1. Parasitology Unit 8 Chapter 45 Nematodes
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

2. Phylum Nematoda Commonly called roundworms Cylindrical body shape
Multicellular
Cuticle – a body wall composed of an external, acellular, protective layer
Hypodermis – cellular layer beneath the cuticle
A layer of longitudinal somatic muscles that function in locomotion
Digestive tract
Tubular and suspended in the pseudocoelom
One straight tube from mouth to anus
Reproductive organs
Tubular but longer than the body
Wrap and coil around the intestinal tract
Nervous system
No respiratory system
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

3. Life Cycle Developmental stages Infective stage Egg
Four larval stages (wormlike)
Sexually mature adult
Infective stage
Egg containing a larva, free-living larva, or larva within an intermediate host
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

4. Life Cycle (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

5. Life Cycle (cont.) Direct Indirect
No intermediate host needed for development to the infective stage
Indirect
An intermediate host is needed for development to the infective stage
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

6. Life Cycle (cont.) Once a nematode gains entry to a new host:
Development may occur in the area of its final location or may occur after extensive migration through the body of the definitive host
Diagnostic stages
Most found in feces, blood, sputum, or urine
Some in lungs, kidney, urinary bladder, or heart
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

7. Taxonomic Superfamilies in Veterinary Medicine
Ascaroidea
Strongyloidea
Trichostrongyloidea
Rhabditoidea
Metastrongyloidea
Trichuroidea
Oxyuroidea
Spiruroidea
Dracunculoidea
Dioctophymoidea
Filaroidea
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

8. Ascaroidea Ascarids of dogs and cats
Toxocara canis, T. cati, and T. leonina
Found in the intestinal tract of dogs and cats around the world
All puppies and kittens should be examined for large robust nematodes
Adult ascarids – 3 to 18 cm in length
Prepatent period for T. canis – 21 to 35 days; T. leonina is 74 days
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

9. Ascarids
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

10. Ascarids (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

11. Ascarids (cont.) Parascaris equorum – equine roundworm
Toxocara vitulorum – cattle
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

12. Ascaris suum – Swine
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

13. Strongyloides Small intestine nematode
Ancylostoma caninum – canine hookworm
Ancylostoma tubaeforme – feline hookworm
Ancylostoma braziliense – canine and feline hookworm
Uncinaria stenocephala – northern canine hookworm
Bunostomum phlebotomum – ruminant hookworm
Hookworms are found throughout the world and are common in tropical and subtropical areas of North America
Produce severe anemia in puppies and kittens
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

14. Life Cycle
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

15. Strongyloides (cont.)
Eggs are oval or ellipsoid with thin walls and 8 to 16 cells
Eggs larvate rapidly in the external environment
Fresh feces needed for diagnosis
Standard fecal flotation
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

16. Strongyloides (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

17. Strongyloides (cont.)
Strongyles are parasites of the large intestine in horses
Large strongyles
Most pathogenic
Strongylus vulgaris, S. edentatus, S. equinus
Small strongyles
Vary in pathogenicity
Eggs identical
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

18. Trichostrongyloidea Bovine trichostrongyles
Identification of fecal culture and larval identification
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

19. Trichostrongyloidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

20. Trichostrongyloidea (cont.)
Ollulanus tricuspis
The feline trichostrongyle
Vomiting in cats
Mostly identified by examination of vomitus with a dissecting microscope
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

21. Rhabditoidea Strongyloides sp. Intestinal threadworms
Only a parthenogenetic female is parasitic
No parasitic males
Larvae have a club-shaped esophagus
Rhabditiform
Fresh fecal flotation diagnosis
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

22. Rhabditoidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

23. Metastrongyloidea Hair lungworms
Adults found in the bronchioles, mostly in nodules in the lung parenchyma of sheep and goats
Eggs develop in the lungs of the definitive host and the first stage larva are coughed up, swallowed, and passed out with the feces
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

24. Metastrongyloidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

25. Trichuroidea Found in the cecum and colon
Canine whipworm - Trichuris vulpis
Common
Feline whipworm – T. campanula and T. serrata
Rare in North America and diagnosed sporadically around the world
Adults have a thin, filamentous cranial end and a thick caudal end that is whiplike
Eggs – thick, yellow-brown symmetrical shell with polar plugs at both ends
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

26. Trichuroidea (cont.) T. vulpis
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

27. Trichuroidea (cont.)
Capillaria plica (Pearsonema plica) – urinary bladder of dogs and cats
Found in urine and feces
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

28. Trichuroidea (cont.)
Trichinella spiralis – often associated with raw or undercooked pork
Ingest infective larval stages in meat
Trichinosis – human parasite
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

29. Oxyuroidea Oxyuris equi – pinworm of horses
Adult worms found in cecum, colon, and rectum
May be seen protruding from anus
Enterobius vermicularis – human pinworm
Not a parasite of dogs and cats
Pets wrongly accused
Pinworms are parasites of omnivores and herbivores but never carnivores
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

30. Oxyuroidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

31. Spiruroidea Habronema sp. and Draschia megastoma Parasite of horses
Found in the stomach
Larvae may parasitize skin lesions or summer sores
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

32. Spiruroidea (cont.) Thelazia californiensis T. rhodesii and T. gulosa
Eyeworm of dogs and cats
T. rhodesii and T. gulosa
Eyeworm of cattle, sheep, and goats
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

33. Dracunculoides Uncommon parasite of dogs, cats, and other carnivores
Life cycle requires a copepod intermediate host
Definitive host become infected by ingesting the copepod
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

34. Dioctophymoidea Dioctophyma renale Stephanurus dentatus
Giant kidney worm of dogs
Infects the right kidney and gradually ingests the renal parenchyma, leaving only a capsule of the kidney
Stephanurus dentatus
Swine kidney worm
Found in kidneys, ureters, and perirenal tissues of pigs
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

35. Dioctophymoidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

36. Filaroidea Dirofilaria immitis – canine heartworm
Most important parasite of the vascular system in domestic animals in the United States
Also known to parasitize cats and ferrets
Adult heartworms – right ventricle, pulmonary artery, and the fine branches of that artery
Can be recovered from other sites like brain, eye, etc.
Prepatent period is 6 months
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

37. Filaroidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

38. Filaroidea (cont.) Diagnosis Observing microfilariae in blood samples
Modified Knott test
Commercially available filter techniques
Immunodiagnostic tests
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

39. Filaroidea (cont.)
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.

40. Summary
The life cycle of nematodes consists of several developmental stages: the egg, four larval stages, sexually mature adult
Infective stages of nematodes may involve an egg containing a larva, a free-living larva, or a larva within an intermediate host
Direct lifestyle has no intermediate host
Indirect lifestyle requires an intermediate host
Transmission of nematode parasite to a new definitive host occurs through ingestion, skin penetration, ingestion of the intermediate host, or deposit on the skin by an intermediate host
Nematode parasites of veterinary significance are in 11 superfamilies
Common nematode parasites of dogs and cats are Toxocara sp., Ancylostoma sp. , Trichuris sp., and Dirofilaria immitis
Copyright © 2015 by Mosby, an imprint of Elsevier Inc. All rights reserved.