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Bulletin No. 16 - Autumn 2003

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Summary

There is a lot of information in this issue. Very briefly, PRRS virus (PRRSV) is confirmed to induce immunomodulation. Several papers have confirmed that CD8+ T lymphocytes play an important role in the defense against PRRSV.

PRRSV is also claimed to interfere with Swine influenza inactivated vaccines. This goes in the same direction as the previous findings of the same team (E. Thacker et al., ISU, Ames, IA) which showed an interference between PRRSV infection and M. hyo vaccination.

On the forefront of PCV2 research, among other topics under debate, the type of cell where the virus primarily replicates and the link between immuno-stimulation and PCV2 diseases are said to be still unknown.

Contents

Fourth International Symposium on Emerging and Re-emerging Pig diseases
  • General session
  • PRRS - (13 articles)
  • PMWS-PCV2 - (9 articles)
  • Swine influenza - (3 articles)
Sixth International Congress of Veterinary Virology
  • Evolutionary aspects of cell recognition by viruses.
  • New advances in veterinary vaccines.
  • Porcine repiratory coronavirus: a SARS model to be considered.
  • Bovine but not porcine are productively experimentally infected with caprine arthritis encephalitis virus (CAEV).
  • Cross-protection studies in pigs with serologically distinct swine influenza virus subtypes.
Bacterology
  • Mycoplasma hyorhinis
  • Mycoplasma hyopneumoniae
  • Escherichia coli & Clostridium perfrigens
Virology
  • Aujeszky's disease
  • Classical Swine Fever - (2 articles)
  • PRRS
  • PMWS-PCV2-PDNS - (3 articles)
Dermatology
  • Tail biting and tail docking in pigs.
  • Tail necrosis in pigs.
Miscelleanous
  • Asia's production dominance.
  • Cost competitiveness of leading exporters.
  • Problems of mycotoxins? and some solutions.
Parasitology
  • The effect of inulin and sugar beet fibre on Oesophagostomum dentatum infection in pigs.
  • Host age influence on the intensity of experimental Trichuris suis infection in pigs.
  • Efficacy of ivermectin premix against parasitic disease in piglets.
  • Study on some factors influencing the incidence of G I parasitism in pigs.
  • Helminth infections in Danish organic swine herds.
  • Associated disease caused in pigs by Ascaris and Oesophagostomum.
  • Internal parasitism of feeder pigs in Southern Illinois.
  • Some aspects of the epizootiology and economic significance of ascariasis in swine.
  • The gradual weaning process in outdoor sows and piglets in relation to nematode infections.
  • The incidence of helminth infections in sows and piglets in southern Germany.
  • The influence of stocking rate on transmission of helminth parasites in pigs on permanent pasture during two consecutive summers.
  • A survey of parasite infection on organic, free range and conventional pig farms in the Netherlands.

Fourth International Symposium on Emerging and Re-emerging Pig diseases - Rome 2003

General session

MENGELING WL
How viruses change.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 3-8
Keywords: PRRSV, SIV, GENETIC CHANGE
The ways by which viruses change are reviewed: point mutation, recombination, reassortment, deletions and insertions, with particular attention to porcine reproductive and respiratory syndrome (PRRS) and influenza viruses.
  • Point mutations ("antigenic shift" in influenza virus) result from RNA polymerase errors of base incorporation and are associated or not with effect on phenotype (virulence). Currently available tools provide a consensus sequence of a virus but cannot provide a perfect, comprehensive picture of the genetic diversity due to mutations. Moreover, the actual effect of mutations on virulence still requires a better understanding.
  • Recombination: cells must be infected simultaneously, or almost so, with more than one viral strain. High levels of replication and long-lasting persistence of viruses increase the probability of recombination between them. Three categories of recombination are defined: between and among virulent strains (the more likely under field conditions), between and among virulent and attenuated (vaccine) strains, between and among attenuated strains (multi-strain vaccine). In all cases, the levels of virulence and replication of the recombinant strain should be the main matters of concern.
  • Reassortment ("antigenic drift" in influenza virus) involves discrete segments of genome and is limited to viruses with segmented genome. The strains of influenza virus are defined thanks to the combination of two major surface proteins (hemagglutinins and neuraminidases respectively responsible for the attachment and the release of the virus to and from cells) which are as many expressions of reassortment. Interspecies reassortants such as the swine H3N2 subtype increase the complexity of this phenomenon.
  • Deletions and insertions have a limited impact in comparison with the foregoing ways of genetic change, at least regarding PRRSV and SIV. However, they are not devoid of interest since porcine respiratory coronavirus (PRCV), for example, is assumed to be a respiratory variant of porcine transmissible gastroenteritis virus (TGEV) as a result of deletion.
In any case the future of an altered virus depends on its ability to replicate, its affinity for cell receptors and its capacity to evade the host's immunity.
      Virus changes are thus to be considered more a result of successful mistakes than a designed tactical plan. One must also keep in mind that other factors may urge virus changes, namely high densities of animals in intensive management, the increase in long-distance transports and the use of artificial insemination. In future, the main difficulty will be to keep the lead over the evolution of pathogens.

PRRS

LAGER KM
Porcine reproductive and respiratory syndrome : control and vaccinology.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 29-36
Keywords: PRRSV, CONTROL, VACCINOLOGY
Updated knowledge regarding epidemiology, immunology and vaccinology is presented together with the available strategies of control and prevention. Even if data keep on accumulating, PRRS is still a complex and mysterious disease lacking absolute rules. The part played by indirect transmission still needs further investigations. The mechanisms of immune response are still wooly and genetic diversity of PRRSV associated with the limited or lack of cross-protection hamper control and prevention of the disease. Eradication of PRRS will not occur in an immediate future, a better understanding of the transmission of PRRSV and the development of innovative vaccines thanks to adjuvants (cytokines, immunoactive peptides) or new technologies (DNA, PRRSV-deletion mutant, viral and bacterial-vectored PRRSV genes) are needed.

LAROCHELLE R, D'ALLAIRE S, MAGAR R
Molecular epidemiology of porcine reproductive and respiratory syndrome virus (PRRSV) in Qu?bec.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 41-42
Keywords: PRRS, EPIDEMIOLOGY, ORF5 SEQUENCES, PHYLOGENY
The sequences of the ORF5 of 250 samples cases were amplified by PCR and investigated so as to carry out a grouping of strains. The results were successively associated with epidemiological data collected through a questionnaire filled for each submitted case. The results confirmed the high genomic variability of PRRSV and provided interesting findings regarding the suspected relationships between strains within groupings. The common denominator in 19% of strains was the introduction of new animals, geographic location in 33% of strains (aerosol transmission is likely to be involved in more than half of the cases), vaccine-like strains in 14% of strains. This findings born from the association of molecular and epidemiological investigations allowed veterinarians to propose more concrete information to swine specialists.

XIAO Z, MURTAUGH MP, JONHSON CR, BATISTA L, DEE SA
Immunity to porcine reproductive and respiratory syndrome virus (PRRSV) : systemic and local responses in acute and persistent infection.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 45-46
Keywords: PRRS, IMMUNITY, INTERFERON GAMMA, ENVELOPE GLYCOPROTEIN
Humoral and cell-mediated immune responses to PRRSV were assessed in peripheral blood and lymphoid tissues during acute and persistent infection. In a first experiment, 120 gilts of four months of age were inoculated with a PRRSV strain while in a second experiment 33 pigs of 5-6 weeks of age were inoculated with Ingelvac? PRRS ATP vaccine strain. The increase of antibodies to GP5 appeared to be associated with clearance of virus from the circulation. The proportion of interferon gamma secreting T cells was determined and provided a scale to measure cell-mediated immune response to PRRSV. The results show great individual variations in the ability to develop immunity to PRRSV infection as well as a lack of stimulation of cell-mediated immune response which both probably facilitate the establishment of persistent infections. The significantly increased levels of CD8+ cells suggest that these lymphocytes are likely to play a great role in immunity to PRRSV. Tonsils showed high levels of virus and particularly low levels of activated lymphocytes, they are thus assumed to be somehow involved in PRRSV infection. The results also indicate that stimulating the initial immune response, known to be inefficient to PRRSV, may be a way of improving humoral and cell-mediated immune response to PRRSV.

NIELSEN J, B?TNER A, AASTED B, JOHNSEN CK, RIBER U, TINGSTEDT JE, LIND P
In utero infection with PRRSV affects immune functions of surviving piglets.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 47-48
Keywords: PRRSV, IMMUNITY, IN UTERO INFECTION
Piglets born of PRRSV experimentally infected sows (inoculation at 90 days of gestation) were submitted to virological, serological, hematological and immunological examination prior uptake of colostrum and every two weeks until 6 weeks of age, the results were then confronted to those obtained in control piglets born of sham-inoculated sows. The immune cell population results deeply altered in surviving infected piglets. CD8+ cells in particular, are of great interest since they are clearly involved in the control of PRRSV replication. The analysis of bronchoalveolar lavage fluid also suggests interferon gamma and IL-10 as protagonists in immunity to PRRSV. In infected piglets, peripheral blood mononuclear cells (PBMC) capacity of phagocytosis proved to be inhibited, which illustrates the lack of immune response PRRSV finds when infection occurs. In addition, the interaction of PRRSV with the immune system predisposes infected animals to secondary infections.

VAN GUCHT S, VAN REETH K, LABARQUE G, NAUWYNCK H, PENSAERT M
PRRSV infection increases CD14 expression and LSP-binding protein in the lungs : possible mechanisms of PRRSV-LPS clinical synergy.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 49-50
Keywords: PRRSV, PATHOGENESIS, LPS, CD14, LBP
The binding of lipopolysaccharides (LPS: endotoxins of Gram-negative bacteria) to CD14 (membrane receptors expressed in monocytes, macrophages and neutrophils) is increased by LPS-binding proteins (LBP). The aim of this study was to confirm or reject the hypothesis that PRRSV infection increases CD14 expression and LBP in the lungs and induces sensitization for LPS. To this end, CD14 and LBP were quantified throughout PRRSV infection. The results clearly show an increased expression of CD14 receptors by monocytes-macrophages and increased LBP, suggesting that this mechanism may account for at least part of sensitization to LPS. A following exposure to LPS will thus result in the production of proinflammatory cytokines and respiratory signs.

DEE S, OTAKE S, ROSSOW K, MOON R, PIJOAN C
Transmission of PRRSV by individual houseflies (Musca domestica)
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 53
Keywords: PRRS, EPIDEMIOLOGY, TRANSMISSION, VECTOR, HOUSEFLY
Transmission of PRRSV from infected pig to susceptible pig by houseflies as mechanical vectors was demonstrated. The intestinal tract of flies can harbor the virus for up to 12 hours suggesting that houseflies may also allow farm-to-farm transmission of PRRSV.

MARTELLI P, CORDIOLI P, FALLACARA F, TERRENI M, CAVIRANI S
Genetic diversity (ORF5) of PRRSV isolates from a herds with SAMS
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 56-57
Keywords: PRRS, VIRUS SEQUENCING, GENETIC DIVERGENCE, ORF5
During an outbreak of sow abortion and mortality syndrome (SAMS), virus isolation and DNA sequencing of ORF5 in sows, weaners and replacement gilts were carried out. All isolates of PRRSV were shown to belong to the European type but although isolated within the same herd, they demonstrated great genomic diversity. The concomitant presence of three different strains of PRRSV (likely introduced with replacement animals or semen) in a single herd illustrates the existence of multiple PRRSV infections and the need for appropriate control strategies.

STADEJEK T, STANKIEWICZ I, PEJSAK Z
Concurrent circulation of PRRSV-US within swine herd in Poland.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 67-68
Keywords: PRRSV, DIAGNOSIS, MLV, VACCINE SAFETY, CONTROL
Primarily, the genotypes of PRRSV (American or European), were linked to the initial geographic distribution from which they had taken their name. However, such perfect match is not valid anymore since both types have been detected where they were originally not present. In this report of PRRSV-US infection in a Polish swine herd, Ingelvac? PRRS modified live vaccine (Boehringer Ingelheim) is recognized as the source of the circulating virus.

SURADHAT S, THANAWONGNUWECH R
Upregulation of IL-10 gene expression in the peripheral blood mononuclear cells (PBMC) of pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV).
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 83-84
Keywords: PRRS, IMMUNOLOGY, IL-10
In vitro, upregulation of IL-10 due to PRRSV has been shown to negatively alter the immune functions of peripheral blood mononuclear cells (PBMC). This study confirms the same effect of PRRSV in vivo: rapidly stimulating the production of an immunosuppressive cytokine such as IL-10, PRRSV hampers the host immune responses and induces only a weak innate immunity.

DASTIG B, SCHMOLL F, LANG CH, IRGANG P, SPERGSER MJ, SCHUH, SIPOS W
Detection of pathogens in aborted fetuses and stillborn piglets.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 88-89
Keywords: PRRSV, PCV2, EPIDEMIOLOGY, REPRODUCTION, INFECTIOUS INFERTILITY
Porcine reproductive and respiratory virus (PRRSV), porcine parvovirus (PPV), leptospirae and chlamydiae/chlamydophilae are the pathogens commonly held responsible for reproductive disorders. However, the role played by PCV2 may be of interest. In this study, 202 aborted fetuses or stillborn piglets from 113 litters of 27 Austrian farms were investigated. The presence of PCV2 was unexpectedly demonstrated in 20.5% of the litters (61.1% of the investigated litters were tested positive for at least one infectious agent). In order to obtain a reliable etiological diagnosis in case of reproductive failures, it appears essential to examine numerous litters and take into consideration all pathogens mentioned above.

NILUBOL D, THACKER BJ, HARRIS DL, THACKER EL
PRRSV vaccination study: interleukin-12 to enhance killed vaccine immunity and combined vaccination with modified live and killed vaccines.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 113-114
Keywords: PRRS, LIVE AND KILLED VACCINATION, IMMUNE RESPONSES
Several vaccination protocols were compared in order to assess their ability to induce immune responses: PRRSV killed vaccine (KV) alone, PRRSV KV added IL-12, PRRSV modified live vaccine (MLV) alone and PRRSV MLV combined with PRRSV KV. All treatments groups were challenged intranasally with PRRSV. Investigations were based on ELISA, seroneutralization and lymphocyte proliferative responses. The use of IL-12 added to PRRSV KV failed to enhance immune responses. In addition, the results show that the combined MLV and KV protocol allows more rapid antibody and cell-mediated immunity responses. Further investigations in this direction are needed.

GIOVANARDI D, PESENTE P, SPERATI RUFFONI L, SANDRI GP, CAMPAGNARI E, MOTTA C
A testing procedure to evaluate gilts' PRRSV acclimatization.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 121-122
Keywords: PRRSV, CONTROL, ELISA, NESTED PCR
In order to reduce the risk of PRRS outbreaks, replacement gilts can be exposed and infected with homologous farm-specific strains of PRRSV before their introduction into PRRS positive farms (acclimatization). At that point, it is necessary to determine the immune status of each gilt and segregate the viremic ones. Clinical signs were shown to be a too subjective and unreliable way to establish viremia. Two testing procedures are investigated: ELISA and nested PCR. In a routine context, the detection of IgG-IgM antibodies by ELISA provides the best cost/benefit ratio.

THACKER E, KITTIKOON P, VINCENT A, HIPPLE K, NILUBOL D, YU S, JANKE B, THACKER B
Influence of PRRS virus infection on swine influenza vaccine efficacy
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 281-282
Keywords: PRRS, INTERFERENCE, FLU VACCINATION, INFLUENZA
Confirming other studies from the same research group performed with M. hyo bacterins, PRRS virus infection when occuring between the two injections of the vaccination was shown to strongly interfere with Swine influenza vaccination with an inactivated vaccine.


PMWS-PCV2

KRAKOWKA S, ELLIS JA, MAC NEILLY F, MEEHAN B, RINGS DM, MAC CULLOUGH K, B?TNER A, NAUWYNCK H, CHARREYRE C, ALLAN G
The pathogenesis of PCV-2-associated postweaning multisystemic wasting syndrome in swine.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 143-148
Keywords: PCV2, PMWS, GNOTOBIOTICS, SWINE, PIGS, CYCLOSPORINE, IMMUNOSTIMULATION
Much work has been done and remains to be done on postweaning multisystemic wasting syndrome (PMWS) and its, now recognized as such, necessary causal agent porcine circovirus type 2 (PCV2). Prior to the first reported outbreaks of PMWS in 1991, PCV2 infection was already occurring, but such a sporadic infection has mysteriously changed into an epidemic disease. This brief review presents the states of the art regarding PMWS and PCV2 with references to experimental reproduction of the subclinical infection and PMWS in gnotobiotic swine by oral inoculation. The monocyte-dendritic cell-macrophage lineages are known to harbor infectious material and are a key feature of the disease. However the primary cellular tropism of PCV2 as primary site of replication still needs to be identified. Gut epithelia, hepatocytes, vascular endothelia, K?pffer cells and histiocytes-like cells have been studied as early virus-permissive cells and represent a lead to further investigate. A dose-effect correlation is on the way to be demonstrated between amounts of PCV2 in tissues and clinical expression of the disease. Another unknown factor is still the link between immunostimulation (early vaccinations) or immunosuppression (cyclosporine) and the genesis of the disease.

SEGALES J, CALSAMIGLIA M, DOMINGO M
How we diagnose postweaning multisystemic wasting syndrome.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 149-151
Keywords: PMWS, DIAGNOSIS, CASE DEFINITION, PCV2
To be diagnosed as suffering from PMWS, a pig or a group of pigs must abide by three criteria, namely, typical clinical signs, typical histopathological lesions and detection of PCV2 in lymphoid tissues. One should always keep in mind that: not all pigs with wasting suffer from PMWS; although PMWS implies PCV2, the presence of PCV2 does not mean PMWS and the viral load is one of the determining factors in the expression of the disease; the detection of low amounts of PCV2 associated with only slight lesions could indicate subclinical PMWS but also an initial phase of the disease or an ongoing convalescence; PMWS can be present either in herds with good or bad performance; other diseases may be concomitantly present in a PMWS affected herd. So far, histopathological findings added to virus detection in tissues by immunohistochemistry or in situ hybridization have been considered the golden standard to establish a PMWS diagnosis. However, due to the likely correlation between amounts of PCV2 and severity of clinical signs, a quantitative PCR represents a useful (but still expensive) technique in the field of PMWS diagnosis. With regards to the epidemiological aspects of PMWS and in particular to the concept of enzootic disease (usual occurrence or constant presence of a disease), the author proposes the following criteria for a herd case definition: occurrence of clinical process characterized mainly by wasting, in excess of the expected level; and individual diagnosis in a pig or a group of pigs thanks to the three criteria mentioned before.

VINCENT IE, CARRASCO CP, HERRMANN B, MEEHAN B, ALLAN GM, SUMMERFIELD A, MAC CULLOUGH KC
Dendritic cells: a Trojan horse for porcine circovirus type 2?
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 163
Keywords: PMWS, PATHOGENESIS, DENDRITIC CELLS, INFECTION, T LYMPHOCYTES
The results of this study show that:
  • PCV2 does not replicate in dendritic cells (DCs)
  • PCV2-infected DCs do not alter the expression of surface markers in monocyte-derived DCs nor in bone-marrow-derived DCs.
  • infected DCs do not transmit PCV2 infection to T lymphocytes, nor induce PCV2 replication in DCs.
Therefore, a direct interaction between dendritic cells and lymphocytes cannot account for the process of immunosuppression due to PCV2 infection.

MEEHAN BM, MAC NEILLY F, ELLIS JA, KRAKOWKA S, FOSSUM C, LASANGE C, ADAIR BM, VENTURA R, MAC NAIR I, ALLAN GM
Genotyping versus pathotyping for the characterization of PCV-2 isolates.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 170-171
Keywords: PMWS, GENOTYPE, PATHOTYPE, PCR
Genotype analysis alone does not provide useful information regarding pathogenicity of PCV2 strains and should be combined with experimental disease reproduction.

SEGALES J, SCHULZE C, GORTAZAR C, VICENTE J, DOMINGO M
First description of postweaning multisystemic wasting syndrome in the wild boar (Sus scrofa) in Europe.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 177-178
Keywords: PMWS, DIAGNOSIS, WILD BOAR, EUROPE
A serological study of the wild boar population of Europe has already shown that this specie is susceptible to PCV2 infection. The necropsy of 4 PCV2-seropositive wild boars allowed the authors to make the first report of PMWS in this specie since two of the investigated animals showed wasting, typical lymphoid lesions among with high amounts of PCV2 nucleic acid in affected lymphoid tissues.

WANG ZT, YANG HC, GUO X
Epidemiological investigation on infection of porcine circovirus type 2 in intensive swine farms in China.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 179-180
Keywords: PMWS, PORCINE CIRCOVIRUS TYPE 2, EPIDEMIOLOGICAL INVESTIGATION
In this study, 55 samples of diseased or dead pigs from 12 intensive herds in 6 Chinese provinces were investigated. PCV2 was shown to be ubiquitous in Chinese swine herds. The presence of the virus was mainly detected in lymph nodes and spleen. In China, PMWS represents a important threat for swine industry and already causes significant economic loss.

LADEKJ?R-MIKKELSEN AS, B?TNER A, NIELSEN J, HASSING AG, BAEKBO P
Serological profiles in Danish PMWS case and control herds.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 184-185
Keywords: PMWS, EPIDEMIOLOGY, PCV2, PPV, SEROLOGICAL PROFILES
This study included four case herds (with diagnosed PMWS) and four control herds (without clinical signs of PMWS) in which porcine parvovirus (PPV) and porcine circovirus type 2 (PCV2) serological profiles were monitored. Pigs in case herds seroconverted earlier to PCV2 in relation to those in control herds. No correlation between the two pathogens and the development of PMWS could be established.

DE BOISSESON C, BEVEN V, BIGARRE L, THIERY R, ROSE N, EVENO E, MADEC F, JESTIN A
Characterization and comparison of porcine circovirus sequences from postweaning multisystemic wasting syndrome affected and non-affected herds.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 186
Keywords: PMWS, EPIDEMIOLOGY, PCV, VIRULENCE
A total of 38 tissue samples collected in pigs originating from seven PMWS-diagnosed herds (PMWS(+)) and seven non-PMWS (PMWS(-)) herds were collected. PCV1 and PCV2 DNA was detected, amplified and sequenced. PCV1 was not detected in any of the submitted sample. PCV2 prevalence in PMWS(-) herds was high (83%). The sequencing of PCV2 genomic sequences obtained from the various tissue extracts confirmed a high nucleotide identity. No virulence factor in PMWS(+) strains could be identified.

LAROCHELLE R, MAGAR R, D'ALLAIRE S
Comparative serological and virological study of herds with and without postweaning multisystemic wasting syndrome (PMWS).
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 226-227
Keywords: PMWS, ETIOLOGY, PCV2, PRRSV
Even if PMWS implies PCV2, PCV2 infection does not necessarily induces PMWS. Three experimental models have been demonstrated to trigger PMWS in PCV2-infected pigs: co-infection with porcine parvovirus (PPV), co-infection with porcine reproductive and respiratory syndrome virus (PRRSV) and immunostimulation. Yet to date, no field study could provide information of that kind regarding PMWS/PCV2 field reality. Kinetics of PCV2 infection and sequence of PCV2 in PMWS and non-PMWS herds were investigated as well as the presence of PPV, PRRSV and the use of immunomodulating agents (vaccines). No difference either in the kinetics of PCV2 infection nor in the genomic sequence of PCV2 strains between PMWS and non-PMWS was determined. No link between either PMWS and co-infection with PPV or PRRSV nor PMWS and immunostimulation could be established. The triggering mechanisms of PMWS need to further investigated.


Swine influenza

VAN REETH K, LABARQUE G, PENSAERT M
The establishment of an H1N2 influenza virus in the European swine population and its impact on prevention and control.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 250-253
Keywords: SWINE INFLUENZA, IMMUNITY, CONTROL, DIAGNOSIS, H1N2 SUBTYPE
Experimental challenges show that, even if influenza viral strains have been drifting since vaccines were designed, the available swine influenza vaccines provide a complete clinical protection against the current H1N1 and H3N2 viruses. Consequently, no updating of H1N1 or H3N2 vaccine strains is needed. On the contrary, commercial vaccines should be supplemented with an H1N2 component, if nonetheless the prevalence and clinical importance of H1N2 infections justify it, since H1N1/H3N2 vaccines do not prevent H1N2 virus replication nor disease. However, cross-infection studies have demonstrated that pigs that are immune due to a prior infection with both H1N1 and H3N2 may develop immunity against H1N2 as well. Still regarding cross-protection, dually H1N1/H1N2 infected-immune pigs were experimentally shown to develop reliable immunity against H3N2. These data indicate that cross-protection against a distinct influenza virus subtype results are efficient following infection. In addition, other investigations showed that hemagglutination inhibition test (HI) can discriminate between H1N1, H3N2 and H1N2 subtypes without inducting serologic cross-reaction.

BARIGAZZI G, FONI E, CHIAPPONI C, LEOTTI G, LONGO S, JOISEL F
Use of a standard kit for the diagnosis of respiratory viral infections in pigs.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 268-269
Keywords: INFLUENZA, DIAGNOSIS, EPIDEMIOLOGY, RESPIRATORY INFECTIONS, NASAL SWABS
A standard kit for the diagnosis of viral pathogens involved in acute respiratory disorders in pigs in the fields.The kit allowed the practicioner to take nasal swabs and blood sample at the first visit and another blood sample on the same pigs (ear tagged) one month later. Different diagnosis methods focused on PRRS, ADV and SIV were applied, including PCR, virus isolation in cells and eggs and serology depending on the pathogen. SIV was found to be a player in 12 out of t a total of 15 cases and in 9 out of 12 the virus was evidenced using a virological method. On the contrary, PRRS was found only twice by PCR in the swabs and 3 times by seroconversion. It is concluded that Flu is dramatically underestimated in acute respiratory episodes occuring in Italy.

CANDOTTI P, FONI E, LEOTTI G, JOISEL F, LONGO S, ROTA NODARI S
Serological prevalence for swine influenza virus in pigs between 3 and 15 weeks of age in Italian farms: evaluation of a maternal antibody decay curve.
Proceedings of the 4th International Symposium on Emerging and Re-emerging Pig Diseases, 2003, 272-273
Keywords: SIV, SEROLOGY, MATERNAL ANTIBODY CURVE, PIG
In order to avoid any interference due to maternally derived antibodies, it is necessary to determine the most appropriate time for Flu vaccination. To this end, a maternal antibody decay curve was evaluated for influenza virus subtypes H1N1, H3N2 and H1N2 in 1000 piglets from 21 farrow-to-weaning or farrow-to-finish Italian herds, from 3 weeks to 15 weeks of life. Due to the low prevalence of the H1N2 subtype, a curve was difficult to evaluate. As far as H1N1 and H3N2 are concerned, the obtained curves showed a linear decline. The hemagglutination inhibition (HI) antibody titers under 1:40, i.e. the minimum to obtain protection after challenge with the virulent H1N1 subtype, were extrapolated from the curves and corrisponded to 15 and 23 weeks respectively for H1N1 and H3N2 subtypes. The groups of 3 and 6 weeks of age showed a significantly higher seroprevalence for subtypes H1N1 and H3N2 in relation to the other age groups, indicating that most piglets over 6 weeks of age do not have maternal antibodies anymore.

Sixth International Congress of Veterinary Virology - Saint-Malo (France)

BARANOWSKI E, RUIZ-JARABO CM, PARIENTE N, VERDAGUER N, DOMINGO E
Evolutionary aspects of cell recognition by viruses.
Proceedings of the 6th International Congress of Veterinary Virology, 2003, 32-34

One specific cell receptor can be used by viruses that belong to distant families and closely related viruses can use different receptor types. Consequently, there is no obvious correlation between the two, so that virus-receptor interactions are unpredictable and are to be studied individually. Some DNA viruses, such as poxviruses and herpesviruses, take advantage of their genome complexity to deceive the immune system imitating chemokines or chemokine receptors. Other DNA viruses have at their disposal various molecules to interact with different cell receptors and switch cell tropism. RNA viruses play the card of adaptability with high mutation rates. In addition, viruses that use some receptors in vivo may develop alternative strategies to interact with different receptors in vitro, as it is the case for classical swine virus in swine kidney cells. In vitro, these shifts of receptor usage may be associated with adaptation to new hosts. Foot-and-mouth disease is mentioned as an example of remarkable flexibility in receptor usage. Such a process has already been shown to also occur in vivo and represents a major source of concern regarding the emergence of human and animal diseases.

AUDONNET JC
New advances in veterinary vaccines.
Proceedings of the 6th International Congress of Veterinary Virology, 2003, 42-45
The group of classical vaccines comprises live vaccines, inactivated vaccines and subunit vaccines, all of them are briefly reviewed. Novel-technology-based vaccines, which progressively substitute classical vaccines, utilize recombinant DNA or other novel technology. Modified or deleted vaccines allow to make a virus or a bacteria highly unlikely or unable to revert to virulence, and allow as well to differentiate vaccinated from infected animals. The technology of live vectored vaccines consists in inserting genes in a non-pathogenic carrier (virus or bacteria) so as to present a recombinant immunogen to the immune system, in a situation identical to infection and trigger immune responses. Poxviruses are already used as vaccine vectors, several examples are reviewed. Herpesvirus vectors are investigated as well, in particular for poultry vaccines. Adenovirus vectors are under development, the main example available is that of canine adenovirus type 2 (CAV2) as vector of canine distemper virus (CDV) HA and E proteins. This vaccine was shown to provide effective protection in seronegative dogs using intranasal route and in seropositive dogs using the subcutaneous route. Among potential live bacterial vectors, Salmonella represents a vector of choice for animal use but no conclusive results has been obtained yet. The technology of recombinant subunit vaccines consists in using bacteria (E.coli) to produce immunogenic factors. These type of vaccines is often associated to adjuvants in order to enhance immunogenicity. Another pathway is DNA vaccines, that is the insertion of genes (naked DNA) within transinfected cells and their subsequent expression by the cells. DNA vaccination represents a field with great prospects. Even if peptide-based vaccines could be another direction to explore, the underlying complexity of such a technology keeps them off of any commercial reality. Much work will be necessary in order to further develop and master novel technology based vaccines and fully introduce them on the market.

VAN REETH K, PENSAERT M
Porcine repiratory coronavirus: a SARS model to be considered.
Proceedings of the 6th International Congress of Veterinary Virology, 2003, 47
Keywords: PORCINE RESPIRATORY CORONAVIRUS, SARS-COV, RESPIRATORY PATHOGENESIS, CYTOKINES, MULTIFACTORIAL DISEASE
Pathogenesis of porcine respiratory coronavirus (PRC) is reviewed and compared with that of severe acute respiratory syndrome (SARS) coronavirus. PRC derives from swine transmissible gastroenteritis virus (TGEV) by deletion but shows a pronounced tropism for the respiratory tract. PRC in itself induces only mild respiratory signs but can contribute to multifactorial respiratory disease, in particular when combined with lipopolysaccharides of E. coli, this combination may be an interesting model to study multifactorial respiratory disease. An hypothesis is that, in fact, SARS may be a multifactorial disease with SARS coronavirus (SARS-coV) as primary agent. PRC is thus considered as a valuable model to study the pathogenesis of SARS-coV.

AOGNINOUWA T, GUIGUEN F, BOUZAR B, VILLET S, DURAND J, GALLAY K, GOUNEL F, FIROUZI F, CHEBLOUNE Y
Bovine but not porcine are productively experimentally infected with caprine arthritis encephalitis virus (CAEV).
Proceedings of the 6th International Congress of Veterinary Virology, 2003, 55
Keywords: BOVINE, PORCINE, ARTHRITIS, PERSISTENCE, PATHOLOGY
A complete resistance of piglets to CAEV infection was demonstrated : no virus replication nor specific response were observed.

VAN REETH K, LABARQUE G, BROWN I, PENSAERT M
Cross-protection studies in pigs with serologically distinct swine influenza virus subtypes.
Proceedings of the 6th International Congress of Veterinary Virology, 2003, 72
Keywords: SWINE INFLUENZA, GENETIC ANALYSIS, CROSS-PROTECTION, IMMUNITY
Cross-protection was already demonstrated to occur against H1N2 following successive infection with the H1N1, H3N2 and H1N2 subtypes. The objective of this study was to determine whether cross-protection is also provided when pigs are exposed to the same subtypes but in another sequence. Infection-induced immunity against any of the 3 subtypes provided partial cross-protection against the other subtypes. Interestingly, cross-protection was considerably enhanced in case of a dual infection. The results also show that cross-protection may depend on non-neutralizing cross-reactive antibodies against viral proteins distinct from haemagglutinin (HA). In addition, the high percentage of homogeneity detected between the various subtypes suggests that nucleoproteins and matrix proteins may be involved in cellular immunity.

Bacteriology

Mycoplasma hyorhinis

SHIN JH, JOO HS, LEE WH, SEOK HB, CALSAMIG M, PIJOAN C, MOLITOR TW
Identification and Characterization of Cytopathogenic Mycoplasma hyorhinis from Swine Farms with a History of Abortions.
Journal of Veterinary Medical Science, 2003, Volume 65, N?4, 501-509 Free on line : http://jvms.jstage.jst.go.jp/
Keywords: DIFFERENTIAL DISPLAY, GENETIC IDENTIFICATION, MYCOPLASMA HYORHINIS
This paper reports the successive steps that led to the identification and characterization of a variant of Mycoplasma hyorhinis as the cytopathic agent isolated from swine farms with recurrent abortion episodes. The use of differential display reverse transcription-polymerase chain reaction (ddRT-PCR) was the first step of the study and allowed to direct the authors towards mycoplasma and then to Mycoplasma hyorhinis. It is the first report within M. hyorhinis species of such a high cytopathogenetic effect on swine tracheal organs. In addition, the unexpected high percentage of similarity between the 5' portion of a gene of M. hyorhinis and 5'untranslated region (UTR) of human prostate tumor inducing gene 1 (PTI-1) suggests that M. hyorhinis might have been related to the evolution of human PTI-1.


Mycoplasma hyopneumoniae

BURCH DGS
The role of maternally derived antibodies, age and other factors on vaccinal response (the percentage game).
Pig Journal, 2003, Volume 51, June, 242-257
Following an introduction presenting the main features of Mycoplasma hyopneumoniae infection and the effects of passive immunity on vaccinal response, non-specific and specific immunity mechanisms in relation to enzootic pneumonia are reviewed as well as their development in fetus and newborn piglets. The efficacy of various types of vaccines and adjuvants is also discussed. As a conclusion, the author draws up an inventory of the main points concerning M. hyopneumoniae vaccination: maternally derived antibodies (MDA) can have a negative influence on vaccinal response; conversely, age is not a primary factor to consider in terms of vaccination; control of infection may be more easily correlated to surface immunity (IgA) rather than to humoral or cell-mediated immunity (CMI); M. hyopneumoniae vaccines do reduce lung lesions but with pig-to-pig variations.


Escherichia coli & Clostridium perfrigens

DORA B, BILKEI G
Post-weaning problems in outdoor pig production caused by Escherichia coli and Clostridium perfringens type A.
Pig Journal, 2003, Volume 51, June, 92-97
Some strains of Clostridium perfringens type A (CpA) are part of the normal intestinal flora of pigs. However, CpA and Escherichia coli (E. coli) dual infections can be responsible of high morbidity and mortality (diarrhea) and are now considered as an emerging problem for outdoor raised grower pigs in Croatia. A description of a prophylactic medication aimed at reducing post-weaning losses is reported. Better results are obtained when such medication is implemented against both CpA and E.coli rather than against only one of them.

Virology

Aujeszky's disease

MULLER T, BATZA HJ, SCHLUTER H, CONRATHS FJ, METTENLEITER TC
Eradication of Aujeszky's disease in Germany.
Journal of Veterinary Medicine. B, 2003, Volume 50, n?5, 207-213
Since February 2003, the whole territory of Germany is included in the list of Member States and regions free of Aujesky's disease (Commission decision 2003/130/EC). This could be achieved thanks to a national eradication program involving gE-deleted vaccines (marker vaccines).


Classical Swine Fever

FLOEGEL-NIESMANN G, BUNZENTHAL C, FISCHER S, MOENNIG V
Virulence of recent and former classical swine fever virus isolates evaluated by their clinical and pathological signs.
Journal of Veterinary Medicine. B, 2003, Volume 50, n?5, 214-220
This study carried out with four recent classical swine fever virus (CSFV) underlines that clinical diagnosis of CSF in pigs up to 14 days post-infection is a tricky thing. In order to detect CSF infection at an early stage and thus limit the spread of the virus, careful differential diagnosis and laboratory investigations are needed.

TOO H, SENEQUE S
Scourge of the Asian pig industry.
Asian Pork Magazine, 2003, Volume 19, June/July, 24-26
Despite an eradication program implemented in the early 1980's, sporadic classical swine fever (CSF) outbreaks still occur in Europe resulting in high economic costs. However, the situation of Asian countries is of even greater concern. There, CSF is widespread but effective eradication programs are very difficult to implement due to the lack of involvement of small raisers. As a result, sanitary management and vaccination with modified live vaccines are likely to remain the main methods used to control CSF. To help swine practitioners the authors of this article have, with the assistance of Merial, published a handbook that covers epidemiology and clinical diagnosis, post-mortem examination, laboratory diagnosis and vaccination concepts for CSF.


PRRS

VANDERHEIJDEN N, DELPUTTE PL, FAVOREEL HW, VANDEKERCKHOVE J, VAN DAMME J, VAN WOENSEL PA, NAUWYNCK J
Involvement of sialoadhesin in entry of porcine reproductive and respiratory syndrome virus into porcine alveolar macrophages.
Journal of Virology, 2003, Volume 77, N?15, 8207-8215
The results of this study together with those of previous experiments show that:
  • Mab41D3 (monoclonal antibody which binds specific receptors present on macrophage surface membrane) was shown to recognize porcine sialoadhesins on porcine alveolar macrophages (PAMs) and to prevent PRRSV infection of PAMs;
  • PK-15 cells, when they are modified so as to express sialoadhesins on their membrane, are no more resistant to PRRSV-infection;
  • MAb41D3 recognized sialoadhesins in all PRRSV-infected cells from experimentally infected pigs, showing that all these cells do express sialoadhesins;
  • MAb41D3 was internalized by encytosis into PAM, showing that sialoadhesins are involved in the process of endocytosis.
Therefore, the role of sialoadhesins in the entry of PRRSV into PAMs was clearly demonstrated. The next step would be to identify the viral sialoadhesin-binding molecules.


PMWS-CIRCOVIRUS-PDNS

NUNEZ A, MCNEILLY F, PEREA A, SANCHEZ-CORDON PJ, HUERTA B, ALLAN G, CARRASCO L
Coinfection by Cryptosporidium parvum and porcine circovirus type 2 in weaned pigs.
Journal of Veterinary Medicine. B, 2003, Volume 50, n?5, 255-258
A 3-month-old diarrheic piglet was investigated. A massive infestation by Cryptosporidium parvum was diagnosed. However, lesions typical of PCV2 infection were observed and PCV2 infection was confirmed by immunohistochemistry. Unexpectedly, cytoplasmic inclusion bodies were detected in foci of histiocytic infiltrates in jejunum submucosa. In addition, a close association between histiocytic cells and eosinophils was observed. The virus was particularly abundant in the areas where parasites were more numerous. PCV2 is known to induce systemic lymphoid depletion and create an immunosuppression state. Therefore, PCV2 may have paved the way for C. parvum which is usually rare in post-weaning and growing pigs.

VLA SURVEILLANCE REPORT
PMWS diagnosed in farmed wild boar.
Veterinary Records, 2003, Volume 153, N?2, 39-42
PCV-2 infection was confirmed by immunohistochemistry in a four-month old wild boar piglet showing pallor associated with generalized lymph node enlargement and interstitial nephritis.

SEGALES J, CALSAMIGLIA M, DOMINGO M
Post-weaning multisystemic wasting syndrome (PMWS) and porcine circovirus type 2 infection in Spain.
Pig Journal, 2003, Volume 51, June, 98-107
In Spain, the first report of PMWS dates back to 1997. Since then, PMWS has been reported in most of the Spanish provinces and has become a major source of concern for swine practitioners. No infallible control measures have been found out so far.


Swine influenza

VAN REETH K, VAN GUCHT S, PENSAERT M
Investigations of the efficacy of European H1N1- and H3N2-based swine influenza vaccines against the novel H1N2 subtype.
Veterinary Records, 2003, Volume 153, N?1, 9-13
Two vaccinated groups and one control group of pigs were included in this study. Pigs of the two vaccinated groups were vaccinated twice, at four and eight weeks of age, group one with a H1N1/H3N2 vaccine (Gripovac?, Merial), group two with the same vaccine supplemented with an H1N2 component. All pigs were challenged with a H1N2 strain three weeks later. H1N1/H3N2 commercial vaccine did not prevent H1N2 virus replication but pigs from group one showed milder respiratory signs in comparison to control pigs. In contrast, pigs that were vaccinated with the H1N2-supplemented vaccine showed no respiratory signs and virus replication was not detected at 72 hours post-challenge. The investigated vaccine did not provided a sufficient protection against H1N2 subtype.


PORCINE RESPIRATORY DISEASE COMPLEX (PRDC)

DONE S, WHITE M
Porcine respiratory disease and complexes : the story to date.
In Practice, 2003, Volume 25, N?7, 410-414, 417
Respiratory diseases in pigs are not a novel issue that swine practitioners have to deal with. Clinical signs have not changed that much over the past decades, but new causal agents have been involved, new vaccines have been available and production methods have evolved. In the 80's, the major etiologic agents were bacteria (Pasteurella multocida, Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae, etc.). In the 90's, porcine reproductive and respiratory syndrome virus (PRRSV) emerged and together with swine influenza virus these new components of PRDC became major sources of concern. Subsequently, porcine circovirus type 2 (PCV2) made its entrance and is currently the most important troublemaker since, to date, no vaccine against PCV2 is available.


Dermatology

DONE SH, GUISE J, CHENNELLS DJ
Tail biting and tail docking in pigs.
Pig Journal, 2003, Volume 51, June, 136-154
Unexpectedly, tail biting has become a serious problem of pig production (bleeding, agitated animals, abscessation, paralysis). It was shown to be three times less frequent in docked pigs. This paper reports the results of anatomical and pathological studies.

BLOWEY R, DONE SH
Tail necrosis in pigs.
Pig Journal, 2003, Volume 51, June, 155-163
First sign of tail necrosis is slight erythema on the dorsal surface of the tail, slightly caudal to its base. Tail necrosis was demonstrated not to be linked to docking, use of tail clippers, holding the tail too tightly for docking, creep lamps nor indoor/outdoor management. The skin of newborn piglets is very delicate and results easily exposed to fecal/environmental contaminants even following mere abrasion. The application of iodine and glycerin to the tails soon after birth prevents tail necrosis.

Miscelleanous

WINDHORST HW
Asia's production dominance.
Pig Progress, 2003, Volume 19, N?4, 6-7
This paper reviews the current situation and perspectives of pig production in Asia. During the last two decades, a 217% increase of pig production was observed in Asia. Exports from Asian countries are low and represent only 3.8% of global exports. Conversely, imports play a more important role since they represent 23.8% of global trades. The Republic of Korea, Indonesia and China are predicted to have the highest growth rates regarding pig production by the end of a decade.

WINDHORST HW
Cost competitiveness of leading exporters.
Pig Progress, 2003, Volume 19, N?4, 8-11
How a country like Denmark which accounts for less than 2% of global pig meat production and has higher costs of production than those of Canada and the USA, can be the leading pig meat exporting country? Various factors are reviewed. The Danes take advantage of better feed conversion rates, higher daily gains, higher numbers of live piglets born per sow and finishers slaughtered per sow. However, the world market is about to experience great changes and the growing competition from Asian countries and Spain may modify the import/export situation.

MELLOR S
Problems of mycotoxins? and some solutions.
Pig Progress, 2003, Volume 19, N?5, 12-15
Mycotoxins are an important issue since contamination of feed and food leads to health problems and heavy financial losses. Dioxyvalenol (DON) and zearalenone (both produced by Fusarium spp.) are responsible for the most significant intoxications with mycotoxins (mycotoxicosis) in pigs. Mycotoxicosis caused by DON brings about vomiting or at least decreased feed intake, as well as a pro-inflammatory effect on the gastrointestinal tract that increases susceptibility to infection. Mycotoxicosis caused by zearalenone results in decreased productivity in sows and gilts due to estrogenic effects and altered semen quality. Early signs of zearalenone intoxication are discoloration and enlargement of the nipples and vulva. Other mycotoxins are reviewed: ochratoxin A (liver damage, immunosuppressive effect, decreased in the number of live piglets per sow and decreased litter size), fumonisins (cardiomyopathy and pleural edema). Physical, chemical and microbial techniques of detoxification are available. The use of mycotoxin binders (adsorption) or enzymes that degrade or transform mycotoxins are as many strategies for animal producers to reduce the risk of mycotoxicosis.

Parasitology

PETKEVICIUS S, KNUDSEN KEB, MURRELL KD, WACHMANN H.
The effect of inulin and sugar beet fibre on Oesophagostomum dentatum infection in pigs.
Parasitology : (London), 127: 61-68, 2003
The present study was designed to assess the role of inulin and sugar beet fibres (SBF) on adult O. dentatum in growing pigs. Four experimental diets were formulated based on barley Hour with added insoluble fibre from oat husk (Diet 1), a pure carbohydrate source inulin (Diet 2), soluble fibre from sugar beet fibre (SBF) with a high proportion of soluble fibre components (Diet 3) or inulin plus SBF (Diet 4). Thirty-two 10-week-old pigs were divided randomly into 4 groups each of 8 pigs. After 3 weeks adaptation o

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