Ingestion of immune bloodmeals and infection of Aedes fowleri, Aedes mcintoshi, and Culex pipiens with Rift Valley fever virus

Rift Valley fever (RVF) virus infection, dissemination, and transmission rates were determined for Aedes fowleri, Aedes mcintoshi and Culex pipiens 7 or 10 days after sequentially feeding to repletion on RVF virus immune hamsters and RVF viremic hamsters, or after feeding on a mixture of RVF virus immune sheep serum and RVF viremic hamster blood through a pledget. No significant differences in infection or dissemination rates were detected among Ae. fowleri and Cx. pipiens feeding to repletion on immune hamsters before or after feeding to repletion on a viremic hamster. Similarly, no significant differences in infection, dissemination, or transmission rates were observed among Ae. fowleri and Cx. pipiens feeding to repletion on immune hamsters or nonimmune (control) hamsters 0 or 24 hr after inoculation with RVF virus. Infection rates were significantly higher for Ae. fowleri (56/66, 85%) and Cx. pipiens (123/148, 83%) fed only on viremic hamsters than for those interrupted to complete feeding on an immune hamster (Ae. fowleri [24/49, 59%], Cx. pipiens [66/131, 50%]) or a nonimmune hamster (Ae. fowleri [32/51, 63%], Cx. pipiens [69/127, 54%]). However, no significant differences were detected in infection, dissemination, or transmission rates among Ae. fowleri, Ae. mcintoshi or Cx. pipiens fed on a viremic hamster and interrupted to complete feeding on an immune vs. a nonimmune hamster. Results from interrupted feeding experiments were significantly different from pledget feeding experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inter-study differences: How should they influence the interpretation and analysis of results?

In determining the role inter-study variation should play in an overview analysis, it is important to consider three factors: which question one is trying to answer; the degree of similarity or dissimilarity of design, and the degree to which heterogeneity of outcomes can be explained. Three questions one might be interested in are: whether treatment can be effective in some circumstances; whether treatment is effective on average, and whether treatment was effective on average in the trials at hand. Under the assumption of no qualitative interaction, the answers to these questions coincide. The O-E analysis most directly answers the third question. Other analyses are suggested when the first question is of interest, using the aspirin post-MI studies as an example.     

Spatial patterns of use of health services in the Kingston metropolitan area, Jamaica

This study focuses on the influence of distance, transport and accessibility on the use of health services in Kingston, Jamaica. It reviews various factors affecting the use of health care with particular reference to Third World cities and presents results from a case study of utilization in the Kingston Metropolitan Area. Three pairs of sites of contrasting social status were selected and 50 respondents questioned in each about spatial patterns of primary health care (PHC) attendance. Types of facility attended, mode of transport, travel times, distance and frequency of utilization were discussed. Some distinctive differences appeared between low and high status site respondents with regard to distances to facilities and travel times, which were almost always higher for the low status respondents. Most respondents were not using their nearest facilities, for varying reasons which included, for poorer respondents, need to attend frequently distant public facilities and, for wealthier respondents, loyalty to old family doctors and use of company-related doctors. The mobility of the higher status respondents afforded them considerable choice of locations used for health care and their attendance was much more convenient than that of lower status respondents. Utilization rates were somewhat higher in the high status sites although not to the extent found by some earlier studies in similar settings.     

Negative symptoms in schizophrenia: considerations for clinical trials

There is little agreement about the methodology of clinical trials of antipsychotic drugs in patients with negative symptoms. A literature review revealed wide variation in experimental design, rating scales and study duration. This reflects differing views as to the definition and response to treatment of negative symptoms. Some degree of standardization would improve comparability of studies and aid the development of new compounds. Patients included in such studies should have displayed negative symptoms for at least 6 months. Depressive symptoms, positive schizophrenic symptoms and extrapyramidal signs may all influence or be confused with negative symptoms and may respond to treatment; they should be at a low level at baseline and should be measured during the study period. Studies should last at least 8 weeks. Several scales are available for measuring negative symptoms and are reviewed; a global impression score should be used additionally.