per cc of blood. Thus, eosinophils at 5% of 10,000
cells constitute 500 cells.
The term eosinophilia is reserved for elevated counts both by
total and by percentage. The most common conditions associated with
elevated eosinophil numbers are collagen diseases, allergies, asthma,
some neoplasias (i.e., some stomach cancers) and of course parasitic
infections. Typically, parasitic organisms that invade the tissues of
the body as contrasted with intestinal worms are the parasites most often
associated with eosinophilia. Ascaris infections which you inquired
about has an impressive eosinophilia while the larvae are migrating
through the tissues of the body, but once the worms arrive in the
intestine and become reproductive adults, the eosinophilia drops off.
The intestinal form of the disease is usually diagnosed by a stool exam
wherein the very characteristic eggs are seen with the aid of a microscope.
Another common parasitic cause of hypereosinophilia is visceral larva
migrans caused by the juvenile form of dog Ascaris <Toxocara canis>. In
this case the WBC can approach 100,000 with > 70% eosinophils.
Unsuspecting physicians often diagnose eosinophilic leukemia but a simple
blood test for antibodies specific for Toxocara indicate this infection.
Because people are not dogs, these worms never arrive in the intestines
but continue to migrate through the tissues and the eosinophilia can persist.
Eosinophils and eosinophilia technically refer to the cells as
seen in the bloodstream. However, eosinophils do not in general carry
out any function in the blood. Rather they leave the blood vessels
and migrate through the connective tissues of the body. If they encounter a
parasite larva under these conditions, lots of them will form a cellular
mass around the worm. Some people believe this is a mechanism to kill
the parasite but I personally, believe it is a sequestration reaction to
contain metabolites of the parasite from spreading throughout the body.
Your last question is more difficult to answer. Your doctor has
to consider all the symptoms and signs and proceed accordingly. There
are general patterns of tests that rule in or rule out the possible
causes of eosinophilia. If there is reason to suspect parasites, then
there are tests to find and identify the infective agent. Unfortunately,
there is no major scan that is done routinely which visualizes
parasites. (Although large numbers of adult ascarids can be seen in the
GI tract by CT and or MRI. Likewise, neurocysticercosis can too, but CT
and MRI are not routine unless indicated.
Hope this helps.
/\ /\//\/######/ /\/#######\ ! Stephen G. Kayes, Ph.D. !
/\/ /\//\/ /\/ /\/ ! Structural & Cellular Biology !
/\/ /\//\/ /\/ /\/ ! University of South Alabama !
/\/ /\/ \/#######/ /\/########/ ! Mobile AL 36688 !
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Will clone genes for food.
On Fri, 5 Jan 1996 until at teleport.com wrote:
>> Would someone here consider answering a question for me
> about eosinophilia? I have been told
> that eosinophilia just means that that type of white blood cell is
> elevated on blood counts--that it is common and nonspecific
> with parasite infestations. I thought it was actually a result
> of a parasitic infection, and that you could see the parasites
> that caused the infection on some sort of medical scan. What
> exactly IS eosinophilia? And what causes it? If it really is
> caused by parasites, which ones cause it--ascarids? M. lineatus?
>> Thank you for your time.
>> - Tara K. Harper
>until at teleport.com>> / Even a thought /
> / Even a possibility can shatter us and transform us /
> / - Nietzsche /