A competitive inhibition enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies in serum to the protective antigen (PA) and lethal factor (LF) components of anthrax toxin. Current human vaccination schedules with an acellular vaccine induce predictable and lasting antibody titers to PA and, when present in the vaccine, to LF. Live spore vaccines administered to guinea pigs in a single dose conferred significantly better protection than the human vaccines (P < 0.001), although they elicited significantly lower (P < 0.0005) anti-PA and anti-LF titers at time of challenge with virulent Bacillus anthracis. Substantial anti-PA and anti-LF titers may not, therefore, indicate solid protective immunity against anthrax infection. The ELISA system was also shown to be capable of detecting anti-PA and anti-LF antibodies in the sera of individuals with histories of clinical anthrax. The advantage of ELISA over the Ouchterlony gel diffusion test and indirect microhemagglutination assay are demonstrated. There was a highly significant degree of correlation between ELISA and the indirect microhemagglutination assay (P < 0.0005); but ELISA was markedly superior in terms of reproducibility, reliability, specificity, speed, and simplicity in performance and stability of the bound antigen.
Initially, 8 of 30 cows had positive CI-ELISA results. Seroconversion was detected in 4 cows. Ovine herpesvirus type 2 DNA was intermittently detected in blood, milk, nasal secretions, or ocular secretions from 17 of 30 cows. Twenty-one cows had positive CI-ELISA or PCR assay results. No cattle in the study developed clinical signs of MCF. Results of PCR assays performed on tissue samples from 2 of 18 animals submitted for necropsy were positive for OvHV-2. CONCLUSIONS AND CLINICAL RELEVANCE; OvHV-2 infection can occur in cattle without concurrent development of clinical MCF. Ovine herpesvirus type 2 DNA was detected intermittently, suggesting fluctuating viral DNA loads or reinfection in subclinical cattle. A definitive site of latency was not identified from tissues obtained during necropsy.
Abstract.A polymerase chain reaction (PCR) test was compared with culture for the detection and diagnosis of bovine Mycoplasma intramammary infection. The PCR test was applied to 24-hour Mycoplasma enrichment cultures of milk from cows with suspected mastitis and from bulk tank milk. In comparison to culture, the sensitivity and specificity of the PCR method were 96.2% and 99.1% for individual cow milk and 100% and 99.8% for the bulk tank milk, respectively. However, in discrepant cases where PCR was positive and culture was negative, the PCR test was correct; subsequent PCR tests and culturing of the individual cow's milk yielded positive results. The PCR test simultaneously detected and differentiated among 11 bovine Mycoplasma species.Mycoplasmal intramammary infection (IMI) of dairy cattle is a serious condition that can result in milk loss and elimination of infected animals from a herd. 2,6,11,12 Mycoplasmal mastitis is also difficult to treat effectively because the organism can persist despite antibiotic treatment and can lead to a chronic, subclinical state of infection. 9,10,12 Because a mycoplasmal IMI can be clinical, subclinical, or chronic, routine screening of bulk milk tanks is beneficial in detecting the presence of mycoplasmas. 3 Early detection is critical in preventing disease and spread to other herd animals. If detected in a bulk tank, individual animals can be tested and identified. Though an infected animal may not exhibit signs of clinical mastitis, a mycoplasmal IMI is still possible, and proper control procedures can be implemented upon identification of the animal.With traditional detection methods, complex media are used for the propagation and isolation of mycoplasmas. 4,7 Preparation of the medium is a tedious and time-consuming process. Subsequent subculturing for identification may take 5-10 days. 3,5,7,12 A sensitive polymerase chain reaction (PCR) test was applied to reduce the time required for detection of mycoplasmas and to identify the Mycoplasma species responsible for an outbreak. Materials and methods Organisms isolates).Specimen preparation. Milk was collected from dairy bulk milk tanks or from individual cows suspected of clinical or subclinical mastitis. Extracted milk was prepared by centrifugation after mixing a small aliquot with an equal volume of chloroform. For enrichment cultures, 100 l of milk was inoculated into 2.5 ml of modified Friis broth. 4 Broth was then incubated at 37 C for 20-24 hr in 5% CO 2 . These specimens and their dilutions were used in the PCR assay.Culturing. After 24 hr of incubation of the enrichment broth, 100 l of broth was plated on to Friis agar and incubated in 5% CO 2 at 37 C for 5 days for the development of typical Mycoplasma colonies. Species identification (M. bovis, M. bovigenitalium, M. alkalescens, M. canandense) was performed with specific (indirect) immunofluorescence. 7 Digitonin disk sensitivity testing was performed on atypical colony types to distinguish between Mycoplasma and Acholeplasma. 7 PCR. Primers were previou...
Summary Reasons for performing study: Horses vaccinated against common agents of infectious upper respiratory disease (IURD) may not have detectable serum antibody and may not be protected from clinical disease. Objectives: The objectives of this study were to 1) investigate the serological response of horses to vaccination against influenza virus (H3N8 and H7N7) and equine herpesviruses (EHV) in a field setting and 2) evaluate associations among vaccination status, serum antibody concentrations, and occurrences of IURD in monitored horses. Methods: In this study, horses on 6 Colorado premises were vaccinated parenterally against influenza virus and EHV, and serological response evaluated. Horses were monitored, and biological samples collected from individuals with clinical IURD and control horses. Results: Of 173 horses, 61 (35.3%), 21 (12.1%) and 4 (2.3%) seroconverted in response to vaccination against EHV, influenza virus H7N7 and influenza virus H3N8, respectively. Conclusions: Outbreaks of IURD in study horses were associated with influenza virus H3N8 and Streptococcus equi infection, and serological response to vaccination with conventional products was poor. Potential relevance: These results confirm that horses may not respond with detectable serological responses to conventional vaccination against common respiratory viruses and, therefore, suggest that alternate methods of protecting horses against common respiratory viruses should be sought.
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