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Intestinal Nematodes 147

Source: Centers for Disease Control and Prevention (CDC) Source: Centers for Disease Control and Prevention (CDC)

FIGURE 6-6 Buccal (mouth) cavity morphology of a FIGURE 6-8 A hookworm infection involving the toes
hookworm, during its rhabditiform, early noninfectious of the right foot
larval stage

and a progressive iron and protein-deficiency anemia.
Often the first sign of having contracted a hookworm
infection is that of the inflammation where the larvae
penetrated the skin of the host (Figure 6-8), signs that
Source: Centers for Disease Control and Prevention (CDC) symptoms will occur.
may last for a week or more. However, as the health of the
individual deteriorates, the more noticeable signs and

Upon penetrating the human skin, animal
hookworm larvae may produce a slowly spreading
skin eruption called cutaneous larval migrans.
These nematodal larvae migrate through circuitous
paths between the top two layers of the skin (stratum

lesions called vesicles that contain serous fluids. With
the advancing movement of the larvae over the body,
the initial areas of the lesions appear dry and crusty.
FIGURE 6-7 Results of dietary protein deficiency germinativum and stratum corneum), resulting in
including edema Often the first sign of infection is the associated itching
followed by a rash at the site where skin was penetrated
nausea, vomiting, indigestion, constipation, and diarrhea and became contaminated by soil or loamy sand.
can occur either in the earlier or in the later stages as well Penetration of the skin by these larvae may ultimately
although gastrointestinal symptoms tend to grow less se- lead to anemia, abdominal pain, loss of appetite,
vere over a period of time. Advanced and severe infec- diarrhea, and weight loss.
tions that are not treated often progress to severe anemia
and protein deficiency states. Characteristics of those Life Cycle
suffering from chronic hookworm disease often include
emaciation and wasting, cardiac failure or abdominal The generalized biological life cycle of the hookworm
distension with ascites, a term indicating a fluid-filled requires environmental conditions conducive to its sur-
cavity (Figure 6-7). vival, and is able to proceed when the temperature of the
No specific symptoms or signs of hookworm infec- earth reaches temperatures of over 65°F or 18°C. The
tion and sometimes no symptoms at all are present until larvae exist primarily in sandy or loamy soil and can-
the health of the infected individual occurs. Clinical signs not survive in clay or boggy wet soil as this type of soil
may occur from a combination of intestinal inflammation condition is not favorable for survival of the microfilaria