1. Order Strongylida Hookworms Necator americanus Americas, Africa, Asia
Ancylostoma duodenale
Europe, Northern Africa, Asia, Americas
Ancylostoma braziliensis
Carnivores in the tropics
Cutaneous larval migrans/creeping eruption
Ancylostoma caninum
Canids

4. Free-living Juveniles
Filariform are infective

6. Rhabditiform and Filariform J3’s

7. Filariform are infective

8. Filariform are infective

11. Necator americanus Ancylostoma duodenale

12. Necator americanus Ancylostoma duodenale

13. Transmission Ancylostoma duodenale Necator americanus Cutaneous
Oral ingestion of juveniles
Paratenic hosts
Transmammary
Transplacental?
Necator americanus

14. Hookworm Disease 1300 million people infected
160 million experience illness
Severity depends on:
Number of worms
Species infected with
Nutritional status of host

15. Hookworm Disease Necator americanus Ancylostoma duodenale
< 25 no symptoms
light symptoms
moderate symptoms
severe symptoms
> 1000 Very severe, often fatal
Ancylostoma duodenale
100+ severe symptoms

16. Pathogenesis Cutaneous Phase Juveniles enter skin
Entrance into blood vessels initiates tissue reaction that can kill juveniles
Itching/rash at location of penetration
Caused by bacteria
“Ground itch”

17. Pathogenesis 2. Pulmonary Phase
Juveniles enter alveoli and move up bronchi to throat
Usually asymptomatic
Hemorrhaging
Dry cough

18. Pathogenesis 3. Intestinal Phase Adults enter intestine
Attach to mucosa with teeth
Feed on blood

19. Pathogenesis 3. Intestinal Phase Adults enter intestine
Attach to mucosa with teeth
Feed on blood

20. Adults pull in a plug of tissue and suck blood!

21. Pathogenesis Blood loss extensive Blood loss exceeds what worms ingest
Lesions
Anticoagulants
Blood loss exceeds what worms ingest
Necator americanus
0.03 ml/worm/day
Ancylostoma duodenale
ml/worm/day

22. Small Intestine Infected with Hookworms: They are sloppy feeders!

23. Pathogenesis Heavy infections Anemia (Iron Deficiency Anemia)
Severe protein deficiency
Edema
Stunting
Mental dullness
Heart failure

24. Hookworm disease: statue (A) and child (B) from Costa Rica with typical stance caused by malnutrition and severe hookworm infection. (Courtesy of Dr. Herman Zaiman and Muriel Jones).

25. Iron Deficiency Anemia
Decrease in erythrocyte count due to lack of iron
Less oxygen gets to tissues
2 billion people

26. Iron Deficiency Anemia
Affects:
Protein-energy malnutrition
Growth and development of children
Physical
Cognitive
Pregnancy
Risk of death of mother and child
Low birth weight
Premature birth
General health
Loss of energy
Weakness
Shortness of breath
Mental dullness

27. “The disease induced by the hookworm…was never suspected to be a disease at all. The people who had it were merely supposed to be lazy, and were therefore despised and made fun of, when they should have been pitied.”
- Mark Twain (Letters from the Earth)

28. Diagnosis Demonstration of eggs in fecal smear
Cannot distinguish species by eggs

29. Melenic diarrhea!

30. Frank blood in diarrhea!

31. Treatment Mebendazole Single dose effective Iron supplementation
Drug resistance of N. americanus in Africa

32. Epidemiology How do you get infected? Necator americanus
Juveniles penetrate skin
Ancylostoma duodenale
Ingest juveniles orally
Paratenic host
Transmammary
Transplacental

33. Epidemiology Transmission Environmental conditions Need
Moisture
Warm temperature
Shade
Juveniles live in moisture in the soil
Migrate to stay in optimal conditions
Dry: Move downward
Wet: Move upward to surface of soil extend upward “looking for a host”
Live 3 weeks

34. Epidemiology Common in tropical or subtropical areas
i.e. Southeastern U.S.

35. Robert, LA

38. Transmission “Hot spots”
Mines
Coffee, banana, sugarcane plantations

39. Other Hookworm Species
Ancylostoma braziliensis
Domestic and wild carnivores in tropics
Most common cause of cutaneous larval migrans/creeping eruption in humans
Ancylostoma caninum
Adults occur in canids (infrequently humans)
cutaneous larval migrans/creeping eruption in humans

41. Ancylostoma caninum

42. Cutaneous Larval Migrans/ Creeping Eruption
Juveniles penetrate skin
Cannot complete migration
Tunnel through skin
Secondary infection
Weeks-months

43. Cutaneous Larval Migrans/ Creeping Eruption

46. Soil Born Nematodes “Soil born” nematodes or “Geohelminths”
Ascaris sp.
Trichuris trichiura
Necator americanus
Ancylostoma duodenale

47. “Soil-born” Nematodes
Development to infective stage
Ascaris sp.
Eggs embryonate in soil
Trichuris trichiura
Necator americanus
Juveniles develop in soil
Ancylostoma duodenale

48. Epidemiological Model of Soil-Born Nematodes
Development to infective stage
1. Contact
2. Contact
Infected
people
Soil
Uninfected
people
1. Eggs released with feces of infected human. Eggs develop in the environment, commonly in soil. Development to the infective stage must occur for successful transmission.
2. Human contacts infective stage. How does this contact differ among species discussed?

49. Sensitivity to Environmental Conditions
Rank the species according to their sensitivity
Ascaris sp.
Trichuris trichiura
Hookworm species
How is sensitivity going to effect their distribution?

50. Distribution
Warm moist habitat
Ascaris sp.
Trichuris
Hookworms

51. Distribution Warm moist habitat Ascaris sp. Trichuris
Southeastern United States
Hookworms

52. Okefenokee Swamp, GA

53. Warm temperatures High Rainfall Dense vegetation High humidity
Moisture
Runoff
Dense vegetation
Shade
High humidity

54. Geophagy

55. Geophagy Ingestion of soil Historical practice
Modern practice in Africa and SE U.S.
Special types of soil are sold
Clay based soil
Markets in Georgia, parts of Africa, and parts of South America sell soil for consumption.
Intense cravings for soil
55 yr old woman who would eat only soil if she could

56. Why? Pregnancy Cure for ailments Religious practice
Clay soils contain kaolin, the principal ingredient in Kaopectate.
Morning sickness
Intestinal ailments
Nutritional supplement
Iron
Magnesium
Calcium
Phosphorus

57. Geophagy Geophagy is often correlated with Cause and effect? Anemia
Parasite infection
Cause and effect?
Does anemia cause geophagy?
Does parasitic infection cause geophagy?
Does geophagy cause anemia?
Does parasitic infection cause anemia?
Does geophagy cause parasitic infection?

58. Geophagy and Parasitism
Western Kenya
Geophagic
Non-geophagic
Trichuris trichiura
Prevalence Egg per gram (range)
44%
48 (13-133)
37%
20 (7-37)
Ascaris lumbricoides
16%
2413 ( ) 9%
455 (25-920)
Geissler et al Transactions of the Royal Society of Tropical Medicine and Hygiene 77:

59. Summary Geophagy is a relatively common practice
Geophagy is associated with parasitism
Geophagy causes parasitism
Does parasitism cause geophagy?

60. Questions? What are the species of “soil-born” nematodes?
Why is Enterobius vermicularis not a “soil-born” nematode?