Foetal death in naive heifers inoculated with Neospora caninum isolate Nc-Spain7 at 110 days of pregnancy

Abstract

Neospora caninum infection is a leading cause of abortion in cattle worldwide. The pathogenesis of bovine neosporosis, particularly during the second term of gestation when most abortions occur in naturally infected dams, is poorly understood. In the present study foetal death was observed in 3 of 6 experimentally infected dams at 110 days of gestation after 6 weeks of experimental period. All experimental heifers were febrile between 3 and 5 days post infection (dpi). Inoculated dams seroconverted by 3-4 weeks post-infection with higher mean antibody titres in aborting dams compared to non-aborting heifers, although not significantly (p > 0.05). Neospora caninum DNA was detected in all infected foetuses and placentas, and three infected foetuses also had N. caninum antibodies. The parasite burden was higher in the brain of dead/aborted foetuses than in live foetuses. Interestingly, high IFN-γ production was detected in foetal fluids of a dead foetus found upon euthanasia of its dam, while no IFN-γ was observed in amniotic, allantoic and/or foetal fluids in the three infected foetuses that were alive upon maternal euthanasia. The present study confirms that the infection of dams on gestation day 110 with 10(7) tachyzoites of the Nc-Spain7 isolate causes abortion. The fact that some infected dams aborted and some did not is relevant to the understanding of N. caninum pathogenesis of abortion in naturally infected cows.

Influence of dose and route of administration on the outcome of infection with the virulent Neospora caninum isolate Nc-Spain7 in pregnant sheep at mid-gestation

“…The biphasic temperature response found in the subcutaneous challenge group (G5) had been previously described after subcutaneous challenge in sheep [ 11 , 28 , 30 ] and cattle [ 33 , 34 ]. Previous studies in cattle have described differences in rectal temperatures between aborting and non-aborting dams [ 19 , 35 ] in the same way as observed in G4 (10 2 , IV) in the present study.…”

“…With regard to clinical observations, foetal viability is the most significant parameter to be evaluated in an abortion model of neosporosis [ 14 ]. Infection of cattle at mid-term gestation with 10 7 tachyzoites of the Nc-Spain7 isolate caused foetal death in 50% of infected animals after an experimental period of 6 weeks [ 19 ]. All pregnant ewes intravenously infected with 10 5 tachyzoites (G1) aborted in the same way as pregnant ewes intravenously infected with a 10-fold higher dose (10 6 tachyzoites) [ 8 , 23 ].…”

“…Likewise, there are clear differences concerning the outcome of the infection among parasite isolates [ 14 ]. The Nc-Spain7 isolate [ 15 ] is a very well-characterized virulent isolate tested so far in three experimental ruminant models, sheep [ 8 ], goats [ 16 ] and cattle [ 17 – 19 ]. Recently, the Nc-Spain7 isolate has been evaluated at different times during gestation in pregnant sheep, suggesting that the time of infection plays a key role in the pathogenesis of the disease [ 8 ].…”

Differential susceptibility of bovine caruncular and trophoblast cell lines to infection with high and low virulence isolates of Neospora caninum

“…These differences may be explained by their biological diversity, as has been demonstrated in previous in vivo studies [ 16 , 18 , 20 , 29 , 32 , 51 , 52 ]. Nc-Spain7 showed a high neonatal mortality (95%) and vertical transmission rate (nearly 80%) in a pregnant BALB/c mouse model [ 31 ], as well as a percentage of abortion and vertical transmission as high as 100% in a bovine model [ 20 , 53 ]. However, Nc-Spain1H showed a 100% offspring survival rate and a low vertical transmission rate (5%) in a pregnant mouse model [ 29 ], and no foetal death was observed in experimentally infected cattle [ 18 ].…”

Evaluation of abortions spontaneously induced by Neospora caninum and risk factors in dairy cattle from Lima, Peru

“…Limiting of histopathology is the subjective criterion because need an expert evaluator, in contrast to PCR and ELISA that are objectives diagnostic test (ORTEGA-MORA et al, 2006). ELISA need a high level of antibodies to detect a positive sample; considering immunology system of fetus recollected is in developing, titers of antibodies may not reach cut-off ELISA, need more time to produces more immunoglubuline or the parasite burden was low (ALMERÍA et al, 2016;PEREIRA-BUENO et al, 2003) PCR diagnostic performance is very high, detecting presence of small amounts of N. caninum DNA in large quantity of sample; moreover, PCR detect DNA in tissues of autolysed fetuses (VAN MAANEN et al, 2004). In conclusion, PCR in our study demonstrated be more sensitivity than ELISA in aborted fetus samples.…”