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Internal Parasites 6

Description: Internal Parasites of Dogs from Chapter 6
Category: Veterinary
Created by: BananaGirl05 on 2009-01-15


 

 

-The vet tech may be asked to perform a variety of diagnostic procedures to locate endoparasites. -These procedures usually detect the adult stages of a parasite or their eggs or larval stages in the animals feces, urine, or blood. -Mature parasites are seldom found because they are generally hidden with in the body of the animal. The only way to detect them is by using immunologic test, performing a necropsy, or postmortem dissection. -Some eggs of parasites are similar. Parasites with similar eggs usually are differentiated by fecal cultures and larval identificaion.

-THE TIME ELAPSED BETWEEN INTIAL INFECTION WITH A PARASITE UNTIL THE INFECTION CAN BE DETECTED BY USING COMMON DIAGNOSTIC PROCEDURES IS CALLED THE PREPATENT PERIOD.

Common Types of Parasites: -Parasites that inside the body of the animal are called endoparasites. -Each parasite has a different life cycle, and have various developmental stages, all of which may occur within the same host or a group of different hosts. -Definitive hosts: -The host that habors the adult, mature, or sexual stages of the parasite. -Ex: The dog is the definitive host for Diroflilaria immitis. Adult male and female heartworms are located in the right ventricle and pulmonary arteries of the heart. -Intermediate Host: -The host that habors the immature, or asexual stages of a parasite -Ex: The mosqutio is the intermediate host for D. immitis; first, second, and third larval stages of D. immitis are found within the mosquito intermediate host.

-The diagnostic stage of a parasite may leave the host through excerta, such feces, urine, or be transmitted from the bloodstream to its next host by an arthropod, such as a mosquito. -The microfilarial stage is the diagnostic stage of D. immitis; the female mosquito takes in the microfilariae during a blood meal.

A. Protozoa (Unicellular Organisms) -One celled organisms

-Protozoans can infect a variety of tissue sites with in the definitive hosts. -Blood Protozoa: (Hemoprotozoa) *Are found in blood samples and are the most common. -Intestinal Protozoa: *Found in fecal samples.

  • Ex: Babesia bigemina- tear shaped hemoprotozoan found in RBC of infected cattle, transmitted by ticks.

B. Trematodes (Flukes): -Are flatworms with unsegmented leaf shaped bodies called flukes. -In domestic animals, most adult flukes are found in the intestinal tract, the liver or even the lungs. -Hermaphroditic: *Having male and female sex organs. *Lay eggs that are passed through the feces. -The larval stage of a fluke is called a miracidium. *Hatches and exits the egg through the operculum. *Penetrates first intermediate host; usually a snail. -While the miracidium is in the snail it develops into a sporocyst, which then produces many tiny internal structures call radiae. -Each rediae may produce many internal cercariae.

Definitions: -Sporocyst: Larval stages of a digenic trematode that develops in a mollusk intermediat hosts. -Redia: A secondary larval form of some digenic trematodes that develops within a mollusk intermediate host. -Cercaria: Life cycle stage of trematodes that develops in the intermediate host.

-There are 3 pathways for the cercariae to enter the definitive hosts. 1. Develops into a metacercaria and encyst upon vegetation and ingested by a definitive hosts. 2. It may be ingested by a 2nd intermediate hosts and become encysted as the metacercarial stage within that hosts, whichis subsequently ingested by the definitive host. 3. Cercaria may directly penetrate the skin of the definitive host.

C. Cestodes (Tapeworms) -These tapeworms and also called flatworms. -They are hermaphroditic. *Cestodes are ribbonlike and divide into long chains of proglottids. *Proglottids: -Segments connected like train cars behind a scolex or "head", by which the tapeworm attaches to the hosts intestinal wall. -Proglottids often contain eggs when they are passed into the feces. *Eggs contain hexacanth embryos. -Internal structures with 6 hooks. -An intermediate host like a rabbit ingest the hexacanth embryos. -The embryos grow within the tissue of the intermediate host and develop into a "bladderworm" stage, (Fluid-filled larval stage) -Definitive hosts ingests the intermediate host and becomes infected.

Examples: -Canine taeniid tapeworm (Taenia pisiformis) -Coenurus tapeworm (Multiceps multiceps)

-The some tapeworms the larval stage with in the vertebrate host is a hydatid cyst. *Echinococcus Multiceps *Echinococcus Multocularis

D.Nematodes (Roundworms) -Referred to as roundworms and are the most important group of parasites. -They have seperated sexes (male and Female). Eggs or larval are recovered with in the feces.

Examples include: Intestinal Nematodes *Large Roundworms: Toxocara canis, Toxocaris leonina *Hookworms: Ancylostoma caninum, Uncinaria Stenocephala *Whipworms: Trichuris vulpis Urinary Roundworms: *Canine Kidney worms: Dioctophyma renale

Respiratory Roundworms: *Dictyocaulus and Muellerius caillaris

Blood Nematodes: *Canine Heartworm (Diroflilaria immitis.

E.Acanthocephalans (Thorny-Head Worms) -Uncommon Parasites with complicated life cycles.

COMMON ENDOPARASITES OF DOMESTIC ANIMALS Parasites of the Intestinal Tract

A.Endoparasites of Dogs and cats. -Nematodes: -Spirocerca Lupi: -The esophageal worm -Forms nodules or granuloma in the esophageal wall of dogs and cats. -Sometimes found in nodulesin the stomach of cats. -Eggs are a unquine paperclip shape -PPP is 6 months.

-Physaloptera: -Stomach worms of dogs and cats. -Sometimes found in the lumen or the small intestines. -Firmly attached to the mucosal surface of the stomach, sucking blodd. -Symptoms: Vomiting, anorexia, and dark tarry stools. -PPP: 56 to 83 days.

-Aonchotheca putorii (Capillaria putorii): -Referred to as the gastric capillarid of cats. -Mainly paraitizes minks but has been reported in cats.

-Ollulanus tricuspis: -Feline trichostrongyle -Associated with vomiting in cats. -Identified by examination of cats vomitus. -The infective third stage larvae mature to adults in the cats stomach. -Transmission occurs through ingestion of vomitus from infected cats.

-Toxcara canis, Toxocara cati, and Toxocaris leonina: -Ascarids of dogs and cats. -Found in the small intestines of dogs and cats. -Eggs are spherical with a deeply pigmented center and a rough pitted outer shell. -PPP: T. canis is 21 to 35 days and T. leonina is 74 days

-Auncylostoma caninum: -Canine heartworm

-Ancylostoma tubaeforme: -Feline Heartworm

-Ancylostoma braziliense: -Canine and feline hookworm

-Uncinaria stenocephalal: -Nothern canine hookworm -Hookworm infection can produce servere anemia in young kittens and puppies, can be a serious problem in kennels. -PPP: depends on the species of hookworms.

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