Slide 2 Chapter 15: Phylum Nematoda: The Roundworms Slide 3
Cryptosporidium Protozoan pathogen Drinking contaminated water
Diarrhea/ Severe in immune-compromised Slide 4 Elephantiasis
Filarial worm (Nematode) Transmitted by mosquitoes Swelling of
lymphatic system Slide 5 Anisakis Nematode Ingesting fish/marine
mammals Slide 6 Tapeworm Parasitic flatworm Ingestion of
contaminated/undercooked meat Malnutrition/ neurological damage
Slide 7 Slide 8 Giardia Protozoan parasite Ingestion of
contaminated food, water, soil Intestinal infection, diarrhea,
abdominal pain Slide 9 Roundworms The common name for phylum
Nematoda is roundworms. They are among the most numerous of all
animals. Roundworms are pseudocoelomates Slide 10 Nematode =
Thread? In Greek, nematos actually means thread, hence why they are
called nematodes. Slide 11 What is a Roundworm? Roundworms are
slender, unsegmented worms with tapering ends. They can be
microscopic or up to a meter in length. Most species of roundworms
are free-living, inhabiting soil, salt flats, aquatic sediments,
and water from polar to tropical regions. Still others are
parasitic and live in hosts that include almost every kind of plant
and animal. Slide 12 What is a Roundworm? Nematodes parasitize
virtually every type of animal and many plants. Almost all species
of vertebrates and many invertebrates serve as hosts for one or
more types of parasitic nematodes. Slide 13 What is a Roundworm?
Nematodes have a digestive tract with two openings. This body plan
is often called atube-within-a-tube. The outer tube is the body
wall and the inner tube is the digestive tract. Slide 14 Form and
Function in Roundworms Roundworms have specialized tissues and
organ systems that carry out essential body function. In general,
the body systems of free-living roundworms tend to be more complex
than those of parasitic forms. Slide 15 Feeding Many free-living
roundworms are carnivores that use grasping mouthparts and spines
to catch and eat other small animals. Some soil-dwelling and
aquatic forms eat algae, fungi, or pieces of decaying matter. Other
nematodes digest the bacteria and fungi that break down dead
animals and plants. Slide 16 Response Nematodes have simple nervous
systems, consisting of several ganglia. Several nerves extend from
ganglia in the head and run the length of the body. These nerves
transmit sensory information and control movement. Roundworms have
several types of sense organs. Slide 17 Reproduction Roundworms
reproduce sexually, and most species of roundworms are dioecious
(male/female) They reproduce using internal fertilization: the male
usually deposits sperm inside the females reproductive tract.
Parasitic nematodes often have complex life cycles that involve two
or three different hosts or several organs within a host. Slide 18
Nematode Parasites Many nematodes are very important pathogens of
humans and domestic animals. Some of the nematodes we will discuss:
Roundworms Hookworms Pinworms Filarial Worms Slide 19 Roundworm
Ascaris lumbricoides occurs in up to 64% of people in some areas of
the southeastern U.S. More than 1.2 billion are affected worldwide.
Slide 20 Roundworm A female roundworm can lay 200,000 eggs per day,
passing out through the hosts feces. Viable eggs remain after signs
of fecal matter have disappeared. Eggs can survive long periods in
the soil. Slide 21 Roundworm When a host swallows the eggs,
juveniles hatch and burrow through the intestinal wall. The
juveniles then are carried through the heart to the lungs. When at
the lungs, they break into the alveoli and are carried up to the
trachea. Juveniles are coughed up and swallowed, then mature in the
intestine two months after they were swallowed. They feed on
intestinal contents and may block or perforate the intestines.
Slide 22 Slide 23 Slide 24 Hookworms Hookworms are so named because
the anterior (head) end curves dorsally, resembling a hook. Necator
americanus is most common species. They have large plates in their
mouths that cut into the intestines so that they can suck on the
hosts blood. Slide 25 Slide 26 Hookworms Hookworms pump more blood
than they can digest. A heavy infection can cause anemia. Eggs pass
in feces and juveniles hatch in soil where they can live off of
bacteria. If human skin comes in contact with the soil, infective
juveniles burrow through the skin to blood. Their life cycle is
similar to that of Ascaris. Slide 27 Slide 28 Slide 29 Pinworms
Pinworms are the most common worm parasite in the U.S., but causes
little disease. It is estimated that 30% of children and 16% of
adults in the U.S. have them. Adults live in the large intestine
and cecum. Slide 30 Pinworms Females, about 12 mm in length,
migrate to the anal region at night and lay eggs, causing itching.
Scratching the anal region contaminates hands and bedclothes. Slide
31 Scotch Tape Method Doctors usually diagnose pinworms by fecal
examinations and finding the eggs, but eggs are often not found in
feces. Many times the female pinworm will deposit her eggs on the
skin around the anus. Doctors have started using the scotch tape
method. Slide 32 Scotch Tape Method 1. The scotch tape method
consists of placing the sticky side of cellulose tape onto the anus
overnight. 2. The next morning the tape is umm...harvested and
placed under a microscope to search for eggs. Slide 33 Several
drugs are effective against it, and all members of the family
should be treated at the same time because the worms spread easily
through a household. Slide 34 Pinworms Eggs develop rapidly and
become infective within six hours at body temperature. When
swallowed, these eggs hatch in the anterior end of the small
intestine (the duodenum) and mature in the large intestine. Members
of this order have haploid (one set of chromosomes) males from
unfertilized eggs and diploid females from fertilized eggs. This is
known as haplodiploidy. Slide 35 Filarial Worms There are eight
species of filarial nematodes that infect humans. Some cause major
and serious diseases. About 250 million people in tropical
countries Slide 36 Filarial Worms Females can be as long as 100 mm
and can release live young into the blood and lymph. Slide 37
Filarial Worms Mosquitoes ingest the microfilariae when they feed.
The worms develop to the infective stage while inside the mosquito
and move into the mosquito bite wound when it feeds. Slide 38
Filarial Worm Diseases Filarial worms cause three main diseases in
their hosts: Elephantiasis River blindness Slide 39 Elephantiasis
Elephantiasis symptoms are apparent after long and repeated
exposure to filarial worms. It is marked by excessive growth of
connective tissue and enormous swelling of affected parts, such as
the legs and arms. Slide 40 Slide 41 Onchocerciasis: River
blindness River blindness is caused by a filarial worm that is
carried by black flies. It infects more than 30 million people in
parts of Africa, Arabia, Central America, South America, and
virtually all other tropical areas. Slide 42 Slide 43 Slide 44
