Page 212 - parasitology for medical and clinical laboratoryprofessionals

192 CHAPTER 8

poorly cooked crabs and crayfish and become infected,
upon which the infective larvae from the crabs or crayfish MICROSCOPIC DIAGNOSTIC
migrate from the duodenum to organs that include the FEATURE
intestinal wall, lymph system, genitourinary tract, central
nervous system, and subcutaneous tissues of the body.
Sometimes the respiratory system is affected and when General Classification—Paragonimus
the lungs become involved the victim develops a cough westermani ova
with hemoptysis. Flecks of blood in the sputum are often Organism Paragonimus
the first sign of paragonimiasis. westermani
Specimen Required Sputum specimens
Disease Transmission most commonly,
less often in stool
Infection occurs when encysted metacercariae are specimens
eaten, along with raw or undercooked crustaceans such Stage Eggs when coughed
as crabs and crayfish. The disease may progress to the up and swallowed
lungs where pulmonary and extra-pulmonary infections Size Range from 80–118 3
become established. 48–60 μm (average
100 3 50 μm)
Laboratory Diagnosis Shape Eggs are broadly oval
Shell Shell of egg is thin
Laboratory diagnosis is frequently based on the finding of but thickens
eggs in either feces or sputum. The eggs measure roughly toward the flattened
100 by 50 μm, and are unembryonated when passed operculum (lid)
(Figure 8-6). Flecks of blood may appear in the sputum Other Features Must be differ-
during infections with P. westermani whose eggs are easily entiated from
Diphyllobothrium
latum
Wet mount from
sputum may reveal
eggs in some patients
P. westermanni
Ovum

Source: Centers for Disease Control and Prevention (CDC) confused with the eggs of the tapeworm Diphyllobothrium Delmar/Cengage Learning

latum, as both are operculated and are essentially the

is brownish in color. Serological immunoassays for serum
antibodies against the organism are available and pleural
effusions are also used to detect the presence of the organ-
FIGURE 8-6 Unstained, formalin-preserved stool same size. When seen, the adult worm is 10 by 8 mm and
specimen egg of Paragonimus westermani trematode ism in both pulmonary and extra-pulmonary infections.