Haemoplasma is a trivial name for haemotropic Mycoplasma spp., which can attach to the surface of red blood cells leading to deformity and anaemia in a wide range of mammalian animals, including pigs. In Thailand, there is only one study that reported the occurrence of Mycoplasma suis without other haemoplasma species. In this study, we examined the molecular occurrence and genetic diversity of porcine haemoplasmas in Thai domestic pigs (Sus scrofa domesticus) from commercial farms using a PCR assay targeting the 16S rRNA gene, DNA sequencing, nucleotide sequence type (ntST) analysis and phylogenetic analysis. A total of 665 blood samples were collected from pigs at thirteen farms located in eight provinces of Thailand during 2019–2020. Genomic DNA was extracted from blood samples and tested by PCR. The frequency of haemoplasma infection was 37.1% (247/665, 95% CI: 33.5%–40.9%) in all pigs. Among 247 PCR positive samples, 194 were sequenced and analysed by nucleotide BLAST, ntST diversity, phylogenetic trees and ntST networks. The results of this genetic analysis indicated that at least four species with 27 nucleotide sequence types (Mycoplasma suis, Mycoplasma parvum, Candidatus Mycoplasma haemosuis and a putative novel species) of porcine haemoplasmas were identified. Thus, it appears that haemoplasmas show a high genetic diversity in the Thai pig population. In addition, a putative novel species was genetically characterized by other markers, namely, the 23S rRNA and RNase P RNA (rnpB) genes. For phylogenetic analysis, Candidatus Mycoplasma haemosuis was placed into the Mycoplasma haemofelis group, and the three remaining species were placed into the Mycoplasma suis group in all trees containing the 16S rRNA, 23S rRNA and rnpB genes. Further studies, such as pathobiology and epidemiology, should be conducted to better characterize this putative novel species.
Duck Tembusu virus (DTMUV) is an important flavivirus that can be transmitted to poultry via Aedes albopictus bites. Furthermore, humans residing in the DTMUV epidemic area display activated antiviral immune responses to local DTMUV isolates during the pathogenic invasion, thereby raising the primary concern that this flavivirus may be transmitted to humans via mosquito bites. Therefore, we identified the gene AALF004421, which is a homolog of the 34-kDa salivary protein (34 kDa) of Ae. albopictus and studied the salivary protein-mediated enhancement of DTMUV infection in Ae. albopictus salivary glands. We observed that double-stranded RNA-mediated silencing of the 34 kDa in mosquito salivary glands demonstrated that the silenced 34 kDa impaired DTMUV infectivity, similar to inhibition through serine protease. This impairment occurred as a consequence of triggering the innate immune response function of a macroglobulin complement-related factor (MCR). 34-kDa in the salivary gland which had similar activity as a serine protease, results in the abrogation of antimicrobial peptides production and strong enhance DTMUV replication and transmission. Although the function of the 34 kDa in Ae. albopictus is currently unknown; in the present study, we showed that it may have a major role in DTMUV infection in mosquito salivary glands through the suppression of the antiviral immune response in the earliest stages of infection. This finding provides the first identification of a prominently expressed 34 kDa protein in Ae. albopictus saliva that could serve as a target for controlling DTMUV replication in mosquito vectors.
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