1. Batch 17 Remya Intestinal helminths

2. Learning Objectives: The objectives of this lecture are to introduce students to the basic concepts of parasitologyintroduce students to the basic concepts of parasitology introduce the various terms related to parasitologyintroduce the various terms related to parasitology highlight the significance of life cycle in the laboratory diagnosis of parasitic infectionshighlight the significance of life cycle in the laboratory diagnosis of parasitic infections

3. At the end of these lectures, students should be able to: restate the basic concepts of parasitology define of the various terms related to basic parasitology discuss briefly the life cycle and pathogenesis of medically important parasites apply the knowledge of the life cycle to the principles of laboratory diagnosis Learning Outcomes

4. Intestinal parasites Transmission is maintained by the release of life cycles in feces. Transmission routes: Food or water contaminated with infective eggs or larvae, or are picked up directly via contaminated fingers Some have larvae that can actively penetrate through the skin, migrating eventually to the intestine Others are acquired by eating animals or animal products containing infective stages.

5. The symptoms of intestinal infection range from very mild, through acute or chronic diarrheal conditions associated with parasite-related inflammation, to life-threatening diseases caused by spread of the parasites into other organs of the body. Mainly in communities in the tropics and subtropics - also affect people in developed countries. Gastrointestinal parasites are either protozoans or helminths which live in the human intestines.Gastrointestinal parasites are either protozoans or helminths which live in the human intestines.

6. Parasitic helminths / worms Cestodes (tapeworms) Trematodes (flukes) Nematodes

7. Parasitic helminths / worms

9. Soil-transmitted helminths fall into two distinct groups: Ascaris lumbricoides (large roundworm) and Trichuris trichiura (whipworm), in which infection occurs by swallowing the infective eggs.Ascaris lumbricoides (large roundworm) and Trichuris trichiura (whipworm), in which infection occurs by swallowing the infective eggs. Ancylostoma duodenale and Necator americanus (hookworms) and Strongyloides stercoralis, which infect by active skin penetration by infective larvae, that then undertake a systemic migration through the lungs to the intestine.Ancylostoma duodenale and Necator americanus (hookworms) and Strongyloides stercoralis, which infect by active skin penetration by infective larvae, that then undertake a systemic migration through the lungs to the intestine.

10. Roundworm An estimated 807-1,221 million people in the world are infected with Ascaris lumbricoides (sometimes called just "Ascaris"). Ascaris lumbricoides is the largest nematode parasitizing the human intestine. (Adult females: 20 to 35 cm; adult male: 15 to 30 cm.) Ascaris infection is one of the most common intestinal worm infections.

11. It is found in association with poor personal hygiene, poor sanitation, and in places where human feces are used as fertilizer. The geographic distributions of Ascaris are worldwide in areas with warm, moist climates and are widely overlapping. Infection occurs worldwide and is most common in tropical and subtropical areas where sanitation and hygiene are poor.

12. Small bowel with impacted worms Before surgery

13. Worms in the small bowel visible Intestineis opened transversely

14. The incision is being sutured Impacted worms removed

15. Life Cycle

16. Adult worms live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces. Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks, depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed, the larvae hatch, invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs. The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed. Upon reaching the small intestine, they develop into adult worms. Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

17. Clinical Features: Although infections may cause stunted growth, adult worms usually cause no acute symptoms. High worm burdens may cause abdominal pain and intestinal obstruction. During the lung phase of larval migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis - Loeffler’s syndrome). Migrating adult worms may cause symptomatic occlusion of the biliary tract or oral expulsion.

18. Laboratory Diagnosis Microscopic identification of eggs in the stool is the most common method for diagnosing intestinal ascariasis. Brine-floatation method Direct wet mount examination Larvae can be identified in sputum or gastric aspirate during the pulmonary migration phase (examine formalin-fixed organisms for morphology). Adult worms are occasionally passed in the stool or through the mouth or nose and are recognizable by their macroscopic characteristics.

19. Treatment Anthelminthic medications such as piperazine, albendazole and mebendazole, are the drugs of choice for treatment of Ascaris infections. Infections are generally treated for 1-3 days. The drugs are effective and appear to have few side effects.

20. Prevention & Control The best way to prevent ascariasis is to always: Avoid ingesting soil that may be contaminated with human feces, including where human fecal matter ("night soil") or wastewater is used to fertilize crops. Handwashing Wash, peel, or cook all raw vegetables and fruits before eating, particularly those that have been grown in soil that has been fertilized with manure. Transmission of infection to others can be prevented by Not defecating outdoors. Effective sewage disposal systems.

21. Hookworm Ancylostoma duodenale Necator americanus.

22. Infection is caused by the nematode parasites Necator americanus and Ancylostoma duodenale. Hookworm infections often occur in areas where human feces are used as fertilizer or where defecation onto soil happens. The geographic distributions of the hookworm species that are intestinal parasites in human,Ancylostoma duodenale and Necator americanus, are worldwide in areas with warm, moist climates and are widely overlapping. Necator americanus was widespread in the Southeastern United States until the early 20th century.

23. Life Cycle

24. Eggs are passed in the stool, and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil, and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective. These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host. Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years. Some A. duodenale larvae, following penetration of the host skin, can become dormant (in the intestine or muscle). In addition, infection by A. duodenale may probably also occur by the oral and transmammary route. N. americanus, however, requires a transpulmonary migration phase.

25. Laboratory Diagnosis Microscopic identification of eggs in the stool is the most common method for diagnosing hookworm infection. Direct wet mount examination of the specimen is adequate for detecting moderate to heavy infections. Cutaneous larval migrans is usually diagnosed clinically, as there are no serologic tests for zoonotic hookworm infections.

26. Larvae may be seen in stained tissue sections, but this procedure is usually not recommended as the parasites are usually not found in the visible track. Examination of the eggs cannot distinguish between N. americanus and A. duodenale. Larvae can be used to differentiate between N. americanus and A. duodenale, by rearing filariform larvae in a fecal smear on a moist filter paper strip for 5 to 7 days (Harada-Mori). Occasionally, it may be necessary to distinguish between the rhabditiform larvae (L2) of hookworms and those of Strongyloides stercoralis.

27. Disease High-intensity hookworm infections occur among both school-age children and adults. The most serious effects of hookworm infection are the development of anemia and protein deficiency caused by blood loss at the site of the intestinal attachment of the adult worms. When children are continuously infected by many worms, the loss of iron and protein can retard growth and mental development.

28. Iron deficiency anemia is the most common symptom of hookworm infection, and can be accompanied by cardiac complications. Gastrointestinal and nutritional/metabolic symptoms can also occur. In addition, local skin manifestations ('ground itch') can occur during penetration by the filariform (L3) larvae, and respiratory symptoms can be observed during pulmonary migration of the larvae.

29. Treatment Anthelminthic medications such as piperazine, albendazole and mebendazole. Iron supplements may also be prescribed if the infected person has anemia.

30. Prevention & Control The best way to avoid hookworm infection is not to walk barefoot in areas where hookworm is common and where there may be human fecal contamination of the soil. Also, avoid other skin contact with such soil and avoid ingesting it. Infection can also be prevented by not defecating outdoors and by effective sewage disposal systems.

31. Enterobius vermicularis Most commonly occurs among children, institutionalized persons, and household members of persons with pinworm infection

33. Eggs are deposited on perianal folds. Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area. Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting). Some small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs. Following ingestion of infective eggs, the larvae hatch in the small intestine and the adults establish themselves in the colon. The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months. Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area. The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions. Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.

34. Disease Itchy anal region. When the infection is heavy- secondary bacterial infection due to the irritation and scratching of the anal area. Teeth grinding and insomnia due to disturbed sleep. Infection of the female genital tract.

35. References http://www.cdc.gov/parasites/ http://dpd.cdc.gov/dpdx/HTML/Para_Health.h tmhttp://dpd.cdc.gov/dpdx/HTML/Para_Health.h tm Mims et al Medical Microbiology 3E