Research Note: Repetitive element-based polymerase chain reaction genotyping improves efficiency of Salmonella surveillance in a model broiler production system.

The genetic relatedness and antimicrobial susceptibility profiles of Salmonella isolated from poultry and their environment were determined. One broiler breeder flock (BBF1) and 2 broiler flocks (BF1 and BF2) were reared over a 1.75-year period on the same poultry research farm. Hatching eggs were obtained from BBF1 to produce BF1 chicks, while BF2 chicks were progeny of a separate, unsampled broiler breeder flock. BF1 and BF2 were reared in the same housing facilities but 6 mo apart. Salmonella isolates were collected via litter sock sampling (BF1), cecal excision (BF1 and BF2), or cloacal swabs (BBF1). Serotyping identified Salmonella enterica subsp. enterica serovar Altona (SA) in BBF1 and S. enterica subsp. enterica serovar Senftenberg (SS) in BF1 and BF2. Genotypic fingerprinting was achieved with Rep-PCR using the (GTG)5 primer and revealed sequence homology among Senftenberg isolates from BF1 and BF2. For each isolate, the minimum inhibitory concentration was determined for 27 antimicrobial agents using Sensititre plates with formularies specific to antimicrobials used in poultry production or those used to control gram negative pathogens. Isolates from the 3 flocks were resistant to clindamycin, erythromycin, novobiocin, penicillin, and tylosin tartrate and demonstrated intermediate resistance to azithromycin, florfenicol, and spectinomycin. These data demonstrated that serovar Altona and Senftenberg were harbored by poultry, the latter appeared to persist in broiler flocks, and both serotypes shared similar patterns of antimicrobial susceptibility in an integrated research operation. In the case of multiple Salmonella isolates, combining genotypic fingerprinting methods with serotyping of representative isolates would reduce the number of samples required for serotyping and more clearly identify relatedness of isolates. These methods facilitate effective surveillance in poultry production systems, thus allowing for implementation of precise Salmonella control measures.

Gross Morphometry, Histomorphometry, and Immunohistochemistry Confirm Early and Persistent Jejunal Crypt Hyperplasia in Poults with Enteritis and Depressed Growth.

Phosphorylated histone 3 (PH3) and cleaved caspase 3 (CCASP3) were used to detect proliferating and apoptotic cells, respectively, in the jejunums of female sibling poults, with and without enteritis and depressed growth, from hatch to day 35. Poults that developed enteritis and depressed growth (SIB flock) were raised on a commercial farm in eastern North Carolina, whereas poults with normal growth and no enteritis (TAU flock) were raised in the Teaching Animal Unit at North Carolina State University College of Veterinary Medicine. Beginning on day 5 through day 35 and at processing, TAU poults were significantly heavier than SIB poults. Jejunal weights, relative jejunal weights, and jejunal densities were greater in SIB poults from day 10 through 35. Jejunal efficiency (body weight /jejunal length) was higher in TAU poults at day 5 and days 10 through 35. Mucosal thickness was greater in SIB poults between days 7 and 21 but greater in TAU poults at days 28 and 35. From day 7 to 35, villus-to-crypt ratios were higher for TAU poults and lower for SIB poults because hyperplastic crypts formed a greater percentage of the mucosa in SIB poults. By day 7, PH3- and CCASP3-positive cells were increased in SIB poults, showing that mucosal changes resulted from combined crypt epithelial hyperplasia and increased apoptosis of villous enterocytes. Findings in this study confirm that enteritis, in the absence of clinical signs, and depressed growth in turkey poults begins by day 7, can be identified microscopically, persists for at least 35 days, is associated with lower processing weights, and has a profound negative effect on turkey growth.

Mast Cells Exert Anti-Inflammatory Effects in an IL10-/- Model of Spontaneous Colitis.

Mast cells are well established as divergent modulators of inflammation and immunosuppression, but their role in inflammatory bowel disease (IBD) remains to be fully defined. While previous studies have demonstrated a proinflammatory role for mast cells in acute models of chemical colitis, more recent investigations have shown that mast cell deficiency can exacerbate inflammation in spontaneous colitis models, thus suggesting a potential anti-inflammatory role of mast cells in IBD. Here, we tested the hypothesis that in chronic, spontaneous colitis, mast cells are protective. We compared colitis and intestinal barrier function in IL10-/- mice to mast cell deficient/IL10-/- (double knockout (DKO): KitWsh/Wsh × IL10-/-) mice. Compared with IL10-/- mice, DKO mice exhibited more severe colitis as assessed by increased colitis scores, mucosal hypertrophy, intestinal permeability, and colonic cytokine production. PCR array analyses demonstrated enhanced expression of numerous cytokine and chemokine genes and downregulation of anti-inflammatory genes (e.g., Tgfb2, Bmp2, Bmp4, Bmp6, and Bmp7) in the colonic mucosa of DKO mice. Systemic reconstitution of DKO mice with bone marrow-derived mast cells resulted in significant amelioration of IL10-/--mediated colitis and intestinal barrier injury. Together, the results presented here demonstrate that mast cells exert anti-inflammatory properties in an established model of chronic, spontaneous IBD. Given the previously established proinflammatory role of mast cells in acute chemical colitis models, the present findings provide new insight into the divergent roles of mast cells in modulating inflammation during different stages of colitis. Further investigation of the mechanism of the anti-inflammatory role of the mast cells may elucidate novel therapies.

Culture methods impact recovery of antibiotic-resistant Enterococci including Enterococcus cecorum from pre- and postharvest chicken.

Pathogenic strains of Enterococcus cecorum (EC) expressing multidrug resistance have emerged. In National Antimicrobial Resistance Monitoring System (NARMS) data, EC is rarely recovered from chickens. Two NARMS methodologies (FDA and USDA) were compared with standard culture (SC) techniques for recovery of EC. NARMS methods failed to detect EC in 58 caecal samples, 20 chicken breast or six whole broiler samples. EC was recovered from 1 of 38 (2·6%) and 2 of 38 (5·2%) preharvest spinal lesions (USDA and FDA method, respectively). In contrast, using the SC method, EC was recovered from 44 of 53 (83%) caecal samples, all 38 (100%) spinal lesions, 14 of 20 (70%) chicken breast samples, and all three spinal lesions identified in whole carcasses. Compared with other Enterococcus spp., EC isolates had a higher prevalence of resistance to macrolides. The NARMS methods significantly affected recovery of enterococcal species other than EC. When the postharvest FDA method was applied to preharvest caecal samples, isolates of Enterococcus faecium were preferentially recovered. All 11 E. faecium isolates were multidrug resistant, including resistance to penicillin, daptomycin and linezolid. These findings confirm that current methodologies may not accurately identify the amount and range of antimicrobial resistance of enterococci from chicken sources. SIGNIFICANCE AND IMPACT OF THE STUDY: Enterococci are an important reservoir for antimicrobial resistance. This study demonstrates how current culture methods underreport resistance to macrolides in enterococci by selecting against strains of Enterococcus cecorum in pre- and postharvest chicken. Further, the application of postharvest surveillance methods to preharvest samples resulted in selective recovery of Enterococcus faecium over Enterococcus faecalis. Isolates of E. faecium recovered exhibited multidrug resistance including penicillin, daptomycin and linezolid resistance. These findings suggest that culture methodology significantly impacts the range and amount of antimicrobial resistance detected in enterococci isolated from chicken.

Pathogenesis of Enterococcal Spondylitis Caused by Enterococcus cecorum in Broiler Chickens.

Enterococcal spondylitis (ES) is a disease of commercial broiler chickens, with a worldwide distribution. Symmetrical hind limb paralysis typical of ES results from infection of the free thoracic vertebra (FTV) by pathogenic strains of Enterococcus cecorum . To determine the pathogenesis of ES, birds with natural and experimental ES were studied over time. In natural disease, case birds (n = 150) from an affected farm and control birds (n = 100) from an unaffected farm were evaluated at weeks 1-6. In control birds, intestinal colonization by E. cecorum began at week 3. In case birds, E. cecorum was detected in intestine and spleen at week 1, followed by infection of the FTV beginning at week 3. E. cecorum isolates recovered from intestine, spleen, and FTV of case birds had matching genotypes, confirming that intestinal colonization with pathogenic strains precedes bacteremia and infection of the FTV. Clinical intestinal disease was not required for E. cecorum bacteremia. In 1- to 3-week-old case birds, pathogenic E. cecorum was observed within osteochondrosis dissecans (OCD) lesions in the FTV. To determine whether OCD of the FTV was a risk factor for ES, 214 birds were orally infected with E. cecorum, and the FTV was evaluated histologically at weeks 1-7. Birds without cartilage clefts of OCD in the FTV did not develop ES; while birds with OCD scores ≥3 were susceptible to lesion development. These findings suggest that intestinal colonization, bacteremia, and OCD of the FTV in early life are crucial to the pathogenesis of ES.

Histiocytic sarcoma with central nervous system involvement in dogs: 19 cases (2006-2012).

BACKGROUND: Reports of histiocytic sarcoma (HS) involving the central nervous system (CNS) are sparse and consist mainly of case reports describing 1-3 animals. OBJECTIVE: The objective of this study was to report the signalments, clinical signs, clinicopathologic and diagnostic imaging findings, treatment, and outcome of a series of dogs with HS and CNS involvement. ANIMALS: Nineteen dogs with HS examined at veterinary referral hospitals. METHODS: Retrospective case series. Medical records were reviewed and cases with a histopathological diagnosis of CNS HS were included in the study. Diagnostic imaging studies of the CNS were evaluated and histopathologic samples were reviewed to confirm the diagnosis. RESULTS: Retrievers and Pembroke Welsh Corgis were overrepresented in this cohort of dogs. Tumors involved the brain in 14 dogs and the spinal cord in 5. In 4 dogs, HS was part of a disseminated, multiorgan process whereas it appeared confined to the CNS in 15 dogs. Diagnostic imaging had variable appearances although extraaxial masses predominated in the brain. There was meningeal enhancement in all dogs that was often profound and remote from the primary mass lesion. Pleocytosis was present in all dogs with CSF evaluation. Median survival was 3 days. CONCLUSIONS AND CLINICAL IMPORTANCE: Breed predispositions appear to vary from reports of HS in other organ systems. Some unique imaging and clinicopathologic characteristics, particularly brain herniation, profound meningeal enhancement, and pleocytosis in combination with 1 or more mass lesions, might help to differentiate this neoplasm from others involving the CNS, although this requires further study.

Early-life dietary spray-dried plasma influences immunological and intestinal injury responses to later-life Salmonella typhimurium challenge.

Increasing evidence supports the concept that early-life environmental influences, including nutrition and stress, have an impact on long-term health outcomes and disease susceptibility. The objective of the present study was to determine whether dietary spray-dried plasma (SDP), fed during the first 2 weeks post-weaning (PW), influences subsequent immunological and intestinal injury responses to Salmonella typhimurium challenge. A total of thirty-two piglets (age 16-17 d) were weaned onto nursery diets containing 0, 2·5 % SDP (fed for 7 d PW) or 5 % SDP (fed for 14 d PW), and were then fed control diets (without SDP), for the remainder of the experiment. At 34 d PW (age 50 d), pigs were challenged with 3 × 109 colony-forming units of S. typhimurium. A control group (non-challenged) that was fed 0 % SDP in the nursery was included. At 2 d post-challenge, the distal ileum was harvested for the measurement of inflammatory, histological and intestinal physiological parameters. S. typhimurium challenge induced elevated ileal histological scores, myeloperoxidase (MPO), IL-8 and TNF, and increased intestinal permeability (indicated by reduced transepithelial voltage (potential difference) and elevated 4 kDa fluorescein isothiocyanate dextran (FD4) flux rates). Compared with S. typhimurium-challenged controls (0 % SDP), pigs fed the 5 % SDP-14 d diet exhibited reduced ileal histological scores, MPO levels, IL-8 levels and FD4 flux rates. Pigs fed the 5 % SDP-14 d nursery diet exhibited increased levels of plasma and ileal TNF-α in response to the challenge, compared with the other treatments. These results indicate that inclusion of SDP in PW diets can have an influence on subsequent immunological and intestinal injury responses induced by later-life S. typhimurium challenge.

Biological behaviour of canine mandibular osteosarcoma. A retrospective study of 50 cases (1999-2007).

The purpose of this retrospective study was to describe the biological behaviour of canine mandibular osteosarcoma (OSA) and to examine factors for their impact on metastasis-free interval (MFI) and survival time (ST). Records from dogs treated with mandibulectomy for OSA (1999-2007) were reviewed. Archived tumour samples were evaluated for mitotic index (MI) and tumour grade. Fifty dogs were included, 21 received chemotherapy. Twenty-nine dogs (58%) developed metastatic disease. The median MFI was 627 days, and median ST was 525 days. In univariate analysis MI > 40 was prognostic for decreased MFI and ST. Grade also influenced MFI and ST, with 5/21 (24%) dogs with grade II/III tumours metastasis-free at one year versus 16/22 (72%) dogs with grade I tumours (P = 0.002); and 5/21 (24%) dogs with grade II/III tumours alive versus 17/22 (77%) dogs with grade I tumours (P = 0.001). In multivariate analysis, histological grade and adjuvant chemotherapy were prognostic for MFI and ST.

Antimicrobial resistance, virulence determinants and genetic profiles of clinical and nonclinical Enterococcus cecorum from poultry.

Enterococcus cecorum has been implicated as a possible cause of disease in poultry. However, the characteristics that contribute to pathogenesis of Ent. cecorum in poultry have not been defined. In this study, Ent. cecorum from carcass rinsates (n = 75) and diseased broilers and broiler breeders (n = 30) were compared based upon antimicrobial resistance phenotype, the presence of virulence determinants and genetic relatedness using pulsed-field gel electrophoresis (PFGE). Of the 16 antimicrobials tested, Ent. cecorum from carcass rinsates and clinical cases were resistant to ten and six of the antimicrobials, respectively. The majority of Ent. cecorum from carcass rinsates was resistant to lincomycin (54/75; 72%) and tetracycline (46/75; 61.3%) while the highest level of resistance among clinical Ent. cecorum was to tetracycline (22/30; 73.3%) and erythromycin (11/30; 36.7%). Multidrug resistance (resistance to ≥2 antimicrobials) was identified in Ent. cecorum from carcass rinsates (53/75; 70.7%) and diseased poultry (18/30; 60%). Of the virulence determinants tested, efaAfm was present in almost all of the isolates (104/105; 99%). Using PFGE, the majority of clinical isolates clustered together; however, a few clinical isolates grouped with Ent. cecorum from carcass rinsates. These data suggest that distinguishing the two groups of isolates is difficult based upon the characterization criteria used.

Pro-tumorigenic effects of transforming growth factor beta 1 in canine osteosarcoma.

BACKGROUND: Transforming growth factor beta 1 (TGFß1) is a pleiotropic cytokine that contributes to reparative skeletal remodeling by inducing osteoblast proliferation, migration, and angiogenesis. Organic bone matrix is the largest bodily reservoir for latent TGFß1, and active osteoblasts express cognate receptors for TGFß1 (TGFßRI and TGFßRII). During malignant osteolysis, TGFß1 is liberated from eroded bone matrix and promotes local progression of osteotropic solid tumors by its mitogenic and prosurvival activities. HYPOTHESIS: Canine osteosarcoma (OS) cells will possess TGFß1 signaling machinery. Blockade of TGFß1 signaling will attenuate pro-tumorigenic activities in OS cells. Naturally occurring primary OS samples will express cognate TGFß1 receptors; and in dogs with OS, focal malignant osteolysis will contribute to circulating TGFß1 concentrations. ANIMALS: Thirty-three dogs with appendicular OS. METHODS: Expression of TGFß1 and its cognate receptors, as well as the biologic effects of TGFß1 blockade, was characterized in OS cells. Ten spontaneous OS samples were characterized for TGFßRI/II expressions by immunohistochemistry. In 33 dogs with OS, plasma TGFß1 concentrations were quantified and correlated with bone resorption. RESULTS: Canine OS cells secrete TGFß1, express cognate receptors, and TGFß1 signaling blockade decreases proliferation, migration, and vascular endothelial growth factor secretion. Naturally occurring OS samples abundantly and uniformly express TGFßRI/II, and in OS-bearing dogs, circulating TGFß1 concentrations correlate with urine N-telopeptide excretion. CONCLUSIONS AND CLINICAL IMPORTANCE: Canine OS cells possess TGFß1 signaling machinery, potentially allowing for the establishment of an autocrine and paracrine pro-tumorigenic signaling loop. As such, TGFß1 inhibitors might impede localized OS progression in dogs.

Lymphoma immunophenotype of dogs determined by immunohistochemistry, flow cytometry, and polymerase chain reaction for antigen receptor rearrangements.

BACKGROUND: Immunohistochemistry (IHC), flow cytometry (FC), and PCR for antigen receptor rearrangements (PARR) are 3 widely utilized tests to determine immunophenotype in dogs with lymphoma (LSA). OBJECTIVES: This study evaluated the ability of FC and PARR to correctly predict immunophenotype as defined by IHC and to determine the level of agreement among the 3 tests. ANIMALS: Sixty-two dogs with lymphoma. METHODS: Retrospective study. Medical records were searched to identify dogs with LSA that had concurrent IHC, FC, and PARR performed. Immunophenotype results were categorized as B-cell, T-cell, dual immunophenotype (B- and T-cell), or indeterminate. The results of FC and PARR were evaluated for correctly classifying B- and T-cell LSA as compared with IHC. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were evaluated in addition to concordance between each test. RESULTS: The sensitivity of FC was significantly higher than PARR for both B-cell (91% versus 67%; P < 0.0072) and T-cell (100% versus 75%; P < 0.0312) LSA. The percent agreement between FC and IHC was 94%, between PARR and IHC was 69%, between FC and PARR was 63%, and among all 3 tests was 63%. CONCLUSIONS AND CLINICAL IMPORTANCE: Flow cytometry is superior to PARR in correctly predicting immunophenotype when evaluating lymph nodes from dogs already diagnosed with B- or T-cell LSA. If fresh samples are not available for FC, PARR is an acceptable assay for determination of immunophenotype given its high specificity.

Distribution of K and L cells in the feline intestinal tract.

Glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide (GLP)-1 and GLP-2 are hormones secreted from specialized K cells (GIP) and L cells (GLP-1, GLP-2) in the intestinal mucosa. These hormones play major roles in health and disease by modulating insulin secretion, satiety, and multiple intestinal functions. The aim of this study was to describe the distribution of K cells and L cells in the intestines of healthy cats. Samples of duodenum, mid-jejunum, ileum, cecum, and colon were collected from 5 cats that were euthanized for reasons unrelated to this study and had no gross or histologic evidence of gastrointestinal disease. Samples stained with rabbit-anti-porcine GIP, mouse-anti-(all mammals) GLP-1, or rabbit-anti-(all mammals) GLP-2 antibodies were used to determine the number of cells in 15 randomly selected 400× microscopic fields. In contrast to other mammals (eg, dogs) in which K cells are not present in the ileum and aborally, GIP-expressing cells are abundant throughout the intestines in cats (>6/high-power field in the ileum). Cells expressing GLP-1 or GLP-2 were most abundant in the ileum (>9/high-power field) as in other mammals, but, although GLP-1-expressing cells were abundant throughout the intestines, GLP-2-expressing cells were rarely found in the duodenum. In conclusion, the distribution of GIP-secreting K cells in cats is different from the distribution of K cells that is described in other mammals. The difference in distribution of GLP-2- and GLP-1-expressing cells suggests that more than 1 distinct population of L cells is present in cats.

Zebrafish (Danio rerio) as a screen for attenuation of Lancefield group C streptococci and a model for streptococcal pathogenesis.

Group C streptococci are highly contagious pyogenic bacteria responsible for respiratory tract, lymph node, urogenital tract, and wound infections. Wild-type strains of Streptococcus equi ssp equi (S. equi) and Streptococcus equi ssp zooepidemicus (S. zoo) as well as a commercially available modified live vaccine strain of S. equi were evaluated for virulence in zebrafish. Survival times, histologic lesions, and relative gene expression were compared among groups. Based on the intramuscular route of infection, significantly shorter survival times were observed in fish infected with wild-type strain when compared to modified live vaccine and S. zoo strains. Histologically, S. zoo-infected fish demonstrated a marked increase in inflammatory infiltrates (predominantly macrophages) at the site of infection, as well as increased cellularity in the spleen and renal interstitium. In contrast, minimal cellular immune response was observed in S. equi-injected fish with local tissue necrosis and edema predominating. Based on whole comparative genomic hybridization, increased transcription of positive acute-phase proteins, coagulation factors, and antimicrobial peptides were observed in S. equi-injected fish relative to S. zoo-injected fish, while mediators of cellular inflammation, including CXC chemokines and granulin, were upregulated in S. zoo-injected fish relative to S. equi-injected fish. In a screen of 11 clinical isolates, S. equi strains with a single nucleotide deletion in the upstream region of szp, a known virulence factor of streptococci, were found to be significantly attenuated in zebrafish. These collective findings underscore the value of the zebrafish as a model of streptococcal pathogenesis.

Characterization of immune cell infiltration into canine intracranial meningiomas.

Meningiomas are the most common intracranial tumors in dogs. A variety of inflammatory cells have been shown to invade these tumors in people, but little is known about interactions between the immune system and naturally occurring brain tumors in dogs. The purpose of this study was to investigate the presence of a variety of immune cell subsets within canine intracranial meningiomas. Twenty-three formalin-fixed, paraffin-embedded tumor samples were evaluated using immunohistochemistry with antibodies specific for CD3, CD79a, CD18, CD11d (αD), CD45RA, forkhead box P3, and Toll-like receptors 4 and 9. Immune cell infiltration was evident in all samples, with a predominance of CD3(+) T cells. Large numbers of CD18(+) microglia and macrophages were noted surrounding and infiltrating the tumors, and a subset of these cells within the tumor appeared to be CD11d(+). Scattered macrophages at the tumor-brain interface were TLR4(+) and TLR9(+). Rare CD79a(+) B cells were noted in only a small subset of tumors. Lesser numbers of lymphocytes that were CD11d(+), CD45RA(+), or FoxP3(+) were noted in a number of the meningiomas. Although the function of these cells is not yet clear, work in other species suggests that evaluation of this immune cell infiltrate may provide important prognostic information and may be useful in the design of novel therapies.

Cathepsin K expression and activity in canine osteosarcoma.

BACKGROUND: Cathepsin K (CatK) is a lysosomal protease with collagenolytic activity, and its secretion by osteoclasts is responsible for degrading organic bone matrix. People with pathologic bone resorption have higher circulating CatK concentrations. HYPOTHESIS: Canine osteosarcoma (OS) cells will possess CatK, and its secretion will be cytokine inducible. Circulating CatK concentrations will be increased in dogs with OS, and will be a surrogate marker of bone resorption. ANIMALS: Fifty-one dogs with appendicular OS and 18 age- and weight-matched healthy control dogs. METHODS: In a prospective study, expressions of CatK mRNA and protein were investigated in OS cells. The inducible secretion and proteolytic activity of CatK from OS cells was assessed in vitro. Serum CatK concentrations were quantified in normal dogs and dogs with OS and its utility as a bone resorption marker was evaluated in dogs with OS treated with palliative radiation and antiresorptive agents. RESULTS: Canine OS cells contain preformed CatK within cytoplasmic vesicles. In OS cells, TGFß1 induced the secretion of CatK, which degraded bone-derived type I collagen in vitro. CatK concentrations were higher in dogs with OS than healthy dogs (11.3 ± 5.2 pmol/L versus 8.1 ± 5.0 pmol/L, P = .03). In a subset of dogs with OS, pretreatment CatK concentrations gradually decreased after palliative radiation and antiresorptive treatment, from 9.3 ± 3.2 pmol/L to 5.0 ± 3.1 pmol/L, P = .03. CONCLUSIONS AND CLINICAL IMPORTANCE: Canine OS is associated with pathologic bone resorption, and CatK inhibitors might aid in the management of canine OS-related malignant osteolysis.

B-mode and Doppler ultrasonography in pony mares with experimentally induced ascending placentitis.

REASONS FOR PERFORMING STUDY: Early, accurate diagnosis of ascending placentitis in mares remains a key challenge for successful treatment of the disease. Doppler ultrasonography has shown promise as a tool to diagnose pregnancy abnormalities and is becoming more available to equine clinicians. However, to date, no studies have prospectively compared this technique to standard B-mode measurement of the combined thickness of the uterus and placenta (CTUP). OBJECTIVES: The objective of the current study was to compare Doppler and B-mode ultrasonography for the detection of experimentally-induced ascending placentitis in mares. METHODS: Eleven healthy pony mares in late gestation were used in this study. Placentitis was induced in 6 mares between Days 280 and 295, while 5 mares served as negative controls. All mares were intensively monitored until delivery. Fetal heart rate, CTUP, uterine artery blood flow (resistance index, pulsatility index, arterial diameter and total arterial blood flow) and physical examination findings were recorded at each examination. Mares with an increased CTUP above published values were treated in accordance with published recommendations. Foals and fetal membranes were examined at birth. Ultrasonographic parameters were compared between groups using ANOVA. Foal viability and histological presence of placentitis were compared using a Fisher's exact test. RESULTS: The CTUP was increased above normal in 5 of 6 inoculated mares within 3 days after inoculation (P = 0.05). The sixth inoculated mare was excluded from subsequent data analysis. Uterine artery blood flow, physical examination findings and fetal heart rate were not different between groups. Gradual increases in CTUP, arterial diameter and total arterial blood flow were detected with increasing gestational age in the control mares (P = 0.02, P = 0.00001 and P = 0.00001, respectively). CONCLUSION: The CTUP, but not uterine blood flow, was different between groups (P = 0.00001). Recorded CTUP values for control pony mares were similar to previously published values for light breed horses.