systemic apicomplexans - ncsu veterinary parasitology · systemic apicomplexans toxoplasma gondii....

Systemic Apicomplexans

Toxoplasma

Protozoan Groups

Flagellates

HemoflagellatesTrypanosoma cruziLeishmania infantum

MucoflagellatesTritrichomonas foetusGiardia spp.

Apicomplexans

Intestinal ApicomplexansCryptosporidium parvumEimeria spp.Cystoisospora spp.

Systemic ApicomplexansToxoplasma gondiiNeospora caninumSarcocystis cruzi, S. neurona

Blood ApicomplexansBabesia bigemina,Babesia canis, B. gibsoniCytauxzoon felis

Ciliates

Balantidium coli

Amoeba

Entameoba histolytica

Historically, protozoa have been grouped by mode of motility.

Toxoplasma gondii

Feline coccidian of zoonotic importancehttps://medicalxpress.com/news/2014-07-toxoplasma-gondii-cancer-tracks-vaccine.html

https://www.cdc.gov/dpdx/toxoplasmosis/index.html

Toxoplasma

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Morphology

Oocyst small, sub-spherical, smooth coat, no polar cap,

single embryo when passed = unsporulated Sporulated oocyst contains 2 sporocysts with 4

sporozoites each = 8 sporozoites total


Toxoplasma


Complex Life CycleCat to Cat

Direct Life Cycle (homoxenous) Definitive host – Felids only

Transmission -- fecal-oral, ingestion of oocyst Invasion -- Sporozoites excyst from oocyst and invade

enterocyte Asexual reproduction (in intestinal cells)

Endodyogeny [single division forming 2 daughter cells] andSchizogony [multi-nuclear division followed by cytoplasmic division forming multiple daughter cells]

Approximately 5 cycles of endodyogeny and / or schizogony Causes none to mild pathology in the cat. Some sporozoites invade deep tissues multiply & disseminate as

tachyzoites, but eventually form bradyzoite cysts

Toxoplasma

Complex Life Cyclein Cat

Sexual reproduction (only occurs in the Felids) Gametogony, Fertilization, Oocyst

Dissemination Oocysts (unsporulated) exit the host in the feces and

contaminate the environment. Felids are the only hosts to pass oocysts. Felids usually only shed oocysts once in their life time Prepatent period (oocyst ingestion to oocyst passing): 19

- 48 days Oocysts highly resistant and remain infectious for many

months

Toxoplasma

Complex Life Cycle

Paratenic Host to Cat

Facultative Indirect Life Cycle (heteroxenous) Paratenic host – Any warm blooded animal Cat ingests a tissue cyst from a paratenic host =

carnivorism Bradyziotes released from tissue cysts develop into

tachyziotes. The rest of life cycle follows that of “Cat to Cat”

Asexual Cycle in Intestinal epithelium Sexual Stage resulting in an unsporulated oocyst, being passed in the

feces. As well as invasion of deep tissues to form bradyzoite cysts

Toxoplasma

Complex Life Cycle

Cat to Paratenic Host Facultative Indirect Life Cycle (heteroxenous)

Paratenic host – Any warm blooded animal, including felids

Transmission Paratenic host ingests an oocyst from the feces of a

felid Invasion -- “Zoites” enter intestinal cells and

lymph cells and transform into tachyzoites. Tachyzoites - rapidly dividing zoites via endodyogeny

(2 daughter cells / division)

Toxoplasma

Complex Life Cycle

in Paratenic Host

Asexual reproduction – extra-intestinal cells Tachyzoites are invade deep tissues and disperse throughout the

body of the paratenic host The rapid destruction of host cells during the tachyzoite phase

causes the acute / severe disease Eventually tachyzoites transform into bradyzoites

Bradyzoites Slowly dividing zoites via endodyogeny (2 daughter cells / division) Stationary (= non-disseminating) and form tissue cysts.

Tissue cysts Cause more chronic pathology in the paratenic (and human) hosts Occur in and cause damage to the brain, liver, lungs, striated muscles. Remain viable for the life of the paratenic host.

Toxoplasma

Complex Life Cycle

in Paratenic Host

General Notes Tachyzoites may be transplacentally transmitted. Mother’s ingestion of oocyst from cat feces could

lead to Toxoplasmosis in fetus

Toxoplasma

Complex Life CycleParatenic Host to Paratenic Host

Transmission ingestion of a tissue cyst from a paratenic host =

carnivorism Bradyziotes released from tissue cysts develop into

tachyziotes. Invasion and Asexual reproduction is the same

as “Cat to Paratenic Host” above General Notes

Tachyzoites may be transplacentally transmitted. Mother’s ingestion of raw meat with tissue cysts may lead to

Toxoplasmosis in the fetus

Toxoplasma

Pathology

Intestinal Phase in Felids -- minimal.

Systemic Disease (Extra-Intestinal Phase) in felids or paratenic hosts or humans Explosive replication of tachyzoites causes massive

destruction of host cells, also acute immune response. Most often affects brain, liver, lungs and striated

muscles. Tissue cysts cause physical cell/tissue damage, and are

a source for latent disease.

Toxoplasma

Clinical Disease - Cat Only

Intestinal Disease – no complaint Oocysts noticed on routine fecal

Systemic Disease - Non-specific disease: Fever, anorexia, vomiting,

diarrhea, enlarged lymph nodes, pneumonia (especially for FIV+ cats), encephalitis, nephritis, death.

Toxoplasma

Diagnosis - Cat only Intestinal Disease

Oocysts in feces Fecal float centrifugation Use Zinc Sulfate as oocysts may distort in other solutions

Systemic Disease Serologic tests – IgG and IgM antibodies. Thoracic radiographs if lung involvement Definitive diagnosis – detection of tachyzoites in

effusions, tissue aspirates or biopsy samples.

Toxoplasma

DiagnosisFecal Float Centrifugation

Toxoplasma


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DiagnosisAspirates or Necropsy

Toxoplasma


Tachyzoites from Effusion or Aspirate Bradyzoite cyst from

Necropsy / Histology




Treatment - Cat only

Intestinal Disease Pyrimethamine plus triple sulfa drugs used against

intestinal phase and acute phase. Clindamycin and Ponazuril also used.

Systemic Disease Clindamycin for at least 4 weeks (12.5mg/kg twice

daily). Supportive treatment depending on clinical signs –

oxygen for dyspnea, assisted feeding for anorexia.

Toxoplasma

Control - Cat only

Sanitation Clean litter box daily (sporulation in 1-3 days).

No raw meat for cats Don’t let cat outside to defecate or hunt

Toxoplasma

Non-felid paratenic hosts Dogs

Systemic toxoplasmosis, ingest oocyst from cat feces or tissue cyst from prey. Fever, respiratory signs

Sheep & Goats Systemic toxoplasmosis & Congenital

toxoplasmosis, ingest oocyst from cat feces Systemic – CNS signs (circling, etc.) Congenital – abortion Vaccine available - Toxovac S48

Toxoplasma

Non-felid paratenic hosts

Cattle Congenital toxoplasmosis (abortion, but

very rare), ingest oocyst from cat feces. Horse

Systemic toxoplasmosis, low pathology, ingest oocyst from cat feces

Toxoplasma


Swine Systemic toxoplasmosis, ingest oocyst

from cat feces or tissue cyst from prey. Fever, respiratory signs Highly prevalent in free-range pigs Important source of infection for humans

Toxoplasma


Poultry Systemic toxoplasmosis, ingest oocyst from cat

feces. Prevalent in free-range and back-yard chickens Important source of infection for humans

Rodents Systemic toxoplasmosis, ingest oocyst from cat

feces or tissue cyst from prey. Decreased fear of cats Major source of infection for cats & pigs.

Toxoplasma

ZoonosisSystemic Toxoplasmosis

Systemic Toxoplasmosis Concern for the immunocompromised Transmission

Ingestion of oocysts from cat feces, unwashed vegetables, or unclean hands

Ingestion of tissue cyst from undercooked meat (mainly mutton, goat, free-range pork, free-range chicken)

Toxoplasma

Immunocompetent Person 1st exposure

“flu-like” illness that may last for weeks Fever, myalgia, sore throat,

lymphadenopathy

Future exposures immune-protected, no pathology.

Toxoplasma


Immuno-deficient Adult Elderly & those w/ Immunosuppressive DZs

Severe disease (Respiratory, CNS, etc.) If 1st exposure is prior to immune-suppression, then

recrudescence may cause severe DZ If 1st or future exposures are after immune-suppression, then

may cause severe acute DZ

Toxoplasma


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Transmission Infection of Mother

Ingestion of oocysts from cat feces, unwashed vegetables, or unclean hands

Ingestion of tissue cyst from undercooked meat (mainly mutton, goat, free-range pork, free-range chicken)

Infection of Fetus Transplacental Transmission

Toxoplasma

ZoonosisCongenital Toxoplasmosis

Fetal Toxoplasmosis Severe DZ

congenital malformation mental retardation death

Toxoplasma


Pregnancy, Infection & Immunity If mother’s 1st exposure occurs during pregnancy.

Transplacental transmission is less common early in pregnancy. But more severe defects if transplacental transmission does

occur early.

If mother’s 1st exposure is prior to pregnancy, then mother’s immune system controls toxoplasmosis, unless mother is immune-deficient. Mother can get antibody tested.

Toxoplasma


Toxoplasmosis & Pregnancy Advice Get antibody tested Mother & Cat

Sero-positive then no worries for / from either. Avoid cat feces, have someone else clean litter box

daily (sporulation in 1-3 days) Avoid uncooked meat, unclean hands, unclean

vegetables, unclean knives and cutting boards. Casual contact with cats is very low risk.

Indoor cats less risky than outdoor cats. Old outdoor cats less risky than young outdoor cats.

Cats usually only shed oocysts once in their life

Toxoplasma


In-Class Discussion

A pregnant client wants to get rid of their cat due to concerns about Toxoplasmosis.

How would you educate your client?

Toxoplasma

In-Class Discussion

Compare & Contrast Toxoplasmosis in various hosts.

Toxoplasma

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