What Is the Pathophysiology of Ascaris Lumbricoides?
Ascaris lumbricoides cause a widespread intestinal roundworm infection called ascariasis. The cases are mainly seen where personal hygiene and proper cleanliness are not accessible.
Ascariasis in pigs is caused by Ascaris suum. These are the roundworms present in the intestines of the pigs. Roundworms of pigs and humans are two different species; however, infection from pigs can be transmitted to human beings.
Transmission
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Transmission of eggs occurs from hand to mouth. However, it can also be transmitted through raw fruits and vegetables cultivated in the soil degraded with the eggs of Ascaris.
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Eggs of the ascaris may also be present in the water and can be transmitted upon water consumption. The infection can be transmitted upon inhalation in areas with a high number of worms. It takes about nine to 12 days after egg ingestion before the signs and symptoms of Ascaris infection appear.
Dissemination or Spread of the Disease
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Once the eggs are ingested, they hatch inside the small intestine and grow into small larvae. These larvae then penetrate the mucosa of the intestine.
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The larvae travel to the lungs through venous blood circulation. It then spreads through the alveoli and the bronchial branches, causing pulmonary ascariasis.
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It then spreads to the throat. It is again swallowed with food, water, and saliva and returns to the intestine. Finally, the maturation of the larvae into adult worms occurs in the intestines.
Pathogenesis
Adult worms live up to ten to 24 months inside humans. The adult male ringworm is 5.90 to 13.77 inches long. The adult female worms are larger than the males and are 15.74 inches long. The fertile female worms pass out eggs after entering the host. The eggs are passed out along with the feces, where they easily survive in the warm and moist environments of the soil. After maturation in the intestines, the larvae travel to the lungs and cause symptoms like cough and wheezing. The eggs are not released during this time, so laboratory investigations for ova and parasites in stool are impossible. Eggs are not released in the feces until after 40 days of the appearance of pulmonary manifestations. Once they are moved to the throat and swallowed again, it lies in the intestines, matures, and lay eggs.
Adult worms survive in the intestine for around six to 24 months and can result in minor or complete bowel obstructions. Transport of the worms to the appendix causes acute appendicitis (inflammation of the appendix). They can also transport to the hepatobiliary system or pancreatic ducts. It rarely migrates to organs like the kidneys or the brain. Patients with many worms in the intestines lead to intestinal obstruction, which further results in intestinal perforation. It takes almost nine weeks from egg ingestion until the next cycle of eggs is released into the intestines again. Another three weeks are needed before the eggs become motile and cause infection in the new host.
What Are the Symptoms of Ascariasis?
Ascariasis is usually asymptomatic, and patients do not present with the symptoms initially. Symptoms that occur in the later stages are divided into early and late.
The Early or Larval Migration Stage: This occurs post four to 16 days of egg ingestion. Larva migrates through the lungs, and hence, respiratory symptoms are commonly seen. Fever, dyspnea (difficulty breathing), wheezing (whistling sound that occurs while breathing), and non-productive cough are a few of the symptoms.
The Late Stage: This occurs after six to eight weeks of egg ingestion. The late stage occurs if there is an overloading of parasites in the body. Gastrointestinal symptoms are most common during this stage. The most common signs are:
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Worm mobility (from mouth, nose, and anus).
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Stomach pain mainly in the upper abdominal region.
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Vomiting.
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Tingling sensation in the throat.
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Dry cough.
Other Symptoms Include:
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Fever.
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Jaundice (in cases of bile duct obstruction).
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Pale appearance or pallor due to anemia.
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Cachexia (muscle wasting due to malnutrition).
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Urticaria, which is a skin reaction.
Pulmonary or Respiratory Symptoms Include:
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Wheezing (whistle sound made during breathing).
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Rales (the crackling sound heard during breathing).
Abdominal Symptoms Include:
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Pain in the abdomen may be localized or diffuse.
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Intestinal obstruction signs like vomiting and constipation.
What Is the Treatment of Ascariasis?
Ascariasis infections are treated with antimicrobial therapy, namely antihelminthic drugs. Antimicrobial drugs are prescribed for all symptomatic and asymptomatic ascariasis infections. Repetition of the drugs is advised as the infection is highly susceptible to remission. Antihelminthic drugs belonging to Benzimidazoles are the drugs of choice for asymptomatic and symptomatic treatment. Systemic absorption of the drug is poor; hence, they have low toxicity levels and act directly on the worms. The most common drugs belonging to Benzimidazoles are Albendazole and Mebendazole.
Cases of bowel or hepatobiliary obstructions are usually managed by intravenous hydration, monitoring the electrolytic level, and nasogastric suctioning. Surgical and gastroenterological consultations are required in case of worm load or complete obstructions. Laparotomy, which is accessing the abdominal contents by making a surgical incision, is the surgical choice in such patients. Colonoscopy for the lower part (large intestine) and esophagogastroduodenoscopy for the upper intestine are used to remove the large masses of worms localized in these regions.
How Can Ascariasis Be Prevented?
Screening programs are conducted in the endemic (consistently present but only in a particular region) areas to screen out the carriers of the disease, which will assist in eradicating the disease. Sanitation programs should be organized to create awareness to stop defecating in the open, as soil serves as a good habitat for the Ascariasis lumbricoides worm. In addition, public awareness should be created on the importance of washing hands. Albendazole is prescribed to all immigrants who are risked as carriers of the worms or are subjected to regions of high worm dose. Even after the infection subsides, it is important to conduct a stool ova test to reduce re-infection chances. The occurrence of re-infection is very common in ascariasis.
Conclusion
Ascaris lumbricoides are one of the most common infections. Most patients show respiratory and gastrointestinal symptoms. The patient's prognosis is very good. However, patients with high worm loads show serious complications like gastric obstructions. Public awareness and educational programs will help eliminate the disease.
