Intestinal Nematodes Module 07.16 PDF

Intestinal Nematodes Module 07: GI and Nutritional Pathologies Alvin Christoper S. Chu, MD | Asynchronous TABLE OF CONTENTS I. OVERVIEW OF NEMATODES..............................................................1 II. ENTEROBIUS VERMICULARIS........................................................... 1...

Intestinal Nematodes Module 07: GI and Nutritional Pathologies Alvin Christoper S. Chu, MD | Asynchronous TABLE OF CONTENTS I. OVERVIEW OF NEMATODES..............................................................1 II. ENTEROBIUS VERMICULARIS........................................................... 1 A. LIFE CYCLE.................................................................................... 1 B. CLINICAL MANIFESTATIONS..........................................................2 C. DIAGNOSIS................................................................................... 2 D. TREATMENT................................................................................. 3 E. PREVENTION................................................................................ 3 III. CAPILLARIA PHILIPPINENSIS........................................................... 3 A. LIFE CYCLE.................................................................................... 4 B. CLINICAL MANIFESTATIONS..........................................................4 C. DIAGNOSIS................................................................................... 4 D. TREATMENT................................................................................. 4 E. PREVENTION................................................................................ 5 IV. STRONGYLOIDES STERCORALIS....................................................... 5 A. LIFE CYCLE.................................................................................... 6 B. CLINICAL MANIFESTATIONS..........................................................7 C. DIAGNOSIS................................................................................... 7 D. TREATMENT................................................................................. 8 E. PREVENTION................................................................................ 8 QUESTIONS......................................................................................... 9 ANSWER KEY.......................................................................................9 RATIONALE..........................................................................................9 Mode of infection: ○ Direct ▸ Parasite release embryonated eggs into host ○ Modified direct ▸ Parasite releases eggs that require exposure to environment in order to be infective ○ Skin penetration ▸ Direct invasion of parasite—usually larval stage II. ENTEROBIUS VERMICULARIS Figure 1. Enterobius vermicularis male and female adult LEARNING OBJECTIVES 1. To be familiar with the parasite biology of the nematodes discussed 2. To be familiar with the epidemiology of the nematodes discussed 3. To be familiar with the common diagnostic methods to detect infection with the nematodes 4. To be familiar with the management of, and prevention of infections the intestinal nematodes I. OVERVIEW OF NEMATODES Take Note! This lecture is considered as Part 2 of Intestinal Nematodes lecture ○ As stated in Canvas, “Part 1 of Intestinal Nematodes was already lectured as soil transmitted nematodes in BP2” The focus of this lecture are medically important nematodes (Enterobius, Capillaria, and Strongyloides) Morphology: ○ Generally cylindrical ○ Tapered at both ends ○ Non-segmented ▸ No repeating segments with complete reproductive parts or organ systems within them ▸ Different from metamerism ○ Bilaterally symmetrical ○ Covered by cuticle ○ Complete digestive tract ○ No circulatory system Characterized based on: ○ Sensory organs ▸ E.g., phasmids ○ Muscle arrangement Life cycle: ○ Egg, larva, adult ○ Larva ▸ Rhabditiform (non infective or feeding) ▸ Filariform (infective or non-feeding) YL6:07.16 Figure 2. Cephalic alae (a), esophageal bulb (b), copulatory spicule of male (c), and pointed tale of female Enterobius vermicularis Pinworm, threadworm, seatworm ○ Can cause confusion as the term “threadworm” may also refer to Strongyloides in some countries Epidemiology: ○ Worldwide distribution ○ One of the most common helminthic infection—particularly in children ○ Commonly seen in institutional settings (e.g., crowding) ○ Humans are the only known species to harbor and transfer this parasite Phylum: Nematoda ○ Family: Oxyuridae ○ Genus: Enterobius Adult ○ Usually present with cephalic alae ▸ An expansion of the mouthpart can also be seen TG01: Alvarez, Balayan, Bantayan, Cosico, Escalante, Majarais, Manlutac, Ozaeta, Rivera, Roque, Santiago CG13: Abad Santos, Ahalajal, Alba, Bernardo, Binobo, Cai, Dy, Gamboa, Pacis, Rejuso, Tan 1 ○ Esophageal bulb ○ Male: 2.5 mm long and 0.1-0.2 mm wide ▸ Curved tail with copulatory spicule ▸ Generally smaller than females, seen in majority of helminths ○ Female: 8-13 mm long and 0.3-0.5 mm wide ▸ Pointed tail ○ Lifespan of approximately 1-2 months Larva ○ Approximately 140-150 μm in length and 10 μm in width ○ Has an esophageal bulb but no cephalic ala Egg ○ Approximately 50-60 μm in length and 20-30 μm in width ○ Elongated, oval, plano-convex (“D-Shaped”) ▸ One side is more flat while the other is more convex ○ Thick, translucent shell ○ Eggs are fully embryonated within a few hours (4-6 hours) after oviposition ▸ Oviposition: When an adult female deposits her eggs ○ Can survive in the environment for 2-3 weeks in optimal conditions ▸ Longest in high humidity and moderate temperature ○ Eggs may also survive in dry dust ▸ In some cases, people were infected by inhaling dry dust A. LIFE CYCLE Infection most commonly occurs through the oro-fecal route ○ Infective stage: embryonated eggs Larva are released in the stomach and small intestines Mature adults reside in the ileo-cecal region ○ Minute ulcerations may develop at the site of attachment of the adult worms to the cecal and/or appendiceal mucosa Adult females migrate to the perianal area and deposit eggs Diagnostic stage: ova/egg Autoinfection (retroinfection) ○ Type of autoinfection where the embryonated eggs in the perianal area hatch and travel back into the intestines ○ They don’t go through the normal cycle where they need to be ingested into the system of the host ○ After, some return to the intestines ○ However, most adult females die after oviposition Once the eggs are deposited, these will cause perianal itching and irritation ○ Individual has a tendency to scratch the pruritic area ○ If eggs are deposited in the area, scratching will transfer the eggs to the individual’s hand ○ If the person’s hand is placed into their mouth, they would ingest the infective embryonated eggs B. CLINICAL MANIFESTATIONS Pruritus ani (nocturnal) ○ Most common clinical manifestation Insomnia and restlessness ○ Due to females depositing eggs around 4 hours after the infected individual goes to sleep In children, they may show loss of appetite, loss of weight, irritability, emotional instability, and enuresis There is usually no eosinophilia or anemia Ulcers and submucosal abscesses ○ Formed in the ileocecal region or appendix due to the attachment of the parasites in those areas Ectopic deposition of eggs (e.g., vulvitis, peritonitis, etc.) ○ When the adult female deposits the eggs in structures near the perianal area Aberrant infections, wherein the parasite travels to different parts of the body, may occur in liver, ovary, kidney, spleen, lung, and appendix C. DIAGNOSIS MICROSCOPIC IDENTIFICATION OF OVA Main method for diagnosis Scotch Tape Swab Figure 4. Enterobius vermicularis egg Figure 5. Scotch tape swab (left) and Swube tube (right) Figure 5 Figure 3. Enterobius vermicularis life cycle Life cycle begins with the ingestion of the embryonated egg Once the egg is ingested, it goes into the stomach where the larvae are released ○ Some are released in the small intestine Larva travel to the ileocecal region where they mature into adults Mature adults may cause minute ulcerations in the site of attachment like the ileocecal region or even in the appendix Adult females migrate from the intestines to the perianal area to deposit their eggs YL6:07.16 Intestinal Nematodes Steps: 1. Affix the end of the tape near one end of the slide 2. Loop or fold the rest of the tape over the end of the slide so the adhesive surface is exposed or is outside 3. After which, touch the adhesive surface to the perianal region several times 4. Fold back the tape and affix it on the slide (smooth down the tape across the surface of the slide) In summary: use the folded side of the tape to touch the perianal region and then close it back 2 ○ There are other tests that use the same concept as this swab called Swube tube ▸ There is a paddle that also has adhesive material ▸ Similarly, touch the paddle to the perianal region ▸ Appears more “formal” than Scotch tape swab ○ There are cases wherein there is ectopic deposition of eggs ▸ E.g., along lower female genital tract, adult worms may be seen in anorectal or vaginal exams or in urine or vaginal smears Stool Examination ○ Not usually done because eggs in stool are less frequently seen ▸ Still possible and may still be done but not a method of choice due to lower yield as compared to Scotch tape swab IDENTIFICATION OF ADULT WORM Adult worms can also be identified They can be seen in the following examples: ○ In tissues sent for routine processing ○ By directly seeing the adult worms in areas they are oviposited Figure 6. Enterobius vermicularis in tissue cross-sections (H&E) Take Note! The lecturer seemed to be narrating while pointing at the parts in the slide deck; however, there was no cursor seen. ○ Hence, the information below includes information directly from the source of the images (CDC) Figure 6 In biopsy specimens, you may sometimes see the adults ○ Left: male ▸ Alae (blue arrow), intestine (red arrow), testis (black arrow) ○ Middle: female ▸ Alae (blue arrow), intestine (green arrow), ovaries (black arrows) Sometimes, you may also see the eggs ○ Right: egg in a colon D. TREATMENT Any of these drugs are given as single dose initially, followed by another dose 2 weeks later ○ Drug of choice: Albendazole ○ Alternative: Mebendazole and pyrantel pamoate The succeeding dose 2 weeks later is done because these drugs can affect or kill the adult worms but not as effective towards the eggs ○ The idea is for the eggs, which are still present, or retroinfection when they go back, you want to treat again to cover for those Although it is simple to effect a temporary cure, complete elimination may prove difficult because of reinfection from: ○ Contaminated environment (contamination of infected individuals to the environment) ○ Asymptomatic members of the same household or institution Repeated treatment may be necessary and other members of the family or school or institution wherein you find the affected individual should also be treated E. PREVENTION Proper hygiene ○ Washing hands with soap and warm water after using the toilet ○ Since this is usually seen in pediatric patients, changing diapers and then handling of food can happen ▸ There must be proper hand hygiene YL6:07.16 Intestinal Nematodes Showering vs. bathing ○ For individuals infected with Enterobius, showering is better than bathing ○ Shower, instead of bathing, helps remove a large amount of eggs in the skin ○ It avoids potentially contaminating bathwater with pinworm eggs when bathing versus showering ○ Infected people should not co-bathe or share a bath with other people during the time of infection unless they are cleared for the infection already Cut fingernails regularly, avoid biting the nails, and scratching around the anus ○ Since the general route of infection of enterobiasis revolves around an infected individual scratching the perianal area ▸ Eggs are transferred over to their hands due to this Frequent changing of underclothes and bed linens ○ Since eggs are deposited in the perianal area, there is a chance that these eggs will be deposited to the clothes or beddings ○ Where ability of the eggs to survive the environment comes into play ○ Even dry infected clothes, since eggs are able to survive ▸ If one were to touch the clothes and transfer the eggs to the hands, one could still get infected if there is inadvertent touching of the mouth and hands ○ Patients with Enterobius are recommended to change their beddings or undergarments first thing in the morning to avoid transmission of eggs to the environment and risk reinfection ○ When removing clothing, individuals should avoid shaking them or doing manipulations ▸ Otherwise, these might cause the eggs to be transferred elsewhere ▸ Should be carefully placed into the laundry and placed into hot water and a hot dryer to kill any eggs there III. CAPILLARIA PHILIPPINENSIS First reported in 1963 ○ 29-year old male from Ilocos Norte ○ Presenting Symptom: Intractable Diarrhea ○ Also called “Pudoc Disease” ▸ This was because after the reported case in 1963, there was a reported outbreak in Pudoc, Ilocos Sur Endemic to the Philippines ○ Seen in Northern Luzon, Zambales, Leyte, Zamboanga del Norte, Zamboanga del Sur, Agusan del Sur, Misamis Occidental ○ Also in other countries such as Thailand, Iran, Japan, Indonesia, UAE, South Korea, India, Taiwan, Egypt, and Laos One gets infected through the ingestion of uncooked or partially cooked small freshwater or brackish water fish Natural host are fish-eating birds ○ Such as Bagsit or Bagsang Incidental host: Humans Phylum: Nematoda ○ Superfamily: Trichinelloidea ○ Other organisms under the superfamily include Trichinella For Adults: ○ Thin filamentous anterior end ○ Slightly thicker posterior end ○ Unique: Presence of a stichosome ▸ Another name for the esophageal structure of the Capillaria ▸ Called stichosome because it is lined by stichocytes which are individual oval-rounded cells in the Capillaria ○ Males: ▸ 1.5 to 4.0 mm long ▸ Spicule with unspined sheath ○ Females: ▸ 2.0 to 5.0 mm long ▸ Vulva found at the junction of the anterior and middle thirds of the parasite ○ Life span: 1-2 months 3 Figure 7. C.philippinensis with sex-specific parts Eggs: ○ Elongated or peanut shaped ▸ Due to waste in the middle ○ 35-45 μm in length and 20-25 μm in width ○ Thick, radially-striated shell ○ Flat, bipolar plugs ○ Released as un-embryonated Larva: ○ Usually have an esophageal bulb but no cephalic ala ○ Approximately 140 to 150 μm in length and 10 μm in width A. LIFE CYCLE Ingestion of infected fish ○ Infective stage: larva Larva are released in the small intestines, burrows into the intestinal mucosa and mature Adult females ○ May produce eggs with a thick shell ○ Sometimes produce eggs without shells (only has a thin vitelline membrane), and/or ○ Directly produce larva ▸ Can produce an egg without a shell, but matures in the body and releases the larva instead of the ova ○ “First-generation” (when first infected with Capillaria) of adult females will release eggs with thin shells and larva ▸ Subsequent generations would produce more of the typical ova with the thick shells Eggs passed in stool which may contaminate water sources (wherein Freshwater/Brackish water fishes live) Eggs are ingested by Freshwater/Brackish water fish (intermediate host) through material (e.g., stool) contaminated with ova ○ Becomes infected with Capillaria ○ Eggs release larvae which invade the tissues of the fish ○ Cycle continues when you ingest improperly prepared or uncooked fish Diagnostic stage: unembryonated egg Autoinfection ○ Similar to Enterobius which has autoinfection through retroinfection ○ May lead to hyperinfection or an increased burden or load of infection ○ Live larvae directly produced may reinvade the intestinal mucosa and repeat the life cycle, or ○ Thin-shelled eggs will release within the intestines the larvae that will reinvade the small intestinal mucosa ○ There is no need for the larvae to be released into the environment and for it to be reingested ▸ Can be done within the body of the host or infected individual YL6:07.16 Intestinal Nematodes Figure 8. Capillaria philippinensis life cycle B. CLINICAL MANIFESTATIONS Malabsorptive syndromes (due to the destruction and blunting of the intestinal villi as larva burrows into the intestinal mucosa) Abdominal pain Severe diarrhea (up to 8-10 voluminous stools per day) Borborygmi Electrolyte imbalance In severe cases seen in hyperinfection, patients may present with chronic diarrhea and develop a protein-losing enteropathy leading to cachexia, weight loss, and even death C. DIAGNOSIS Identification of ova ○ Microscopic examination of stool/stool examination (wet mount) ▸ Direct mounting of the stool specimen with a non-specific stain (NSS) ▸ Look for characteristic eggs – E.g., peanut-shaped, bipolar plugs, thick shell with radial striations ○ Microscopic examination of stool/stool examination with concentration techniques (e.g., Formalin Ether Concentration Technique/FECT) ▸ To increase the yield of stool examination Identification of adult worm/larva ○ Similar to Enterobius ○ May be seen in stool if with high burden of infection (i.e., hyperinfection) ○ May occasionally be seen in tissue specimens submitted for routine tissue processing (biopsy) Immunoassays/serologic tests (e.g., ELISA) ○ Other immunochromatographic tests (e.g., lateral flow) are present in the market PCR ○ Rather impractical in countries that are endemic for the infection D. TREATMENT Drug of choice: Mebendazole ○ 200 mg BID for 20 days Alternative: Albendazole ○ 400 mg OD for 10 days 4 E. PREVENTION Improvements in sanitation ○ Especially because eggs are passed in the stool ○ Prevent contamination with brackish water or water where freshwater fishes live Health education ○ Teach individuals about sanitation and hygiene and proper food handling Capacity building for health personnel ○ Improve ability to diagnose early, especially cases of possibly fatal hyperinfection ○ Training of medical professionals for recognition of possible capillariasis ▸ Symptoms of chronic diarrhea, history of eating raw fish ▸ Reinforce knowledge in identification of Capillaria through diagnostic methods Figure 9. Morphology of a parasitic adult female Strongyloides stercoralis Active Recall Box 1. T/F: In preventing E. vermicularis infection, showering is better than bathing. 2. T/F: The infective stage of C. philippinensis is unembryonated egg. Answers: 1T, 2F Rationale: 1T: Showering is better than bathing because showering avoids potentially contaminating bathwater. 2F: The infective stage of C. philippinensis is the larva whereas the unembryonated egg is the diagnostic stage. Figure 10. Free-living adult male Strongyloides stercoralis IV. STRONGYLOIDES STERCORALIS Also known as threadworm in some countries Smallest nematode of man Potentially one of the deadliest helminthic parasites Capable of heart-lung migration Facultative parasite ○ Can exist as free-living nematode in optimal environmental conditions Epidemiology ○ Tropical and subtropical countries with heavy rainfall ○ Humans are the only hosts (definitive host) Phylum: Nematoda ○ Order: Rhabdtinina ○ Family: Strongylidae ○ Genus: Strongyloides Adult parasitic female ○ Approximately 2 mm long ○ Colorless, semi-transparent, finely striated cuticle ○ Slender tapering anterior, short conical pointed tail ○ Short buccal cavity with four indistinct lips ○ Parthenogenetic (do not need males to produce eggs) ○ Esophagus extends to anterior 4th of the body ○ Vulva is located ⅓ of the body length from the posterior end ○ Uterus contains a single file of 8-12 thin-shelled, transparent ova You do not see parasitic adult males, only parasitic adult females Adult forms follow the general characteristic of helminths that females are larger than males Table 1. Comparing adult male and female Strongyloides stercoralis morphology Male Free-living form: approximately 1mm long Female Free living from: generally smaller than parasitic females Ventrally curved tail with 2 spicules Double-bulbed esophagus (protrusion pointed with a red arrow in Figure 10) No caudal alae or expansion of the Tapered conical posterior end cuticle towards the caudal end YL6:07.16 Intestinal Nematodes Figure 11. Free-living adult female Strongyloides stercoralis (on the left), eggs (within the encircled segment), and larva (pointed smaller longitudinal creature on the right) Eggs ○ Very similar in morphology to those of hookworms ▸ Difficult to differentiate the eggs of the two ○ Clear, thin shell with the embryo inside ○ Approximately 50-60 µm by 30-35 µm in size Take Note! When discussing Strongyloides, always have hookworms in mind due to their similarities in morphology of different stages and route of infection (skin penetration) Larva ○ Rhabditiform: feeding stage ▸ Usually the first stage after it is released from the egg ▸ Approximately 225 µm in length ▸ Diagnostic stage (rather than the egg stage) ▸ Elongated esophagus with pyriform posterior bulb ○ Filariform: infective stage (non-feeding) ▸ Slender and elongated ▸ Approximately 550 µm in length ▸ With a distinct cleft (notch) at the tail (encircled in Figure 14) 5 Figure 12. Rhabditiform stage of Strongyloides stercoralis Figure 16. Genital primordium of Strongyloides stercoralis (rhabditiform) Figure 13. Filariform stage of Strongyloides stercoralis Figure 17. Rhabditiform hookworm with an inconspicuous genital primordium Figure 14. Notched tail (pink dot) of a filariform S. stercoralis larva Table 2. Comparing larval forms of Strongyloides stercoralis and hookworms Rhabditiform Larva Strongyloides Hookworm A. LIFE CYCLE Buccal capsule Short Long Genital Primordium Prominent Small (inconspicuous) Filariform Larva Strongyloides Hookworm Esophagus Long Short Tail Notched/Forked Pointed Sheath (outer covering) Unsheathed Sheathed Figure 15. Anterior portion of Strongyloides stercoralis vs. hookworm (rhabditiform) YL6:07.16 Intestinal Nematodes Figure 18. Filariform hookworm PARASITIC CYCLE Contact of filariform larvae with bare skin ○ Recall: Filariform larva is the infective stage Larva penetrate the intact skin of host and travel by various pathways to the lungs ○ Most commonly: ▸ Hematogenous ▸ Lymphatics ○ There are instances in which the filariform larvae travel directly through tissues to other areas of the body (usually intestines) Once in the lungs (usual route), larvae are coughed up into the bronchial tree due to irritation and swallowed into the digestive tract ○ Allows the larva to reach the small intestines (duodenum and upper jejunum) and mature into adult worms Adult female invades into the intestinal mucosa into the submucosa, where they may produce eggs which develop into rhabditiform larva Rhabditiform larva travel back into the intestinal lumen Rhabditiform larva can be passed in stool or stay in the intestines causing autoinfection ○ Recall: autoinfection occurs when the rhabditiform larva matures into filariform larva and invades the intestinal mucosa ○ Similar to capilaria Diagnostic stage: Rhabditiform larva 6 Figure 20. Strongyloides stercoralis skin invasion Figure 19. Strongyloides stercoralis life cycle FREE-LIVING CYCLE Rhabditiform larva are passed in the stool of an infective definitive host May develop into either infective filariform larvae (direct development) or free-living adult males and females Once in the environment, adults that mate produce eggs, from which rhabditiform larvae hatch and eventually become infective filariform larva The filariform larvae penetrate the human host skin to initiate the parasitic cycle ○ Infective filariform larvae may reinfect a host (e.g., humans) This second generation of filariform larvae cannot mature into free-living adults ○ Must find a new host to continue the life cycle Larval migration ○ Lobar pneumonia and hemorrhage ○ Cough and tracheal irritation Penetration of intestinal mucosa ○ Light infections are usually asymptomatic ○ Moderate infections may cause alternating diarrhea and constipation ○ Heavy infections (hyperinfection) are usually seen in immunocompromised individuals and may be characterized as: ▸ Cochin China Diarrhea – Intractable, painless, intermittent bloody and watery diarrhea ▸ Abdominal pain ▸ Borborygmi ▸ Malabsorptive syndromes due to destruction and blunting of the intestinal villi ▸ Edema ▸ Emaciation ▸ Loss of appetite ▸ Anemia ▸ Lobar pneumonia ▸ Ileus ▸ Intestinal obstruction – Occurs when the burden of infection is high ▸ GI bleeding – Due to invasion ▸ Cachexia CHRONIC INFECTION B. CLINICAL MANIFESTATIONS Incubation period: approximately 1 month ○ From infection to being able to see the rhabditiform larvae in stool ○ Takes around a month to identify if any rhabditiform larvae is in the stool specimen 3 PHASES OF ACUTE INFECTION Skin invasion ○ Recall: ▸ Infection starts when the filariform larva penetrates the skin of the host ○ Area where the filariform larvae invades will produce local erythema, pruritic hemorrhagic papules, and larva currens ○ Larva currens ▸ Larvae traveling through the skin before it enters the deeper tissues to travel to the lungs ▸ A serpiginous urticarial rash, commonly involving the buttocks and waist ▸ Formed as filariform larvae that enters the perianal skin and migrate under skin during autoinfection – Shorter duration, faster movement (vs. cutaneous larva migrans or CLM) – CLM is for hookworms and it may last for months, whereas, larva currens may only last for days ▪ Hookworm larvae travels around 1-2 cm per day, but larva currens is faster and it is visually seen moving – In larva currens, it is usually recurrent ▪ Filariform larvae remains in your skin, penetrates it, and travels instead of the larvae being released into the environment YL6:07.16 Intestinal Nematodes Chronic uncomplicated strongyloidiasis is often asymptomatic but may present with: ○ Intermittent vomiting ○ Diarrhea ○ Constipation ○ Borborygmi ○ Skin symptoms C. DIAGNOSIS Identification of larvae is still the most commonly used way to determine the presence of Strongyloides stercoralis ○ May be seen occasionally in stool, duodenal fluid, and sputum ▸ If with high burden of infection and/or disseminated infections Recall! In disseminated infections, the filariform larvae will penetrate to the skin and travel to the lungs via various routes: ○ Hematogenous route ○ Lymphatics ○ Direct tissue penetration Reason why the larvae can disseminate into different parts of the body and is not limited to the lungs and the GI tract ○ The stool can be examined in wet mounts either directly or after concentration ○ Due to the low yield, it is recommended to do concentration techniques when examining the stool specimens: ▸ Baermann funnel sedimentation technique ▸ Culture via Koga agar plate ▸ Charcoal culture ▸ Harada-Mori filter paper technique ▸ Beale’s string test/Entero-Test 7 ▸ Duodenal aspiration – Strongyloides stercoralis can be seen in the duodenum or in the upper jejunum ○ Adults and larvae may occasionally be seen in tissue specimens submitted for routine tissue processing Figure 23 Steps: 1. Swallow pill (“sugar capsule”) attached to the string 2. Leave it for a few hours 3. Take it out and examine for the presence of larvae There are different Entero-Tests for pediatric and adult patients ○ Strings are longer for adults SEROLOGIC TESTS Figure 21. Harada-Mori filter paper technique Figure 21 Steps: 1. Place the stool on one end of the filter paper 2. Place the stool sample in the water 3. Leave the sample for around 7-10 days (the larvae will travel down into the distilled water) 4. Remove the strip and close the tube 5. Centrifuge the sample at 1500 rpm for 2 minutes 6. Discard the supernatant 7. Read the slide with the 10x objective of the microscope 8. Using a pipette, remove the sediment, place it on a slide and re-cover it with a cover glass Serology tests (i.e., ELISA) have shown to have sensitivity of up to 88% and specificity of 99% May not be useful in filariasis-endemic areas like the Philippines ○ Due to cross-reactivity to various organisms ○ May result in false-positive result in ELISA for Strongyloides when patient has something else (e.g., Filariasis) Serologic tests are unable to distinguish active from past infections ○ Detecting antibodies against Strongyloides doesn’t necessarily mean that there is an active infection ○ Presence of IgGs from past Strongyloides infection have some degree of persistence in the body Other molecular techniques are available ○ I.e., PCR ○ But currently not cost-effective to do PCR for detecting Strongyloides in the Philippines D. TREATMENT Thiabendazole is the drug of choice for Strongyloides ○ However it has severe side effects ○ Majority have shifted to Ivermectin and Albendazole Ivermectin ○ Slightly more effective in terms of clearing out parasite than Albendazole with dose of 200 ug/kg ○ Single dose repeated after 1 week or daily for 3 days for those with hyperinfection or disseminated strongyloidiasis Albendazole ○ 400 mg OD for 3 days repeated for 2 weeks E. PREVENTION Figure 22. Funnel sedimentation test Figure 22 Steps: 1. Place stool in the mesh 2. Fill it with liquid (usually distilled water) 3. Let liquid drain down the funnel 4. Examine collected liquid after sedimentation Larvae will travel out from stool sample through the mesh, down the funnel and into the collected liquid Environmental sanitation ○ Cut the cycle by avoiding contamination of environment (e.g., water ways) with stool where infective stages are present Health education ○ For public to have proper hygiene ○ For health professionals to have higher index of suspicion in cases “WASH” approach ○ For soil transmitted helminths (STHs) ○ Access to clean water and sanitation ○ Promotion of hygiene education ○ Regular deworming ▸ Not done for Strongyloides stercoralis ▸ Used for other STHs Active Recall Box 3. The diagnostic stage of Strongyloides stercoralis is? A. Egg stage B. Filariform larva C. Free-living male D. Rhabditiform larva 4. Which of the following symptoms is commonly associated with chronic uncomplicated strongyloidiasis? A. Abdominal pain B. Borborygmi C. Intractable, painless, intermittent bloody and watery diarrhea D. Intermittent vomiting Answers: 3D, 4C Figure 23. Entero-Test device prior to swallowing (left) and Entero-Test in situ (right) YL6:07.16 Intestinal Nematodes 8 QUICK REVIEW QUESTIONS 1. T/F: The most common clinical manifestation of Enterobius vermicularis infection is enuresis. 2. What is the drug of choice for Strongyloides? A. Albendazole B. Ivermectin C. Thiabendazole D. Mebendazole 3. T/F: In Scotch tape swab, the adhesive surface of the tape must touch the perianal region several times. 4. What is true about Capillaria philippinensis? A. It is rod-shaped B. It relies on the ingestion of cooked brackish water fish for transmission C. It has a thick filamentous anterior end D. Presence of a stichosome 5. Strongyloides stercoralis nematodes are facultative parasites. The parasitic adult male has a slender tapering anterior and short conical pointed tail. A. Only statement 1 is true B. Only statement 2 is true C. Both statements are true D. Both statements are false 6. Select the statement that best describes Strongyloides stercoralis. A. Sheathed filariform larva with a long buccal capsule and prominent genital primordium B. Infection occurs through ingestion of contaminated food and water C. This parasite is capable of autoinfection within the host lungs D. Rhabditiform and filariform larval stages are the feeding and infective stages, respectively 7. What does not characterize heavy infections (hyperinfection) of Strongyloides stercoralis? A. Cochin China disease B. Borborygmi C. Nausea D. Intermittent vomiting 8. Which of the following is not a clinical manifestation of an Enterobius vermicularis infection? A. Eosinophilia B. Pruritus ani C. Insomnia D. Vulvitis 9. The definitive hosts of Capillaria philippinensis are freshwater and brackish water fish. Unlike Enterobius vermicularis, C. philippinensis cannot cause autoinfection. A. Only statement 1 is true B. Only statement 2 is true C. Both statements are true D. Both statements are false 10. The following are Strongyloides stercoralis’ 3 phases of acute infection EXCEPT: A. Skin invasion B. Larval migration C. Penetration of intestinal mucosa D. Larva currens 5. A. Only statement 1 is true. Strongyloides stercoralis nematodes are facultative parasites. There are no parasitic adult Strongyloides stercoralis males. 6. D. Rhabditiform and filariform larval stages are the feeding and infective stages, respectively. Strongyloides filarial larvae are unsheathed and their rhabditiform larvae have short buccal capsules with prominent genital primordia. Infection with Strongyloides occurs through skin penetration. Autoinfection occurs within the host intestines. 7. D. Intermittent vomiting. Intermittent vomiting is a complication of Chronic uncomplicated strongyloidiasis 8. A. Eosinophilia. Eosinophilia is not an expected finding in an Enterobius vermicularis infection. Pruritus ani is the most common symptom. Oviposition can happen in nearby structures causing vulvitis. Egg deposition is nocturnal which can cause insomnia. 9. D. Both statements are false. Freshwater and brackish water fishes are intermediate hosts of the parasite. Similar to Enterobius, C. philippinensis is capable of causing autoinfection. 10. D. Larva currens. Skin invasion, larval migration, and penetration of intestinal mucosa are the three phases of Strongyloides stercoralis’ acute infection. Larva currens is basically a condition wherein a larva travels through the skin before it enters the deeper tissues to travel to the lungs. REFERENCES REQUIRED Chu, A.C. (2024, January, 23). Intestinal Nematodes Part 2 [Video]. SUPPLEMENTARY Centers for Disease Control and Prevention. (2019, August, 5). CDC DPDx - Enterobiasis. www.cdc.gov/dpdx/enterobiasis/index.html Concerns and Feedback form: http://bit.ly/YL6CFF2027 How’s My Transing? form: https://bit.ly/2027YL6HMT Mid-Semester Evaluation form: https://bit.ly/2027YL6MidSem End-of-Semester Evaluation form: https://bit.ly/2027YL6EndofSem Errata Points Trackers: https://bit.ly/YL62027EPT YL6 TransMap: https://bit.ly/2027YL6TransMap FREEDOM SPACE ANSWER KEY 1F, 2C, 3T, 4D, 5A, 6D, 7D, 8A, 9D, 10D RATIONALE 1. False. The most common clinical manifestation of E. vermicularis infection is nocturnal pruritus ani. 2. C. Thiabendazole. Thiabendazole is the drug of choice for Strongyloides. However it has severe side effects. 3. True. In Scotch tape swab, the adhesive surface of the tape must touch the perianal region several times. 4. D. Presence of a stichosome. It is another name for the oesophageal structure of the Capillaria. This is also present in other nematodes close to C. philippinensis YL6:07.16 Intestinal Nematodes 9