Apicomplex pt 2 Flashcards
There is only one specie of toxoplasma within the genus (gondii), but there are many ________
Genotypes
- vary in virulence, transmission efficiencies, etc
Toxoplasma gondii is distributed _____
Worldwide
- seen on every continent
T. gondii definitive host
Felidae
- domestic and wild
Does T gondii have intermediate hosts?
Yes
- all warm-blooded animals (mammals and birds)
- serve as source of infection
Less common routes of transmission for T gondii
- blood transfusion: circulating stages of tachyzoites in blood
- organ transplant: could have tissue cysts present
Cats are infected with T gondii by getting exposed to ____
Sporulated oocysts
- typically get ingested by grazing animals exposed to soil
T gondii tissue cysts
Seen in intermediate hosts
- asexually reproducing
- only when cyst opens or gets compromised will you see disease
_______ transmission can happen in intermediate or definitive hosts
Transplacental
What 2 apicomplexa sporulate inside the host?
- sarcocystis
- cryptosporidium
What 5 apicomplexa sporulate outside the host?
- toxoplasma gondii
- hammondia
- isospora
- eimeria
- neospora
Toxoplasma gondii routes of infection
- ingestion of tissue cysts in IH
- ingestion of sporulated oocysts
T. gondii - protozoal stages in felids
Sexual stages in intestine (gametogony)
- fertilization –> unsporulated oocysts shed
Asexual stages: extraintestinal
- tachyzoites, bradyzoites
In the US ____ cats shed T gondii oocysts
1%
- greater percentage have antibody titiers
- oocyst re shedding is uncommon
Prepatent period
Time from infection until demonstration of oocysts in feces
T gondii - PPP
- ingestion of tissue cysts (bradyzoites) –> 3-10 days (efficient)
- ingestion of sporulated oocysts –> 20 days
Peak oocyst shedding occurs ______
6-7 days post infection
- oocyst shedding lasts 10-14 days, then decreases rapidly
T gondii - clinical signs
Subclinical
Feline toxoplasmosis
- concurrent infection, immunosuppression
- fever, weight loss, lethargy
- dyspnea, anorexia, abdominal discomfort, ichterus, retinochoroiditis, uveitis, encephalitis
- associated with multiple tachyzoites, granulomatous response
- multisystemic - primarily in lung, liver, ocular, brain
Cats with clinical disease are _______
Unlikely to be shedding oocysts
T gondii immune response is due to _______
Tachyzoites
Tissue cysts of T gondii contain ______
Bradyzoites
T gondii - sheep
Adults: major cause of sheep abortions in US via transplacental transmission (vertical)
T gondii - goats
Adults: abortions, clinical toxoplasmosis (liver, kidney, CNS)
T gondii - cattle
Resistant to infection
- seropositive, but not important epidemiologically
- tissue cysts are undetectable
Other hosts of T gondii
Chickens: seropositive, with tissue cysts (not documented in commercial flocks, only backyard ones)
Swine: domestic and feral are seropositive, clincial signs are rare
Horses: resistant
T gondii - dogs
Clinical toxoplasmosis is rare
- pneumonia, hepatitis, encephalitis
Vertical transmission is rare
T gondii - wildlife
Seroprevalence high in many populations (esp white tailed deer)
- clinical toxoplasmosis in multiple species including: marsupials, non human primates
T. gondii causes potential behavior changes in _______
Intermediate host
- extended phenotype of the parasite
- especially in murine hosts
- depends on strains, age of host, stage of infection
T gondii - diagnosis in felids
- fecal float: rarely detects oocysts
- subclinical
- serology: does not predict shedding
- IgM: peaks early (1-2 weeks PI)
- IgG: develops 2 weeks PI
- active infection requires demonstrating high titer
T gondii - diagnosis in IH
- clinical signs
- antibody titers
- PCR
- immunohistochemistry
- histology
Tachyzoites are _______
Banana shaped
T gondii - treatment/control
No vaccine or approved drugs
- remove feces daily
- do not feed cats raw food
- prevent carnivorism
T gondii - zoonosis
Vulnerable populations - pregnant women, immunosuppressed Primary source of infection - transplacental - organ transplants - meat sources - raw goat milk - environmental contamination
T gondii - human pathology
Immunocompetent patients - aysmptomatic or flu-like Immunocompromised - neurologic infection - exposure or reactivated dormant cyst = coma/death Placental transmission - abortion, hydrocephalus, blindness - associated with schizophrenia
Neospora caninum is similar to T gondii, except the DH is _______
Canids
- neuromuscular disease
- prevalent in strays, dogs around cattle
N. caninum IH
Cattle (small ruminants)
- primary cause of cattle abortion worldwide
Neospora caninum has a _____ life cycle only
Indirect
N caninum - PPP
5-17 days
- oocysts sporulate in environment in 24-72 hrs = 2 sporocysts with 4 sporozoites each
N caninum - route of infection
IH: oocyst, transplacental
DH: ingestion of tissue cyst, transplacental
N caninum - pathology DH
Usually subclinical
- congenitally infected puppies or immunocompromised
- signs are neuromuscular
- lesions: focal necrosis to severe myositis in skeletal muscles
N caninum congenital infection leads to _______
Asymptomatic carriers
N caninum - pathology IH
Cattle
- abortions (abortion storms)
- repeated abortions
- infected calves that survive are asymptomatic carriers or have clinical infections
N caninum - diagnosis
DH - fecal float for unsporulated oocysts - antibody titers IH - ELISA - test aborted calves with PCR, ELISA
N caninum - treatment and control
No approved treatment or vaccine
- limit access of dogs to cattle
- minimize fecal contamination
- remove aborted fetus
- herd management
Hammondia
Must be distinguished from toxoplasma and neospora
- oocysts are similar
- is non-pathogenic
- no extra-intestinal stage in IH
Hammondia infects IH only via ____
Ingestion of oocysts
Hammondia infects DH only via ________
Ingestion of tissue cysts
Hammondia sites of infection
DH: intestinal tract only
IH: throughout entire body
H. heydorni
DH: dog, coyotes
IH: herbivores
H. hammondi
DH: cat
IH: mammals, birds
Hammondia - life cycle
- oocyst: 2 sporocysts with 4 sporozoites each
- oocysts same size as toxo and neospora
- PPP: 1 week
- patent for 1-2 weeks
Neospora hughesi
Less common cause of equine protozoal myelitis
- primary cause is sarcocystis neurona
- DH: unknown
- IH: horse via transplacental
