Validation of an equine serum amyloid A assay with an unusually broad working range

Enzyme-Linked Immunosorbent Assay (ELISA) Development for Equine Serum Amyloid A (SAA) Determination Using Recombinant Proteins

We aimed to develop a species-specific ELISA for qualitatively and quantitatively determining serum amyloid A (SAA) in horses. Current methods for measuring SAA in horses utilize ELISA or immunoturbidimetric tests designed for human SAA, which are not specific to horses. Mice and rabbits were used to generate polyclonal antibodies against equine SAA. The study examined serum samples from 32 horses with acute inflammatory disease (SG) and 25 clinically healthy horses. Furthermore, the SAAeq kinetics were observed in three horses from the SG group at three different timepoints. The SAA-ELISA established a cut-off at 0.06 OD492nm, where values equal to or higher than this were deemed positive, while values below it was considered negative. The test exhibited a sensitivity of 94% and specificity of 92%, resulting in an overall accuracy of 93%. The positive and negative predictive values were 94% and 92%, respectively. Coefficients of variation for inter- and intra-assay were 6.1% and 7.46% for SG and 9.6% and 9.63% for the control group (CG). The detection limit was determined to be 0.067. The SAA-ELISA proved its worth by demonstrating satisfactory performance, paving the way for the development of automated quantitative tests and species-specific semi-quantitative tests. This paves the way for their application in practical field settings.

ESTABLISHING REFERENCE INTERVALS FOR SERUM INFLAMMATORY MARKERS AND INVESTIGATING THEIR STORAGE STABILITY AND CLINICAL UTILITY IN ASIAN WILD HORSES (EQUUS FERUS PRZEWALSKII) UNDER MANAGED CARE

Acute phase proteins (APPs) are commonly used in domestic equine practice, where they rise rapidly in response to inflammation and decrease soon after resolution. This response provides useful information to identify, monitor, and prognosticate a variety of inflammatory conditions. Asian wild horses (Equus ferus przewalskii) are an endangered relative of the domestic horse, and APP reference intervals (RI) and clinical utility in this species are not well documented. This study used serum samples from clinically healthy Asian wild horses under managed care to establish RI for serum amyloid A (SAA, n = 21) using an equine SAA assay and haptoglobin (HP, n = 23) using a proprietary assay. The utility of SAA and HP in identifying inflammation in clinically abnormal horses was assessed, and storage stability of these analytes under refrigerated conditions was determined. The RIs established in this study were 0.3-6.8 mg/L for SAA and 0-3.25 g/L for HP. Six clinically abnormal cases were retrospectively assessed using the RI established in this study. One case of pituitary neoplasia showed elevated SAA levels, one case of maxillary lip phaeohyphomycosis and concurrent endometritis showed elevations in SAA and HP, and one case of chronic laminitis had elevated SAA. Storage stability of SAA and HP were assessed at 4°C over 7 d. SAA significantly decreased between Time 0 h and Time 72 h, but increased again at 7 d with no significant difference between Time 0 h and Time 7 d. Because of the initial decrease in SAA concentration over the first 72 h, it is recommended that SAA is analyzed within 48 h if freezing or immediate analysis is not possible. There was no significant difference between HP between Time 0 h and Time 7 d, suggesting stability of this analyte over this period if freezing or immediate analysis is not possible.

Application of blood parameters for the early diagnosis of natural ascending placentitis in pregnant mares

Placental infection is an important cause of late-term pregnancy loss and neonatal diseases in horses. Detection of changes in blood parameters especially during early placentitis could improve the diagnostic accuracy, treatment decision, and potential outcomes. The objectives of this 2-part study were to identify differences in circulating immunological, inflammatory, and hormonal parameters between mares with natural ascending placentitis and control mares; evaluate each and combination of parameters as predictors of placentitis; and determine how these parameters indicate severity of placentitis. Reproductive examination and blood sampling were prospectively performed on pregnant mares in a natural setting. Study 1 enrolled mares diagnosed with early stage of ascending placentitis based on ultrasonographic findings (n = 12), and gestationally age-matched mares with healthy pregnancies as controls (n = 12). Blood samples were classified as pre-onset (before) and early onset (at the time of ultrasonographic changes) of placentitis. There were no detected statistically significant differences between groups and timepoints in immunological and inflammatory parameters, including peripheral lymphocyte subpopulations, cytokine, and serum amyloid A concentrations. The placentitis group showed a reduced (P = 0.01) DHP/20α-DHP ratio when compared to the control group at the early onset timepoint. Plasma estradiol-17β concentration <359 pg/mL predicted ascending placentitis with acceptable accuracy (area under the curve, AUC = 0.71). Combined albumin <3.7 g/dL, estradiol-17β < 499 ng/mL, and DHP <33 ng/mL predicted 100 % of cases of ascending placentitis. In study 2, samples were classified according to the presence and severity of the abnormal ultrasonographic findings as mild (n = 11) and moderate-severe (n = 23), and gestationally age-matched with samples from control mares (n = 34). Mares with moderate-severe ascending placentitis had increased (P = 0.03) plasma 20α-DHP concentration and reduced (P = 0.03) DHP/20α-DHP ratio when compared to control mares. Our results suggest that the early events of ascending placentitis detected by ultrasonographic findings include hormonal alterations of feto-placental metabolism measurable in the mare's circulation, yet without obvious systemic immunological and inflammatory changes. Additional studies are warranted to further assess how hormonal markers and cutoff values could guide decisions for timely therapeutic intervention.

Assessment of health impacts in retired antisera-producing horses: Blood biochemistry and serum amyloid A analysis

Background and Aim

Horses used for antisera production are repeatedly hyperimmunized to produce high levels of specific antibodies. This prolonged process can lead to various health issues, including amyloidosis, which involves the accumulation of amyloid proteins in organs and tissues, potentially causing organ dysfunction and failure. These horses are often retired when they no longer produce adequate antibody levels. This study aimed to evaluate the impact of prolonged antisera production on the health of retired horses by examining their blood biochemistry and serum amyloid A (SAA) levels, which are indicators of systemic inflammation and organ damage.

Materials and Methods

Blood samples were collected from 12 horses for this study. Nine horses were retired antisera-producing horses that had been discontinued for 2 years, while three healthy non-antisera-producing horses were used as controls. These twelve horses were divided into four groups based on the duration of their active period as antisera producers (never been used, 2-3 years, 4-5 years, and 6-7 years). We measured key blood biochemistry parameters and SAA levels to evaluate the health status of the horses.

Results

Total protein, fibrinogen, and globulin levels were elevated, whereas other parameters remained normal. The findings indicate that despite normal SAA levels, the horses exhibited signs of ongoing health issues related to their previous use in antisera production, such as increased total plasma protein, fibrinogen, and globulin levels, as well as the presence of amyloid deposits in vital organs such as the liver and kidneys, as observed in post-mortem examinations.

Conclusion

Despite normal SAA levels, retired antisera-producing horses showed elevated total protein, fibrinogen, and globulin levels, indicating ongoing health issues.

The use of serum paraoxonase-1 to assess inflammation in horses with colitis

BACKGROUND

Paraoxonase-1 (PON-1) has been suggested as a marker of inflammation and oxidative stress in horses and could potentially be used for prognostication in horses with colitis.

OBJECTIVES

Assessment of PON-1 in horses with colitis and comparison of two methods.

METHODS

Serum PON-1 was measured by two methods (paraoxon and p-nitrophenyl acetate) in 161 horses with colitis and 57 controls. Follow-up samples obtained during hospitalization were available from 106 horses with colitis. The two methods were compared.

RESULTS

Serum PON-1 was significantly lower in horses with colitis than in healthy horses (P < .0001 for both methods) as well as in nonsurvivors compared with survivors (P = .0141 [paraoxon-based method] and P < .0001 [p-nitrophenyl acetate-based method]), but with marked overlap between groups. PON-1 activity did not change parallel to a change in inflammatory status in response to treatment when assessed at admission and in up to seven follow-up samples. Admission PON-1 activity could not reliably classify horses as survivors or nonsurvivors, with sensitivity and specificity ranging between 53.1% and 72.9%. Results from the two methods were comparable.

CONCLUSIONS

Both methods reliably measured serum PON-1 activity. Significant differences in PON-1 activity were found between healthy horses and horses with colitis and between survivors and nonsurvivors. However, PON-1 activity varied considerably within groups. Both the proposed reference intervals as well as alternative cutoff values resulted in suboptimal diagnostic and prognostic performance, and the use of serum PON-1 in horses with colitis thus seems to add little to existing diagnostic and prognostic markers.

Performance of an automated immunoturbidimetric assay for bovine serum amyloid A

BACKGROUND

Acute phase proteins are a group of vital constituents of the innate immune system, which may also serve as circulatory biomarkers of inflammation. The major acute phase protein serum amyloid A (SAA) is a reliable and sensitive biomarker in cows, allowing for rapid detection of inflammatory disease. A multispecies automated immunoturbidimetric assay (VET-SAA, Eiken) has been validated for horses, dogs, and cats, and it has been used to measure SAA concentrations in bovine samples.

OBJECTIVES

The aim of the present study was to perform an analytical validation of the VET-SAA immunoturbidometric assay based on monoclonal antihuman SAA antibodies for the measurement of SAA in clinical samples from cows.

METHODS AND RESULTS

The validation included an assessment of imprecision, inaccuracy, and detection limit, as well as an evaluation of the overlap performance, using banked serum from healthy and sick cows with or without inflammatory disease. Intra- and interassay variation ranged from 0.91% to 2.9% and 2.5% to 5.8%, respectively. The assay was performed with acceptable accuracy within a clinically relevant range of SAA, although minor signs of inaccuracy were detected. Overlap performance was acceptable, with the VET-SAA assay able to differentiate between healthy cows and cows with inflammatory and noninflammatory conditions. The automated VET-SAA assay is considered acceptable for the measurement of SAA in cows.

Simplified Light's Criteria and Acute Phase Proteins Reflect Aetiology of Feline Body Cavity Effusions Better than the Traditional Classification Scheme

The traditional veterinary classification (TVC) of effusions based on cell count and total protein (TP) does not adequately reflect the aetiology. Light's criteria (LC) (activity of lactate dehydrogenase [LDH] in the effusion [LDHef], effusion/serum LDH ratio [LDHr], effusion/serum TP ratio [TPr]), serum-effusion albumin gradient (ALBg), acute phase proteins (APPs) [serum amyloid A (SAA), α₁-acid glycoprotein (AGP), haptoglobin] might aid classification. The aim was to evaluate the utility of these parameters except LDHr in differentiating exudates from transudates. Sixty-five cats with effusions (33 peritoneal, 31 pleural, 1 pericardial), with 18 transudates and 47 exudates based on aetiological classification (AC), were included. The sensitivity, specificity and accuracy of several parameters to identify exudates (based on AC) was assessed. APPs were compared between exudates and transudates based on AC and TVC, with receiver operating characteristics analysis identifying the best APP to recognise exudates. Simplified LC (LDHef, TPr) had an accuracy of 79% and TVC of 48%. ALBg had the highest sensitivity (98%) and LDHef the highest specificity (83%) in identifying exudates in cats. All APPs but effusion SAA could differentiate exudates from transudates based on AC (effusion AGP had the largest area under the curve 0.79) but not TVC. All parameters were better than TVC in identifying exudates. The conformity of APPs with AC but not TVC favours the use of AC to classify effusions.

Use of serum amyloid A in equine medicine and surgery

Serum amyloid A (SAA) has become an indispensable part of the management of equine patients in general practice and specialized hospital settings. Although several proteins possess acute phase properties in horses, the usefulness of SAA exceeds that of other acute phase proteins. This is due to the highly desirable kinetics of the equine SAA response. SAA concentrations exhibit a rapid and pronounced increase in response to inflammation and a rapid decline after the resolution of inflammation. This facilitates the detection of inflammatory disease and real-time monitoring of inflammatory activity. SAA may be used in all stages of patient management: (1) before diagnosis (to rule in/rule out inflammatory disease), (2) at the time of diagnosis (to assess the severity of inflammation and assist in prognostication), and (3) after diagnosis (to monitor changes in inflammatory activity in response to therapy, with relapse of disease, or with infectious/inflammatory complications). By assessing other acute phase reactants in addition to SAA, clinicians can succinctly stage inflammation. White blood cell counts and serum iron concentration change within hours of an inflammatory insult, SAA within a day, and fibrinogen within 2-3 days; the interrelationship of these markers thus indicates the duration and activity of the inflammatory condition. Much research on the equine SAA response and clinical use has been conducted in the last decade. This is the prerequisite for the evidence-based use of this analyte. However, still today, most published studies involve a fairly low number of horses. To obtain solid evidence for use of SAA, future studies should be designed with larger sample sizes.

Acute phase reactants in nondomesticated mammals-A veterinary clinical pathology perspective

Applications for acute phase reactants (APRs) in nondomesticated mammals include identifying inflammatory disease, monitoring the course of specific disease processes and recovery during rehabilitation, detecting preclinical or subclinical disease, being used as bioindicators for monitoring population and ecosystem health, and as markers of stress and animal welfare. Serum amyloid A, haptoglobin, C-reactive protein, fibrinogen, albumin, and iron are most commonly measured. The procedure for evaluating an APR in a nondomesticated mammalian species should follow a stepwise approach beginning with an assessment of analytical performance, followed by an evaluation of overlap performance, clinical performance, and impact on patient outcomes and management. The lack of species-specific standards and antibodies for nondomesticated mammals presents a challenge, and more attention needs to be focused on assessing cross-reactivity and ensuring adequate analytical performance of APR assays. Sample selection for the initial evaluation of APRs should consider preanalytical influences and should originate from animals with confirmed inflammatory disease and healthy animals. Reference intervals should be generated according to published guidelines. Further evaluation should focus on assessing the diagnostic utility of APRs in specific disease scenarios relevant to a species. Greater attention should be paid to assay performance and uniformity of methods when using APRs for population and ecosystem surveillance. Veterinary clinical pathologists should work closely with zoo veterinarians and wildlife researchers to optimize the accuracy and utility of APR measurements in these various conservation medicine scenarios.

Experimental infection with African Horse Sickness Virus in horses induces only mild temporal hematologic changes and acute phase reactant response

OBJECTIVE

African Horse Sickness (AHS) is a vector-borne disease endemic to sub-Saharan Africa caused by African Horse Sickness Virus (AHVS). Infections in naïve horses have high morbidity and mortality rates. AHS pathogenesis is not well understood; neither the hematologic changes nor acute phase response occurring during infection has been fully evaluated. The study's objective was to characterize the hematologic changes and acute phase response during experimental infection with AHSV.

ANIMALS

4 horses negative for AHSV group-specific antibodies.

PROCEDURES

In this prospective, longitudinal study conducted between November 23 and December 2, 2020, horses were experimentally infected with AHSV, and blood samples were obtained before inoculation and then every 12 hours until euthanasia. Hematologic changes and changes for serum amyloid A (SAA) and iron concentration were evaluated over time using a general linear model including natural logarithm of sampling time.

RESULTS

All horses were humanely euthanized due to severe clinical signs typical of AHS. Median Hct increased significantly, and the median WBC count, monocyte count, eosinophil count, and myeloperoxidase index changed significantly in all horses over time. Horses developed marked thrombocytopenia (median, 48 X 103 cells/µL; range, 21 X 103 to 58 X 103 cells/µL) while markers of platelet activation also changed significantly. Median SAA increased and serum iron concentration decreased significantly over time.

CLINICAL RELEVANCE

Results indicated severe thrombocytopenia with platelet activation occurs during infection with AHSV. Changes in acute phase reactants SAA and iron, while significant, were unexpectedly mild and might not be useful clinical markers.

Comparative evaluation of acute phase proteins by C-reactive protein (CRP) and serum amyloid A (SAA) in nonhuman primates and feline carnivores

The feasibility of a commercially available assay for C-reactive protein (CRP, CRP for humans: hCRP, and CRP for dogs: vCRP) and a trial reagent of serum amyloid A (SAA, vSAA for animals) were applied to the measurement of acute phase proteins in zoo animals, particularly in nonhuman primates and feline carnivores was evaluate. Results showed that hCRP and vSAA methods were applicable to measure CRP and SAA in Haplorhini. There was a highly significant correlation between both parameters with remarkably high correlation coefficient. A higher proportion of Bonnet macaques in Haplorhini, and the linear regression with good correlation between hCRP and vSAA levels were observed. Reference values in healthy Bonnet macaques were hCRP (46.86 ± 30.97 nmol/L) and vSAA (9.06 ± 1.95 μg/mL). Although Ring-tailed lemur, which belonging to Strepsirrhini, showed low vSAA concentrations (reference values: 1.08 ± 0.47 μg/mL), vSAA in patients was apparently elevated. The vCRP and vSAA methods were applicable to measurements of CRP and SAA in feline carnivores for highly significant correlation between both parameters. Theses two methods were also been deteded in lions, tigers and cheetahs. vSAA assays can be applied to measure SAA levels in other carnivores and herbivores. In conclusion, vSAA systems have potential utility as diagnostic tools for health screening and prediction in zoo animals.

Validation of an automated immunoturbidimetric assay for feline serum amyloid A

BACKGROUND

Serum Amyloid A (SAA) is a major acute phase protein in cats, increasing rapidly in response to various inflammatory diseases. An automated latex-enhanced immunoturbidimetric assay for human SAA (LZ-SAA, Eiken), previously validated for use in cats, has had further major modification (VET-SAA, Eiken) for specific use in veterinary diagnostic laboratories but has yet to be validated in cats.

RESULTS

Intra-assay and inter-assay CVs for the VET-SAA assay ranged from 1.88-3.57% and 3.98-6.74%, respectively. Linearity under dilution was acceptable with no prozone effect observed. Limit of detection was 1.65 mg/L and limit of quantification was 6 mg/L. Haemoglobin and triglyceride showed no adverse interference, but bilirubin produced positive bias in samples with low SAA. Comparison with the LZ-SAA assay showed significant correlation with proportional bias increasing as SAA concentration increased, likely related to differing calibration standards. SAA was significantly higher in patients with inflammatory disease compared with non-inflammatory disease, and in patients with moderate to highly elevated α1-AGP compared with patients with normal α1-AGP. Improvement of the assay range may be required to fully evaluate differences between disease groups at low SAA levels. Based on ROC curve analysis, at a cut-off point of 20.1 mg/L the VET-SAA assay discriminated between inflammatory and non-inflammatory disease with sensitivity of 0.93 and specificity of 0.99.

CONCLUSIONS

The automated VET-SAA assay is a robust, precise, and accurate method for measurement of feline SAA which can clearly identify patients with inflammatory disease. It should be a valuable biomarker for use in feline medicine.

Concentrations of Neutrophil Gelatinase-Associated Lipocalin are increased in serum and peritoneal fluid from horses with inflammatory abdominal disease and non-strangulating intestinal infarctions

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is produced in response to inflammation in horses, but it has not yet been investigated as a biomarker in horses with abdominal disease.

OBJECTIVES

To investigate NGAL in serum and peritoneal fluid in horses with abdominal disease.

STUDY DESIGN

Retrospective clinical study.

METHODS

Data from medical records of 270 horses admitted with acute abdominal disease (simple obstructions [n=43], strangulating obstructions [n=104], inflammatory abdominal disease [n=99], non-strangulating intestinal infarction [NSII, n=24]) and 9 healthy control horses were reviewed, and serum and peritoneal fluid samples were retrieved from a biobank. NGAL was measured in serum and peritoneal fluid by ELISA. Differences in NGAL concentrations between groups were assessed.

RESULTS

Healthy horses had low serum and peritoneal fluid concentrations of NGAL (median = 21.0 and 9.5 μg/L, respectively). Neither serum nor peritoneal fluid NGAL concentrations (median serum, peritoneal fluid) differed between healthy horses and horses with simple (28.1 μg/L, 13.0 μg/L) and strangulating intestinal obstructions (34.7 μg/L, 38.4 μg/L). Horses with NSII (308.0 μg/L, 2163.0 μg/L) and inflammatory abdominal disease (171.1 μg/L, 314.1 μg/L) had higher serum and peritoneal fluid concentrations of NGAL than the other groups (P<0.001). Peritoneal fluid NGAL concentrations in horses with NSII were higher than in horses with inflammatory abdominal disease (P=0.03).

MAIN LIMITATIONS

Retrospective study design; small group of control horses.

CONCLUSIONS

NGAL is a marker of inflammation in horses with abdominal disease. The high peritoneal fluid concentration of NGAL in horses with NSII compared to all other groups may render NGAL useful for identifying this condition, which is otherwise difficult to differentiate from other types of peritonitis. Thereby, NGAL may potentially facilitate timely surgical intervention in this group of patients. The results of this study must be evaluated in larger, and preferably prospective, studies to obtain a more comprehensive evaluation of the diagnostic utility of NGAL. This article is protected by copyright. All rights reserved.

Acute phase protein response and changes in lipoprotein particle size in dogs with systemic inflammatory response syndrome

Background

Improved methodology to measure acute phase proteins and determination of lipoprotein particle‐size distribution (PSD) could be clinically useful in dogs with systemic inflammatory processes.

Objectives

Evaluate an immunoturbidometric assay for serum amyloid A (SAA) and lipoprotein PSD in dogs with sepsis, nonseptic systemic inflammation, and in healthy controls. Correlate dyslipidemic changes with SAA and C‐reactive protein (CRP) concentrations.

Animals

Twenty‐five dogs with sepsis, 15 dogs with nonseptic systemic inflammation, and 22 healthy controls.

Methods

Prospective, case‐control study. Variables included SAA, CRP, and electrophoretic subfractionation of high‐ and low‐density lipoproteins (HDL, LDL). Continuous variables were compared using ANOVA or Kruskal‐Wallis tests with linear regression or Spearman's rank correlation used to assess relationships between variables.

Results

Median SAA and CRP concentrations were greater in dogs with sepsis (SAA 460 mg/L, interquartile range [IQR] 886 mg/L; CRP 133.2 mg/L, IQR 91.6 mg/L) and nonseptic inflammation (SAA 201 mg/L, IQR 436 mg/L; CRP 91.1 mg/L, IQR 88.6 mg/L) compared to healthy dogs (SAA 0.0 mg/L, IQR 0.0 mg/L; CRP 4.9 mg/L, IQR 0.0 mg/L) P < .0001. A cutoff of >677.5 mg/L SAA was 43.2% sensitive and 92.3% specific for sepsis. Low‐density lipoprotein was higher in dogs with sepsis 29.6%, (mean, SD 14.6) compared to 14.4% (mean, SD 5.6) of all lipoproteins in healthy controls (P = .005). High‐density lipoprotein was not associated with CRP but was negatively correlated with SAA (r_s −0.47, P < .0001). Subfractions of LDL and HDL differed between groups (all P < .05).

Conclusions and Clinical Importance

Measurement of SAA using the immunoturbidometric assay evaluated in this study and lipoprotein PSD in dogs with inflammation might help distinguish septic from nonseptic causes of inflammation.

Assessment of automated assays for serum amyloid A, haptoglobin (PIT54) and basic biochemistry in broiler breeders experimentally infected with Escherichia coli

Biomarkers of inflammation are valuable tools for health status evaluation in numerous species. However, in poultry, methods for measuring acute phase proteins (APP) are sparse and rely on manual laboratory labour reserving these parameters mainly for research studies with APP as a focus point. To extend the use of APP beyond tightly focused research studies, blood from experimentally infected and control hens was analysed using equipment available in many veterinary clinics in order to identify easily accessible biomarkers of infection. Blood samples from broiler breeders (n = 30) inoculated intratracheally with either Escherichia coli or sterile vehicle were randomly selected at 2, 4 and 7 days post-infection (dpi) and subjected to biochemical analysis. Samples for bacteriological testing were collected, and all animals were subjected to a full necropsy for disease confirmation. Significantly higher levels of serum amyloid A were evident in the infected birds at 2 and 4 dpi (p < 0.01) compared to the controls. Likewise, haptoglobin (PIT54) levels were significantly elevated at 4 dpi (p < 0.01) in the infected animal, whilst at 2 dpi magnesium and calcium were significantly lower in the infected group (p < 0.05). Gross pathology and bacteriology confirmed the presence of infection in the E. coli inoculated birds. In conclusion, equipment routinely used in other species for rapid analysis of blood samples, successfully differentiated between sick and healthy birds, hereby, showing great potential as an easily added parameter of evaluation in research studies, and as a valuable decision-making tool for poultry veterinarians.

Interrelationship between reproductive hormones and acute phase proteins during estrous cycle and pregnancy in Spanish purebred broodmares

In some species, female steroid hormones modify the profile of acute phase proteins (APPs) during the estrous cycle and pregnancy, according to the ovulation, embryonic implantation and placental development; however, nowadays there's no experimental evidence for equine species. Objectives of this study were: to compare the serum amyloid A (SAA), haptoglobin (Hp) and C-reactive protein (CRP) concentrations between cyclic and pregnant mares, and to analyze the influence of estradiol-17β (E2) during estrous cycle or estrone sulfate (E1) during pregnancy, and progesterone (P4) on these proteins to assess their potential role to identify the cyclicity or pregnancy in Spanish mares. Blood samples were taken from 20 Purebred Spanish mares on the day of ovulation (day 0), on days +5 and +16 post-ovulation, and then, monthly during the whole pregnancy. SAA, Hp and CRP did not change between day 0, +5 and +16 post-ovulation days. P4 concentrations were significantly higher on day +16 than on days +5 and 0; and E2 concentrations were significantly higher on day 0 than day +5. On the other hand, pregnancy was characterized by a progressive increase in the Hp, variable modifications of E1 and P4 concentrations, without changes in SAA and CRP. The absence of significant differences in the APPs between days 0, +5 and +16, suggested that these proteins cannot be used as biomarkers of diagnosis of heat or pregnancy in Spanish mares, at least early, since the Hp later increases during the gestation. Nevertheless, it is possible to use them for comparative purposes with other equine breeds, as supervisor instrument of health status in breeding females as diagnostic tools to monitor pregnancy's development and/or subclinical reproductive inflammations, that could lead to the early embryonic death.

Comparison of a point-of-care serum amyloid A analyzer frequently used in equine practice with 2 turbidimetric immunoassays used in human and veterinary medicine

Rapid, accurate detection of serum amyloid A (SAA) is needed in equine practice. We validated a patient-side point-of-care (POC) assay (Stablelab; Zoetis) compared to the turbidimetric immunoassays LZ-SAA (TIA-Hum) and VET-SAA (TIA-Vet; both Eiken Chemical). Analytical performance was assessed at 3 different concentration ranges and with interferences. Inter-method comparison using 49 equine serum samples revealed a significant difference between median SAA results (p < 0.0001), with the strongest bias between the POC and TIA-Vet (median 1,093 vs. 578 mg/L). The median SAA value obtained with the TIA-Hum method was 752 mg/L. Correlation between POC/TIA-Hum and between POC/TIA-Vet was fair (r_s = 0.77 and 0.69) and excellent between both TIAs (r_s = 0.93). Bias between POC/TIA-Hum, POC/TIA-Vet, and TIA-Hum/TIA-Vet was −56.7%, –80.9%, and −28.2%, respectively. POC intra- and inter-assay CVs (16.1–30% and 19.8–35.5%) were higher than TIA CVs (generally <12%). Bilirubin and hemoglobin had a negative bias on POC and TIA-Vet results (−16.6 to −45.6%); addition of intralipid yielded a positive bias (35.9–77.4%). The POC had good linearity of SAA concentrations up to 10,312 mg/L (R² = 0.92). A hook effect was present at SAA >3,000 mg/L for the POC assay. Equine serum SAA was stable over a median period of 2.5 y when stored at −80°C. Overall, there was excellent-to-moderate correlation between tests, but imprecision and hook effect of the POC, as well as bias between the methods, must be considered.

Bullous amyloidosis in a horse: first description in veterinary medicine

BACKGROUND

Bullous amyloidosis is a rare disease in humans that has not been described in a veterinary species in the peer-reviewed literature. The human disease is characterised by haemorrhagic vesicles and bullae on the skin and mucosae, which form due to amyloid deposition.

HYPOTHESIS/OBJECTIVES

To describe the clinical features, laboratory analysis and histopathological features of an unique presentation of bullous disease in a horse.

ANIMALS

A 17-year-old thoroughbred mare presented for weight loss and severe oral cavity ulcers.

METHODS AND MATERIALS

Investigations involved haematological evaluation, chemistry profiles, gastroscopy and serum protein electrophoresis, and, postmortem, histopathological evaluation, Congo-red staining and transmission electron microscopy (TEM).

RESULTS

Haemorrhagic vesicles and bullae occurred on the mucosa of the oral cavity, lips, oesophagus and stomach, and much less the muzzle, face and mucocutaneous areas of the perineum, where scarring was evident. Histopathological evaluation and Congo-red staining confirmed the presence of amyloid deposits in dermis and submucosa, in association with vesicle and bulla formation, consistent with bullous amyloidosis. TEM confirmed amyloid fibril deposition in the dermis and along the basement membrane zone. Clefts occurred in the superficial dermis and submucosa, which explained haemorrhage and scarring. The presence of a polyclonal gammopathy and the rapid abolishment of Congo-red staining with performate pretreatment supported serum amyloid A and secondary amyloidosis.

CONCLUSION AND CLINICAL IMPORTANCE

Bullous amyloidosis is a novel disease of the horse and a newly recognised differential for bullous disease, for which the haemorrhagic nature of bullae, scarring and deep secondary ulcers are considered clinical clues to the condition.

Reference intervals of acute phase proteins in healthy Andalusian donkeys and response to experimentally induced endotoxemia

BACKGROUND

Assessment of acute phase proteins (APPs) may allow prompt detection of diseases in donkeys, that otherwise may be missed because of the stoic behavior of donkeys. Reference intervals (RIs) of APPs measured using immunoassays and a comparison of the response of these biomarkers to a controlled inflammatory insult are lacking in donkeys.

OBJECTIVES

(a) To describe the RIs for APPs in healthy Andalusian donkeys, (b) to study the effects of sex and age on APPs, and (c) to assess the early response of APPs to experimentally induced endotoxemia.

ANIMALS

Seventy-three healthy Andalusian donkeys (67 for RIs and 6 for endotoxemia).

METHODS

Serum amyloid A (SAA), haptoglobin (Hp), C-reactive protein (CRP), ceruloplasmin (Cp), α1-acid glycoprotein (AGP), procalcitonin (PCT), ferritin (Ft), and fibrinogen (Fb) RIs were determined. Endotoxemia was induced and samples for APP determination were obtained at regular intervals for 4 hours.

RESULTS

The RIs in Andalusian donkeys were: SAA (0.1-0.6 mg/L), Hp (75-2261 mg/L), CRP (1.3-7.0 mg/L), Cp (0-745 mg/L), AGP (0-884 mg/L), PCT (0-504 pg/mL), Ft (26.9-31.8 μg/L), and Fb (115-466 mg/dL). Concentrations of SAA were higher (P < .05) in jacks. Donkeys <5 years old had higher Cp, AGP, and PCT compared to older donkeys. Concentrations of SAA and Hp were significantly increased in endotoxemic donkeys from 2 hours postinduction.

CONCLUSIONS AND CLINICAL IMPORTANCE

We illustrated the importance of using species-specific RIs for APPs in donkeys and the effect of age and sex on APP concentrations. Concentrations of SAA and Hp appear to be the most useful biomarkers in donkeys in the early stages of endotoxemia.