MBBS B3 Ascaris lumbricoides & Ancylostoma duodenale PDF

Intestinal helminths infections Ascaris lumbricoides Ancylostoma duodenale Prepared by: Dr. Helen Tang Hooi Chia Department of Microbiology (Faculty of Medicine) At the end of the lecture, you should be able to: ❑ Describe the morphology, habitat and general characteristics ❑ Describe the hosts,...

Intestinal helminths infections Ascaris lumbricoides Ancylostoma duodenale Prepared by: Dr. Helen Tang Hooi Chia Department of Microbiology (Faculty of Medicine) At the end of the lecture, you should be able to: ❑ Describe the morphology, habitat and general characteristics ❑ Describe the hosts, infective forms, routes of entry and modes of transmission ❑ Describe the pathogenesis, clinical features, complications and laboratory diagnosis of the Infections ❑ Describe the treatment and preventive measures Manipal University College Malaysia 2 Intestinal Helminthic Infections 3 Intestinal Helminthic Infections ❑ Parasitic helminths: • Nematodes ( Ascaris lumbricoides, Ancylostoma duodenale, Strongyloides stercoralis, Enterobius vermicularis) • Trematodes ( Clonorchis sinensis) • Cestodes ( Taenia solium, Taenia saginata, Echinococcus granulosus) Nematodes Manipal University College Malaysia Trematodes Cestodes 4 Ascaris lumbricoides Ancylostoma duodenale General characteristics ❑ Intestinal nematodes ❑ Oviparous ❑ 6 developmental stages ❑ Female worm is larger in size ❑ Bilaterally symmetrical ❑ Contain various organs ❑ Diecious (bisexual) male and female worms are different ❑ Complete life cycle in one host (man) Manipal University College Malaysia 5 6 Ascaris lumbricoides Ascaris lumbricoides Common name: roundworm Cause ascariasis Habitat ❑ Small Intestinal Morphology Three forms: 1. Adult 2. Larvae 3. Eggs Manipal University College Malaysia 7 Ascaris lumbricoides 1. Adult • Cylindrical • Tapering ends • Large (measures 15-31 cm) Females: 20–50 cm long Males: 15–30 cm long Adult females are larger than adult male worms (length of ruler = 16 cm) Manipal University College Malaysia 8 Ascaris lumbricoides 2. Larvae Four stages (L1-L4) 3. Eggs Two types: Fertilised eggs ❑ _______________ Unionised eggs ❑ ________________ • Round to ovoid • Elongated • Measuring 60–75 μm in length • More elliptical with a thinner shell • Contain large, unsegmented ovum • Measuring up to 85-95 μm • Outer layer is coarsely mamillated ( protective layer) • Contains an unsegmented, small atrophied ovum • Floats in saturated salt solution • Does not develop into the infective stage Manipal University College Malaysia 9 10 Ascaris lumbricoides (Life Cycle) ❑ Involves only one host ❑ Embryonated eggs contain the L2 larvae Mode of transmission ❑ Faecal-oral transmission of eggs containing infective larvae ❑ Ingestion of embryonated eggs from the contaminated soil, food and water Manipal University College Malaysia 11 • The adult worms live in the small intestine • The female worm produces both fertilized and unfertilized eggs which are passed out in faeces • In the soil, the fertilized egg undergoes development to the infective stage • Human acquires infection via ingestion of the infective eggs • In the intestine, the eggs hatch into larvae • The larvae penetrate the mucosa of the small intestine and enter the portal circulation and are carried to the heart and lungs (migration phase) • The L4 larvae in the lungs migrate up to reach the pharynx and finally are swallowed to re-enter the intestine, where they develop into adults 12 Ascaris lumbricoides (Pathogenesis & Clinical Features) ❑ Infections by small numbers of worms may remain asymptomatic ❑ Larger numbers of worms can cause significant health problems ❑ Pathogenesis caused by Ascaris infection is attributed to: i. The host immune response ii. Migration of larva iii. Mechanical obstruction by the adult worms iv. Nutritional deficiencies due to the presence of adult worms ❑ The incubation period is about 60–70 days Manipal University College Malaysia 13 Ascaris lumbricoides (Pathogenesis & Clinical Features) ❑ Pulmonary Phase • Results from migrating larvae in the lungs • Provoke an immune-mediated hypersensitivity response • Symptoms are observed in the second week after the ingestion of eggs • Characteristics: Non-productive cough Chest discomfort Fever • Eosinophilic pneumonia (Loeffler’s syndrome) In severe cases, patients develop dyspnea and transient patchy infiltrates seen in the chest XManipal University College Malaysia 14 ray along with transient peripheral eosinophilia Ascaris lumbricoides (Pathogenesis & Clinical Features) ❑ Intestinal Phase • Due the effect of adult worm in the intestine • Asymptomatic • Malnutrition and growth retardation • Intestinal complications • Extraintestinal complications • Allergic manifestation Manipal University College Malaysia 15 Ascaris lumbricoides (Laboratory Diagnosis) Detection of parasites ❑ Microscopic examination • Egg detection • Both fertilized and unfertilized eggs can be detected by stool examination by saline and iodine wet mount ❑ Gross examination • Adult Worm Detection • May be detected in stool or sputum • Barium meal X-ray of the GIT may demonstrate the adult worms in the intestine • Ultrasound to detect adult worms in extraintestinal sites Manipal University College Malaysia 16 Ascaris lumbricoides (Laboratory Diagnosis) Molecular method ❑ PCR ❑ Multiplex PCR ❑ Real-time PCR Manipal University College Malaysia 17 Ascaris lumbricoides (Treatment) ❑ Antiparasitic drugs • Albendazole (400 mg once) or mebendazole (100 g twice daily for 3 days or 500 mg once) • Ivermectin (150–200 mg/kg once) and nitazoxanide • In pregnancy, pyrantel pamoate is safe ❑ Symptomatic treatment • Partial intestinal obstruction: Nasogastric suction Intravenous (IV) fluid administration • Complete obstruction and its severe complications like intussusception Immediate surgical intervention Manipal University College Malaysia 18 Ascaris lumbricoides (Preventive Measures) ❑ Avoidance the use of human faeces as fertilizer ❑ Wash fruits and vegetables before consumption ❑ Maintenance of sanitary conditions ❑ Good personal hygiene Manipal University College Malaysia 19 Ancylostoma duodenale 20 Ancylostoma duodenale (General characteristics) ❑ Ancylostoma duodenale (Greek ankylos—hooked; stoma—mouth) ❑ Common name: __________________ ❑ Cause hookworm infection ❑ The important causes of iron deficiency anaemia ❑ Only two species are human pathogens; cause intestinal disease Ancylostoma duodenale Necator americanus ❑ Much smaller than the large roundworm, Ascaris lumbricoides ❑ Males and young adults are commonly affected Manipal University College Malaysia ❑ Iron deficiency anaemia more severe in children and pregnant women 21 Ancylostoma duodenale Habitat: Small intestine Morphology Three forms: 1. Adult 2. Larvae 3. Eggs Manipal University College Malaysia 22 Ancylostoma duodenale 1. Adult ❑ Cylindrical in shape ❑ Well-developed buccal capsule with sharp teeth ❑ Has a bent in the anterior end ❑ Males are slightly smaller ❑ Have a broadened posterior end copulatory bursa used to mate with females ❑ Females release > 10,000 eggs per day ❑ Smaller (measures 7-13 mm) Females: 10–13 mm long Males: 8–11 mm long Manipal University College Malaysia 23 Ancylostoma duodenale 2. Larvae ❑ Four stages (L1-L4) ❑ 2 types of larva • L1 larva: ____________ larva Vhabidiform Filariform(L3) hookworm larva Alan • L3 larva: ____________larva form - Close-up of the posterior end of a filariform (L3) larva Close-up of the anterior end showing cutting teeth 3. Eggs ❑ Oval ❑ Measure 60 × 40 µm, surrounded by a thin eggshell ❑ Ovum (embryo) is ___________; comprises 4-32 blastomeres segmented ❑ There is a clear space between the segmented ovum and eggshell Egg with four blastomeres Manipal University College Malaysia 24 Ancylostoma duodenale (Life Cycle) ❑ Involves only one host Phantom ↳ ❑ The _________________ is the infective form larvaa Mode of transmission ❑ Through penetration of the skin by the L3 larva; during walking barefoot in dampen soil Manipal University College Malaysia 25 • Eggs released in faeces are immature, which become embryonated in moist, shady, warm soil • L1 (rhabditiform) larvae hatch out from eggs and then molt twice to develop into L3 larvae • L3 larvae remain viable in the soil for several weeks (infective form) • The larvae penetrate the skin and are carried through the blood vessels to the lungs • They enter into the alveolar space and migrate up to pharynx and finally by swallowing of sputum, they enter GIT • The L3 larvae molt twice in small intestine to develop into adult worms, which attach to the intestinal mucosa by their teeth in the buccal capsule • Following fertilization, female worms lay eggs, which are excreted in the faeces 26 27 Ancylostoma duodenale (Pathogenesis & Clinical Features) ❑ Able to suck blood from the intestinal vessels: • Attaching and making cuts in the intestinal wall followed by sucking the blood through contraction of their muscular oesophagus • Secreting ______________ hydrolytic enzymes • Releasing ______________ anticoagulants ❑ Pathogenicity involves skin, lungs, and small intestine ❑ There are 3 phases: invasion, migration, and establishment in the intestine ❑ Effect due to migrating larvae or adult worms in the intestine Manipal University College Malaysia 28 Ancylostoma duodenale (Pathogenesis & Clinical Features) 1. Effect due to migrating larvae Cutaneous lesions • May provoke pruritic maculopapular dermatitis and rashes • Serpiginous tracks may be formed Mild transient pneumonitis • The pulmonary symptoms are usually mild and transient • Dry cough, sore throat, wheezing and slight fever Manipal University College Malaysia 29 Ancylostoma duodenale (Pathogenesis & Clinical Features) 2. Effect due to adult worm in the intestine Clinical spectrum produced depends upon the __________ mom load ❑ Asymptomatic ❑ Early intestinal phase ❑ Late intestinal phase ❑ Wakana disease Manipal University College Malaysia 30 Ancylostoma duodenale (Pathogenesis & Clinical Features) ❑ Asymptomatic • Most infections are asymptomatic ❑ Early intestinal phase: • Epigastric pain • Inflammatory diarrhoea • Other abdominal symptoms + eosinophilia ❑ Late intestinal phase: • Iron deficiency anaemia and protein energy malnutrition resulting from blood loss • Other features: weakness and shortness of breath Manipal University College Malaysia 31 Ancylostoma duodenale (Pathogenesis & Clinical Features) ❑ Wakana disease: • When L3 larvae are ingested by the oral route • Either migrate to pharynx or develop into adult worms in the intestine • Both GI and pulmonary symptoms are observed ➢ Nausea ➢ Vomiting ➢ Pharyngeal irritation ➢ Cough ➢ Dyspnea ➢ Hoarseness Manipal University College Malaysia 32 Ancylostoma duodenale (Laboratory Diagnosis) 1. Microscopic examination • Diagnosis is established by finding characteristic eggs in the faeces • Egg counting The number of eggs per gram of stool can be counted to estimate the disease burden in the individual as well as in the community 2. Stool culture The freshly passed stool samples can be cultured so that the eggs hatch out to develop to L3 stage filariform larvae in 5–7 days, which can differentiate A. duodenale from N. americanus Manipal University College Malaysia 33 Ancylostoma duodenale (Laboratory Diagnosis) 3. Molecular method ❑ PCR ❑ Real-time PCR ❑ Multiplex PCR Advantages: • Species-specific • Can differentiate between Ancylostoma and Necator • Can detect as low as one copy per 200 mg of stool Manipal University College Malaysia 34 Ascaris lumbricoides (Treatment) ❑ Antiparasitic drugs • Albendazole (400 mg once) or mebendazole (500 mg once) • Pyrantel pamoate (11mg/kg for three days) ❑ Symptomatic treatment • Mild iron-deficiency anaemia: oral iron and folic acid • Severe hookworm disease: Nutritional support and oral or parenteral iron replacement Manipal University College Malaysia 35 Ascaris lumbricoides (Preventive Measures) General preventive measures include: ❑ Improved personal hygiene ❑ Proper disposal of faeces ❑ Improved nutrition with dietary iron ❑ Treatment of infected persons Manipal University College Malaysia 36 37 38