The index herd with PMWS in Sweden: Presence of serum amyloid A,circovirus 2 viral load and antibody levels in healthy and PMWS-affected pigs

Background

Postweaning Multisystemic Wasting Syndrome (PMWS) is an emerging disease in pigs of multifactorial origin, but associated to porcine circovirus type 2 (PCV2) infection. PMWS was first diagnosed in Sweden at a progeny test station that received pigs aged five weeks from 19 different nucleus herds on the day after weaning. The objective of this study was to examine, for the first time in an index outbreak of PMWS, the relationship between PCV2 virus, antibodies to PCV2 and serum amyloid a (SAA) in sequentially collected serum samples from pigs with and without signs of PMWS.

Methods

Forty pigs of the last batch that entered the station at a mean age of 37.5 days were monitored for signs of PMWS during the first 55 days after arrival. Serum was collected on six occasions and analysed for presence of PCV2 DNA and antibodies to PCV2, as well as for levels of SAA.

Results

Four of the pigs (10%) were concluded to have developed PMWS, with necropsy confirmation in three of them. These pigs displayed low levels of maternal antibodies to PCV2, more than 10⁷ PCV2 viral DNA copies per ml serum and failed to mount a serological response to the virus. Starting between day 23 and 34 after arrival, an increase in PCV2 viral load was seen in all pigs, but PCV2 did not induce any SAA-response. Pigs that remained healthy seroconverted to PCV2 as the viral load was increased, regardless of initially having low or high levels of PCV2-antibodies.

Conclusion

In this index case of PMWS in Sweden, pigs affected by PMWS were not able to mount a relevant serum antibody response which contributed to the disease progression. The maximal PCV2 virus load was significantly higher and was also detected at an earlier stage in PMWS-affected pigs than in healthy pigs. However, a viral load above 10⁷ PCV2 DNA copies per ml serum was also recorded in 18 out of 34 pigs without any clinical signs of PMWS, suggesting that these pigs were able to initiate a protective immune response to PCV2.     

Comparative serologic and virologic study of commercial swine herds with and without postweaning multisystemic wasting syndrome

A comparative serologic and virologic study was performed in pigs from 5 herds with postweaning multisystemic wasting syndrome (PMWS) and 2 herds without PMWS in Quebec. In each herd, 60 blood samples were collected at 4-wk intervals from pigs from 3 to 23 wk of age. The serum was evaluated for the presence of antibodies to porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), as well as for the presence of nucleic acid of PCV2, PRRSV, and porcine parvovirus (PPV), by means of the polymerase chain reaction (PCR). Serologic profiles for PCV2 were very similar in 6 of the 7 herds, including the 2 without PMWS, and were characterized by a gradual decrease in antibody titres from 3 until 11 wk of age, followed by seroconversion at 15 wk, and high PCV2 antibody titres thereafter in all pigs. Only starting at 11 to 15 wk of age could PCV2 viremia be detected, except in 1 herd, in which clinical signs were observed at 6 to 7 wk of age. A PCV2 viremia could be detected within the same pigs for a minimum of 8 wk, and the virus could still be detected in 41% of the serum samples obtained at 23 wk of age. The antibody level did not appear to influence the occurrence of disease, since titres were similar in pigs in the herds with or without PMWS. Infection with PRRSV, as demonstrated by PCR and seroconversion, preceded that of PCV2 by at least 1 mo in both types of herd. Both PRRSV and PCV2 were detected in some pigs in 5 of the 7 herds, including 1 herd without PMWS. Porcine parvovirus could be detected in serum by PCR in 2 herds with PMWS after the onset of clinical signs and also in 1 herd without PMWS. Genomic analysis of PCV2 strains identified in the herds without PMWS indicated complete or very high homology (99.4% to 100%) with the PCV2 strains identified in 4 herds with PMWS. In our field study, the triggering of PMWS in the herds could not be linked to coinfection with either PRRSV or PPV or to the use of a specific immunostimulant, such as vaccines, or to particular genomic differences between the PCV2 strains identified.     

Efficacy of single dose of an inactivated porcine circovirus type 2 (PCV2) whole-virus vaccine with oil adjuvant in piglets

Background

Post-weaning multisystemic wasting syndrome (PMWS) associated with PCV2 is one of the most costly diseases currently faced by the swine industry. The development of effective vaccines against PCV2 infection has been accepted as an important strategy in the prophylaxis of PMWS.

Methods

In the present study, a PK-15 cell-adapted formalin-inactivated prototype vaccine candidate was prepared using a strain of PCV2 from China. Inactivation of the virus was accomplished using a standard formalin inactivation protocol. The protective properties of the inactivated PCV2 vaccine were evaluated in piglets. Ten 28-day-old pigs were randomly assigned to two groups, each with five. Group 1 was vaccinated intramuscularly with the inactivated virus preparation; Group 2 received sterile PBS as a placebo. By 28 days post-vaccination (DPV), Groups 1 and 2 were challenged intranasally and intramuscularly with 5 × 10⁷ TCID₅₀ of a virulent PCV2 isolate.

Results

The vaccinated pigs seroconverted to PCV2 and had high levels of serum antibodies to PCV2 at 28 days after vaccination, whereas the control pigs remained seronegative. No significant signs of clinical disease were recorded following the challenge with PCV2, but moderate amounts of PCV2 antigen were detected in most lymphoid organs of the control pigs. PCV2 was detected in two out of the five vaccinated pigs. Furthermore, pathological lesions and viremia were milder in the vaccinated group.

Conclusions

The obtained results indicate that the inactivated PCV2 virus vaccine with an oil adjuvant induce an immunological response in pigs that appears to provide protection from infection with PCV2. The vaccine, therefore, may have the potential to serve as a vaccine aimed to protect pigs from developing PMWS.     

The presence of co-infections in pigs with clinical signs of PMWS in The Netherlands: a case-control study

In this study, 60 pigs with clinical signs of post-weaning multisystemic wasting syndrome (PMWS) from 20 different pig herds and 180 control pigs (without clinical signs of PMWS) were examined to get more insights into the frequencies of porcine circovirus 2 infections and the presence of co-infections in pigs with and without clinical signs of PMWS in the Netherlands. Porcine circovirus type 2 was detected in 100% of the pigs with clinical signs of PMWS by virus isolation and/or PCR and in 50% of the pigs from PMWS-free herds. There was an association between the levels of infectious PCV2 and/or PCV2 DNA load and the severity of clinical signs as described for PMWS. A high variation in PCV2 antibody titres was found in the clinically affected pigs, and 27% of these pigs did not mount PCV2 antibody titres higher than 1:200. A concurrent infection of PCV2 and porcine reproductive and respiratory syndrome virus (PRRSV) was found in at least 83% of the pigs with clinical signs of PMWS and in 35% of the pigs from PMWS-free herds. Co-infections of European- and American-type PRRSV were detected only in PMWS herds and in one control herd with a history of PMWS clinical signs.     

Reproduction of postweaning multisystemic wasting syndrome in pigs experimentally inoculated with a Swedish porcine circovirus 2 isolate.

In recent years, porcine circovirus type 2 (PCV2)-associated postweaning multisystemic wasting syndrome (PMWS) has been reported worldwide. However, to date, PMWS has not been reported in Sweden despite the demonstration of serum antibodies to a PCV2-like virus in Swedish pigs. This communication reports the experimental reproduction of clinical PMWS after inoculation of colostrum-deprived (CD) pigs, derived from a Northern Ireland herd, with an isolate of PCV2 virus recovered from a clinically normal Swedish pig that was necropsied in 1993. The clinical disease and histological lesions observed in CD pigs inoculated with this virus were indistinguishable from those observed in previous studies on CD pigs inoculated with a PCV2 virus isolate recovered from pigs with PMWS. These results highlight the disease potential of PCV2 isolated from regions apparently free of PMWS and suggest that the status of the host and its environment is an important factor in the development of clinical PMWS.     

Profiles of seroconversion to porcine circovirus type 2 in herds affected and not affected by postweaning multisystemic wasting syndrome

The aim of the present study was to explore the usefulness of serological methods in the diagnosis of postweaning multisystemic wasting syndrome (PMWS). The study was carried out in 4 PMWS-affected and 6 control farms. Based on the serological profiles, infection with porcine circovirus type 2 (PCV2) was determined to take place at 3-7 weeks of age in the PMWS-affected and at 3-11 weeks of age in the control farms. To compare the dynamics of seroconversion to PCV2 among farms, cross-sectional serological profiles were normalised in relation to the inferred age of infection. The results indicated that the proportion of seropositive pigs increased significantly slower in the affected herds. The most pronounced difference was observed about 4 weeks after infection, when the proportion of seropositive pigs ranged from 0 to 53.3% and from 70 to 100% in PMWS-affected and control herds, respectively. Mean antibody titres at that age were also significantly lower in the affected farms. These observations suggest a delay in the production of PCV2-specific antibodies and indicate that serological methods may be helpful in identifying herds with a high risk of PMWS.     

Transmission of different variants of PCV2 and viral dynamics in a research facility with pigs mingled from PMWS-affected herds and non-affected herds

Post-weaning Multisystemic Wasting Syndrome (PMWS) has been identified in most swine-producing countries worldwide. The disease has resulted in significant health challenges and economic damage to the swine industry. The aim of this study was to determine horizontal transmission of porcine circovirus type 2 (PCV2) and to examine viral dynamics in pigs in a controlled PMWS transmission study. In the study pigs from PMWS-affected herds and non-affected herds were permitted to have close contact (same pen), nose-to-nose contact (to pigs in neighbouring pens) or no physical contact (pen across the aisle and pens in other compartments). By DNA sequence analysis, eight variants of genotype PCV-2b were identified in the research facility. From the spread of these PCV2-variants it was concluded that PCV2 primarily infects through close contact and nose-to-nose contact. PCV2 genome sequences were obtained from selected pigs at arrival to the research facility and again when the same pigs developed PMWS. This analysis showed that pigs from PMWS-affected herds developed PMWS caused by the same variant of PCV2 as they carried when entering the research facility. In contrast, pigs from non-affected herds developed PMWS with PCV2-variants identified in pigs from PMWS-affected herds. This was probably connected to at least 10³ higher mean serum-titer of PCV2 in pigs from PMWS-affected herds as compared to pigs from non-affected herds at the beginning of the transmission study. The study further showed that pigs able to control the PCV2 infection, as measured by the PCV2-titer in serum, recovered clinically (pigs from PMWS-affected herds) or stayed healthy (pigs from non-affected herds). Like this, pigs with a PCV2 titer below 5 × 10⁸ copies/ml serum during the study period had a chance of recover from the PCV2 infection whereas pigs with PCV2 titers above 5 × 10⁸ copies/ml serum at any time point generally died from PMWS.     

Detection of neutralizing antibodies in postweaning multisystemic wasting syndrome (PMWS)-affected and non-PMWS-affected pigs

The notion that postweaning multisystemic wasting syndrome (PMWS)-affected pigs develop an impaired humoral response against porcine circovirus type 2 (PCV2) has been reported in several studies. However, little information is available regarding the presence of neutralizing antibodies (NA) in PCV2-infected pigs and their role in the pathogenesis of the disease. The aim of the present work was to further characterize the humoral response, and in particular the production of NA, in pigs with different PCV2-infection status. Seventy-two conventional pigs from different farms were classified into three groups based on PCV2 infection and clinico-pathological status, namely: PCV2-negative, non-PMWS PCV2-positive and PMWS-affected animals. In addition, 9-week old pigs from an experimental infection (6 controls and 14 PCV2-inoculated pigs) were also studied. NA and total PCV2 antibodies (TA) as well as viral load in serum were determined and correlated with the clinico-pathological status of pigs. Results indicated that PMWS-affected pigs had lower NA titres, if any, than healthy animals. NA titres were also inversely correlated with PCV2 load in serum. NA and TA titres were positively correlated; however, correlation differed among infection status, being lower in PCV2-positive pigs. Also, the diagnostic performance of each test was evaluated, indicating that the combination of viral neutralization and quantitative PCR in serum was useful to discard PMWS (specificity 92%). In experimentally infected animals, the evolution of NA paralleled the course TA, although a slight delay in NA production was seen in some animals. The increase of NA coincided with the drop in viral load. Results from this work further support that PMWS-affected pigs show an impaired humoral immune response and, particularly, an inefficient NA response against PCV2.     

Postweaning multisystemic wasting syndrome (PMWS) in Sweden from an exotic to an endemic disease

Postweaning multisystemic wasting syndrome (PMWS) is causally associated with porcine circovirus type 2 (PCV2) infection of pigs. PCV2 was first demonstrated in Swedish pigs in 1993, although the virus was almost certainly present in pigs in the country before that. Despite this, no signs of PMWS were observed in pigs of Sweden until the first outbreak was reported in 2003. The accumulated number of PMWS-affected herds have increased via 16 (2004) and 41 (2005) to 123 in December 2006. Of these herds, 30 (25%) have now been declared free from PMWS. However, a number of other herds have had individual pigs that have fulfilled the demands for PMWS at necropsy and 52 of these herds have been declared negative on herd basis after treatment for intestinal or respiratory diseases, and/or by correcting shortcomings in management of the herd including feed. Thus, individual cases of the disease have been observed in around 200 herds by the end of 2006 and PMWS is now regarded as an endemic disease in Sweden. The pig population of Sweden is geographically isolated, the density of pigs and the pathogen load in the country is low and the use of growth promoters (low dose antibiotics in feed) was prohibited in 1986. Additionally, the trade of animals in Sweden is organised in a restricted way. Because of these factors it is possible to conduct meaningful real-time studies on the transformation of PMWS in Sweden from being an exotic to an endemic disease in a three year time scale. Initially the PMWS cases were concentrated in the southern part of Sweden, but have gradually spread north. The PMWS-positive herds have, in general, had an effective production, but some management errors have constantly been observed in affected herds. Physical links between affected herds are often missing, and the data generated to date on the PMWS outbreaks in Sweden do not suggest an introduction of a new contagious microbe into the country that is responsible for the PMWS outbreaks, nor does PMWS appear to be spread via semen. In Sweden, intensity in rearing, disease preventing measures and immaturity of the piglets appear to be important as predisposing factors to PMWS and, as such, are discussed in this article.     

Dynamics of porcine circovirus type 2 infection in a herd of pigs with postweaning multisystemic wasting syndrome

OBJECTIVE: To determine the pattern of infection for porcine circovirus type 2 (PCV2) in a herd of pigs with postweaning multisystemic wasting syndrome (PMWS). ANIMALS: 29 sows and 250 pigs. PROCEDURE: Blood samples were collected from all 3-, 7-, and 12-week old pigs and 59 pigs at 28 weeks of age. Pigs that died during the study were necropsied. Porcine parvovirus and PCV2 antibodies were assayed. A polymerase chain reaction (PCR) was used to detect PCV2 genome in serum of selected pigs. RESULTS: The PMWS started when pigs were 8 weeks old, with a prevalence of 30% in 8- to 10-week-old pigs. Eighty-three pigs died during the period between 3 and 12 weeks of age. Microscopic lesions consistent with PMWS were observed, and PCV2 nucleic acid was detected (50 of 68 pigs). Antibodies to PCV2 decreased from 3 to 7 weeks of age, increased at 12 weeks of age, and were maintained until 28 weeks of age. One sow had a positive result for PCR of serum. Nine, 37 and 8 pigs had PCV2 genome in serum obtained at 7, 12, and 28 weeks of age, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Infection with PCV2 coincided with severe clinical signs; however, infected 28-week-old pigs did not have evidence of disease. Immunity declined over time in young pigs. A long duration of PCV2 viremia was apparent in a high percentage of infected pigs, which may affect transmission and persistence of the virus in a herd.     

Seroprevalence of Toxoplasma gondii infection in Norwegian dairy goats

Background

Toxoplasma gondii is a major problem for the sheep industry as it may cause reproduction problems. The importance of T. gondii in Norwegian goat herds is uncertain, but outbreaks of toxoplasmosis in dairy goat farms have been recorded. The aim of this study was to describe the prevalence of T. gondii infection in Norwegian dairy goats by using serology.

Findings

Goat serum originally collected as part of two nationwide surveillance and control programmes between 2002 and 2008 were examined for T. gondii antibodies by using direct agglutination test. In total, 55 of 73 herds (75%) had one or more serologically positive animals, while 377 of 2188 (17%) of the individual samples tested positive for T. gondii antibodies.

Conclusions

This is the first prevalence study of T. gondii infection in Norwegian goats. The results show that Norwegian goat herds are commonly exposed to T. gondii. Nevertheless, the majority of goat herds have a low prevalence of antibody positive animals, which make them vulnerable to infections with T. gondii during the gestation period.     

Experimental reproduction of postweaning multisystemic wasting syndrome (PMWS) in pigs in Sweden and Denmark with a Swedish isolate of porcine circovirus type 2

An experimental model using 3-day-old snatch-farrowed colostrum-deprived piglets co-infected with porcine circovirus type 2 (PCV2) and porcine parvovirus (PPV) is at present one of the best methods to study factors affecting development of postweaning multisystemic wasting syndrome (PMWS). A Swedish isolate of PCV2 (S-PCV2) retrieved in 1993 from a healthy pig has been used in this model to reproduce PMWS in pigs from Northern Ireland. This virus has been present in the Swedish pig population for at least a decade without causing any known PMWS disease problems, despite its potential pathogenicity. The reasons for this are unknown, but could be related to genetics, absence of triggers for PCV2 upregulation (infectious agent and/or management forms) within Swedish pig husbandry. In order to confirm the pathogenicity of S-PCV2, Swedish and Danish pigs were experimentally infected with this isolate according to the established model. Swedish pigs were also infected with a reference isolate of PCV2 (PCV2-1010) to compare the severity of disease caused by the two isolates in Swedish pigs. Both Danish and Swedish pigs developed PMWS after the experimental infection with S-PCV2. Antibodies to PCV2 developed later and reached lower levels in serum from pigs infected with S-PCV2 than in pigs inoculated with PCV2-1010. In general, pigs infected with S-PCV2 showed more severe clinical signs of disease than pigs infected with PCV2-1010, but pigs from all PCV2-inoculated groups displayed gross and histological lesions consistent with PMWS. All pigs inoculated with PPV, alone or in combination with PCV2, displayed interleukin-10 responses in serum while only pigs infected with PPV in combination with PCV2 showed interferon-alpha in serum on repeated occasions. Thus, the pathogenicity of S-PCV2 was confirmed and a role for cytokines in the etiology of PMWS was indicated.     

Use of a polymerase chain reaction assay and an ELISA to monitor porcine circovirus type 2 infection in pigs from farms with and without postweaning multisystemic wasting syndrome

OBJECTIVE: To determine whether correlations exist between viremia with porcine circovirus type 2 (PCV2) and serum antibody profiles and between detection of PCV2 in nasal cavities and viremia of pigs from farms with and without postweaning multisystemic wasting syndrome (PMWS). ANIMALS: 495 pigs, ranging from the late nursery stage to the early grower-finisher stage of production. PROCEDURE: Serum antibodies to PCV2 were studied with an ELISA that detects the ORF2 viral protein. Nasal swab specimens and serum samples were tested with a PCV2-specific PCR assay. RESULTS: PCV2 DNA and serum antibodies to PCV2 were detected in pigs from all farms, although in different proportions. Overall, PCV2 DNA was detected in greater percentages in serum samples and nasal swab specimens of pigs from farms with PMWS. Although viral DNA was detected in both serum samples and nasal swab specimens, PCV2 detection in nasal swab specimens was higher than in serum samples of pigs from all farms. Serum antibodies to PCV2 were detected in a greater percentage of pigs from farms with PMWS, compared with farms without PMWS. CONCLUSIONS AND CLINICAL RELEVANCE: A high prevalence of PCV2 infection was found in pigs from farms with and without PMWS. Besides the presence of PCV2, unknown additional factors may be necessary to induce the full expression of PMWS.     

The relationship between antibody status to bovine corona virus and bovine respiratory syncytial virus and disease incidence,reproduction and herd characteristics in dairy herds

Background

Bovine respiratory syncytial virus (BRSV) and bovine corona virus (BCV) affects cattle worldwide. Our objective was to evaluate the effects of these infections on general health and reproduction parameters measurable on herd level and to explore the association between antibody status and some herd characteristics.

Methods

We collected a pooled milk sample from five primiparous cows from 79 Swedish dairy herds in September 2006. The samples were analysed for immunoglobulin G antibodies to BCV and BRSV with indirect enzyme-linked immunosorbent assays. Herd level data from 1 September 2005 to 30 August 2006 were accessed retrospectively. The location of the herds was mapped using a geographical information system.

Results

Ten herds were antibody negative to both viruses and were compared with 69 herds positive to BCV or BRSV or both. Positive herds had a higher (P = 0.001) bulk tank milk somatic cell count (BMSCC) compared with negative herds. The medians for all other analyzed health and reproductive parameters were consistently in favour of the herds negative to both viruses although the differences were not statistically significant. A higher proportion (P = 0.01) of herds used professional technicians for artificial insemination, rather than farm personnel, amongst the 33 herds negative to BCV compared with the 46 positive herds.

Conclusions

Our result shows that herds that were antibody positive to BCV and/or BRSV had a higher BMSCC compared with herds negative to BCV and BRSV. There was also tendency that negative herds had a better general herd health compared with positive. A higher proportion amongst the BCV negative herds used external technicians for AI instead of farm personnel, indicating that it is possible to avoid infection although having regular visits. Negative herds were located in close proximity to positive herds, indicating that local spread and airborne transmission between herds might not be of great importance and that herds can stay free from these infection transmission although virus is circulating in the area.     

Factors affecting costs for on-farm control of salmonella in Swedish dairy herds

Background

The Swedish control program for salmonella includes restrictions and on-farm control measures when salmonella is detected in a herd. Required control measures are subsidised by the government. This provides an opportunity to study costs for on-farm salmonella control. The aim of this study was to describe the costs for on-farm salmonella control in Swedish cattle herds and to investigate the effects of herd factors on these costs in dairy herds.

Results

During the 15 years studied there had been a total of 124 restriction periods in 118 cattle herds; 89 dairy herds, 28 specialised fattening herds and three suckler herds. The average costs per herd for on-farm salmonella control was 4.60 million SEK with a median of 1.06 million SEK corresponding to approximately 490 000 and 110 000 EUR. The range was 0.01 to 41 million SEK corresponding to 1080 EUR to 4.44 million EUR per farm. The costs cover measures required in herd-specific control plans, generally measures improving herd hygiene. A mixed linear model was used to investigate associations between herd factors and costs for on-farm salmonella control in dairy herds. Herd size and length of the restriction period were both significantly associated with costs for on-farm control of salmonella with larger herds and longer periods of restrictions leading to higher costs. Serotype detected and administrative changes in the Swedish Board of Agriculture aiming at reducing costs were not associated with costs for on-farm salmonella control.

Conclusions

On-farm control of salmonella in Swedish cattle herds incurred high costs but the costs also varied largely between herds. Larger herds and longer restriction periods increased the costs for on-farm control of salmonella in Swedish dairy herds. This causes concern for future costs for the Swedish salmonella control program as herd sizes are increasing.     

Housing system and herd size interactions in Norwegian dairy herds; associations with performance and disease incidence

Background

According to the Norwegian animal welfare regulations, it has been forbidden to build new tie-stall barns since the end of 2004. Previous studies have shown that cow performance and health differ between housing systems. The interaction between housing system and herd size with respect to performance and disease incidence has not been evaluated.

Methods

Cow performance and health in 620 herds housed in free-stall barns were compared with in 192 herds housed in tie-stall barns based on a mail survey and data from the Norwegian Dairy Herd Recording and Cattle Health Systems. The housing systems herds were comparable with respect to herd size (15-55 cows). Associations between performance/disease incidence and housing system, herd size and year of building the cow barn were tested in general linear models, and values for fixed herd size of 20 and 50 cows were calculated. On the individual cow level mixed models were run to test the effect of among others housing system and herd size on test-day milk yield, and to evaluate lactation curves in different parities. All cows were of the Norwegian Red Breed.

Results

Average milk production per cow-year was 134 kg lower in free-stall herd than in tie-stall herds, but in the range 27-45 cows there was no significant difference in yields between the herd categories. In herds with less than 27 cows there were increasingly lower yields in free-stalls, particularly in first parity, whereas the yields were increasingly higher in free-stalls with more than 45 cows.In free-stalls fertility was better, calving interval shorter, and the incidence rate of teat injuries, ketosis, indigestions, anoestrus and cystic ovaries was lower than in tie-stalls. All of these factors were more favourable in estimated 50-cow herds as compared to 20-cow herds. In the larger herd category, bulk milk somatic cell counts were higher, and the incidence rate of mastitis (all cases) and all diseases was lower.

Conclusion

This study has shown that there is an interaction between housing system and herd size, and that performance and health is not universally better in small free-stalls than in tie-stalls.     

Genomic analysis of PCV2 isolates from Danish archives and a current PMWS case-control study supports a shift in genotypes with time

Porcine circovirus type 2 (PCV2) is the primary cause of Postweaning Multisystemic Wasting Syndrome (PMWS) in pigs. PCV2, however, is found in both PMWS-affected herds and non-affected herds. The objective of this study was to clarify if PCV2 genome nucleotide sequences isolated from pigs from PMWS-affected herds and non-affected herds cluster phylogenetically in two separate groups. All isolates (45) belonged to PCV2 group 1 and shared a nucleotide sequence identity of 99.4-100% indicating a very homogeneous PCV2 population in Denmark. Phylogenetic analysis of the PCV2 isolates revealed no distinctive clustering of case- and control-herds suggesting that there is no link between PCV2 sequences and herd disease status. The appearance of only PCV2 group 1 isolates in this study (isolates from 2003/2004) led us to determine if PCV2 nucleotide sequences had changed in Denmark over time. Interestingly, all PCV2 isolates from before the first outbreak of PMWS (2001) belonged either to a new PCV2 group identified for the first time in this study and named group 3 (isolates from 1980, 1987 and 1990) or PCV2 group 2 (isolates from 1993 and 1996). The shift from PCV2 group 2 to 1 was confirmed on a more global scale by placing all full genome PCV2 sequences submitted to GenBank from 1997 to 2006 in either of the groups by phylogenetic analysis. The analysis showed that the shift happened in 2003 or even earlier. This may indicate that PCV2 group 1 is a more adapted form of PCV2 and possibly could be more pathogenic.     

Reproductive Performance,Udder Health,and Antibiotic Resistance in Mastitis Bacteria isolated from Norwegian Red cows in Conventional and Organic Farming

Background

The objectives of this study were to investigate whether there were differences between Norwegian Red cows in conventional and organic farming with respect to reproductive performance, udder health, and antibiotic resistance in udder pathogens.

Methods

Twenty-five conventional and 24 organic herds from south-east and middle Norway participated in the study. Herds were matched such that geographical location, herd size, and barn types were similar across the cohorts. All organic herds were certified as organic between 1997 and 2003. All herds were members of the Norwegian Dairy Herd Recording System. The herds were visited once during the study. The relationship between the outcomes and explanatory variables were assessed using mixed linear models.

Results

There were less > 2nd parity cows in conventional farming. The conventional cows had higher milk yields and received more concentrates than organic cows. Although after adjustment for milk yield and parity, somatic cell count was lower in organic cows than conventional cows. There was a higher proportion of quarters that were dried off at the herd visit in organic herds. No differences in the interval to first AI, interval to last AI or calving interval was revealed between organic and conventional cows. There was no difference between conventional and organic cows in quarter samples positive for mastitis bacteria from the herd visit. Milk yield and parity were associated with the likelihood of at least one quarter positive for mastitis bacteria. There was few S. aureus isolates resistance to penicillin in both management systems. Penicillin resistance against Coagulase negative staphylococci isolated from subclinically infected quarters was 48.5% in conventional herds and 46.5% in organic herds.

Conclusion

There were no large differences between reproductive performance and udder health between conventional and organic farming for Norwegian Red cows.     

吉林部分地区TTSuVs与PCV2混合感染情况调查及其与PMWS相关性分析

为了解吉林地区猪细环病毒(TTSuVs)与II型猪圆环病毒(PCV2)混合感染情况,分析TTSuVs感染与仔猪多系统衰竭征(PMWS)的相关性。试验通过PCR技术对2019年收集到的吉林部分地区的10家规模化猪场130份血清样本进行检测;并应用本实验已建立的PCV2、TTSuVs实时荧光定量PCR检测方法,对PCV2阳性样品进行病毒载量的分析,区分PMWS病猪与PCV2亚临床感染猪,比较PMWS病猪与PCV2亚临床感染猪中TTSuVs的载量。结果显示:TTSuV1感染率为38.46%;TTSuV2感染率为57.69%;PCV2感染率为46.15%;TTSuV1与TTSuV2的混合感染率为31.54%;TTSuV1与PCV2的混合感染率为32.30%;TTSuV2与PCV2的混合感染率为44.62%;三种病毒的混合感染率为22.30%。且PMWS病猪血清中TTSuV2载量明显高于PCV2亚临床感染猪(P<0.01)。结果表明,TTSuV2载量与PMWS病的发生存在一定程度的相关性。