Internal Parasites 1 Definitions Definitive host Harbors the

Internal Parasites 1

Definitions • Definitive host – Harbors the adult parasite • Intermediate host – Harbors the immature parasite • Reservoir host – Harbors a parasite but is not affected by the parasite 2

Educating Clients • Parastic life cycles – Clues regarding risks – Clues to prevention – Clues to treatment interval protocols • Client education – Accuracy in word choices – Well-informed – Be aware of internet search options 3

Trematodes • Digenetic flukes (flatworms) – Digenetic: definitive host plus two intermediate hosts – Paragonimus kellicotti (lung fluke in cats and dogs) – Schistosomes (blood fluke in wild birds; shown here) 4

Flukes • Paragonimus kellicotti (lung fluke in cats and dogs) – Eggs will float to top of most fecal flotation solutions 5

Cestodes and Metacestodes • Cestodes: Adult tapeworms – Intestinal tract of definitive host • Metacestodes: Larval tapeworms – Extraintestinal sites • Types of cestodes – Dipylidium caninum (shown) – Echinococcus granulosus/Echinococcus multilocularis – Spirometra mansonoides 6

Cestodes (Tapeworms) • The most common sign is the presence of gravid tapeworm proglottids (tapeworm segments) in the host’s feces or around the anus • Dried-out tapeworm segments resembling dry uncooked white rice may be found in bedding 7

Dipylidium caninum 8

Dipylidium caninum 9

Dipylidium caninum 10

Echinococccus granulosus • The definitive hosts, primarily canids, harbor the adult stages of the tapeworm in the small intestine • The intermediate hosts, sheep and cattle, harbor the larval stage of the tapeworm in a variety of visceral organs (the liver, the lung, and the brain) 11

Echinococcus multilocularis • The definitive hosts, primarily cats and foxes, harbor the adult stages of the tapeworm • The intermediate hosts, microtine rodents (mice, voles, and rats), harbor the larval stage of the tapeworm, in the liver and lung 12

GI Nematodes (Roundworms) • Round on cross section • Parasitize widest assortment of wild and domestic animals; many organs/systems • Types – Toxocara canis/Toxocara cati /Toxascaris leonina (cats and dogs) – Paratenic (transport) host – Baylisascaris procyonis (raccoons) – Ancylostoma aninum/Ancylostoma braziliense/Ancylostoma tubaeforme (dogs and cats) 13

Toxocara canis (Canine Roundworm) • Dog must ingest this egg for the life cycle to continue 14

Barylisascaris procyonis • Mainly found in the small intestine of the raccoon definitive host, but can be found in dogs • Similar to ascardis of dogs and cats • Diagnosed using routine fecal flotation 15

Ancylostoma (Hookworm) • Found in small intestine of dogs and cats • Voracious blood feeders • Diagnosis: Fecal centrifugation/flotatio n of fresh feces and egg identification 16

Trichuris vulpis (Whipworm) • Fresh fecal sample is best for diagnosis • Identify unique whip-like shape (fat posterior handle with long, filamentous anterior end) • Unique trichinelloid egg type. 17

Strongyloides (Intestinal Threadworm) • Strongyloides larvae (L 1 stage) • Fresh fecal sample, Baermann technique • Mucosal scrapings may reveal adult female parasites, eggs, and first-stage larvae 18

Enterobius vermicularis • Human pinworm; pseudoparasite of cats and dogs • NIH Scotch tape test – Characteristic asymmetric ovum 19

Protozoans • Unicellular – Giardia • Humans, pets, contaminated water – Toxoplasma gondii • Only cats harbor sexual stages; other mammals intermediate hosts – Cryptosporidium parvum • Intestinal • No reliable treatment • Infected dog must be isolated from other pets, children, and individuals with compromised immune systems 20

Giardia • Humans, pets, contaminated water • Cysts and trophozoites on direct fecal smear • Zinc sulfate flotation medium with centrifugation 21

Cryptosporidium parvum • Smallest protozoan parasite in GI tract • All domestic animals • Tips of villi in small intestine • Diagnosed by fecal flotation • No reliable treatment 22

QUESTIONS? 23