Sessions 25-26 Nematodes.pptx

Nematodes PBC 9600 - Microbiology Sessions 25 April 16, 2024 Jyotsna Chawla, Ph.D. Nova Southeastern University Dr. Kiran C. Patel College of Osteopathic Medicine Pre-medical Post-Baccalaureate Program Contact: [email protected] Office Hours: Wednesday 11:00 am-12:00pm Learning objectives 1. Define n...

Nematodes PBC 9600 - Microbiology Sessions 25 April 16, 2024 Jyotsna Chawla, Ph.D. Nova Southeastern University Dr. Kiran C. Patel College of Osteopathic Medicine Pre-medical Post-Baccalaureate Program Contact: [email protected] Office Hours: Wednesday 11:00 am-12:00pm Learning objectives 1. Define nematodes and identify their major morphologic features and stages of their life cycle. 2. Recognize which nematode is described by the common name’s pinworm, roundworm, whipworm, hookworm, and threadworm. 3. Define the term autoinfection, recognize which nematodes can cause it, and indicate the specific mechanisms of autoinfection. 4. Know the pathogenesis and epidemiology of nematodes affecting the gastrointestinal system and tissue; Ascaris lumbricoides, Trichuris trichiura, and Trichinella spiralis. 5. Know the pathogenesis and epidemiology of nematodes affecting the blood and lymphatic system: Brugia malayi and Onchocerca volvulus. 2 1. Define Nematodes: General Characteristics  Nematodes are parasitic worms -> also called Roundworms  Latin -> nemat – “thread” –odes “like”  Elongated, cylindrical worms with tapered ends  Non-segmented  The body of nematodes is covered by a tough, protective cuticle, which is periodically molted as the worm grows  Most nematodes have separate sexes (dioecious) and reproduce sexually*  Nematodes typically have a direct life cycle involving only one host* *there are exceptions to this case An adult Ascaris lumbriocoides worm. They can range from 15 to 35 cm. Credit: CDC. 3 1. Define Nematodes: Structure  Head Region: Relatively distinct head, mouth with 3-6 labial structures, series of denticles on the inner edges of the lips  Body Structure: Bilaterally symmetrical body, may have ridges, rings, or bristles along the body  Tail Region: Adhesive 'caudal gland' located at the tip of the tail  Digestive System: Tubular digestive system with openings at both ends of the digestive tract  Internal Anatomy: The body cavity is filled with the gastrointestinal tract and reproductive organs;  Between the cuticle and the digestive tract lie the nervous system, excretory system, and muscle layers 4 1. Define Nematodes: Life Cycle  Molting (Ecdysis): Nematodes undergo molting, shedding their outer cuticle, to accommodate growth. Typically, nematodes go through four molts (L1 to L4 stages) during their development.  Cuticle restricts growth – must molt to enlarge  Stages in between molts (L1 L4)  L5 is pre-adult stage (develop into adults with no molting)  Migration of larval forms in humans may result in tissue damage or morbidity and mortality  Larvae forms:  Non-infective larvae (Rhabditiform)  Infective larvae (Filariform) egg 5 2. Pinworm, roundworm, whipworm, hookworm, threadworm Pinworm Roundworm Whipworm Enterobius vermiculari s Ascaris lumbricoides Trichuris trichiura Hookworm Threadwor m Necator americanus Strongyloid es stercoralis Discussed in detail under objective 4 6 2. Pinworm  Enterobius vermicularis  Enterobius vermicularis commonly infects the intestines, especially in children  It causes enterobiasis or pinworm infection  8 to 13 millimeters in length  Thread-like Appearance  Adult females have a characteristic sharply pointed tail, which distinguishes them from males  Oval Shape eggs  Transmission occurs through ingestion of pinworm eggs  Symptoms include perianal itching, especially at night  Diagnosis: Microscopic identification of pinworm eggs, scotch-tape test  Treatment involves anthelmintic medications like albendazole or mebendazole  Human is the only host Pinworm Eggs 7 2. Hookworm  Necator americanus  Adult female 9-11 mm; male 7-9 mm  Mouth has two pairs of cutting plates (dorsal & ventral)  Dorsal curve at the anterior end (“hookworm”)  Most common in Tropical areas of S. Asia, Africa, America, Southern US  It causes hookworm disease or Necatoriasis  Transmission occurs through skin penetration by infective larvae present in contaminated soil (barefoot walking, poor sanitation)  Symptoms: abdominal pain, diarrhea, and nausea, iron-deficiency anemia, itching (ground itch) at the site of larval penetration  Diagnosis involves microscopic identification of hookworm eggs in stool samples Each adult worm extracts 0.03 mL of  Humans are the only known host for blood per day Necator americanus. 1L blood loss a day = 33,333 parasites 8 2. Threadworm  Strongyloides stercoralis   Males and females mate in the soil (freeliving part of the life cycle) Only females found in the host  Most common in tropics, subtropics, and warm temperate regions  It causes strongyloidiasis  Transmission occurs through skin penetration by infective larvae present in contaminated soil  Symptoms include gastrointestinal disturbances, larva currens (itching skin rash), Pulmonary infection; and in severe cases, hyperinfection syndrome or disseminated strongyloidiasis, particularly in immunocompromised individuals  Diagnosis involves microscopic identification of Strongyloides larvae in stool samples or by serological tests for specific antibodies  Alternates between free-living and 9 3. Define the term Autoinfection  Autoinfection in nematodes refers to the transfer of a life cycle stage of the parasite from one site to another inside the same host, typically accompanied by morphological transformation  This process involves the transformation of noninfective larvae (rhabditiform) into infective larvae (filariform), which can then penetrate the intestinal mucosa (internal autoinfection) or the skin of the perineal area (external autoinfection)  Infection can be maintained by repeated migratory cycles for the remainder of the host’s life  Example: Strongyloides stercoralis 10 3. Mechanisms of Autoinfection Strongyloidiasis Transmission -> Direct contact o Skin penetration by filariform larvae (L3) Alternates between free-living and parasitic stages o Rhabditiform larvae form either adults and mate in the soil or directly molt 2x to become filariform larvae (L3) that are infectious o Upon skin entry L3 direct migration to s. intestines or lymph to blood then lungs, coughed up, swallowed, and deposit in s. intestines L3 molt 2x adult females o Eggs hatch in s. intestines rhabditiform larvae are passed in stool or reinfect intestines 11 3. Mechanisms of Autoinfection Strongyloidiasis Skin penetration: Pruritus (itching sensation) Urticaria (raised rash = hives) At site of L3 entry Often recurrent along thighs and buttocks Respiratory symptoms (larval migration): Dry cough and sore throat Moderate-heavy burden: Abdominal Pain & Tenderness Nausea/Vomiting, Diarrhea Intestinal inflammation (can extend to small and large intestines) Ulceration – epigastric pain Diagnose -> Rhabditiform larvae in stool Hyperinfection syndrome Rhabditiform larvae filariform larvae widespread disseminate to any organ Profound diarrhea, malabsorption, electrolyte abnormalities 86% fatality rate Patients = immunocompromised by disease, cancer, and corticosteroids 12 Soil-Transmitted Helminths Ascaris lumbricoides Trichuris trichiura Trichinella spiralis Also include: Necator americanus Ancylostoma duodenale Strongyloides stercoralis 13 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides  Roundworm Unfertilized Egg Adult female ~30cm (l) 3-6mm diameter Adult male ~15-30cm (l) 2-4mm diameter  Cylindrical bodies that taper at both ends In males the tail curves ventrally Fertilized Egg  Integument is a chitinous layer of non-nucleated cuticle  Uses longitudinal muscular activity to remain in the intestinal lumen of the host (serpentine motion) 55 m X 40 m 14 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides  Epidemiology ~807 million – 1.5 billion people infected 8,000-10,000 deaths annually Found in warm, moist climates globally ~90% of rural Malaysia infected Most common in children 2-10 years  Why so infectious? Prior infection does not confer protection High number of eggs produced per parasite Durability of eggs in environment (up to 10 y) Asymptomatic individuals can shed for years 15 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides  Transmission -> Fecal-oral (eggs present in contaminated soil or on unwashed or improperly cooked vegetables; Foodborne (human feces are used as fertilizer for agricultural purposes; Ascaris eggs may contaminate crops during cultivation) Mature 8-12 wks Lifespan = 1 yr  Post-fertilization: Zygote secretes fertilization membrane thickens to protect egg Eggs embryonate prior to being infectious (moisture, warmth) Worms reside in the upper 2-3 wks 1 female = 200,000 eggs/d 16 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides 1. Larval release: Upon ingestion, the eggs hatch in the small intestine, releasing larvae that penetrate the intestinal wall Larvae hatches in s. intestine Larvae 17 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides 2. Larval invasion of the mucosa into the venous blood: The larvae migrate through the bloodstream to the liver Larvae 18 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides 3. Migration through the Body: The larvae migrate through the bloodstream to the liver and then to the lungs. In the lungs, they penetrate the alveolar walls and migrate up the bronchial tree to the throat. Larvae are now too large to pass through capillaries Larvae 19 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides 4. Larvae presence in the air sacs triggers cough Larvae 20 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides 5. Coughed-up larvae are swallowed Larvae 21 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides 6. Larvae complete maturation in the intestine: they mature into adult worms, attach and feed, reproduce sexually in the small intestine, and produce a large number of eggs, which are passed out of the host's body in feces. Complete maturation & mate Larvae 22 4. Know the pathogenesis and epidemiology of Ascaris lumbricoides SYMPTOMS  Larval Migration: Fever, cough, wheezing, shortness of breath, and eosinophilia may occur during larval migration  Adults in Intestines (Light Burden/Asymptomatic): Often asymptomatic, but febrile illness can trigger temporary symptoms such as abdominal discomfort  Adults in Intestines (Heavy Burden): Abdominal pain, malabsorption, bowel obstruction DIAGNOSIS  Gold-standard: Detection of knobbycoated eggs in stool  Employ a concentration procedure for collecting eggs in light burden infection  Adults can sometimes be found in stool  Eosinophilia ->High eosinophil count (white blood cells) 23 4. Know the pathogenesis and epidemiology of Trichuris trichiura  Whipworm adult female ~35-50 mm (l) adult male ~30-45 mm (l) Undeveloped embryo  Elongated anterior that stretches into a thread-like point  No excretory system; wastes diffuse through small pores in the integument 50 m X 25 m 24 4. Know the pathogenesis and epidemiology of Trichuris trichiura  Epidemiology  604-795 million people infected  2-3 million infected in US (rural areas of southeast US)  In Brazil, it affects up to 40% of the population  Eggs can survive up to 5 years in soil  Most common in children 2-9 years  Like Ascaris, usually high incidence in areas with poor sanitation practices 25 4. Know the pathogenesis and epidemiology of Trichuris trichiura  Trichuriasis  Transmission -> Fecal-oral, Foodborne Mature 1 mo Ingestion of eggs from eating infected soil or unwashed/uncooked vegetables (human feces used as fertilizer)  Upon ingestion, the eggs hatch in the duodenum Lifespan = 1 yr 3 wks  Adults reside in cecum attached by thin anterior end 1 female = 5,000 eggs/d 26 4. Know the pathogenesis and epidemiology of Trichuris trichiura SYMPTOMS  Light Burden: Often asymptomatic  Moderate Burden: Nausea, abdominal pain, diarrhea, stunting in growth (especially in children), and eosinophilia (elevated eosinophil count in the blood)  Heavy Burden (>800 worms): The colon is infested with worms, mucosal damage, and blood loss, leading to anemia and prolapse of the colon  Attachment of adults to colon and feeding produces ulcerations and hemorrhage (0.005 ml blood/worm/day)  Ulcerations often provide enteric bacteria access to the bloodstream, increasing the risk of systemic infection Colonoscopy picture of extensive Trichuriasis DIAGNOSIS  Fecal smear for the presence of eggs  Colonoscopy 27 4. Know the pathogenesis and epidemiology of Trichinella spiralis  Trichina Worm, relatively small nemarode  Adult female 2.8-3.2 mm (l); male 1.4-1.6 mm (l)  Females are ovoviviparous Produces eggs but does not lay them Eggs hatch in uterus Larvae are released within the s. intestine  Stichosome A specialized structure in the glandular tissue of the esophagus  Cloaca A typical cavity in which the intestinal, waste, and generative canals open 28 4. Know the pathogenesis and epidemiology of Trichinella spiralis  Epidemiology 10,000 cases annually worldwide Worldwide but prevalent in Mexico, southern Asia, Africa, S. America & Middle East About 11-20 cases annually in US (improved pig raising & eating practices)  Primarily associated with consumption of pork products; freezing pork products effectively kills the parasitic larvae 29 4. Know the pathogenesis and epidemiology of Trichinella spiralis  Trichinosis (Trichinellosis)  Transmission -> Foodborne Ingestion of undercooked meat (pork, wild game) contaminated with encysted larvae  Domestic Cycle (affects domestic animals): Rats and pigs serve as hosts and reservoirs in the domestic cycle.  Sylvatic Cycle (affects wildlife): Seals, walruses, whales, bears, and other wildlife serve as hosts and reservoirs in the sylvatic cycle. Adults live 4 wks 36 h 1 wk 1 female = 1,500 larvae 30 4. Know the pathogenesis and epidemiology of Trichinella spiralis 1. Ingestion of encysted larvae Encysted larvae released into the small intestine Larvae Adult female Adult male Larvae develop into adults and mate 31 4. Know the pathogenesis and epidemiology of Trichinella spiralis 2. Larvae undergo maturation Larvae invade mucosa & develop into adults (mate) Larvae Adult female Adult male 32 4. Know the pathogenesis and epidemiology of Trichinella spiralis 3. Adults mate and produce larvae New larvae released by female into s. intestine (penetrate gut wall) Larvae Adult female Adult male 33 4. Know the pathogenesis and epidemiology of Trichinella spiralis 4. Progeny larvae invade the mucosa and access venous blood Larvae invades portal venules (or taken up by lymphatics) Larvae 34 4. Know the pathogenesis and epidemiology of Trichinella spiralis 5. Progeny larvae migration Larvae enters liver and then access the circulation bloodstream Larvae 35 4. Know the pathogenesis and epidemiology of Trichinella spiralis 6. Larvae “seed” different muscle tissue bloodstream New larvae pass from circulation into striated muscle and encyst Larvae 36 4. Know the pathogenesis and epidemiology of Trichinella spiralis SYMPTOMS  Intestinal penetration: Nausea, Abdominal pain, Diarrhea  Larval invasion of muscle: 1000/g Hemoptysis, tachycardia, congestive heart failure, encephalitis, meningitis, delirium, psychosis, coma DIAGNOSIS History of consuming undercooked pork or bear (wild game) meat – or encysted larvae detection in a meat sample Eosinophilia Diagnostic confirmation is by serology, or occasionally, muscle biopsy may be needed 37 Filarial Nematodes  Thread-like parasitic nematodes (roundworms) that are transmitted by arthropod vectors  The adult worms inhabit specific tissues where they mate and produce microfilariae, the characteristic tiny, thread-like larvae. The microfilariae infect vector arthropods, in which they mature to infective larvae Medical Microbiology. 4th edition. Brugia malayi Onchocerca volvulus 38 5. Know the pathogenesis and epidemiology of Brugia malayi  Brugia malayi (Malayan Filaria)  Adult female 43-55 mm (l); male 13-23 mm (l)  Eggs lack a true shell instead, microfilaria are enclosed in a membrane sheath  Adults live coiled around one another  Nocturnal periodicity (microfilariae) = microfilariae in blood at night; coincides with the feeding pattern of arthropod host (mosquito) Microfilariae  Vector species: Aedes, Anopheles, or Culex 39 5. Know the pathogenesis and epidemiology of Brugia malayi  Epidemiology  120 million people are infected worldwide  Burden is high in tropics/subtropics of Asia, Africa, Western Pacific & parts of Caribbean, and S. America  Endemic in Brazil, China, India, Haiti, Dominican Republic, Guyana, Brazil  US – Charleston, SC last known case of lymphatic filariasis (early 1920s) 40 5. Know the pathogenesis and epidemiology of Brugia malayi  Lymphatic Filariasis  Transmission -> Bite of mosquito transmits infective larvae (L3 stage) into the skin  Infective larvae penetrate the skin and migrate through the subcutaneous tissues, eventually reaching the lymphatic vessels 3 mo – 1 yr Lifespan 5-10 y  Larvae mature into Adult worms over several months in the lymphatic vessels  Microfilariae circulate in the bloodstream 41 5. Know the pathogenesis and epidemiology of Brugia malayi SYMPTOMS DIAGNOSIS  Acute Phase (8-12 months after exposure): Fever, Chills, Myalgia, Lymphadenitis; Area affected large, red, tender lump, secondary bacterial infections develop as lymph flow is impaired  Chronic Phase (Repeats over weeks to months): Elephantiasis- Thickening and hypertrophy of tissues, usually in extremities  Sheathed microfilariae in the blood (Giemsa stain) microscopy  PCR-based assays can detect filarial DNA 42 5. Know the pathogenesis and epidemiology of Onchocerca volvulus  Onchocerca volvulus (Blinding Filaria)  Adult female 34-50 cm (l); male 19-42 cm (l)  Adults live coiled around one another within capsules forming skin nodules  Causes onchocerciasis (river blindness)  The second-leading cause of blindness due to infection  One of the 20 neglected tropical diseases listed by the WHO Unsheathed Microfilariae in subcutaneous tissues 43 5. Know the pathogenesis and epidemiology of Onchocerca volvulus  Epidemiology 37 million people are infected globally 270,000 are blind and 500,000 have visual impairment Mainly in sub-Saharan Africa  Those living near rivers with blackflies, longterm missionaries, Peace Corps workers, and field researchers are at risk 44 5. Know the pathogenesis and epidemiology of Onchocerca volvulus  Onchocerciasis (River Blindness)  Transmission -> Bite of blackfly L3 larvae enter bite wound and penetrate subcutaneous tissue to develop into adults 10-20 mo Adults Fertilized eggs Unsheathed Microfilariae (3-12 wks) migrate up to 2 yrs Lifespan 8-15 y Adults = reside in fibrotic nodules 1 female 1,300-1,900 microfilariae per day for 9-11 yrs  Unsheathed Microfilariae = migrate in subcutaneous tissues (skin); common site of migration is the eye Progeny lifespan 2y 45 5. Know the pathogenesis and epidemiology of Onchocerca volvulus SYMPTOMS  Skin Nodules: Painless, firm nodules containing adult worms and larvae, typically 1-3 cm in diameter.  Skin Manifestations: Itchy skin rash due to the inflammatory response to dying parasites, leading to wrinkles, large skin folds  Eye Complications: An invasion of the eye can lead to river blindness, characterized by conditions such as keratitis, iritis, and chorioretinitis, which results in reduced vision or DIAGNOSIS Eye  1-2 mg Skin Snip, place in saline microfilariae emerge  Skin nodules: Remove nodule and examine for adult worms -> PCR  Eye infections – slit-lamp exam for microfilariae or lesions 46 Lecturio videos and questions 1. Introduction to Helminths (https://nova.lecturio.com/#/lecture/c/8286/38710, 2:28 mins, 2 questions) 2. Ascaris lumbricoides (Nematodes) (https://nova.lecturio.com/#/lecture/c/8286/38712, 8:48 mins, 5 questions) 3. Nematodes (Roundworms) (https://nova.lecturio.com/#/lecture/s/6434/39114, 2:57 min; 2 questions) 4. Hookworms (Nematodes) (https://nova.lecturio.com/#/lecture/c/8286/38714, 4:54 mins; 3 questions) 5. Nematodes (Roundworms) and Cestodes (Flatworms) (https://nova.lecturio.com/#/lecture/c/6434/39114, 2:57 mins, 2 questions) 6. Trichinella spiralis and Trichinosis (Nematodes) (https://nova.lecturio.com/#/lecture/c/8286/38716, 4:29 mins, 3 questions) 47