The primary source of data on bovine respiratory disease (BRD) prevalence in US adult dairy cattle is producer surveys, which estimate that 2.4–2.9% of cattle are affected. This estimate appears low when compared to calculations based on limited data regarding on-farm deaths due to BRD and the number of carcasses at slaughter with severe BRD. These calculations indicate that approximately 3% of dairy cows die on farm or go to slaughter with severe BRD. Not included in these data are cows that are treated for BRD and retained. The primary manifestation of BRD on dairy farms is in calves. Nationwide surveys have estimated that 12.4–16.4% of preweaned dairy heifer calves are affected with BRD, and 5.9–11% of calves are affected after weaning. More detailed prevalence studies have generally included a limited number of small farms, with limited calf age range studied. All studies relied on producer diagnosis. Prevalence in these studies ranged from 0 to 52%, with many cases occurring before weaning, and with BRD being associated with increased calf death rates. BRD affects heifer growth. It appears to have a small effect on age at first calving, and some studies have shown small effects on performance and herd life after calving. First lactation performance of heifers depends on many factors that can obscure the effects of calfhood BRD.

Defining the causal relationship between a microbe and encephalitis is complex. Over 100 different infectious agents may cause encephalitis, often as one of the rarer manifestations of infection. The gold-standard techniques to detect causative infectious agents in encephalitis in life depend on the study of brain biopsy material; however, in most cases this is not possible. We present the UK perspective on aetiological case definitions for acute encephalitis and extend them to include immune-mediated causes. Expert opinion was primarily used and was supplemented by literature-based methods. Wide usage of these definitions will facilitate comparison between studies and result in a better understanding of the causes of this devastating condition. They provide a framework for regular review and updating as the knowledge base increases both clinically and through improvements in diagnostic methods. The importance of new and emerging pathogens as causes of encephalitis can be assessed against the principles laid out here.

The aim of the study was to measure the positive predictive value (PPV) and sensitivity of operational case definitions of 13 syndromes in a surveillance system based on the Emergency online database of the Lazio region. The PPVs were calculated using electronic emergency department (ED) medical records and subsequent hospitalizations to ascertain the cases. Sensitivity was calculated using a modified capture–recapture method. The number of cases that fulfilled the case definition criteria in the 2004 database ranged from 27 320 for gastroenteritis to three for haemorrhagic diarrhoea. The PPVs ranged from 99·3 to 20; sepsis, meningitis-like and coma were below 50%. The estimated sensitivity ranged from 90% for coma to 22% for haemorrhagic diarrhoea. Syndromes such as gastroenteritis, where the signs, symptoms, and exposure history provide immediate diagnostic implications fit this surveillance system better than others such as haemorrhagic diarrhoea, where symptoms are not evident and a more precise diagnosis is needed.

L’épidémiologie psychiatrique s’est beaucoup développée depuis trente ans. Après avoir rappelé les définitions et méthodes fondamentales en épidémiologie, nous décrivons des progrès accomplis en épidémiologie psychiatrique. Parmi eux, la définition des cas, les techniques d’identification des cas, et la recherche de facteurs de risque sont présentés ici. Pour les illustrer, certaines connaissances actuelles sur les facteurs de risque dans la schizophrénie et la dépression sont brièvement décrits. Ensuite, les travaux en psychiatrie de l’enfant sont brièvement présentés en insistant sur quelques difficultés spécifiques à la recherche en pédopsychiatrie. Finalement, après avoir fait le point de la situation française, quelques opinions communes qui freinent l’essor de la recherche épidémiologique sont passées en revue. Les conclusions soulignent la possibilité et la nécessité de développer cette approche multi-disciplinaire en psychiatrie.