Spatial and temporal patterns of pig herds diagnosed with Postweaning Multisystemic Wasting Syndrome (PMWS) during the first two years of its occurrence in Denmark

The clinical syndrome Postweaning Multisystemic Wasting Syndrome (PMWS) in pigs has emerged globally during the last decade. In October 2001, the first pig herd diagnosed with PMWS was reported in Denmark, and since then the number of herds diagnosed with PMWS has increased markedly. The etiology of PMWS is not well understood, but increased knowledge of the causal factors is prerequisite for applying preventive interventions. In this study we described the temporal (time of diagnosis), spatial (location of herds) and spatio-temporal pattern of Danish pig herds diagnosed with PMWS during the first two years after the first herd was diagnosed, and we tested for spatial and spatio-temporal clustering using scan statistics. The study population consisted of pig herds that during the study period (October 2001-September 2003) performed diagnostic submissions to the two major veterinary diagnostic laboratories in Denmark (6724 herds). Of these, 277 herds were diagnosed with PMWS. Two statistically significant spatial clusters of herds diagnosed with PMWS were identified. These clusters included 11% and 8% of the study herds, respectively. Within these two clusters the relative risk for a herd to be diagnosed with PMWS was twice as high as expected. One statistically significant spatio-temporal cluster was identified between February and May 2002. We discuss different hypotheses that could explain why pig herds diagnosed with PMWS were clustered both spatially and spatio-temporally, and conclude that the results support the hypothesis that PMWS is caused by introduction of a new, unidentified, pathogen into the Danish pig production.     

免疫刺激商品断奶仔猪复制多系统衰竭综合征(PMWS)

猪圆环病毒2型（PCV2）是引起PMWS的必需病原,与其他病原混合感染或受到外界刺激时表现PMWS临床症状。本试验将16头商品化断奶仔猪（32日龄）随机分为4组（每组4头）,即对照组、钥匙孔血蓝蛋白刺激组、PCV2攻毒组和PCV2攻毒后钥匙孔血蓝蛋白刺激组,用上海某猪场分离株PCV2-SH、钥匙孔血蓝蛋白（KLH）反复刺激断奶仔猪以复制PMWS。其中对照组、钥匙孔血蓝蛋白刺激组未出现症状;PCV2攻毒组症状较轻,出现增重缓慢,伴有短暂的体温升高;而PCV2攻毒后钥匙孔血蓝蛋白刺激组出现明显的临床症状,2头猪在攻毒后第11天濒临死亡,其中1头在第12天死亡,攻毒猪宰杀后脏器出现明显的病理变化。PCV2攻毒组和PCV2攻毒后钥匙孔血蓝蛋白刺激组于攻毒后第4天出现病毒血症,宰杀后肺脏、淋巴结均检测到PCV2的DNA。以上结果说明,PCV2-SH感染结合免疫刺激可以引起商品化仔猪发生PMWS,为PCV2致病机理和免疫学研究提供了动物发病模型。     

断奶后多系统衰竭综合征病猪中存在沙门氏菌和猪繁殖与呼吸系统综合征病毒共感染

调查了曾经暴发沙门氏菌病的四个猪场的14头病猪,发现在这些猪的肿胀淋巴结中出现带有淋巴细胞排空的肉芽肿性炎症。应用免疫标记和PCR方法在病变部位检测到猪圆环病毒2(PCV2)抗原和PCV2DNA。此外,在这些病猪的肺脏中检测出猪繁殖与呼吸综合征病毒(PRRSV),分离到猪霍乱沙门氏菌。在9头沙门氏菌感染猪中,有5头为沙门氏菌、PMWS与PRRSV并发感染,其数量(55.6%)远远高于沙门氏菌与PMWS感染猪(22.2%)或沙门氏菌与PRRSV感染猪(22.2%)。     

Individual risk factors for Post-weaning Multisystemic Wasting Syndrome (PMWS) in pigs: A hierarchical Bayesian survival analysis

Risk factors for Post-weaning Multisystemic Wasting Syndrome (PMWS) at the pig level were identified using data from a longitudinal study in seven PMWS-affected farms in France. In each farm, a representative sample of 120 pigs (180 in one farm) was randomly selected after farrowing and followed from birth to slaughter. Individual information included serological status for Porcine Circovirus type 2 (PCV-2), Porcine Reproductive and Respiratory Syndrome (PRRS) virus, and Porcine Parvovirus (PPV), individual weight, rearing conditions, and clinical observations recorded at 7, 13, 16 and 21 weeks of age and at slaughter. Two different Bayesian frailty models were used to identify variables related to time-to-PMWS: (i) a logistic-survival model and (ii) an accelerated failure time model (different survival time distributions) both with two levels of clustering (litter and farm). Similar results in terms of variables related to time-to-PMWS were obtained with both models. However, information provided by the different approaches were complementary. Piglets were more likely to exhibit PMWS after early infection by PCV-2 (i.e. before 7 weeks old) and if they were weaned early (before 21 days). Piglets born to PCV-2 seronegative sows and/or to sows with neck injuries due to poorly performed injections were also more at risk. With the accelerated failure time model, time ratios were obtained giving an estimation of the expected survival time (increased or decreased) after exposure to the factor. The logistic-survival model showed that the majority of the risk factors were mostly related to the odds of PMWS whereas the PCV-2 passive immunity derived from the dam also tended to postpone PMWS appearance later.     

华东地区PMWS患病猪群PCV-2的检测及其基因特征

用 PCR方法 ,对江苏、上海、山东、江西、安徽和浙江等省市 6 5家猪场 99例断奶仔猪多系统衰弱综合征(PMWS)肺脏和淋巴结病料 ,进行了猪圆环病毒 - 2 (PCV- 2 )基因检测 ,发现其中 18家猪场 2 1例病料为 PCV- 2阳性。源自安徽和上海的 PCV- 2分离株经基因序列分析显示 ,2个分离株部分 ORF2 与国外分离毒株同源性为 92 %～99%。安徽分离株 AHHF6与韩国分离株 KSY- 1同源性为 99% ,而上海分离株 SHHT1与加拿大分离株 Imp.114 7同源性为 98%。上述结果表明 ,我国 PMWS患病猪群广泛存在 PCV- 2 ,不同地区 PCV- 2存在一定基因差异 ,它们可能来源于不同国家或地区     

Effect of the Pietrain breed used as terminal boar on Post-weaning Multisystemic Wasting Syndrome (PMWS) in the offspring in four PMWS-affected farms

The aim of this study was to determine the potential risk factors for PMWS at the individual pig level and assess the effect of the Pietrain paternal genetic background of the animals in a cohort study. The survey was set up in four PMWS-affected farms with 2 repetitions (batches) per farm. A representative sample of 60 pigs per batch, stratified according to the paternal genetic background (Pietrain: yes vs. no), was randomly selected after farrowing. The representative cohort was divided into 8 batches and the pigs were individually monitored from birth to slaughter. Survival analysis was used to determine the factors related to the time to PMWS. The litter-cluster effect was taken into account using the marginal Cox model (robust estimation of the covariance matrix) and the gamma shared frailty model which were compared.No protective effect of the Pietrain breed on the time to PMWS and the proportion of affected pigs in the offspring was found in this study. Piglets showing low circovirus type 2 (PCV2) titres at 7 weeks-old with no subsequent seroconversion and piglets from PCV2 negative sows were most likely to be affected by PMWS (HR=7.0 and 2.8, respectively). Active infection of the pregnant dams with parvovirus was related to an increased risk of PMWS in the offspring (HR=2.3). Neck injuries due to poorly performed injections in the dams were associated with an increased risk of PMWS with the marginal model (HR=2.1). Oxytocin injection (dams) during farrowing was protective against PMWS in the offspring (HR=0.6).     

上海PMWS并发PRRS自然病例的病理组织学观察

对上海5例5～13周龄断奶仔猪多器官衰竭综合征（PMWS）并发猪繁殖与呼吸综合征（PRRS）自然病例进行了病理组织学观察。结果：5例病猪均出现坏死性淋巴结炎、间质性肺炎以及不同程度的坏死性脾炎、间质性肾炎和肝炎。2例病猪出现心肌炎，表现为心肌纤维断裂、溶解和心肌间质中淋巴细胞局灶性浸润。2例病猪出现脑炎，在大脑白质区出现神经胶质细胞结节。     

An outbreak of blue-eared pig disease (porcine reproductive and respiratory syndrome) in four pig herds in Great Britain.

The clinical syndrome of a new disease of pigs in four herds in the Humberside area is described. The first signs of the disease were anorexia, lethargy and pyrexia with up to 60 per cent of the dry sows affected. These signs were followed by an increased incidence of abortions which occurred in up to 3.3 per cent of sows, premature farrowings in up to 20.6 per cent of sows and stillbirths and late mummification which affected up to 26.0 and 18.8 per cent of fetuses, respectively. Mortality in neonatal and pre-weaning pigs reached up to 88 per cent and respiratory disease of high morbidity and low mortality occurred in fattening pigs. There were infertility problems in sows, with an increase in returns to service and a failure to show oestrus after weaning or aborting. The signs of the disease in boars were anorexia and malaise. Cyanosis of the extremities affected up to 2 per cent of the animals. The outbreak lasted 11 weeks in all the herds.     

Postweaning multisystemic wasting syndrome (PMWS) in pigs in Croatia: detection and characterisation of porcine circovirus type 2 (PCV2)

The objective of this study was to characterise porcine circovirus type 2 (PCV2) from pigs with naturally occurring postweaning multisystemic wasting syndrome (PMWS) in Croatia, and to determine the epizootiological, clinical and pathomorphological features of the disease. During a systematic health monitoring programme conducted in the period from January 2002 to June 2003, PMWS was suspected on eight different pig-producing farms in Croatia. The diagnosis of PMWS met all three key criteria: the presence of compatible clinical signs, the presence of the characteristic microscopic lymphoid lesions, and the detection of PCV2 within the lesions by polymerase chain reaction (PCR) and by in situ hybridisation (ISH). Moreover, PCV2 DNA from swine tissues was extracted and sequenced. The phylogenetic analysis of 4 Croatian PCV2 strains showed close relationship to PCV2 strains isolated in Slovenia, France, the Netherlands, the United Kingdom, China and Hungary. PCV2 was also demonstrated by electron microscopy in the lymph node of an affected animal. This is the first demonstration of PMWS in Croatia based on all scientifically accepted diagnostic criteria.     

Herd prevalence of Salmonella spp. in Danish pig herds after implementation of the Danish Salmonella Control Program with reference to a pre-implementation study

The problems addressed are: (1) comparison of prevalences of Salmonella spp. in different herd types in the Danish pig population after implementation of the Danish Salmonella Control Program (DSCP), and (2) to make a reference to a study from 1993/1994 (pre-implementation) with a discussion of possible biases when diagnostic methods differ slightly. The objectives were to present the prevalences of Salmonella spp., Salmonella Typhimurium, and multiresistant S. Typhimurium DT104 in Danish pig herds in 1998. Further, to discuss how herd prevalences may be compared to a previous study.A bacteriological study in 1998 comprised: (a) a random sample of slaughter pig producing herds (N=1962); (b) a random sample of farrow-to-grower (sow) herds (N=305); and (c) all breeding and multiplying (genetic) herds (N=366). A previous bacteriological study on Salmonella presence in 1993/1994 served as a model for the present study. The results of the study were that multiresistant S. Typhimurium DT104 was detected in one herd producing slaughter pigs. The herd apparent prevalences (HAPs) of Salmonella spp. were 11.7, 16.7 and 11.4% in genetic, sow, and slaughter pig herds, respectively. The conclusion of the study was that prevalence of multiresistant S. Typhimurium DT104 was low in the examined slaughter pig herds. The herd true prevalence (HTP) of Salmonella spp. in pigs had declined from before the start of the DSCP in 1993/1994 to 4 years later (1998).     

Immunohistochemical characterisation of the lymph node reaction in pig post-weaning multisystemic wasting syndrome (PMWS)

The goal of this study was to identify a strain of feline immunodeficiency virus (FIV) that would be more virulent for adult cats than the prototype FIV-APetaluma and, thereby, enhance the FIV infection model for HIV-1 related research. Diehl et al. reported that one clade C strain of FIV, FIV-CPGammar, was more virulent than other known FIV isolates. Mortalities from 58 to 100% were reported for kittens 12 weeks of age and less following intravenous inoculation. A more variable and somewhat less virulent disease course was observed in neonatal to 8-10-week-old kittens infected orally, intravaginally or intrarectally with this same isolate (Obert and Hoover, 2000). However, no studies have been done with FIV-CPGammar in adult cats. Therefore, the virulence of FIV-CPGammar for young adult cats was compared to that of FIV-APetalulma, the original FIV isolate. One group of five cats were inoculated intraperitoneally with 470 TCID(50) of FIV-CPGammar in the form of pooled plasma from acutely infected cats, while a second group was infected with plasma containing the 750 TCID50 of FIV-APetaluma. The cats were observed for 20 weeks for gross signs of disease, hematologic abnormalities, time of antibody appearance, and plasma and peripheral blood mononuclear cell (PBMC) associated virus levels. Viral RNA and proviral DNA were measured by a real-time PCR, sensitive to 50 copies per milliliter. The only outward sign of disease was lymphadenopathy, which occurred at a similar time and intensity in both groups of cats. Cats infected with FIV-CPGammar were more likely to be neutropenic and lymphopenic during the first 10-12 weeks of infection than cats infected with FIV-APetaluma. Both groups of cats showed similar overall declines in absolute mean CD4 cell counts and identical concomitant increases in CD8 cells. CD4/CD8 cell ratios were also similar. Antibody, as measured by an ELISA against recombinant FIV-TM antigen, appeared in all cats by 4 weeks post-infection. The most significant differences were in plasma viral RNA and PBMC proviral DNA levels. Cats infected with FIV-CPGammar had up to 100 times higher mean levels of viral RNA during the first few weeks of infection than cats infected with FIV-APetaluma. This difference was also mirrored in levels of proviral DNA in PBMC, which were significantly higher in the FIV-CPGammar infected cats. Plasma viral RNA and PBMC proviral DNA levels were virtually identical in both groups of cats at 20 weeks post-infection. However, proviral DNA in tissues such as thymus and popliteal lymph nodes was 10-fold or so higher in FIV-CPGammar infected cats at 20 weeks and histopathologic lesions were more severe. Based on these various parameters, we concluded that FIV-CPGammar was more virulent than FIV-APetaluma in young adult cats during the 20-week study period. However, we were not able to recreate the severe and rapidly progressive disease previously reported for kittens, suggesting an age-related resistance similar to that observed previously for FIV-APetaluma (George et al., 1993).     

Postweaning multisystemic wasting syndrome (PMWS) in pigs with particular emphasis on the causative agent, the mode of transmission, the diagnostic tools and the control measures. A review

Postweaning multisystemic wasting syndrome (PMWS) is a worldwide emerging disease of weaned piglets. The objective of this review is to summarize the current knowledge regarding PMWS, its causative agent, mode of transmission, diagnostic techniques to detect PCV-2, the possible control measures, and the association of PMWS and PCV-2 with porcine dermatitis and nephropathy syndrome (PDNS). The causative agent of PMWS is porcine circovirus type 2 (PCV-2), however, not all pigs infected with PCV-2 develop the syndrome. PCV-2 is consistently associated with PMWS and PMWS is considered not to occur without it. Both the syndrome and the virus are not regarded as new. Co-factors that could activate PCV-2 to cause PMWS are considered. This enigmatic nature of both the syndrome and the virus is triggering a concern towards uncertainties of the viral transmission, its introduction in to the herd, effective tools of diagnosis, and control strategies.     

Geographical association between the genotype of bovine tuberculosis in found dead badgers and in cattle herds

In a survey, 457 badgers that had been found dead in Wales were postmortem-examined, and samples were examined by histology and by extended culture (for up to 12 weeks). Mycobacterium bovis was cultured from 55 badgers (12.0 per cent), and the histology typical of M bovis infection was seen in a further six (1.3 per cent). The prevalence in badgers in each of 10 geographical areas varied between 0 and 26 per cent (P<0.001), and was associated with the incidence of confirmed M bovis infection in cattle herds in the same areas (P<0.01). In northern Wales, bTB was rare in both hosts. An infected badger was 12.3 times more likely to be within 5 km of a confirmed cattle bTB breakdown than an uninfected badger. The M bovis isolates from badgers belonged to one of four genotypes defined by spoligotype and variable number tandem repeat type. These genotypes were also found in 290 concurrent confirmed herd breakdowns, and tended to be similar to the genotypes in badgers in the same geographical areas. When badgers and cattle no more than 30 km apart were compared, the genotype diversity was greater in cattle than in badgers (P=0.016), suggesting that the movement of cattle plays a greater part in the spatial distribution of M bovis than the movement of badgers.     

Relationship of the prevalence of swine helminths to management practices and anthelmintic treatment in Danish sow herds

During 1982-1984, the occurrence of helminths in 66 sow herds in Denmark was examined by means of faecal samples. The correlations between the prevalences of Ascaris suum and Oesophagostomum spp. and management practices were analysed for fatteners and sows, respectively, resulting in four multivariate models. The helminth prevalences were in general low in large herds, specific pathogen-free (SPF) herds and herds with low weaning age. The multivariate analyses showed that only the two latter correlations were significant. The helminth prevalences of the fatteners were not correlated with anthelmintic treatment. In the sows, anthelmintic treatment was significantly correlated with low prevalences of both helminths, despite samples from recently dewormed sows indicating a rather transitory effect. The prevalences of Oesophagostomum in both fatteners and sows were significantly higher on solid floors with straw bedding than on slatted floors without straw, while this was not the case for Ascaris. Tethering of sows was not significantly correlated with helminth prevalences. Daily cleaning was significantly correlated with low helminth prevalences in fatteners, but not in the sows, while disinfection of the pens was only significantly correlated with low prevalences of Oesophagostomum in fatteners. No correlations to washing of the pens were found. The epidemiology of Ascaris and Oesophagostomum is discussed, especially why the latter is the most sensitive to intensive management.     

Overview of issues pertaining to the manufacture, distribution, and use of antimicrobials in animals and other information relevant to animal antimicrobial use data collection in the United States

This paper provides condensed literature review and contextual information concerning antimicrobial use in animals and antimicrobial use data collection techniques. Information is summarized into the following topics: (I) antimicrobial use for animal growth promotion; (II) regulatory framework for approval of veterinary antimicrobials and feed additives in the United States; (III) animal health product manufacturing and distribution networks; (IV) existing estimates of animal antimicrobial use in the United States; (V) additional sources for animal use data in the United States; (VI) recommendations from international expert groups; (VII) animal antimicrobial use surveillance systems in other nations and (VIII) human use data collection systems in the United States.