VIROLOGIE

PMWS-CIRCOVIRUS-PDNS
• Characteristics of porcine circovirus-2 replication in lymphoid organs of pigs inoculated in late gestation or postnatally and possible relation to clinical and pathological outcome of infection
• Systemic cytokine profile in feeder pigs suffering from natural postweaning multisystemic wasting syndrome (PMWS) as determined by semiquantitative RT-PCR and flow cytometric intracellular cytokine detection
• Identification of postweaning multisystemic wasting syndrome in European wild boar (Sus scrofa)
• Epidemiological study on porcine circovirus type 2 (PCV2) infection in the European wild boar (Sus Scrofa)
• Interlaboratory testing of porcine sera for antibodies to porcine circovirus type 2
• A chimeric porcine circovirus (PCV) with the immunogenic capsid gene of the pathogenic PCV type 2 (PCV2) cloned into the genomic backbone of the nonpathogenic PCV1 induces protective immunity against PCV2 infection in pigs
• Characterization of porcine circovirus type 2 in Taiwan
• Haptoglobin and pig-major acute protein are increased in pigs with postweaning multisystemic wasting syndrome (PMWS)
PRRS
• Effects of porcine reproductive and respiratory syndrome vaccination in breeding-age animals

Characteristics of porcine circovirus-2 replication in lymphoid organs of pigs inoculated in late gestation or postnatally and possible relation to clinical and pathological outcome of infection
SANCHEZ RE, MEERTS P, NAUWYNCK HJ, ELLIS JA, PENSAERT MB
J Vet Diagn Invest, 16, 2004, 175-185
Both late-term fetuses in utero and one-day-old cesarean derived piglets were inoculated with PCV2 in an attempt to reproduce PMWS and PMWS-like lesions. Piglets were either euthanized immediately at harvest or sacrificed sequentially and monitored for clinical signs. In each case, blood and tissue samples from lymphoid organs were collected and virus isolation and titration were performed in order to correlate the level of virus replication with clinical signs, histological lesions and serological response. PCV2 infected cells were identified by double-immunofluorescence labeling using several specific cell markers. Clinical signs were not observed in any of the piglets suggesting that high levels of PCV2 replication and severe lymphoid lesions are not necessarily associated with wasting disease which is in disagreement with some previous studies. Cells of the monocyte-macrophage lineage were confirmed the main target cells of PCV2. However, infected cells carrying lymphocyte-related markers were also detected in a few pigs without it being possible to state for sure that these cells were lymphocytes. Six out of the 26 piglets included in this study had high virus titers (104.5-5.7 TCID50/g) with infiltrating monocytic cells, and to a lesser extent cells carrying lymphocyte-related markers, as the main infected cell populations while in pigs with lower virus titers (less than 104.5 TCID50/g) cells of the monocyte-macrophage lineage were those primarily infected.

Systemic cytokine profile in feeder pigs suffering from natural postweaning multisystemic wasting syndrome (PMWS) as determined by semiquantitative RT-PCR and flow cytometric intracellular cytokine detection
SIPOS W, DUVIGNEAU JC, WILLHEIM M, SCHILCHER F, HARTL RT, HOFBAUER G, EXEL B, PIETSCHMANN P, SCHMOLL F
Veterinary Immunology and Immunopathology, 97, 2004, 25-37
http://www.sciencedirect.com
Keywords: porcine circovirus type 2 (PCV2), postweaning multisystemic syndrome (PMWS) intracellular cytokine detection, flow cytometry, RT-PCR, swine.
The blood cell and cytokine profile of 14-week-old PMWS-naturally-affected pigs was compared to that of clinically healthy pen-mates. In PMWS-affected pigs, total leukocytes and platelets were increased whereas lymphocytes were only slightly decreased but this could be ascribed to the fact that the animals being 14-week-old were then coming out of the clinical stage of the disease (4-14 weeks of age). At the transcriptional level, an increase in IL-1a and IL-10 mRNA was observed in PMWS-affected pigs but the difference was not significant when compared to reference pigs, whereas IL-2 and IL-2Ra mRNA was found notably decreased even if the results of flow cytometry revealed a significant increase of IL-2 at the protein level and thus an increased capacity of the remaining lymphocytes to produce IL-2 upon in vitro stimulation. No difference was observed between diseased and healthy animals for IL-12 and TNF-a and only a slight increase in IFN-? was detected in the diseased pigs. As a virus-induced disease, PMWS should lead to a cellular immune response characterized either by a Th1 driven cytokine response pattern or a cytokine pattern indicative of T cell immunosuppression. The results of this study contrast with this hypothesis.

Identification of postweaning multisystemic wasting syndrome in European wild boar (Sus scrofa)
SCHULZE C, SEGALES J, NEUMANN G, HLINAK A, CALSAMIGLIA M, DOMINGO M
Veterinary Record, 2004, Volume 154, N°22, 694-696
A 10-month-old wild boar was found dead in a rural area in Germany. Post-mortem examination revealed wasting and gross lesions indicative of bacterial septicemia that was further confirmed by the identification of Salmonella cholerasuis. In addition, histological lesions together with a wide range of serological and molecular tests demonstrated the presence of PCV2 infection. The sequencing of the resulting isolate showed a very high homology with other PCV2 isolates obtained from German domestic pigs. It is interesting to notice that this animal was much older than PMWS-affected domestic pigs suggesting that, following PCV2-infection, others factor such as concurrent infections be necessary for the development of the disease. In that case systemic salmonellosis could have been the triggering factor. This paper is the first report of PMWS in a free-living European wild boar.

Epidemiological study on porcine circovirus type 2 (PCV2) infection in the European wild boar (Sus Scrofa)
VICENTE J, SEGALES J, HÖFLE U, BALASCH M, PLANA-DURAN J, DOMINGO M, GORTAZAR C,
Veterinary Research, 35, 2004, 243-253
Keywords: European wild boar, porcine circovirus type 2, epidemiology, postweaning multisystemic wasting syndrome.
A nationwide serological survey was conducted in Peninsular Spain in 656 wild boars from 45 geographical sites over a 3-year period from 2000 to 2003. These wild boars were coming from open areas, fenced areas or fenced areas with translocations and artificial feeding. The analysis of the samples by immunoperoxydase monolayer assay (IPMA) revealed that the prevalence of medium to high titers of antibodies to PCV2 was 47.9 ± 1.9% which demonstrates the endemic status of PCV2 in the Spanish wild boar population. As expected, the more intensively managed wild boars had the highest prevalence of antibodies to PCV2 with piglets showing very high levels of seropositivity which confirms the role played by management in the spread of PVC2. In addition, the presence of PCV2 nucleic acid and PMWS lesions was investigated in tissue samples from 55 healthy wild boars and one diseased wild boar by in situ hybridization and histopathology respectively. PCV2 nucleic acid was detected in two of the healthy animals as well as in the 6-month-old pig showing wasting and diagnosed with PMWS which represents the first report of a PMWS case in a wild boar in Spain.

Interlaboratory testing of porcine sera for antibodies to porcine circovirus type 2
MCNAIR I, MARSHALL M, MCNEILLY F, BOTNER A, LADEKJAER-MIKKELSEN AS, VINCENT I, HERRMANN B, SANCHEZ R, RHODES C
J Vet Diagn Invest, 16, 2004, 164-166
Various types of assays and fixatives are currently available for the detection and the titration of PCV2 antibodies in swine sera. Five laboratories across Europe and Canada were given the same panel of 20 swine sera and requested to carry out their routine assays. The analysis of the results revealed that immunoperoxydase monolayer assay (IPMA) provided higher titers than did indirect immunofluorescence assay (IFA) and that paraformaldehyde provided higher titers than did acetone or ethyl alcohol. These variations clearly demonstrates that the investigation of PCV2 calls for standardized procedures.

A chimeric porcine circovirus (PCV) with the immunogenic capsid gene of the pathogenic PCV type 2 (PCV2) cloned into the genomic backbone of the nonpathogenic PCV1 induces protective immunity against PCV2 infection in pigs
FENAUX M, OPRIESSNIG T, HALBUR PG, ELVINGER F, MENG XJ
Journal of Virology, 2004, Vol. 78, N°12, 6297-6303
In a previous paper, Fenaux et al. reported that they had designed an immunogenic, attenuated chimeric PCV1-2. This follow-up study consisted in inoculating 3 groups of 12 SPF piglets either by intramuscular injection with 200 µg of the chimeric PCV1-2 DNA clone (group 1), by intralymphoid injection with 200 µg of the chimeric PCV1-2 DNA clone (group 2) or by intramuscular injection with 103.5 TCID50 of the chimeric PCV1-2 live virus (group 3), a fourth group of 12 pigs being kept as control. At 42 days post-inoculation all pigs were challenged intranasally and intramuscularly with 2x104.5 TCID50 of a wild-type PCV2. The results of this study showed that protective immunity to wild-type PCV2 was achieved in SPF pigs using attenuated chimeric PCV1-2 live virus or DNA clone inoculated intramuscularly (group 1 and 3).

Characterization of porcine circovirus type 2 in Taiwan
WANG C, HUANG TS, HUANG CC, TU C, JONG MH, LIN SY, LAI SS
Journal of Veterinary Medical Science, 2004, Volume 66, N°5, 469-475
http://www.jstage.jst.go.jp/article/jvms/66/5/469/_pdf
Routine PCR for PCV2 detection was applied to tissue samples collected from 623 Taiwanese diseased pigs over a 2-year period (2000-2002). The clinical conditions of the diseased pigs included PMWS, abortion, nervous disorders, sudden death, PDNS and non-specific clinical signs. PCV2 was detected in 49.6% of the cases. PCV2 infection may thus be present in pigs showing a large variety of clinical signs. A total of 8 PCV2 isolates were sequenced (4 from PMWS-affected pigs, 2 from PDNS-affected pigs, 1 from a pig with nervous disorders, 1 from a case of abortion) and were shown to share 95-99% homology. A further comparison of these isolates with 6 other isolates from the USA, Canada, Spain, Germany, Korea and Japan, revealed that all shared 92-99% homology. The phylogenetic analysis of the 8 Taiwanese isolates together with 32 PCV2 isolates from various parts of the world allowed to classify them into one large group containing two minor subgroups, the Taiwanese isolates being present in both subgroups. In addition, a large-scale serological survey revealed that about 83.5% of the Taiwanese pig population was seropositive to PCV2 suggesting that PCV2 infection is widely present in Taiwanese pig herds.

Haptoglobin and pig-major acute protein are increased in pigs with postweaning multisystemic wasting syndrome (PMWS)
SEGALES J, PINEIRO C, LAMPREAVE F, NOFRARIAS M, MATEU E, CALSAMIGLIA M, ANDRES M, MORALES J, PINEIRO M, DOMINGO M
Veterinary Research, 2004, Volume 35, N°3, 275-282
Keywords: porcine circovirus type 2, postweaning multisystemic wasting syndrome, acute phase proteins, haptoglobin, pig major phase protein.
The impact of PCV2-infection and PMWS on the acute phase protein (APP) profile was studied through the determination of serum concentration level of two major porcine APP, namely haptoglobin (HPT) and pig major phase protein (pig-MAP), by radial immunodiffusion, in conventional pigs originating from PMWS-affected herds with minimal pathogen microbism. A significant increase in APP was observed in PMWS-affected pigs, but not in pigs with subclinical PCV2 infection, when compared to healthy age-matched pigs suggesting that the level of such APP could be a useful tool to establish the health status of PCV2-infected pigs.

Effects of porcine reproductive and respiratory syndrome vaccination in breeding-age animals
DEWEY CE, WILSON S, BUCK P, LEYENAAR JK
Preventive Veterinary Medicine, 62, 2004, 299-307
Keywords: porcine reproductive and respiratory syndrome (PRRS), reproductive performance, vaccine.
The reproductive performance of 52 pig herds from Canada (Ontario and Manitoba) and the USA (Midwest) vaccinated with PRRS modified live vaccine (RespPRRS, Boehringer Ingelheim Ltd) were investigated. None of these herds had 100% of their sow population vaccinated against PRRSV. Herds with more than 50% of vaccinated sows were classified as “majority-vaccinated” herds while the others were classified as “low-vaccinated” herds. The vaccination of sows during gestation is to be avoided since a negative impact was observed in both “low-vaccinated” and “majority-vaccinated” herds with a lower number of pigs born alive and weaned in sows vaccinated during gestation when compared to sows that farrowed prior to the use of the vaccine.