Early Neospora caninum infection dynamics in cattle after inoculation at mid-gestation with high (Nc-Spain7)- or low (Nc-Spain1H)-virulence isolates

Abstract

Early Neospora caninum infection dynamics were investigated in pregnant heifers intravenously inoculated with PBS (G-Control) or 107 tachyzoites of high (G-NcSpain7)- or low (G-NcSpain1H)-virulence isolates at 110 days of gestation. Serial culling at 10 and 20 days post-infection (dpi) was performed. Fever was detected at 1 dpi in both infected groups (P < 0.0001), and a second peak was detected at 3 dpi only in G-NcSpain7 (P < 0.0001). At 10 dpi, Nc-Spain7 was detected in placental samples from one animal related to focal necrosis, and Nc-Spain7 transmission was observed, although no foetal lesions were associated with this finding. The presence of Nc-Spain1H in the placenta or foetuses, as well as lesions, were not detected at 10 dpi. At 20 dpi, G-NcSpain7 animals showed almost 100% positive placental tissues and severe focal necrosis as well as 100% transmission. Remarkably, foetal mortality was detected in two G-NcSpain7 heifers. Only one animal from G-NcSpain1H presented positive placental samples. No foetal mortality was detected, and lesions and parasite transmission to the foetus were not observed in this group. Finally, 100% of G-NcSpain7 heifers at 20 dpi presented specific antibodies, while only 60% of G-NcSpain1H animals presented specific antibodies at 20 dpi. In addition, earlier seroconversion in G-Nc-Spain7 was observed. In conclusion, tachyzoites from Nc-Spain7 reached the placenta earlier and multiplied, leading to lesion development, transmission to the foetus and foetal mortality, whereas Nc-Spain1H showed delayed infection of the placenta and no lesional development or transmission during early infection.

Crosstalk between Neospora caninum and the bovine host at the maternal-foetal interface determines the outcome of infection

“…However, in vitro models cannot mimic the complex architecture of the bovine placenta, as they lack the microenvironmental influences and the host ability to compensate for stress conditions. Recently, we used an in vivo model of bovine infection at mid-gestation to study the early infection dynamics (10 and 20 days postinfection, dpi) after experimental challenge with highand low-virulence isolates of N. caninum (Nc-Spain7 and Nc-Spain1H, respectively) [13]. The results confirmed marked differences in virulence.…”

“…A full description of the animals and experimental design have been previously published [13]. Briefly, pregnant Asturian heifers (n = 24) were randomly distributed into three experimental groups inoculated intravenously at 110 days of gestation with phosphate-buffered saline (PBS G-control; n = 6) or 10 7 culture-derived tachyzoites of the Nc-Spain7 isolate (G-NcSpain7; n = 9) or the Nc-Spain1H isolate (G-NcSpain1H; n = 9).…”

Spatial Distance Between Sites of Sampling Associated With Genetic Variation Among Neospora Caninum in Aborted Bovine Foetuses From Northern Italy

“…virulence for foetuses [52]. Nevertheless, virulence differences have been observed among N. caninum strains also in its main intermediate host, the cattle [15,17,18,20,21,22,23], and it would be fascinating to know, to which extent differences in microsatellite loci contribute to virulence. Recently, highly virulent isolates of N. caninum were shown to express a subset of particular secreted proteins in more abundance [53].…”

“…Nevertheless, N. caninum is less uniform than the previously mentioned study [11] suggests. In fact, different N. caninum isolates show large differences in vitro [14,15,16] and in vivo [17,18,19], also in cattle [20,21,22,23]. The pioneering work of Regidor et al [24] contributed a number of microsatellite markers that allow to ngerprint N. caninum isolates or DNAs and undertake population studies.…”

Proteomic Characterization of Host-Pathogen Interactions during Bovine Trophoblast Cell Line Infection by Neospora caninum

“…In addition, some differences in parasite-trophoblast interactions between isolates have been described [5,6]. Parasite intraspecific variation in virulence has been widely demonstrated, and isolates have been characterized with low (e.g., Nc-Spain1H), moderate (e.g., Nc-1) and high virulence (e.g., Nc-Liv, Nc-Spain7) according to their capacity to produce foetal death after infection of dams during pregnancy [7][8][9][10][11].…”