a summary of phylum nematoda and some of its species

1. The Roundworms

2. All are parasitic
11 known species compromise the genus
2 main clades
1. Encapsulated
 species in which the host muscle cells they invade
become surrounded by a collagen capsule
2. Non-encapsulated
 no encapsulation occurs in the host muscle

3.  The five species (and three genotypes yet to be
defined taxonomically) that comprise the
encapsulated clade parasitize only mammals
 Three species comprise the non-capsulated clade
 One infects mammals and birds
 Other two species infects mammals and reptiles
 There are only two of these parasites, T.
papuae and T. zimbabwensis, known to complete
their entire life cycle independently of whether the
host is warm-blooded or cold-blooded

4. Trichinella papuae Trichinella zimbabwensis

5.  Greek: trichinos = of hair, -ella = diminutive
 Latin: Trichinella spiralis means spira, which is a
reference to how this organism coils up in its host
 Well known for its parasitic lifestyle
 Belongs to the first clade
 Main hosts are meat eating animals
 Resides within skeletal muscles
 Disease caused is “trichinosis”

6.  Buccal cavity
 one of the most important structures for
adaptation developed
 Has a very similar function to our mouth
 Contains teeth to help the organism to adhere to
the substrate
 Supplies the organism with a place to take up
nutrients from its surroundings

7.  Hydrostatic skeleton
 Helps with movement
 Tail
 Helps in locomotion
 Supplies a place for claudal glands
 responsible for secreting an adhesive mucus
that helps this organism stick to the substrate
of interest
 Amphids
 Specialized sensing structures
 Located on the lateral sides of the head
 Gives the organism the ability to sense and then
adapt to their surroundings

8.  Simple nervous system
 Consists of dorsal and ventral nerve cords
 allows them to interpret information coming
from their sensory organs such as the amphids
 Enables them to react to their environment better
and have an increased chance of survival
 Cuticle
 located on the external aspect of the worm
 is shed off to allow these organisms to grow and
develop
 larger body size all results in a discount
metabolic rate per gram of tissue

10.  Encysted nematode is ingested
 Travel to the stomach to be digested
 digestive functions of the stomach allow the
nematodes to change from their encysted to their
active forms
 Molts four times for the first 34 hours
 Female releases pheromones to attract the male
 Male coils itself around the females genitals
 Male then inserts its spicule/s into female’s genitals
where the amoeboid sperms will crawl
 When eggs are fertilized, the mother will not release
the eggs unless they have hatched within its uterus
 Usually the 5th or 6th day of infection

12.  Greek: enteron = intestine, bios = life
 Has the broadest geographic range of any helminth
 Small, white, and thread-like
 Females: ranging between 8-13 mm x 0.3-0.5 mm
 Possess a long pin-shape posterior end
 Males: ranging between 2-5 mm x 0.1-0.2 mm
 Dwells primarily in the cecum of the large intestine
 Females migrate at night to lay 15,000 eggs on the
perineum

14.  Flattened asymmetrically on one side
 Ovoid
 Approximately 55 mm x 25 mm in size
 Embryonate in six hours
 Can remain viable for about twenty days in a moist
environment
 Viable eggs and larvae were found in the sludge of
sewage treatment plants in Czechoslovakia in 1992

15.  High prevalence in countries with a temperate
climate
 approximately 200 million people are infected
internationally
 The most common intestinal parasite
 Serves as an exception to the general rule that
intestinal parasites are uncommon in affluent
societies
 Does not need to rely on a vector for transmission
 Infection usually occurs via ingestion of infectious
eggs by direct anus-to-mouth transfer by fingers

17.  Scotch tape test
 Most common test
 A clear adhesive cellulose tape is applied to the
anal area early in the morning before bathing or
defecation
 It is then observed under the microscope for the
presence of eggs
 These eggs may also be stained blue with
lactophenol cotton blue, which aids in detection
and identification
 Sensitivity of this test when performed for three
consecutive mornings is 90%

18.  Bathe when you wake up to help reduce the egg
contamination
 Change and wash your underwear each day.
Frequent changing of night clothes are recommended
 Change underwear, night clothes, and sheets after
each treatment. Because the eggs are sensitive to
sunlight, open blinds or curtains in bedrooms during
the day
 Personal hygiene should include washing hands after
going to the toilet, before eating and after changing
diapers
 Trim fingernails short
 Discourage nail-biting and scratching bare anal areas.
These practices help reduce the risk of continuous
self reinfection

19.  Filial nematode that is a thread-like worm
 Female: 10 cm long and 0.2 mm wide
 Male: about 4 cm long
 Adults reside and mate at the lymphatic system
 Can produce up to 50 000 microfilaria per day
 microfilaria are 250-300 µm long, 8 µm wide and
circulate in the peripheral blood and can live as is up
to 12 months
 Adult s take 6 to 12 months to develop from the
larval stage and can live between 4 and 6 years

21.  Interactions are with humans and mosquitoes
 Mosquitoes are intermediate hosts
 Humans are definitive hosts
 Microfilariae inhabits the mosquito and the mosquito
then transfers the microfilariae to humans when it
takes a blood meal
 Some of the common vectors are the Culex,
Anopheles, and Aedes mosquito
CULEX ANOPHELES AEDES

22. RED: Endemic
PINK: Unknown
GREEN: Unaffected

23.  This disease is transferred by mosquitoes and is
found mainly in the tropics and sub-tropics
 Very rarely found in Western countries
 Onset of symptoms is usually slow, but after a couple
of years, the lymphatic system will no longer work
like it should
 Lymph nodes become enlarged and clogged
 Swelling, discoloration, and thickening of the skin
occurs
 Without treatment, the tissue infected with
Lymphatic filariasis develops into Elephantiasis

24.  The thickening of skin and other tissues to produce
huge growths on a person’s body
 Growths result from the blocking of lymphatic
vessels by the parasite
 Usually found in the lower regions of the body
 W. Bancrofti can affect the arms, legs, and breasts