Effect of parity segregation on Mycoplasma hyopneumoniae infection dynamics and pneumonic lesions in pigs

ABSTRACT: Gilts represent a group risk for Mycoplasma hyopneumoniae vertical transmission in swine herds. Therefore, parity segregation can be an alternative to control M. hyopneumoniae infections. The study evaluated the effect of parity segregation on M. hyopneumoniae infection dynamics and occurrence and severity of lung lesions at slaughter. For that, three multiple site herds were included in the study. Herd A consisted of the farm where gilts would have their first farrowing (parity order (PO) 1). After the first farrowing PO 1 sows were transferred to herd B (PO2-6). Herd C was a conventional herd with gilt replacement (PO1-6). Piglets born in each herd were raised in separated nursery and finishing units. Sows (n = 33 (A), 37 (B), 34 (C)) in all herds were sampled prior to farrowing and piglets (n = 54 (A), 71 (B), 66 (C)) were sampled longitudinally at 21, 63, 100, 140 days of age and at slaughter for M. hyopneumoniae detection by PCR and lung lesions scoring. M. hyopneumoniae prevalence in sows did not differ among herds. Prevalence of positive piglets was higher at weaning in the PO1 herd (A) (P < 0.05). However, prevalence of positive pigs from 100 days of age to slaughter age was higher in the PO2-6 herd (B) (P < 0.05). Lung lesion occurrence and severity were higher in herd B. The authors suggested that the lack of a proper gilt acclimation might have influenced the results, leading to sows being detected positive at farrowing, regardless of the parity.

Fc-Mediated E2-Dimer Subunit Vaccines of Atypical Porcine Pestivirus Induce Efficient Humoral and Cellular Immune Responses in Piglets

Congenital tremor (CT) type A-II in piglets is caused by an emerging atypical porcine pestivirus (APPV), which is prevalent in swine herds and a serious threat to the pig production industry. This study aimed to construct APPV E2 subunit vaccines fused with Fc fragments and evaluate their immunogenicity in piglets. Here, APPV E2Fc and E2ΔFc fusion proteins expressed in Drosophila Schneider 2 (S2) cells were demonstrated to form stable dimers in SDS-PAGE and western blotting assays. Functional analysis revealed that aE2Fc and aE2ΔFc fusion proteins could bind to FcγRI on antigen-presenting cells (APCs), with the affinity of aE2Fc to FcγRI being higher than that of aE2ΔFc. Moreover, subunit vaccines based on aE2, aE2Fc, and aE2ΔFc fusion proteins were prepared, and their immunogenicity was evaluated in piglets. The results showed that the Fc fusion proteins emulsified with the ISA 201VG adjuvant elicited stronger humoral and cellular immune responses than the IMS 1313VG adjuvant. These findings suggest that APPV E2 subunit vaccines fused with Fc fragments may be a promising vaccine candidate against APPV.

Genotype diversity of Mycoplasma Hyopneumoniae in Chinese swine herds based on multilocus sequence typing

Background Between 2018 and 2020, 989 clinical specimens from pigs showing clinical signs of a variety of swine diseases in 27 provinces in China were sampled and submitted for further testing. Nested PCR targeting the 16S rRNA gene of Mycoplasma hyopneumoniae and subsequent sequencing were used to analyse these specimens. Mycoplasma hyopneumoniae-positive samples were assayed by multilocus sequence typing (MLST). The aim of the study was to reveal the distribution of M. hyopneumoniae and determine the genotypes of M. hyopneumoniae in pig herds in China based on MLST. Results Among these 989 samples, 199 samples were M. hyopneumoniae-positive. The M. hyopneumoniae positivity rate was 7.2% (35/494) in 2018, 18.4% (38/207) in 2019, and 43.8% (126/288) in 2020. In total, 47 samples were successfully assayed by MLST. Sixteen new M. hyopneumoniae sequence types from 9 provinces were recorded in the present study. Conclusions This is the first report on sample positivity rates and molecular typing results for M. hyopneumoniae in swine herds in China. MLST has revealed high genotype diversity among M. hyopneumoniae from different provinces of China.

Assessment and Appliction of Whole-Herd-Sampling, qPCR-Based-Testing, and Precision-Removal Method in Eliminating ASFv in Four Large Swine Herds in China

Since the first report of ASFV in China in 2018, conventional whole herd depopulation method to control ASF has proved unwieldly because of high production intensity and complex trade network. To provide an alternative to conventional methods, we evaluated the feasibility of implementating an extensive sampling method and qPCR tests to determine the status of ASFV in herds, with a rapid response to identified outbreaks. By assessing and applying these methods without whole herd depopulation, we successfully controlled ASF and eliminated the virus from 4 large swine herds. The time to negative herd was 19, 28, 14, and 1 days in farms 1-4 respectively. Retention rates of pigs of farm 1 to farm 4 was 69.7%, 65%, 99.4% and 99.72% respectively. We anticipated that this innovative method would replace the conventional stamping out one and greatly facilitate the control and eradication of ASFV in China and worldwide.

506 Late-Breaking: Rapid Weight Assessment of Finishing Pigs

Accurate pig body weight assessment is an important factor in managing swine herds and imperative when determining acceptable market weights. Pigs marketed outside the desired weight range established by the packer can lead to severe economic loss to the producer. This study’s objective was to validate new weight measurement technologies and determine their usefulness on swine farms. Accuracy of three methods were evaluated: human observation, a walk-across platform scale (CIMA; Correggio, Italy), and PigVision mounted cameras (Asimetrix Inc; Durham, NC). Weights were validated with a calibrated livestock scale in all three studies. In the first study, a trained individual selected pigs estimated to be market weight at two sites. Site one had 468 pigs and an accuracy of 84.4%, site two had 522 pigs and an 82.5% accuracy. A 16-week study was then conducted to determine PigVision camera accuracy over time from placement to market. Cameras were mounted above 12 pens. Weights were validated every two weeks. The accuracy for pigs that weighed 32.7 kg (87.7%) was lower (P &lt; 0.05) than the accuracy for pigs that weighed 117.5 kg (97.6%) or 125.7 kg (96.6%). The overall accuracy from placement to market was 94.1%. A final study at market compared human observation, the walk-across scale, and PigVision. A total of 91 pigs were weighed with each method. The accuracy for the walk-across scale was 98.2%. The walk-across scale did not register a weight for six pigs. Final accuracies were 88.2% for human observation, and 96.6% for PigVision. Human observation is the chosen method in many operations today yet offers the lowest accuracy. The walk-across scale is easy to operate but requires tactical animal movement. PigVision is the least arduous option, provides constant data, but does require maintenance. This work was funded by the National Pork Board.

Distribution of Leptospira Serogroups In Swine Herds In France, 2007 - 2017

Background: Leptospirosis is a widespread zoonotic disease caused by pathogenic Leptospira and is responsible for significant economic losses in porcine livestock. Knowledge of Leptospira serogroups and their distributions is important for evaluating the relevance of leptospirosis management measures, including the use of the prophylactic vaccine recently made available in France.A retrospective study was conducted to determine the distribution of Leptospira serogroups. Pigs from across France presenting clinical signs suggestive of leptospirosis were tested by micro-agglutination test between 2007 and 2017. We used a weighted average to determine the serogroup distributions according to the MAT results, considering cross reactions.Results: A total of 19,395 pig sera, mostly from Brittany, were tested, and 22.7 % were found to be positive for at least one Leptospira serogroup. In analysing the 4346 seropositive results for which the putative infective serogroup could be defined, we found that two serogroups out of ten were much more frequent than the others: Australis (48.5 %) and Icterohaemorrhagiae (38.2 %). Other serogroups, including Autumnalis, Panama, Ballum, Tarassovi, Sejroe, Grippotyphosa, Bataviae, and Pomona, were less common. Conclusion: Although data from diagnostic laboratories are prone to selection bias, using such a large amount of data provides a relevant overview of Leptospira distribution in space and time. Extracting epidemiological information with a standardized approach could be used for surveillance and support prophylactic strategies. Along the last decade, provide protection against the serogroups Australis and Icterohaemorrhagiae could prevent most of the clinical porcine leptospirosis in France.

Pilot Investigation of Anti-Salmonella Antibodies in Oral Fluids from Salmonella Typhimurium Vaccinated and Unvaccinated Swine Herds

Oral fluid (OF) can be a simple, cheap and non-invasive alternative to serum or meat juice for the diagnosis and surveillance of important pathogens in pigs. This study was conducted on four Salmonella Typhimurium-positive farrow-to-finish pig farms: two Salmonella-vaccinated (V) and two non-vaccinated (NV). Gilts and sows in the V farms were vaccinated with a live, attenuated vaccine prior to farrowing. Pooled faecal and OF samples were collected from the sows and their offspring. Salmonella was isolated according to ISO6579–1:2017. In parallel, IgG and IgA levels were assessed in OF samples using a commercial ELISA assay. Salmonella was detected in 90.9% of the pooled faecal samples from the NV farms and in 35.1% of the pooled faecal samples from the V farms. Overall, a higher prevalence was observed in the pooled faecal samples from the offspring (76.3%) compared to the sows (36.4%). IgG antibodies measured in V farms are likely to be related to vaccination, as well as exposure to Salmonella field strains. The detection of IgA antibodies in OF was unreliable with the method used. The results of this study show that IgG is the most reliable isotype for monitoring Salmonella-specific antibody immunity in vaccinated/infected animals via OF.

Update on the Phylodynamics of SADS-CoV

Coronaviruses are known to be harmful and heterogeneous viruses, able to infect a large number of hosts. Among them, SADS-CoV (Swine Acute Diarrhea Syndrome Coronavirus), also known as PEAV (Porcine Enteric Alphacoronavirus), or SeA-CoV (Swine Enteric Alphacoronavirus), is the most recent Alphacoronavirus discovered, and caused several outbreaks reported in Chinese swine herds between late 2016 and 2019. We performed an upgraded phylodinamic reconstruction of SADS-CoV based on all whole genomes available on 21 June 2021. Results showed a very close relationship between SADS-CoV and HKU2-like CoV, which may represent the evolutionary intermediate step towards the present SADS-CoV. The direct progenitor of SADS-CoV is so far unknown and, although it is well known that horseshoe bats are reservoirs for Rhinolophus bat coronavirus HKU2-like (HKU2-like CoVs), the transmission path from bats to pigs is still unclear. The discrepancies in the phylogenetic position of rodent CoV, when different molecular markers were considered, corroborate the recombination hypothesis, suggesting that wild rats, which are frequent in farms, may have played a key role. The failure of the attempt at molecular dating, due to the lack of a clock signal, also corroborates the occurrence of a recombination event hypothesis. Zoonotic infections originating in wildlife can easily become a significant threat for human health. In such a context, due to the high recombination and cross-species capabilities of Coronavirus, SADS-CoV represents a possible high-risk pathogen for humans which needs a constant molecular monitoring.