Page 157 - Medical Parasitology_ A Textbook ( PDFDrive )

150 12 Trematodes: Flukes

Cercariae invade the crustacean
5
and encyst into metacercariae. i
4a 4b 4c

Sporocysts Rediae Cercariae

Humans ingest
inadequately 6
cooked or pickled
4 crustaceans containing
metacercariae.
7

Excyst in
duodenum
3
Miracidia hatch,
and penetrate snail 8

Adults in cystic
cavities in lungs
lay eggs which
are excreted
in sputum.
2 Embryonated eggs Alternately eggs
d are swallowed
i = Infective Stage 1 Unembryonated eggs and passed with
d = Diagnostic Stage stool.
Fig. 12.11 Life cycle of Paragonimus westermani (Reproduced from https://www.cdc.gov/dpdx/
paragonimiasis/index.html)

Diagnosis
1. Microscopic examination
Detection of the eggs in sputum or faeces (if the patient swallows the eggs).
2. Serodiagnosis
3. Molecular diagnosis
PCR on clinical specimens.
4. Biopsy
Identification of species is made when adult or egg is recovered from the
lesion in the lungs.

Treatment
Praziquantel (25 mg/kg orally 3 times per day for 2 days) is the drug of choice.
Bithinol and niclofolan are also effective.

Prevention and Control
1. Adequate cooking of crabs and crayfish
2. Treatment of infected cases
3. Control of snails