Ascaris Lumbricoides is a Nematode sometimes considered as the ‘’large worm” of human capable of growing to a length of up to 35 cm. These large roundworms are the most common parasitic worm in humans. They are responsible for the disease term Ascariasis which is one of the group of neglected tropical diseases with an estimate of one-sixth of the human population infected by large worms and other worms.It is common in tropical countries with hygiene insufficient, more and more rare in temperate countries.
Around the globe, an estimate of 1 billion people are infected with Ascaris. lumbricoides.These worms are most common in sub-Saharan Africa,China, the Americas and east Asia.
Ascaris lumbricoides eggs are extremely resistant to desiccation,strong chemicals and low temperatures. The eggs can remain viable in the soil for several months or even years.
Morphology of Ascaris lumbricoides
The adult roundworms live for 6 to 18 months in the jejunum where they ingest food particles.
They migrate easily and can end up in different viscera. The males roundworm measure from 12 cm to 17 cm long and 2 to 4 mm in diameter; their extremity is curved in butts while females measure from 20 to 25 cm and 3 to 6 mm in diameter
The eggs are Ovoid in shape measuring 60 to 70 μm long by 40 to 50 μm wide and are laid in very large numbers in the intestine.Up to 200,000 eggs are laid per day and evacuated with feces . These eggs are surrounded by a brown double shell, with a very characteristic hinted appearance, which makes them very resistant in the external environment.There exist two types of ascaris eggs : Fertilised and unfertilised egg (unfertilized eggs which are more elongate (85-95 x 45µm) and decorticated
Transmission of Ascariasis
- Transmission of Ascariasis occurs mostly by fecal-oral routes.That is Ingestion of infective eggs from soil contaminated with human faeces, uncooked produce contaminated with soil containing infective eggs.
- Infections are more common where sanitation is poor and the uses of human faeces as sources of fertilize
- Contaminated water and food where The eggs then emerge into larvae in the small intestine and penetrate the intestine, gaining entry into the bloodstream and are being taken into the lungs.
- Transmission does not occur from direct person-to-person contact or from fresh faeces.
Life Cycle of Ascaris lumbricoides
These large roundworms, infects humans when they ingest the fertilised egg which later develop into a larval worm also called rhabditiform larva.The larva penetrates the wall of the duodenum entering the bloodstream.The unfertilized eggs may be ingested but luckily are not infective.
Fertile eggs embryonate becoming infective after 18 days to several weeks, depending on the environmental conditions such as optimum temperature,moist, warm and shaded soil.It is then carried to the liver and heart, and enters the pulmonary circulation to break free in the alveoli, where it grows and molts.
In three weeks, the larva passes from the respiratory system to be coughed up, swallowed, and thus returned to the small intestine, where it finally matures to an adult male or female worm. Fertilization can now occur and the female produces as many as 200,000 eggs per day for a period of 12–18 months. These fertilized eggs become infectious after two weeks in soil; they can persist in soil for 10 years or more as earlier stated.
Ascaris lumbricoides eggs are extremely resistant to desiccation,strong chemicals and low temperatures.because of a lipid layer which also makes them resistant to the effects of acids and alkalis and other chemicals. This resilience helps to explain why this nematode is such a ubiquitous parasite
Symptoms of Ascaris lumbricoides
- Ascaris lumbricoides infection may be asymptomatic (no symptoms) in mild infecton.
- The presence of the adult worms in the lungs may cause irritating non-productive cough and chest pain
- Ascaris pneumonia with symptoms such as fever, cough, and eosinophilia (Presence of increase eosinophil) can occur, This condition is referred to as Loeffler’s syndrome or Loeffler’s pneumonia
- There may be Fever when the adult worms are in the lungs and a Chest x-ray may show evidence of pneumonitis (Loeffler’s syndrome)
- Because children turn to put their dirty hands in the mouth, Heavy infections, especially in these childrens are associated with non-specific symptoms such as nausea, bloody sputum,vomiting, intestinal ulcer(s),abdominal discomfort and anorexia (loss of appetite)
- Large bolus of worms may cause abdominal pain and small bowel obstruction
- The highest morbidity is found in children, especially in those with a high worm burden. Ascaris lumbricoides which can lead to reduced physical fitness, growth retardation, and respiratory and gastrointestinal problems
Laboratory Diagnosis of Ascaris lumbricoides
- The diagnosis of ascariasis mostly depends on the identification of the adult worms passed through the rectum or from other body orifice such as the nostril and mouth,
- By identification of the eggs of Ascaris lumbricoides in stool sample, vomitus, sputum, or small bowel aspirate
- Eggs, larvae or adult worms may also be identified in tissue sections.
- Once the fertile females within the gut begin to release eggs, the diagnosis of ascariasis can usually be made by direct fecal smears (Stool wet mount observation)
- For better result,concentration techniques using centrifugation such as formalin-ethyl acetate method ,formol ether and flotation concentration techniques may facilitate diagnosis and eggs recovering.
- There may also be a rise in eosinophil concentration (Eosinophilia) of 30% to 50%
Prevention of Ascaris Lumbricoides
In order to preventing any fecal-borne disease such as Ascariasis requires educated hygienic habits/culture and effective fecal treatment systems hence the following points can be taking into consideration
- Avoid use of human manure as fertilizer
- Properly wash vegetables, fruits and foodstuff before cooking or eating (Ascaris eggs can resist extreme temperature)
- Practice good hygiene by washing your hands properly with clean water before eating,avoid putting hands in the anus,especially children
- Only drink clean water,Bleach does not readily kill Ascaris lumbricoides eggs, but it will remove their sticky film, to allow the eggs to be rinsed away.
- Also remember keeping your environment clean The treatment
Treatment for Ascaris Lumbricoides
Recommended treatments very effective against these large roundworms are
- Flubendazole (Fluvermal®) tablet or suspension.Take 100 mg tablet, morning and evening, during for a period of three days.
- Albendazole (Zentel®), tablet or suspension.Take 400 mg as a single cure.
- Pyrantel pamoate (Combantrin®), 12 mg / kg as a single cure
- Mebendazole (100 mg twice daily for 3 days)
- Oxantel pamoate (single dose of 10mg/kg)
- Piperazine citrate (75mg/kg (max. 3.5g) single dose daily for two days)
NB : albendazole and Mebendazole are contraindicated in pregnancy case but patient can take pyrantel pamoate and piperazine which are safe.
Some complication of Ascariasis infections
Patient suffering from ascariasis may suffer from the following during prolonged infection
- Intestinal obstruction – distal ileal obstruction due to bolus of worms
- Chyluria resulting from a painless passage of milky white urine especially after a fatty meal that may become painful when it clots.
- Strictures of the biliary tree
- The worm may enter the biliary tree through the ampulla of Vater and cause severe biliary pain
- Suppurative cholangitis from infestation of common bile duct
- Also cause liver abscesses
- It may causes malnutrition in children as the worms competes for food with the child and preventing absorption
- Empyema of the gallbladder
- Obstructive jaundice – from infestation of the common bile duct
- Acute pancreatitis when the worm lodges in the pancreatic duct
- In rare cases, the worms could cause perforation of the small bowel
- The worms may invade the appendix and cause acute signs of appendicitis
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