For Hookworm Diagnosis, Is Finding an Egg Enough?

Abstract

What do we find when diagnostically we discover a hookworm egg? A case of hookworm? Perhaps. But do we not still regard such a finding too simply? Does the demonstration of a hookworm egg in a diagnostic preparation furnish information comparable in significance, for instance, to finding a few acid-fast bacilli in a sputum smear?In the latter instance we are dealing with an organism that is self-multiplying within the host, and finding only one or a few acid-fast forms may be a crucial diagnostic point. For hookworm we need rather to remember that the organism is not self-multiplying, and finding an egg may have little or no significance. What does have significance is how many eggs are demonstrable, as a measure of the amount of infestation in the individual concerned (Cort, 1924). Also we should know, if possible, whether we are dealing with Necator americunus (Stiles, 1902), with Ancylostoma duodenale (Dubini, 1843), or with both.Why is it necessary to know something about the size of the infestation? Individuals examined for the presence of hookworm may be thought of in two distinct categories. They are either (1) members of a population group living under conditions of reinfection or (2) individuals separated for the time being from further infection, such as patients in a hospital or those no longer in endemic areas.For members of Category 1 who reside in endemic areas, examining stools by any refined method to determine whether or not they show an egg in the feces may be useful to satisfy curiosity, but scientifically it is useful primarily as a screening method by which to select the specimens to be egg-counted, i.e., to learn something of how heavy an infestation they are exhibiting. The epidemiology of endemic infections requires information not so much to determine how many individuals over-all are showing infestation as to learn how many are heavily infested, how many are moderately infested, and how many are lightly infested. Our concern is with a succession of incidences of the different weights or burdens of infestation. The proportion of the numbers of individuals in such subgroups, classified for sex, age, occupation, and the like, will show where in the population attention to control should be centered. A mere over-all incidence figure, or even an average worm burden, may be spurious and misleading unless one also knows the distribution of the worm burdens within the group.For members of Category 2, such as hospitalized patients, or Puerto Ricans living in New York, knowledge of the mere presence or absence of an egg in the feces should be secondary to knowing something of how many there are, in order to relate the parasitic status to the clinical condition, including anemia if demonstrable, and to guide the treatment and its effects. The ultimate in the determination of such parasitic status for one person requires the egg-count sampling of a succession of entire fecal outputs. However, a serviceable short 712