Helminths

• Helminth is a general term for a parasitic worm.

• Trematodes are Platyhelminthes or flatworms (flukes )

Trematodes

• Clonorchis sinensis

• Fasciola hepatica

• Paragonimus westermani

• Schistosoma haemotobium

• Schistosoma japonicum

• Schistosoma mansoni

Trematodes

•Trematodes, or flukes, are parasitic flatworms with unique life cycles:

-involving sexual reproduction in mammalian and other vertebrate definitive hosts and

-asexual reproduction in snail intermediate hosts.

Trematodes

•In humans they may be: • liver flukes which reside in the bile ducts • intestinal fluke •lung fluke •blood flukes (Schistosoma), which live in the intestinal or vesical (urinary bladder) venules and infect humans by direct penetration through the skin.

Trematodes

•Signs and symptoms are related largely to the location of the adult worms.

Trematodes

•multicellular eukaryotic helminths.

•Free-swimming larvae

•penetrate the skin of the human definitive host (schistosomes) or

• ingested

Clonorchis sinensis

•Chinese or oriental liver fluke

•following ingestion of imported, undercooked fish containing the parasite

Diagnosis

• Microscopic demonstration of eggs in the stool or in duodenal aspirate

• The adult fluke can also be recovered at surgery.

Fasciola hepatica

•the sheep liver fluke

•worldwide

Diagnosis

•Eggs can be recovered in the stools or in material obtained by duodenal or biliary drainage.

•False fascioliasis (pseudofascioliasis) refers to the presence of eggs in the stool resulting not from an actual infection but from recent ingestion of infected livers containing eggs.

•This situation (with its potential for misdiagnosis) can be avoided by having the patient follow a liver-free diet several days before a repeat stool examination.

•Antibody detection tests are useful especially in the early invasive stages, when the eggs are not yet apparent in the stools, or in ectopic fascioliasis.

Paragonimus westermani

• the oriental lung fluke

•The eggs are excreted unembryonated in the sputum, or alternately they are swallowed and passed with stool

• in the Far East

Diagnosis

• microscopic demonstration of eggs in stool or sputum,

(not present until 2 to 3 months after infection).

• Eggs are also occasionally encountered in effusion fluid or

biopsy material.

Schistosomiasis

•Schistosoma haematobium,

•S. japonicum,

•S. mansoni

•Eggs are eliminated with feces or urine

•Schistosoma mansoni: South America and the Caribbean, Africa, and the Middle East;

•S. Haematobium:n Africa and the Middle East; and

•S. Japonicum:Far East

Symptoms

•continuing infection may cause granulomatous reactions and fibrosis in the affected organs: •cystitis and ureteritis (S. haematobium) with hematuria, which can progress to bladder cancer !

Diagnosis

•Microscopic identification of typical eggs in stool or urine is the most practical method for diagnosis.

• stool examination -S. mansoni or S. japonicum

•urine examination - S. haematobium

•antibody detection

Schistosoma

mansoni

Schistosoma

haematobium