Infectious Diseases Ascariasis

Subject: Infectious Diseases Ascariasis Sun Jan 02, 2011 8:37 pm

Ascariasis
(as-kuh-RI-uh-sis) is a type of roundworm infection. Roundworms are
parasites that use your body as a host to stay alive and reproduce,
maturing from eggs to adult worms inside your body. While the worm eggs
are microscopic, adult worms can be more than a foot (30 centimeters)
long.

Ascariasis affects approximately 25 percent of the world's population.
Because most people have such mild cases of ascariasis, they have no
symptoms. But when your body is infested with hundreds of worms, serious
symptoms and complications can occur.

Ascariasis occurs most often in young children and is most prevalent in
tropical and subtropical regions of the world — especially in areas
where sanitation and hygiene are poor. In the United States, ascariasis
is most common in rural areas of the Southeast.

Symptoms

Most people infected with ascariasis have no symptoms. Moderate to heavy
infestations cause symptoms that may vary, depending on which part of
your body is being affected.

In the lungs
After you ingest the microscopic ascariasis eggs, they hatch in your
intestine and the larvae migrate through your bloodstream or lymphatic
system into your lungs. At this stage, you may experience signs and
symptoms similar to asthma or pneumonia, including:

* Persistent cough
* Shortness of breath
* Wheezing

After spending six to 10 days in the lungs, the larvae travel to your throat, where you cough them up and then swallow them.

In the intestines
The larvae mature in your small intestines and typically live there as
adults until they die. In mild or moderate ascariasis, the intestinal
infestation can cause:

* Vague abdominal pain
* Nausea and vomiting
* Diarrhea or bloody stools

If you have a heavy intestinal infestation — a large number of worms — you may experience:

* Severe abdominal pain
* Fatigue
* Vomiting
* Weight loss
* A worm in vomit or stool

When to see a doctor
Consult your doctor if you have persistent abdominal pain, diarrhea or nausea.

Causes

Ascariasis isn't spread directly from person to person. Instead, a
person has to come into contact with soil mixed with human feces that
contain ascaris eggs. In many developing countries, human feces are used
for fertilizer or poor sanitary facilities allow human waste to mix
with local soil in yards, ditches and fields.

Because small children often play in dirt, infection can occur if they
put their dirty fingers in their mouths. Unwashed fruits or vegetables
grown in contaminated soil also can transmit the microscopic eggs that
cause ascariasis.

Life cycle of a worm

* Ingestion. The microscopic ascariasis eggs cannot become infective
without coming into contact with soil. People can accidentally ingest
contaminated soil through hand-to-mouth contact, or by eating uncooked
fruits or vegetables that have been grown in contaminated soil.
* Migration. Larvae hatch from the eggs in your intestines and then
penetrate the intestinal wall to travel to your lungs via your
bloodstream or lymphatic system. After maturing for about a week in your
lungs, the larvae break into your airway and travel up your throat,
where they are coughed up and swallowed.
* Maturation. Once back in the intestines, the parasites grow into
male or female worms. Female worms can be more than 15 inches (40
centimeters) long and a little less than a quarter inch (6 millimeters)
in diameter. Male worms are generally smaller.
* Reproduction. Male and female worms mate in the small intestine.
Female worms can produce 200,000 eggs a day. You expel the eggs in your
feces. The fertilized eggs must be in soil for at least 18 days before
they become infective.

The whole process — from egg ingestion to egg deposits — takes about two
or three months. Ascariasis worms can live inside you for a year or
two. Because they cannot reproduce without leaving your body, heavy worm
infestations are caused by repeated ingestion of contaminated soil.

Risk factors

Risk factors for ascariasis include:

* Age. Most people who have ascariasis are 10 years old or younger.
Children in this age group may be at higher risk because they are more
likely to play in dirt.
* Warm climate. Ascariasis worms thrive in milder climates. In the
United States, ascariasis is more common in the Southeast. But it's more
prevalent in developing countries with warm temperatures year-round.
* Poor sanitation. Ascariasis is more widespread in developing
countries where human feces are allowed to mix with local soil.

Complications

Mild cases of ascariasis usually don't result in complications. If you
have a heavy infestation, potentially dangerous complications may
include:

* Nutritional deficiencies. Children with ascariasis are especially
at risk of nutritional deficiencies. Loss of appetite and insufficient
absorption of digested foods can occur.
* Intestinal blockage and perforation. In heavy ascariasis
infestation, a mass of worms can block a portion of the intestine,
causing severe abdominal cramping and vomiting. The blockage can even
perforate the intestinal wall or appendix, causing hemorrhage or
appendicitis.
* Duct blockages. In some cases, worms may block the narrow ducts of the liver or pancreas, causing severe pain.

Preparing for your appointment

Your family doctor might refer you to a doctor specializing in disorders
of the digestive system (gastroenterologist) if it appears that you
have a severe case of ascariasis. You may even need to consult a surgeon
if the worms have blocked your intestines.

What you can do
Before your appointment, you may want to write a list to answer the following questions:

* When did your symptoms begin?
* Does anything make your symptoms better or worse?
* Have you noticed any worms in your stool or vomit?
* Have you traveled to any developing countries lately?
* What types of medications and supplements are you taking?

What to expect from your doctor
During the physical exam, your doctor may press on certain areas of your
abdomen to check for pain or tenderness. He or she may also want a
sample of your stool for testing.

Tests and diagnosis

In heavy infestations, it's possible to find worms after you cough or
vomit, and the worms can come out of other body openings, such as your
mouth or nostrils. If this happens to you, take the worm to your doctor
so that he or she can identify it and prescribe the proper treatment.

Stool tests
About two months after you ingest ascariasis eggs, the worms mature and
begin laying thousands of eggs a day. These eggs travel through your
digestive system and eventually can be found in your stool. To diagnose
ascariasis, your doctor will examine your stool for the microscopic eggs
and larvae. But eggs will not appear in stool until at least 40 days
after you are infected. And if you are only infected with male worms,
you won't have any eggs at all.

Blood tests
Your blood can be tested for the presence of an increased number of a
certain type of white blood cell, called eosinophils. Ascariasis can
elevate your eosinophils, but so can several other types of health
problems.

Imaging tests

* X-rays. If you are infested with a large number of worms, the mass
of worms may be visible in an X-ray of your abdomen. In some cases, a
chest X-ray can reveal the larvae in your lungs.
* Ultrasound. An ultrasound may show if any worms are in your
pancreas or liver. This technology uses sound waves to create images of
internal organs.
* CT scans or MRIs. Both these types of tests create detailed images
of your internal structures, so they can detect worms that are blocking
ducts in your liver or pancreas. Computerized tomography (CT) combines
X-ray images taken from many different angles, while magnetic resonance
imaging (MRI) uses radio waves and a strong magnetic field.

Treatments and drugs

Mild cases of ascariasis may require no treatment. While symptomatic
infections usually warrant treatment, infections with no symptoms
typically don't need to be treated. In some cases, ascariasis will
resolve on its own. This occurs when there are no male worms to mate
with females and the females eventually die.

Medications
Anti-parasite medications are the first line of treatment against ascariasis. The most common are:

* Albendazole (Albenza)
* Ivermectin (Stromectol)
* Mebendazole

These medications work by killing the adult worms. Each medication can
be taken as a single dose. Side effects include mild abdominal pain or
diarrhea.

Surgery
In cases of heavy infestation, surgery may be necessary to repair damage
the worms have caused and to remove worms. Intestinal obstruction or
perforation, bile duct obstruction, and appendicitis are complications
that may require surgery.

Prevention

The best defense against ascariasis is good hygiene and common sense. Follow these tips to avoid infection:

* Practice good hygiene. Ascariasis is spread by ingesting parasite
eggs from contaminated soil. Before handling food, always wash your
hands with soap and water, and wash fresh fruits and vegetables
thoroughly.
* Use care when traveling. Ascariasis is the most common roundworm
infection in the world, with higher infection rates in developing and
warm-climate countries. When traveling, use only bottled water and avoid
raw vegetables unless you can peel and wash them yourself. As a rule,
eat only foods that are hot and cooked.

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