Ascariasis is a common parasitic infection. This article tells all there is to know about Ascaris lumbricoides infection.
Ascariasis is a common parasitic infection that typically affects the small intestine. It is a frequent type of roundworm infection, a particular type of parasitic worms widely distributed worldwide. Ascaris lumbricoides infection represents around 10% of all roundworm infections worldwide. Although most infections are without symptoms (asymptomatic), sometimes the parasite can cause important problems in the intestines, lungs, and other organs.
As with many other intestinal parasitoses, ascariasis is more common in developing tropical countries with poor sanitation policies. In fact, ascariasis represents a significant public health problem in the developing world.
The world health organization (WHO) estimates that there are around 800 million ascariasis cases worldwide; the great majority of these cases occur in developing regions such as sub-Saharan Africa (140 million), South America (84 million), and the middle east (23 million).
The disease affects mostly children between the ages of five and fifteen, usually in combination with other parasitic infections such as Trichuris trichiura infection and hookworm infection. Children are more likely than adults to show symptoms (become symptomatic) and develop severe complications due to heavy infection. Intestinal obstruction, which is the most feared complication in children, causes 60.000 deaths a year.
What is the lifecycle of an Ascaris lumbricoides worm?
Ascaris lumbricoides is the largest roundworm around; an adult worm can be up to 35 cm long. An Ascaris lumbricoides worm can be either male or female. Female worms produce eggs, which are later fertilized by nearby male worms.
Once an egg is fertilized, it becomes an infective egg, which means it can hatch inside the small intestine producing larvae that penetrate the intestinal wall to enter the portal vein, go through the liver, and then into the lungs. The same larvae are later expectorated or swallowed and reach the small intestines once again. They become adults within 65 days.
Adult worms subsist by eating the host’s digestion products, which causes malnutrition in children, along with retarded growth and greater susceptibility to other infections. Infected individuals usually have 4 to 16 worms in their small intestine. Nevertheless, these numbers can be much higher in severe infections. An Ascaris worm has a lifespan of 10 to 24 months. For an Ascaris infection to persists beyond the parasite’s two-year lifespan, the individual in question has to be reinfected at some point.
How do you get ascariasis?
A person is infected by eating Ascaris eggs excreted in human feces. Although most people don’t directly eat human feces, there are other ways to get infected. For example, eating and drinking food or water contaminated by infected human feces. Also, many children put their hands in their mouths after playing with soil. If the soil is contaminated with Ascaris eggs, the kid in question will be infected.
Ascaris lumbricoides suum is a type of Ascaris that infects swine that appears to be responsible for most ascariasis cases in developed countries.
What are the symptoms of ascariasis?
Depending on its migration phase, ascariasis causes different sets of symptoms.
During the early infection phases, when the larvae migrate through the lungs, ascariasis might cause respiratory symptoms such as:
- Difficulty breathing
- Chest pain
- Cough with bloody sputum (bloody or reddish mucus)
Suppose you seek medical attention during this phase. In that case, your physician might hear wheezes similar to those in asthma while auscultating your chest. Late in the migratory phase, patients might also develop fever and urticaria (hives) in reaction to the parasite.
All of these respiratory symptoms are part of Loeffler Syndrome, a transient respiratory illness associated with several parasitic infections. It causes cough, fever, wheezes along with high eosinophils in the complete blood count and particular chest X-ray findings.
When the host swallows the larvae and falls into the small intestines, gastrointestinal symptoms may or may not appear. Common intestinal ascariasis symptoms include the following:
- Nausea and Vomiting
- Diarrhea or irregular stools
- Abdominal pain
- Abdominal discomfort
- Presence of a parasitic roundworm in the stool
The GI symptoms are usually vague and recurrent; patients usually don’t pay much attention because they tend to be rare and mild. The real problem with ascariasis is the complications it causes when adult worms migrate outside the small intestines to organs like the pancreas or the biliary system.
What are the complications of ascariasis?
Complications are mainly due to 2 things, erratic migration of the parasite or having too many adult worms. Several ascariasis complications constitute severe surgical emergencies (they need surgery as a treatment).
The most common complication of intestinal ascariasis is bowel obstruction. In endemic areas (where there are too many cases) such as India and South America, Ascaris lumbricoides infection represents one of the main causes of intestinal blockage in children. Bowel obstruction due to Ascaris lumbricoides infection is the consequence of an aggregated mass of ascariasis worms blocking the small bowel’s lumen.
Symptoms are progressive; they begin with moderate colicky pain that worsens within hours combined with constipation and vomiting (sometimes with worms). If not treated, it can cause bowel infarction, perforation, and peritonitis.
What happens when Ascaris lumbricoides migrates outside the small bowel into the liver and pancreas?
Pancreatic and hepatobiliary ascariasis is one of the most common and potentially dangerous ascariasis complications, along with intestinal obstruction. When worms migrate into the pancreas through the small bowel, they can move into the system that transports bile from the liver into the intestines (biliary system).
A heavy worm load is the main factor that promotes migration to the pancreas, the biliary system, and the liver itself. Ascaris worms that penetrate the pancreatic duct or the biliary ducts get trapped there and die, causing an obstruction.
What are the complications of biliary ascariasis?
When the parasite migrates into the biliary tree, it can cause the following complications:
- Biliary colic: This is an acute severe pain in the upper right portion of your abdomen accompanied by nausea and vomiting. These pain episodes can come and go for months. Most biliary colics are the consequence of gallstones blocking a part of the biliary pathways called the cystic duct. Still, any obstruction in the biliary system can cause symptoms. Biliary colic is a consequence of a temporary block; if this obstruction becomes permanent, it can lead to a more severe consequence that requires hospitalization and surgery.
- Cholecystitis: When the obstruction in the cystic duct becomes permanent, the gallbladder behind it begins to swell. As biliary colic, gallbladder inflammation causes pain in the right upper quadrant, but in this case, pain does not go away; it increases progressively, eventually becoming unbearable, nausea and vomiting are usually present, and many patients also report fever. Doctors can differentiate cholecystitis from biliary colic because in the former constant pain lasts for more than 6 hours.
- Cholangitis: Differently to what happens in the previous two conditions, obstruction, in this case, occurs in the common bile duct, which is further down the biliary tree. Cholangitis presents with fever, right upper portion abdominal pain, abdominal tenderness, and jaundice (yellow coloring of the skin). It has a higher risk of complications (sepsis) and a higher mortality rate than cholecystitis. Recurrent pyogenic cholangitis is characterized by recurrent episodes of jaundice and upper abdominal pain due to stone formation in the bile ducts. Some studies suggest an important correlation with Ascaris lumbricoides infection and recurrent pyogenic cholangitis in endemic areas.
Can Ascaris worms reach the liver?
Ascaris lumbricoides can reach the liver through the hepatic ducts forming a hepatic abscess. Symptoms include right upper tenderness in the abdomen, high fever, an enlarged liver. It is, however, very rare and has an extremely low incidence with few described cases. The mortality rate is unknown.
What happens when worms reach the pancreas?
The two most common causes of pancreatitis are alcoholic poisoning and obstruction of the pancreatic duct by gallbladder stones. However, an ascariasis worm that obstructs the pancreatic duct is a recognized and reasonably frequent cause in endemic areas. Acute pancreatitis is a potentially dangerous condition in which the pancreas’ inflammation can lead to a systemic inflammatory response.
Pancreatitis patients usually complain about upper abdominal pain spread to the back in a band-like pattern. There also nausea and vomiting, low fever and abdominal tenderness, bloating, and indigestion. It has a sudden onset, and it might take several days before inflammation settles down with treatment. Many cases require a hospital stay and IV treatment.
Acute pancreatitis due to ascariasis or any cause can induce either of the following complications:
- Fluid sacs inside the pancreas are called pseudocysts; they cause dull abdominal pain and frequently get infected.
- Pancreatic necrosis, inflammation can decrease blood flow to the pancreas, causing part of the tissue to die; this can lead to infection, sepsis, and multiple organ failure.
- Diabetes (the pancreas is responsible for producing insulin).
Is ascariasis an important cause of malnutrition?
Intestinal parasites like Ascaris lumbricoides are an important cause of malnutrition and failure to thrive in children in developing countries. The parasite also contributes to cognitive deficits and mental retardation in infected children that live in endemic areas.
Who is at risk for ascariasis?
Everyone can get ascariasis, however certain risk factors and behaviors increase the risks of suffering from the disease and its complications. Some of the most important risk factors include:
- Exposure to contaminated dirt (people in occupations that involve contact with dirt like construction workers and farmers)
- Visiting or living in a subtropical area. This includes developing countries and parts of the developed world, such as New Mexico and Arizona in the United States
- Use of contaminated feces as fertilizer for crops
- Absence of proper mechanisms for stool disposal
- Extreme ages (younger than 15 or older than 65)
- People with defects in their immune system (HIV patients, cancer patients, and those who use systemic corticosteroids) have a higher risk of infection and a higher risk of developing severe complications like cholangitis and pancreatitis
How is ascariasis diagnosed?
The best way to diagnose ascariasis is through a stool sample. Stool examination under expert eyes reveals ascariasis eggs. Still, as you may recall, the parasite has a complex life cycle. It might take up to forty days for the eggs to hatch, larvae to migrate through the portal system to the lungs, and adults to mature and begin producing eggs. Therefore, stool examination may return a false negative result during the first 40 days of infection.
Providing several samples from different days increases the likelihood of detecting parasites in infected patients. During the pulmonary phase of the disease, the microscopic examination of the sputum may reveal the presence of migrating larvae.
Routine blood work is not particularly helpful in the context of ascariasis without complications. During the lung phase and the disease’s intestinal phase, a full blood cell count may reveal a high eosinophil count suggestive of parasitic infection. The absence of a high white cell count is useful to rule out pneumonia in the context of Loeffler syndrome. Anemia is a common finding in malnourished children with ascariasis.
What imaging tests are useful in ascariasis?
Imaging tests are very helpful during the pulmonary and intestinal phases and to detect and diagnose complications such as hepatobiliary ascariasis, pancreatitis, and intestinal obstruction. Some useful imaging tests include:
- Chest X-rays: Particularly helpful during pulmonary larvae migration. It might reveal several lung opacities during this phase.
- Abdominal X-ray: Worms can be seen in plain abdominal X-rays of patients with adult worms in their small intestine. Abdominal X-rays are also very helpful in the context of intestinal obstruction due to ascariasis. The most common finding in intestinal obstruction is the presence of abnormally dilated small bowel loops.
- Abdominal Ultrasound: Abdominal ultrasonography is probably the most important test in the context of hepatobiliary ascariasis and pancreatitis. It can identify worms inside the stomach, duodenum, gallbladder, biliary tree, and pancreatic duct. Abdominal ultrasound also helps in detecting hepatic abscesses.
- Endoscopic Retrograde Cholangiopancreatography: Commonly known as ERCP, is a complex procedure with diagnostic and therapeutic use. It is an office-based procedure where the surgeon or gastroenterologist introduces a small camera through your mouth into the small intestine, pancreatic duct, and biliary tree. It allows the physician to visualize the worms and remove them as well.
What type of specialists treat ascariasis?
The type of specialist depends if there are complications or not. Most cases of ordinary, uncomplicated ascariasis can be treated by a primary health provider or a family physician, or a general pediatrician in a child’s case. Gastroenterologists and surgeons are of vital importance in managing complications such as intestinal obstruction, cholecystitis, pancreatitis, cholangitis, and hepatic abscess. Although some of the ascariasis complications might respond to medical treatment, many of them, like intestinal obstruction and appendicitis, constitute surgical emergencies.
What is the treatment for ascariasis?
Early ascariasis treatment during the intestinal phase prevents complications like intestinal obstruction and hepatobiliary ascariasis. It also leads to better development in children that suffer from the disease.
Dead larvae during the pulmonary phase can produce severe pneumonitis. Accordingly, patients with Loeffler syndrome should not receive specific ascariasis treatment during this stage. If respiratory symptoms are severe enough, an asthma-like treatment with nebulized salbutamol and an IV corticosteroid like prednisolone or hydrocortisone can produce relief before the patients move on to the intestinal phase.
Specific antiparasitic drugs with activity against Ascaris lumbricoides
- Albendazole: Causes parasite energy depletion, paralysis, and death. It is the drug of choice for intestinal ascariasis. It can cause important adverse effects in pregnant women. Treatment requires a single dose of 400mg.
- Mebendazole: Useful when ascariasis infection coexists with a whipworm infection, is the second drug of choice after albendazole.
- Pyrantel Pamoate: This is the treatment of choice for pregnant women with ascariasis.
- Ivermectin: An alternative to mebendazole and albendazole. These days doctors prefer avoiding ivermectin due to its many adverse effects.
These drugs kill only adult worms; infected individuals who live in endemic areas may still carry larvae; therefore, all patients in endemic areas must be evaluated three months after completing treatment.
Patients with intestinal obstruction may require surgical intervention. Notwithstanding, recent studies show that up to 89% of children with intestinal obstruction due to ascariasis benefit from conservative treatment with intravenous fluid, no oral intake, antibiotics, and piperazine drip through a nasogastric tube combined with glycerin and paraffin enemas.
Antiparasitic drugs are not effective in patients with hepatobiliary disease. Furthermore, the death of parasites inside the biliary tree worsens inflammation and obstruction. Patients with only mild hepatobiliary symptoms can benefit from simple observation and monitoring during the first 48 hours; however, if symptoms persist or the patient shows severe cholangitis or cholecystitis symptoms, worm removal through ERCP is the treatment of choice. An important percentage of patients will still require invasive surgery.
What is the prognosis for ascariasis?
More than 95% of patients are completely cured after a single dose of albendazole. However, reinfection rates in endemic areas are very high without significant sanitation. Preventive measures that prevent reinfection include:
- Avoiding contact with soil that may be contaminated with human feces
- Avoid using fertilizers of unknown precedence
- Frequent handwashing, particularly before eating
- Wash fruits and vegetables before eating and cooking, particularly those that grow in soils fertilized with manure.
Do you have symptoms of this disease?
This tool is an Ascariasis Symptoms Checker. It gathers the most important signs, symptoms, and risk factors for the disease. Therefore, the tool will tell anybody who uses it the likelihood of their symptoms because of ascariasis. Using the tool is free and would only take a few minutes.