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
Islet cell transplantation restores type 1 diabetics' blood sugar defense mechanisms
Type 1 diabetes (T1D) patients who have developed low blood...
medicalxpress.com
Irish face new abortion row over brain-dead woman
Ireland is debating its constitutional ban on abortion again amid...
medicalxpress.com
Preventing hepatitis C patients from being lost in the health-care system
A new study shows that many patients infected with the...
medicalxpress.com
Tailor-made cancer treatments? New cell culture technique paves the way
In a development that could lead to a deeper understanding...
medicalxpress.com
Specific oxidation regulates cellular functions
For a long time, hydrogen peroxide has been considered as...
medicalxpress.com
Researchers ferret out a flu clue
Research that provides a new understanding as to why ferrets...
medicalxpress.com
Researchers treat heart attacks with new gene therapy based on telomerase enzyme
The enzyme telomerase repairs cell damage produced by ageing, and...
medicalxpress.com
New disease mechanism discovered in lymphoma
Programmed cell death is a mechanism that causes defective and...
medicalxpress.com
Why do parents who usually vaccinate their children hesitate or refuse?
A new study by Dr. Anat Gesser-Edelsburg, Dr. Yaffa Shir-Raz...
medicalxpress.com
Low premiums yet big bills – why high-deductible health plans need reform
A few years ago, we met Angie, a hair salon...
medicalxpress.com
First of new generation of cancer drugs granted European approval
A new drug for ovarian cancer, developed by researchers at...
medicalxpress.com
Wild blueberries (bilberries) can help tackle the adverse effects of a high-fat diet
Eating bilberries diminishes the adverse effects of a high-fat diet,...
medicalxpress.com
Researchers hope patent can pave way to future treatments of heart, lung disease
A Kansas State University research team has received a patent...
medicalxpress.com
Low-dose lithium prevents Parkinson's symptoms in aged mice with a human mutation for the disease
Low-dose lithium prevented symptoms of Parkinson's disease in aged mice...
medicalxpress.com
Athletes urged to drink when thirsty after Rottnest swim incident
Long distance swimmers are being urged to drink when they...
medicalxpress.com
Is the government stalling on plain cigarette packaging?
We are still waiting to hear whether the UK government...
medicalxpress.com
Morning Break: Obesity as Disability, Fat-Fighting Holiday Decor
(MedPage Today) -- Health news and commentary from around the...
medpagetoday.com
Christmas a risky time for vulnerable according to indigenous expert
Christmas is a risky time for many people, young and...
medicalxpress.com
Instant noodles recalled as Taiwan food scare widens
Taiwanese authorities on Thursday ordered a leading food company to...
medicalxpress.com
11th Sierra Leonean doctor dies from Ebola
One of Sierra Leone's most senior physicians died Thursday from...
medicalxpress.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 +