Intestinal Nematodes Student Notes PDF

GASTROINTESTINAL NEMATODES DR EMMANUEL IREK MEDICAL MICROBIOLOGIST ABUAD  Objectives Recognising the nematodes Identifying the disease entities they cause Management of the diseases  Classification of worms? Helminths (worm)...

GASTROINTESTINAL NEMATODES DR EMMANUEL IREK MEDICAL MICROBIOLOGIST ABUAD  Objectives Recognising the nematodes Identifying the disease entities they cause Management of the diseases  Classification of worms? Helminths (worm) Platyhelminths Flat worm/trematodes (flukes) Cestodes (Tapeworms) Nematodes (round worm) Intestinal !!!! Tissue filarial worms Guinea worm Zoonotic eruptive infections  Characteristics They are round!!! Nematodes are unsegmented helminths with bilateral symmetry have a fully functional digestive tract usually long and cylindrical vary from a few millimeters to over a meter long Tapered at both ends Those in humans have separate sexes Males usually smaller than females  Characteristics…2 In some cases, the eggs are infective when swallowed and other eggs will hatch in the soil, thus initiating infection by larval penetration of the human skin rather than egg ingestion Life cycle- Egg----Larval-----Adult usually four larval stages and then adult Direct- This means that once the egg is ingested and the internal larva has emerged, it develops within the intestinal tract into the adult form Indirect- there is extensive migration throughout the body prior to adult worm maturation and egg production Epidemiology  Epidemiology….2 World Health Organization (WHO) estimates suggest that over 3.5 billion people carry nematode infections Risks: HIV or other immunosuppressive ailments Poverty!! Poor sanitation Climatic Morbidity: blood loss, malnutrition, and intestinal blockage  Epidemiology….3 Parasitic factors for clinical effect strain of parasite and adaptation to a human host. number of parasites (parasite load). site(s) occupied in the body  Nematodes Enterobius vermicularis (pinworm) Trichuris trichiura (whipworm) Ascaris lumbricoides (human roundworm) Ancylostoma duodenale and Necator americanus (human hookworms) Strongyloides stercoralis (human threadworm) Trichinella spiralis  Ascaris lumbricoides A. lumbricoides was confused for the common earthworm Morphology females measure 20 to 35 cm long, and males are 15 to 31 cm long  6. From the right heart they are carried into the pulmonary circulation (10days) 7. Larvae break into the alveoli, migrate via the bronchi 1. The worms then until they reach mature and mate in the trachea and the small intestine, pharynx, and with the eventual then are production of eggs, swallowed which are passed in the stool 5.the eggs hatch in the stomach and duodenum, where the larvae actively penetrate the intestinal wall—undergoing  Ascaris lumbricoides….2 1. The worms then mature and mate in the small intestine, with the eventual production of eggs, which are passed in the stool 5. the eggs hatch in the stomach and duodenum, where the larvae actively penetrate the intestinal wall—undergoing molting; they are then carried to the right heart 6. From the right heart they are carried into the pulmonary circulation (10days) 7. larvae break into the alveoli, migrate via the bronchi until they reach the trachea and pharynx, and then are swallowed  Ascaris lumbricoides….3 The entire developmental process from egg ingestion to egg passage from the adult female takes from 8 to 12 weeks. During her life span, she may deposit a total of 60 million or more eggs. Often only female worms are recovered from the intestine. Fertilized eggs become infective within 2 weeks if they are in moist, warm soil, where they may remain viable for months or even years Ascaris lumbricoides….4  Ascaris lumbricoides….5 Pathology-Ascariasis the host immune response- (asymptomatism), effects of larval migration, mechanical effects of the adult worms, and nutritional deficiencies due to the presence of the adult worms Ascaris Pnemonitis transient pulmonary infiltrates associated with peripheral eosinophilia -Loeffler’s syndrome Asthma and urticaria may continue during the intestinal phase of ascariasis Rarely hepatic ascariasis Worm migration may occur as a result of stimuli such as fever (usually over 38.9°C), the use of general anesthesia,or steroids. This migration may result in intestinal blockage bowel perforation and peritonitis, anal passage of worms, vomiting, and abdominal pain. Ascaris lumbricoides….6  Ascaris lumbricoides….7 Diagnosis Larval migration phase- sputum or gastric washings Intestinal phase- eggs (iodine/Saline wet mount) or adult worms in stool Radiology- trolley-car lines bowel obstruction, biliary or pancreatic duct blockage, appendicitis, or peritonitis Acute abdomen  Ascaris lumbricoides….8 Treatment- Adult worm killers Albendazole or mebendazole -drug of choice ivermectin and pyrantel pamoate (pregnancy) Levimasole Prevention Sanitation Faeces as fertilizers Complications Low weight Anaemia Prognosis Good but reinfection  Enterobius vermicularis Oxyuris vermicularis AKA Pinworm more prevalent in the cool and temperate zones High prevalence in children Morphology: Female pinworms (about 10 millimeters in length) have a slender, pointed PIN posterior end. Males are approximately 3 millimeters in length and have a curved posterior end  Enterobius vermicularis…2 After fertilization of the female worms, the males usually die and may be passed out in the stool the female migrates down the colon and out of the anus, where they deposit eggs on the perianal and perineal skin Vaginal migration? eggs are fully embryonated and infective within a few hours transmission is often attributed to the ingestion of infective eggs by nail biting and inadequate hand washing  Enterobius vermicularis…3 Pathology: Enterobiasis Asymptomatic PRURITUS via migration of the female worms from the anus onto the perianal skin before egg deposition ……. Hypersensitivity reaction of the eggs Women and children are more predisposed to symptomatism +/- eosinophilia nervousness, insomnia, nightmares, and convulsions unexplained eosinophilic enterocolitis  Enterobius vermicularis…4 Diagnosis May be clinical; anal itching, irritability and insomnia Confirmed laboratory by demonstrating the presence of eggs or adult worms perianal and perineal skin with cellulose tape (Scotch tape) 4X overnight The tape is transferred to a glass slide and examined under the microscope for the presence of eggs or adult worms Stool sampling rarely Treatment albendazole or mebendazole ivermectin or pyrantel pamoate Sanitation and good hygiene  Trichuris trichiura Whipworm Direct life cycle Morphology: Adult female whipworms are approximately 30–50 millimeters in length; adult male worms are smaller 360° coil at the caudal extremity Adult whipworms inhabit the colon, where male and female worms mate Usually seen with Ascaris spp. 10-14days  Trichuris trichiura……2 Pathology- Trichuriasis Asymptomatic The head portion of the worm is very thin and is embedded in the mucosa, while the posterior end is much thicker and lies free in the lumen of the large intestine Punctate haemorrhages  Trichuris trichiura……3 Intestinal manifestations-worm burden, the length of the infection, and the age and overall health status of the host Lower abdominal pain, distention, and diarrhea chronic dysentery-like syndrome if they have a massive infestation leading to anemia and growth retardation. Severe infection may lead to profuse bloody diarrhea, cramps, tenesmus, urgency, and rectal prolapse the appendix, causing appendicitis Hypochromic anaemia-blood loss  Trichuris trichiura……4 Diagnosis Eggs in the stool The eggs are barrel shaped with clear, mucoid-appearing polar plugs eosinophils and Charcot-Leyden crystals are present in the stool in patients with dysentery +/- peripheral eosinophilia Treatment albendazole or mebendazole  Hookworms Ancylostoma duodenale, Necator americanus, and Ancylostoma ceylanicum An estimated 700 million to 900 million people worldwide are infected with hookworm (mostly Ancylostoma duodenale), 0.2% of whom suffer from severe anemia Morphology Adult fem males measure 7 to 11 mm long The adult Ancylostoma worm tends to be larger than the Necator worm 5-7days 24hrs 8 months  Hookworms………..2 Proteolytic enzymes for penetration Optimal pH Life cycle similar to Ascaris when in the intestines This worm attaches to the intestine and feeds on the blood from the capillary-rich lamina propria of the bowel  Hookworms………..3 Pathology----Hookworm infection Worm burden predicts events Skin penetration Ground itch----may become infected (erythema and intense pruritus ) Pneumonitis Intestinal phase Necrosis of tissue and blood ingestion Necator---0.03ml/day; Ancylostoma---0.15-0.2ml/day Clinically manifested as fatigue, nausea, vomiting, abdominal pain, diarrhea with black to red stools (depending on the level of blood loss), weakness, and pallor In chronic infections- iron deficiency anemia (microcytic, hypochromic)  Hookworms………..4 Diagnosis Eggs in the stool---non-distinguishable amidst species Treatment mebendazole, pyrantel pamoate, and albendazole Iron replacement Mangement of co-morbidities  Strongyloides stercoralis Adult females is about 2 millimeters long Can maintain a nonparasitic cycle in the soil S. stercoralis has a unique evolutionary adaptation that can greatly enhance its reproductive success S. stercoralis is most commonly found in warm areas but can survive in colder climates Partheogenesis????  Strongyloides stercoralis..2 Under ideal conditions of moisture and temperature in the external environment, rhabditiform larvae hatch, and quickly transform into infective filariform larvae homogonic route or heterogonic route the majority of eggs hatch into rhabditiform larvae while still in the intestinal lumen Some of the rhabditiform larvae may transform into filariform larvae while still within the intestinal lumen invade the mucosa or perianal skin, resulting in a cycle of chronic reinfection. More in immunosuppressed px fatal hyperinfection syndrome  Strongyloides stercoralis..3 Pathology- Strongyloidiasis Point of entry- skin irritation and pruritus in the form of low- grade chronic dermatitis , Larva currens Vs ground itch The intestinal manifestations vary from few to no symptoms in light infections to severe necrotizing bowel disease in heavy infections DDx PUD, crohn’s (eosinophilic granulomatous enterocolitis) (severe diarrhea, abdominal pain, gastrointestinal bleeding, nausea, vomiting) Loeffler’s pneumonia  Strongyloides stercoralis..4 Disseminated Strongyloides infection---organic Autoinfection Hyperinfection----Immunity problem; steroids and human T- lymphotropic virus type 1 (HTLV-1) infection Gram-negative sepsis  Strongyloides stercoralis..5 chronic disease These symptoms include intermittent vomiting, diarrhea, constipation, and loud gurgling GI noises, Anal pruritus, urticaria and larva currens, rashes, recurrent asthma, and nephrotic syndrome have also been associated with.  Strongyloides stercoralis..6 Diagnosis Rhabditiform larva in stool Eggs could be seen in profuse diarrhoea Peripheral Eosinophilia EnteroTest capsule Molecular Serology  Strongyloides stercoralis..7 Treatment Ivermectin Thiabendazole Mebendazole Albendazole  Other intestinal nematodes Trichinella spiralis Acquired by eating improperly cooked meat infected with the larval stage Mating of adult worms occur in the intestine post-maturation female worms release live larvae larvae penetrate the intestine, circulate in the blood, and eventually encyst in muscle tissue Intestinal symptoms: diarrhea, abdominal pain, and nausea Muscular encystation is the hallmark of Trichinellosis/Trichinosis Tissue nematode!!!!  Trichostrongylus spp. …2 Trichostrongylus spp. Rare in man Similar to hookworm in structure (but nil jaws) and intestinal habitat (nil lung migration) Live embedded in the mucosa of the small intestine Infection in humans is acquired through ingestion of the infective larvae contaminating plant material Clinical effect----Worm burden and intestinal damage  Trichostrongylus spp. ….3 Symptoms: Epigastric pain, diarrhea, anorexia, nausea, dizziness, and generalized fatigue or malaise; eosinophilia is usually present Cholecystitis Dx-Egg In stool Tx- pyrantel pamoate, mebendazole, and albendazole  THE END Thank you for listening……………………… Any questions???????????????????????????????