Significance

• According to Zoologix and the United States Department of Agriculture, Neospora is responsible for spontaneous abortion in dairy cattle around the world, and is a major cause of reproductive failure in New Zealand, the Netherlands and North and South America. According to Zoologix, 20 percent to 45 percent of bovine abortions in California drylot dairies are attributable to this disease. The parasite can move from dogs to many other species of animal, depending on the stage of its development.
  
  

Oocyst

• In the first stage of its life cycle, Neospora multiplies rapidly. This stage occurs only in dogs, which usually contract the disease by ingesting the second stage—tissue cysts—in the meat of infected animals. Dogs infected with the first stage may show no clinical signs, but still shed oocysts, a spore-form of the protozoan, in their feces. Intermediate hosts become infected by eating food or drinking water contaminated by these oocysts.
  
  

Tissue Cysts

• Once an intermediate host ingests an oocyst, tissue cysts form. The parasite migrates to both peripheral and central nervous system tissues and develops into a latent form. It can remain dormant in this stage for a long time. Possible intermediate hosts include sheep, horses, cattle, deer and goats.
  
  

Tachyzoite

• The final form of Neospora is the tachyzoite. This form occurs when the oocyst sporulates, or reproduces, in the environment outside a host animal. Sporulated oocysts in contaminated food or water do not form tissue cysts. This form of Neospora causes the most symptoms. It's capable of invading a variety of cell types and produces lesions, neuromuscular degeneration and eventually hind limb paralysis. It can be transferred from mother to fetus across the placenta, causing spontaneous abortion.
  
  

Considerations

• Because Neospora caninum has only been recently discovered, scientists don't have much information about its specific life cycle in the wild. This makes it difficult to create an effective preventive treatment for the protozoa. Pet and livestock owners must take care to examine their animals regularly, and have them tested for Neospora infection if any unusual signs appear.