Neospora Neospora was one of one of those hot topic health issues for discussion during our 2021-member forum meetings. Here, Gerard te Lintelo MRCVS explains the parasite-based disease’s life cycle, what to look out for, testing, treatment and prevention. Whilst testing remains optional, he reminds that annual testing of all female breeding animals as per the CHeCS scheme should be routine; herds require three consecutive clear annual herd screens to obtain risk level 1 status.
Introduction Neosporosis was first discovered in cows with abortions in the UK in 1987. This disease is nowadays recognized as a major cause of reproductive problems and abortion in cows and it can have a significant economic impact. Neosporosis is caused by Neospora caninum (N. caninum), a tiny parasitic single-cell protozoal organism about half the size of a red blood cell that can invade and live inside animal cells.
Transmission N. caninum has a unique life cycle (fig.1). Cows are intermediate hosts and dogs, and other canines like wolves, are the definitive hosts. A definitive host is an animal which harbours the adult parasite and where the parasite reproduces sexually and sheds eggs. An intermediate host is an animal which harbours the larval stage(s) or the asexual forms of the parasite. N. caninum is spread either vertically from one generation to the next generation within one species (cow to calf) or horizontally from one host to the other - dog to cow or cow to dog. Vertical transmission is considered to be the principle route of N. caninum infection in cattle and this vertical transmission maintains the infection within a herd.
Horizontal transmission from definitive host to cows This occurs mainly when a cow becomes infected from eating dog faeces through contaminated feed and water supplies. After infection N. caninum will spread from the cow’s digestive system to other tissues in the cow. This can then cause 94
Fig. 1 Neospora life cycle
acute infection - abortion, or N. caninum can change into a dormant state by hiding in tissues. The incidence of horizontal transmission in cows is generally low. However, an abortion storm can be seen when multiple animals within a herd have been exposed to the same contaminated feed and or water. Dogs usually acquire N. caninum by eating infected placentae, foetuses or dead calves.
often seen when seropositive animals can be traced through maternal family lines within a herd. The probability of a seropositive dam producing a calf that is seropositive prior to consumption of colostrum is around 95%. Note that these antibody-positive calves can appear clinically normal at birth.
Vertical transmission in cows
N. caninum can cause encephalomyelitis inflammation of the brain and spinal cord, in calves infected during pregnancy. This can have the following consequences; early embryonic death, abortion, stillbirth or birth of a feeble abnormal calf or birth of a normal calf with no obvious effect of N. caninum infection. The following scenarios can be seen on farms.
The main route of infection in cattle is trans-placental from dam to calf and the same cow can pass the infection on to multiple offspring. N. caninum infection is thought to be maintained by vertical infection on most farms. This is practically
Beef Shorthorn Cattle Society Journal 2022
Clinical manifestations
