Estimation of the specificity of an antibody ELISA for paratuberculosis generated from a sector of the UK cattle population using results from a paratuberculosis control programme.

In the United Kingdom (UK) a voluntary programme to control paratuberculosis in cattle based on herd management and serological screening has been operating since 1998. The programme assigns a risk level to each participating herd according to the within herd seroprevalence and the confirmation of the presence of infection with Mycobacterium avium subspecies paratuberculosis (MAP) by faecal culture or polymerase chain reaction (PCR). From the outset a general concern over the specificity of the paratuberculosis antibody enzyme-linked immunosorbent assay (ELISA) resulted in the use of a faecal screen for the causal organism to negate or confirm infection in individual seropositive animals. Progress in improving the diagnostic tests has been gradual throughout the life of the programme and the under-pinning approach to using tests to determine the risk of paratuberculosis for a herd required to be re-examined. This study used a large data set of more than 143,000 test results over five years from the lowest paratuberculosis risk level category of herds to estimate the specificity of a commercially available paratuberculosis antibody ELISA for cattle. In each year of the study the estimated specificity reached or exceeded 0.998. We also examined the apparent impact that annual or more frequent application of the single intradermal comparative cervical tuberculin (SICCT) test for tuberculosis (TB), using purified protein derivatives of Mycobacterium bovis and Mycobacterium avium subspecies avium, had on specificity of the antibody ELISA for paratuberculosis. We found a statistically significant difference in three of the five years with herds that were officially tuberculosis free and not subject to frequent SICCT testing. This difference was small and considered to be of little practical importance for the paratuberculosis assurance programme. We concluded that, in the UK the mandatory TB surveillance programme of cattle herds is not a limiting factor in the use of serological testing to support herd-level assurance schemes for paratuberculosis. Furthermore, in paratuberculosis, where shedding of MAP is intermittent and the sensitivity of the commercially available PCR tests for detection MAP is highly variable, faecal screening of seropositive animals is an unreliable method for negating infection in seropositive cattle.

Mannheimia haemolytica serovars associated with respiratory disease in cattle in Great Britain.

BACKGROUND: Mannheimia haemolytica is commonly associated with respiratory disease in cattle worldwide as a cause of fibrinous pneumonia, bronchopneumonia and pleuritis. M. haemolytica is further subdivided into 12 serovars, however not all are considered to be pathogenic in cattle. The study aim was to determine the most common serovars of M. haemolytica associated with respiratory disease in cattle in Great Britain, which is currently unknown and could be useful information for clinicians when considering preventative strategies. RESULTS: One hundred four M. haemolytica isolates isolated from bovine clinical pathology and post-mortem samples from pneumonia cases between 2016 and 2018 were tested using a multiplex PCR assay to identify M. haemolytica serovars A1, A2 and A6. 46 isolates (44.2%) typed as M. haemolytica serovar A1, 31 (29.8%) as M. haemolytica serovar A2 and 18 isolates (17.3%) as M. haemolytica serovar A6. Nine isolates (8.7%) were not A1, A2 or A6 so were considered to belong to other serovars or were not typable. CONCLUSION: This study highlights the importance of M. haemolytica serovars other than A1 which may be responsible for respiratory disease in cattle and could help guide the veterinarian when making choices on preventative vaccination programmes.

A Geography-Specific Approach to Estimating the Distributional Impact of Highway Tolls: An Application to the Puget Sound Region of Washington State.

This study contributes to the debate about tolls' equity impacts by examining the potential economic costs of tolling for low-income and non-low-income households. Using data from the Puget Sound metropolitan region in Washington State and GIS methods to map driving routes from home to work, we examine car ownership and transportation patterns among low-income and non-low-income households. We follow standard practice of estimating tolls' potential impact only on households with workers who would drive on tolled and non-tolled facilities. We then redo the analysis including broader groups of households. We find that the degree of regressivity is quite sensitive to the set of households included in the analysis. The results suggest that distributional analyses of tolls should estimate impacts on all households in the relevant region in addition to impacts on just users of roads that are currently tolled or likely to be tolled.

Cell division activity determines the magnitude of phosphate starvation responses in Arabidopsis.

Phosphate (P(i)) is a major limiting factor for plant growth. Plants respond to limiting P(i) supplies by inducing a suite of adaptive responses comprising altered growth behaviour, enhanced P(i) acquisition and reduced P(i) demand that together define a distinct physiological state. In P(i)-starved plants, continued root growth is required for P(i) acquisition from new sources, yet meristem activity consumes P(i). Therefore, we analysed the relationship between organ growth, phosphate starvation-responsive (PSR) gene expression and P(i) content in Arabidopsis thaliana under growth-promoting or inhibitory conditions. Induction of PSR gene expression after transfer of plants to P(i)-depleted conditions quantitatively reflects prior levels of P(i) acquisition, and hence is sensitive to the balance of P(i) supply and demand. When plants are P(i)-starved, enhanced root or shoot growth exacerbates, whereas growth inhibition suppresses, P(i) starvation responses, suggesting that the magnitude of organ growth activity specifies the level of P(i) demand. Inhibition of cell-cycle activity, but not of cell expansion or cell growth, reduces P(i) starvation-responsive gene expression. Thus, the level of cell-cycle activity specifies the magnitude of P(i) demand in P(i)-starved plants. We propose that cell-cycle activity is the ultimate arbiter for P(i) demand in growing organs, and that other factors that influence levels of PSR gene expression do so by affecting growth through modulation of meristem activity.