## 3 Results and Discussion  
Out of the 2050 mites used in this study, 153 (44%) and 658 (39%) were found engerged in NC and SG devices, respectively, with median values of 24 and 20 mites, but the difference was not found to be significantly different (\(p\) = 0.08), despite just above the significance level. The incubation of fed mites allowed the generation of offspring, as listed in Table 2 and Table S1. While the feeding ability of mites was not influenced by the presence of \(S\). Gallinarum in the blood, the latter affected mite reproduction. In fact, ovipositing fed females were found in 43% of NC and 22% of SG mites, respectively, with a significant difference (\(p\) = \(<\)0.01). Similarly, the number of laid eggs by SG-fed mites was found to be significantly reduced (\(p\) \(<\) 0.01) with respect to the NC-fed mites. Likewise, the fecundity rate was \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**Negative Control**} & \multicolumn{2}{c}{_Salmonella_** Gallinarum**} & \multirow{2}{*}{\(p\)} \\ \cline{2-2} \cline{4-5}  & \(n\) & **CI95** & & & **CI95** \\ \hline Tested mites & 350 & - & 1700 & - & - \\ Fed mites & 153 & - & 658 & - & 0.08 \\ Egg-laying mites & 65 & - & 146 & - & \(<\)0.01 \\ Laid eggs * & 135 & - & 313 & - & \(<\)0.01 \\ Fed mites per device \(\dagger\) & 24 & - & 20 & - & \\ Egg-laying mites per device \(\dagger\) & 12 & - & 3 & - & \\ Feecundity rate * & 0.9 * & (0.5, 1.2) & 0.4 * & (0.3, 0.6) & \(<\)0.01 \\ \hline \hline \end{tabular}  
* CI95: 95% confidence interval.
* The number includes eggs, larvae, and protronyms. See the text for details. \(\dagger\) Each device contained 50 adult female mites.
* Eggs laid/fed mites ratio.
* Central value.  
\end{table} 
Table 2: Feeding and reproductive parameters observed in mites infected or not infected with _Salmonella enterica_ ser. Gallinarum. significantly lower in the SG mites (\(p\) = \(<\)0.001), with 0.9 eggs laid per female in the NC group and 0.4 in the SG group. Those results suggest that, while \(D\). _gallinae_ has almost the same chance to take a bloodneal on infected or non-infected animals, \(S\). Gallinarum seems to impair the reproduction of the infected mites, in terms of both oviposition and fecundity. Similar findings about the negative impact of \(S\). _enterica_ were previously reported for mites contaminated by \(S\). Enteritidis [26], relating such evidence to the localization of the pathogen in the reproductive apparatus of female mites. Actually, \(S\). Gallinarum was detected in adult PRMs fed on experimentally infected blood, as well as in eggs, larvae, and protonymphs from adults fed in SG devices. Out of them, 89% of pooled adult mites, 5% of single eggs, 17% of pooled eggs, 9% of pooled larvae, and 43% of pooled protonymphs were positive for \(S\). Gallinarum (Table 3). All pools of adults, eggs, larvae, and protonymphs from NC devices resulted negative. Those data evidenced the vertical transmission of \(S\). Gallinarum in \(D\). _gallinae_ from adults to eggs, larvae, and protonymphs. Considering the impact and the sanitary consequences of FT in affected farms, such evidence is particularly worrying. Indeed, the vertical transmission of \(S\). Gallinarum across the PRM life stages may play an important role in enhancing the circulation of the pathogen within and even among the chicken flocks. Reduced fertility does not appear to be a limiting factor for such a spread, as previously demonstrated [20]. This fact may be due to the huge number of mites that may infest the poultry farms, reaching up to 500,000 per hen [27]. In those conditions, a percentual reduction in fertility does not produce significant effects on the whole mite population. Apart from demonstrating the vertical transmission, the adopted system allowed to confirm that \(S\). Gallinarum can be orally introduced by PRM.