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Lecture 5: Emerging Parasitic Helminths Part 2: Tissue Nematodes

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Readings-Nematodes • Ch. 11 (pp. 290, 291-93, 295 [box 11.1], 304 [box 11.2]) • Lecture 5: Emerging Parasitic Ch.14 (p. 375, 367 [table 14.1]) Helminths part 2: Tissue Nematodes Matt Tucker, M.S., MSPH [email protected] HSC4933 Emerging Infectious Diseases HSC4933. Emerging Infectious Diseases 2 Monsters Inside Me Learning Objectives • Toxocariasis, larva migrans (Toxocara canis, dog hookworm): • Understand how visceral larval migrans, cutaneous larval migrans, and ocular larval migrans can occur Background: • Know basic attributes of tissue nematodes and be able to distinguish http://animal.discovery.com/invertebrates/monsters-inside- these nematodes from each other and also from other types of me/toxocariasis-toxocara-roundworm/ nematodes • Understand life cycles of tissue nematodes, noting similarities and Videos: http://animal.discovery.com/videos/monsters-inside- significant difference me-toxocariasis.html • Know infective stages, various hosts involved in a particular cycle • Be familiar with diagnostic criteria, epidemiology, pathogenicity, http://animal.discovery.com/videos/monsters-inside-me- &treatment toxocara-parasite.html • Identify locations in world where certain parasites exist • Note drugs (always available) that are used to treat parasites • Describe factors of tissue nematodes that can make them emerging infectious diseases • Be familiar with Dracunculiasis and status of eradication HSC4933. Emerging Infectious Diseases 3 HSC4933. Emerging Infectious Diseases 4 Lecture 5: On the Menu Problems with other hookworms • Cutaneous larva migrans or Visceral Tissue Nematodes larva migrans • Hookworms of other animals • Cutaneous Larva Migrans frequently fail to penetrate the human dermis (and beyond). • Visceral Larva Migrans – Ancylostoma braziliense (most common- in Gulf Coast and tropics), • Gnathostoma spp. Ancylostoma caninum, Ancylostoma “creeping eruption” ceylanicum, • Trichinella spiralis • They migrate through the epidermis leaving typical tracks • Dracunculus medinensis • Eosinophilic enteritis-emerging problem in Australia HSC4933. Emerging Infectious Diseases 5 HSC4933. Emerging Infectious Diseases 6 1 Visceral Larva Migrans (VLM) • Caused by juveniles of several species of nematodes that gain entry to improper host • Larvae begin tissue migration, but become arrested and migrate throughout body • Toxocara canis, Toxocara cati • Ascaris suum No maturation to adults http://www.cdc.gov/mmwr/preview/mmwrht ml/mm5649a2.htm HSC4933. Emerging Infectious Diseases 7 HSC4933. Emerging Infectious Diseases 8 Toxocara canis T. canis life cycle • Dog roundworm – Transmitted maternal-fetal • Infects very high % puppies • Distributed worldwide • Worms release massive amounts of eggs that are environmentally stable • Causes VLM, OLM • Albendazole+inflammatory drugs HSC4933. Emerging Infectious Diseases 9 HSC4933. Emerging Infectious Diseases 10 Diseases Gnathostoma spp. • VLM – Larvae invade multiple tissues (liver, heart, lungs, • G. spinigerum brain, muscle) and cause fever, anorexia, weight • Transmitted in Asia, especially Thailand and loss, cough, rashes, hepatosplenomegaly Japan; recently emerged as an important – Death can occur rarely, by severe cardiac, human parasite in Mexico pulmonary or neurologic involvement. • Humans infected by eating undercooked • OLM fish or poultry containing third-stage – Larvae produce various ophthalmologic lesions, larvae, or by drinking water containing sometimes misdiagnosed as retinoblastoma infected copepods – Often occurs in older children or young adults, • Disease due to migrating, immature worms with only rare eosinophilia or visceral manifestations. • Emerging imported infections • Dx: For both VLM and OLM, the diagnosis rests • Adults and larvae have numerous spines for on clinical signs, history of exposure to puppies, encysting in host tissue laboratory findings, and detection of antibodies Note collar of spines of to Toxocara. adult worm, used for – Remember, no eggs in stool sticking in host tissue HSC4933. Emerging Infectious Diseases 11 HSC4933. Emerging Infectious Diseases 12 2 Gnathostoma spp. Gnathostomiasis and Tx • Within 24-48 h of ingestion of larvae, patients may develop fever, vomiting, epigastric pain. • Migration in the subcutaneous tissues causes intermittent, migratory, painful, pruritic swellings (cutaneous larva migrans). • Migration to other tissues (visceral larva migrans) can result in ocular involvement, more serious manifestations such as eosinophilic meningitis with myeloencephalitis. • Removal and identification of the worm is both diagnostic and therapeutic. • Tx: Surgical removal or combination with albendazole or ivermectin HSC4933. Emerging Infectious Diseases 13 HSC4933. Emerging Infectious Diseases 14 Mexico: An emerging problem Trichinosis (Trichinellosis) • First case of clinical • Zoonotic infections gnathostomiasis was reported in • Humans are accidental, dead-end hosts Mexico in 1970 • Multiple species of Trichinella infect humans • Over 1,000 cases reported along depending on climate and reservoir hosts Gulf/Pacific Coasts from 1980- • T. spiralis, T. pseudospiralis, T. nativa, T. nelsoni, 1996 T. britovi – 1993-1997: 98 cases in Acapulco • T. spiralis is comopoliltan, most pathogenic • Linked to eating ceviche • Emerging in China, Russia, other European • Mass production and commercial countries distribution of tilapia has been – In 2008, morbidity due to trichinellosis doubled implicated in Russia: 312 cases in 2008 vs. 155 in 2007. – 779 human cases in EU Member States during 2007 HSC4933. Emerging Infectious Diseases 15 HSC4933. Emerging Infectious Diseases 16 Various Life Cycles of Trichinella spp. T. spiralis Life Cycle Domestic cycle • Domestic pigs are considered the dominant reservoir host, but there are many different typical hosts throughout the world Infection is maintained Sylvatic (wild animal) cycles primarily in rats and other rodents which may • Temperate regions (carrion and live be eaten by other prey): pig, wild boar, horse, dog, animals such as pigs and bear, fox bears. • Arctic regions (carcasses): polar bear, walrus, wolf, fox • Tropical regions (carcasses): wharthog, hyena HSC4933. Emerging Infectious Diseases 17 18 3 T. spiralis Distribution Nurse Cell Complex • Larvae encysted in striated muscle • Subversion and redirection of host cell activities – Alteration of gene expression of host cell from contractile fiber to cell that nourishes worm – Synthesis of collagen by neighboring fibroblasts encloses nurse cell • Juveniles absorb nutrients while in nurse cell and increase 1mm in 4-8 weeks, infective to hosts • Juveniles enter developmental arrest and live for years • Emerging in China, Russia, other European countries • Calcification of nurse cell and worms by host – In 2008, morbidity due to trichinellosis doubled in Russia: 312 cases in 2008 reactions vs. 155 in 2007. • 779 human cases in EU Member States during 2007 • Lithuania, June 2009: outbreak due to wild boar meat sausages -affected 107 people HSC4933. Emerging Infectious Diseases 20 Disease Trichinosis Dx and Tx • The first few days of the infection • Dx based on symptoms of stage of life cycle and are characterized by larvae in feces, blood, other secretions gastroenteritis associated with diarrhea, abdominal pain, • Muscle biopsy for larvae, PCR, antibody vomiting. detection • Pathology is due to migrating • Steroids are used for infections with severe newborn larvae as they randomly symptoms penetrate cells (e.g., brain, liver, • Mebendazole or albendazole can be used to kidney, heart) in their search for treat infections in the intestines striated skeletal muscle cells. • Treatment should begin as soon as possible and – Fever and myalgia, bilateral the decision to treat is based upon symptoms, Immature larva periorbital edema, and petechial exposure to raw or undercooked meat, and from biopsy hemorrhage laboratory test results. • Heavy infection results in – No specific treatment for trichinosis once the generalized edema, larvae have invaded the muscles cardiomyopathies and CNS abnormalities HSC4933. Emerging Infectious Diseases 21 HSC4933. Emerging Infectious Diseases 22 Prevention Outbreak: Crazy turtles • In July 2008, four teaching hospitals in northern Taiwan reported 8 patients in • Curing (salting), drying, smoking, or 2 groups with fever, myalgias, and eosinophilia of unknown cause developed microwaving meat does not consistently kill after they shared a common food source in May 2008. – Group A: 20 Taiwanese, participated in a festive meal at a Japanese food restaurant, and infective worms. were served raw meat, blood, liver, and eggs of 3 of 5 soft-shelled turtles – Group B: A group of 3 Japanese customers was served the other 2 turtles • Cook meat products until the juices run clear • Extensive serologic testing for helminths by ELISA, hits against Trichinella spp. or to an internal temperature of 170⁰F. • The incubation period, clinical features, and laboratory findings in this outbreak were similar to those of other reported trichinosis outbreaks • Freeze pork less than 6 inches thick for 20 days associated with eating mammals – T. papuae and T. zimbabwensis are the most likely parasites causing this outbreak at 5⁰F to kill any worms. because of their ability to infect mammals and reptiles. • Serum specimens from 6 of the 8 case-patients reacted most strongly to the • Cook wild game meat thoroughly-harder to kill 53-kDa recombinant protein of T. papuae. worms than in pork. • Significance: – Not yet determined how
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