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
UN: Goals helped lift one billion people from extreme poverty
A 15-year effort to implement eight goals adopted by world...
medicalxpress.com
New Brazil rules seek to cut Cesarean craze
New regulations aimed at rolling back Brazil's obsession with Cesarean...
medicalxpress.com
Teva to lift bid for Mylan: report
Israeli pharmaceutical giant Teva plans to increase its bid for...
medicalxpress.com
Religious groups could expedite response to biggest global health challenges of 21st century
Faith-based organisations [1] are crucial in achieving the promise of...
medicalxpress.com
Scientists lead consensus guidelines for thyroid cancer molecular tests
University of Pittsburgh Cancer Institute (UPCI) scientists recently led a...
medicalxpress.com
Study explains how dengue virus adapts as it travels, increasing chances for outbreaks
A researcher from The University of Texas Medical Branch at...
medicalxpress.com
Non-invasive technique may help detect skin and other cancers
Researchers have developed a non-invasive technique that allows clinicians to...
medicalxpress.com
Societal challenges and new treatments for Ebola virus disease
Since Ebola was first described in 1976, there have been...
medicalxpress.com
Dental pulp cell transplants help regenerate peripheral nerves
Peripheral nerve injuries often are caused by trauma or surgical...
medicalxpress.com
Simple heart scan may help identify patients at risk for premature death
A study in the online edition of Annals of Internal...
medicalxpress.com
What's the best walking aid for patients with COPD?
In a first-of-its-kind study, researchers have investigated the impact of...
medicalxpress.com
Illicit drug use may affect sexual function in men
In a study of 1159 males who illicitly used amphetamines,...
medicalxpress.com
Simply observing men with very low- and low-risk prostate cancer very effective and underused
Monitoring men with very low- and low-risk prostate cancers using...
medicalxpress.com
Five-year study sheds light on hospice care in assisted living facilities versus in the home
Researchers have found several key differences among people who receive...
medicalxpress.com
Кesearchers find two biomarkers linked to severe heart disease
Insulin resistance affects tens of millions of Americans and is...
medicalxpress.com
Nothing to snort over: Why snoring should be taken seriously
It’s the middle of the night—or maybe the middle of...
scopeblog.stanford.edu
Drinking alcohol while pregnant is common in UK, Ireland, and Australasia
Drinking alcohol while pregnant is common, ranging from 20% to...
medicalxpress.com
Heightened hospital weekend death risk common in several developed countries
The heightened risk of death after admission to hospital at...
medicalxpress.com
New smartphone app warns drinkers if they go over recommended daily/weekly units
A new smartphone app warns drinkers if they go over...
medicalxpress.com
Epigenetic driver of glioblastoma provides new therapeutic target
Cancer's ability to grow unchecked is often attributed to cancer...
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 +