Hookworm
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The hookworm is a parasite that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. The distribution of each species significantly overlaps that of the other. Necator americanus predominates in The Americas and Australia, while only A. duodenale is found in the Middle East, North Africa and southern Europe. Hookworms are thought to infect 800 million people worldwide. The A. braziliense and A. tubaeforme species infect cats, while A. caninum infects dogs. Uncinaria stenocephala infects both dogs and cats.
These worms are much smaller than the large roundworm, Ascaris lumbricoides, and the complications of tissue migration and mechanical obstruction so frequently observed with roundworm infestation are less frequent in hookworm infestation. The most significant risk of hookworm infection is anemia secondary to loss of iron (and protein) into the gut.
Ankylostomiasis, or anchylostomiasis, also called helminthiasis, "miners' anaemia", and in Germany Wurmkrankheit, a disease to which much attention has been paid, from its prevalence in the mining industry in England, France, Germany, Belgium, North Queensland and elsewhere, apparently known in Egypt even in very ancient times, caused a great mortality among blacks in the West Indies towards the end of the 18th century; and through descriptions sent from Brazil and various other tropical and sub-tropical regions, it was subsequently identified, chiefly through the labours of Bilharz and Griesinger in Egypt (1854), as being due to the presence in the intestine of nematoid worms (Ankylostoma duodenalis) from one-third to half an inch long. The symptoms, as first observed among blacks, were pain in the stomach, capricious appetite, pica (or dirt-eating), obstinate constipation followed by diarrhoea, palpitations, small and unsteady pulse, coldness of the skin, pallor of the skin and mucous membranes, diminution of the secretions, loss of strength and, in cases running a fatal course, dysentery, haemorrhages and dropsies. The disease was first known in Europe among the Italian workmen employed on the St Gotthard tunnel. In 1896, though previously unreported in Germany, 107 cases were registered there, and the number rose to 295 in 1900, and 1030 in 1901. In England an outbreak at the Dolcoath mine, Cornwall, in 1902, led to an investigation for the home office by Dr Haldane F.R.S. (see especially the Parliamentary Paper, numbered Cd. 1843), and since then discussions and inquiries were frequent.
A committee of the British Association in 1904 issued a valuable report on the subject. After the Spanish-American War American physicians had also given it their attention, with valuable results; see Stiles (Hygienic Laboratory Bulletin, No. 10, Washington, 1903), who first described Necator americanus under the name Uncinaria americana, whence the name Uncinariasis for this disease.
Hookworms are leading causes of maternal and child morbidity in the developing countries of the tropics and subtropics. In susceptible children hookworms cause intellectual, cognitive and growth retardation; as well as intrauterine growth retardation, prematurity and low birth weight among newborns born to infected mothers. Hookworm infection is rarely fatal, but anemia can be significant in the heavily infected individual.
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Hookworm life cycle
See the image for the biological life cycle of the hookworm.
The hookworm larva lives in infected soil. The larva penetrates the skin on contact, e.g. when walking barefoot, enters the bloodstream and is transported to the lungs. From the lungs and bronchi it transfers to the stomach and intestine by coughing up and swallowing phlegm. The larva clings to the intestinal mucous membrane and developes into an adult hookworm, drawing its nourishment from the blood-vessels of their host, and as the parasites are found in hundreds in the body after death, the disorders of digestion, the increasing anaemia and the consequent dropsies and other cachectic symptoms are easily explained. The adult releases eggs that leave the human body with the feces. The eggs hatch in soil and eventually develop into larva.
The parasites thrive in an environment of dirt, particularly sandy soil, and the main lines of precaution are those dictated by sanitary science.
To prevent hookworm infection:
- prevent skin/soil contact: do not walk barefoot
- do not defecate outside latrines, toilets etc.
- do not use human excrement or raw sewage as manure/fertilizer in agriculture
- Worm pet dogs (canine hookworms cannot develop to adulthood in humans, but can cause an unpleasant rash called cutaneous larval migrans).
If you are traveling and develop what you at first think are mosquito bites on the soles of your feet, be aware that it might be hookworm. If on the second day you see the "bites" turn into lines, it is probably hookworm and you should see your doctor immediately. Hookworm is commonly called "larva migratoria" in Spanish and "bicho do pé" in Portuguese. This might come in handy if you have to see a doctor in another country.
Treatment
Hookworm can easily be treated with a topical liquid when it has first been contacted, and is still in the skin. Usually the same liquid is taken orally as well. As of 1911, malefern, santonine, thymol and other anthelmintic remedies were prescribed.
See also
References
- This article incorporates text from the 1911 Encyclopædia Britannica, which is in the public domain.
External link
- CDC Department of Parasitic Diseases images of the hookworm life cycle
- Personal MD, more hookworm info
