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
Antibodies to brain proteins may trigger psychosis
Antibodies defend the body against bacterial, viral, and other invaders....
medicalxpress.com
Community nurses urged to highlight dangers of female genital mutilation
In their trusted professional capacity, community nurses are well placed...
medicalxpress.com
Women unaware of specialist phone services in late pregnancy
Researchers in England have found women are accessing advice via...
medicalxpress.com
Biomarker for fatty liver disease
40 percent of people in the EU suffer from non-alcoholic...
medicalxpress.com
Study to examine computer-based decision aids to help in lupus therapy
Researchers at the University of Alabama at Birmingham are enrolling...
medicalxpress.com
Elevated childhood weight may increase susceptibility to eating disorders
What causes people to develop eating disorders?...
medicalxpress.com
Largest genome-wide study reveals genes driving obesity
In obesity, some people store fat evenly throughout the body...
medicalxpress.com
New drug resistance mechanism has implications for breast, ovarian cancer treatment
Research to understand why hereditary cancers develop resistance to a...
medicalxpress.com
Smoking when pregnant increases cancer risk for daughters
A new study has found women who smoke when pregnant...
medicalxpress.com
Study shows longer-term cytomegalovirus treatment effective for symptomatic babies
Babies treated for symptomatic cytomegalovirus (CMV) infection for six months,...
medicalxpress.com
Daylight saving time's 'spring forward' can cause problems, expert says
Daylight saving time begins at 2:00 a.m. Sunday—and while you'll...
medicalxpress.com
Family interventions reduce smoking rates in children and adolescents
A global review by Canada's University of Calgary and QUT...
medicalxpress.com
Study shows benefits of fluoride to children
A study showing that tooth decay in Logan-Beaudesert children has...
medicalxpress.com
Students throw away less food with new healthier school lunches
After the U.S. Department of Agriculture's healthier school meal standards...
medicalxpress.com
Stigma of mental illness in India linked to poverty
The stigma surrounding people with severe mental illness in India...
medicalxpress.com
Dental students warn about hidden sugar in energy drinks and snacks
A team of dental students from Plymouth University Peninsula Schools...
medicalxpress.com
Australia leads world in skin cancer incidence but lacks reporting
Research published this week in the Australasian Journal of Dermatology...
medicalxpress.com
Sun damage causes genetic changes that predispose children and adolescents to melanoma
The St. Jude Children's Research Hospital—Washington University Pediatric Cancer Genome...
medicalxpress.com
US must respond to global health outbreaks, say bioethicists
Last summer, West Africa fell into the grip of a...
medicalxpress.com
Brain structure varies depending on how trusting people are of others, study shows
A recent study from the University of Georgia shows differences...
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 +