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• The most abundant animal on earth
• Nematodes


  • Dioecious- male and female worm (larger) a few mm-meter in length
  • Free living in soil, marine and freshwater habitat
  • 500,000 species
  • Nonsegmented, cylindrical, tapered at both ends
  • Body covering- cuticle with longitudinal muscles
  • Body cavity(pseudocoel)complete digestive tract with both oral and anal openings
  • Mouth is provided with spines, hooks, cutting plates, stylets or other structures for attachment or penetration of tissue
  • Reproductive organs are tubular and lie coiled in the body cavity
  • Males have chitinized spicules for copulation
  • Sensory organs- anterior end (amphids), posterior end-caudal (phasmids) nerve endings that acts as chemoreceptors

  
• Classes of nematodes


  • Aphasmidea
  • Phasmidea
• Life cycle of nematodes

  1. Egg stage

  2. Larval stage

  3. Adult stage
• Adult female nematodes


  • Oviparous
  • Vivaparous
  • Parthenogenetic
• Aphasmids include Trichinella spiralis, Trichuris trichiura, Capillaria philippinensis
• Phasmids include Ascaris lumbricoides, Strongyloides stercoralis, Hookworms, Enterobius vermicularis, Filarial worms
• Nematode habitats in the human body

  • Small Intestine
  • Large Intestine
  • Tissue
• Trichinella spiralis


  Parasite of the carnivorous mammals, smallest nematode parasite of humans, "Trichina worm"-minute and threadlike

  
• Trichinella spiralis


  • Common in rats and swine fed with uncooked garbage and slaughterhouse scraps
  • Occurs worldwide, especially in areas where raw garbage containing pork scraps is fed to hogs
  • Highest incidence rate is now reported in china- 10,000 cases annually

  
• Trichinella spiralis was discovered in 1835 by James Paget and named by Prof. Richard Owen

  
• Trichinella spiralis male adult worm

  • Less than 2mm long (1.4-1.6 mm x 40-60um)
  • Cloaca is found at caudal end which is evertible during coitus, guarded by 2 conspicuous conical papillae which clasp the female during copulation
  • Spicule is absent
  • Posterior end is curved ventral

  
• Trichinella spiralis female adult worm

  • Less than 5mm (3-4mm x 60-80 um)
  • Vulva opens at the anterior fifth of the body
  • Single uterus which contain the larva
  • Single ovary found near the posterior end (caudal)
• Trichinella spiralis larva


  • 80-120um x 5-6um (100x6um)
  • Provided with a spear-like burrowing tip at the anterior end
  • Readily transported throughout the body, leave the capillaries in striated muscle to penetrate through the sheaths of the muscle fibers
  • Larva excyst after the cyst are digested and penetrate the im- develop to adult (30-40 HRS)

  
• Trichinosis, trichiniasis, trichinelliasis


  Disease caused by ingestion of carcasses with encysted larva (infective stage)

  
• Clinical features of trichinosis include mild to moderately severe symptoms within 2-7 days after ingestion, such as gastroenteritis, diarrhea with or without abdominal pain for several weeks, weakness, fever and eosinophilia, leukocytosis, circumorbital edema, vasculitis, muscle pain, and CNS involvement
• Diagnosis of trichinosis is done by skeletal muscle biopsy and serologic tests
• Treatments for trichinosis


  • Mebendazole
  • Thiabendazole
  • Albendazole
  • Prednisone
• Prevention of trichinosis involves proper cooking of meat and maintaining proper sanitation, as well as public education
• Trichuris trichiura


  "Whipworm"- whip like in appearance, with anterior 3/5 very thin and hair like housing the esophagus, and posterior 2/5 thick and stout resembling the handle of a whip housing the intestine and reproductive organs
• Trichuris trichiura has worldwide distribution but is common in tropical countries and regions with poor sanitation, with prevalence rates up to 50-80% in Asia
• Trichuris trichiura male adult worm

  • 3-3.5 cm in length
  • Spicule protrudes through a refractile penial sheath which has a bulbous termination covered with small recurved spines
  • Distuinghed from the female by its coiled caudal extremities about 360 or more

  
• Trichuris trichiura female adult worm

  • 3.5-5.5 cm in length
  • Vulva opens at the anterior end which is the fleshy portion of the body
  • Has a single uterus and ovary
  • Bluntly rounded at the posterior end
  • Produces 3000-7000 eggs daily

  
• Trichuris trichiura ova

  • Barrel – football-shaped in feces
  • Intralaminar (refractile) prominences usually referred to as polar plugs at either end
  • 3 shells- chorionic layer, albuminous layer, bile-stained layer
  • When passed out it is usually immature (unsegmented), requires 3 weeks in soil to mature
• Trichuriasis


  Disease caused by ingestion of Trichuris trichiura ova

  
• Clinical features of trichuriasis range from asymptomatic light infections to abdominal pain, distention, appendicitis, bloody or mucoid diarrhea, tenesmus, weight loss, weakness, and rectal prolapse in heavy infections
• Diagnosis of trichuriasis is done by direct fecal smear, Kato-Katz, and fecal egg count techniques

  
• Treatments for trichuriasis


  • Mebendazole
  • Albendazole
  • Piperazine citrate
  • Pyrantel pamoate
  • Loperamide hydrochloride (Imodium)
• Prevention of trichuriasis involves proper hygiene, sanitation, and avoiding the use of fecal matter as fertilizers, as well as public education
• Capillaria philippinensis

  Intestinal capillariasis, first recognized in the Philippines in 1963
• In 1967, there was an epidemic of capillariasis in Pudoc, West Tagudin, Ilocos Sur, Philippines, with approximately 1,300 persons becoming ill and 90 persons dying
• Capillaria philippinensis adult worm

  • 1.5-3.9 mm in length for males, 2.3-5.3 mm in length for females
  • Characterized by caudal alae and long, non spiny sheaths
  • Body is divided into 2 equal parts, with anterior esophagus+esophageal glands and posterior intestine, reproductive organs with slightly prominent vulva
  • Two types of females - larviparous (population build up) and oviparous (infection)

  
• Capillaria philippinensis ova


  • 42x20um, single or 2 stage development, similar to Trichuris egg but smaller and more oval in shape, shell is thick with striations hence peanut shape, with bipolar mucous plugs but not protuberant
• Intestinal capillariasis


  Disease caused by ingestion of Capillaria philippinensis larvae from contaminated fish

  
• Clinical features of intestinal capillariasis include abdominal pain, diarrhea, borborygmi, loss of weight, weakness, anorexia, vomiting, and hypoproteinemia due to malabsorption
• Diagnosis of intestinal capillariasis is done by identification of larvae and worms in stool

  
• Treatments for intestinal capillariasis

  • Mebendazole
  • Albendazole
• Proper cooking of freshwater fish and proper sanitation are important for prevention of intestinal capillariasis
• Capillaria hepatica causes hepatic capillariasis, and Capillaria aerophila causes pulmonary capillariasis
• Ascaris lumbricoides

  "Giant Intestinal roundworm", found in temperate and tropical areas with poor sanitation and where feces are used as fertilizers, affects more of the world's population than any other parasitic disease