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

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.

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.

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

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.

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.

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.

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.

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

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

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

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

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.

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

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.

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

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.

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

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

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.

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.

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

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.

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

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.

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

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.

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.

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.

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

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.

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.

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.

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.

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

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.

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

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.

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

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.