Quantcast Classification of Helminths - Principles of Epidemiology and Microbiology

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
2-24. GENERAL
Helminths are multicellular (Metazoa) worms or wormlike animals. They may be
parasitic or free living. Since they are multicellular, most helminths may be easily seen
with the naked eye in the adult form and are not truly within the scope of microbiology.
Because of their medical importance, however, helminths are usually studied, along
with protozoa, as part of the science of medical parasitology.
2-25. CLASSIFICATION OF HELMINTHS
Helminths are found in two phyla of the subkingdom Metazoa (multicellular
animals):
a. Phylum: Platyhelm1nthes (flatworms)
(1)
Class I: Cestoda (tapeworms)
(2)
Class II: Trematoda (flukes)
b. Phylum: Aschelminthes
Class I: Nematoda (roundworms, threadworms)
2-26. CESTODES (TAPEWORMS)
a. The tapeworm has two stages: larva and adult. The length of an adult worm
varies, according to the species, from 3-8 mm to 25 or 30 feet. The adult form has a
small head (scolex) and varying numbers of segments (proglottides) (figure 2-15 A&B).
The head attaches itself to the intestinal wall of the host by means of suckers.
Segments form from the head, receiving their nourishment through absorption, since the
worm has no alimentary tract. Each mature segment is a sexually complete
hermaphrodite (possessing both male and female sex organs), capable of producing
thousands of eggs. Treatment that fails to dislodge the head is ineffective, since the
head will immediately begin to replace the lost segments. In most instances a cestode
requires both an intermediate host (where certain stages of development occur) and a
definitive host (where the adult worm lives and produces ova) to complete its life cycle.
Table 2-8 lists the principal cestodes affecting man.
b. When eggs or segments of most tapeworms are passed from the definitive
host (man), they are ingested by the intermediate hosts (ruminants, swine, and so forth)
while grazing or rummaging for food. The larval stage, a hexacamth oncosphere, hatches
and encysts as a cysticercus or cysticercoid larva in the muscles or various organs of
the intermediate host. Therefore, the eggs are infective to man and may encyst in
tissue as a cysticercus larva resulting in severe complications. In the life cycle of the
large fish tapeworm of humans, the eggs must reach water where a larval stage
(coracidium) emerges and is swallowed by a small fresh-water crustacean called a
MD0151
2-34



Medical News
A 65-Million-Year Rectal Foreign Body? That's Improbable!
(MedPage Today) -- The revealing of the self through ......
medpagetoday.com
CMS Proposes 1.1% Hospital Pay Raise for 2016
(MedPage Today) -- Hospitals that don't participate in quality reporting...
medpagetoday.com
House Panel Considers Medicare Reform for Post-Acute Care
(MedPage Today) -- Spending on post-acute care has outpaced most...
medpagetoday.com
New research shows how to tackle obesity
One size does not fit all when it comes to...
medicalxpress.com
Tweet of the Week: Candy Anatomy
(MedPage Today) -- Here's what happens when a med student...
medpagetoday.com
Someone Wants All That FitBit Data
(MedPage Today) -- Dietitians would be glad to evaluate data...
medpagetoday.com
Teamwork Cuts In-Hospital Observation Time
(MedPage Today) -- Lengths of stay cut substantially at one...
medpagetoday.com
New approaches for early diagnosis of Alzheimer's
Mild cognitive impairment, or MCI, may be one of Alzheimer's...
medicalxpress.com
Endovascular Clot Removal Wins Again (CME/CE)
(MedPage Today) -- Reduced disability with thrombectomy in REVASCAT trial....
medpagetoday.com
Doc Facebook, Avoiding Burnout: Healthcare Career Insights
(MedPage Today) -- Must-reads about the latest news and trends...
medpagetoday.com
Scope wins award for its “creative and effective approach” to promoting academic medicine
We’re happy to announce that Scope is a 2015 GIA...
scopeblog.stanford.edu
Kids with ADHD must squirm to learn, study says
For decades, frustrated parents and teachers have barked at fidgety...
medicalxpress.com
Hospital Leader: An Interview With Toronto's Adina Weinerman, MD
(MedPage Today) -- What strategies can streamline code status documentation?...
medpagetoday.com
Friday Feedback: What's Next for Medicare?
(MedPage Today) -- SGR has been repealed, but what does...
medpagetoday.com
USDA confirms bird flu at 5th South Dakota turkey farm
Five commercial turkey farms in South Dakota have now been...
medicalxpress.com
Glaxo recalls flu vaccine due to potency problem
GlaxoSmithKline is recalling remaining doses of a popular four-in-one flu...
medicalxpress.com
From beef tongue to beef on weck, menus tell culinary story
Before beef on weck and chicken wings became staples of...
medicalxpress.com
Cohen's Brain Bits: Dream On
(MedPage Today) -- REM sleep behaviors offer opportunity for early...
medpagetoday.com
Artificial blood vessel lets researchers better assess clot removal devices
Researchers at the University of California, San Diego School of...
medicalxpress.com
Mortality Equal With Simultaneous vs. Staged Hip Replacement (CME/CE)
(MedPage Today) -- Survival similar after 30 and 90 days,...
medpagetoday.com
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +