Helminths, also known as parasitic worms, are multicellular eukaryotic parasites that live in and feed on living hosts. They include nematodes (roundworms), cestodes (tapeworms), trematodes (flukes), and monogeneans. Trematodes have two suckers, an oral and ventral sucker, and a simple digestive system without an anus. They reproduce through an intermediate host, often a snail, and then a definitive host, where they can cause disease. One example is Fasciola hepatica, the sheep liver fluke, which uses a snail and water plants as intermediate hosts before infecting the liver of mammals like sheep, cattle, and humans

1. PARASITIC WORMS
(HELMINTHS)
Dr. Souzan Eassa
Department of Microbiology
1Souzan Eassa

2. HumanParasitology
Medical
Helminthology
Medical
Protozoology
Medical
Arthropodology
• Phylum Nemathelminths
- Class Nematoda
• Phylum Platyhelminthes
1- class Trematoda
2- Class Cestoda
• Phylum Lobosea
• Phylum Zoomastigophorea
• Phylum Ciliophora
• Phylum Sporozoa
• Phylum Insecta
• Phylum Arachnida
• Phylum Crustacea
• Phylum Chilopoda
2Souzan Eassa

3. (4)
Turbellaria
Helminthes
Are eukaryotic multicellular parasites living in and feeding on
living hosts, receiving nourishment and protection while disrupting
their hosts' nutrient absorption, causing weakness and disease.
(2)
Cestodes (tapeworms)
Roundworms
(3)
Trematodes (flukes)
Flatworms (Platyhelminthes)
(1)
Nematodes
Helminthes
(3)
Monogeneans
3Souzan Eassa

4. • Phylum Platyhelminthes
1- Class Cestoda (Tape worms)
2- Class Trematoda (Flukes or Flat worms)
• Phylum Nemathelminths
Class Nematoda (round worms)
4Souzan Eassa

5. INTRUDUCTION
TO
Trematodes (Flukes)
Dr. Souzan Eassa
Department of Diagnosis Diseases
5Souzan Eassa

6. There are about 9000 species of
trematodes all of which are parasitic. Most
Trematodes are parasites of vertebrates.
Trematods are multicellular eukaryotic
helminths unsegmented dorso-ventrally
flattened.
Most adult are bilaterally symmetric,
leaf-shaped or tongue-like and covered
with a cuticle (tegument).
The tegument may be smooth or spiny
and protects the parasite against its host
(e.g. against digestive enzymes).
General Morphology
6Souzan Eassa

7. Digestive tract
Have two suckers, an oral and a
ventral sucker.
Oral cavity leads to muscular
esophagus.
Intestine branches into
two cecae, which end
blindly near the
posterior end of the
worm.
Simple digestive
system, which is no
anus - waste
products are
regurgitated. 7Souzan Eassa

8. Reproductive system
Most are hermaphroditic and
capable of self-fertilization
except for schistosomes
(diecious).
Uterus is the largest organ and
they have a single ovary.
Dendritic testes.
a series of glandular structures
that produce egg shell
materials.
Uterus may be filled with
thousands of eggs.
8Souzan Eassa

9. General Reproducing
 A snail is the first (or intermediate)
host and a vertebrate (include
human) the final (or definitive
host).
 In some species there may be 2
or 3 intermediate hosts before the
definitive host is reached.
 A series of generations occurs in
the intermediate host, resulting in
the liberation of larvae known as
cercariae,
1.free swimming larvae
2.given off by infected snail
3.penetrate the skin of the
human definitive host
9Souzan Eassa

10. Liver/ Lung:
• Fasciola hepatica
Blood:
• Schistosoma Spp.
mansoni
haematobium
• japonicum
Intestinal:
• Fasciolopsis buski
Trematodes (Flukes) of Human being
10Souzan Eassa

11. 11
Medically significant trematodes
Reservoir
host
Biological
vector
Intermediate
host
Common
name
trematodes
Sheep, cattle,
human
Water
planets(eg. ,
water
tercress
snailSheep liver
fluke
Fasciola hepatica
Primates,
rodents,
domestic pets,
human
nonesnailBlood flukeSchistosoma
Souzan Eassa

12. Fasciola hepatica
Sheep liver Fluke
12Souzan Eassa

13. Fasciola hepatica
Fasciola hepatica, is the largest
flukes in the world, also known as
the common liver fluke or sheep
liver fluke.
 Infects liver of various
mammals, including humans.
The disease caused by the fluke
is called fascioliasis.
 F. hepatica is world-wide
distributed and causes great
economic losses in sheep and
cattle.
13Souzan Eassa

14. 14Souzan Eassa

15. Fasciola hepatica
The adult (30mm-13mm), leaf
shape with anterior end being
broader than the posterior end and
has cone shaped projection.
he intestinal ceca are highly
dendritic and extend to near the
posterior end of the body.
Two sucker the oral and ventral.
The ovary and tests are highly
branched.
The eggs of Fasciola hepatica are
operculated and average 140 um-
7um
Egg and egg capsule with emerging miracidium
of Fasciola hepatica. 400x
15Souzan Eassa

16. People become infected
with Fasciolopsis when they
eat raw or undercooked
aquatic plants that have the
organism (metacercariae)
encysted on them.
Intermediate host is snail.
The final host is mammalian
mostly human, sheep and
cattle.
A form of infection known
as halzoun that is specific
to Middle East in
contracted by eating the
raw liver of infected animal
Fasciola hepatica
16Souzan Eassa

17. 17Souzan Eassa

18. F. hepatica requires an aquatic snail as an intermediate host such as
Galba truncatula, in which the parasite can reproduce asexually.
 From the snail, minute cercariae emerge and swim through pools of
water in pasture, and encyst as metacercariae on nearby vegetation.
From here, the metacercariae are ingested by the ruminant, or in some
cases, by humans eating un-cooked foods such as water-cress.
Contact with low pH in the stomach causes the early immature juvenile
to begin the process of excysment .
In the duodenum, the parasite breaks free of the metacercariae and
burrows through the intestinal lining into the peritoneal cavity.
The newly excysted juvenile does not feed at this stage, but once it finds
the liver parenchyma after a period of days, feeding will start.
This immature stage in the liver tissue is the pathogenic stage, causing
anaemia and clinical signs sometimes observed in infected animals.
The parasite browses on liver tissue for a period of up to 5-6 weeks and
eventually finds its way to the bile duct where it matures into an adult
and begins to produce eggs.
Up to 25,000 eggs per day per fluke can be produced, and in a light
infection, up to 500,000 eggs per day can be deposited onto pasture by a
single sheep.
Life cycle
18Souzan Eassa

19. Four Symptomatic Patterns
1. Acute Phase
2. Chronic Phase
3. Halzoun
4. Ectopic Infection
Acute Phase
Rarely seen in humans
Fever, tender hepatomegaly, and abdominal pain are
frequent symptoms.
Vomiting, diarrhea, and anemia may also be present 19Souzan Eassa

20. Chronic Phase
More common in human
population.
Symptoms include: bilary cholic,
abdominal pain, tender
hepatomegaly, and jaundice.
In children: severe anemia is
common.
Inflammation of the bile ducts
eventually leads to fibrosis and a
condition called “pipestem liver”.
Severe infections can lead to
death 20Souzan Eassa

21. Halzoun & Ectopic Infection
Occurs when an
individual consumes
infected raw liver.
The adult worms can
cause considerable pain,
edema, and bleeding that
can interfere with
respiration.
Adults can live in biliary
ducts and cause
symptoms for up to 10
years.
In frequent, but can occur
in peritoneal cavity,
intestinal wall, lungs,
subcutaneous tissue, and
very rarely in other
locations.
21Souzan Eassa

22. Diagnostic Tests
After 4 months of
infection: direct
examination F. hepatica
eggs in a stool sample.
Prior to 4 months:
serological tests can be
used.
Ultrasound can be
used to visualize adult
flukes in the bile ducts.
22Souzan Eassa

23. Treatment
Bithionol for 5-10 day course
of oral at 30mg/kg body
weight.
Along with pharmaceutical
therapy, surgery may be
necessary in very extreme
cases to clear the biliary tract
23Souzan Eassa

24. Molluscicides (pesticides against molluscs ):
application of malluscicides to decrease the population
of Lymnaea snails.
Avoiding ingestion of raw watercress grown in endemic
areas.
Avoid eat raw or uncooked liver
Prevention
24Souzan Eassa

25. Souzan Eassa