Lecture 20: Nematoda PDF

Nematodes… are acoelomates are coelomates are pseudocoelomates have muscles that run to nerves have nerves that run to muscles lack a mouth lack an anus possess a mouth possess an anus are gonochoristic...

Nematodes… are acoelomates are coelomates are pseudocoelomates have muscles that run to nerves have nerves that run to muscles lack a mouth lack an anus possess a mouth possess an anus are gonochoristic are hermaphroditic must moult to grow don’t moult  human cow seal duck bear marine sh dolphin squid krill sheep pig fi  L3 L1 adults L2 L4 eggs  Lecture 19 Nematoda Phylum Nematoda Trichinella spiralis (1.6 mm) Placentonema gigantissima (10 m) human intestine sperm whale placenta © 2024 K. Jensen Dioctophyme renale, giant kidney worm This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Phylum Nematoda—male reproductive system copulatory bursa and 2 spicules male organs female organs ovary, etc. testis, etc. MALE single spicule (no bursa) © 2024 K. Jensen FEMALE This content is protected and may not be shared, uploaded, or distributed. Source: Foundations of Parasitology  Lecture 19 Nematoda Basic nematode life cycle 4th molt 3rd molt 2nd molt 1st molt © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda + Contracaecum © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda + Contracaecum © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 1 Medical parasitology Recent estimates of number of people infected with parasites in the world No. of cases ascariasis 1 billion hookworms 470 million whipworms >450 million schistosomes 230 million malaria 249 million food-borne trematodiasis 75 million lymphatic lariasis 120 million cutaneous leishmaniasis 4.1 million cysticercosis (Taenia) 2.6 million Chagas’ disease 7 million = untold suffering and death in the world today Source of data: © 2024 K. Jensen WHO, CDC, etc. This content is protected and may not be shared, uploaded, or distributed. fi  Lecture 20 Nematoda Ascariasis One of the most common human parasitic infections 1 billion people infected globally 60,000 people die from ascariasis annually Endemic mostly tropical and subtropical countries (e.g., Sub-Saharan Africa, Latin America, China, & East Asia) Disease in children & adults in areas with poor sanitation and hygiene Infected children are nutritionally and physically impaired Common in areas where night soil is used as fertilizer Higher risk of infection in non-endemic areas due to increased rate of migration and travel © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. Source: https://www.ncbi.nlm.nih.gov/books/NBK430796/  Lecture 20 Nematoda Ascaris lumbricoides DH: humans Ascaris suum 3 anterior lips DH: pigs zoonotic large worms (up to 50 cm) huge nos. eggs produced eggs very resistant (survive up to 10 yrs in environment) egg with mammillated outer layer © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. intestine of infected pig  Lecture 20 Nematoda Life cycle of Ascaris lumbricoides (& A. suum) Ascaris lumbricoides DH: humans infective stage monoxenous Ascaris suum 2 DH: pigs zoonotic (L1–L2 in egg) Juveniles migrate through lungs Adults in small intestine eggs diagnostic & infective stage © 2024 K. Jensen diagnostic stage This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Details of life cycle of Ascaris suum (also A. lumbricoides) 1. adults in small intestine 13. in lungs, L2 molts to L3, L3 molts to L4 (damage!) 1 2. eggs passed in feces 4th molt 8 14. L4 break into alveoli & migrate up trachea 3. eggs with mammillated layer 16 9 15. L4 cause irritation, get 4. eggs survive 4–10 years coughed up & swallowed (even in formalin) 10 2 16. nal molt of L4 to adult 15 3rd molt 2nd molt 11 5. 9–40 days for L1 to develop 14 13 12 7 6. L1 molts to L2 in egg De nitive host 7. eggs with L2 ingested zoonotic 8. L2 hatches after passing through stomach 9. L2 enters venues of hepatic portal vein monoxenous 3 10. L2 through liver eggs diagnostic 11. L2 into heart & infective stage 4 12. L2 through pulmonary circulation 6 1st molt to lungs © 2024 K. Jensen 5 This content is protected and may not be shared, uploaded, or distributed. fi fi  Lecture 20 Nematoda Soil Transmitted Helminths (STH) Ascaris lumbricoides global prevalence Trichuris trichiura in tropical/subtropical regions associated with poor sanitation Hookworms Strongyloides stercoralis © 2024 K. Jensen (Ancylostoma & Necator) Source: Jourdan, P. M., P. H. L. Lamberton, A. Fenwick, and D. G. Addiss. 2018. Soil-transmitted helminth This content is protected and may not be shared, uploaded, or distributed. infections. The Lancet 391: 252–265. doi: 10.1016/S0140-6736(17)31930-X  Lecture 20 Nematoda Symptoms, pathology & treatment of Ascaris Etiological agents of Ascariasis Most ( rst) infections asymptomatic. Juveniles (pathology if 100s of larvae migrating & prior exposure): - migration of L3/L4s causes hemorrhage in lungs - in high intensity infections, pools of blood - pneumonia-like symptoms - allergic airway disease; granulomas in liver - can be deadly Adults: - can block intestine in high intensity infections - bite intestine with lips causing damage to mucosa - can suck blood resulting in malnutrition - impaired absorption of proteins, lactose, vitamins Treatment: albendazole, mebendazole, etc. © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. fi  Lecture 20 Nematoda Murder by Ascaris © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda + Contracaecum © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda monoxenous Toxocara canis + foxes, coyotes, wolves Toxocara cati juveniles of both species are zoonotic Juveniles are etiological agents of humans Toxocariasis (= Visceral Larval Migrans) Worldwide (France, Austria, India, Japan, Korea, China, USA, and Brazil, etc.) 1° infective stage predominantly affects children in tropical and subtropical regions hundreds of clinical cases in US each year (L1–L3 in egg) © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Visceral Larval Migrans (VLM) (toxocariasis) in humans PROBLEM: stray dogs & cats contaminating soil with eggs e.g., prevalence of Toxocara in US: 7% in dogs (2009); 33% in cats (2001) embryonated eggs ingested when coming in contact with contaminated soil; 1° children © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Visceral Larval Migrans (VLM) (toxocariasis) in humans Symptoms & pathology (if with complications) - migrate to various organs; fever - Ocular larval migrans (OLM): damage to eyes, blindness - Visceral larva migrans (VLM): hepatomegaly (liver); pulmonary symptoms (lungs) - Neurotoxocariasis: neurological, meningoencephalitis (brain) Treatment: albendazole, mebendazole, ivermectin © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Visceral Larval Migrans (VLM) (toxocariasis) in humans Toxocara infection in the retina. Visceral larval migrans blinds at least 70 children in the US each year. Toxacara sp. in the human eye as a result of VLM Imaging section through the torso of a patient with VLM, note the migration tracts and larvae in liver (left). VLM tracts under the skin of a child (right). © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda monoxenous Baylisascaris procyonis juveniles are zoonotic Juveniles are etiological agents of Baylisascariasis in humans (i.e., ocular, visceral, or neural larval migrans) Worldwide, but 1° US and Canada Prevalence in raccoons in Northeast, Midwest, and West Coast sometimes >80% Most documented human cases in California, (L1–L3 in egg) Washington, Minnesota, New York 1° infective stage © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda monoxenous Baylisascaris procyonis juveniles are zoonotic Juveniles are etiological agents of Baylisascariasis in humans (i.e., ocular, visceral, or neural larval migrans) 62°C (L1–L3 in egg) 1° infective stage © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. L.A. County Michigan  Lecture 20 Nematoda + Contracaecum © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Hookworms juveniles are zoonotic 1 pr 3 prs 2 prs cutting teeth teeth plates Ancylostoma caninum Ancylostoma duodenale Necator americanus juveniles are zoonotic 1 pr teeth Ancylostoma brasiliense posterior of male © 2024 K. Jensen with copulatory bursa This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda Human hookworms juveniles are zoonotic 1 pr 3 prs 2 prs cutting teeth teeth plates Ancylostoma caninum Ancylostoma duodenale Necator americanus juveniles are zoonotic 1 pr teeth Ancylostoma brasiliense © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda History of hookworm disease “The disease induced by the hookworm…was never suspected to be a disease at all. The people who had it were merely supposed to be lazy, and were therefore despised and made fun of, when they should have been pitied.” Mark Twain (1910) Rural hookworm treatment center in Tennessee (1920’s) Mobile screening and dispensary worker, Waller County, Texas © 2024 K. Jensen (1920) operated by the Rockefeller Sanitary Commission This content is protected and may not be shared, uploaded, or distributed.  Lecture 20 Nematoda History of hookworm disease “As it was when I rst saw it, so it is now, one of the most evil of infections. Not with dramatic pathology as are lariasis, or schistosomiasis, but with damage silent and insidious. Now that malaria is being pushed back hookworm remains the great infection of mankind. In my view it outranks all other worm infections of man combined…in its production, frequently unrealized, of human misery, debility, and inef ciency in the tropics.” Norman Stoll (1962) © 2024 K. Jensen Source: Stoll, N. R. 1962. On endemic hookworm, where do we stand today? Experimental This content is protected and may not be shared, uploaded, or distributed. Parasitology 12: 241–252. doi: https://doi.org/10.1016/0014-4894(62)90072-3 fi fi fi  Lecture 20 Nematoda Hookworm disease One of the major groups of soil-transmitted helminths (STH) ~450 million people infected globally (2016) ~160 million experience illness Highest prevalence in sub-Saharan Africa and eastern Asia Accounts for more than US$100 billion in global economic losses Striking relationship between hookworm prevalence and low socioeconomic status Concentration among the world’s poorest 2.7 billion people who live on less than $2 a day = one of the reasons for neglected status © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. Source: https://www.ncbi.nlm.nih.gov/books/NBK430796/  Lecture 20 Nematoda + Ancylostoma ceylanicum Ancylostoma duodenale & Necator americanus Etiological agents of Hookworm disease in humans diagnostic stage monoxenous (embryonated; blastomeres in non-infective cleavage at the 8- or 16-cell stage) Juveniles migrate Diagnosis: through lungs eggs (& blood) in feces infective Adults in small intestine infective stage © 2024 K. Jensen Source: Loukas, A., P. J. Hotez, D. Diemert, M. Yazdanbakhsh, J. S. Mccarthy, R. Correa-Oliveira, J. Croese, and J. M. This content is protected and may not be shared, uploaded, or distributed. Bethony. 2016. Hookworm infection. Nature Reviews Disease Primers 2: 16088. doi: 10.1038/nrdp.2016.88  Lecture 20 Nematoda + Ancylostoma ceylanicum Ancylostoma duodenale & Necator americanus plug of mucosal tissue in Etiological agents of buccal capsule Hookworm disease in humans Section through adult hookworm attached to intestine Stage of disease 1. Penetration L3 2. Migration of L3 in lungs Summary effects because if infection with adults 3. Intestinal infections with adults - adults use teeth to breach intestinal mucosa - secrete an anticoagulant & suck blood - wasteful feeders (A. duodenale 0.25 ml blood/day/worm) - anemia, iron de ciency - 150–500 worms: mental de ciency & protein malnutrition - 500–1,000 worms: deadly if untreated © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. fi fi  Lecture 20 Nematoda + Ancylostoma ceylanicum Ancylostoma duodenale & Necator americanus Stage Symptoms Pathology 1. Penetration of L3 - ground itch at site of penetration - minute wounds; 2° bacterial infections; red papules in sensitized hosts 2. Migration of L3 in lungs - dry cough; sore throat; hoarseness - hemorrhage of lung tissue** - bloody sputum - broblast in ltration 3. Intestinal infections with adults At all levels of infection: PICA (craving scratchy substances, e.g., chalk, soil, etc.) Light (500 worms) - profound anemia - heart invaded by connective tissue - exhaustion - malnutrition © 2024 K. Jensen This content is protected and may not be shared, uploaded, or distributed. **smaller than Ascaris juveniles, thus damage to lungs is less severe fi fl fi