Demographic survey of private veterinary practices in western Canada.

A workforce survey of private veterinary practices in western Canada was conducted in 2020. Data were obtained on 526 practices (response rate = 39.5%) and 1445 individual veterinary practitioners. Overall, 68.4% of practitioners identified as female, with 4 times as many females as males comprising the youngest age cohorts (26 to 35 y) of the profession. The majority of practices (67.9%) were companion animal, followed by mixed animal (21.9%) and food animal (10.2%). Most females (77.2%) and males (57.8%) were engaged in companion animal practice, whereas 23.5% of males and 6.0% of females were food animal practitioners. During an average work week, practitioners devoted 77.4% of practice time to small animals, 15.1% to food animals, and 7.5% to equine animals. A greater proportion of males (75.2%) versus females (63.2%) worked on a full-time equivalent basis (P < 0.001). Whereas males were 1.7 times (95% CI = 1.3 to 2.3; P < 0.001) more likely to be practice owners than females, 54.5% of females were owners. Practice ownership was lower than in previous surveys, a trend that may have long-term implications with respect to the corporatization of the veterinary profession.

Enquête démographique sur les cabinets vétérinaires privés dans l'Ouest canadien. Une enquête sur la main-d'oeuvre des cabinets vétérinaires privés dans l'Ouest canadien a été menée en 2020. Des données ont été obtenues sur 526 cabinets (taux de réponse = 39,5 %) et 1445 praticiens vétérinaires individuels. Dans l'ensemble, 68,4 % des praticiens se sont identifiés comme des femmes, avec quatre fois plus de femmes que d'hommes parmi les cohortes d'âge les plus jeunes (26 à 35 ans) de la profession. La majorité des pratiques (67,9 %) étaient chez les animaux de compagnie, suivis des pratiques mixtes (21,9 %) et chez les animaux de rente (10,2 %). La plupart des femmes (77,2 %) et des hommes (57,8 %) travaillaient en pratique des animaux de compagnie, tandis que 23,5 % des hommes et 6,0 % des femmes étaient en pratique des animaux de rente. Au cours d'une semaine de travail moyenne, les praticiens ont consacré 77,4 % de leur temps de pratique aux petits animaux, 15,1 % aux animaux de rente et 7,5 % aux équidés. Une plus grande proportion d'hommes (75,2 %) que de femmes (63,2 %) travaillaient en équivalent temps plein (P < 0,001). Alors que les hommes étaient 1,7 fois (IC à 95 % = 1,3 à 2,3; P < 0,001) plus susceptibles d'être propriétaires d'un cabinet que les femmes, 54,5 % des femmes étaient propriétaires. La propriété de la pratique était plus faible que dans les enquêtes précédentes, une tendance qui peut avoir des implications à long terme en ce qui concerne la corporisation de la profession vétérinaire.(Traduit par Dr Serge Messier).

Hiring intentions and remuneration of veterinary practitioners in western Canada.

All private veterinary practices in western Canada (N = 1333) were surveyed during the SARS-CoV-2 pandemic (January to November 2020) to generate data on the demographics of the profession, and to quantify past and present hiring intentions (demand) as well as remuneration for veterinary associates. The response rate was 39.5% (526/1333), 186 of which had hired at least one full- (FT) or part-time (PT) associate within the 12-month period preceding the completion of the survey. When extrapolated to the practices that did not respond (nonresponders), as many as 471 practices may have hired an associate within the previous 12 mo. The median (mean) annual remuneration paid to FT associates was $90 000 ($91 730). The median number of months it took to hire an associate did not vary by province (P = 0.52); however, it did vary by practice type (P <0.0001): companion animal practice, 3.0 mo; food animal practice, 8.0 mo; and mixed animal practice, 12.0 mo. At the time of the survey, 232 of the 526 (44.1%) responding practices were currently seeking to fill 281 vacancies, representing 274 full-time equivalents (FTE). If extrapolated to the nonresponders, the total number of vacant FTE positions could have been as high as 694. The median (mean) annual wage offered for a FT associate was $87 500 ($88 940), which did not differ by province (P = 0.14) or practice type (P = 0.22). The results of this study support anecdotal reports of a shortage of private veterinary practitioners in western Canada.

Intentions d'embauche et rémunération des vétérinaires praticiens dans l'Ouest canadien. Tous les cabinets vétérinaires privés de l'Ouest canadien (N = 1333) ont été interrogés pendant la pandémie de SARS-CoV-2 (janvier à novembre 2020) afin de générer des données sur la démographie de la profession et de quantifier les intentions d'embauche passées et présentes (demande) ainsi que rémunération des associés vétérinaires. Le taux de réponse était de 39,5 % (526/1333), dont 186 avaient embauché au moins un associé à temps plein (FT) ou à temps partiel (PT) au cours de la période de 12 mois précédant la fin de l'enquête. Lorsqu'ils sont extrapolés aux pratiques qui n'ont pas répondu (non-répondants), jusqu'à 471 pratiques peuvent avoir embauché un associé au cours des 12 derniers mois. La rémunération annuelle médiane (moyenne) versée aux associés de FT était de 90 000 $ (91 730 $). Le nombre de mois qu'il a fallu pour embaucher un associé ne variait pas selon la province (P = 0,52); cependant, elle variait selon le type de pratique (P <0,0001) : pratique des animaux de compagnie, 3,0 mois; pratique des animaux destinés à l'alimentation, 8,0 mois; et pratique animale mixte, 12,0 mois. Au moment de l'enquête, 232 des 526 cabinets répondants (44,1 %) cherchaient actuellement à pourvoir 281 postes vacants, représentant 274 équivalents temps plein (ETP). Si extrapolé aux non-répondants, le nombre total de postes vacants en ETP aurait pu atteindre 694. Le salaire annuel médian (moyen) offert pour un associé à temps plein était de 87 500 $ (88 940 $), ce qui ne différait pas selon la province (P = 0,14) ou type de pratique (P = 0,22). Les résultats de cette étude appuient les rapports anecdotiques d'une pénurie de vétérinaires praticiens privés dans l'Ouest canadien.(Traduit par Dr Serge Messier).

Depletion of pulmonary intravascular macrophages rescues inflammation-induced delayed neutrophil apoptosis in horses.

The objective of this study was to determine the effect of pulmonary intravascular macrophage depletion on systemic inflammation and ex vivo neutrophil apoptosis using an experimental model of intestinal ischemia and reperfusion injury in horses. Neutrophils were isolated before and after surgery from horses that were randomized to three treatment groups, namely, sham celiotomy (CEL, n = 4), intestinal ischemia and reperfusion (IR, n = 6), and intestinal ischemia and reperfusion with gadolinium chloride treatment to deplete pulmonary intravascular macrophages (PIMs, IRGC, n = 6). Neutrophil apoptosis was assessed with Annexin V and propidium iodide staining quantified with flow cytometry and caspase-3, caspase-8, and caspase-9 activities in neutrophil lysates. All horses experienced a systemic inflammatory response following surgery. Following surgery, ex vivo neutrophil apoptosis was significantly delayed after 12 or 24 h in culture, except in IRGC horses (12 h: CEL: P = 0.03, IR: P = 0.05, IRGC: P = 0.2; 24 h: CEL: P = 0.001, IR: P = 0.004, IRGC: P = 0.3). Caspase-3, caspase-8, and caspase-9 activities were significantly reduced in neutrophils isolated after surgery and cultured for 12 h in IR horses, but not in IRGC horses (IR caspase-3: P = 0.002, IR caspase-8: P = 0.002, IR caspase-9: P = 0.04). Serum TNF-α concentration was increased in IRGC horses for 6-18 h following jejunal ischemia. Following surgery, ex vivo equine neutrophil apoptosis was delayed via downregulation of caspase activity, which was ameliorated by PIM depletion potentially via upregulation of TNF-α.

Bistable expression of CsgD in Salmonella enterica serovar Typhimurium connects virulence to persistence.

Pathogenic bacteria often need to survive in the host and the environment, and it is not well understood how cells transition between these equally challenging situations. For the human and animal pathogen Salmonella enterica serovar Typhimurium, biofilm formation is correlated with persistence outside a host, but the connection to virulence is unknown. In this study, we analyzed multicellular-aggregate and planktonic-cell subpopulations that coexist when S. Typhimurium is grown under biofilm-inducing conditions. These cell types arise due to bistable expression of CsgD, the central biofilm regulator. Despite being exposed to the same stresses, the two cell subpopulations had 1,856 genes that were differentially expressed, as determined by transcriptome sequencing (RNA-seq). Aggregated cells displayed the characteristic gene expression of biofilms, whereas planktonic cells had enhanced expression of numerous virulence genes. Increased type three secretion synthesis in planktonic cells correlated with enhanced invasion of a human intestinal cell line and significantly increased virulence in mice compared to the aggregates. However, when the same groups of cells were exposed to desiccation, the aggregates survived better, and the competitive advantage of planktonic cells was lost. We hypothesize that CsgD-based differentiation is a form of bet hedging, with single cells primed for host cell invasion and aggregated cells adapted for persistence in the environment. This allows S. Typhimurium to spread the risks of transmission and ensures a smooth transition between the host and the environment.

B-cell activating factor (BAFF) promotes CpG ODN-induced B cell activation and proliferation.

It is controversial whether naïve B cells are directly activated in response to TLR9 ligand, CpG ODN. Although bovine blood-derived CD21(+) B cells express TLR9 and proliferate in response to CpG in mixed-cell populations, purified bovine B cells do not proliferate significantly in response to CpG ODN, even when the B cell receptor is engaged. When co-cultured with CD14(+) myeloid cells and/or B-cell activating factor (BAFF), a cytokine produced by activated myeloid cells, there was a significant increase in CpG-specific B cell proliferation, and the number of large B cells in general or positive for CD25, all of which are markers for B cell activation. These data suggest that activated myeloid cells and BAFF prime B cells for significant CpG-specific activation. Understanding the signals required to mediate efficient CpG-induced, antigen-independent and T-cell independent activation of B cells has implications for polyclonal B cell activation and the development of autoimmune diseases.

Genes coding for virulence determinants of Campylobacter jejuni in human clinical and cattle isolates from Alberta, Canada, and their potential role in colonization of poultry.

Forty nine Campylobacter jejuni isolates from cattle feces collected from Alberta feedlots and 50 clinical C. jejuni isolates from people in Alberta were tested for the presence of 14 genes encoding putative virulence factors by PCR. These included genes implicated in adherence and colonization (flaC, cadF, docC, racR, jlpA, peb1, and dnaJ), invasion (virB11, ciaB, pldA, and iamA) and protection against harsh conditions (htrA, cbrA, and sodB). The genes examined were widely distributed in both the cattle fecal isolates and the human isolates. Of the isolates tested, 67% contained all of the genes except virB11. The cadF gene was found in 100% of the isolates tested. The presence or absence of virulence-associated genes was not associated with the ability of the organism to colonize birds. All of the C. jejuni isolates used to challenge birds were able to colonize the animals regardless of virulence gene profile. While some diversity in the profile of the occurrence of virulence-associated genes in C. jejuni exists, the distribution of these putative virulence-associated genes isolates from feedlot cattle feces and humans in Alberta was similar. In addition it was not possible to predict the ability of the selected isolates to colonize young chicks based on the presence of these genes coding for virulence determinants.

Epidemiology of equine sarcoids in horses in western Canada.

Sarcoids are the most common tumor of the equine skin but only 1 study describing the epidemiology of sarcoids in Canadian horses has been published. The records of 5 veterinary diagnostic laboratories in western Canada were searched to identify submissions of sarcoids from horses. The submission records and diagnostic reports of 802 separate submissions of equine sarcoids were reviewed for age, breed, and gender of the horse and the number, location, and clinical type of sarcoid. From these records, the 307 submissions to laboratories in Saskatchewan were compared to a reference group to test for breed and gender predisposition. Based on clinical history and lesion descriptions, 5 clinical types of sarcoids were identified. Horses of various ages and 23 equine breeds were affected; donkeys were over-represented. Polymerase chain reaction (PCR) for the bovine papillomavirus (BPV) DNA was performed on formalin-fixed paraffin-embedded tissues from a stratified subset of 96 of the different clinical types; BPV2 was present in 60 of 74 (81%) for which a PCR product was obtained. Unlike other areas in the world, in western Canada, equine sarcoids are most commonly associated with BPV type 2.

Regional Dichotomy in Enteric Mucosal Immune Responses to a Persistent Mycobacterium avium ssp. paratuberculosis Infection.

Chronic enteric Mycobacterium avium ssp. paratuberculosis (MAP) infections are endemic in ruminants globally resulting in significant production losses. The mucosal immune responses occurring at the site of infection, specifically in Peyer's patches (PP), are not well-understood. The ruminant small intestine possesses two functionally distinct PPs. Discrete PPs function as mucosal immune induction sites and a single continuous PP, in the terminal small intestine, functions as a primary lymphoid tissue for B cell repertoire diversification. We investigated whether MAP infection of discrete vs. continuous PPs resulted in the induction of significantly different pathogen-specific immune responses and persistence of MAP infection. Surgically isolated intestinal segments in neonatal calves were used to target MAP infection to individual PPs. At 12 months post-infection, MAP persisted in continuous PP (n = 4), but was significantly reduced (p = 0.046) in discrete PP (n = 5). RNA-seq analysis revealed control of MAP infection in discrete PP was associated with extensive transcriptomic changes (1,707 differentially expressed genes) but MAP persistent in continuous PP elicited few host responses (4 differentially expressed genes). Cytokine gene expression in tissue and MAP-specific recall responses by mucosal immune cells isolated from PP, lamina propria and mesenteric lymph node revealed interleukin (IL)22 and IL27 as unique correlates of protection associated with decreased MAP infection in discrete PP. This study provides the first description of mucosal immune responses occurring in bovine discrete jejunal PPs and reveals that a significant reduction in MAP infection is associated with specific cytokine responses. Conversely, MAP infection persists in the continuous ileal PP with minimal perturbation of host immune responses. These data reveal a marked dichotomy in host-MAP interactions within the two functionally distinct PPs of the small intestine and identifies mucosal immune responses associated with the control of a mycobacterial infection in the natural host.

A Bovine Enteric Mycobacterium Infection Model to Analyze Parenteral Vaccine-Induced Mucosal Immunity and Accelerate Vaccine Discovery.

Mycobacterial diseases of cattle are responsible for considerable production losses worldwide. In addition to their importance in animals, these infections offer a nuanced approach to understanding persistent mycobacterial infection in native host species. Mycobacteriumavium ssp. paratuberculosis (MAP) is an enteric pathogen that establishes a persistent, asymptomatic infection in the small intestine. Difficulty in reproducing infection in surrogate animal models and limited understanding of mucosal immune responses that control enteric infection in the natural host have been major barriers to MAP vaccine development. We previously developed a reproducible challenge model to establish a consistent MAP infection using surgically isolated intestinal segments prepared in neonatal calves. In the current study, we evaluated whether intestinal segments could be used to screen parenteral vaccines that alter mucosal immune responses to MAP infection. Using Silirum® - a commercial MAP bacterin - we demonstrate that intestinal segments provide a platform for assessing vaccine efficacy within a relatively rapid period of 28 days post-infection. Significant differences between vaccinates and non-vaccinates could be detected using quantitative metrics including bacterial burden in intestinal tissue, MAP shedding into the intestinal lumen, and vaccine-induced mucosal immune responses. Comparing vaccine-induced responses in mucosal leukocytes isolated from the site of enteric infection versus blood leukocytes revealed substantial inconsistences between these immune compartments. Moreover, parenteral vaccination with Silirum did not induce equal levels of protection throughout the small intestine. Significant control of MAP infection was observed in the continuous but not the discrete Peyer's patches. Analysis of these regional mucosal immune responses revealed novel correlates of immune protection associated with reduced infection that included an increased frequency of CD335+ innate lymphoid cells, and increased expression of IL21 and IL27. Thus, intestinal segments provide a novel model to accelerate vaccine screening and discovery by testing vaccines directly in the natural host and provides a unique opportunity to interrogate mucosal immune responses to mycobacterial infections.

Salmonella enterica serovar enteritidis pathogenicity island 1 is not essential for but facilitates rapid systemic spread in chickens.

Salmonella enterica subsp. enterica serovar Enteritidis is a leading cause of human food-borne illness that is mainly associated with the consumption of contaminated poultry meat and eggs. To cause infection, S. Enteritidis is known to use two type III secretion systems, which are encoded on two salmonella pathogenicity islands, SPI-1 and SPI-2, the first of which is thought to play a major role in invasion and bacterial uptake. In order to study the role of SPI-1 in the colonization of chicken, we constructed deletion mutants affecting the complete SPI-1 region (40 kb) and the invG gene. Both DeltaSPI-1 and DeltainvG mutant strains were impaired in the secretion of SipD, a SPI-1 effector protein. In vitro analysis using polarized human intestinal epithelial cells (Caco-2) revealed that both mutant strains were less invasive than the wild-type strain. A similar observation was made when chicken cecal and small intestinal explants were coinfected with the wild-type and DeltaSPI-1 mutant strains. Oral challenge of 1-week-old chicken with the wild-type or DeltaSPI-1 strains demonstrated that there was no difference in chicken cecal colonization. However, systemic infection of the liver and spleen was delayed in birds that were challenged with the DeltaSPI-1 strain. These data demonstrate that SPI-1 facilitates systemic infection but is not essential for invasion and systemic spread of the organism in chickens.

Genomics-based molecular epidemiology of Campylobacter jejuni isolates from feedlot cattle and from people in Alberta, Canada.

Feedlot cattle in Alberta, Canada, have been identified as reservoirs for Campylobacter jejuni, an important human pathogen. Oligonucleotide DNA microarrays were used as a platform to compare C. jejuni isolates from feedlot cattle and human clinical cases from Alberta. Comparative genomic hybridization (CGH) analysis was performed on 87 isolates (46 bovine, 41 human) obtained within the same geographical regions and time frame. Thirteen CGH clusters were obtained based on overall comparative genomic profile similarity. Nine CGH clusters contained human and cattle isolates, three contained only human isolates, and one contained only cattle isolates. The study isolates clustered regardless of temporal or geographical frameworks. In addition, array genes (n = 1,399) were investigated on a gene-by-gene basis to see if any were unequally distributed between human and cattle sources or between clusters dominated by either human or cattle isolates ("human enriched" versus "cattle enriched"). Using Fisher's exact test with the Westfall and Young correction for these comparisons, a small number of differentially distributed genes were identified. Our findings suggest that feedlot cattle and human C. jejuni strains are very similar and may be endemic within Alberta. Further, the common distribution of human clinical and bovine C. jejuni isolates within the same genetically based clusters suggests that dynamic and important transmission routes between cattle and human populations may exist.

Role of toll-like receptor 4 and caspase-3, -8, and -9 in lipopolysaccharide-induced delay of apoptosis in equine neutrophils.

OBJECTIVE To evaluate the effect of lipopolysaccharide (LPS) on apoptosis of equine neutrophils in vitro. SAMPLE Venous blood samples from 40 adult horses. PROCEDURES Neutrophils were isolated from blood samples and cultured with or without LPS from Escherichia coli O55:B5 for 12 or 24 hours. Neutrophil apoptosis was assessed by use of cytologic examination, annexin V and propidium iodide staining quantified with flow cytometry, coincubation with inducers of intrinsic and extrinsic apoptosis or a toll-like receptor (TLR) 4 inhibitor, and measurement of caspase-3, -8, and -9 activities. RESULTS Treatment with LPS resulted in a significant delay in apoptosis after incubation for 12 and 24 hours (neutrophils from blood samples of 40 horses). There was a significant correlation between increases in LPS dose and decreases in apoptosis after incubation for 24 hours (3 experiments, each of which involved neutrophils obtained from the same 3 horses at 3 separate times). Caspase-9 activity, but not caspase-3 or -8 activity, was significantly reduced in LPS-treated neutrophils after incubation for 12 hours (neutrophils from blood samples of 17 horses). Treatment with a TLR4 inhibitor or intrinsic and extrinsic inducers of apoptosis prevented LPS-delayed apoptosis. CONCLUSIONS AND CLINICAL RELEVANCE LPS treatment delayed apoptosis of equine neutrophils in vitro for up to 24 hours in a dose-dependent manner by alteration of the intrinsic pathway of apoptosis and was dependent on TLR4 signaling. Increased neutrophil life span may contribute to the development of a systemic inflammatory response syndrome in endotoxemic horses.

Systemic innate immune responses following intrapulmonary delivery of CpG oligodeoxynucleotides in sheep.

Mucosal delivery of CpG oligodeoxynucleotide (ODN) in mice has been shown to induce potent innate immunostimulatory responses and protection against infection. We evaluated the efficacy of CpG ODN in stimulating systemic innate immune responses in sheep following delivery to the pulmonary mucosa. Intrapulmonary (IPM) administration of B-Class CpG ODN in saline induced transient systemic responses which included increased rectal temperatures, elevated serum 2'5'-A synthetase and haptoglobin concentrations. The ODN dose required to induce detectable systemic responses following IPM delivery could be reduced by approximately 80% if the CpG ODN was administered in 30% emulsigen instead of saline. Intrapulmonary B-Class CpG ODN formulated in 30% emulsigen produced similar effects when compared to those seen following SC injection. These responses were CpG ODN-specific since control GpC ODN did not induce any detectable response. Intrapulmonary administration of both B-Class and the newly described C-Class CpG ODN produced similar effects indicating that both classes of CpG ODN were comparably effective in stimulating innate immune system following mucosal delivery. Administration of CpG ODN directly into the lungs or delivery of CpG ODN via an intratracheal (IT) infusion also produced similar systemic responses. These observations support the conclusion that mucosal delivery of CpG ODN is an effective route for induction of systemic acute phase responses and antiviral effector molecules in large animals, and may be helpful in controlling systemic infections.

Seroprevalence and risk factors for infection with West Nile virus in Saskatchewan horses, 2003.

The primary objectives of this study were to determine the seroprevalence of West Nile virus (WNV) infection of horses in Saskatchewan in 2003 and to identify risk factors for the infection. Blood samples were collected in August and October from 212 horses in 20 herds in 5 geographic zones. After accounting for within-herd clustering, the proportion of horses that had been infected with WNV, as determined by IgG and IgM antibody response, was 55.7% (95% confidence interval, 44.9% to 65.8%). The proportion of antibody-positive horses differed among herds (0% to 100%) and across ecoregions (20% to 76%). Horses in southern ecoregions were more likely to have either IgM antibodies or IgG concentrations suggesting infection than were horses in northern ecoregions. The use of mosquito-control measures was associated with decreased risk. After accounting for ecoregion, there was no difference between recipients of an inactivated WNV vaccine and nonrecipients in the occurrence of antibodies reflecting natural infection.

Stimulation of innate immune responses by CpG oligodeoxynucleotide in newborn lambs can reduce bovine herpesvirus-1 shedding.

Stimulation of the innate immune system is potentially very important in neonates who have an immature adaptive immune system and vaccination cannot be used to reduce the risk of infection. CpG oligodeoxynucleotide (ODN) can stimulate innate immune responses in newborn chickens and mice, but similar studies are lacking in other mammalian species. We have shown previously that CpG ODN can both stimulate an acute-phase immune response and induce the antiviral effector molecule, 2'5'-A synthetase, in adult sheep. Therefore, the immunostimulatory activity of A class and B class CpG ODN was evaluated in newborn lambs, and the capacity of CpG ODN-induced responses to reduce viral shedding was evaluated following aerosol challenge with the respiratory pathogen, bovine herpesvirus-1 (BHV-1). In vitro CpG ODN stimulation of peripheral blood mononuclear cells (PBMC) isolated from newborn lambs (3-5 days old) and adult sheep induced equivalent CpG-specific proliferative responses and interferon-alpha (IFN-alpha) secretion. CpG ODN-induced IFN-alpha secretion by neonatal PBMCs was, however, significantly (p < 0.01) enhanced 6 days after subcutaneous (s.c.) injection of 100 microg/kg CpG ODN 2007. Newborn lambs injected s.c. with B class CpG ODN 2007 or the inverted GpC control ODN formulated in 30% Emulsigen (MVP Laboratories, Ralston, NE) displayed CpG ODN-specific increases in body temperature (p < 0.0001), serum 2'5'-A synthetase activity (p = 0.0015), and serum haptoglobin (p = 0.07). CpG ODN-treated lambs also displayed a transient reduction in viral shedding on day 2 postinfection (p < 0.05), which correlated (p < 0.03) with serum 2'5'-A synthetase levels on the day of viral challenge. These observations confirmed that CpG ODNs effectively activate innate immune responses in newborn lambs and CpG ODN-induced antiviral responses correlated with a reduction in viral shedding.

The equine immune response to equine herpesvirus-1: the virus and its vaccines.

Equine herpesvirus-1 (EHV-1) is an alphaherpesvirus which infects horses, causing respiratory and neurological disease and abortion in pregnant mares. Latency is established in trigeminal ganglia and lymphocytes. Immunity to EHV-1 lasts between 3 and 6 months. Current vaccines, many of which contain inactivated virus, have reduced the incidence of abortion storms in pregnant mares but individual animals, which may be of high commercial value, remain susceptible to infection. The development of effective vaccines which stimulate both humoral and cellular immune responses remains a priority. Utilising data generated following experimental and field infections of the target species, this review describes the immunopathogenesis of EHV-1 and the interaction between the horse's immune system and this virus, both in vivo and in vitro, and identifies immune responses, highlighting those which have been associated with protective immunity. It then goes on to recount a brief history of vaccination, outlines factors likely to influence the outcome of vaccine administration and describes the immune response stimulated by a selection of commercial and experimental vaccines. Finally, based on the available data, a rational strategy designed to stimulate protective immune responses by vaccination is outlined.

Immune responses to commercial equine vaccines against equine herpesvirus-1, equine influenza virus, eastern equine encephalomyelitis, and tetanus.

Horses are commonly vaccinated to protect against pathogens which are responsible for diseases which are endemic within the general horse population, such as equine influenza virus (EIV) and equine herpesvirus-1 (EHV-1), and against a variety of diseases which are less common but which lead to greater morbidity and mortality, such as eastern equine encephalomyelitis virus (EEE) and tetanus. This study consisted of two trials which investigated the antigenicity of commercially available vaccines licensed in the USA to protect against EIV, EHV-1 respiratory disease, EHV-1 abortion, EEE and tetanus in horses. Trial I was conducted to compare serological responses to vaccines produced by three manufacturers against EIV, EHV-1 (respiratory disease), EEE, and tetanus given as multivalent preparations or as multiple vaccine courses. Trial II compared vaccines from two manufacturers licensed to protect against EHV-1 abortion, and measured EHV-1-specific interferon-gamma (IFN-gamma) mRNA production in addition to serological evidence of antigenicity. In Trial I significant differences were found between the antigenicity of different commercial vaccines that should be considered in product selection. It was difficult to identify vaccines that generate significant immune responses to respiratory viruses. The most dramatic differences in vaccine performance occurred in the case of the tetanus antigen. In Trial II both vaccines generated significant antibody responses and showed evidence of EHV-1-specific IFN-gamma mRNA responses. Overall there were wide variations in vaccine response, and the vaccines with the best responses were not produced by a single manufacturer. Differences in vaccine performance may have resulted from differences in antigen load and adjuvant formulation.

Expression of TECK/CCL25 and MEC/CCL28 chemokines and their respective receptors CCR9 and CCR10 in porcine mucosal tissues.

CCL25 and CCL28 (also named TECK and MEC) are CC chemokines primarily expressed by thymic dendritic cells and mucosal epithelial cells. The cognate receptors of CCL25 and CCL28, named CCR9 and CCR10, are mainly expressed on T lymphocytes for CCR9 and IgA(+) and IgM(+) plasmablasts for CCR9 and CCR10, respectively. In human and mouse, chemokines CCL25 and CCL28 play an important role in attracting immune cells to the gastrointestinal tract and in controlling segmental specialization of the intestinal immune system. To investigate if CCL25 and CCL28 play a similar role in the pig and to better understand lymphocyte trafficking in this species, we cloned porcine CCL25 and CCR10 and measured expression of CCL25, CCL28, CCR9, and CCR10 transcripts by real-time and conventional PCR in various tissues from newborn and young piglets, and adult sows. The results of the expression analyses show that (i) expression of CCL25 mRNA is mainly restricted to the small intestine, (ii) CCL28 mRNA expression is detectable in all tested epithelial mucosal surfaces with the highest levels of expression in the mammary gland, trachea and large intestine, (iii) high levels of expression of CCR9 mRNA in CD3+ T lymphocytes, gut-associated lymphoid tissues (GALT), and the small intestine, (iv) high levels of expression of CCR10 mRNA in GALT, the large intestine, the small intestine, and the mammary gland, and (v) up-regulation of CCL28 mRNA expression during lactation in the mammary gland. This pattern of expression, which is discussed in the context of compartmentalization of the porcine common mucosal immune system into upper aero-digestive tract, small intestine and large intestine, suggests a key role for CCL28 in the recruitment of IgA secreting cells into the mammary gland enabling the passive transfer of IgA antibodies from mother to infant.

Cytokine responses to EHV-1 infection in immune and non-immune ponies.

Protecting equids against equine herpesvirus-1 (EHV-1) infection remains an elusive goal. Repeated infection with EHV-1 leads to protective immunity against clinical respiratory disease, and a study was conducted to measure the regulatory cytokine response (IFN-gamma and IL-4) in repeatedly infected immune ponies compared to non-immune ponies. Two groups of four ponies were established. Group 1 ponies had previously been infected on two occasions, and most recently 7 months before this study. Group 2 ponies had no history no vaccination or challenge infection prior to this study. Both groups were subjected to an intranasal challenge infection with EHV-1, and blood samples were collected pre-infection, and at 7 and 21 days post-infection for preparation of PBMCs. At each time point, the in vitro responses of PBMCs to stimulation with EHV-1 were measured, including IFN-gamma and IL-4 mRNA production, and lymphoproliferation. Group 1 ponies showed no signs of clinical disease or viral shedding after challenge infection. Group 2 ponies experienced a biphasic pyrexia, mucopurulent nasal discharge, and nasal shedding of virus after infection. Group 1 ponies had an immune response characterized both before and subsequent to challenge infection by an IFN-gamma response to EHV-1 in the absence of an IL-4 response, and demonstrated increased EHV-1-specific lymphoproliferation post-infection. Group 2 ponies had limited cytokine or lymphoproliferative responses to EHV-1 pre-challenge, and demonstrated increases in both IFN-gamma and IL-4 responses post-challenge, but without any lymphoproliferative response. Protective immunity to EHV-1 infection was therefore characterized by a polarized IFN-gamma dependent immunoregulatory cytokine response.

Prediction of human cases of West Nile virus by equine cases, Saskatchewan, Canada, 2003.

In 2003, an outbreak of West Nile virus (WNV) occurred in Saskatchewan, Canada from July to September. One-hundred thirty-three horse cases and 947 human cases were recorded and data were analyzed retrospectively for evidence of clustering to determine if clinical infection in the horse population could be used to estimate human risk of infection with WNV. Kulldorff's scan statistic was used to identify spatial-temporal clusters in both the human and horse cases. In most areas, human clusters were not preceded by horse clusters. In one area, a significant cluster of horse cases preceded human cases by 1 week; however, 1 week does not provide sufficient time for human-health authorities to act and provide advance warning for the public.