1. Phylum Nematoda
If all the matter in the universe except the nematodes were swept away,…we should find our world’s mountains, hills, vales, rivers, lakes and oceans represented by a thin film of nematodes.
N.A. Cobb (1914, Yearbook of the United States Department of Agriculture)

2. Phylum Nematoda Parasitic and free-living Numerous and diverse
6.7 ml of coastal mud
1,074 individuals
236 species
Rotting apple:
90 thousand individuals
Farmland:
9 billion per acre

3. Phylum Nematoda Roundworms Dioecious (mostly) Tapered at both ends
Pseudocoelomate
Pseudocoel
Complete digestive system
Mouth and anus
What kind do platyhelminths have?

4. Pseudocoelomate Characteristics
“false” body cavity
ectoderm
pseudocoelom
mesoderm
Gut
endoderm
the pseudocoelom is lined by mesoderm
on ONE side only

5. Characteristics of the Phylum Nematoda

6. Phylum Nematoda
Triradiate pharynx
Pharynx between mouth and esophagus

7. Photo by Agustín Jimenez

9. Phylum Nematoda Body covered by: Cuticle Noncellular Molts
4 times during development

10. Elaboration of Cuticle
Aspidodera

11. Phylum Nematoda Movement Contraction of muscles
Longitudinal muscles
Hydrostatic skeleton
Fluid filled pseudocoel
Cuticle
Contraction of muscles
Antagonized by pressure of pseudocoel and hydrostatic skeleton

12. Tube within a tube
Female
Esophagus
Uterus
Vulva

13. Tube within a tube
Male
Cloaca = common area for openings of genital pore and anus

14. Copulatory Spicules Hold vulva open during copulation

15. Reproduction Dioecious Some Monoecious (rare) Parthenogenesis
Females reproduce without males
Unfertilized eggs develop into new individuals
Sometimes systems are mixed (heterogamy)
Mate Finding
Pheromones
Thigmotaxis (papillae near reproductive structures)

16. Papillae
Sensory structures

17. Mating Behavior
Male coils tail around female and searches for vulva.

18. Characteristics of the Phylum Nematoda
Nematode development is similar in all nematodes.
 Consists of 4 juvenile stages between the egg and adult. Each stage is separated by a molt of the cuticle.
Hatch M M M M4
Egg J J J J Adult
Juvenile stages may be passed within the egg, free-living in soil, parasitic in an intermediate host, or parasitic in definitive host.

19. Parasitic Nematodes

20. Order Ascaridida Ascaris lumbricoides Ascaris suum Toxocara canis
Ascaridia galli
Parascaris equorum
Anisakis sp.
Baylisascaris procyonis

21. Ascarids These are large roundworms of animals, and humans (7-40 cm).
As adults they live in the small intestine of mammals and birds.
These are predominantly parasites of young animals and people.

22. Ascaris lumbricoides and A. suum
Similar species
Ascaris lumbricoides
Humans
Ascaris suum
Pigs
Probably dealing with two diverging populations
Cross infection can occur

23. Facts
The annual global morbidity (# of people infected) due to Ascaris infections is estimated at 1 billion with a mortality (# of people that die) of 20,000.
Ascariasis can occur at all ages, but it is more prevalent in the 5 to 9 year age group. The incidence is higher in poor rural populations.

24. Biology
Adults live in the small intestine (1 foot long by 5-6 mm in diameter).
Worms are along the mucosa so ordinarily not much obstruction.
Feed on semi-digested material.

25. Life Cycle
Adults in small intestine mate and lay eggs which are passed in the feces of the host.
Eggs must embryonate in soil (not infective initially) takes about 1 month; molt to J2 (J3) stage in egg.

26. Biology One worm will lay 200,000 + eggs per day.
Extremely resistant; infective eggs will last for years in the soil.

27. Biology Eggs are golden brown in color.
Eggs are covered with proteinaceous coat (mammillated surface) which makes them very sticky!
Unfertilized egg Fertilized egg Decorticated egg

28. Eggs Unfertilized egg Fertilized egg Decorticated egg
Size X μm

29. Life Cycle
In order to be infected humans must swallow embryonated eggs with J2 (J3)’s!

30. Contaminated food, hands, etc.

31. Life Cycle Eggs swallowed Hatch in small intestine
Juveniles penetrate mucosa and enter blood stream

32. Life Cycle
Juveniles pass through liver and heart to lungs and molts to J3
Develop for days
Penetrate the alveolar walls, ascend the bronchial tree to the throat and molts to J4

33. Life Cycle Swallowed Go back to small intestine
Molt and mature into adults

34. Pathology and Symptoms
Usually in people the first few times we are exposed to Ascaris not much response.
However, humans are allergic creatures, and the more times exposed the more severe the reaction!

35. Pathology and Symptoms
Get granulomas in liver!
Liver milk spots

36. Pathology and Symptoms
Have trouble breathing in lungs, coughing, even pneumonia and sometimes death!

37. Pathology and Symptoms
Ascaris has characteristic 3 lips.
Use to chew mucosa.
Secretes enzymes of their own on the surface.

38. Pathology and Symptoms
Enzymes interfere with our own enzymes (may be a reason why we don’t digest them).
Children with infection don’t grow normally  not absorbing nutrients adequately.

39. Pathology and Symptoms
In the Philippines, calorie cost is equivalent to 100,000 lbs of rice a day!

40. Pathology and Symptoms
Boy (8) mysteriously died & authorities originally thought it was homicide until an autopsy revealed that he was infected with hundreds (921) of Ascaris lumbricoides.

41. Pathology and Symptoms
People don’t usually die from ascarid infections even though they have hundreds of worms.
Won’t feel good, and will be robed of nutrients.
Symptoms are practically non existent to abdominal discomfort and diarrhea

42. Pathology and Symptoms
Occasionally obstruction can occur when worms are treated in heavy infections and form knots.

43. Pathology and Symptoms
Worms migrate looking for mates.
Can crawl out through the nose, ears, anus.
Problem is that they can wander into small holes or other areas.

44. Pathology and Symptoms
Infant suffocation due to worms wondering into trachea.
Known to get in Eustachian tubes in ear and cause balance problems.
Crawl into appendix.

46. Distribution and Treatment
Drugs of choice: Ivermectin and Mebendazole.
Cosmopolitan!

47. Toxocara canis and Toxocara cati
Common ascarids in the intestines of dogs and cats!
Prevalence in dogs and cats is estimated to be between 20 to 100%.
These parasites are enzootic in Oklahoma dogs and cats.
Adults are much smaller than Ascaris.
- males are about 10 cm in length
- females are 18 cm in length

48. Toxocara canis Life Cycle
4 aspects to the life cycle:
1. Normal cycle in the dog (dogs up to 6 months of age)
Dogs are infected by ingestion of eggs with J2 (J3)
Juvenile undergo migration through lungs and are swallowed
Reach adulthood in dog small intestine
1. Normal cycle in dog

49. Toxocara canis Life Cycle
2. Addition of a paratenic host (rodent)
If a mouse ingests an infective egg, the juvenile J2 (J3) hatches and migrates to many internal organs.
It develops no further.
If mouse is eaten by a dog, the J2 (J3) penetrates the dog’s intestine and undergoes normal migration.

50. Toxocara canis Life Cycle
Transplacental transmission
If a bitch becomes infected, the migrating J2 (J3) can cross the placenta to infect the fetal puppies.
When the puppies are born, they are already infected with worms; PPP 3-4 weeks.
Prevalence rates in puppies can reach 100% because of the efficiency of transplacental transmission.

51. Toxocara canis Life Cycle
4. Human infection
Human infections of Toxocara cause "visceral larva migrans"
This disease results when eggs with J2 (J3) are accidentally ingested by humans.

52. Toxocara canis Life Cycle
J2 hatch in the human small intestine, penetrate the intestine, and enter the circulation.
J2 are carried throughout the visceral organs where they wander randomly - hence, the name "visceral larva migrans".

53. Toxocara canis Life Cycle
Eventually, the human immune system recognizes the parasite encapsulates it, and the J2 (J3) is killed.

56. Pathology of Visceral Larva Migrans
PATHOLOGY - dependent upon which organs are invaded by the J2 (J3)
The liver is commonly invaded - hepatomegaly & cirrhosis may occur.
Brain invasion results in a severe tissue reaction that can result in death
3. The eyes may be invaded - scar tissue deposition in the retina can result in blindness
J2 (J3) in retina
Scar tissue in retina

57. Tragically, most human cases involve children due to their close association with pets.

58. Diagnosis and Treatment of Toxocara in Dogs & Cats
Adults in dog - Identify egg in feces
Diagnostic features –
85-90 X 75 μm subsperical,
yellow-brown, thick shell with
coarsely pitted surface,
1 cell stage
TREATMENT – Ivermectin, Piperazine

59. Diagnosis and Treatment of Human Visceral Larva Migrans
Larvae in human are very difficult to ID
- only way is to do an ELISA 
TREATMENT – mebendazole has recently been reported to be successful.

60. Prevention of Human Infection
Many cities have enacted "pooper scooper" laws that require owners to clean up after their pets.
Especially important in parks where pet owners take animals for walks and children are playing.

61. Parascaris equorum

62. Parascaris equorum Parasite of equids Cosmopolitan
Pathogenic in young animals
Pneumonia
Bronchial hemorrhage
Intestinal perforation
Obstruction
Older animals usually immune

63. Parascaris equorum
Worms are cm in length; eggs are 100 X 90 μm, dark brown, thick shell with a finely granulated surface!

64. Lifecycle
Eggs are passed in manure and become infective J2 (J3) in the grass.

65. Lifecycle
Eggs are passed in manure and become infective J2 (J3) in the grass.
While grazing, the horse swallows the eggs, which hatch and burrow into the walls of the intestine.

66. Lifecycle
Eggs are passed in manure and become infective J2 (J3) in the grass.
While grazing, the horse swallows the eggs, which hatch and burrow into the walls of the intestine.
From there, they are carried by the bloodstream into the liver and lungs. The horse coughs up the J4 and swallows them again. Worms mature into egg-laying adults in the intestine.

67. Ascaridia galli Parasite of domestic fowl Life cycle
No migration
After hatching, burrow into intestinal mucosa
Develop
Return to lumen and become an adult
Wandering worms can end up in chicken eggs

68. Ascaridia galli
Worms are about 10 cm long; the eggs are elliptical with a smooth thick shell 85 μm X 50 μm.