Soil-Transmitted Helminths and Toxocara spp. PDF

PH 172: MEDICAL HELMINTHOLOGY AND PROTOZOOLOGY SOIL-TRANSMITTED HELMINTHS AND TOXOCARA SPP. Professor Myra S. Mistica, MPH | August 22, 2024 Trans #03...

PH 172: MEDICAL HELMINTHOLOGY AND PROTOZOOLOGY SOIL-TRANSMITTED HELMINTHS AND TOXOCARA SPP. Professor Myra S. Mistica, MPH | August 22, 2024 Trans #03 INTENSITIES OF STH INFECTION OUTLINE Measured by number of eggs per gram of stool A. Soil-transmitted Helminths Classified as light, moderate, or heavy a. Factors Affecting Transmission b. Intensities of STH Infection c. Control Programs B. Intestinal Nematodes a. Ascaris lumbricoides b. Trichuris trichiura c. Hookworms d. Strongyloides stercoralis e. Toxocara spp. C. Stool Examination Techniques a. Kato Katz Technique b. Formalin Ether Concentration Technique Figure 2. Intensities of STH Infection (WHO, 1998). c. Flotation Techniques d. Harada-Mori / Test Tube Culture Technique CONTROL PROGRAMS D. Review Questions The “NTD Roadmap”, published by the World Health E. References Organization (WHO) in 2012, set two targets for the control of soil-transmitted helminthiases (STH) by 2020, namely: SOIL-TRANSMITTED HELMINTHS ○ 75% of preschool (pre-SAC) and school-age children Most common parasitic infection (SAC) in need of treatment are regularly treated More than 1.5 billion people (24% of the world’s ○ 75% coverage with preventive chemotherapy (PC) is population) are affected by STH infection achieved in pre- SAC and SAC in 100% of countries Transmitted by eggs present in human feces which World Health Organization contaminate soil in areas with poor sanitation ○ Prevent and control morbidity through the periodic STH leads to intestinal obstruction, anemia, malnutrition, treatment of at-risk population (PSAC, SAC, women of dysentery syndrome, fever, dehydration, vomiting, and child-bearing age) colitis Department of Health, Philippines Results in poor growth, reduced physical activity, and ○ STH Control Program impaired learning ability in children ○ Integrated Helminth Control Program Disease burden of STH in the country among vulnerable and high-risk groups is quite high and way above the global standard of less than 20% Cumulative Prevalence (CP) Reduce the Cumulative Prevalence of STH to less than 20% and Prevalence of Moderate to Heavy Intensity Infection (MHII) to less than 2% ○ DepEd - school-based MDA ○ Community-based MDA Other Control Programs / Interventions ○ WASH (Water, Sanitation and Hygiene) Piped-water access was associated with reduced odds of A. lumbricoides (60%) and T. trichiura (43%) infection Latrine availability and usage - 38–46% reduced Figure 1. Life cycle of intestinal helminths. odds of A. lumbricoides infection and 39–42% reduced odds of T. trichiura infection were FACTORS AFFECTING TRANSMISSION reported Environmental conditions Hand washing after defecation - reduced odds of ○ Soil condition STH infection (53%) ○ Climate Soap use or availability (47%) Socio-economic Hand washing before eating and after defecating ○ Sanitation facilities was associated with reduced odds of A. ○ Water supply lumbricoides infection (62% and 55%, ○ Education respectively) Health behaviors ○ Defecation habits ○ Personal hygiene ○ Occupation-related #MagkabigkisBenteSais Ador, Bartolome, Lanting, Macunat, Se | 1 of 12  INTESTINAL NEMATODES Ascaris lumbricoides Giant intestinal roundworm Most common intestinal roundworm Widely distributed in the Philippines (rural and urban areas) Common among children: ○ 54%-67%: School-age children ○ 66%: Pre-school age Figure 6. Morphology of a fertilized egg of Ascaris lumbricoides. ○ 65%: PSAC Figure 7. Morphology of an embryonated egg of Ascaris lumbricoides. Life Cycle Direct life cycle Figure 3. Ascaris lumbricoides ovas in different shapes. Embryonation: in soil for 2-3 weeks Embryonated eggs can survive in soil for few months to Morphology about 2 years Male: 15-31cm x 3mm Egg to adult: 1-11 weeks ○ Posterior end curved Life span of adult worm: 1 year Female: 20-35cm x 5mm Has a lung phase ○ Posterior end straight ○ Anterior ⅓: depression pr constricted vagina (genital ring) Lips: 3 lips-center buccal cavity Stages: unfertilized egg, fertilized egg, and embryonated egg ○ 3 layers can be seen in a fertilized egg (2 layers develop after fertilization) Figure 4. Adult forms of Ascaris lumbricoides female and male worms (left), and the 3 lip-center buccal cavity of Ascaris lumbricoides. Figure 8. Life cycle of Ascaris lumbricoides. Pathology and Clinical Manifestations Reaction to migrating larvae ○ Pulmonary manifestations ○ Asthmatic-like attacks (bronchial rales and chest pain) ○ Pneumonitis (massive Ascaris infections) ○ Loeffler’s syndrome Adult worms in duodenum and jejunum feed on nutrients Wandering adult worm = erratic behavior Figure 5. Morphology of an unfertilized egg of Ascaris lumbricoides. ○ Entangled (intestinal obstruction) ○ Appendix (acute appendicitis) ○ Bile duct (biliary ascariasis) ○ Liver parenchyma (multiple abscesses) ○ Block the pancreatic duct (acute pancreatitis) ○ Perforate the bowel (peritonitis) Migration of larvae to the lungs is not erratic behavior because it is a part of its life cycle PH 172 | Soil-Transmitted Helminths and Toxocara spp. 2 of 12 Diagnosis Clinical signs and symptoms ○ Vague; confirmation by laboratory diagnosis is needed ○ Children -passing out = Ascaris Laboratory ○ Direct Fecal Smear (DFS) ○ Kato Katz / Thick Technique Treatment, Prevention, and Control Individual infections ○ Single dose of broad spectrum anthelmintics: Figure 10. Trichuris trichiura egg. Albendazole, mebendazole and pyrantel pamoate 400 mg single dose albendazole Life Cycle 500 mg mebendazole Direct life cycle 10 mg / kg body weight pyrantel pamoate ○ But no lung phase unlike Ascaris ○ Cause paralysis of the parasite Embryonation occurs in the soil - 2-3 weeks ○ Ascaris adults do not have organs for attachment to Embryonated eggs can survive in soil - few months to the intestinal wall about 2 years ○ 100% cure rate Egg to adult - 12 weeks Community Life span of adult worm - 2 years ○ 3x/year for 3 years Infective stage: Embryonated egg ○ Mass treatment for re-infection Diagnostic stage: Unembyonated egg (passed through ○ Selective treatment feces) Positive for eggs Summary (BSPH 2024) Targeted group (children) 1. Embryonic eggs are ingested by an individual Discriminate fecal disposal (oral-fecal route). ○ Sanitary disposal of feces 2. Larvae hatch in the small intestines and penetrate the Personal family intestinal wall for 3-10 days. ○ Community hygiene 3. Larvae develop into an adult and inhabit the cecum of Mass treatment; 2 to 3x/year the colon. ○ Children (target population) 4. Reproduction takes place: females will lay unembryonated eggs through feces. Trichuris trichiura Causes trichuriasis Whipworm, whip-like Habitat - large intestine (cecum) Figure 9. Trichuris trichiura. Morphology Male: 30-45 mm ○ Coiled posterior end Female: 35-50 mm ○ Posterior half is stout; blunt posterior end Figure 11. Trichuris trichiura life cycle. Both: esophagus (anterior 1/5) Pathology and Clinical Manifestations ○ Lined with stichocytes/stichosomes Egg Light infections - no symptoms (asymptomatic); no ○ 50-54 microns x 22-23 microns significance ○ Barrel or lemon-shaped with prominent protruding Heavy or chronic – (>5,000 eggs/gm feces) bipolar plugs ○ Blood streaked diarrhea (due to intestinal damage) ○ Has an unsegmented mass protected by a thick, ○ Abdominal pain, nausea, vomiting, anemia brown egg shell Attached on walls of the large intestine feed on intestinal tissues, colon, rectum (rectal, anal prolapse) Prolapse; frequent LBM; loss of muscle tone of the anal sphincter Invade appendix PH 172 | Soil-Transmitted Helminths and Toxocara spp. 3 of 12  Figure 12. Rectal prolapse. Diagnosis Same as Ascariasis: ○ Direct Fecal Smear (DFS), Kato-thick, Kato-Katz Figure 15. Morphology of male and female hookworms. Epidemiology Larval morphology Prevalence – 80-84% parallels that of ascariasis ○ Rhabditiform larva Most infections are light to moderate Short and stout Eggs are susceptible to dryness Short esophagus; mascular, flask Long-life span of the worm (2 years) Genital primordium 60 M eggs in 2 years Pointed posterior end Children: 5 - 15 y.o Feeding stage; open buccal capsule Factors affecting transmission as in Ascaris ○ Filariform larva Longer, slender Treatment, Prevention, and Control Slender and elongated esophagus Same as Ascariasis Sheath Albendazole, mebendazole, oxantel-pyrantel Pointed posterior end Non-feeding stage; closed HOOKWORMS Infective stage Adults suck blood Attached to the mucosa of the small intestine (jejunum) Hookworms: ○ Necantor americanus - human hookworm Semilunar cutting plate ○ Ancylostoma duodenale - human hookworm 2 pairs of teeth ○ Ancylostoma ceylanicum ○ Ancylostoma caninum - dog hookworm 3 pairs of teeth Figure 16. Differences between the morphologies of Strongyloides and ○ Ancylostoma braziliense - cat and dog hookworm larvae. 2 pairs of teeth Figure 13. Hookworm dentition: (A) N. americanus, (B) A. duodenale, (C) A. caninum, and (D) A. braziliense. Morphology Eggs ○ Ovoidal Figure 17. Buccal canals Strongyloides and hookworm rhabditiform larvae. ○ 56 - 60 x 34 - 40 microns ○ Differentiation of species is difficult (human vs. animal spp.) Figure 14. Hookworm egg morphology. Figure 18. Strongyloides filariform and hookworm tail tips. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 4 of 12 Life Cycle Diagnosis Direct life cycle Stool examination - identification of the hookworm ova in Embryo within the egg develops rapidly and hatches into the feces rhabditiform larva in 1-2 days ○ DFS, Kato-thick/Katz, FECT Rhabditiform to filariform larva in 7-10 days Culture methods: Harada-Mori Filariform larva - Infective stage ○ Allow hatching of larvae from eggs on filter paper Skin penetration/ingestion strips with one end immersed in water ○ Recommended for species identification Treatment, Prevention, and Control Treatment ○ Broad spectrum antihelminthics: Albendazole Mebendazole Pyrantel pamoate ○ A severe anemia; raise hemoglobin level Ferrous sulfate (200 mg 3x/day) - oral for 3 months ○ Topical antihistamine - CLM Prevention and Control ○ Proper disposal of feces ○ Use of footwear ○ Avoid ingestion of unwashed / improperly washed vegetables (A. duodenale) Figure 19. Life cycle of human hookworms. ○ Health education, personal; family community hygiene Pathology and Clinical Manifestations ○ Treatment of positive cases to prevent spread of At the site of entry of larvae infection ○ Ground itch or dew itch (itching due to penetration of the filariform larvae, a hypersensitivity reaction Strongyloides stercoralis because of the enzymes) Threadworm ○ Rash around the area of penetration Strongyloidiasis - infection with Strongyloides ○ Itching, edema, erythema, papulovesicular eruptions Tropical and subtropical countries, occurs in temperate that can last for two weeks zones In the lungs during larval migration Parasitic and free-living life cycle ○ Bronchitis or pneumonitis – abundant number of The only species capable of autoinfection (replicate in the migrating larvae human host, and may cause infection without the need for ○ Sputum production, cough repeated exposure), persistent infection At small intestine ○ Habitat of the adult worms Morphology ○ Microcytic, hypochromic anemia - chronic moderate Larvae or heavy infection ○ Rhabditiform larva ○ Iron-deficiency anemia (due to bleeding / blood loss Short, open buccal capsule from attachment of adult worms to the intestinal Mascular, elongated esophagus with pyriform mucosa) posterior bulb 0.03 to 0.05 ml blood/day (N. americanus) Genital primordium, small, conspicuous 0.16 to 0.34 ml (A. duodenale) Pointed posterior end ○ Hypoalbuminemia - low level of albumin (loss of ○ Filariform larva blood, lymph and protein) Closed buccal capsule ○ Weight loss, abdominal pain Long esophagus Other clinical presentations: Infective stage ○ Creeping eruptions or cutaneous larva migrans Forked or notched tail ○ Intense pruritus ○ Serpiginous tunnel - at the level of the epidermis Figure 21. Different life stages of Strongyloides stercoralis. Figure 20. Cutaneous larva migrans. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 5 of 12 Life Cycle Immunocompromised patients (cancer, malnutrition, Direct life cycle HIV/AIDS) Free-living cycle ○ Disseminated infection ○ Rhabditiform larvae (from intestine) are passed out in the stool which may: Diagnosis Molt twice → infective filariform larvae Stool examination - Kato Katz / Kato Thick Molt four times → free living adult males and Direct fecal examination females that mate and produce eggs from which Concentration techniques - FECT, AECT new generation of rhabditiform larvae hatch, Flotac/Mini flotac - flotation techniques which may either: Stool culture Develop into new generation of free-living adults, or Epidemiology Develop into filariform larvae Found throughout the world ○ Filariform larvae penetrates human skin to start the Follows the distribution pattern similar to hookworm next cycle infection in the tropics and subtropics as well as Europe Parasitic cycle and USA ○ Filariform larvae → lungs via bloodstream or 50 to 100M estimated infected lymphatics where they penetrate alveolar spaces In the Philippines, 0 to 2.3% depending on the area ○ Larvae in lungs → pharynx via the bronchial tree selected ○ Larvae are swallowed → small intestine where, More frequent in male children, ages 7-14, than among ○ The larvae molt twice and become adult female females and adults worms Autoinfection occurs all over the world ○ Adult worms live in the intestines and produces eggs by parthenogenesis Treatment, Prevention, and Control ○ Rhabditiform larvae are then hatched Albendazole, Thiabendazole ○ The cycle then either repeats or enters autoinfection Ivermectin wherein: ○ Chronic uncomplicated strongyloidiasis Rhabditiform larvae → filariform larvae Prevention and control: same with hookworm infection Filariform larvae penetrate either the intestinal mucosa (internal autoinfection) or skin of Toxocara spp. perianal area (external autoinfection) *From BSPH 2024 Trans Filariform larvae → lungs → pharynx → Zoonotic parasites swallowed → small intestine (normal infective Causes toxocariasis cycle) Caused by larvae of Toxocara canis from dogs and Filariform larvae mature into adults or may Toxocara cati from cats disseminate into the body Common in urban areas with stray dogs and cats Humans are an accidental host Morphology Eggs ○ Spherical, 75090 microns ○ Ovoid, pitted capsule wall ○ Once embryonated, resistant to freezing, moisture, and extreme pH levels for at least a year ○ 2 to 4 weeks, up to several months to become infective ○ Optimum environmental condition: 10-35 °C High soil humidity Life Cycle In human host: ○ Ingestion of embryonated eggs from contaminated soil Figure 22. Life cycle of Strongyloides stercoralis. ○ Larvae released from eggs penetrate the intestinal wall Pathology and Clinical Manifestations ○ Larvae carried by circulation to different organs (liver, Acute strongyloidiasis heart, lungs, brains, muscle, eyes) ○ Invasion of the skin by filariform larvae ○ No adult development ○ Migration of larvae through the body In animal host (natural or definitive): ○ Penetration of the intestinal mucosa by adult female ○ Ingestion of embryonated eggs from contaminated soil worms ○ Larvae released from eggs penetrated the gut wall Light infection ○ Larvae carried by circulation to different tissues and ○ No intestinal symptoms encyst Moderate infection ○ Younger dogs: ○ Diarrhea alternating with constipation Larvae migrate through the lungs → bronchial tree Heavy infection → esophagus → swallowed to gastrointestinal ○ Intractable, painless, intermittent diarrhea tract characterized by numerous episodes of watery and In the GI tract, larvae mature into adults where it bloody stools reproduces PH 172 | Soil-Transmitted Helminths and Toxocara spp. 6 of 12  ○ Older female dogs: Implement strategic anthelmintic treatments of Reactivation of the encysted larvae during dogs and cats pregnancy → infecting the puppies through the Gardens should be fenced transplacental and transmammary routes Thoroughly wash vegetables Adult develops in the intestine of the puppies Avoid consumption of raw/undercooked meat ○ Eggs are secreted by both infected lactating female Proper and frequent handwashing dogs and puppies Municipal ordinances for proper pet-handling on public places should be considered Pathology and Clinical Manifestations STOOL EXAMINATION TECHNIQUES Visceral Larva Migrants (VLM) Diagnostic techniques involving a stool sample ○ Manifested as eosinophilic granulomas There are a few types such as direct stool sample (Kato ○ Livers, lungs, central nervous system, and eyes are Katz), concentration techniques (FECT, AECT), flotation mostly affected techniques (FLOTAC/Mini-FLOTAC), direct fecal ○ Common Signs: examination and stool culture Wheezing alongside lower respiratory systems Associated with liver enlargement and necrosis KATO KATZ TECHNIQUE Ocular Larva Migrants (OLM) Determines the intensity of infection or worm burden ○ Manifested in the eyes Qualitative (positive or negative) and quantitative (egg per ○ Occurs in children aged 5 to 10 years old gram) ○ Common Signs: 41.7g of stool is sieved through a wire screen, covered in Larval invasion of the eye may result to invasion cellophane soaked in glycerine solution then placed on a of the retina template Blindness can occur For surveillance of STH and SCH Covert Toxocariasis (CoTOX) Examined within 30-60 minutes; clearing of hookworm ova ○ Most patients are asymptomatic; eosinophilia is less Low sensitivity to light intensity infections frequent Sensitivity increases with increasing number of specimen ○ Symptoms: and slides processed Coughing, wheezing, chronic or recurrent abdominal pain, hepatomegaly, sleep disturbances, headache, malaise and anorexia Neurological Toxocariasis ○ Larvae may migrate to the brain, meninges and may be found in the cerebrospinal fluid (CSF) ○ Can cause encephalitis Diagnosis Figure 23. Kato Katz Technique. Definitive diagnosis FORMALIN ETHER CONCENTRATION TECHNIQUE ○ Based on the detection of larvae from biopsy tissue Qualitative (time consuming and difficult) Sedimentation to concentrate helminth ova for 1g of stool ○ Clinical and serological tests (currently used) specimen Blood tests ○ IgG ELISA Kits (inadequate specificity) ○ Western blot (unable to differentiate new/old infection) ○ PCR (for animal models) Others ○ Identifying the presence of typical clinical signs of OLM/VLM and exposure history to cats and dogs ○ Medical Imaging (ultrasound, CT Scan, MRI) Treatment, Prevention, and Control Treatment Figure 24. Final centrifuge results in FECT. ○ Visceral Toxocariasis Low sensitivity (28.6%) but highly specific (97.4%) Antiparasitic drugs in combination with Special requirements: anti-inflammatory medications ○ Trained staff Albendazole/Mebendazole ○ Centrifuge ○ Neurological Toxocariasis/Lungs/Cardiac ○ Highly flammable ether (PDEA Controlled) complication Requires more time and effort to perform Antihelminthic treatment is mandatory Protozoan can be seen ○ Ocular Toxocariasis Difficult Usually consists of measure to present progressive damage to the eye Prevention And Control ○ Aims to prevent infection in both humans and animals ○ Soil and environment Control and capture stray dogs and cats Cleaning up of feces from soil and pavements Close potentially contaminated areas Figure 25. FECT Technique. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 7 of 12  FLOTATION TECHNIQUES REVIEW QUESTIONS Developed to detect infective stages of parasites in 1. What is the only species capable of causing infection humans and animals without repeated exposure? a. Ascaris lumbricoides b. Toxocara spp. c. Strongyloides stercoralis d. Trichuris trichiura 2. In the life cycle of Toxocara spp., humans are considered the natural host. a. True b. False 3. What is the technique that helps in identifying and determining the intensity of infection? a. Kato Thick b. Kato Katz Figure 26. Apparatus used in Flotation techniques. c. FECT d. Direct Fecal Smear Use solutions with higher specific gravity than the parasite ova to be floated; fecal debris sinks to the bottom 4. In toxocariasis, what is the name of its manifestation Zinc sulfate or Sheather’s sugar solution that is associated with liver enlargement? Nematode eggs a. Visceral Larva Migrants b. Ocular Larva Migrants c. Covert Toxocariasis d. Neurological Toxocariasis 5. What are the symptoms of a light Trichuriasis infection? a. Diarrhea b. Abdominal pain and vomiting Figure 27. FLOTAC Technique. c. Both a and b d. No symptoms 6. Which of the following statements about Trichuris trichiura is not true? a. Direct life cycle with no lung phase b. Only male worms have an esophagus lined with stichocytes/stichosomes c. Adult larvae inhabit the cecum of the colon Figure 28. Mini-FLOTAC Technique. d. The female worm has a stout posterior half and a blunt posterior end HARADA-MORI / TEST TUBE CULTURE TECHNIQUE 7. An Ascaris lumbricoides egg must be embryonated for Species identification hookworm and differentiation from it to be infective. Strongyloides by allowing larval development a. True Positive stool sample applied to a filter paper strip, placed b. False in a test tube with about 7 cc of boiled or distilled water Filariform larvae generally move downwards against the 8. Which type of Ascaris lumbricoides egg has the upward capillary movement of the water following morphological characteristics: mammillary or Strongyloides larvae move upwards at the upper end of albuminoid layer, transparent hyaline layer, lipoidal the filter paper strip inner layer, and ovoid mass of protoplasm. Gloves should be worn due to possible larvae invasion a. Unfertilized b. Fertilized c. Embryonated 9. The rhabditiform larvae of hookworms are characterized as long, slender, with an elongated esophagus and a pointed posterior end. a. True b. False 10. Dog hookworm with 3 pairs of teeth: a. Necantor americanus b. Ancylostoma duodenale c. Ancylostoma caninum d. Ancylostoma braziliense Figure 29. Harada-Mori Technique. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 8 of 12  ANSWER KEY 1. C 6. B 2. B 7. A 3. B 8. B 4. A 9. B 5. D 10. C REFERENCES Lectures Mistica, M. (2024). Soil-transmitted Helminths [Slides]. https://drive.google.com/file/d/1qlfbYd6_yV6e1wGxv7jvGcWvm Kh5VD8E/view. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 9 of 12  APPENDIX Appendix 1. Kato Katz Technique. Appendix 2. FECT Technique. Appendix 3. FLOTAC Technique. Appendix 4. Mini-FLOTAC technique. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 10 of 12  Appendix 5. Life cycle of Ascaris lumbricoides. Appendix 6. Trichuris trichiura life cycle. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 11 of 12  Appendix 7. Life cycle of human hookworms. Appendix 8. Life cycle of Strongyloides stercoralis. PH 172 | Soil-Transmitted Helminths and Toxocara spp. 12 of 12