Clinical Diagnosis.—The diseases with which it is most likely to be confused are beriberi, chronic nephritis and malarial cachexia. Stiles notes that heavy Ascaris infections may give rather similar symptoms.
The signs of a multiple neuritis should differentiate beriberi, and the presence of casts or high blood pressure, chronic nephritis. Recently, there has been a great deal written about the danger of confusing hookworm disease and malarial cachexia, the statement being often made that splenic enlargement is a feature of ancylostomiasis. Most authorities, however, state that the spleen of ancylostomiasis is not enlarged, this point being of diagnostic value in differentiating it from malaria and kala-azar.
Laboratory Diagnosis.—As a matter of fact the diagnosis is almost invariably made by finding hookworm ova in the faeces. The eggs are oval and thin-shelled with a wide, clear, glassy zone separating the more or less segmented, granular central portion from the shell.
Formed stools are more satisfactory for examination than the liquid ones resulting from a dose of salts. Put about 2 drops of water or 1% trikresol solution in the centre of a glass slide and emulsify in it as much of the faeces as is held by the spatulate end of a wooden toothpick. A small piece of wood or a match stick will answer. These preparations can be readily examined without a cover-glass, using a ⅔ inch objective, with a 1-inch ocular.
Cultural methods give a higher percentage of success than looking for ova in the stools. Put a pile of 2 inch filter papers in the center of a Petri dish. Fill the dish with water to the level of the paper island. Smear a thick layer of faeces on the paper. The larvae hatch out and can be found by centrifuging the water.
It is usually stated that about 500 worms must be present for several months to produce symptoms. Grassi has thought that the presence of 150 eggs in 0.01 gm. faeces indicates the presence of 1,000 worms, of which 25% would be males.
There may be as many as 4,000,000 eggs in a stool. Bass has proposed the following method for the examination of faeces for ova: The faeces, which have been made fluid, should be centrifuged and the supernatant fluid containing vegetable débris poured off. The sediment contains hookworm eggs. Then pour on sediment a calcium chloride solution of sp. gr. 1.050. Again centrifuge and decant. Next add calcium chloride solution of a sp. gr. of 1.250 and centrifuge. This brings to the surface the hookworm eggs which may be pipetted off. As a rule, the finding of hookworm eggs is very easy without such a technique.
Fig. 93.—Ovum of Ancylostoma duodenale. By J. A. Thomson. (Jefferys and Maxwell.)