TREMATODES Flashcards
Like the cestodes, the trematodes belong to the phylum
Platyhelminthes
For classification purposes, the flukes may be divided into four categories based on the areas of the body that primarily harbor the parasites:
intestinal, liver, lung, and blood.
Commonly known as the [?], these parasites vary in egg, larva, and adult morphology and production processes.
flukes
The trematodes can be divided into two groups, the [?] that infect organs and are foodborne, and the blood flukes or schistosomes that are [?] and infect by direct penetration.
hermaphroditic (self-fertilizing) flukes
dioecious (parasites that reproduce via separate sexes)
Common to all trematodes is their complex life cycle, which almost always include [?] as an intermediate host.
mollusks (snails)
- Morphology: [?] along a long axis and are usually [?], EXCEPT for the blood flukes which are [?]; [?] varies.
Broadly oval/leaf-like, bilaterally symmetrical ;
flattened dorsoventrally
cylindrical; shape and size
- Excretory system: bilaterally symmetrical and open at posterior end with
FLAME CELLS or SOLENOCYTES
• With an [?] extending from the mouth to a short narrow esophagus
oral sucker and a globular pharynx
• [?] is situated at the anterior end of the worm and is equipped with muscular suckers with spines or hooklets.
Oral cavity
Some species possess a large ventral sucker (?) posterior to the oral sucker
ACETABULUM
• bifurcates in front of the ventral sucker into a pair of blind intestinal caeca which may be simple or branched or may reunite to form a single caecum
Esophagus
• Digestion is predominantly an
extra-cellular process
- Nervous system: composed of a group of paired ganglion cells disposed like saddle on the dorsum of
pharynx/esophagus
• All are hermaphrodite/monoecious EXCEPT the
blood flukes
• All are
Oviparous
• Eggs are provided with a lid called [?], EXCEPT the blood flukes
operculum
• The male reproductive system is located at the [?] of the body.
posterior half
It consists of the [?]
prostate gland, seminal vesicle, cirrus, vas deferens, vas efferens, and testes
• The female reproductive system is composed of
uterus, mehli’s gland, ootype, vitellaria, seminal receptacle, and ovary.
Movement is either
through contraction, elongation or flexion
• The trematodes need [?] to complete their life cycle
body of water
• All require 2 intermediate hosts EXCEPT for
blood flukes
• All trematodes lay eggs which upon embryonation, give rise to a ciliated embryo known as [?] → [?] (Dioecious flukes) →[?] (Monoecious flukes)
MIRACIDIUM; CERCARIA; METACERCARIA
- Stages of Trematodes:
a. Egg stage b. Larval stages
– a ciliated embryo that hatches in water
▪ Miracidium
– sac like structure
▪ Mother sporocysts
/daughter sporocysts
▪ Rediae
– tailed and free swimming
▪ Cercaria/daughter redia
– the encysted resting or maturing stage
▪ Metacercaria
Testes types:
✓ Branched, arranged in tandem:
F. hepatica, C. sinensis, F. buski
✓ Lobulated, arranged side by side:
P. westermani
✓ Deeply lobulated, arranged in tandem or dumbbell testes:
E. ilocanum
✓ Oval or round, arranged side by side or slightly oblique:
H. heterophyes, M. yokogawai
✓ Lobular, obliquely arranged:
O. felineus
✓ Oval, round:
M. yokogawai
Ovary types:
✓ Branched:
F. hepatica, F. buski
✓ Lobulated:
C. sinensis, O. felineus, P. westermani
✓ Oval or rounded:
E. ilocanum, H. heterophyes, M yokogawai
Vitellariae types:
✓ Highly branched:
F. hepatica, C. sinensis
✓ Finely granular vitelline follicles:
P. westermani, F. buski
✓ Medium-sized vitelline follicles:
E. ilocanum
✓ Compressed vitelline follicles:
O. felineus
✓ Polygonal:
H. heterophyes, M. yokogawai
Intestinal ceca types:
✓ Branched:
F. hepatica
✓ Simple:
F. buski, E. ilocanum, M. yokogawai, H. heterophyes, C. sinensis, O. felineus
✓ Simple but arranged in zigzag fashion:
P. westermani
Cercaria types:
o Lophocercus:
❖ Simple tailed:
❖ Keeled-tail:
F. hepatica, F. buski, E. ilocanum
C. sinensis, O. felineus, H. heterophyes
Microcercus:
P. westermani
Forked tail:
Schistosoma
2 intermediate hosts:
▪ Snails
▪ Fresh water
Monoecious
1 intermediate host:
▪ Snails only vegetations
Dioecious
Infective stage Metacercariae
Monoecious
Infective stage Cercariae
Dioecious
Operculated
Monoecious
Non-operculated with spines
Dioecious
Straight-tailed
Monoecious
Forked or bifurcated
Dioecious
Flat, leaf-like (hermaphrodites)
Monoecious
Cylindrical, separate sexes
Dioecious
Lungs, liver, and separate intestines
Monoecious
Blood vessels
Dioecious
- Liver flukes
a. Fasciola hepatica
b. Fasciola gigantica
c. Clonorchis sinensis
d. Opistorchis felineus
e. Dicrocoelium dendriticum
- Intestinal flukes
a. Fasciolopsis buski
b. Echinostoma ilocanum
c. Heterophyes heterophyes
d. Metagonimus yokogawai
- Lung fluke
a. Paragonimus westermani
- Blood flukes
a. Schistosoma japonicum
b. Schistosoma mansoni
c. Schistosoma haematobium
are considered as the most important digenetic parasites of man inhabiting the veins of their vertebrate hosts.
dioecious flukes
The usual portal of entry into the definitive host is the skin.
dioecious flukes
Members of this group parasitize fishes, turtles, birds, and mammals.
dioecious flukes
There are at least four species (S. haematobium, Schistosoma mansoni, Schistosoma japonicum, and S. mekongi) that are important agents of disease in man, whereas others are incidental or potential human parasites.
dioecious flukes
Species parasitizing man usually inhabits the mesenteric-portal and caval venous blood vessels.
dioecious flukes
Males ➢ Larger than the female adult worm measuring about 12-20 mm by 0.5 to 0.55 mm in diameter
dioecious flukes
Males ➢ Grayish in color and is attached by its suckers to the wall of the vessel
dioecious flukes
Males ➢ With a gynecophoral canal on the ventral side which functions to surround almost completely the female adult facilitating copulation
dioecious flukes
Females ➢ Average size is 26 mm in length by 0.3 mm in diameter
dioecious flukes
Females ➢ Thread-like structure
dioecious flukes
China, Japan, Indonesia, Thailand, Cambodia, Philippines
dioecious flukes
The trematodes pass through three morphologic forms during their life cycle – eggs, multiple larval stages, and adult worms.
MONOECIOUS FLUKES
The eggs, which are the primary morphologic form recovered in human specimens, vary in appearance.
MONOECIOUS FLUKES
Some contain a lid-like structure called operculum that under appropriate conditions, flips open to release its contents for further development, such as in Fasciolopsis and Fasciola.
MONOECIOUS FLUKES
Based on the organism’s life cycle, the trematodes may be placed into two categories, those that reside in the intestine, bile duct, or lung (organ dwelling).
MONOECIOUS FLUKES
Human infection of such organ-dwelling flukes occurs following ingestion of water plants, fish, crab, or crayfish contaminated with encysted form of the parasite known as metacercaria.
MONOECIOUS FLUKES
These large digenetic trematode species belong to the
Family Fasciolidae
They are parasites found in the liver and biliary passages of humans and herbivorous mammals.
Family Fasciolidae
are the causative agents of fascioliasis.
Fasciola hepatica (temperate liver fluke) and Fasciola gigantica (tropical liver fluke)
The mode of transmission of Fasciola hepatica and Fasciola gigantica is through ingestion of [?] encysted on edible water plants or by drinking water contaminated with [?].
metacercaria
Thus, the life cycle of Fasciola hepatica and Fasciola gigantica is the same.
Family Fasciolidae
These small digenetic trematodes (C. sinensis, O. felineus, O. viverrini) belonging to family [?] are parasites of the bile duct and gall bladder of humans and fish-eating mammals.
Family Opisthorchiidae
The life cycle of these liver flukes is similar as well as their mode of transmission.
Family Opisthorchiidae
The mode of transmission is via ingestion of the metacercaria of the parasite present in infected fish (2nd IH) that is eaten raw or undercooked.
Family Opisthorchiidae
The distinctive feature of [?] is a head collar bearing one or two row of spines.
Family Echinostomatidae
The tegument usually bears spines or scales, especially over the anterior part of the body.
Family Echinostomatidae
are parasites of birds and mammals, and usually inhabits the intestine.
Family Echinostomatidae
are small or minute intestinal parasites of birds and mammals.
Family Heterophyidae
They are generally less than 1 mm long, pyriform or ovoid, with spiny integument.
Family Heterophyidae