Clinical Assessment of a Point-of-Care Serum Amyloid A Assay in Foals with Bronchopneumonia

Evaluation of oxidative stress in foals with Rhodococcus equi infection-induced pneumonia for the judgment of therapeutic effect

Forty-five foals with Rhodococcus equi infection and pneumonia symptoms were classified into a surviving group and a dead group. Using serum samples, the oxidative stress index (OSI) was determined at the first visit and the follow-up visit. The OSI of the surviving group was significantly lower at the follow-up than that at the first visit. No significant difference was observed between the OSI of the dead group at the first and follow-up visits. In the surviving group, treatment at the first visit mitigated inflammation and reduced OSI. However, in the dead group, poor response to the treatment provided at the first visit led to continued inflammation, and no change was observed the OSI.

Investigation of the relationship between pulmonary lesions based on lung ultrasound and respiratory clinical signs in foals with suspected pulmonary rhodococcosis

Rhodococcus equi is a widely recognized bacterium responsible for pneumonia in preweaned foals. On endemic farms, foals with a subclinical course of the disease usually outnumber those presenting clinical signs. The disease is typically chronic and mainly manifests as fever and dyspnoea. Currently, field diagnosis is often based on lung ultrasound (LUS); however, both diagnostic and therapeutic approaches vary among practitioners and considerably change over time. This longitudinal, prospective study was designed to describe the appearance and progression of rhodococcal pulmonary lesions during the first months of life based on LUS and to evaluate the relationship between the presence and severity of rhodococcal pulmonary lesions and the occurrence of respiratory clinical signs in foals from farms with endemic R. equi infections. Nearly 26% of foals demonstrated respiratory signs highly suggestive of pulmonary rhodococcosis, and approximately 70% of the foals had abnormalities detected on LUS without concurrent clinical signs. The appearance and development of LUS abnormalities were age-related. An abscess diameter exceeding 15 mm in LUS and other pleural lesions were significantly linked with the occurrence of clinical signs suggestive of pulmonary rhodococcosis (P < 0.001) and may be considered predictive factors of rhodococcal pneumonia in foals.

Utility of serum amyloid A in monitoring clinical response to antimicrobial treatment in horses with bacterial pneumonia

BACKGROUND

Serum amyloid A (SAA) is a major acute phase protein in horses which could be a useful tool for assessing clinical response to treatment of bacterial pneumonia in adult horses.

OBJECTIVES

To monitor SAA concentration in response to treatment and identify associations among SAA concentration, WBC and neutrophil counts, and fibrinogen in bacterial pneumonia in adult horses.

ANIMALS

Eighteen adult horses with bacterial pneumonia.

METHODS

Prospective clinical study. Horses hospitalized with bacterial pneumonia were enrolled and SAA concentration and vital signs were assessed daily. SAA concentration was measured by a handheld meter. CBC and plasma fibrinogen were assessed on days 0, 1, and 2, then every 3 days until discharge. Data were not normally distributed and therefore were log transformed. Log-transformed data were analyzed and comparisons were performed on LSMeans by the 2-sided Student's t-test at the 5% level of significance.

RESULTS

Geometric mean SAA concentration on day 0 was 537 μg/mL (SE 383 μg/mL). Geometric mean SAA concentration decreased significantly over time (P = .0001), peaking at day 2 (geomean 1038 μg/mL, SE 261.7 μg/mL) and decreasing until discharge. Plasma concentration of fibrinogen (P = .06), neutrophil count (P = .48), and WBC count (P = .07) did not change significantly over time.

CONCLUSIONS AND CLINICAL IMPORTANCE

SAA concentration decreased significantly over the course of treatment and correlated with clinical improvement of pneumonia whereas fibrinogen, neutrophil, and WBC counts did not.

Evaluation of serum concentration of acute-phase proteins (haptoglobin and serum amyloid A) in the affected Arabian foals with rhodococcosis

BACKGROUND

Early detection of Rhodococcus equi pneumonia in foals is essential for horse health and for veterinarians.

OBJECTIVES

This study aimed to demonstrate the usefulness of assessing the serum concentration of acute-phase proteins (APPs) in the early diagnosis of pneumonia.

METHODS

The study evaluated APPs in 19 Arabian foals with R. equi pneumonia and compared them with 18 normal Arabian foals in equestrian clubs in Tabriz, Iran. Affected foals were identified through history, clinical findings and bacterial culture of tracheal washing. Biochemical methods and polymerase chain reaction tests were performed by examining the 16S rRNA and vapA genes to confirm the diagnosis of bacterial isolates. Blood samples were taken from all sick and healthy horses, and their serum was isolated. APPs in the serum were measured in all the samples.

RESULTS

Rhodococcosis increased the serum concentration of haptoglobin (Hp) and serum amyloid A (SAA) (p < 0.001). The relationship between SAA and Hp was meaningful in the infected group (r = 0.933) but not in the healthy group. In cases where there are clinical findings of R. equi pneumonia, the concentration of SAA and Hp can help the effectiveness of treatment.

- CONCLUSIONS

Serum concentration analysis of APPs can be helpful in early diagnosis and successfully treating foals with R. equi pneumonia.

A prospective study of serum amyloid A in relation to plasma administration in neonatal foals

SAA is a commonly used biomarker for measuring acute inflammation in equine practice, and the administration of prophylactic plasma to foals is a routine practice in large breeding farms. Despite this, limited information is available on the values of SAA in healthy or sick neonatal foals following this common procedure. A prospective study was conducted with 31 foals from a veterinary hospital in Texas in one year. Enrolled foals were part of a foaling program, where a prophylactic hyperimmunized plasma was administered 12 h after birth. Blood was collected for SAA measurements at birth and at 12 h (pre-plasma), 13 h (post-plasma), 24 h, 48 h, 72 h, and 96 h. Eight of the foals were clinically ill prior to plasma administration, and 23 foals were clinically normal. The mean SAA of all foals at birth was 1 μg/mL, increased to 11 μg/mL at 12 h (pre-plasma), and at 13 h (post-plasma) was 155 μg/mL. At 13 h, 65% of normal foals and 63% of sick foals had an SAA value >100 μg/mL. Transient but substantial increases in SAA following prophylactic plasma administration were frequently observed in this study. Veterinarians evaluating neonatal foals for clinical disease in the field should be cognizant of the timing of blood sampling in relation to plasma administration.

Serum amyloid A as an aid in diagnosing sepsis in equine neonates

BACKGROUND

Sepsis is a significant cause of morbidity and mortality in neonatal foals, especially during the first 7 days of life. Diagnosing sepsis in neonatal foals can be challenging because initial clinical signs are often ambiguous and non-specific.

OBJECTIVES

To determine if the major acute phase protein serum amyloid A (SAA) as measured by a point-of-care SAA testing device can be used as an evidence-based biomarker of sepsis.

STUDY DESIGN

Retrospective cohort.

METHODS

Clinical diagnosis of sepsis based on positive bacterial blood culture or a positive sepsis score was obtained and compared to SAA values in a population of neonatal foals on a breeding farm and referral hospital during four consecutive foaling seasons. A rapid, point-of-care blood test was used to measure SAA concentrations in neonatal foals <36 hours old that were clinically diagnosed as healthy, sick non-septic or septic.

RESULTS

The septic foals (n = 35) had a median SAA concentration (114 µg/mL) that was significantly greater (P < .05) than that for foals in the sick non-septic (n = 117, 1.5 µg/mL) and healthy (n = 245, 0 µg/mL) groups. At a diagnostic threshold of 100 µg/mL, the SAA test had a sensitivity of 52.9% (95% CI 36.5-68.9), specificity of 97.5% (95% CI 95.0-99.0), positive predictive value of 75.0% (95% CI 56.2-87.5), negative predictive value of 93.7% (95% CI 91.2-95.5), and a test accuracy of 92.1% (95% CI 88.2-95.0).

CONCLUSIONS

The results of this study indicate that SAA is a useful aid in the diagnosis of sepsis in the neonatal foal.

Serum Amyloid A Aggravates Lipopolysaccharide-Induced Injury of BEAS-2B Cells by Activating Toll-Like Receptor 2/Activator Protein-1 Signaling

The serum amyloid A (sAA) is a common sensitive indicator for the diagnosis of infectious diseases, and sAA levels are increased in pneumonia. However, the detailed molecular mechanism is unknown. Previous studies have demonstrated the participation of Toll-like receptor (TLR) 2 and its downstream protein activator protein-1 (AP-1) in inflammatory lung injury. This study aimed to investigate the effect of sAA on LPS-induced BEAS-2B cells injury and uncover the possible mechanism. The human bronchial epithelial cell line BEAS-2B was exposed to sAA with or without lipopolysaccharide (LPS) treatment, then cell viability, inflammation and apoptosis were evaluated. The effects of TLR2 knockout on sAA + LPS-treated BEAS-2B cells were also determined. Results revealed that sAA treatment reduced cell viability in a concentration-dependent manner and the effect of 500 nM sAA on cell viability was approximately equivalent to LPS. The levels of inflammatory cytokines including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-8, monocyte chemotactic protein (MCP)-1 and IL-6 as well as cell apoptosis and expression of proteins related to apoptosis were significantly increased upon sAA or LPS stimulation. The expression of TLR2 and AP-1 was also elevated in cells challenged with sAA or LPS. Besides, sAA and LPS co-treatment further enhanced the actions of LPS. However, the knockdown of TLR2 obviously blunted the effects of LPS and sAA co-treatment on cell viability, inflammation and apoptosis. Taken together, our results revealed that sAA could exert an enhanced effect on LPS-induced BEAS-2B cells injury via promoting TLR2/AP-1 expression.

Current Trends in Understanding and Managing Equine Rhodococcosis

The aim of this review was to summarize studies on equine rhodococcosis over the last decade. For many years Rhodococcus equi has remained one of the major health challenges in the equine breeding industry worldwide. Recently, many novel approaches and ideas have been described and some of them were initially implemented into the clinical practice. This study reviews a variety of new information about neonatal susceptibility, clinical appearance, considered and applied diagnostic procedures and treatment alternatives, factors limiting accurate prognosis, ideas regarding environmental management and prophylaxis considerations. Although multiple research were conducted, the main problems such as high morbidity and mortality, a lack of reliable prevention strategies and treatment limitations are still unresolved and require further scientific effort.

Serum amyloid A in equine health and disease

Serum amyloid A (SAA) is the major acute phase protein in horses. It is produced during the acute phase response (APR), a nonspecific systemic reaction to any type of tissue injury. In the blood of healthy horses, SAA concentration is very low, but it increases dramatically with inflammation. Due to the short half‐life of SAA, changes in its concentration in blood closely reflect the onset of inflammation and, therefore, measurement of SAA useful in the diagnosis and monitoring of disease and response to treatment. Increases in SAA concentration have been described in equine digestive, reproductive and respiratory diseases and following surgical procedures. Moreover, SAA has proven useful for detection of some subclinical pathologies that can disturb training and competing in equine athletes. Increasing availability of diagnostic tests for both laboratory and field use adds to SAA's applicability as a reliable indicator of horses’ health status. This review article presents the current information on changes in SAA concentrations in the blood of healthy and diseased horses, focussing on clinical application of this biomarker.

Analytical validation of a new point-of-care assay for serum amyloid A in horses

BACKGROUND

Serum amyloid A (SAA) is a major acute phase protein in horses. A new point-of-care (POC) test for SAA (Stablelab) is available, but studies evaluating its analytical accuracy are lacking.

OBJECTIVES

To evaluate the analytical performance of the SAA POC test by 1) determining linearity and precision, 2) comparing results in whole blood with those in serum or plasma, and 3) comparing POC results with those obtained using a previously validated turbidimetric immunoassay (TIA).

STUDY DESIGN

Assay validation.

METHODS

Analytical validation of the POC test was done in accordance with American Society of Veterinary Clinical Pathology guidelines using residual equine serum/plasma and whole blood samples from the Clinical Pathology Laboratory at the University of California-Davis. A TIA was used as the reference method. We also evaluated the effect of haematocrit (HCT).

RESULTS

The POC test was linear for SAA concentrations of up to at least 1000 μg/mL (r = 0.991). Intra-assay CVs were 13, 18 and 15% at high (782 μg/mL), intermediate (116 μg/mL) and low (64 μg/mL) concentrations. Inter-assay (inter-batch) CVs were 45, 14 and 15% at high (1372 μg/mL), intermediate (140 μg/mL) and low (56 μg/mL) concentrations. SAA results in whole blood were significantly lower than those in serum/plasma (P = 0.0002), but were positively correlated (r = 0.908) and not affected by HCT (P = 0.261); proportional negative bias was observed in samples with SAA>500 μg/mL. The difference between methods exceeded the 95% confidence interval of the combined imprecision of both methods (15%).

MAIN LIMITATIONS

Analytical validation could not be performed in whole blood, the sample most likely to be used stall side.

CONCLUSION

The POC test has acceptable accuracy and precision in equine serum/plasma with SAA concentrations of up to at least 1000 μg/mL. Low inter-batch precision at high concentrations may affect serial measurements, and the use of the same test batch and sample type (serum/plasma or whole blood) is recommended. Comparison of results between the POC test and the TIA is not recommended.