|Classification and external resources|
Signs and symptoms
When adult worms attach to the villi of the small intestine, they suck on the host's blood, which may cause abdominal pain, diarrhea, cramps, and weight loss that can lead to anorexia. Heavy infections can lead to the development of iron deficiency and hypochromic microcytic anemia. This form of anemia in children can give rise to physical and mental retardation. Infection caused by cutaneous larvae migrans, a skin disease in humans, is characterized by skin ruptures and severe itching.
The most common technique used to diagnose a hookworm infection is to take a stool sample, fix it in 10% formalin, concentrate it using the formalin-ethyl acetate sedimentation technique, and then create a wet mount of the sediment for viewing under a microscope. However, the eggs of A. duodenale and N. americanus cannot be distinguished; thus, the larvae must be examined to identify these hookworms. Larvae cannot be found in stool specimens unless the specimen was left at ambient temperature for a day or more.
An infection of N. americanus parasites can be treated by using benzimidazoles, albendazole, and mebendazole. A blood transfusion may be necessary in severe cases of anemia. Light infections are usually left untreated in areas where reinfection is common. Iron supplements and a diet high in protein will speed the recovery process. In a case study involving 56-60 men with Trichuris trichiura and/or N. americanus infections, both albendazole and mebendazole were 90% effective in curing T. trichiura. However, albendazole had a 95% cure rate for N. americanus, while mebendazole only had a 21% cure rate. This suggests albendazole is most effective for treating both T. trichiura and N. americanus.
Cryotherapy by application of liquid nitrogen to the skin has been used to kill cutaneous larvae migrans, but the procedure has a low cure rate and a high incidence of pain and severe skin damage, so it now is passed over in favor of suitable pharmaceuticals. Topical application of some pharmaceuticals has merit, but requires repeated, persistent applications and is less effective than some systemic treatments.
Necator americanus was first discovered in Brazil and then was found in Texas. Later, it was found to be indigenous in Africa, China, southwest Pacific islands, India, and Southeast Asia. This parasite is a tropical parasite and is the most common species in humans. Roughly 95% of hookworms found in the southern region of the United States are N. americanus. This parasite is found in humans, but can also be found in pigs and dogs.
Transmission of N. americanus infection requires the deposition of egg-containing feces on shady, well-drained soil and is favored by warm, humid (tropical) conditions. Therefore, infections worldwide are usually reported in places where direct contact with contaminated soil occurs.
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- "Necator americanus Material Safety Data Sheets (MSDS)". 2001. Public Health Agency of Canada. 4 Dec 2009. http://www.phac-aspc.gc.ca/msds-ftss/msds107e-eng.php
- "hookworm disease." Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 06 Dec. 2009 <http://www.britannica.com/EBchecked/topic/271350/hookworm-disease>.
- Holzer, B. R.; and Frey, F. J. (February 1987). "Differential efficacy of mebendazole and albendazole against Necator americanus but not for Trichuris trichiura infestations". European Journal of Clinical Pharmacology. 32 (6): 635-637. http://www.springerlink.com/content/k000065915k70257/
- Caumes, Eric. Treatment of Cutaneous Larva Migrans. Clin Infect Dis. (2000) 30 (5): 811-814. doi: 10.1086/313787