There are three standard methods of fecal examination for ova and parasites: direct examination, concentration methods followed by direct examination, and permanent stained slides prepared after concentration. Concentration techniques are useful on all types of stool specimens but especially on formed stools or soft stools. Concentration techniques detect larvae, ova, and protozoan cysts. Direct wet mounts can also be performed on all types of stools and also can detect larvae, ova, and protozoan cysts, but will not detect them as frequently as concentration techniques (in one study, only half as often). However, direct wet mount occasionally will detect some ova and protozoan cysts missed by concentration techniques. Permanent stained slide preparations are designed to detect protozoan cysts and trophozoites rather than ova or larvae, and should be performed on all very soft or liquid stools. Stained slides in addition to concentration plus direct examination are essential for optimal detection of E. histolytica and G. lamblia. In several reports, concentration techniques yielded about 50%-60% positive results for these two protozoans (literature range, 45%-74%), whereas stained smears yielded about 75%-85% positive results (literature range, 59%-95%). In another study, nonfixed direct wet mounts detected only 5% of trophozoites, whereas permanent stain detected about 60%.
Tag: Parasites
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Eosinophilia
Parasites. Eosinophilia is most often associated with roundworms and infestation by various flukes. In the United States, roundworms predominate, such as Ascaris, Strongyloides, and Trichinella (Trichina). The condition known as visceral larva migrans, caused by the nematode Toxocara canis (common in dogs) is sometimes seen in humans. In Trichinella infection an almost diagnostic triad is bilateral upper eyelid edema, severe muscle pain, and eosinophilia. (Eosinophilia, however, may be absent in overwhelming infection.)
Acute allergic attacks. Asthma, hay fever, and other allergic reactions may be associated with eosinophilia.
Certain extensive chronic skin diseases. Eosinophilia is often found in pemphigus; it also may appear in psoriasis and several other cutaneous disorders.
Certain bacterial infections. Eosinophilia may occur in scarlet fever and brucellosis.
Miscellaneous conditions. Eosinophilia is reported in 20% of polyarteritis nodosa cases and 25% of sarcoidosis patients. It also has been reported in up to 20% of patients with Hodgkin’s disease, but the degree of eosinophilia is usually not impressive. Eosinophilia is associated with certain types of pneumonitis such as Lцffler’s syndrome and the syndrome of “pulmonary infiltration with eosinophilia.” Eosinophilia may occur with various types of cancer, but the overall incidence is less than 1%. A substantial number of patients undergoing peritoneal dialysis for chronic renal failure are reported to have intermittent eosinophilia (about 60% of cases in one report), most often following insertion of the dialysis catheter. A number of other diseases have been reported to produce eosinophilia, but either the diseases are rare or there is a low incidence of eosinophilia.