Neospora caninum infection in cattle: Not only an economic problem

Neosporosis is an infectious disease of cattle and other species with a worldwide distribution. In Poland, the seropositivity rate for N. caninum among dairy cattle varies between 6% and 80%, with the highest number of seropositive cows in central and north-eastern voivodeships. In the United States, in 2003 the total annual cost of N. caninum infections was 657 million dollars, and in Great Britain in 2014 it was nearly 14 million pounds. N. caninum results in severe economic losses caused by a decreased milk yield, an increased number of culled cows, a higher newborn calf mortality rate and occasional birth defects. However, the most common result of this disease is abortion, which usually occurs between the 5th and 7th month of gestation. The risk of aborting is 3 times as high for seropositive cows as it is for seronegative cows; up to 21.6% vs. 7.3%, respectively. Cattle can become infected by consuming food and water contaminated with N. caninum oocysts, but the principal route is transplacental transmission usually between the 70th and 210th day of gestation. The ELISA test is most often used to detect the presence of specific antibodies in blood serum. PAG-2 level in the bloodstream can be a good marker for predicting Neospora-induced abortions – in seropositive cows, a level of more than 4.5 ng/ml on the 120th day of gestation means a 7-fold higher risk of pregnancy loss. According to research, live attenuated vaccines are highly efficacious in preventing neosporosis. Unfortunately, the currently available methods of prevention are based on the elimination of seropositive cows from the herd and the limitation of contact with the final hosts of N. caninum.