Association of Myroides odoratimimus in immunocompromized piglets with post weaning multisystemic wasting syndrome.

AIM: To study the association of opportunistic infection due to Myroides odoratimimus in piglets immunocompromised by porcine circovirus type 2 (PCV2) infection. METHODS AND RESULTS: The clinical samples (n = 101) were analysed bacteriologically. The isolates were identified by their phenotypes and MALDI TOF-MS analysis as Myroides species. The phylogram constructed based on nucleotide sequences of the 16S rRNA gene showed identity (~99%) with the M. odoratimimus isolates. The minimum inhibitory concentration values for antibiotics revealed M. odoratimimus to be resistant against carbapenem, cephalosporins, aminoglycosides and fluoroquinolones. The presence of PCV2 in affected tissue samples was confirmed by amplification of the 565 bp region of ORF2 of the PCV2 genome. The topology of the phylogenetic tree grouped the PCV2 with cluster-2d. CONCLUSIONS: PCV2 being immunosuppressive in nature might have impaired the immunity thereby increasing the susceptibility of immunocompromised piglets to opportunistic pathogens such as M. odoratimimus leading to disease severity and high mortality. The M. odoratimimus isolates were found to be multidrug resistant and evidenced for uncertain clinical relevance and hence could act as hidden source of public health hazard. SIGNIFICANCE AND IMPACT OF THE STUDY: Myroides odoratimimus is a rarely reported human pathogen. We reported the incidence of infection due to seemingly rare isolates of M. odoratimimus causing an outbreak of pneumonia in piglets. This appears, to the best of authors' knowledge, to be the first outbreak due to Myroides recorded in animal clinical cases described in the literature.

Coinfection with Haemophilus parasuis serovar 4 increases the virulence of porcine circovirus type 2 in piglets.

BACKGROUND: Postweaning multisystemic wasting syndrome (PMWS) is an emerging disease in swine. Pigs with PMWS are often infected with a variety of other pathogens, including bacteria, viruses and mycoplasm, in addition to porcine circovirus type 2 (PCV2). PCV2 and Haemophilus parasuis serovar 4 (HPS4) coinfection remain epidemic in China. METHODS: Here we report construction of a three-week-old naturally farrowed, colostrum-deprived (NFCD) piglet's infection model and demonstrate that PCV2-infected piglets with the HPS4 coinfection increased the virulence of PCV2 and these pathogens interact acquired PMWS. RESULTS: All the single infected piglets were transiently bacteremic or viremic. All the PCV2/HPS4 coinfected piglets developed PMWS, characterized by dyspnea, anorexia, prostration and lose weight severely. Co-infection with PCV2 and HPS4 resulted in an increased amount of virus in serum and tissues, presented a slower generation and lower levels of antibodies against PCV2. Co-infection with PCV2 and HPS4 resulted in further reductions in total and differential peripheral blood leukocyte counts. Meantime, PCV2/ HPS4 coinfection potentiated the severity of lung and lymphoid lesions by PCV2-associated, increased the virulence of PCV2-antigen and enhanced the incidence of PMWS in piglets. CONCLUSION: Co-infection with PCV2 and HPS4 induce the exacerbation of system injuries and enhance the pathogenicity of PCV2 in piglets.

Cost of post-weaning multi-systemic wasting syndrome and porcine circovirus type-2 subclinical infection in England - an economic disease model.

Post-weaning multi-systemic wasting syndrome (PMWS) is a multi-factorial disease with major economic implications for the pig industry worldwide. The present study aimed to assess the economic impact of PMWS and porcine circovirus type 2 (PCV2) subclinical infections (PCV2SI) for farrow-to-finish farms and to estimate the resulting cost to the English pig industry. A disease model was built to simulate the varying proportions of pigs in a batch that get infected with PCV2 and develop either PMWS, subclinical disease (reduce growth without evident clinical signs) or remain healthy (normal growth and no clinical signs), depending on the farm level PMWS severity. This PMWS severity measure accounted for the level of post-weaning mortality, PMWS morbidity and proportion of PCV2 infected pigs observed on farms. The model generated six outcomes: infected pigs with PMWS that die (PMWS-D); infected pigs with PMWS that recover (PMWS-R); subclinical pigs that die (Sub-D); subclinical pigs that reach slaughter age (Sub-S); healthy pigs sold (H-S); and pigs, infected or non-infected by PCV2, that die due to non-PCV2 related causes (nonPCV2-D). Enterprise and partial budget analyses were used to assess the deficit/profits and the extra costs/extra benefits of a change in disease status, respectively. Results from the economic analysis at pig level were combined with the disease model's estimates of the proportion of different pigs produced at different severity scores to assess the cost of PMWS and subclinical disease at farm level, and these were then extrapolated to estimate costs at national level. The net profit for a H-S pig was £19.2. The mean loss for a PMWS-D pig was £84.1 (90% CI: 79.6-89.1), £24.5 (90% CI: 15.1-35.4) for a PMWS-R pig, £82.3 (90% CI: 78.1-87.5) for a Sub-D pig, and £8.1 (90% CI: 2.18-15.1) for a Sub-S pig. At farm level, the greatest proportion of negative economic impact was attributed to PCV2 subclinical pigs. The economic impact for the English pig industry for the year 2008, prior to the introduction of PCV2 vaccines, was estimated at £52.6 million per year (90% CI: 34.7-72.0), and approximately £88 million per year during the epidemic period. This was the first study to use empirical data to model the cost of PMWS/PCV2SI at different farm severity levels. Results from this model will be used to assess the efficiency of different control measures and to provide a decision support tool to farmers and policy makers.

Economic efficiency analysis of different strategies to control post-weaning multi-systemic wasting syndrome and porcine circovirus type 2 subclinical infection in 3-weekly batch system farms.

The study assessed the economic efficiency of different strategies for the control of post-weaning multi-systemic wasting syndrome (PMWS) and porcine circovirus type 2 subclinical infection (PCV2SI), which have a major economic impact on the pig farming industry worldwide. The control strategies investigated consisted on the combination of up to 5 different control measures. The control measures considered were: (1) PCV2 vaccination of piglets (vac); (2) ensuring age adjusted diet for growers (diets); (3) reduction of stocking density (stock); (4) improvement of biosecurity measures (bios); and (5) total depopulation and repopulation of the farm for the elimination of other major pathogens (DPRP). A model was developed to simulate 5 years production of a pig farm with a 3-weekly batch system and with 100 sows. A PMWS/PCV2SI disease and economic model, based on PMWS severity scores, was linked to the production model in order to assess disease losses. This PMWS severity scores depends on the combination post-weaning mortality, PMWS morbidity in younger pigs and proportion of PCV2 infected pigs observed on farms. The economic analysis investigated eleven different farm scenarios, depending on the number of risk factors present before the intervention. For each strategy, an investment appraisal assessed the extra costs and benefits of reducing a given PMWS severity score to the average score of a slightly affected farm. The net present value obtained for each strategy was then multiplied by the corresponding probability of success to obtain an expected value. A stochastic simulation was performed to account for uncertainty and variability. For moderately affected farms PCV2 vaccination alone was the most cost-efficient strategy, but for highly affected farms it was either PCV2 vaccination alone or in combination with biosecurity measures, with the marginal profitability between 'vac' and 'vac+bios' being small. Other strategies such as 'diets', 'vac+diets' and 'bios+diets' were frequently identified as the second or third best strategy. The mean expected values of the best strategy for a moderately and a highly affected farm were £14,739 and £57,648 after 5 years, respectively. This is the first study to compare economic efficiency of control strategies for PMWS and PCV2SI. The results demonstrate the economic value of PCV2 vaccination, and highlight that on highly affected farms biosecurity measures are required to achieve optimal profitability. The model developed has potential as a farm-level decision support tool for the control of this economically important syndrome.

Infectious risk factors for individual postweaning multisystemic wasting syndrome (PMWS) development in pigs from affected farms in Spain and Denmark.

Two prospective longitudinal studies in 13 postweaning multisystemic wasting syndrome (PMWS)-affected farms from Spain (n=3) and Denmark (n=10) were performed. Blood samples from pigs were longitudinally collected from 1st week until the occurrence of the PMWS outbreak. Wasted and healthy age-matched pigs were euthanized, necropsied and histopathologically characterised. PMWS diagnosis was confirmed by means of lymphoid lesions and detection of porcine circovirus type 2 (PCV2) in these tissues by in situ hybridization or immunohistochemistry. Serological analyses were performed in longitudinally collected serum samples to detect antibodies against, PCV2, porcine reproductive and respiratory syndrome virus (PRRSV), porcine parvovirus (PPV), swine influenza virus (SIV) and Lawsonia intracellularis (law), Mycoplasma hyopneumoniae, Aujeszky's disease virus (ADV) and Salmonella spp. A Cox proportional hazards model was used to investigate the simultaneous effects of seroconversion and maternal immunity against the studied pathogens. Results showed that high levels of maternal immunity against PCV2 had a protecting effect in farms from both countries. Moreover, for the Danish dataset, seroconversion against law had an overall protecting effect, but for animals with very low levels of maternal antibody levels against this pathogen, the effect appeared neutral or aggravating. Otherwise, for the Spanish dataset, maternal immunity against PPV and PRRSV gave protective and aggravating effects, respectively. In conclusion, the present study reflects the complex interaction among different pathogens and their effects in order to trigger PMWS in PCV2 infected pigs.

Gastric zygomycosis in a pig affected with postweaning multisystemic wasting syndrome--case report.

A postweaning pig died in spite of antibiotic therapy showing wasting in a small herd. Postweaning multisystemic wasting syndrome (PMWS) was diagnosed on the basis of gross pathological and histological lesions and the presence of moderate amounts of porcine circovirus 2 (PCV2) antigen in tissue samples. Mycotic gastritis caused by Zygomycetes spp. was found on round areas with a diameter of 1 to 3 cm in the glandular mucosa of the stomach. Moderate amount of PCV2 viral antigen was detected almost evenly in the stomach and mostly in the macrophages. In addition, acute uraemia, revealed by an ammonia-like stink of the gastric mucosa and the presence of acute erosions on the glandular mucosa of the stomach, was observed as a consequence of PCV2-induced interstitial nephritis. Only PCV2 infection could be identified as a cause of secondary mycotic gastritis. The results further support the immunosuppressive ability of PCV2 infection in PMWS-affected pigs.

[Detection of Mycoplasma suis in clinical cases with postweaning multisystemic wasting syndrome in swine]. / Detección de Mycoplasma suis en casos clínicos de síndrome del desmedro multisistémico posdestete en porcinos.

Mycoplasma suis is a swine erythrocyte obligatory parasite. Its presence may result in chronic or acute anaemia in different pig categories. It is considered that the postweaning multisystemic wasting syndrome (PMWS) is caused by porcine circovirus type 2, but some aspects of the pathogenesis remain unknown. PMWS signs are impaired weight gain, anaemia and jaundice in 5 to 12 week-old pigs that suffer from immunosuppression and bacterial co-infections. The pigs with signs of these diseases on three porcine farms were studied. Compatible M. suis forms in blood smears and typical PMWS lesions in tissue cuts were seen. This is the first communication of the clinical association between these two entities.