Evaluation, Diagnosis and Treatment of Ascariasis: An Updated Review

Abstract

Ascaris lumbricoides (Round Worm) is the most common human helminth with a world wide distribution. Incidence of ascariasis remain very high in the tropical and sub tropical countries with poor sanitation, personal hygiene, and rural areas where defaecation in open place is still a common practice. Ascariasis is classified as a neglected tropical disease. Infections have no symptoms in more than 85 percent of cases specially if the number of cases are small. Pathogenecity and clinical features are either due to migrating larvae or due to adult worms. Larval migration may lead to allergic reactions, ascaris pneumonia. Adult worms are often responsible for nutritional deficiencies, toxic effects due to hypersensitivity &mechanical effects leading to intestinal obstruction. Ectopic ascariasis can lead to acute biliary obstruction, cholangitis, acute pancreatitis, acute obstructive appendicitis and peritonitis due to perforation of an intestinal ulcer or break down of a post operative suture line. Medical therapy with Albendazole is the first line drug ascariasis can be eliminated by preventing faecal contamination of soil. Advancement in recombinant protein technology may provide first step in discovery of Ascaris vaccine as well as pan helminthic Vaccine. This chapter is a updated review of ascariasis.

1. Introduction

GENUS:Ascaris lumbricoides Linnaeus 1758

Species:A. lumbricoides

The common roundworm

The study was conducted analysing the inputs from various articles presented with general description of Ascaris lumbricoides and study results were analysed.

Cram in 1926 mentioned the hookworm and the malarial parasite have been the objects of international campaign of far reaching scope while the ascarid has received only causal attention. And yet this parasite is of very great importance because it is so wide spread and the pathological effect on the individual may be so very serious.

Ascaris lumbricoides, a soil transmitted helminth is the largest nematode infecting human with a worldwide distribution. The nematodes are unsegmented ones. They are elongated and cylindrical with tapering ends.

The specific name lumbricoides is derived from its resemblance to earthworm (in Latin lumbricoides meaning earthworm).

Ascaris has been described from very ancient times. It was described in Egyptian papyrus and found in Egyptian mummies. This helminth has been described by Hippocrates and Aristotle. About 0.8 to 1.2 billion people around the world are infected with ascaris. It is more common in tropical and sub tropical countries around the world and most heavily affected population being in the sub Saharan Africa [1, 2, 3], Latin America, China and East Asia with poor sanitation, poor personal hygiene and places where defecation in open place is common practice.

Ascaris is classified as a neglected tropical disease [4, 5, 6].

Infections have no symptoms in more than 85% of the cases specially if the numbers of worms are small.

Children are most commonly affected [7]. Because of its global presence and potential to cause severe morbidity and mortality ascaris must be considered as a major health hazard.

Its global distribution is so high an editorial in Lancet in 1989 observed that if all the roundworms in the entire affected individual worldwide were placed end to end then they can encircle the world 50 times.

A species- Ascaris sum morphologically identical but biologically separate which is a pig roundworm rarely infect human being. It is unknown how many people are infected with ascaris sum worldwide.

2. Habitat

The adult worm lives in the lumen of small intestine (85% in jejunum [1, 8], and 15% in ileum) and maintain its position by muscle tone. Ascaris takes most of its nutrients from the partially digested food in the intestine. They can secrete inhibitory enzymes to protect itself from digestion by host’s enzymes. Adult worm survive for 1 to 2 years in human host after which it dies and spontaneously evacuated from the digestive tract.

3. Morphology

Adult worm– Largest intestinal nematode resembles an ordinary earthworm. When fresh from the intestine it is pale pink or light brown in colour but become white outside the body. The mouth opens at the anterior end and possesses three finely toothed lips- one dorsal and two ventral.

Male worm – It is 15 to 25 cm in length with a diameter of 3 to 4 mm. The tail end is curved ventrally to form a hook. The genital pore opens into the cloacae and carries two copulatory spicules.

Female worm- It is longer than male and measures 25 to 40 cm with a diameter of 3 to 6 mm. posterior end is straight and conical. The vulva opens at the junction of anterior and middle third of the body and this section is narrower and is called the vulval waist. A mature female worm lays up to 2,00,000 eggs per day. The eggs are passed in the faeces.

Eggs- Eggs can be fertilised or unfertilized.

1. Fertilised egg- Round or oval in shape, always bile stained. Fertilised eggs are embryonated and develop into infective eggs.

2. Unfertilized eggs- Narrower, longer, brownish in colour. They are non embyonated and non infective.

Both fertilised and unfertilized eggs may be found in a sample of stool or either type alone. Specimens showing only the unfertilized eggs signify that the host is harbouring only female worm.

4. Lifecycle

Man is the only natural host and there is no intermediate host. Lifecycle of the parasite were not known before 1916.

INFECTIVE AGENT – Embryonated eggs.

Mode of transmission – Infection occurs when embryonated eggs are swallowed with contaminated food and water.

Stage 1- Fertilised eggs containing the unsegmented ovum are passed with the feceas. They are not immediately infective.

Stage 2- Development in soil- under suitable climatic condition of temperature 25 to 30 degree centigrade, high humidity, and adequate oxygen supply fertilised eggs mault once and rhabtidiform larvae developed from the unsegmented worm within the egg cell in 10 to 40 days time. The fertilised egg of Ascaris is the most resistant and can remain viable in the hostile environment for many years.

Stage 3- Swallowing of infective eggs and liberation of larvae.

The swallowed eggs passed down to duodenum where egg shell weakened by the digestive juice and rhabtidiform larva about 250 microns in length and 14 micron in diameter liberated in upper part of small intestine.

Stage 4- Migration through the lungs.

The larvae penetrate the intestinal mucosa and enter the portal circulation and carried to liver. From liver it passes via the hepatic veins, Inferior vena cava and right side of the heart to the lungs in about 4 days. In the lungs they grow much bigger and moult twice. Subsequently they penetrate the capillary wall and enter the lung alveoli in about 10 to 15 days.

Stage 5- Re-entry into the small intestine.

From the lung alveoli the larvae pass up the bronchi and trachea, where they are coughed up and may be swallowed. The larvae pass down the oesophagus to the stomach and reach the upper part of small intestine- their normal habitat.

Stage 6- Maturity.

The larvae on reaching their habitat grow into adult worm. They become sexually mature in about 6 to 12 weeks time. The gravid female start laying eggs which is passed in the stool and the cycle is repeated [9, 10].

5. Clinical manifestations

5.1 Symptoms due to migrating larvae

Ascaris pneumonia (Loeffler’s syndrome) – Pulmonary manifestations take place during larval migration and characterised by low grade fever, cough, dyspnoea, urticaria and eosinophilia.

The sputum is often blood stained and may contain Charcot- layden crystals.

Chest x-ray may show pulmonary infiltrate with radiographic shadowing.

The larvae may be found in sputum and more often in gastric washing. This pneumonia usually clears up in 1 to2 weeks but sometimes may be severe [8, 11]. Ascaris induced eosinophilic myocarditis have been reported in literature [12].

5.2 Symptoms due to adult worm

1. Nutritional deficiency: Ascaris lumbricoides induces changes in the jejunal mucosal and intestinal muscle layers. There is coarsening of mucosa folds, crypt depth shortening, reduced mucus production and hypertrophy of muscle layers [13, 14].

   Where large numbers of worms are present specially in children interfere with proper digestion and absorption of food and can lead to protein energy malnutrition, vitamin A deficiency and impaired cognitive function in children [15].

2. Toxic effects: Hypersensitivity to Ascaris antigen can lead to fever, urticaria, Angioneurotic oedema, conjunctivitis.

3. Mechanical effects: This is the most important manifestation of Ascariasis. Bowel obstruction may occur in upto 0.2 per 1000 per year [7]. When large numbers of worms get strangled into a bolus may lead to luminal occlusion and acute intestinal obstruction [16, 17, 18]. Perforation may occur due to ischemic pressure necrosis by roundworm ball. It can precipitate intussusceptions, volvulus and closed loop obstruction. It may perforate through any ulcer of the alimentary tract and can lead to peritonitis. Free lying ascaris can be seen floating in the peritoneal cavity. We have reported a case of duodeno ureteric fistula caused by ascaris [19].

4. Ectopic Ascariasis: Migration is a common habit of ascaris. Fever, ingestion of some drugs and foods by the host and surgical anaesthesia is a predisposing factor for worm migration from its natural location. Going up it may pass through the oesophagus and coming out through mouth or nose. It may enter the trachea causing respiratory obstruction. Rarely it may enter the biliary or pancreatic duct causing obstructive jaundice, cholangitis, acute pancreatitis and liver abscess. Going down worm may enter the appendix giving rise to acute obstructive appendicitis [9, 10, 20, 21, 22]. In gastrointestinal surgery requiring resection and anastomosis it may perforate through the suture line. So in endemic areas it is recommended pre-operative deworming before gastrointestinal surgery.

6. Diagnosis

1. Direct evidence:

   Larvae: During the pulmonary disease larvae may be found in sputum or more often in gastric juice. Findings of Charcot – layden crystal in sputum and eosinophilia may further help in the diagnosis.

   Eggs: The best diagnostic test is still the stool examination demonstrating eggs as the Ascaris eggs are passed in stool in enormous numbers. It is easy to detect the affected person by direct microscopical examination of a saline emulsion of the stool.

   It is important to note that stool can be negative while the worm migrates and matures. Both fertilised and unfertilized eggs may be present, occasionally only one type is seen. If the patient harbours male ascaris only, eggs are not found in the stool.

   Microscopical examination of bile obtained by duodenal aspirate may reveal ascaris eggs. Eggs in the biliary tree can act as a nidus for stone formation.

   Adult worms: Occasional findings of adult worm in stool and vomit.

2. Serological tests: Detection of Ascaris antibody by indirect hemagglutination and ELISA test.

3. Blood examination: Eosinophilia in early stage of infection.

4. Imaging:

   X-ray Abdomen: Bolus of worms may be found with whirled appearance (whirlpool sign) in intestinal obstruction.

   Barium Meal Follow through: Round worm may be identified with barium within.

   CECT Abdomen: may show curvilinear structure within the lumen of intestine.

   USG and MRCP: may demonstrate worm in CBD and pancreatic duct in the setting of obstructive jaundice, acute cholangitis, and acute pancreatitis.

7. Treatment/management:

1. PREVENTION – Ascaris can be eliminated by preventing faecal contamination of soil.

   Improved access to sanitation, prohibition of open defecation, use of clean toilet by all community members, provision of clean drinking water, maintenance of general hygiene and health education, avoiding of untreated human fecaes as fertiliser will help in reducing ascsaris egg contamination.

   Washing of vegetables with water containing iodine 200 PPM for 15 minutes kills the eggs of Ascaris and other helminth.

   In areas where more than 20% of population is affected treating the whole community with deworming agent is recommended as prophylaxis [7]. This is known as Mass drug administration and targeted population specially at the school age children [23]. As recommended by WHO, drug of choice is Albendazole or Mebendazole.

2. Medications – To prevent serious complications even mild cases of ascariasis should be treated with proper medications. Those recommended by WHO for ascariasis are Albendazole, Mebendazole, Levamisole and Pyrantal pamoate [24].

   Medical therapy with albendazole 400 mg as a single dose is the first line of drug. Second choice is mebendazole 100 mg twice a day for 3 days or 500 mg as a single dose or Ivermectin 100 microgram per kg to 200 microgram per kg once [25].

   The major site of action of albendazole and mebendazole is the microtubular protein “Beta Tubulin” of the worm. It binds to the beta tubulin of the worm with high affinity and inhibits its polymerisation. Intracellular microtubules in the cells of the parasite lost. It blocks glucose uptake by the parasite. Hatching of nematode eggs and their larvae are also inhibited. Ascaris ova are also killed. Albendazole is contraindicated during pregnancy and children less than 2 years of age.

   Pyrantal pamoate: Pyrantal activates nicotinic cholinergic receptors in the worm causing spastic paralysis. Worms are then expelled. For Ascaris single dose of 11 mg/kg is recommended. Pyrantal may induce intestinal obstruction in the presence of heavy worm load. It can be used in pregnancy.

   Piparazine: It causes flaccid paralysis of the worm and worms are expelled alive by peristalsis. Often a purgative is given with it. Because of its ability to relax ascaris it is of particular value in intestinal obstruction due to roundworm. It can be used during pregnancy.

   Other medications:

   Nitazoxanide

   Hexylresorcinol

   Ivermectin

   Levamisole

   Tetramisole

   Children should receive Vitamin A supplementation because of vitamin A deficiency in ascasriasis. Retreatment in 3 to 6 months is recommended in endemic areas.

3. Vaccine: There is a significant challenge to control and eradicate ascariasis especially in endemic areas. Mass drug administration programme with benzimidazole anti-helminthics are the only methods available to control infection. Ascaris eggs are highly resistant in adverse environment which limit the ability of mass drug administration to break the transmission cycle in the community. So post treatment reinfection is common. Besides frequent anti-helminthic administration may result in complications including development of drug resistance. So only solution to eradicate the disease globally is vaccination against ascariasis. However till date no effective vaccine available for human clinical trial. Advancement in recombinant protein technology may provide the first step in generating an ascaris vaccine as well as pan-helminthic vaccine [26].

4. Surgery: In sub acute intestinal obstruction, conservative treatment in the form of IV fluid, NG suction and hypertonic saline enema is recommended.

   Hypertonic saline enema disimpact the roundworm bolus and stimulates intestinal peristalsis. Operation is required for acute intestinal obstruction and perforation.

   During laparotomy, attempt should be made to milk the ascaris mass to the colon through ileo-caecal valve for natural evacuation.

   In healthy bowel, enterotomy and removal of round worm bolus may be required.

   Perforation, gangrene require resection and anstomosis.

   In perforation it is safe to exteriorize the perforation site as ileostomy because chances of suture line breakdown due to roundworm activity are increased. Sometimes roundworms may be an incidental finding in typhoid perforation, tuberculosis, and other causes of intestinal obstruction.

   Post operative deworming is always necessary to kill the residual egg.

   ERCP – In Pancreaticobiliary ascariasis ERCP may be both diagnostic and therapeutic [27].

8. Present review result shows

1. Ascaris is the commonest helminth affecting human.

2. Despite improvement in living standard children are frequently affected specially in the developing countries. In many communities prevalence may be in excess of 80% [8, 28].

3. Roughly one-quarter of the population are affected.

4. Majority of the patients are asymptomatic.

5. Symptoms develop when worm burden is high.

6. Ascariasis has enormous morbidity and affects many organs in the body but fatalities are usually due to intestinal and pancreatico-biliary ascariasis.

7. Inspite of modernization, ascariasis is regarded as neglected tropical disease.

8. Lozano R et al. in Lancet (December 2012) reported ascariasis caused about 2700 directly attributable death down from 3400 in 1990 [29]. Indirectly attributable death due to malnutrition may be much higher.

9. Health education, improvement of personal hygiene, improvement of sanitation in community, proper disposal of human faeces,providing clean drinking water are all important to help eradication of the disease.

10. Albendazole is the drug of choice for ascariasis with cure rate over 95% and gradual reduction of eggs in the next few weeks in 99.5%

11. Patient with intestinal obstruction and pancreatico biliary complications, a very high index of suspicion is of paramount importance specially in the endemic areas in order to avoid serious complications.

12. No effective vaccine for human trial available till date.