Hi, Ikhlas! When the infection occurs during gestation, the parasite invades the uterine cells, causing abortion, then the abortion is the result of the congenital transference of the tachyzoites to the fetus during gestation. 

I recomend you watch this movie: https://www.youtube.com/watch?v=N1Rn7F2yxPk 

Hi, normally losses occur after a primary infection during pregnancy but more commonly as the result of recrudescence of a persistent infection during pregnancy. That parasitaemia is followed by invasion of the parasite into placenta and fetus. It is suggested that abortion occurs when primary parasite-induced placental damage jeopardises fetal survival directly or causes release of maternal prostaglandins that in turn cause luteolysis and abortion. Fetal damage may also occur due to primary tissue damage caused by the multiplication of N. caninum in the fetus or due to insufficient oxygen/nutrition, secondary to placental damage. In addition, maternal immune expulsion of the fetus may occur associated with maternal placental inflammation and the release of maternal pro-inflammatory cytokines in the placenta.

Because neosporosis is only one of many causes of abortion, diagnostic efforts should focus on an array of possible causes. Aborted fetuses should be submitted to a veterinary diagnostic laboratory, together with placenta and a serum sample from the aborting dam. Examination of multiple fetuses increases the odds of accurate diagnosis. If it is impractical to submit an entire fetus, as many of the following specimens as possible should be submitted to exclude other causes of abortion: aseptically collected and chilled lung, liver, spleen, and abomasal fluid; an eyeball for nitrate testing; formalin-fixed specimens of brain (even if soft), lung, thymus, liver, kidney, spleen, adrenal gland, skeletal muscle (eg, tongue and diaphragm), and placental cotyledon; serum from the aborting dam; and thoracoabdominal fluid from the fetus for serology.

A diagnosis of neosporosis abortion can be made with great confidence from the following constellation of findings: 1) lack of other etiologic agents; 2) nonsuppurative inflammation in multiple fetal organs, especially including the brain, heart, and skeletal muscle; 3) immunohistochemical or PCR detection of Neospora in fetal tissues; and 4) Neospora seropositivity of the dam or fetus. However, such unequivocal findings are not always present. A lesion that is nearly specific for neosporosis abortion in cattle is multifocal cerebral necrosis surrounded by nonsuppurative leukocytic reaction. Confidence in the diagnosis increases with the strength of the Neospora antibody level in the aborting dam, with high seropositive reactions at the time of abortion having greater predictive value than low seropositive reactions. Neosporosis is generally excluded in seronegative dams.

Toxoplasmosis is a more common cause of abortion in sheep and goats and has lesions similar to those of neosporosis, but toxoplasmosis abortion in cattle is rare or nonexistent.

Serologic testing of multiple cows or heifers can be used as an alternative or complementary method to determine whether neosporosis is a major reproductive problem in a herd. This strategy can be helpful when investigating herds with endemic abortion problems. Serum samples should be collected from aborting dams and from an equal number of matched herdmates with normal gestation (generally ≥10 per group). Sera should be tested and classified for Neospora antibodies. If most cows in the aborting group are seropositive and few are seropositive in the normal group, then neosporosis should be suspected as a cause of abortion in the herd; this may be confirmed by statistical comparison. If most aborting cattle are seronegative, then neosporosis is unlikely to be a major problem.

Neospora caninum is one of the most important causes of abortion in cows. The occurrence of N. caninum infection in beef and dairy cattle has been reported worldwide, and in most provinces in Canada. The objective of this review is to summarize our current understanding of N. caninum in dairy and beef cattle for Canadian bovine practitioners. The review covers the life cycle of the agent, its mechanisms of transmission, clinical signs, and tests for diagnosing the infection. Data on the prevalence of the infection in Canadian dairy and beef cattle are reviewed and briefly compared with estimates from other parts of the world. Most importantly for Canadian bovine practitioners, the impacts of the infection, risk factors for its occurrence, and methods of control are also discussed. By reviewing the scientific literature on N. caninum from a Canadian perspective, culling decisions based on the interpretation of diagnostic tests are more effectively made in the control of N. caninum-associated disease.

REFERENCES

Thanks a lot Jose Ramon Vielma for this information ....

https://www.science.gov/topicpages/n/neospora+caninum+infections.html

Neospora can infect cattle by two main routes: dog to cattle and dam to calf - during pregnancy. Dog to cattle transmission occurs when cattle ingest Neospora oocysts in contaminated feed, water or from pasture. As a result, animals may become infected simultaneously, which can lead to abortion storms, where many cattle lose their foetuses within a short period. Dam to calf transmission may occur by two separate routes: 1) when the parasite, from a previous infection, is reactivated in the dam during pregnancy and 2) if the dam is newly infected with Neospora during pregnancy. In both cases the unborn calves become infected in utero. If the foetus survives the infection then they are born congenitally infected but may appear clinically normal. Infected heifers can transmit Neospora to their offspring in subsequent pregnancies. This transmission route is very effective and Neospora may be maintained within a herd for many generations.

may be secondary cosequences

Dear Dr. I.A. Marhoon

Neospora was first identified in dogs, the “definitive” host of the parasite that can produce Neospora oocysts (eggs) in their faeces. If a dog eats infected meat, then the parasite can invade and multiply within gut cells and Neospora oocysts will be excreted in the faeces a few days later. The dog’s immune system will usually control the infection within a few weeks and shedding of oocysts will cease. In subsequent infections, parasites are controlled quicker and only insignificant numbers of oocysts are produced. As a result, shedding is mostly seen in younger dogs, after their first exposure to the parasite. The oocysts can survive in the environment for many months and be a source of infection for many other host species including cattle.

Neospora can infect cattle by two main routes: dog to cattle and dam to calf - during pregnancy. Dog to cattle transmission occurs when cattle ingest Neospora oocysts in contaminated feed, water or from pasture. As a result, animals may become infected simultaneously, which can lead to abortion storms, where many cattle lose their foetuses within a short period. Dam to calf transmission may occur by two separate routes: 1) when the parasite, from a previous infection, is reactivated in the dam during pregnancy and 2) if the dam is newly infected with Neospora during pregnancy. In both cases the unborn calves become infected in utero. If the foetus survives the infection then they are born congenitally infected but may appear clinically normal. Infected heifers can transmit Neospora to their offspring in subsequent pregnancies. This transmission route is very effective and Neospora may be maintained within a herd for many generations.

hello dear neospora  cause abortion as Toxoplasma gondi when tacchyzoit trans through placenta to foetus 

Neospora can infect cattle by two main routes: dog to cattle and dam to calf - during pregnancy. Dog to cattle transmission occurs when cattle ingest Neospora oocysts in contaminated feed, water or from pasture. As a result, animals may become infected simultaneously, which can lead to abortion storms, where many cattle lose their foetuses within a short period. Dam to calf transmission may occur by two separate routes: 1) when the parasite, from a previous infection, is reactivated in the dam during pregnancy and 2) if the dam is newly infected with Neospora during pregnancy. In both cases the unborn calves become infected in utero. If the foetus survives the infection then they are born congenitally infected but may appear clinically normal. Infected heifers can transmit Neospora to their offspring in subsequent pregnancies. This transmission route is very effective and Neospora may be maintained within a herd for many generations.

Hi , i want to know how Neosporosis cause abortion in cattle?. Available from: https://www.researchgate.net/post/Hi_i_want_to_know_how_Neosporosis_cause_abortion_in_cattle [accessed May 8, 2017].