Classical Swine fever
• Adsorption of colostral antibodies against classical swine fever, persistence of maternal antibodies, and effect on response to vaccination in baby pigs.
• An experimental infection with classical swine fever virus in pregnant sows: transmission of the virus, course of the disease, antibody response and effect on gestation.

PRRS
• Effect of concurrent infections on persistence of shedding of porcine reproductive and respiratory syndrome virus and transmissible gastroenteritis virus.
• An attempt to eradicate porcine reproductive and respiratory syndrome virus (PRRSV) after an outbreak in a breeding herd : eradication strategy and persistence of antibody titers in sows.
• Genetic interaction between porcine reproductive and respiratory syndrome virus (PRRSV) strains in cell culture and in animals.
• High frequency RNA recombination in porcine reproductive and respiratory syndrome virus occurs preferentially between parental sequences with high similarity.
• Transmission of porcine reproductive and respiratory syndrome virus from persistently infected sows to contact controls.
• Genetic variability of European porcine reproductive and respiratory syndrome virus (PRRSV) isolates by RT-PCR and restriction fragment length polymorphism of ORF5 gene.
• PRRS: vaccination with a killed vaccine; field experience.
• Porcine reproductive and respiratory syndrome: an update, with regard to vaccination.
• Experimental inoculation of late term pregnant sows with a field isolate of porcine reproductive and respiratory syndrome vaccine-derived virus.
• Shedding of porcine reproductive and respiratory syndrome virus in mammary gland secretions of sows.
• A comparison of virus isolation, immunohistochemistry, fetal serology, and reverse-transcription polymerase chain reaction assay for the identification of porcine reproductive and respiratory syndrome virus transplacental infection in the fetus.

PMWS and PCV2 diseases
• Susceptibility of porcine circovirus type 2 to commercial and laboratory disinfectants.
• Neonatal vaccination for Mycoplasma hyopneumoniae and post-weaning multisystemic wasting syndrome: a field trial.
• An experimental model for post-weaning multisystemic wasting syndrome (PMWS) in growing piglets.
• Kinetics of porcine circovirus type 2 replication.
• The effects of immuno-modulation on the clinical and pathological expression of postweaning multisystemic wasting syndrome.
• Cloned genomic DNA of type 2 porcine circovirus is infectious when injected directly into the liver and lymph nodes of pigs: characterization of clinical disease, virus distribution, and pathologic lesions.

Adsorption of colostral antibodies against classical swine fever, persistence of maternal antibodies, and effect on response to vaccination in baby pigs.
VANDEPUTTE J, TOO HL, NG FK, CHEN C, CHAI KK, LIAO GA.
Amer J Vet Res 2001 62 : 1805-1811
This trial demonstrates the ability of Pestiffa® (MERIAL, Lyon, France) to provide effective protection against a virulent Asiatic strain of CSF virus in neonates vaccinated before the uptake of colostrum. Vaccination was also proved effective in 7-week-old pigs.

An experimental infection with classical swine fever virus in pregnant sows: transmission of the virus, course of the disease, antibody response and effect on gestation.
DEWULF J, LAEVENS H, KOENEN F, MINTIENS K, DE KRUIF A
J Vet Med B 2001 48 : 583-591
In sow herds, establishment of CSF infection by clinical observation was found to be less appropriate a method than in fattening herds, the time between the onset of clinical signs and the actual report of the disease being longer for the former. In this study, 12 conventional gilts were experimentally infected with classical swine fever virus. Following infection, clinical signs were atypical and discrete, suggesting that diagnostic tests such as leukocyte count associated with PCR should be considered as a suitable method when atypical clinical signs are observed in diseased sows.

Effect of concurrent infections on persistence of shedding of porcine reproductive and respiratory syndrome virus and transmissible gastroenteritis virus.
MENGELING WL, WESLEY RD, LAGER KM, VORWALD AC, CLOUSER DF
Journal of Swine Health and Production Vol.10, number 2 : 67-73
Clinical signs, shedding and persistence of either virus were not potentiated by concurrent infection. In order to reduce contact transmission, it is suggested to isolate TGEV-infected pigs for 2 weeks and PRRSV-infected pigs for 8 weeks.

An attempt to eradicate porcine reproductive and respiratory syndrome virus (PRRSV) after an outbreak in a breeding herd : eradication strategy and persistence of antibody titers in sows.
Journal of Swine Health and Production Vol.10,number 1 : 23-25
DESROSIERS R, BOUTIN M
The outbreak of porcine reproductive and respiratory syndrome (PRRS) occurred in a sow herd of high health status. The strategy consisted in exposing all animals to the PRRS field virus by mixing animals showing clinical signs with healthy animals, by introducing minced tissues of piglets that died from PRRS in feed, and by placing dead piglets in the farrowing pens, in the hope of making all animals immune to the virus and putting an end to virus shedding. This strategy of deliberate infection associated to temporary herd closure gave promising results but further data are necessary in order to valid the protocol.

Genetic interaction between porcine reproductive and respiratory syndrome virus (PRRSV) strains in cell culture and in animals.
Journal of Swine Health and Production Vol.10,number 1 : 15-21
MURTAUGH MP, YUAN S, NELSON EA, FAABERG KS
The fact that recombinant virus could originate from mixed attenuated vaccine viruses as a consequence of genetic rearrangements has been studied in cell culture and animals. Recombination between vaccine strains occurred in cultured cells but the resulting viruses did not persist. No recombination was observed in animals in this experiment.

High frequency RNA recombination in porcine reproductive and respiratory syndrome virus occurs preferentially between parental sequences with high similarity.
VAN VUGT JJFA, STORGAARD T, OLEKSIEWICZ MB, BØTNER A
J Gen Virol 2001 82 : 2615-2620
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The study consisted in inoculating cultured cells either with two European isolates or an European isolate and a North American isolate. While recombination between European strains of PRRSV occurred, no recombination between the European and the North American isolates was observed. Thus the probability of recombination between the European and the North American types appears very low.

Transmission of porcine reproductive and respiratory syndrome virus from persistently infected sows to contact controls.
BIERK MD, DEE SA, ROSSOW KD, OTAKE S, COLLINS JE, MOLITOR TW
Can Vet J 2001 65 : 261-266
A model was established demonstrating the ability of PRRSV to persist in non-pregnant sows as well as its ability to be transmitted from persistently infected to naïve contact sows.

Genetic variability of European porcine reproductive and respiratory syndrome virus (PRRSV) isolates by RT-PCR and restriction fragment length polymorphism of ORF5 gene.
BOUVET J, CHARREYRE C, LAMBERT V, AEBERLE C, BROCARD P, BOEUF L, CHAPPUIS G
Eleven European strains of PRRSV were submitted to RT-PCR and RFLP and compared to two reference strains namely Lelystad virus and US VR2332 in order to assess their genetic variability. Nucleotide sequence identity between European strains and Lelystad strain and European strains and the US strain respectively ranged from 87.9 to 99.8% and from 31.3 to 62.5%. As for the amino acid sequence, European strains shared 87.6-100% identity with Lelystad strain and 52.4-54% with the US strain.

PRRS: vaccination with a killed vaccine; field experience.
JOISEL F, REYNAUD G, CHARREYRE C, HERIN JB
Pig Journal 2001 48 : 120-137
The effects of porcine reproductive and respiratory syndrome (PRRS) on breeding herds in France are described. Various aspects of its epidemiology and its immunological responses are touched on, together with means of diagnosis and methods of control. In particular, reference is made to a large-scale vaccination trial carried out over a one-and-a-half year period in the Bretagne and Loire regions of France. The value and efficacy of the inactivated PRRS vaccine Merial: Progressis is assessed and detailed results of its use in the trial are set out. Overall, the authors ascribe definite benefits to its use in breeding herds on a continued basis.

Porcine reproductive and respiratory syndrome: an update, with regard to vaccination.
DONE SH
Pig Journal 2001 48 : 159-176
Comprehensive update on porcine PRRSV. Among others, the author reviews the results of recent studies regarding vaccination and the problems that raises the use of PRRS vaccines:
the vaccine virus in some cases may return to virulence,
• vaccines may not provide sufficient protection against heterologous strains,
• immunity is slow to develop (several weeks after exposure to field virus or MLV PRRSV virus),
• vertical transmission,
• immune response in piglets may be delayed by maternally derived antibodies,
• horizontal transmission,
• virus shedding in semen when boars are not exposed to PRRSV prior to vaccination.

Experimental inoculation of late term pregnant sows with a field isolate of porcine reproductive and respiratory syndrome vaccine-derived virus.
NIELSEN J, BØTNER A, BILLE-HANSEN V, OLEKSIEWICZ MB, STORGAARD T
Vet Microbiol 2002 84 : 1-13
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The occurrence of PPRSV-like clinical problems in Danish herds is thought to be closely linked to vaccination with an American-type live attenuated vaccine virus. In order to verify this hypothesis an experimental infection of 6 late term pregnant sows (principal sows) with PRRSV vaccine derived virus (VDV) isolated from a stillborn pig was decided. A control group of 4 sows was also sham inoculated. The number of piglets (born live or dead) was recorded as well as the appearance of characteristic macroscopic lesions and serological status of sows and piglets. A higher number of deadborn pigs were observed for the principal sows compared to the control group. Macroscopic lesions of lungs were observed in over 50% of liveborn principal piglets with interstitial pneumonia in three-fourth of piglets. These lesions were typical of a PRRSV infection. PPRSV was detected in all principal sows by 14 post infection and their piglets had become viremic and PRRSV-antibody positive on day 10 after birth. The results of this experimental infection showed that PRRS-VDV isolated from field could cause PRRS-like symptoms in swine. Also PRRS-VDV being a derivative of the live attenuated vaccine virus used in Denmark, evidence of a correlation between PRRS-like signs observed in herds and previous vaccination with this same vaccine is manifest. The genetic vaccine reversion to virulence may be at the origin of clinical problems in Danish herds.

Shedding of porcine reproductive and respiratory syndrome virus in mammary gland secretions of sows.
WAGSTROM EA, CHANG CC, YOON KJ, ZIMMERMAN JJ
Amer J Vet Res 2001 62 : 1876-1880
Previous studies reported a possible transmission of viruses pertaining to the same order as PRRS virus (Nidovirales) via mammary gland secretions. PRRSV is known to be shed in saliva, urine, nasal secretions and semen but mammary gland secretions as a means of transmission of the virus has not yet been studied. Thus three experiments were conducted: in experiment 1 (6 pregnant sows), 2 sows were inoculated with a PRRS virus isolate, another two were administered a PRRSV vaccine and 2 were used as controls. In experiment 2, the 2 previously vaccinated sows were administered another vaccine and in experiment 3, 202 sows were selected from 10 herds (8 PRRSV infected herds). Mammary gland secretions from all sows were assayed for PRRSV by virus isolation and bioassay. It was found that sows exposed to PRRSV in experiment 1 shed virus in mammary gland secretions. However, in experiment 2 and 3, virus was not detected in samples from sows vaccinated twice and from the 202 commercial sows. It is the first time that shedding of virus in mammary gland secretions has been reported. Further investigation is needed to understand the role of immunity on such shedding.

A comparison of virus isolation, immunohistochemistry, fetal serology, and reverse-transcription polymerase chain reaction assay for the identification of porcine reproductive and respiratory syndrome virus transplacental infection in the fetus.
BENSON JE, YAEGER MJ, CHRISTOPHER-HENNINGS J, LAGER K, YOON KJ
J Vet Diagn Invest 2002 14 : 8-14
The objectives of the study were to compare the ability of these four tests (virus isolation, immunohistochemistry, fetal serology and RT-PCR) to identify PRRSV infection in fetuses obtained from sows experimentally infected with PRRSV about one month before term and to assess the impact of fetal autolysis and pooling of tissues. Out of the 107 piglets tested, 48.6% 23.4% and 14.9% were tested positive by VI, IHC and fetal serology respectively. A 100% of homology was obtained between the results of VI and RT-PCR with specimens allowed to autolyze at 4°C for 24 hours. The efficacy of RT-PCR is altered by fetal autolysis to a much lesser extent than that of VI, IHC and fetal serology. Moreover, thoracic fluids and tissues were shown suitable for RT-PCR.

Susceptibility of porcine circovirus type 2 to commercial and laboratory disinfectants.
ROYER RL, NAWAGITGUL P, HALBUR PG, PAUL PS
Journal of Swine Health and Production Vol.9,number 6 : 281-284
Several disinfectants were tested in order to assess their efficacy against PCV2. In laboratory conditions and to a certain extent, the virus proved susceptible to some of them suggesting that the use of appropriate disinfectants could reduce the impact of PCV-2 associated diseases.

Neonatal vaccination for Mycoplasma hyopneumoniae and post-weaning multisystemic wasting syndrome: a field trial.
ALLAN GM, MC NEILLY F, MC NAIR I, O’CONNOR M, MEEHAN B, GILPIN D, ELLIS J, TOWNSEND H, LASAGNA C, BORIOSI G, KRAKOWKA S
Pig Journal 2001 48 : 34-41
Following heavy losses due to PMWS, about one half of the piglet population of a herd was kept unvaccinated against Mycoplasma hyopneumoniae over a 4-month period. The results show a significant reduction in the losses due to PMWS in the non-vaccinated group.

An experimental model for post-weaning multisystemic wasting syndrome (PMWS) in growing piglets.
ALBINA E, TRUONG C, HUTET E, BLANCHARD P, CARIOLET R, LHOSPITALIER R, MAHE D, ALLEE C, MORVAN H, AMENNA N, LEDIMNA M, MADEC F, JESTIN A
AGENCE FRANCAISE SECUR SANITAIRE ALIMENTS PLOUFRA
J Comp Pathol 2001 125 : 292-303
This paper describes the development of a reproducible experimental model of PMWS. Six piglets from a PMSW-affected farm were obtained. Two of them presented severe PMWS signs. Inocula were prepared from the lung tissues of the two severely sick piglets and administered intratracheally to seven groups of SPF (specific pathogen free) piglets and one group of conventional ones. Mild PMWS characterized by an increased rectal temperature and growth retardation lasting three weeks was induced in the two groups after a long incubation period. However a severe form of the disease was observed in only four inoculated piglets. Laboratory investigations were performed to demonstrate the presence of a new virus resembling PCV in inocula and infected piglets. Serological tests to detect other pathogens were used and confirmed that no other common porcine pathogens were present in the inocula. As a result, PCV2 proved to be the primary agent in this experimental model of PMWS. Also secondary infections were shown to be not critical for the onset of PMWS but could contribute to a fatal outcome.

Kinetics of porcine circovirus type 2 replication.
CHEUNG AK, BOLIN SR.
Arch Virol 2002 147 : 43-58
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This paper reports the kinetics of porcine circovirus type 2 (PCV2) replication. Several techniques were used to examine the PCV2-infected PK cells for progeny viruses, viral RNAs and viral proteins.
- Northern blot analysis: total RNAs extracted from PCV2-infected cells were subjected to this analysis. Both DNA and RNA were detected starting at 18 h post infection and they increased as the infection progressed. Three PCV2 RNA species of 950, 750 and 450 nucleotides (nt) were detected.
- Western blot analysis: PCV2 cells were analyzed and a capsid protein of 35 kD in the cell lysates was detected at 30 h post infection.
- Immunohistological staining was used to monitor the progression of viral capsid protein expression in PCV2 infected cells and. With this technique viral-specific antigens were first observed in the nuclei and then in the cytoplasm as the infection progressed.
- In situ hybridization indicated that 750 and 450 nt RNAs shared some 3’ common sequences and that they are transcribed in the same orientation as the replication associated protein (Rep).
These results provide informative elements to understand PCV replication and the production of infection.

The effects of immuno-modulation on the clinical and pathological expression of postweaning multisystemic wasting syndrome.
KYRIAKIS SC, SAOULIDIS K, LEKKAS S, MILIOTIS CC, PAPOUTSIS PA, KENNEDY S
J Comp Pathol 2002 126 : 38-46
This trial included 84 pigs from a commercial herd affected by PMWS. Three groups of 28 pigs each were constituted, pigs either received an injection of Respisure® (Pfizer, NY, USA) or Baypamun® (Bayer, Leverkusen, Germany) or kept as controls. The objective was to determine whether the administration of a vaccine against Mycoplasma hyopneumoniae, and thus a non-specific immuno-modulation, could influence the outcome of PMWS. The use of both products was shown to increase the morbidity rate and the severity of the clinical signs, to induce more severe pathological lesions, and higher amounts of PCV2 antigen.

Cloned genomic DNA of type 2 porcine circovirus is infectious when injected directly into the liver and lymph nodes of pigs: characterization of clinical disease, virus distribution, and pathologic lesions.
J Virol 2002 76 :541-551
FENAUX M, HALBUR PG, HAQSHENAS G, ROYER R, THOMAS P, NAWAGITGUL P, GILL M, TOTH TE, MENG XJ
First report of infection with a cloned PCV2 plasmid DNA injected in liver and superficial iliac lymph nodes.