FieldDxNeosporosisClinical signs, differential diagnosis, treatment and prevention in cattle and horses.
Overview
A major cause of abortion in cattle, transmitted congenitally or from dog feces contaminating feed. Neospora caninum, a protozoan parasite; dogs are the definitive host.
Clinical signs
- Repeat abortions from the same cows can occur (sporadic or outbreaks common at 20%-40%) at 3 to 8 months of gestation (mean 5.5 months).
- Autolyzed midgestation fetus exhibits widespread histologic inflammatory lesions in the fetus, including nonsuppurative necrotizing encephalitis and myocarditis.
- Mummification and birth of full-term infected calves can occur with or without clinical signs.
- No characteristic gross lesions are present in the placenta, though the parasite may be present.
Predisposing factors
- Congenital transmission commonly occurs during pregnancy; acquired postnatal infection may also occur.
Look-alikes to rule out
Treatment
- In dogs, clindamycin has antiprotozoal activity against Neospora caninum tachyzoites and can be combined with trimethoprim-sulfa or pyrimethamine, though response is often partial or absent.
- In cattle, no approved treatment or vaccine exists; control relies on accurate diagnosis and preventing transmission (e.g. not breeding seropositive cows, controlling definitive-host dog access to feed).
Drugs mentioned: Pyrimethamine Clindamycin
Prevention
1. Test and cull or replace seropositive cows where cost-benefit supports it; use embryo transfer into seronegative recipients. 2. Breed seropositive dairy cows to beef sires to lower abortion risk. 3. Keep dogs and wild canids away from feed and water and protect stored feed from canine feces. 4.
Source
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Table 18-2)
MSD Veterinary Manual — Neosporosis in Animals (accessed 2026-09-21)
Condensed and attributed, never reproduced whole. Open the full entry in the app.