Life Cycles

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Life Cycles
2014-06-09 14:02:40

Life cycles of nematode, ascarid, ancylostoma, Trichuris, Toxascaris leonina, Transtracheal migration
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  1. Nematode LC (10)
    • Egg(cell)
    • 2. Morula
    • 3. Vermiform Embryo
    • 4. hatch to L1 (stage 1) 
    • 5. molt L2  (stage 2)
    • 6. molt L3 (stage 3)
    • 7. molt L4 (stage 4)
    • 8. molt L5 (stage 5)
    • 9. adult 
    • 10. egg
  2. Ascarid LC (4)
    • 1. Eggs/ L2 (infective stage) is
    • consumed,
    • 2. Larve penetrates the stomach and enters the hepatic portal circulation in the liver
    • 3. the larva then goes to the lungs via the vena cava, right auricle, right atrium, tricuspid valve, right ventricle, pulmonary valve and pulmonary artery
    • 4. larvae enter the alveoli, are coughed up into the trachea and mouth, are swallowed, molt once in the stomach and then go to the small intestines mature and reproduce.
  3. Ancylostoma (6)
    • 1. Egg(passed in feces)  
    • 2. (hatch in 2-8days) L1
    • 3. molt L2
    • 4. molt L3(infective stage) swallowed
    • or penetrates skin, and matures to adult stage
    • 5. molt L4
    • 6. molt L5 à attaches to intestines.
  4. Trichuris LC (6)
    • 1. Eggs are passed in the feces
    • 2. egg develops into 2 cells and then
    • into more cells
    • 3. Cells form L1 larvae (infective)  
    • 4. Egg is then ingested by the host and
    • hatches
    • 5. L1 develops in the small and large
    • intestines (molt to L5)
    • 6. Adults migrate to the cecum and reproduce
  5. Strongyloides LC (5)
    • 1. Three forms exist – an asexual very pathogenic female (passes eggs that develop without being fertilized), and a sexual male and sexual female that are passed as a vermiform embryo. Sexual females and sexual males produce sexual males and sexual females only and the pathogenic female produces pathogenic females only, as far as we know.
    • 2. After being passed, the larvae will go through two molts to the infective 3rd stage.
    • 3. Infective 3rd stage larvae are consumed or penetrate the skin.

    • 4. The 3rd stage larvae will migrate through the circulation to the lungs, where they are coughed up, swallowed, and make their way back to the intestines where they molt twice to the 4th and 5th stages.
    • 5. The adult larvae reproduce and the eggs can be shed in the feces 7 to 20 days after infection.
  6. HW LC (8)
    • 1. dog 1 has adults(S5) and microfilaria(S1)
    • 2. mosquito takes blood and picks up S1
    • 3. S1 molts to S3 in mosquito (time depends on temp)
    • 4. mosquito inserts S3&saliva into dog 2
    • 5. S3 molts to S4 in subcutaneous tissue
    • 6. S4 stays in SQ tissue for 100 days
    • 7. S4 molts to S5(pre-adult) and moves to pulmonary artery
    • 8. S5 stays in pulmonary artery for 80 days then molts to adult S5
  7. Transtracheal migration (7)
    • 1. Animal consumes 2nd stage larvae (infective stage) 
    • 2. Larvae will penetrate the stomach and enter the hepatic portal circulation to the liver 
    • 3. The S2 larvae will migrate through the liver parenchyma (functional liver cells) 
    • 4. The larvae will enter the posterior vena cava and go into the lungs by way of the right auricle, right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary artery. 
    • 5. Once the larvae goes into the lungs it will migrate to the trachea where the S2 is coughed up into the pharynx and is swallowed 
    • 6. The larvae passes down the esophagus and into he stomach where it will molt to S3 and move into the small intestines.
    • 7. There it will molt to S4 then molt to S5 and begin reproducing
  8. Gastrophilus intestinalis/haemorrhoidalis/nasalis (9)
    • 1. Male and female reproduce 
    • 2. Female will lay eggs on the hairs of the foreleg and/or the shoulders 
    • 3. After about 5 days (maybe earlier) the horse will consume the eggs 
    • 4. The larvae will hatch and migrate to the dorsal surface of the tongue 
    • 5. The larvae will penetrate the tongue and remain there for 30 days then move to the lumen to be swallowed 
    • 6. The larvae will then migrate to the stomach and attach themselves to the wall of the stomach for about 11 months 
    • 7. The pupal cases will release their grip and fall out in the feces and hatch into adult male/female flies in 3 – 9 weeks. (back to step 1)
    • G. nasalis and G. haemorrhoidalis are pretty much the same with a couple of differences. 
    • --G. nasalis - lay eggs in the intermandibular space - once in the mouth, they penetrate between the molar teeth/gums - They move to the duodenum and stay there for about 10 - 11 months
    • --G. haemorrhoidalis - lay eggs on lips - in the mouth, they penetrate the mucus membranes in the cheek - they also move to the duodenum and stay there for about 10 - 11 months
  9. Toxascaris leonina (4)
    • 1. ingestion of eggs
    • 2. hatch,
    • 3. molt, and
    • 4. mature to adult all within the intestinal tract.
  10. Strongylus vulgaris LC (6)
    • 1. Horse ingest stage 3 larvae (S3) 
    • 2. S3 cast covering and enters wall of the cecum and ventral colon
    • 3. S3 penetrates submucosa and molts to stage 4 (S4) this takes about 1 week 
    • 4. S4 will penetrate the aorta and small artery walls traveling to the cranial mesenteric artery this process take 11-21 days. 
    • 5. S4 will migrate through the cranial mesenteric artery for 2 – 4 months penetrating surrounding tissue and molt to stage 5 (S5)
    • 6. S5 enters the lumen of the colon and begins reproducing in about 6 months