Systemic Apicomplexans. Toxoplasma

Transcription

1 Systemic Apicomplexans Toxoplasma

2 Protozoan Groups Historically, protozoa have been grouped by mode of motility. Flagellates Hemoflagellates Trypanosoma cruzi Leishmania infantum Mucoflagellates Tritrichomonas foetus Giardia spp. Ciliates Balantidium coli Amoeba Entameoba histolytica Apicomplexans Intestinal Apicomplexans Cryptosporidium parvum Eimeria spp. Cystoisospora spp. Systemic Apicomplexans Toxoplasma gondii Neospora caninum Sarcocystis cruzi, S. neurona Blood Apicomplexans Babesia bigemina, Babesia canis, B. gibsoni Cytauxzoon felis

3 Toxoplasma gondii /index.html Feline coccidian of zoonotic importance

4 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 /index.html

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6 Complex Life Cycle Cat 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] and Schizogony [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

7 Complex Life Cycle in 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): days Oocysts highly resistant and remain infectious for many months

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9 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

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11 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)

12 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.

13 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

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15 Complex Life Cycle Paratenic 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

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17 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.

18 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.

19 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.

20 Diagnosis Fecal Float Centrifugation asmosis/index.html

21 Diagnosis Aspirates or Necropsy Tachyzoites from Effusion or Aspirate Bradyzoite cyst from Necropsy / Histology asmosis/index.html asmosis/index.html

22 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.

23 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

24 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

25 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

26 Non-felid paratenic hosts 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

27 Non-felid paratenic hosts 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.

28 Zoonosis Systemic 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, freerange chicken)

29 Zoonosis Systemic Toxoplasmosis Immunocompetent Person 1 st exposure flu-like illness that may last for weeks Fever, myalgia, sore throat, lymphadenopathy Future exposures immune-protected, no pathology.

30 Zoonosis Systemic Toxoplasmosis Immuno-deficient Adult Elderly & those w/ Immunosuppressive DZs Severe disease (Respiratory, CNS, etc.) If 1 st exposure is prior to immune-suppression, then recrudescence may cause severe DZ If 1 st or future exposures are after immune-suppression, then may cause severe acute DZ %3A+Neurology+%28B%29+-+Part+1/ overview#showall

31 Zoonosis Congenital Toxoplasmosis 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

32 Zoonosis Congenital Toxoplasmosis Fetal Toxoplasmosis Severe DZ congenital malformation mental retardation death

33 Zoonosis Congenital Toxoplasmosis Pregnancy, Infection & Immunity If mother s 1 st 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 1 st exposure is prior to pregnancy, then mother s immune system controls toxoplasmosis, unless mother is immune-deficient. Mother can get antibody tested.

34 Zoonosis Congenital Toxoplasmosis 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

35 In-Class Discussion A pregnant client wants to get rid of their cat due to concerns about Toxoplasmosis. How would you educate your client?

36 In-Class Discussion Compare & Contrast Toxoplasmosis in various hosts.