Page 144 - parasitology for medical and clinical laboratoryprofessionals

124 CHAPTER 5

remedy the widespread scourge of hookworm infections is that hookworm infection tends to be occupational,
included the West Indies, where significant mortality so that plantation workers, coal miners, and other
rates were reported just before the end of the eighteenth groups maintain a high prevalence of infection among
century. The disease was also well established, as in- themselves by contaminating their own personal
dicated by reports from Brazil and a number of other work environment. However, in most endemic areas,
tropical and subtropical regions. Not only controlling adult women are the most severely affected by the
the factors leading to contracting the disease and the accompanying anemia, mainly because they have
spread of it, but treatment of existing infections was re- much higher physiological needs for iron with regular
quired to minimize the threat to new victims. Treatment menstrual cycles, repeated pregnancies, and also
from the turn of the century was with thymol, a mercury because they customarily have less access to adequate
containing medication to kill the worms was used, fol- food than do men.
lowed by ingestion of Epsom salts to clear the body of
the worms. Then, sometime later, a medication called Life Cycle for Hookworms
tetrachloroethylene became available and replaced the
thymol treatment as the preferred method for killing the This image for the biological life cycle of the hookworms
organisms. In the mid-twentieth century new organic is in areas where the organism thrives in warm earth with
drug compounds that were even more effective and less surrounding temperatures of over 18°C. Acid soil such
toxic were developed and introduced for treatment of as red clay or in muck found in much of the southern
hookworm infections. United States is not conducive to the survival of hook-
Many individuals with hookworm infection have worm larvae. Hookworm larvae exist for the most part
no symptoms. Generally, very high loads of the parasite in sandy or loam soils. A rainfall average of more than
coupled with poor nutrition with inadequate intake of 40 inches per year is almost mandatory for the reproduc-
protein and iron will eventually lead to anemia. But many tion of hookworms where a stage of the life cycle includes
infected individuals are able to tolerate the condition larvae that remain in the soil for a period of time. These
for years while needlessly passing on the infection and environmental conditions are certainly met in many areas
showing no ill effects of the infection themselves. The of the United States, especially the southeastern part of
symptoms can be linked to inflammation in the gut the North American continent and in other parts of the
stimulated by feeding hookworms which is accompanied world. Eggs will not hatch if these conditions are not
by nausea, abdominal pain, and intermittent diarrhea minimally met.
early in the disease, with progressive anemia occurring There is also a difference in survival of the two ma-
in prolonged disease. Old folk remedies were often jor species of the hookworm. Infective larvae of N. ameri-
followed, particularly in the southeastern United canus can survive at higher temperatures than those of
States. Impulsive eating of certain materials, perhaps A. duodenale. This perhaps accounts for the fact that
accompanied by unreasonable desires for certain N. americanus is primarily found in the temperate zones
materials, such as pica (or dirt-eating) are present in of the southeastern United States and nearby regions,
some. Others exhibit prolonged constipation followed whereas A. duodenale is confined to Europe where the
by diarrhea, heart palpitations from severe anemia, climate is cooler. As a general rule, these larvae live for
thready (weak) pulse, coldness of the skin, pallor of only a few weeks in natural conditions suitable for their
the mucous membranes, fatigue and weakness, and survival, and will die within a short time if exposed to
shortness of breath often occur in long-standing direct sunlight, or if the conditions are too dry for the
cases. Extremely grave medical conditions, including infective stage of the larvae. So as the United States and
dysentery, hemorrhage, and edema, may culminate in in particular the rural South moved from an agrarian so-
eventual death. ciety where almost everyone initially lived in close prox-
In contrast to most intestinal helminthiases, where imity to the soil and often raised animals, the incidence
the heaviest parasitic loads tend to occur in children, of these infestations have been greatly diminished. Di-
hookworm prevalence and intensity can be even agnosis may be made by finding ova in the stool speci-
higher among adult males. The explanation for this men of a victim, but A. duodenale and N. americanus are