Digestive Tract Trematodes FAMILY ECHINOSTOMATIDAE - intestinal parasites recognized by their anterior collar of spines. Echinostoma - Chap. 17 Cosmopolitan parasite of ________________________________ – shows low host specificity Common definitive hosts in Wisconsin are ____________________________________________ _______ Human cases have been reported in the Orient, primarily Taiwan and Indonesia – _________species reported from humans
Transcript
Digestive Tract Trematodes
FAMILY ECHINOSTOMATIDAE - intestinal parasites recognized by their anterior collar of spines.
Echinostoma - Chap. 17
Cosmopolitan parasite of ________________________________ – shows low host specificity
Common definitive hosts in Wisconsin are ___________________________________________________
Human cases have been reported in the Orient, primarily Taiwan and Indonesia – _________species reported from humans
Taxonomy a mess – _____________described species. E. revolutum now confined to bird hosts; E. trivolvus is new name for species in mammals in Wisconsin.
Morphology of Adult Echinostoma
Adults are elongate, up to an inch in length.
Characteristic structure is: ____________________________________________ ______________________
Internal organs are distinct and easy to identify.
Morphology of Adult Echinostoma
Vitellaria Testes Mehlis’ gland Ovary
uterus
Collar of spines around oral sucker
Life Cycle of Echinostoma
Parasite shows low host specificity throughout cycle 1. Adults occur in _________________________________________________ 2. Eggs are released via the feces into an aquatic habitat. 3. Miracidia hatch, swim to snail, and penetrate ________________________(1st intermediate host).
Life Cycle of Echinostoma
4. Sporocysts and rediae occur within snail. Cercariae are released.
5. Cercariae penetrate ________________________________________________(2nd intermediate hosts) and encyst as metacercariae. 6. Definitive host is infected by ingesting 2nd intermediate host, metacercariae excyst in stomach, and adults maturein small intestine.
Echinostoma
How are humans infected? ______________________________ ____________________________________________________
PATHOLOGY - inflammation of the small intestinal mucosa at the attachment site.
• Symptoms are intestinal pain and diarrhea.
• Parasite is never life-threatening.
FAMILY HETEROPHYIDAE - family of tiny flukes in the small intestine of fish-eating birds And mammals. Two heterophyids are important human parasites.
Heterophyes heterophyes – Chap. 18, p. 291-292
Adults are small parasites in the human small intestine.
Distributed in the Orient (Japan, Korea, China, Taiwan, and the Philippines), Africa, and Asia Minor.
2. Eggs are released in feces and must be eaten by aquatic ____________________ (1st intermediate)
3. Miracidia hatch in snail and undergo sporocyst and redial generations.
4. Free-swimming cercariae are released from snail and penetrate a _____________________________ (2nd intermediate) where metacercariae encyst in the muscle.
5. Humans become infected ______________________________________________________________. Adults mature in small intestine in 7-10 days.
In heavy infections, the mucosa and submucosa may become ulcerated.
EGGS can get into the bloodstream and may be carried to the _____________________ where they cause a severe tissue reaction called ____________________________________.
• 14% of fatal heart attacks in the Philippines
Heterophyes
DIAGNOSIS - Identify eggs in the feces. Eggs are similar to Clonorchis.
(We do not have slides of Heterophyes eggs.)
TREATMENT -
Metagonimus yokagawai
Common heterophyid trematode in humans in the Orient (overlaps with Heterophyes), Russia, and the Balkan countries.
There is no gonotyl. Seminal vesicle and seminal receptacle are ___________.
acetabulum
Metagonimus
LIFE CYCLE, PATHOLOGY, DIAGNOSIS, AND TREATMENT is identical to that of Heterophyes.
STRIGEOID TREMATODES - 2 families of trematodes that inhabit the small intestine of birds and mammals - Chapter 16, p. 247-249
Alaria spp.
Many species of Alaria occur in the small intestine of carnivores.
Alaria canis in dogs.
Alaria americana in foxes.
Alaria mustelae in mink and weasels.
Alaria taxideae in badgers (we will examine this one in lab)
Morphology of Adult Alaria
Body is divided into 2 regions:
1.
2.
Three suckers are present - _____________________________________________________________________
Common genital pore is posterior.
Life Cycle of Alaria
LIFE CYCLE is unusual in that 3 or 4 hosts may be involved.
1. Adults in small intestine of carnivore definitive host.
2. Eggs in feces hatch in water releasing miracidia that penetrate _____________________ first intermediate host.
3. Cercariae released from snail penetrate a _____________________ second intermediate host and transform into an unencysted stage called the ______________________ .
Life Cycle of Alaria
4. If tadpole is eaten, frogs, snakes, mice can serveas _____________________________________________. Mesocercariae undergo no further development.
5. Carnivore becomes infected by eating tadpole or paratenic host.
Life Cycle of Alaria
6. ______________________ penetrate the intestine, burrow through the diaphragm, and reach the lungs. Here they become _______________________
7. Metacercariae migrate up the respiratory tree and are swallowed.
Adults in the carnivore's ______________________
Pathology of Alaria infections
PATHOLOGY - Adult parasites cause severe damage to the small intestine of the carnivore.
Often occur together in clumps.
Forebody
Hindbody
Pathology of Alaria infections
HUMAN INFECTION – few cases involved infection with _______________________________
• most cases involved mesocercariae migrating to the eye
• one fatal case occurred in Canada from ingestion of poorly cooked _____________________________
Mesocercariae were identified in nearly every organ at autopsy.
Photo shows mesocercaria in lung
Uvulifer ambloplitis
is associated with ____________________________
Fish are the 2nd intermediate host – common in ____________________________
____________________________
Uvulifer
Adults occur in the ________________________________________________ (fish-eating birds). This is the only definitive host – shows ____________________________________
Uvulifer
Blackspot is caused by the _____________________________ in the fish muscle and fins. ___________________________ is produced by the fish in response to the parasite and is deposited into the metacercarial cyst.
Uvulifer
LIFE CYCLE involves: (1) _______________________________ (2) ____________________________________ (3) ___________________________ (only one - shows high host specificity)
Uvulifer
What happens if humans eat poorly cooked fish with blackspot?
