VACCINOLOGY
• Les vaccins du futur.

HERD MANAGEMENT
• Incidence économique en production porcine de l'évolution des contraintes réglementaires relatives au bien-être animal

JOURNEE DE LA RECHERCHE PORCINE
• Etude de la transmission du Circovirus porcin de type 2 à partir de porcelets sevrés précocement et issus d’un élevage atteint de Maladie de l’Amaigrissement du Porcelet
• Etude de différentes modalités d’inoculation du circovirus porcin de type 2 (PCV2) à des truies EOPS

American Association of Swine Veterinarians, Annual Meeting March 2002, Kansas City
PRRS
• Effect of fetal PRRSV infection on the development of the porcine immune system.
• Transmission of PRRSV: recent research approach.
• Transmission of porcine reproductive and respiratory syndrome virus from persistently infected sow to contact controls.
• What do we know about PRRSV and replication is the pig?
• Assessing the duration of porcine reproductive and respiratory syndrome virus persistence and shedding in a large population of breeding age female swine.
• How does the body respond to PRRSV? (Immune response to PRRSV)
PMWS
• The role of circovirus in PMWS and PRDC: advances in understanding pathogenesis and control.
• Role of maternal immunity to PCV2 and PRRSV co-infection in the pathogenesis of PMWS.
• Reproduction of PMWS with an infectious molecular clone of PCV2.
Haemophilus parasuis
• Haemophilus parasuis: challenges and changes.
Staphylococci
• Staphylococcal Dermatitis and PDNS.
Miscellaneous
• Exceeding expectations.

Les vaccins du futur.
LECLERC C, MOINGEON P - INSTITUT PASTEUR
Biofutur 2001 : 82-86
The advent of ‘molecular’ vaccines is a great step forward in the development of new vaccination strategies. Research into purified antigens composing the vaccines is being carried out. With the use of the genomic sequencing of pathogenic agents and post-genomic study methods, it is now possible to identify and predict the molecules that are likely to be released by these pathogens or appear on their surface and trigger an immune response (cell-mediated). Hundreds of these antigenic molecules are thus produced and purified and will be the core elements of tomorrow’s vaccines. The improvement of vaccination also depends on the roles played by dendritic cells and mucosa in provoking immune responses. Therapeutic vaccination is newly associated with the preventive role of vaccination and will aim at controlling chronic infectious diseases.

Incidence économique en production porcine de l'évolution des contraintes réglementaires relatives au bien-être animal.
GOURMELEN C, SALAUN Y, ROUSSEAU P
Techni Porc 2001 24 : 5-12
Animal comfort and well-being are now taken into account in swine production. Experts from the Scientific Veterinary Committee suggested new recommendations on this matter, which are likely to form the basis of new European laws. These new suggestions mainly involve technical improvements on the farm such as a different type of sow containment (no more individual stall for pregnant sows), a greater surface allotted to each animal and a different type of floor (slatted floor replaced by solid floor or straw litter). The economical consequences expected from a new regulation enforcement are studied in this paper. In general the new measures on animal welfare entail significant extra financial costs for French swine producers.

Etude de la transmission du Circovirus porcin de type 2 à partir de porcelets sevrés précocement et issus d’un élevage atteint de Maladie de l’Amaigrissement du Porcelet
CARIOLET R, LE DIMNA M, BLANCHARD P, BENEVENT G, EVENO E, JESTIN A, MADEC F
Journées de la Recherche Porcine 2002, 34: 325-332
The piglets used in this trial were born in a herd severely affected by PMWS, they were weaned at 12 days of age, transferred to high-biosecurity facilities and distributed into two groups : piglets born of young sows and piglets born of multiparous sows. Following an observation period of 4 weeks, half of each group of piglets was placed in direct contact with SPF piglets while the other two halves were kept in pens adjacent to other SPF piglets (indirect contact). In this trial, only the piglets born of multiparous sows seem to have excreted the virus suggesting that the status of the sows should be taken into consideration when designing an eradication program. Moreover, the observations tend to show that direct contact between virus-excreting animals and naive animals is necessary for the disease to manifest severely.

Etude de différentes modalités d’inoculation du circovirus porcin de type 2 (PCV2) à des truies EOPS
CARIOLET R, BLANCHARD P, LE DIMNA M, TRUONG C, KERANFLEC’HA, BEAUREPAIRE B, JOLLY JP, JULOU P, DE BOISSESON C, MAHE D, MADEC F, JESTIN A
Journées de la Recherche Porcine 2002, 34: 317-323
Four SPF sows were inoculated with PCV2 by both the intratracheal route and intramuscular route (group 1) and six others by the intrauterine route at estrus (group 2). All aborted fetuses and piglets obtained in group 1 were PCV2 seronegative, suggesting that transplacental transmission does not occur which is in opposition with previous results obtained by Ladekjaer-Mikkelsen et al.. In group 2, reproductive failures were greatly influenced by the dose effect: the higher the titer the more significant the failures. The results obtained in this group of sows suggest that the second half of gestation is the period in which PCV2 achieves infection.

Effect of fetal PRRSV infection on the development of the porcine immune system.
LAGER KM, BUTLER JE
Proceeding of the American Association of Swine Veterinarians 2002: 299-300
In order to better understand how PRRSV may be transmitted within a herd, the following hypothesis was formulated: fetuses infected before being immunocompetent may develop an immunotolerant state to PRRSV. Six groups of fetuses were inoculated with wild-type PRRSV and 8 groups by an attenuated virus at 48/51 days of gestation. Their PRRSV antibody levels were examined. Control groups received a sham inoculum. It was confirmed that in wild-type PRRSV inoculated litters, fetuses became infected and died. Similarly, fetuses with attenuated PRRSV were alive but became seropositive, suggesting that an immunotolerant state in porcine fetuses following fetal infection with PRRSV is unlikely.

Transmission of PRRSV: recent research approach.
OTAKE S, DEE SA, ROSSOW KD, DEEN J, HANSOO J, MOLITOR TW, PIJOAN C
Proceeding of the American Association of Swine Veterinarians 2002: 349-356
Transmission of PRRSV by non-porcine vectors involving needles, fomites and personnel, aerosol and mosquitoes was studied. The following conclusions were derived from the studies conducted for each vector: contaminated needles following vaccination of infected pigs, fomites and hands of personnel associated with direct pig contact as well as mosquitoes play a potential role in PRRS transmission in pigs. However transmission was not or hardly observed when sanitation procedures were implemented for fomites and personnel and when aerosol as a potential vector was assessed.

Transmission of porcine reproductive and respiratory syndrome virus from persistently infected sow to contact controls.
DEE SA
Proceeding of the American Association of Swine Veterinarians 2002: 301
The persistence of PRRSV in sows and transmission of the virus from persistently infected sows were confirmed by a study involving 12 non pregnant sow infected with PRRSV (index sows) and brought into contact with naïve sows. The different post-infection tests (PCR) and observations showed that PRRSV was detected in all 12 index sows over a period of 72 to 86 days post infection and that infectious virus was isolated in 3 contact sows.

What do we know about PRRSV and replication is the pig?
BENFIELD DA
Proceeding of the American Association of Swine Veterinarians 2002: 353-356
PRRS is presented as a four-stage disease (in utero infection, acute infection, asymptomatic infection and clearance) and virus replication is observed during the first three stages, suggesting that the virus is persistent in pigs over a long period of time. It has been shown that PRRSV mainly resides in tonsil and lymph nodes, with macrophages as the favorite target cells for its replication.

Assessing the duration of porcine reproductive and respiratory syndrome virus persistence and shedding in a large population of breeding age female swine.
BATISTA L, DEE SA, ROSSOW KD, DEEN J, PIJOAN C
Proceeding of the American Association of Swine Veterinarians 2002: 357-359
Persistent infection was previously reported in experimentally PRRS infected pigs but needed to be studied on a large scale in a large population of breeding age gilts. One hundred and fifty PRRS naïve gilts were intranasally inoculated with a field isolate of PRRS and tested for presence of virus at 120, 150 and 180 days post-infection (slaughter times). Shedding of virus from PRRS positive gilts was assessed with the introduction of 30 PRRSV naïve sentinel gilts.

How does the body respond to PRRSV? (Immune response to PRRSV)
OSORIO FA
Proceeding of the American Association of Swine Veterinarians 2002: 361-366
Both humoral (PRRSV antibodies) and cell (T-cells) mediated immune responses have been identified in PRRSV-infected pigs and are characterized by an unusual delay in responsiveness. However, there is conflicting data on the actual protective role of antibodies against infection. Passive transfer of PRRSV-neutralizing immunoglobulins (Igs) in pregnant females with no known reproductive failure was thus conducted and the protection of pregnant females from reproductive disease with clearance of the virus and absence of viremia in dams and offspring were confirmed. Theses findings provide strong evidence of a protective immunity conferred by Igs. However, further investigation is needed to understand the causes of this delayed protective immunity.

The role of circovirus in PMWS and PRDC: advances in understanding pathogenesis and control.
SORDEN SD, HALBUR PG
Proceeding of the American Association of Swine Veterinarians 2002: 265-268
A review of the current knowledge on PCV2/PMWS in relation to PDRC (Porcine respiratory disease complex) was conducted at the Iowa State University Veterinary Diagnostic Laboratory (ISU-VDL), based on the university own experience and on international literature. At ISU-VDL, PMWS was found to be frequently associated with the PRDC complex as pneumonia is often observed with PMWS cases. PCV2 infection, which is consistently associated with PMWS, has also been demonstrated in PRDC cases. A review of the current literature emphasizes the importance of dual infection (PCV2 with PRRSV or PPV) in the development of clinical PMWS. Such herd management strategies as AIAO (all in all out), pig flow changes, vaccination or change in pig sources have been put forward to prevent PMWS but further investigation is needed to answer a series of pending questions: relation of PCV2 strains to virulence and tissue tropism, different PCV2 situations among countries, factors causing the progression of PCV2 infection to PMWS.

Role of maternal immunity to PCV2 and PRRSV co-infection in the pathogenesis of PMWS.
HARMS PA, SORDEN SD, HALBUR PG, NAWAGITGAL P, LAGER K, BOLIN S, PAUL PS
Proceeding of the American Association of Swine Veterinarians 2002: 307-312
Based on the observation that only 5 to 15% of pigs are affected by PRRS, a study was conducted to provide evidence of the protective role of maternally-derived antibodies to PCV2 in pigs likely to develop PMWS. Colostrum-fed pigs were removed from seropositive sows and inoculated with PCV2, PCV2+PRRSV or sham-inoculated at 3 to 10 weeks of age and then necropsied at 7, 14, 21, 28 days post infection. PCV2 antibody levels at inoculation were recorded using the ELISA technique (S/P ratios). Clinical signs and lesions were also scored. It was concluded that passive antibodies to PCV2 offered protection as pigs with S/P ratios above 0.6 had no PMWS lesions, with one exception. Additionally, dually infected pigs showed greater lesions thereby highlighting the role of concurrent infection in the severity of the disease. However, other factors than low S/P ratios need to be considered to understand how the disease develops.

Reproduction of PMWS with an infectious molecular clone of PCV2.
HALBUR P, FENAUX M, HAQSHENAS T, TOTH T, MENG X-J
Proceeding of the American Association of Swine Veterinarians 2002: 313-314
Following previous experiences of PMWS lesions reproduced from intranasal inoculation of PCV2, of dual inoculation (PCV2-PPV), or inoculation of cell culture from PMWS-infected pig, the authors used a DNA cloned model of PCV2 for the inoculation of 3 groups of early weaned pigs and observed similar results: the development of lesions typical of PMWS confirmed PCV2 as a causative agent of PMWS and concurrent infection may be needed to induce all clinical signs and lesions of PMWS. They also stressed the utility of a molecular clone of PCV2 to study viral replication.

Haemophilus parasuis

Haemophilus parasuis: challenges and changes.
PIJOAN C, OLIVEIRA S
Proceeding of the American Association of Swine Veterinarians 2002: 251-253
To understand what may be the different colonization patterns of Haemophilus parasuis, a study of field isolates and an experimental infection in 5 pigs were performed. PCR analysis of isolates revealed the existence of homologous virulent strains associated with a late colonization, mostly after weaning, and heterogeneous low virulent strains associated with early colonization. The experimental infection at pre-weaning stage with a virulent strain showed that high levels of colonization resulted in less clinical disease in pigs.

Staphylococci

Staphylococcal Dermatitis and PDNS.
CLARK T
Proceeding of the American Association of Swine Veterinarians 2002: 269-270
Staphylococcal dermatitis may be caused by Staphilococcus aureus or S. hyicus. The former is observed in pustular dermatitis and some visceral disease while the latter is the causative agent of exudative epidermatitis (EE), a disease with worldwide distribution in young pigs (<1week). The author’s aim is to draw attention on a more localized form of S. hyicus dermatitis observed from a herd during 7 years and characterized by multifocal pododermatitis with bacteremia and joint inflammations. It may pose a serious threat to herds because of its rapid onset and progression. Also, there is little information available on its causes and so far management practices (improved sanitation or all in all out) have been unsuccessful in solving the problem.
Another emerging disease, PDNS (porcine dermatopathy and nephropathy syndrome) causing vasculitis of kidneys and skin should also be considered. Co-occurrence of PDNS and PMWS is frequent. Although evidence of PCV2 involvement in PDNS has been provided, the etiology of the vascular lesions is yet to be discovered.

Miscellaneous

Exceeding expectations.
BLACKWELL TE
Proceeding of the American Association of Swine Veterinarians 2002: 9-18
This paper addresses various reflections on the swine veterinary profession and the commitment of veterinarians to exceed expectations placed upon them. As experts in animal welfare and animal agriculture, veterinarians have to face a number of responsibilities and strike a balance between several conflicting interests. Veterinarians are expected to be fully responsible for the livestock medicines prescribed and for a review of medication usage on a farm. They are also leaders in animal welfare discussions to ensure the welfare of sick, injured animals and these discussions should be considered within an ethical framework. The collaborative work of independent owner-operator of swine farms to devise solutions to the never-ending problems of swine production should be set as an example for veterinarians. In order to make continual progress, veterinarians should access current information on the veterinary practice but also share their knowledge and practical experience with their peers in the form of informal ‘hallway-style’ meetings to learn how to apply this knowledge and this experience to their work.