Bartonella quintana Transmission from Mite to Family with High Socioeconomic Status

considerable genetic distance from them. Isolates in the outbreak in China had only a minor nucleotide sequence variation from the Thailand isolates, indicating that the virus has a high genetic relatedness to the Southeast Asia strain. However, previous studies showed that isolates from Europe, South Korea, and China were serologically identical to the prototype CV777 strain (1,4). To our knowledge, fecal–oral transmission is probably the main or only route of PEDV transmission (5–7). In our study, if a fecal sample from a sick piglet was found to be positive for PEDV, we also collected and studied milk from its mother. These results showed that PEDV was present in sow milk (online Technical Appendix Table 3), but the detection rate was lower for these samples (40.8%) than for the fecal samples (82.0%). On the basis of these results, we hypothesize that sow milk could represent a possible (and potentially major) route for the vertical transmission of PEDV from sow to suckling piglet. This hypothesis could be indirectly verifi ed by our fi eld observation that piglet death rates decreased as a result of fostering (data not shown). Our fi ndings show that PEDV was identifi ed not only in fecal samples from sick piglets, as expected, but also in the milk of the sow, which suggests vertical transmission of the virus.