Parasitology exam 5

What type of life cycle do toxoplasma gondii have?

facultative direct and indirect

Which is the only host of toxoplasma gondii where sexual reproduction occurs? Where in this host does it occur?

In the small intestine of cats

What species is the only definitive host for toxoplasma gondii?

cats

How are most cats infected with toxoplasma gondii? What is another way they can get infected?

• MOST via ingestion of tissue cysts

• additionally infected by ingestion of oocysts

What type and where does reproduction of toxoplasma gondii occur in domestic livestock, dogs, grazing wildlife, birds, and people?

asexual replication in the CNS and edible tissues

What are the two phases of toxoplasma gondii infection in cats?

• intestinal phase

• tissue phase (asexual replication)

What are signs of the intestinal phase of toxoplasma gondii?

diarrhea, soft stool, without specific clinical signs

What are signs of the tissue phase of toxoplasma gondii?

respiratory disease and lymphadenopathy

What parasite do these oocysts belong to and how large are they?

toxoplasma gondii

• 12 um

What pathology is this and what parasite is it indicative of?

Tachyzoites in the lymph nodes of a cat infected with toxoplasma gondii

What pathology is this and what parasite is it indicative of?

Bradyzoites in the brain of a mouse infected with toxoplasma gondii

What is a common sign of toxoplasma gondii in sheep’s and goats?

abortion storms

What is the difference between abortions in sheep and goats infected with toxoplasma gondii?

• In sheep, 1st exposure while pregnant is a risk but subsequent pregnancies are protected from abortion

• In goats, abortion risks span over multiple pregnancies

A dog has clinical signs of lymphadenopathy, neurologic disease, respiratory complaints, and myositis. What is the likely diagnosis?

Infection with toxoplasmosis

What is the relationship between toxoplasmic encephalitis and HIV?

In HIV patients, the occurrence is almost always caused by reactivation of a chronic infection and there is a direct correlation with pre-existing Ab titer

True or False: Babies with congenital toxoplasmosis appear normal at birth and develop symptoms months to years later

TRUE

• 90% of babies appear normal at birth

• 55-85% develop problems months to years later

• often asymptomatic until 20s-30s

When does abortion or serious congenital abnormalities occur in pregnant humans infected with toxoplasma gondii?

more likely to occur in 1st trimester

When are clinically inapparent infections with toxoplasma gondii possible in babies?

If infection occurs late in the third trimester

What symptoms are seen in babies when infection with toxoplasma gondii occurs in the 2nd and 3rd trimester of pregnancy?

mild retardation and blindness

What tests are used to diagnose infection with toxoplasma gondii?

• fecal exam

• serologic testing

• PCR

• specimen testing

Make a diagnosis for toxoplasma gondii using the following titers

• negative IgG

• negative IgM

No toxoplasma infection

Make a diagnosis for toxoplasma gondii using the following titers

• negative IgG

• positive IgM

early acute infection with toxoplasma gondii

• retest 2-3 weeks later to see ig IgG is positive

Make a diagnosis for toxoplasma gondii using the following titers

• equivocal IgG

• equivocal IgM

re-test and examine other options if IgG is not positive on re-test

Make a diagnosis for toxoplasma gondii using the following titers

• positive IgG

• positive IgM

Possible acute infection with toxoplasma

• re-test new specimen to identify a rising IgG titer (4-fold)

Make a diagnosis for toxoplasma gondii using the following titers

• positive IgG

• negative or equivocal IgM

Infection with toxoplasma for longer than 1 year

• re-test new specimen for rising IgG titer (4-fold) → if no change, assume chronic infection

Which antibody plateaus within one month after infection with toxoplasma gondii? Which plateaus within 2-3 months when treatment is absent?

• one month - IgM

• 2-3 months - IgG

What are some possible behavior changes observed in male and female humans infected with toxoplasma gondii?

• Female - more intelligent, outgoing, conscientious, kind

• Male - opposite traits

• ALL appear more guilty

What is the relationship between toxoplasma gondii and mental health problems?

People with mental health problems are more likely to be seropositive for the parasite than uninfected controls

Does eating meat increase the chance of an infection with toxoplasma gondii?

Yes, no, maybe - some correlation between decreased positivity in vegetarians or those with religious restrictions on meat consumption

True or False: cat ownership increases the chance of acquiring infection with toxoplasma gondii

FALSE

What are the t. gondii testing recommendations for women of childbearing age?

• get tested prior to and yearly for T. gondii

• test regularly during prenatal exams

What are the treatment goals when treating for toxoplasma gondii?

RESOLUTION OF CLINICAL DISEASE

• arrest rapid proliferation of the tachyzoite stage

• NO CURATIVE THERAPIES

What is the treatment of choice for toxoplasma gondii in humans?

clindamycin (tolerated in HIV patients)

Which drug targets the apicoplast stage of t. gondii?

ponazuril and diclazuril

What is the apicoplast stage important for?

fatty-acid metabolism

Which parasite doe these oocysts belong to? How large are they and where are they found?

Neospora caninum

• 10um

• found in the small intestine epithelium

What species is the only DH for neospora caninum?

Dogs are the only DH and allow the parasites to sexually multiply

True or False: The only IH for neospora caninum are some grazing hoof stock

TRUE

Is neospora caninum an intercellular or extracellular parasite?

intercellular

What is the predominant life cycle of neospora caninum?

obligate indirect

How is the DH usually infected with neospora caninum?

ingestion of tissue cysts in the IH

• oocyst transmission to DH appears insignificant

Are neospora caninum zoonotic?

NO - not zoonotic

How are intermediate hosts infected with neospora caninum?

• ingestion of oocysts

• prenatal vertical transmission

What is the clinical significance of neospora caninum in dogs?

neuromuscular disease in canines - posterior paresis

• asymptomatic at birth with clinical disease > 3 weeks later

What is the clinical significance of neospora caninum in cattle?

Disease of placental/fetus

• primary infection in dam

• neuromuscular disease in congenitally infected calves (vertical transmission)

Are dairy heifers or beef heifers more likely to be seropositive for neospora caninum?

dairy heifer 8.59x more likely

What is the main area of economic loss in regards to infection with neospora caninum?

Primarily reproductive losses

• abortion storms

• culling and replacement of breeding stock

What are treatment options for infections with neospora caninum in dogs?

• clindamycin

• trimethoprim sulfadiazine AND pyrimethamine

What are treatment options for infections with neospora caninum in cattle?

• toltrazuril and ponazuril

What species does this sporocyst belong to? How large is it?

sarcocystis species

• 15 × 8um

What life cycle do sarcocystic organisms undergo?

obligate indirect lifecycle

How does the DH acquire the sarcocystic infection from the IH?

Via ingestion of tissue cysts in IH

Which species are the only hosts where sexual reproduction can occur? Where does this replication occur?

• Domestic and wild cats/dogs

• Occurs in the small intestine

Who are the intermediate hosts for sarcocystic infections? What type of replication occurs and where does it occur in the intermediate hosts?

• domestic livestock, birds, grazing wildlife

• asexual reproduction occurs in striated muscle or endothelial cells

True or False: Disease with sarcocystic parasites is only clinical in the DH?

FALSE: Disease is in the IH

Is sarcocystosis zoonotic?

YES

Describe the life cycle of s. cruzi. How many hosts are required? Is clinical disease seen in all hosts?

obligate indirect lifecycle

• IH is cattle - adverse effects seen

• DH is dogs - no clinical disease

How are cattle infected with s. cruzi?

ingest sporocysts while grazing → two generations of asexual replication

What are the clinical signs of sarcocystosis in cattle?

• abortion, still born, eosinophilic myositis

• fever, anorexia, diarrhea, muscle spasm, hyper excitability, hair loss

• CACHEXIA in calves - FAIL TO THRIVE → premature death

What treatment is used for infections with s. cruzi?

amprolium

What is a negative aspect of treating s. cruzi?

Not economically practical - expensive per head

What is the primary etiologic agent of of equine protozoa myloencephalitis?

sarcocystis neurona is the primary agent

• n. hughesi

• s. fayeri

What species is the DH for s. neurona?

opossums who pass the sporocysts in their feces

What species are aberrant/accidental hosts for s. neurona? Why?

Horses - the tissue cysts are NOT viable and DO NOT produce infection in the DH

What are the clinical signs of s. neurona?

neurologic disease

• stumbling, ataxia, incoordination, lameness

• paresis, muscle atrophy, recumbency

• diaphoresis, urinary incontinence, constipation

How is infection with s. neurona diagnosed?

Serology

• presence of IgG

• IFA testing

For infections with s. neurona, does seropositivity equate to disease?

NO, the infection is widespread but the disease (EPM) is rare

True or False: More horses have antibodies to s. neurona than they express the neurologic disease of EPM

TRUE

How is EPM treated? What is the goal?

• ponazuril

• sulfadiazine/pyrimethamine

• GOAL IS TO CONTAIN PARASITE REPLICATION

Which parasites are associated with hepatozoonosis?

Haemogregarine parasites in genus hepatozoon

True or False: Disease associated with hepatozoonosis results from the asexual reproduction of the parasite within leukocytes of the DH

FALSE: It is associated with the asexual reproduction of leukocytes in the IH

What species is the DH for Haemogregarine? What type of reproduction occurs in th

TICKS

What species is the IH for Haemogregarine? How are they infected?

DOGS - infected by ingestion of ticks with mature oocysts in the haemocel

Which species, H. americanum or H. canis, is milder?

H. canis is milder than H. americanum

How old are dogs when they start to demonstrate age associated immunity to infections with H. canis?

> 4 - 6 months old

How do dogs acquire H canis?

ingestion of rhipicephalus sanguinensis

Describe the life cycle of h. canis?

dogs ingest oocysts in ticks → meronts replicate asexually in bone marrow → ticks bite dogs and ingest gammons within the circulating neutrophils

When infected with h. canis, is there a low or high parasite level?

low, except for in cases with 100% of neutrophils infected

How are dogs infected with H. americanum?

ingested of infected amyblomma maculatum - transmission via PARATENIC HOST

Where do the meronts of H. americanum replicate in host tissue?

asexually within the striated muscle

What type of response is elicited by merozoites of H. americanum?

pyogranulomatous inflammatory response

What clinical signs are associated with infection of H. americanum?

• fever, lethargy, mucopurulent ocular discharge

• neutrophilic leukocytosis and non-regenerative anemia

• stuff gait, myositis, ascending progressive muscle weakness and head atrophy

• periostea lesions

How would you diagnose infection with H. americanum?

• muscle biopsy

• serology, PCR

This pathology is seen on a sample from a muscle biopsy. What is your diagnosis?

infection with H. americanum

What is the black arrow pointing to?

A gamont among circulating white blood cells

What is this picture demonstrating?

a cyst containing the merozoite stage of h. americanum

How long does infection with H. americanum last in dogs?

LIFELONG but remission of clinical disease is possible

What combination therapy is used to establish remission of h. americanum infection?

• trimethoprim-sulfadiazine

• clindamycin

• pyrimethamine

When does relapse of clinical disease for h. americanum usually occur?

2-6 months post treatment

what drug prevents relapse of h. americanum clinical disease?

decoquinate

describe the life cycle of babesia sp.

• ticks ingest merozoites from the blood of vertebrate IH → sexual reproduction occurs within the tick (DH) → trans ovarian infection of tick offspring → IH infected when ticks feed for their obligate food meal

What is the etiologic agent of Texas cattle fever?

bovine babesiosis

How is bovine babesiosis controlled?

intensive dipping

What are the two species of babesiosis dogs are mainly infected by? How can you tell them apart?

• B. canis - larger piroplasms, 4-5 um and pear shaped

• B. gibsoni - smaller piroplasms, 3 um and round to oval shaped

Which species of babesiosis is associated with greyhounds?

B. canis

Which species of babesiosis is associated with direct transmission via fighting?

B. gibsoni

What is responsible for the pathogenesis of babesiosis?

UNLIMITED ASEXUAL MULTIPLICATION of the parasite and its destruction of erythrocytes in the vertebrate host

what disease signs do we see associated with babesiosis in cattle?

pyrexia, hemoglobinuria, anemia, icterus, splenomegaly

what disease signs do we see associated with babesiosis in canines?

pyrexia, anemia, thrombocytopenia, splenomegaly, lymphadenomegaly, dysorexia, vomiting, lethargy

What subset of canines is b. canis pathogenic to?

non-pathogenic except in puppies