Introduction - Ascaris Lumbricoides

Ascaris lumbricoides is a parasite. It is a helminth or more specifically a nematode (roundworm) that undergoes most of its life-cycle within the human body.

Ascariasis is a type of roundworm infection that causes many problems in human beings. This type of round worm tends to inhabit the intestines of human beings, named Ascaris lumbricoides. In other words, human beings are host to them. They stay in our bodies, mature and reproduce eggs to complete their life cycle

 So what is meant by parasitism? It is actually a symbiotic relationship between usually 2 organisms that are of different species where one will gain benefit while the other suffers. Ascaris benefits from the intestinal contents from human being while the host , human beings are being sacrificed of their nutrients and body fluids.

The lifecycle of Ascaris Lumbricoides begins when a human ingests viable Ascaris eggs via contaminated soils or composts that may remain on unwashed hands, food, or particularized dust.

When the eggs entered the human body, they enter the intestines and mature over a period of two months to become young adults.

The adult Ascaris roundworm will remain in the small intestines where it can live for up to one year.

In addition, the roundworm can migrate to the heart and lungs.

During most of the adult life the female Ascaris roundworm lays eggs that are excreted in the feces of the infected human.

Once the eggs are excreted from the human body they often remain viable for a period of several years waiting to infect another human and repeat the life cycle. Feces from a human infected with Ascaris often contain 10,000 viable eggs per one gram of feces, while the female A. lumbricoides roundworm can excrete over 200,000 eggs daily.

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Epidemiology of Ascaris Lumbricoides

WHO estimated that more than 1.4 billion people are infected with Ascaris lumbricoides, representing about 25 percent of the world population.

In Malaysia, it is estimated that up to 90 percent are infected in rural areas (especially among Orang Asli) whereas only 4 percent in are reported urban areas.

A number of features account for its high prevalence including:
1)a ubiquitous distribution the durability of eggs under a variety of environmental conditions
2)the high number of eggs produced per parasite
3)poor socioeconomic conditions that facilitate its spread.
Transmission is enhanced by the fact that individuals can be asymptomatically infected and can continue to shed eggs for years, yet prior infection does not confer protective immunity.

Although ascariasis occurs at all ages, it is most common in children 2 to 10 years old, and prevalence decreases over the age of 15 years. Infections tend to cluster in families, and worm burden correlates with the number of people living in a home. Infection rates for ascariasis have not been reported to be higher in patients infected with the human immunodeficiency virus (HIV).

The highest prevalence of ascariasis occurs in tropical countries where warm, wet climates provide environmental conditions that favor year-round transmission of infection. This contrasts to the situation in dry areas where transmission is seasonal, occurring predominantly during the rainy months.
The prevalence is also greatest in areas where suboptimal sanitation practices lead to increased contamination of soil and water. The majority of people with ascariasis live in Asia (73 percent), Africa (12 percent) and South America (8 percent), where some populations have infection rates as high as 95 percent.

The rate of complications secondary to ascariasis ranges from 11-67%, with intestinal and biliary tract obstruction representing the most common serious sequelae. Although infection with A lumbricoides is rarely fatal, it is responsible for an estimated 8,000-100,000 deaths annually, mainly in children, usually from bowel obstruction or perforation in cases of high parasite burden

Ova can survive in the environment for prolonged periods and prefer warm, shady, moist conditions under which they can survive for up to 10 years. The eggs are resistant to usual methods of chemical water purification but are removed by filtration or by boiling. Developing larvae will be destroyed by sunlight and desiccation. There is no significant animal reservoir, but A. suum, which infects pigs, is morphologically similar to A. lumbricoides, and the larval forms can occasionally infect humans.

Transmission - How the parasites were spread?
Transmission occurs mainly via:
1)ingestion of water or food (raw vegetables or fruit in particular) contaminated with Ascaris lumbricoides eggs
2)inhalation of contaminated dust
3)Children playing in contaminated soil may acquire the parasite from their hands
4)Transplacental migration of larvae has also occasionally been reported
5)Co-infection with other parasitic diseases occurs with some regularity because of similar predisposing factors for transmission

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Clinical presentation of Ascariasis

Many individuals infected with Ascaris lumbricoides remain generally asymptomatic.

But on the other hand, if the infection is severe, the individual can become symptomatic.
Ascariasis has a multitude of symptoms, which include:

Coughing
dyspnea
substernal pain
conjunctivitis, convulsions
eosinophilia
fever
skin rash
abdominal distension
abdominal pain
colic
nausea
vomiting
anal itching
anorexia
disordered small bowel pattern
malabsorption
enterocolitis
fat malabsorptio
intermittent diarrhoea
jejunal mucosal abnormalities
protein malabsorption
restlessness
vitamin A malabsorption
intestinal obstruction
intussusception
invasion of bile duct (producing cholangitis, obstructive jaundice, gallstones, or liver abscesses)
acute appendicitis
acute pancreatitis
intestinal perforation, peritonitis
upper respiratory tract obstruction
volvulvus 



Most of the symptoms occurred due to the obstruction and migration of the adult worm to elsewhere of the body other than the intestines.  Although these symptoms exist, Ascariasis can often go misdiagnosed as most of the symptoms can also be contributed to other common illnesses.

More than often, the diagnosis of Ascariasis comes about after the excretion of adult Ascaris worms via the anus, mouth, or nose.

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Pathogenesis - How does Ascaris Lumbricoides causes illness?

Ascariasis is infection caused by Ascaris lumbricoides, an intestinal roundworm. 

First, the eggs of the worm are found in soil contaminated by human stool or in uncooked food contaminated

by soil containing eggs of the worm. 

Second, person can get infected when he/she swallows contaminated food with Ascaris eggs. It usually occurs in poor sanitation area.  

Third, once swallowed, Ascaris eggs hatch and release larvae in the intestine. 

Then, each larva migrates through the wall of the small intestine and is carried through the lymphatic vessels and bloodstream to the lungs. 

Fifth, in the lungs, the larva passes into the air sacs. It then moves up to the respiratory tract and into the throat and is swallowed.

Finally, the larva matures in the small intestine, where it remains as an adult worm. This is the stage where variety of symptoms could occurs if the worm burden is heavy. They might be huge enough to form a bolus and obstruct the intestine lumen or they might migrate to other places of the body due to some stimulation.

Female adult Ascaris Lumbricoides produce eggs. Eggs laid by the adult worms are excreted in stool and cause infection again when they are ingested by another person.

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Effacts & Complications of Ascariasis

As mentioned earlier, Ascariasis could remain asymptomatic but could be fatal if the infection is severe.

Children is more prevalence to the infection, thus we're going to discuss the sequelae and complications on children more.  

Complications of Ascariasis arisen due to 2 important process. 
1) Obstruction
2) Migration

In Ascariasis, if the worm burden is too severe, it might be huge enough to form a clump, called worm bolus which can obstruct the intestinal lumen. Problems arisen due to the obstruction. Other than watery diarrhoea, the infected child might show sign of project vomiting cause the food ingested were being stuck at the point of obstruction. Consumption of food might lead to abdominal discomfort and thus they may show sign of anorexia.

Malabsorption is another severe complication of Ascariasis in children. The worms in the intestine can block the intestinal surface and thus impair the ability of absorption. Lack of nutrient causes children to have stunded growth and they can present with steatorrhoea, short stature, skinny, night blindness....etc.

Another complication arisen when there is migration of adult worm from the intestine to elsewhere of the body. The migration can be trigger by drugs or temperature.

The migration of worm can causes problems at the site of migration. Normal sites of migration include mouth, anus, lungs, bile duct and pancrease. Migration to the mouth could cause the child to vomit worms; to the anus leads to worm emesis, to the lungs could lead to acute respiratory distress syndrome; to the bile duct and pancreas could causes acute inflammation.

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Treatment & Management of Ascariasis

The infection is usually treated by antiparasitic agents.  

The most commonly recommended agents are albendazole and mebendazole

1. Albendazole (single dose- 400mg stat)
2. Mebendazole (single dose -500mg stat or multiple dose 100mg b.d for 3/7
3. Pyrantel pamoate (single dose 10mg/kg)
4. Piperazine citrate (single dose 30-70ml stat)

ALL infection must be treated

Recheck after a month – treat again if still +ve 

Anthelmintics

Parasite biochemical pathways are sufficiently different from the human host to allow selective interference by chemotherapeutic agents in relatively small doses.

Albendazole (Albenza)

Decreases ATP production in worm, causing energy depletion, immobilization, and finally death.

Mebendazole (Vermox)

Causes worm death by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine where helminths dwell.

Piperazine citrate

Recommend for GI or biliary obstruction secondary to ascariasis; causes flaccid paralysis of the helminth by blocking response to worm muscle to acetylcholine.

Pyrantel pamoate (Antiminth)

Depolarizing neuromuscular blocking agent; inhibits cholinesterases, resulting in spastic paralysis of worm.

Ivermectin (Stromectol)

Binds selectively with glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death.

Levamisole (Ergamisol)

May inhibit worm copulation via agonism of L-subtype nicotinic acetylcholine receptors in male nematode muscles

Other supportive could be Vitamin and nutrient supplements to treat malabsorption or Oral Re-hydration Solution to treat dehydration.

In case there is acute obstruction of the intestine, surgical removal of the worm bolus is required.

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