PARA LEC

• Toxocara canis

  Dog roundworm
• Toxocara cati

  Cat roundworm
• Tissue nematodes

  • Toxocara species
  • Dracunculus medinensis
  • Parastrongylus cantonensis
  • Anisakis
• Toxocariasis is a zoonotic disease from stray dogs and cats
• Diagnostic Stage of Toxocara species


  Larvae encysted in tissues
• Hosts of Toxocara species

  • Accidental Host: Humans
  • Paratenic Host: Rabbits and small mammals
  • Definitive Hosts: Dogs or cats
• Infective Stage of Toxocara species

  1. Embryonated ova

  2. Encysted larvae in small mammals like rabbit
• Pathogenesis and Clinical Manifestations of Toxocara species

  1. Visceral Larva Migrans (VLM)

  2. CNS: Neurological Toxocariasis

  3. Ocular Larva Migrans (OLM)

  4. Covert Toxocariasis (CoTOX)
• Reactivation of encysted eggs in female dogs

  Transplacental or transmammary transmission
• Common clinical manifestations of Toxocara species include seizures, encephalitis, pneumonia, respiratory failure, hepatomegaly, and more
• Diagnosis of Toxocara species involves tissue biopsy demonstrating larva
• Common among children 5-10 years old


  • Unilateral visual impairment and strabismus
• Retinal Invasion


  • Most serious consequence
• Treatment

  1. Most patients recover without therapy

  2. If therapy is warranted: Albendazole or Mebendazole PLUS anti-inflammatory drug (Steroids) for those with CNS, cardiac, or lung complications

  3. More difficult for Ocular Toxocariasis to prevent progressive damage to the eye
• Prevention and Control

  1. Control and capture of stray dogs and cats

  2. Cleaning up feces from soil and pavements

  3. Closing of potentially contaminated areas to animals and children

  4. Gardens should be fenced to prevent fecal contamination by dogs and cats

  5. Vegetables gathered from possible contaminated gardens should be washed thoroughly

  6. Avoidance of consumption of raw or undercooked meat of potentially infected animal

  7. Hand washing at all times
• Covert Toxocariasis (CoTOX)


  • Less specific syndrome or may be asymptomatic
• Prevention and Control

  1. Strategic antihelminthic treatment of dogs and cats

  2. Puppies: start 2-3 weeks of age, repeated every 2 weeks until 12 weeks age

  3. Adult: treated every 6 months

  4. Female: after each estrus cycle
• Dracunculus medinensis infection has been recorded as early as the 15th BC
• Dracunculus medinensis, also known as Guinea Worm, is the longest nematode known to cause human parasitism
• Diagnosis


  1. Tissue Biopsy demonstrating larva

  2. ELISA test for IgG

  3. PCR

  4. Stool exam to demonstrate eggs has no role in the diagnosis of human toxocariasis
• Definitive Hosts

  • Humans
  • Wolves
  • Dogs
  • Horses
  • Cows
  • Leopards
  • Monkeys
  • Baboons
• Diagnostic Stage


  • Female adult worm in the subcutaneous tissue, rhabditiform larvae
• Intermediate Host

  • Cyclops copepods
• Pathogenesis and Clinical Manifestations


  Details on the symptoms and effects of the infection
• Infective Stage

  • Third Stage Larva (L3) within the Cyclops copepods
• Treatment


  Manual Removal of Adult Female Worm by submerging the affected body part in water to coax the worm out, cleaning the site, applying slight pressure, and slowly pulling out the worm
• Diagnosis

  1. Recovery of adult worm from the blister

  2. Recovery of rhabditiform larvae

  3. Fluid discharged by the worm
• Hosts of Parastrongylus cantonensis

  • Definitive Host: Rats
  • Intermediate Host: Snails or Slugs
  • Paratenic Host: Crabs, freshwater shrimps
  • Accidental Host: Humans
• First human infection documented by Nomura and Lin in Taiwan


  1945
• Worm extraction

  1. Water is used to help coax the worm out

  2. The site is cleaned thoroughly

  3. Slight pressure is applied to the worm as it is slowly pulled out of the wound

  4. To avoid breaking the worm, pulling should stop when resistance is met

  5. Full extraction of the female guinea worm usually takes several days
• Parastrongylus cantonensis infection documented in at least 30 countries
• Biology of Adult Parastrongylus cantonensis

  • Male: 16-22mm by 0.25-0.35mm, well-developed caudal bursa
  • Female: 19-33mm by 0.28-0.50mm, lay 15,000 eggs per day
• Biology of Ova Parastrongylus cantonensis

  • 46-48um by 68-74um, elongated ovoidal eggs with delicate hyaline shells, unembryonated when oviposited
• Biology of Larva Parastrongylus cantonensis

  • Rhabditiform Larva found in lungs of rodents, distinct small knob near the tip of the tail
  • Filariform Larva with two well-developed chitinous rods below the buccal cavity, rods have expanded knob-like tips
• Pathogenesis and Clinical Manifestations

  1. Eosinophilic meningoencephalitis: Brain is the primary site of infection, symptoms include headache, stiffness of neck, paresthesia, vomiting, fever, nausea, blurred vision, diplopia, myalgia, fatigue, confusion, incoherence, disorientation, memory lapses, coma, intraocular hemorrhage, blindness

  2. Eosinophilic Enteritis: eosinophilic inflammation of the mesenteric arterioles of the ileocecal region mimicking appendicitis

  3. Inflammatory Reaction and Local tissue necrosis due to dead worms
• Elevated eosinophils in CSF

  • Similar with other CNS parasitism
• Adult worm cannot survive for a long time inside the human body
• CT Scan

  1. Cerebral edema

  2. Hydrocephalus

  3. Meningeal lesions
• Anisakis is a nematode parasite of whales, dolphins, pospoises, walruses, seals, sea lions, and other deep-marine mammals
• Related species of Anisakis

  • Contracaecum sp
  • Hysterothylacium sp