Hookworm - Ancylostoma Duodenale and Necator Americanus

The hookworm, also called hookworm, necatoriasis, yellowing or Jeca Tatu disease is a very common intestinal parasitosis caused by two Nematodes: Ancylostoma duodenale or Necator americanus.

Ancylostoma worms
Ancylostoma worms

What is hookworm

The hookworm in men is a worm infestation caused by nematodes of Ancylostomidae family: Ancylostoma duodenale or Necator americanus . Other species of hookworms, as braziliense Ancylostoma or Ancylostoma caninum, usually only cause intestinal infection in cats and dogs, but can cause larva migrans in man.

It is estimated that about 740 million people worldwide are infected with hookworms of the two. The Ancylostoma duodenale is a species of hookworm that inhabits Mediterranean, North Africa, Iran, India, Pakistan, China and Japan. But the Necator americanus is very found throughout the American continent, especially in tropical areas, Central Africa, Southeast Asia South Pacific islands and parts of Australia.

The Ancylostoma duodenale and Necator americanus are small roundworms, which are between 0.5 and 1.5 cm in diameter and have a head shaped like a hook, especially N. americanus. Both have a well - defined mouth with two pairs of sharp teeth (A. duodenale) or two sharp plates (N. americanus), which serve to adhere to the intestinal wall and suck the blood of its host.

Life cycle of Ancylostoma duodenale and Necator americanus

Individuals with hookworm daily eliminate thousands of parasite eggs in their feces. In places with poor sanitation, these stools end up contaminating the soil. If hookworm eggs are deposited them in a humid, hot and no direct exposure to sunlight, they can give rise to larvae that after about 7 days in the environment, mature and become capable of infecting humans. The larvae of hookworms can survive in the environment, waiting for a host, for up to 6 weeks if have suitable conditions of humidity and temperature.

Contamination with Ancylostoma duodenale or Necator americanus is through direct skin contact with contaminated soil (usually the legs) or by accidental ingestion of this larva on the environment (often by hands contaminated by soil going to mouth without being washed). Just 5 minutes of direct skin contact with contaminated soil is sufficient for the larva to penetrate our body.

After penetrating the skin, the larvae reach the blood vessels and travel to the lungs, where it will remain for some days. When the patient coughs, the parasite can be released toward the oral cavity, and then inadvertently swallowed. If the contamination has not been by the skin, but by accidental ingestion of larvae, that first part of the cycle does not exist, going the parasite directly to the gastrointestinal tract.

When swallowed, the larvae pass through the stomach and lodges in the small intestine, where it will mature into adult worm form. There each intake hookworm adheres to the mucosa and starts to consume about 0.3 to 0.5 ml of blood per day. To arising anemia, contamination is required with at least 40 worms.

Five to eight weeks after the patient has been infected for the first time, the female Ancylostoma duodenale or Necator americanus starts to produce thousands of eggs, which will be released to the environment through feces, restarting the parasite's life cycle.

Both Ancylostoma duodenale or Necator americanus do not multiply within our body. To generate new worms, the eggs must be deposited in the environment. So if the individual does not recontaminate, he ends up healing of hookworm alone with time. The problem is that the Ancylostoma duodenale usually have a 1 year lifetime and Necator americanus can reach up to 5 years. If the patient lives in an area with poor sanitation, he ends up infecting again before the first generation of worms have died.

Symptoms of hookworm

The hookworm is a parasitic disease with clinical predominantly gastrointestinal. Before the worm Chagar the intestine, the symptoms are mild. In the worm penetrate the skin site is formed a little inflammatory reaction, which causes itching. During the passage through the lungs, the patient usually has dry cough.

Typical symptoms of hookworm arise even when the parasite migrates into the small intestine. At this time, the patient may experience nausea, vomiting, diarrhea, tiredness, increased gas and abdominal pain. The initial infection is usually the most symptomatic. As the individual reinfects repeatedly, the trend is it present fewer symptoms.

The main problem of hookworm is anemia and malnutrition, because the parasite consumes blood and protein. In children, there may be slowing growth and changes in neurological development. In pregnant women, malnutrition and anemia are more common, and the baby is usually born with low weight.

Diagnosis of hookworm

The diagnosis of hookworm is done by the detection of parasite eggs in the faeces. The problem is that after the invasion of the skin by the parasite, the first eggs can only appear two months later. When the infection is caused by A. duodenale, the first eggs can take up to 1 year to appear in the stool. Therefore, when there is clinical suspicion of hookworm, several stool tests may be needed until an egg can be identified.

In the CBC, the presence of anemia and eosinophilia (increase in eosinophils), associated with a suspected gastrointestinal framework is an important clue to the diagnosis.

Treatment of hookworm

The treatment is equal to hookworm, whether caused by Ancylostoma duodenale or Necator americanus.

Two scheme with anthelmintics are the most used:
  • Albendazole 400 mg single dose
  • Mebendazole 100 mg 2 times a day for 3 days.

If the patient has anemia also indicates whether iron replacement orally.

A stool test can be requested after 3 weeks to confirm the cure.
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