Protozoa V: Apicomplexa Toxoplasma, Neospora Flashcards
Describe Toxoplasma gondii
Only species in the genus, but has many genotypes
Common
Can infect many vertebrates
Can cause multi-systemic disease, but can also be covert
Distributed worldwide
What is the definitive host of Toxoplasma gondii?
Felidae (domestic and wild)
What is the intermediate host of Toxoplasma gondii?
Almost all warm-blooded animals
What is the Toxoplasma gondii life cycle?
Tissue cysts from intermediate host is ingested by cat
Unsporulated oocysts passed in feces
Sproulates in 1-2 days
Sporulated oocysts in feed, water, or soil are ingested by intermediate host and warm-blooded vertebrates (cycle starts over with cat)
Warm-blooded vertebrates ingest contaminated food and water or uncooked meat
Tachyzoites are transmitted through the placenta
What parasites sporulate outside the host?
Toxoplasma gondii Hammondia Isospora Eimeria Neospora
What parasites sporulate inside the host?
Sarcocystis
Cryptosporidium
What are the routes of infection with Toxoplasma gondii?
Ingestion of tissue cysts in IH
INgestion of sporulated oocysts
What are the Toxoplasma gondii protozoal stages in felids?
Sexual stages in intestine (gametogony): fertilization—unsporulated oocysts shed
Asexual stages are extra-intestinal (tachyzoites, bradyzoites)
What is a prepatent period?
Time from infection until demonstration of oocysts in feces
What is the PPP with ingestion of Toxoplasma gondii tissue cysts?
3-10 days (most efficient route)
What is the PPP with infestion of Toxoplasma gondii sporulated oocysts?
About 20 days
When is peak oocyst shedding of Toxoplasma gondii? How long does it last?
6-7 days post infection
Lasts about 10-14 day, then decreases rapidly
What are the clinical signs of Toxoplasma gondii in Felids?
Usually subclinical
Feline toxoplasmosis
Cats with clinical disease are unlikely to be shedding oocysts
What is Toxoplasma gondii a major cause of in adult sheep in the US?
Abortions
What is the transmission of Toxoplasma gondii in sheep?
Vertical transmission: congenitally infected offspring
What is Toxoplasma gondii associated with in goats?
Primarily abortions
Clinical toxoplasmosis
What is the transmission of Toxoplasma gondii in goats?
Vertical transmission: congenitally infected offspring
What is the transmission risk of Toxoplasma gondii between humans and goats?
Raw goat milk
Undercooked meat
Describe Toxoplasma gondii in cattle
Cattle are resistant to infection
Seropositive, but not epidemiologically important
No reports of clinical toxoplasmosis
Tissue cysts typically undetectable
Describe Toxoplasma gondii in chickens
Seropositive and have tissue cysts
Commercial flocks: clinical toxoplasmosis not documented
Backyard flocks: lesions and necrosis in brain
Describe Toxoplasma gondii in swine
Domestic and feral populations are seropositive
Clinical toxoplasmosis is rare
Describe Toxoplasma gondii in horses
Resistant: no reports of clinical cases
Describe Toxoplasma gondii in dogs
Clinical toxoplasmosis is rare
Vertical transmission rare
Describe Toxoplasma gondii in wildlife
Seroprevalence high in many wildlife populations
Clinical toxoplasmosis in multiple species including marsupials, non-human primates, etc.
Marine animals impacted from water run-off
What is seen in IH infected with Toxoplasma gondii?
Behavioral changes
What are the methods of diagnosis of Toxoplasma gondii in Felid definitve host?
Fecal float (rarely detects oocysts
Usually subclinical
Serology
Describe serology for Toxoplasma gondii
Does not predict oocyst shedding
IgM peaks early
IgG develops 2 weeks post infection
Active infection requires demonstrating rising titer
What are the methods of diagnosis of Toxoplasma gondii in the intermediate host?
Clinical signs Antibody titers PCR Immunohistochemistry Histology
What are methods of treatment for Toxoplasma gondii?
No vaccine
No approved drugs, but off-label options (Clindamycin hydrochloride)
What are methods of control for Toxoplasma gondii?
Remove feces daily
Feed cats dry/canned/cooked meat only
Prevent carnivorism/hunting
What are vulnerable populations that can be infected with Toxoplasma gondii?
Pregnant women
Immunosuppressed individuals
What are the primary sources of infection of Toxoplasma gondii?
Transplacental/transmammary Organ transplants/blood transfusions Meat sources Raw goat milk* Environmental contamination
What is the pathology for Toxoplasma gondii in immunocompetent patients?
No symptoms to flu-like symptoms for a few weeks
What is the pathology for Toxoplasma gondii in immunocomprised patients?
Most frequent neurological infections
Toxoplasma encephalitis
What is the pathology for Toxoplasma gondii in the transmission from pregnant mother to unborn fetus?
Stillbirths, abortion, hydrocephalus, microcephalus, blindness
Congenital infections develop later in life
What life cycle does Neospora caninum?
Indirect life cycle only
How is Neospora caninum different from T. gondii?
DH: Canids
—Neuromuscular disease
—HIgh seroprevalence in strays and dogs around cattle
IH: Cattle
—Primary cause of cattle abortion worldwide
—Antibody titers in a wide range of hosts
Describe the Neospora caninum life cycle
Definitive host: dog
Dogs can get reinfected
Sporulated oocysts in food, water, and soil are ingested by intermediate host
Dog ingests infected tissue cyst (e.g. in aborted fetus or infected calf)
What is the PPP of Neospora caninum?
5-17 days
Oocysts sporulate in environment in 24-72 hours
When sporulated: 2 sporocysts/4 sporozoites each
What are the routes of infection for Neospora caninum?
IH: oocyst. transplacental
DH: ingestion of tissue cyst, transplacental
What are the clinical signs and pathology of Neospora caninum in dogs (DH)?
Usually subclincial
Clinical infection
—Congenitally infected puppies or immunocompromised dogs
—Signs are usually neuromuscular
—Lesions: focal necrosis to sever myositis in skeletal muscles
Congenital infection—asymptomatic carriers
What are the neuromuscular signs associated with Neospora caninum?
Progressive hind limb paralysis
Muscle atrophy
Difficulty swallowing
What are the clinical signs and pathology of Neospora caninum in IH?
Cattle:
Abortions (Abortion storms; stillbirths)
Infected calves that survive are asymptomatic carriers or have clinical infection
What is the method of diagnosing Neospora caninum in DH?
Fecal flotation: unsporulated oocysts
Antibody titers in dogs vary widely
What is the method of diagnosing Neospora caninum in IH?
Cattle: antibody test using serum or milk (ELISA); multiple testing
Aborted calves: brain, fetal fluid, placental tissue collected for histology
Other hosts: histology
What are the methods of treatment of Neospora caninum?
No approved treatment
No vaccine available
What are methods of control of Neospora caninum?
Limited access of dogs to cattle
Minimize fecal contamination, by dogs, of food and water
Remove aborted cattle fetus/placenta/stilbirths
Herd management: culling. testing
What must Hammondia be distinguished from? Why?
Toxoplasma and Neospora
Oocysts have similar appearance/size
What makes Hammondia different from Toxoplasma and Neospora?
It is non-pathogenic
Has no extra-intestinal stage in DH
Infects IH only via ingestion of oocysts
Infects DH only via ingestion of tissue cysts
What is the DH of Hammondia heydorni?
Dogs, coyotes
What is the IH of Hammondia heydorni?
Herbivores
What is the DH of Hammondia hammondi?
Cat
What is the IH of Hammondia hammondi?
Mammals, birds
What is the site of infection in hosts with Hammondia?
DH: intestinal tract only
IH: throughout entire body
Where does Hammondia sproulate?
Outside the host
What is the treatment for Hammondia?
None
What is the control for Hammondia?
Proper sanitation
What is the pathology for Hammondia?
None
What is the Hammondia oocyst like?
2 sporocysts with 4 sporozoites each
What is the PPP for Hammondia?
1 week
How long is Hammondia patent?
1-2 weeks
What is Neospora hughesi the less common cause of?
Equine Protozoal Myelitis
Describe the life cycle of Neospora hughesi
Poorly understood DH: unknown IH: horse ---Transplacental transmission ---Clinical signs and treatment similar to EPM
