Ascaris lumbricoides- Lab Diagnosis, Treatments, Prophylaxis
Ascaris lumbricoides is a large parasitic worm that causes ascariasis in humans. It belongs to the genus Ascaris, which includes several species of roundworms that infect animals. A. lumbricoides is the most common parasitic worm in humans, affecting an estimated 807 million to 1.2 billion people worldwide. It is more prevalent in tropical and subtropical regions, where sanitation and hygiene are poor.
A. lumbricoides has a complex life cycle that involves migration through various organs of the human body. The infection begins when a person ingests eggs that are shed in the feces of an infected person and contaminate the soil, water, or food. The eggs hatch in the small intestine and release larvae that penetrate the intestinal wall and enter the bloodstream or lymphatic system. The larvae then travel to the lungs, where they break out of the capillaries and enter the air sacs (alveoli). From there, they move up the respiratory tract and are coughed up and swallowed again. The larvae then reach the small intestine again, where they mature into adult worms and mate. Adult worms can live for up to 18 months and produce up to 200,000 eggs per day. The eggs are passed out with feces and can survive in the soil for up to 10 years.
Most people with A. lumbricoides infection do not have any symptoms or mild symptoms such as abdominal discomfort or pain. However, in some cases, the infection can cause serious complications such as intestinal obstruction, malnutrition, growth retardation, liver or pancreatic damage, allergic reactions, or respiratory distress. The diagnosis of A. lumbricoides infection can be made by finding eggs or worms in stool samples, bile samples, sputum samples, or gastric washings. Blood tests may also show eosinophilia (increased number of eosinophils) or antibodies against the parasite. Imaging techniques such as X-rays, ultrasound, or endoscopy may also reveal worms in the intestines or other organs. The treatment of A. lumbricoides infection involves taking anti-parasitic drugs such as albendazole, ivermectin, or mebendazole, which kill the adult worms and prevent further egg production. In some cases, surgery may be needed to remove worms that cause obstruction or complications. The prevention of A. lumbricoides infection requires improving sanitation and hygiene practices, such as using latrines, washing hands, treating sewage, and avoiding raw or unwashed vegetables or fruits.
The laboratory diagnosis of ascariasis can be made by detecting the parasite or its eggs in various specimens, such as stool, sputum, bile, or tissue. The diagnosis can also be supported by blood tests or imaging techniques.
- Adult Worm: In heavy infections, the adult worm can be seen by the naked eye in the stool or sputum of the patient. Sometimes, the worm may come out of other body openings, such as the mouth or nose. Imaging techniques such as barium meal, plain abdominal film, ultrasound, or endoscopic retrograde cholangiopancreatography (ERCP) can also reveal the presence of adult worms in the small intestine or the biliary tract.
- Larvae: In the early stages of infection, when migrating larvae cause Loeffler`s syndrome, the diagnosis can be made by finding the larvae in sputum or gastric washings. Eosinophilia may be present in the blood, especially during the larval migration through the lungs. Chest X-ray may show patchy pulmonary infiltrates.
- Specimen: Stool, bile
- Method: The saline emulsion of stool is examined under a microscope for the presence of eggs. Both fertilized and unfertilized eggs are usually present. The eggs are oval, thick-shelled, and have a rough surface. The fertilized eggs contain a developing embryo, while the unfertilized eggs are larger and contain a mass of cells. If very few eggs are present, the concentration technique can increase the detection rate of microscopy. Eggs can also be found in bile obtained by duodenal aspirates.
A complete blood count may show eosinophilia in the early stage of invasion.
Ascaris antibody can be detected by indirect hemagglutination (IHA), immunofluorescence antibody (IFA), enzyme-linked immunosorbent assay (ELISA), or other methods. Serodiagnosis is helpful in extraintestinal ascariases, such as Loeffler`s syndrome.
Other methods that can help in the diagnosis of ascariasis include:
- Ultrasound: It can show the movement and shape of adult worms in the intestine or biliary tract.
- CT-scan: It can show calcified worms or masses of worms in the abdomen.
- X-rays: They can show intestinal obstruction or perforation caused by worms.
Detection of Parasite
Ascaris lumbricoides is a large roundworm that lives in the human intestine. It can cause abdominal pain, malnutrition, intestinal obstruction, and other complications. To diagnose ascariasis, the infection caused by this parasite, different methods can be used to detect the presence of the worm or its eggs in the body.
In some cases, the adult worm can be seen by the naked eye in the stool or sputum of the infected person. This usually happens when there is a heavy infection or when the worm migrates to other organs, such as the lungs or the bile ducts. However, this method is not very reliable as it depends on the chance of finding a worm in the fecal matter or mucus.
Other methods that can be used to detect adult worms are:
- Barium meal: This is a test that involves swallowing a liquid containing barium, a contrast agent that makes the digestive tract visible on X-rays. The barium meal can reveal the presence of an adult worm in the small intestine.
- Plain abdominal film: This is a simple X-ray of the abdomen that can show masses of worms in gas-filled loops of the bowel in patients with intestinal obstruction.
- Ultrasound: This is a test that uses sound waves to create images of internal organs. Ultrasound can detect pancreaticobiliary worms, which are worms that have migrated to the pancreas or the bile ducts. Ultrasound has a sensitivity of more than 50% for this purpose.
- Endoscopic retrograde cholangiopancreatography (ERCP): This is a test that involves inserting an endoscope (a thin tube with a camera and a light) through the mouth and into the duodenum (the first part of the small intestine). Then, a dye is injected into the bile ducts and pancreas to make them visible on X-rays. ERCP can detect pancreaticobiliary worms with a sensitivity of 90%.
In the early stages of infection, when the larvae migrate from the intestine to the lungs, they can cause Loeffler`s syndrome, which is characterized by cough, fever, wheezing, and eosinophilia (a high level of eosinophils, a type of white blood cell). To diagnose ascariasis at this stage, different methods can be used to detect the larvae in the body fluids:
- Sputum or gastric washings: These are samples of mucus or fluid from the lungs or stomach that can be examined under a microscope for the presence of larvae. This method is more often positive than negative in patients with Loeffler`s syndrome.
- Blood examination: A complete blood count (CBC) can show eosinophilia, which is a sign of an allergic reaction to the larvae. However, eosinophilia can also be caused by other conditions, so it is not specific for ascariasis.
- Chest X-ray: This is a test that uses X-rays to create images of the lungs. Chest X-ray can show patchy pulmonary infiltrates, which are areas of inflammation or fluid accumulation in the lungs caused by the larvae.
The most common and reliable method for diagnosing ascariasis is to examine the stool for eggs. The eggs are microscopic and have a characteristic shape and size. They can be detected by using different techniques:
- Saline emulsion: This is a simple technique that involves mixing a small amount of stool with saline (salt water) and placing a drop on a microscope slide. Both fertilized and unfertilized eggs can be seen under low magnification.
- Concentration technique: This is a technique that involves using chemicals or filters to separate and concentrate the eggs from other stool components. This technique increases the yield and sensitivity of microscopy, especially when there are few eggs present.
- Duodenal aspirates: This is a technique that involves inserting an endoscope into the duodenum and aspirating (sucking out) some bile. The bile can contain eggs that have been released by adult worms in the small intestine.
However, there are some limitations to these techniques:
- Eggs do not appear in stool until at least 40 days after infection, so they cannot be used to diagnose early or acute cases.
- Eggs may not be present in the stool if there are only male worms or if there is a low worm burden, so they cannot rule out infection.
- Eggs may be confused with other objects or artifacts in stool, such as pollen grains or plant cells, so they require careful examination and confirmation.
Microscopy is the standard method for diagnosing ascariasis by identifying Ascaris eggs in a stool sample. The eggs are oval, thick-shelled, and have a rough surface. They measure about 50–70 µm by 40–50 µm. Both fertilized and unfertilized eggs are usually present in the stool of infected individuals. However, only fertilized eggs are infective and can survive in the soil for long periods. Unfertilized eggs are often larger, more elongated, and have a clear space around the granular protoplasm.
To detect the eggs, a saline emulsion of stool is examined under a light microscope using a low-power objective (10x). Because eggs may be difficult to find in light infections, a concentration technique is recommended to increase the yield of diagnosis. There are various methods of concentration, such as flotation, sedimentation, or centrifugation. The choice of method depends on the availability of equipment, reagents, and expertise.
In some cases, Ascaris eggs may be demonstrable in the bile obtained by duodenal aspirates. This can be useful for diagnosing biliary ascariasis, which is a complication of intestinal ascariasis where the worms migrate into the bile ducts and cause obstruction or inflammation.
Microscopy is a simple, inexpensive, and reliable technique for diagnosing ascariasis. However, it requires specially trained laboratory personnel who can distinguish Ascaris eggs from other helminth eggs or artifacts that may resemble them. Moreover, microscopy cannot differentiate between species of Ascaris, such as A. lumbricoides and A. suum, which may have different epidemiological and clinical implications.
A blood examination is a useful method to detect the early stage of ascariasis when the larvae migrate through the lungs and cause eosinophilia. Eosinophils are a type of white blood cell that increases in response to parasitic infections. Ascariasis can elevate your eosinophils, but so can other types of health problems.
To test for eosinophilia, a complete blood count (CBC) can be performed on a blood sample collected from the patient. A normal eosinophil count is less than 500 cells per microliter of blood. A count of more than 500 cells per microliter is considered eosinophilia.
Eosinophilia is not specific to ascariasis and may be absent in chronic or heavy infections. Therefore, blood examination should be combined with other diagnostic methods, such as microscopy or serology, to confirm the diagnosis.
Serology is another type of blood examination that can detect antibodies against Ascaris lumbricoides. Antibodies are proteins produced by the immune system to fight foreign invaders, such as parasites. Serological tests can measure the level of antibodies in the blood using different techniques, such as indirect hemagglutination (IHA), immunofluorescence antibody (IFA), or enzyme-linked immunosorbent assay (ELISA).
Serological tests are helpful in extraintestinal ascariases, such as Loeffler`s syndrome, when the larvae cause pulmonary symptoms and no eggs are seen in feces. However, serology has some limitations, such as cross-reactivity with other parasites, low sensitivity and specificity, and inability to distinguish between current and past infections. Therefore, serology should also be used in conjunction with other diagnostic methods.
A blood examination is a valuable tool for the diagnosis of ascariasis, especially in the early stage of infection. However, it should not be used alone and should be interpreted with caution and clinical correlation.
Serological tests are methods that detect antibodies or antigens in the blood or other body fluids. They can be used to diagnose Ascaris lumbricoides infection by measuring the immune response of the host to the parasite.
Some of the serological tests that can be used for Ascaris lumbricoides are:
- Indirect hemagglutination (IHA): This test uses red blood cells coated with Ascaris antigen to agglutinate with Ascaris antibodies in the serum of the infected person. The degree of agglutination indicates the level of antibody present.
- Immunofluorescence antibody (IFA): This test uses fluorescent dye-labeled Ascaris antigen to bind with Ascaris antibodies in the serum of the infected person. The fluorescence intensity indicates the level of antibody present.
- Enzyme-linked immunosorbent assay (ELISA): This test uses enzyme-labeled Ascaris antigen or antibody to react with Ascaris antibody or antigen in the serum of the infected person. The enzyme activity produces a color change that indicates the level of antibody or antigen present.
Serological tests are helpful in extraintestinal ascariases, such as Loeffler`s syndrome, which is caused by the migration of Ascaris larvae through the lungs and causes respiratory symptoms. Serological tests can also be used to monitor the effectiveness of treatment and to assess the exposure and transmission of Ascaris lumbricoides in endemic areas.
However, serological tests have some limitations, such as:
- Cross-reactivity: Ascaris lumbricoides shares some antigens with other helminths, such as Toxocara canis and Trichinella spiralis, which can cause false-positive results.
- Persistence: Ascaris antibodies can persist for a long time after the infection is cleared, which can cause false-positive results or difficulty in distinguishing between current and past infections.
- Sensitivity: Serological tests may not detect low levels of antibodies or antigens, especially in light infections or early stages of infection.
- Specificity: Serological tests may not differentiate between different species of Ascaris, such as Ascaris lumbricoides and Ascaris suum, which can infect humans and pigs, respectively.
Therefore, serological tests should be used in conjunction with other diagnostic methods, such as microscopy, imaging, and molecular techniques, to confirm the diagnosis of Ascaris lumbricoides infection.
Besides the methods mentioned above, there are some other ways to diagnose Ascaris lumbricoides infection. These include:
- Ultrasound: This is a non-invasive imaging technique that uses sound waves to create pictures of the internal organs. Ultrasound can help detect worms in the liver, pancreas, bile ducts, or gallbladder. Ultrasound can also show the size and shape of the worms and their movement in the intestine.
- CT scan: This is another imaging technique that uses X-rays to create cross-sectional images of the body. A CT scan can help identify worms in the abdomen, especially if they cause complications such as intestinal obstruction, perforation, or abscess.
- X-rays: This is a simple and widely available imaging technique that uses electromagnetic radiation to produce images of the body. X-rays can show worms in the chest or abdomen, especially if they are calcified or cause obstruction. X-rays can also reveal masses of worms in gas-filled loops of the bowel in patients with intestinal obstruction.
- ERCP: This stands for endoscopic retrograde cholangiopancreatography, which is a procedure that uses an endoscope (a thin, flexible tube with a light and camera) and contrast dye to examine the bile ducts and pancreas. ERCP can help detect worms in the pancreaticobiliary system, which is the most common site of extraintestinal ascariasis. ERCP can also help remove the worms by using forceps or baskets.
These methods are usually reserved for cases where stool examination is negative or inconclusive or where complications are suspected or confirmed. They may also be used to monitor the response to treatment or to rule out other causes of symptoms.
The best way to prevent ascariasis is to avoid fecal contamination of soil, food, and water. The Ascaris egg is highly resistant and can survive for years in the environment. Therefore, the following measures are recommended :
- Improving sanitation and hygiene, especially in areas where open defecation is practiced or where human feces are used as fertilizer.
- Washing hands with soap and water before handling food and after using the toilet.
- Washing, peeling, and cooking vegetables and fruits before eating them, especially if they are grown in contaminated soil.
- Avoid eating raw or undercooked meat from pigs or other animals that may harbor Ascaris suum, a closely related parasite that can infect humans.
- Treating infected people, especially children, with anthelmintic drugs to reduce the transmission and burden of the disease.
- Mass drug administration (MDA) programs that provide periodic treatment to at-risk populations, such as school-age children, in endemic areas.
These prophylactic interventions can reduce the morbidity and mortality associated with ascariasis, as well as improve the nutritional status and cognitive development of affected children.
Ascariasis can be prevented by avoiding fecal contamination of soil, water, food, and hands. The following measures can help reduce the risk of infection :
- Proper disposal of human and animal feces.
- Composting of night soil before using it as fertilizer.
- Treatment of vegetables and other garden crops with water containing iodine 200 ppm for 15 minutes to kill the eggs and larvae of Ascaris and other helminths.
- Avoid eating raw or undercooked vegetables that may be contaminated with soil.
- Washing hands with soap and water before eating and after using the toilet.
- Improving personal hygiene and sanitation facilities.
- Treating infected persons, especially children, with anti-parasite medications to prevent transmission and complications.
- Mass drug administration (MDA) in endemic areas to reduce the worm burden and morbidity.
These prophylactic measures can help eliminate ascariasis as a public health problem and improve the quality of life of affected populations.
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