Neospora spp. (1)

Question 1

What are the intermediate hosts?

Answer 1

Dogs

Cattle

White-tailed deer

Water buffaloes

Sheep

Goats

Horses

Other species

Question 2

How do you identify?

Answer 2

Spherical Oocysts

 - Colorless
 - Thin, smooth outer wall
 - Up to 12 micro m

Question 3

Explain the life cycle

Answer 3

Not completely understood

Originally confused with Toxoplasma

FH - Gametogony in intestine
- Bradyzoites in cysts (in neural cells) - infective stage for final hosts
- When fed tissue cysts (bradyzoites), produce Unsporulated
Oocysts in feces
- Sporulation occurs outside host
- Results in 2 Sporocysts each with 4 sporozoites
- Spporulated oocyst - infective stage to IH

In IH
- Sporulated Oocysts ingested
- Excyst in intestine and sporozoites penetrate intestine and
sporozoites penetrate intestine and can then enter cells
extraintestinally
- Group of tachyzoites formed
- Rupture and each tachyzoite enters another cell and replicates
- Tachyzoites found in many cell types
- Neural, macrophages, fibroblasts, vascular endothelium of
kidney and liver
- Tachyzoites cross placenta
- Replicates in fetus
- Cysts containing bradyzoites formed
- Cysts found only in neural cells
- Most infections in cattle and dogs occurs transplacentally

Question 4

What are the sites of infection?

Answer 4

Intracellular parasites

 - FH - Epithelial or other intestinal cells
 - IH - Many cell types with predilection site for CNS

Question 5

Describe the Pathogenesis

Answer 5

Lesions occur in CNS, heart, skeletal muscle, kidney, and liver
- All organs can be affected

Multiplication of tachyzoites cause cells to die

Abortion at 3 months to term (mostly 4-6 months) - only clinical signs in
COWS

Fetus may die in utero or be born alive but diseased

Necropsy of fetus (affected calves)

 - Brain is most consistently infected organ
 - Encephalitis 
 - Characteristic lesion

Neurologically associated limb defects in calves

Repeat abortions

Decrease milk production

Major cause of abortion in dairy cows
- Responsible for 10-20% of abortions

Question 6

How do you diagnose?

Answer 6

Samples of tissue at necropsy

Serological tests - serum or CSF

T. gondii must be differentiated from Sarcocystis spp. (in cattle), S. neurona (in horses), and Neosspora caninum (in dogs)

Question 7

How do you treat and prevent?

Answer 7

Cattle - No drug effective

Control

 - Hygiene
 - Protecting water/feed sources from contamination with feces

Disposal of aborted fetuses - prevent infection in unaffected animals

Vaccine for use in healthy pregnant cattle during their 1st trimester as an aid to reduce abortion

Question 8

What are the final hosts?

Answer 8

Dogs

Coyotes

Other canids