Ascaris LumbricoidesThis review assignment highlights my findings about Ascaris Lumbricoides. As we studied in parasitology class, Ascariasis is the largest intestinal roundworm that parasitizes the gastrointestinal tract and it is the third most common helminthis infection. According to WHO, in the year 2003, prevalence of ascariasis is 1222 millions worldwide with 84 million cases in USA. Also, we have learned that humans are the definitive host for Ascaris Lumbricoids.
According to Celia Holland, the author of “Ascaris: The Neglected Parasite”, the Ascarisis females weight about 4 to 7 grams and measure 20 to 30 cm long. But males are smaller. “The worms tend to inhibit the Jejunum, the middle section of the small intestine, feeding on ingesta and swimming against the flow to maintain their position”(Holland p.157 ). According to this book, the life cycle begins with both mature females and males mate in order to enable production of the fertile eggs. The “eggs are egested into the environment with the host’s feces”(Page 157). According to the author, the best temperature for these worms is about 28 to 32 centigrade for embryonation. They have a life span of 10 months to 2 years and then are passed in the stool. Each female worn produce about 200,000 fertilized ova per day. The infection happens only with female worms, and those infertile eggs that cannot develop into the infectious stage are produces. “With male only worm infections, no eggs are formed”(Standford.edu 2018). The embryos develop into infective second stage larvae in the environment in two to four weeks depending on the environment condition as mentioned earlier. When ingested by humans, the ova are going to hatch in the small intestine and will release larvae, which will penetrate the intestine wall and migrate hematogenously or via lymphatics to the heart and lungs. Sometimes, “Larvae migrate to sites other than the lungs, including the kidnery or brain”(Jessika Lora and Peter F. Weller 2005). By four days after ingestion, larvae will reach the lungs. Within the alveoli of the lungs, the larvae mature over a period of approximately 10 days, then pass up via bronchi and the trachea, and are subsequently swallowed. Once back in the intestine, they mature into adult worms. Although the majority of worms are found in the jejunum, they may be found anywhere from the esophagus to the rectum. After approximately two to three months, the females will begin to produce ova which, when excreted, complete the cycle. It was very interesting to know that adult worms do not multiply in the human host, in fact, the number of adult worms per infected person relates to the number of continued exposure to infectious eggs over time.
When the symptoms happen, they either related to the larva migration stage or to the adult worm intestinal stage. The symptoms can be pulmonary and hypersensitivity manifestations that is associated with the pneumonitis that happens two weeks after the ingestions of the eggs. The hypersensitivity happens the end of the period of migration through the lungs. Intestinal symptoms, as we also learned about it in class, result in abdominal pain, nausea and diarrhea. According to Stanford University, intestinal obstruction, “A mass of worms can obstruct the bowel lumen in heavy Ascaris infection, leading to acute intestinal obstruction”. Hepatobiliary and pancreatic symptoms are related to “Symptoms related to the migration of adult worms into the biliary tree can cause abdominal pain, biliary colic, acalculous cholecystitis, ascending cholangitis, obstructive jaundice, or bile duct perforation with peritonitis. Strictures of the biliary tree may occur”(al-Karawi, M, Sanai, FM, Yasawy, MI, Mohammed, AE 1999).
Treatment consists of choosing the right medications, doctors follow up or therapy. The drugs that can be used in treatment of Ascariasis are Mebendazole that helps with GI discomfort and headache, Albendazole which is the same as Mebendazole, and Levamisole that 96 percent is effective. The patients should be reevaluated at two to three months to ensure that no eggs are detectable. Because reinfection can happen frequently. Prevention, can be somehow hard since the Ascaris parasites are abundant in soil. However, good sanitation is required. Using the above medications can help young children to reduce the reinfection.
“Chapter 7.” Ascaris: the Neglected Parasite, by Celia V. Holland, Elsevier/Academic Press, 2013.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3693114/pdf/CRIM.MEDICINE2013-579464.pdfhttps://web.stanford.edu/group/parasites/ParaSites2005/Ascaris/JLora_ParaSite.htmal-Karawi, M, Sanai, FM, Yasawy, MI, Mohammed, AE. Biliary strictures and cholangitis
secondary to ascariasis: endoscopic management. Gastrointest Endosc 1999; 50:695.