M3

• Unit IIB:Extra-Intestinal & Zoonotic Nematodes (General characteristics, Mode of Transmission,Clinical Significance, Life Cycle, Epidemiology, Prevention & Control )
• Learning Objectives


  • Identify correctly and describe the characteristics and diagnostic features of parasites of clinical importance
  • Discuss the pathology that the clinically significant parasites cause and the common signs, symptoms and manifestation of infected human
  • Describe accurately the life cycle of the pathogenic parasites, their infective stages to humans and their mode of transmission
  • Explain the importance of prevention and control of parasitic infections

  
• Topic Outline

  • Extra-Intestinal Nematodes
  • Zoonotic Nematodes
• Extra-Intestinal Nematodes

  • Tissue: Trichinella spiralis, Dracunculus medinensis
  • Lymphatics: Wuchereria bancrofti, Brugia malayi
  • Subcutaneous: Loa loa, Onchocerca volvulus, Mansonella spp. (perstans, ozzardi, streptocerca)

  
• Zoonotic Nematodes

  • Angiostrongylus cantonensis
  • Anisakis spp.
  • Toxocara cani
  • Toxocara cati
  • Ancylostoma braziliense
  • Ancylostoma caninum
• TAXONOMIC CLASSIFICATION

  • METAZOANS
  • PHYLUM NEMATHELMINTHES
  • PHYLUM PLATYHELMINTHES
  • CLASS TREMATODA
  • CLASS CESTODA
  • CLASS NEMATODA
  • CYCLOPHYLLIDEA
  • PSEUDOPHYLLIDEA
  • SUB-CLASS SECERNENTIA
  • SUB-CLASS ADENOPHOREA
  • INTESTINAL, LIVER, LUNG & BLOOD FLUKES
  • "TCT"
• Trichinella spiralis


  Also known as "Muscle worm", "Garbage worm", "Pork muscle roundworm, "Trichina worm". Causes Trichinosis,Trichinellosis. Intestinal and Tissue nematode. Adults: small intestine, Encysted larva: striated muscles (cardiac & skeletal) enclosed or being enclosed in a cyst

  
• Trichinella spiralis encysted larva


  • Spear-like, burrowing anterior tip
  • Digestive tract (same w/ adults)
  • Undeveloped reproductive organs

  
• Trichinella spiralis life cycle

  1. Infective & Diagnostic stage: encysted larvae

  2. D.H & I.H: humans and other carnivores & omnivores

  3. Dead end-host: Humans

  
• Trichinella spiralis pathogenesis

  • Enteric phase (acute food poisoning, including diarrhea or constipation, vomiting, abdominal cramps, malaise, and nausea)
  • Invasion phase (eosinophilia, histamines, tissue edema)
  • Convalescent phase

  
• Trichinella spiralis cardinal signs

  • Severe myalgia, periorbital edema, and eosinophilia
• Trichinella spiralis diagnosis

  Muscle biopsy- definitive method, Identification of the encysted larva
• Trichinella spiralis prevention, treatment & epidemiology

  • Prevention: Heating (77°C) and freezing (-15°C for 20 days or –30°C for six days)
  • Treatment: mebendazole, albendazole
  • Epidemiology: 10,000 cases reported each year, 0.2% resulting in mortality. No recorded case in the Philippines.

  
• Dracunculus medinensis


  Also known as "Guinea worm, Fiery serpent of the Israelites, dragon worm". Longest nematode of man (840 mm long by 1.5 mm wide). Causes Dracontiasis, Dracunculiasis. Habitat: body cavities & subcutaneous tissues

  
• Dracunculus medinensis larvae

  • First stage or rhabditiform larvae (L1) - diagnostic stage
  • Third stage larva (L3) - infective stage

  
• Dracunculus medinensis adult


  • One of the longest nematodes, tail makes up about one third of the body length and culminates in a point, Female: 840 mm long by 1.5 mm wide, possesses a prominent blunt, rounded anterior end
• Dracunculus medinensis life cycle

  1. Definitive: human & dogs

  2. Intermediate Host: cyclops/copepods

  3. MOT: ingestion of infected copepods thru contaminated water

  4. Infective stage: Third stage larva (L3)

  5. Diagnostic stage: First stage larva (L1)

  
• Dracunculus medinensis pathogenesis

  Guinea Worm Infection: Dracunculosis, Dracunculiasis, painful ulcer

  
• Dracunculus medinensis diagnosis

  Observing infected ulcers, Induced rupture of the infected ulcers by immersing in cool water
• Dracunculus medinensis treatment

  Total worm removal
• Filarial nematodes

  • Lymphatic filariasis (Wuchereria bancrofti, Brugia malayi, and Brugia timori)
  • Subcutaneous (Loa loa, Mansonella streptocerca Onchocerca volvulus)
  • Serous cavity (Mansonella)
• Wuchereria bancrofti

  Also known as "Bancroft's filarial worm". Causes Bancroftian filariasis. Habitat: Lower lymphatics. Vector: Mosquitoes (Aedes, Culex, Anopheles and Mansonia). MOT: Skin inoculation. Specimen: Blood. Periodicity: Nocturnal periodicity (8PM-4AM). Infective stage: 3rd stage larva (L3)

  
• Wuchereria bancrofti adult


  • Creamy white, long, and filiform in shape, male: 20 to 40 mm in length, female: 80 to 100 mm, similar to Brugia malayi adults
• Wuchereria bancrofti microfilaria

  • 270 to 290 µm, enclosed in a hyaline sheath, dark-staining nuclei that does not reach the tail's end, "Graceful appearance"
• Brugia malayi


  Also known as "Malayan Filaria". Causes Malayan filariasis. Habitat: Upper lymphatics. Vector: Mosquito (Mansonia). MOT: Skin inoculation. Specimen: Blood. Periodicity: Nocturnal sub-periodicity. Infective stage: 3rd stage larva (L3)

  
• Brugia malayi microfilaria

  • 111 to 230 µm in length, enclosed in a hyaline sheath, dark-staining nuclei with two nuclei at the tip of the tail, "Kinky appearance"
• Parasite Life Cycle Comparison

  • Wuchereria bancrofti: Nocturnal periodicity, Mosquitoes (Aedes, Culex, Anopheles), D.H: Humans, I.H: Mosquito, Skin inoculation, Lower lymphatics
  • Brugia malayi: Nocturnal sub-periodicity, Mosquitoes (Mansonia spp), Upper lymphatics

  
• Clinical Spectrum of Lymphatic Filariasis

  • Asymptomatic microfilaremia
  • Acute dermatolymphangioadenitis (ADLA)
  • Acute filarial lymphangitis (AFL)
  • Lymphedema (elephantiasis)
  • Genitourinary lesions (e.g., hydrocele)
  • Tropical pulmonary eosinophilia (TPE)
• Asymptomatic microfilaremia

  Individuals with thousands to millions of vigorously motile microfilariae in the peripheral blood often show no obvious clinical signs of disease
• Acute dermatolymphangioadenitis (ADLA)


  Most common acute manifestation, characterized by localized pain, lymphadenitis, lymphangitis, cellulitis and local warmth, with or without systemic manifestations
• Acute filarial lymphangitis (AFL)


  Lymphangitis that progresses distally along the lymphatic vessel, "palpable cord"
• Stages of Lymphedema

  • Stage 1: swelling increases during the day but is reversible once the patient lies flat in bed
  • Stage 2: swelling is no longer reversible overnight, and the patient may still experience acute attacks
  • Stage 3: presence of shallow skin folds
  • Stage 4: knobs present in the affected area
  • Stage 5: deep skin folds (opens only manually)
  • Stage 6: mossy lesions are present (leak translucent fluid)
  • Stage 7: debilitated state (foul smelling)
• Genitourinary lesions - Hydrocele

  Results in the obstruction of the lymphatics of the tunica vaginalis, clear/straw colored fluid, most common in Bancroftian filariasis

  
• Genitourinary lesions - Chylocele

  Hydrocele fluid with a "milky appearance", lymphatics in the kidney may rapture producing chyluria (milky urine)
• Tropical pulmonary eosinophilia (TPE)


  Occult filariasis (no clinical manifestations), microfilaria are found in the tissues not in the blood, characterized by paroxysmal nocturnal cough, hypereosinophilia

  
• Lymphatic Filariasis Treatment and Prevention

  • Treatment: Diethylcarbamazine (DEC)- drug of choice
  • Prevention: mosquito nets, repellants, preventive chemotherapy, hygiene education programs

  
• Epidemiology of Lymphatic Filariasis: 120 million people worldwide, 90% (W. bancrofti) other 10% (B. malayi & similar parasites)
• Loa loa

  Also known as "Eye worm". Causes Loiasis (Calabar or Fugitive swelling). Habitat: Subcutaneous tissues. Vector: Chrysops fly/Deerfly/Mango fly. MOT: Skin Inoculation. Specimen: Blood. Periodicity: Diurnal (10:15 AM and 2:15 PM). Infective stage: 3rd stage larva

  
• Loa loa microfilariae


  • Sheathed, distinct continuous row of nuclei that extends to tip of tail
• Loiasis pathogenesis and clinical manifestations

  Pruritus or itchiness and localized pain, Temporary inflammatory swellings (Calabar or Fugitive swelling)- due to parasite migration