[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

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CHAPTER 8 The Nematodes
Although historically a parasite of the Old
World, A. duodenale has been transported to
other areas of the globe via modern world
travel. Today, A. duodenale may be found in
Europe, China, Africa, South America, and the
Caribbean.
Clinical Symptoms
Asymptomatic Hookworm Infection. Some
persons infected with a light hookworm burden
do not exhibit clinical symptoms. An adequate
diet rich in iron, protein, and other vitamins
helps maintain this asymptomatic state.
Hookworm Disease: Ancylostomiasis, Necatoriasis.
Patients who are repeatedly infected may
develop intense allergic itching at the site of
hookworm penetration, a condition known as
ground itch. A number of symptoms experienced
by infected persons are associated with larvae
migration into the lungs, including sore throat,
bloody sputum, wheezing, headache, and mild
pneumonia with cough.
The symptoms associated with the intestinal
phase of hookworm disease depend on the
number of worms present. Chronic infections,
consisting of a light worm burden (defined as
<500 eggs/g of feces) are the most common form
seen. These patients may experience vague mild
gastrointestinal symptoms, slight anemia, and
weight loss or weakness.
Patients with acute infections (>5000 eggs/g of
feces) may develop a number of symptoms,
including diarrhea, anorexia, edema, pain, enteritis,
and epigastric discomfort. Furthermore
because adult hookworms compete with the
human host for nutrients as they feed, infected
patients may develop a microcytic hypochromic
iron deficiency, weakness, and hypoproteinemia.
Mortality may result from the enormous loss of
blood.
Treatment
The drugs of choice for treatment of hookworm
disease are mebendazole and pyrantel pamoate.
When indicated, especially in persons with
asymptomatic hookworm infection, only iron
replacement and/or other dietary therapy (including
proteins, iron, and other vitamins) may be
administered.
Prevention and Control
Hookworm prevention and control measures are
similar to those for A. lumbricoides. Proper sanitation
practices, especially appropriate fecal disposal,
prompt and thorough treatment of infected
persons, and personal protection of persons
entering known endemic areas, such as covering
bare feet, are measures targeted at breaking the
hookworm life cycle.
Notes of Interest and New Trends
The advent of indoor plumbing is said by some
to have contributed to a considerable decrease
in hookworm infections, and considered by
others to have eradicated them, in areas of the
United States known to have sandy soil. Infections
in those regions were contracted by individuals
who walked barefoot to and from the
outhouse.
The incidence of hookworm among soldiers
during World War II was high. A significant
number of them exhibited no clinical symptoms.
Their diagnosis was based solely on the presence
of hookworm eggs in the stool. These soldiers
were unnecessarily hospitalized and given potent
medications that resulted in toxic side effects. In
those asymptomatic cases, only simple dietary
therapy would have been warranted.
Research has been conducted using a reverse
enzyme immunoassay for specific immunoglobulin
E (IgE) in patients with known hookworm
infections. This serodiagnosis methodology has
shown favorable results and has been suggested
as an alternative means of hookworm infection
diagnosis.
There are two other species of hookworms
known to infect humans accidentally, although
they are primarily a parasite of dogs and cats,
Ancylostoma braziliense, and of dogs only, Ancylostoma
caninum. When they infect humans,