Abstract
Neospora caninum has been detected only sporadically in cases of ovine abortion, and it has therefore traditionally been considered as an unimportant parasite in small ruminants. This study was carried out with the aim of identifying the pathogen causing serious reproductive problems on a commercial sheep farm. Sera from all rams and ewes tested negative for antibodies against Border disease virus, Schmallenberg virus and Coxiella burnetii, and infections by these agents were therefore ruled out. Nevertheless, seropositivity to N. caninum and/or Toxoplasma gondii was detected, although the seroprevalence was higher in the case of N. caninum. The percentage of lambings and the number of lambs per dam were significantly lower in ewes that were seropositive to N. caninum while no effect on these parameters was detected in ewes that were seropositive to T. gondii. There was also no evidence of infection by T. gondii in the foetal/lamb tissues analyzed by PCR and/or immunohistopathological techniques. On the contrary, the DNA of N. caninum was detected in 13 out of 14 foetuses/lambs descendant from dams seropositive to this parasite. Characteristic lesions caused by N. caninum and/or its antigen were also detected. Genotyping of the N. caninum DNA revealed only two closely related microsatellite multilocus genotypes. The results clearly demonstrate that infection by N. caninum was the cause of the low reproductive performance of this sheep flock.
Highlights
Reproductive failure of infectious aetiology is often identified as one of the primary causes of underperformance in ruminant livestock
The protozoan pathogens Neospora caninum and Toxoplasma gondii are often associated with this failure: N. caninum is currently considered the main cause of abortion and neonatal death in cattle, whereas T. gondii has traditionally been thought to be one of the principal agents causing abortion in sheep [1,2,3,4,5]
Seropositivity to N. caninum and T. gondii was detected in the flock at both sampling times
Summary
Reproductive failure of infectious aetiology is often identified as one of the primary causes of underperformance in ruminant livestock. The protozoan pathogens Neospora caninum and Toxoplasma gondii are often associated with this failure: N. caninum is currently considered the main cause of abortion and neonatal death in cattle, whereas T. gondii has traditionally been thought to be one of the principal agents causing abortion in sheep [1,2,3,4,5]. Research on the aetiology of ovine abortion is scarce and may not reflect the current epidemiological situation of neosporosis and toxoplasmosis, at least in some geographical areas. The aetiological diagnosis of ovine abortion induced by protozoa has been based on histopathological examination of foetal tissues. Regarding the in vivo diagnosis of infected sheep, different serological techniques based on antibody detection have been used to determine the seroprevalence of both infections in different geographical areas [8,9,10,11].
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