Protozoa Parasites of Dogs and Cats

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Exam 2

Giardia intestinalis:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Sarcomastigophora
-Subphylum: Mastigophora
-Order: Diplomonadorida/Trichomonadorida
-Family: Diplomonadidae
-Genus species: Giardia intestinalis

Giardia intestinalis:
Hosts

-Dogs
-Cats
-Cattle
-Sheep
-Goats
-Ilamas
-Domestic animals
-Humans

Giardia intestinalis:
Trophozoites Identification

-21um long
-Teardrop
-2 nuclei
-8 flagella
-Face-like appearance

Giardia intestinalis:
Cyst Identification

-12um long
-Ovoid
-4 nuclei

Giardia intestinalis:
Life Cycle

-Trophozoites adhere to the microvilli of the epithelial cells of small intestine and multiply asexually (binary fission) or budding
-After several replications, a trophozoite encysts
-Cysts pass down the small intestine, are passed in the feces and are the infective form
-When feces are not well formed, the trophozoite may also be present in the feces
-Trophozoite is not able to survive long outside the host
-Cysts can survive 2-4 weeks

Giardia intestinalis:
PPP

1-2 weeks

Giardia intestinalis:
Sites of Infection

Small Intestine

Giardia intestinalis:
Pathogenesis and Lesions

-Many infections asymptomatic
-Trophozoites can cause an acute focal inflammation

Giardia intestinalis:
Clinical Signs

-Often none
-Acute or chronic diarrhea

Giardia intestinalis:
Diagnosis

-Trophozoites and cysts demonstrated in fecal smears
-Trophozoites are also detected when feces are not well formed
-ELISA tests

Giardia intestinalis:
Treatment and Prevention

-Dogs (and cats): fenbendazole or albendazole
-Humans: Metronidazole
-Prevention of fecal contamination of water and feed
-Sanitation and disinfection of the environment

Trypanosoma cruzi:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Sarcomastigophora
-Subphylum: Mastigophora
-Order: Kinetoplastorida
-Family: Trypanosomatidae
-Genus species: Trypanosoma cruzi
-Common Name of Disease: Chagas' Disease

Trypanosoma cruzi:
Hosts

-Dogs
-Cats
-Humans
-Wild animals: armadillos, racoons, opossums, rats, guinea pigs, monkeys are reservoir hosts
-Domestic animals can be reservoir hosts
-Vector are required

Trypanosoma cruzi:
Trypomastigote Identification

-Found in blood smear
-Elongated, spindle or leaf-shaped
-20um long
-Has nucleus near middle of its length
-Posterior end pointed
-Single flagellum near posterior and close to the kinetoplast
-Extends along the body in the edge of an undulating membrane and terminates in a free flagellum at the anterior tip

Trypanosoma cruzi:
Life Cycle

-Infected triatomine insect vector takes a blood meal and releases trypomastigotes in its feces near the site of the bite wound
-Trypomastigotes enter the host through the wound or intact mucosal membrane
-Trypomastigotes invade cells, where they differentiate into intracellular amastigotes
-Amastigotes multiply by binary fission and differentiate into trypomastigotes and released into circulation as bloodstream trypomastigotes (do not replicate)
-Trypomastigotes infect cells from a variety of tissues and transform into intracellular amastigotes in new infection sites
-"Kissing bug" becomes infected by feeding on human or animal with circulating parasites
-Ingested trypomastigotes transform into epimastigotes in the vector's midgut
-Parasites multiply and differentiate in the midgut and differentiate into infective metacyclic trypanomastigotes in the hindgut
-Trypanosomes enter the body via oral, nasal, conjunctival mucosae or by infectious bug feces rubbed into skin abrasions
-Infection occurs through placenta, blood transfusion, organ transplant or accidental self injection
-Also when dogs drink water with infected bugs

Trypanosoma cruzi:
Sites of Infection

-Cardiac and smooth muscle
-Blood

Trypanosoma cruzi:
Pathogenesis and Lesions

-Amastigotes cause pathology in the heart muscles
-There are 3 stages of disease: acute, latent and chronic
-Cause of Chagas' disease in humans and dogs
-Puppies and kittens most susceptible

Trypanosoma cruzi:
Clinical Signs

-Highly pathogenic causing acute and chronic cardiac disease
-Pale mucous membranes, lethargy, ascites, hepatomegaly, splenomegaly, tachyarrhythmia
-Acute disease characterized by lymphadenopathy, neurology signs may be seen
-Infection in dogs and cats less common currently

Trypanosoma cruzi:
Diagnosis

-Dogs treated with pour on insecticides
-Epidemiology depends on distribution of vectors, virulence of parasite and response of host
-Transmission reduced by considering sources of infection

Cystoisospora (Isospora) canis:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Apicomplexa
-Order: Eucoccidiorida
-Family: Eimeriidae
-Genus species: Cystoisospora (Isospora) canis
-Common Name: Coccidia

Cystoisospora (Isospora) canis:
HOsts

-Dogs
-Rodents and other hosts can be paratenic hosts

Cystoisospora (Isospora) canis:
Egg Identification

-Unsporulated oocysts are a single cells or sporonts
-Protozoan oocyst is differentiated from the egg of Toxacaris leonina by smaller size and the absence of a lipid layer
-Sporulated oocysts spherical
-2 sporocysts each with 4 sporozoites, oval, largest species 50um

Cystoisospora (Isospora) canis:
Life Cycle

-Sporulated oocyst contains 2 sporocysts each with 4 sporozoites
-Dogs can acquire infection from tissues of rodents infected with asexual stages
-3 phases: sporulation, infection and schizogony and gametogony and oocyst formation

Cystoisospora (Isospora) canis:
Life Cycle-Sporulation

-Unsporulated oocysts pass in feces
-Sporulation takes place outside host
-Sporulated oocyst contains 2 sporocysts with 4 sporozoites and is the infective stage

Cystoisospora (Isospora) canis:
Life Cycle-Infection and Schizogony

-Asexual Reproduction
-Definitive host becomes infected by ingesting a sporulated oocyst
-Each sporocyst releases 4 sporozoites
-A parentic host can also ingest this oocyst and the sporozoites released invade its extraintestinal tissues/organs (muscle, liver, lung, brain) to form a cyst
-When the paratenic host and its cyst are ingested by the final host, sporozoites are released from the cyst in the final host
-Each sporozoite give rise to a schizont containing numerous merozoites
-Merozoites reupture out if the small intestinal cell, enter another cell, form a seconf and third generation schizont
-The number of schizont generations depends on the species

Cystoisospora (Isospora) canis:
Life Cycle-Gametogony and Oocyst Formation

-Sexual Reproduction
-Merozoites give rise to male and female gametocytes
-Macrogametocytes are female, remain unicellular, but increase in size to fill the parasitized cell
-They are distinguishable by the single large nucleus
-The male microgametocytes undergo repeated division to forma large number of flagellated uninucleate organisms, the microgametes
-This is the only time coccidia have organs of locomtion
-Fusion and fertilization of micro- and macrogametes take place and a cyst wall forms which results in a zygote, now an oocyst
-This oocyst reuptures out of the cell and passes as an unsporulated oocyst in the feces of the host

Cystoisospora (Isospora) canis:
PPP

4-11 days, depending on species

Cystoisospora (Isospora) canis:
Sites of Infection

Small intestine

Cystoisospora (Isospora) canis:
Pathogenesis and Lesions

Host small intestinal cells are destroyed and this lead to a disruption of villous architecture and enteritis

Cystoisospora (Isospora) canis:
Clinical Signs

-Diarrhea can be severe, watery, profuse and sometimes bloody
-Most Cystoisospora and Isospora species are low in pathogenesis and therefore infections are asymptomatic
-Young dogs are more susceptible and will show clinical signs

Cystoisospora (Isospora) canis:
Diagnosis

-Important that oocysts are differentiated from those of Sacrocystis, which are smaller in size and sporulated when freshly shed in feces
-Easily demonstrated in a fecal flotation

Cystoisospora (Isospora) canis:
Treatment and Prevention

-Management is critical
-Overcrowding and poor sanitation leads to a build up of heavy environmental contamination with oocysts
-Immunity develops after infection and with reinfection animals pass small numbers of oocysts
-Approved antiprotozoal remedies are available

Toxoplasma gondii:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Apicomplexa
-Order: Eucoccidiorida
-Family: Sarcocystidae
-Genus species: Toxoplasma gondii

Toxoplasma gondii:
Hosts

-Definitive Host: Cats and other felids
-IH: warm-blooded animals, humans, livestock and birds
-Zoonosis

Toxoplasma gondii:
Egg Identification

-Occysts found in feces of cats
-Small 12 um
-Sporulated in 1-5days
-Contains 2 sporocysts, each with 4 sporozoites

Toxoplasma gondii:
Life Cycle:

-Unsporulated oocysts are shed in the cat's feces
-Although oocysts usually only shed for 1-2weeks, large numbers may be shed
-Oocyst take 1-5days to sporulate in the environment and become infective
-IH in nature become infected after ingesting soil, water or plant material contaminated with oocysts
-Oocysts transform into tachyzoites shortly after ingestion
-These tachyzoites localize in neural and muscle tissue and develop into bradyzoites (tissue cyst form)
-Cats become infected after consuming IH harboring tissue cysts and ingestion of these tissue cysts in the most important route
-Following infection, the tissue cyst qall is digested in the cat's stomach and in the intestinal epithelium the liberated bradyzoites initiate a cycle of schizogonous and gametogenous development culminating in the production of oocysts in 3-10 days
-Cats may also become infected directly by ingestion of sporulated oocysts
-During final host cycle in the intestinal mucosa, the organisms invade the extraintestinal tissues/organs,where the development of tachyzoites and bradyzoites proceed as in IH
-Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment
-The liberated sporozoites rapidly penetrate the intestinal wall and spread via blood
-The invasive and proliferative stage is the tachyzoite
-Tissue cysts form in extraintestinal tissues cointaining thousands of organisms, bradyzoites
-IH can aldo ingest undercooked meat containing bradyzoites or tachyzoites from the flesh of another IH

Toxoplasma gondii:
Human Infection Routes

-Eating undercooked meat of animals habouring tissue cysts
-Consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat)
-Blood transfusion or organ transplantation
-Transplacentally from mother to fetus

Toxoplasma gondii:
Human Infection

-In the human host, the parasite form tissue cysts, most commonly in skeletal muscle, myocardium, brain and eyes; these cysts may remain throughout the life of the host
-Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens
-Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using PCR

Toxoplasma gondii:
Sites of Infection

Intestinal and extraintestinal tissue in both hosts

Toxoplasma gondii:
Pathogenesis and Lesions/Clinical Signs

-Most animals asymptomatic
-Clinical signs depend on the organ involved and extent of the injury
-Death of intestinal and extrintestinal cells is due to tachyzoites
-Clinical disease can occur in cats
-Acute toxoplasmosis in cats is due to disseminated infection with most lesions in the livers, lungs, spleen, pancreas, eyes and lymph nodes
-Severe signs are seen in cats with feline immunodeficiency virus
-Pneumonia is the most important sign in cats
-Cats develop immunity after initial infection and shed only once in a lifetime

Toxoplasma gondii:
Diagnosis

-Oocysts are very small in cats feces and shed usually for a 1-2 week period
-Serological tests or demonstration of organisms in tissues of mice infected of mice infected with suspect material
-The modified direct aggulation test, ELISA and IFA tests are preferred -Latex and indirect hemagglutination are poor
-IgM ELISA is very useful in diagnosis acute toxoplasmosis in cats

Toxoplasma gondii:
Treatment and Prevention

-Humans should avoid contact with feces from an infected cat or uncooked meat with infected tissue cysts
-One serious concern is that of exposure of human fetuses to the hazard of death, congenital malformation, loss of vision or mental retardation that may result from exposure of the nonimmune mother to T. gondii infection during pregnancy
-Can cause damage to brain, eyes, muscle, liver and lungs
-70% of women don't have circulating antibodies and need to worry about exposing their unborn babies to congenital toxoplasmosis
-No vaccine approved
-Infected cats treated with nonsulfonamides and sulfonamides

Sarcocystis spp:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Apicomplexa
-Order: Eucoccidiorida
-Family: Sarcocystidae
-Genus species: Sarcocystis spp

Sarcocystis spp:
Hosts

-FH: dogs, cats, humans, other carnivores and birds
-IH: cattle, herivores, omnivores and birds
-Several species are zoonotic

Sarcocystis spp:
Identificaiton

-In FH, sporulated oocysts contain 2 sporocysts, each with 4 sporozoites
-Sporocytes are 18um
-Sporocysts sporulate inside the intestine before being passed in feces individual sporocysts are often observed
-In muscle tissue of IH, bradyzoits are observed

Sarcocystis spp:
Life Cycle

-Gametogony in the FH
-Schizogony and sarcocyst formation in the IH

Sarcocystis spp:
Life Cycle- Gametogony

-Infection is by ingestion of mature sarcocysts with bradyzoites in the muscles of the IH
-The bradyzoites are liberated in the intestine and the freed zoites pass to the sub-epithelial lamina propria and differentiate into micro and macrogametocytes
-Conjugation and fertilization of gametes take place forming thin--walled oocysts, which sporulate within the body
-Two sporocysts are formed, each containing 4 sporozoites
-usually fragile oocyst wall ruptures and free sporocysts are found in feces

Sarcocystis spp:
Life Cycle- Schizogony

-Infection is by ingestion of the sporocysts from an infected final host and this is followed by at least 3 asexual generations
-In the first, sporozoites released from sporocysts, invade the intestinal wall and enter the capillaries where they locate in endothelial cells and undergo 2 schizogonous cycles
-A third asexual cycle occurs in the circulating lymphocytes, the resulting merozoites penetrating muscle cells
-There they encyst and divide by a process of budding or endodyogeny giving rise to broad banana-shaped bradyzoites contained within a cyst
-This is the mature sarcocyst and is the infective stage for the carnivorous final host
-This bradyzoites represent a state of arrested development or hypobiosis

Sarcocystis spp:
PPP in Carnivores

7-14 days

Sarcocystis spp:
PP

-Period during which sporocysts are passed in feces by carnivores
-1 week to several months

Sarcocystis spp:
PP of IH

-From ingestion of sporocysts to presence of infective bradyzoites in muscles of IH is usually 2-3 months, but may extend to 12 months

Sarcocystis spp:
Sites of Infection

-Muscles in IH
-Sporocysts in gastrointestinal tract of FH

Sarcocystis spp:
Pathogenesis/Clinical Signs

-No illness in FH, but schizogony in the endothelium of the herbivore may result in serious or fatal disease
-Can cause abortion

Sarcocystis spp:
Diagnosis

-Sporocysts in final hosts
-Positive diagnosis based on bradyzoites in musce tissue of the IH

Sarcocystis spp:
Treatment and Prevention

-Cycle of infection can be interrupted either by cooking meat to be fed to final hosts and preventing fecal contamination form FH

Hepatozoon spp:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Apicomplexa
-Order: Eucoccidiorida
-Family: Hepatozoidae
-Genus species: Hepatozoon spp

Hepatozoon spp:
Hosts

-Dogs
-H. americanum causes disease in dogs in US, vector id Amblyomma maculatum
-H. canis is present in areas of N. America where its vector, Rhipicephalus sanguineus occurs
-Co-infection of these 2 organisms has been reported
-Paratenic hosts play a role
-Not a Zoonosis

Hepatozoon spp:
Identification

Gamonts in blood cells of peripheral blood

Hepatozoon spp:
Life Cycle

-After dogs become infected by ingesting tick, schizont occurs in various tissues, esp. spleen and liver and finally parasitic organism are found that occur in WBCs
-Ticks become infected by ingesting a blood meal that contains WBCs that habor the gamonts of the parasite
-Sexual replication in the gut of the tick results in the production of oocysts containing infective sporozoites

Hepatozoon spp:
Sites of Infection

WBCs

Hepatozoon spp:
Pathogenesis and Lesions/Clinical Signs

-H. canis causes subclinical infection
-H. americanum causes severe disease, with dogs having a marker neutrophilic leukocytosis
-These infected animals also have joint pain associated with myositis and periosteal bone proliferation, which can be reveal in radiographs
-Lesions occurs in the proximal long bones of the limbs and are similar to those of hypertrophic osteopathy in domestic dogs

Hepatozoon spp:
Diagnosis

-Gamonts in peripheral blood
-Frequently requires the exam of muscle tissue collected at biopsy or during necropsy to reveal the schizonts
-A large cystic form of H. americanum occurs in the skeletal muscle biopsy is very useful

Hepatozoon spp:
Treatment and Prevention

-No satisfactory treatment
-Several antiprotozoals treatments have been used to treat H. canis, but have failed ot prevent relapse
-Tick control

Babesia spp:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Apicomplexa
-Order: Piroplasmorida
-Family: Babesiidae
-Genus species: Babesia spp.

Babesia spp:
Condition Caused

-Canine babesiosis
-Canine piroplasmosis

Babesia spp:
Hosts

-Dogs
-Occasionally humans

Babesia spp:
Identification

-Stained blood smears demonstrate trophozoites in RBCs
-Trophozoites are round, ovoid, elongate, amoeboid, pyriform, club-shaped
-In pairs as pyriform merozoites or in tetras as cruciform merozoites and measure 5um
-3 subspecies have been identified
-B. canis vogeli infects dogs in N. America and N. Africa
-B. gibsoni found in erythrocytes of dogs measuring 3um

Babesia spp:
Life Cycle

-After the dog is inoculated by a tick vector, B. canis sporozoites enter the bloodstream of the dog and multiply by schizogony in erythrocytes
-Intraerythrocytic Babesia are seen singly as round, oviod, elongate, ameboid trophozoites, in pairs as pyriform merozoite or in tetrads as cruciform merozoites
-Host cells rupture and new organisms penetrate new cells
-Ticks become infected by ingesting infected blood from an infected dog
-In the tick gut generation of schizogony results in the production of elongated, motile, club-shaped bodies called vermicules
-These infect tick eggs in the female tick, which continue to multiply to infect tick larva (transovarial transmission) eventually causing small pyriform bodies in the salivary cells and forming sporozoites which are inoculated into a new host

Babesia spp:
PPP

7 days

Babesia spp:
Sites of Infection

Erythrocytes

Babesia spp:
Pathogenesis and Lesions/Clinical Signs

Erythrocyte destruction leads to depression, anorexia, anemia and splenomegaly

Babesia spp:
Diagnosis

-Demonstration of trophozoites in a peripheral blood smear using Giemsa stain
-Serology also avialble

Babesia spp:
Treatment and Prevention

-Antiprotozoal remedies are effective but are nt approved in the US
-Prevention of this protozoal disease depends on control of the tick R. sanguineus

Theileria (Cytauxzoon) spp:
Taxonomy

-Subkingdom: Protozoa
-Phylum: Apicomplexa
-Order: Piroplasmorida
-Family: Babesiidae
-Genus species: Theileria (Cytauxzoon) spp

Theileria (Cytauxzoon) spp:
Hosts

-Cats
-Bobcats

Theileria (Cytauxzoon) spp:
Identification

-Small organisms 1-2um in RBCs

Theileria (Cytauxzoon) spp:
Life Cycle

-Poorly described
-Amblyomma americanum is the tick which transmits the organisms to the cat
-Trophozoites may be absent or present in the circulating blood
Schizonts are found in leukocytes, erythroblasts, macropahsges and other host cells (ex: liver, spleen, kidney, brain, etc.)
-Merozoites released froms chizonts invade erythrocytes
-Occurs in the reticuloendothelial cells

Theileria (Cytauxzoon) spp:
Sites of Infection

Blood

Theileria (Cytauxzoon) spp:
Pathogenesis and Lesions

-Rapid and fatal disease
-Die within 9-15 days after infection
-Developing schizonts cause an enlargemtn of infected cells to 75um
-Typically 1 orgamism per cell, sometimes 4
-Occlusion of the lumen of blood vessels and sinusoids in organs including heart, liver and lungs
-Parasitemia 1-4% RBCs

Theileria (Cytauxzoon) spp:
Clinical Signs

-Pyrexia
-Anemia
-Icterus
-Dehydration
-Death within a few days

Theileria (Cytauxzoon) spp:
Diagnosis

-Wright's or Giemsa-stained blood smears reveal 1-2um organisms with light blue cytoplasm and dark red nucleus in the erythrocytes

Theileria (Cytauxzoon) spp:
Treatment and Prevention

-No satisfactory treatment
-Experimentally Dermacentor variabilis transmits this disease
-Various rememdies have been used including antiprotozoals but have been met with varying results

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