Biomedical subjects

Stephen M Reed

Publications and source records attributed to Stephen M Reed.

6 recordsLinked to original sources

PubMed2004

Equine herpesvirus 1 and 4.

Equine herpesvirus infections in horses remain a significant cause of abortion and neurologic disease. These viruses are also responsible for mild signs of respiratory disease. The ability to establish latent infections with periodic reactivation or transmission to other horses is an important feature of these herpesviruses. One of the most unique aspects of this report is the description of horses demonstrating neurologic signs serving as the source of infection for other horses. Accurate diagnosis and better means of protection for horses remain problems facing veterinarians and horse owners.

Abortion, Veterinary↗

PubMed2004

Rapid sequential changeover of expressed p44 genes during the acute phase of Anaplasma phagocytophilum infection in horses.

Anaplasma phagocytophilum immunodominant polymorphic major surface protein P44s have been hypothesized to go through antigenic variation, but the within-host dynamics of p44 expression has not been demonstrated. In the present study we investigated the composition and changes of p44 transcripts in the blood during the acute phase of well-defined laboratory A. phagocytophilum infections in naive equine hosts. Three traveling waves of sequential population changeovers of the p44 transcript species were observed within a single peak of rickettsemia of less than 1 month. During the logarithmic increase, the rapid switch-off of the initial dominant transcript p44-18 occurred regardless of whether the bacterium was transmitted by ticks or by intravenous inoculation. Each of the subsequently dominant p44 transcript species was phylogenetically dissimilar from p44-18. Development of antibody to the hypervariable region of P44-18 during the rickettsemia suggests the suppression of dominance of immuno-cross-reactive p44 populations. When A. phagocytophilum was preincubated with plasma from the infected horse and then coincubated with HL-60 cells, the dominance of the p44-18 transcript was rapidly suppressed in vitro and most of the newly emerged p44 transcript species were previously undetected in this horse. This work provides experimental evidence of within-host p44 antigenic variation. Results suggest that the rapid and synchronized switch of expression is an intrinsic property of p44s reinitiated after transmission to naive mammalian hosts and shaped upon exposure to immune plasma.

Acute Disease↗

PubMed2004

Evaluation and comparison of an indirect fluorescent antibody test for detection of antibodies to Sarcocystis neurona, using serum and cerebrospinal fluid of naturally and experimentally infected, and vaccinated horses.

The objectives of this study were to evaluate the accuracy of the indirect fluorescent antibody test (IFAT) using serum and cerebrospinal fluid (CSF) of horses naturally and experimentally infected with Sarcocystis neurona, to assess the correlation between serum and CSF titers, and to determine the effect of S. neurona vaccination on the diagnosis of infection. Using receiver-operating characteristic analysis, the areas under the curve for the IFAT were 0.97 (serum) and 0.99 (CSF). Sensitivity and specificity were 83.3 and 96.9% (serum, cutoff 80) and 100 and 99% (CSF, cutoff 5), respectively. Titer-specific likelihood ratios (LRs) ranged from 0.03 to 187.8 for titers between <10 and 640. Median time to conversion was 22-26 days postinfection (DPI) (serum) and 30 DPI (CSF). The correlation between serum and CSF titers was moderately strong (r = 0.6) at 30 DPI. Percentage of vaccinated antibody-positive horses ranged from 0 to 95% between 0 and 112 days after the second vaccination. Thus, the IFAT was reliable and accurate using serum and CSF. Use of LRs potentially improves clinical decision making. Correlation between serum and CSF titers affects the joint accuracy of the IFAT; therefore, the ratio of serum to CSF titers has potential diagnostic value. The S. neurona vaccine could possibly interfere with equine protozoal myeloencephalitis diagnosis.

Animals↗

PubMed2002

Reduced levels of nitric oxide metabolites in cerebrospinal fluid are associated with equine protozoal myeloencephalitis.

Equine protozoal myeloencephalitis (EPM) is a disease of horses that is primarily associated with infection with the apicomplexan Sarcocystis neurona. Infection with this parasite alone is not sufficient to induce the disease, and the mechanism of neuropathogenesis associated with EPM has not been reported. Nitric oxide (NO) functions as a neurotransmitter, a vasodilator, and an immune effector and is produced in response to several parasitic protozoa. The purpose of this work was to determine if the concentration of NO metabolites (NO(x)(-)) in the cerebrospinal fluid (CSF) is correlated with the development of EPM. CSF NO(x)(-) levels were measured before and after transport-stressed, acclimated, or dexamethasone-treated horses (n = 3 per group) were experimentally infected with S. neurona sporocysts. CSF NO(x)(-) levels were also compared between horses that were diagnosed with EPM after natural infection with S. neurona and horses that did not have clinical signs of disease or that showed no evidence of infection with the parasite (n = 105). Among the experimentally infected animals, the mean CSF NO(x)(-) levels of the transport-stressed group, which had the most severe clinical signs, was reduced after infection, while these values were found to increase after infection in the remaining groups that had less severe signs of EPM. Under natural conditions, horses with EPM (n = 65) had a lower mean CSF NO(x)(-) concentration than clinically normal horses with antibodies (Abs) against S. neurona (n = 15) in CSF, and horses that developed ataxia (n = 81) had a significantly lower mean CSF NO(x)(-) concentration than horses that did not have neurologic signs (n = 24). In conclusion, lower CSF NO(x)(-) levels were associated with clinical EPM, suggesting that measurement of CSF NO(x)(-) levels could improve the accuracy of diagnostic tests that are based upon detection of S. neurona-specific Abs in CSF alone and that reduced NO levels could be causally related to the development of EPM.

Animals↗

PubMedDate not supplied

Technique for equine cervical articular process joint injection.

Degenerative changes and osteochondrosis of articular processes are common sources of stiffness or pain in the equine cervical spine. Temporary relief of the clinical signs related to these maladies may be achieved by injecting corticosteroids into the joint. This is routinely done by ultrasound-guided needle placement. The cervical articular processes and joint form an easily identifiable sonographic landmark, a step-like echogenic surface described as having the appearance of a "chair."

Animals↗

PubMedDate not supplied

Actinobacillus sp. bacteremia in foals: clinical signs and prognosis.

Medical records of 101 blood culture-confirmed bacteremic foals were reviewed to determine whether foals with Actinobacillus sp. bacteremia are affected at an earlier age, have more severe signs of disease, and have a worse prognosis than do foals with bacteremia of other causes. Thirty percent (30/101) of bacteremic foals had Actinobacillus sp. cultured, and these were 2 times more likely to die (crude odds ratio [OR(CR)] 0.8, 4; P = .14), with a survival rate of 43% (13/30) compared to the overall survival rate of 55% (56/101). When compared to other bacteremic foals, foals with actinobacillosis were 7 times more likely to have been sick from birth (adjusted odds ratio [OR(ADJ)] 2, 26; P = .003) and 6 times more likely to have diarrhea (OR(ADJ) 1, 22; P = .009). By bivariate analysis. foals with Actinobacillus sp. bacteremia were 5 times more likely to have a sepsis score >11 (OR(CR) 1, 18; P = .007), 6 times more likely to be obtunded (OR(CR) 2, 20; P = .005), and 3 times more likely to have pneumonia (OR(CR) 1, 7; P = .03). Furthermore, Actinobacillus sp. bacteremic foals were 27 times more likely to have a segmented neutrophil count <3.3 X 10(9) cells/L (OR(ADJ) 4, 166: P < .0001) and were 4.5 times more likely to have a band neutrophil count >0.46 x 10(9) cells/L (OR(ADJ) 1, 17; P = .02) when compared to foals that had bacteremia caused by either gram-negative enteric or gram-positive organisms. Sepsis score was < or = 11 in 49% (29/59) of bacteremia foals aged <13 days for which a discernible sepsis score was calculable. Results of this study should improve the diagnostic sensitivity of clinical examinations of neonatal foals, thereby facilitating treatment decisions.

Actinobacillosis↗