A mathematical model of the effects of chronic carriers on the within-herd spread of contagious bovine pleuropneumonia in an African mixed crop-livestock system

Contagious bovine pleuropneumonia (CBPP) is a respiratory disease of cattle; CBPP is caused by Mycoplasma mycoides subsp. mycoides small colony. CBPP is a major cause for concern for African countries (because of mortality, animal-production losses and cost of control). The clinical form of the disease is the more infectious (contagion occurs essentially through coughing). However, chronic lung lesions with viable mycoplasmas can persist in recovering cattle. Animals presenting these lesions might have a time-delimitated infectious phase. Such carriers are suspected to generate field outbreaks (although this hypothesis remains debated). We investigated the potential quantitative effects of these chronic carriers on the within-herd CBPP spread. Data were collected during a longitudinal field herd survey in a mixed crop-livestock system in the Ethiopian highlands. Two stochastic Markov-chain models' outputs (seroconversion dynamics, basic reproduction ratio R0, cumulative clinical incidence and risk of herd infection) were compared given different hypotheses on the carrier infectiousness. The late seroconversions observed in the field data were fitted correctly only for the highest carrier infectiousness we considered (mean chronic duration of 1 year and carriers 50-times less infectious than clinical cases). Although sensitivities (in terms of disease impact in the herd) were in general negligible when the carrier infectiousness was low (e.g. when carriers were assumed to be 1000-times less infectious than clinical cases), they rapidly became important when the infectiousness increased.     

Cladosporium Avr2 inhibits tomato Rcr3 protease required for Cf-2-dependent disease resistance

How plants recognize pathogens and activate defense is still mysterious. Direct interaction between pathogen avirulence (Avr) proteins and plant disease resistance proteins is the exception rather than the rule. During infection, Cladosporium fulvum secretes Avr2 protein into the apoplast of tomato leaves and, in the presence of the extracellular leucine-rich repeat receptor-like Cf-2 protein, triggers a hypersensitive response (HR) that also requires the extracellular tomato cysteine protease Rcr3. We show here that Avr2 binds and inhibits Rcr3 and propose that the Rcr3-Avr2 complex enables the Cf-2 protein to activate an HR.     

Current-induced spin-wave Doppler shift

Spin transfer appears to be a promising tool for improving spintronics devices. Experiments that quantitatively access the magnitude of the spin transfer are required for a fundamental understanding of this phenomenon. By inductively measuring spin waves propagating along a permalloy strip subjected to a large electrical current, we observed a current-induced spin wave Doppler shift that we relate to the adiabatic spin transfer torque. Because spin waves provide a well-defined system for performing spin transfer, we anticipate that they could be used as an accurate probe of spin-polarized transport in various itinerant ferromagnets.     

Correlates of diet quality in the Quebec population

OBJECTIVE: To determine the correlates of a high-fat diet in urban, suburban and rural areas of Quebec, Canada. DESIGN: A secondary analysis of data collected as part of a 5-year multi-factorial, multi-setting, community-intervention project. SETTING: Urban, suburban and rural settings of the province of Quebec, 1997. SUBJECTS: Data were analysed from a sample of 5214 participants (2227 males, 2987 females). A food-frequency questionnaire was completed and a global index of food quality was calculated. Logistic regression was used to identify correlates of a diet high in total fats, saturated fat and cholesterol. RESULTS: In both genders, lower level of education, smoking status, French and English languages compared with other languages spoken at home, and a rural environment were associated with poor diet quality. Having no intention to eat low-fat dairy products more often was associated with a high-fat diet. In men, obesity (body mass index >/=30 kg m(-2)) and absence of reported health problems were correlates of a high-fat diet, while, in women, lower physical activity was a correlate. CONCLUSIONS: Future health interventions in Quebec should target people with low education, smokers and those living in a rural environment. Obese men and sedentary women should have access to specific dietetic resources.     

Changes in soil faunal assemblages during conversion from pure to mixed forest stands

Replacement of native deciduous forests by coniferous stands was a common consequence of former European afforestation policies. However, these changes have proven to lead to serious ecological problems. Therefore, re-establishing mixed forests with native tree species became an increasingly popular management strategy to fulfil the demands of multi-functional forestry. We report about changes in collembolan assemblages and microbial performances during conversion of pure coniferous stands to mixed forests. The study was carried out in the Black forest area (SW of Germany), where a gradient of conversion from pure spruce stands (S1) to equally mixed stands (spruce, beech, and fir) at S4, through two intermediate stages (S2 and S3) was selected. Results clearly indicated strong modifications of the collembolan communities with an enrichment of the assemblages over the course of the conversion process. Mean species richness increased by 47% from S1 to S4 accompanied by diversity indices (Shannon and Simpson) higher at S4. Significantly different soil biota assemblages were found at each phase of the conversion process. Spatial turnover and nestedness contribute almost equally to the modification of assemblages from S1 to S2 while later on in the mixing process only spatial turnover was acting. Concomitantly, significant shifts in the functional structure of the collembolan assemblages were depicted, deep-dwelling collembolan (euedaphic) being, surprisingly, the most responsive group. In contrast, neither microbial nor coarse environmental parameters were influenced by the factor “conversion phase”. We suggest that stimulation of Collembolan communities after the mixing process was mainly due to the input of more suitable food sources and/or microhabitat increases. Our findings underline the crucial role of aboveground processes on the belowground system, with the intensity and scheme of the mixing-process as important factors to consider when aiming at soil biodiversity improvement in forest systems.     

Comparison of medial and lateral ultrasound-guided approaches for periarticular injection of the thoracolumbar intervertebral facet joints in horses

Objective: To compare ultrasound‐guided lateral and medial approaches for periarticular injections of the thoracolumbar intervertebral facet joints (IFJ). Study Design: Experimental cadaveric study. Sample Population: Adult equine cadavers (n=4). Methods: IFJ (T12–T13 to L5–L6) were identified by ultrasound (transducer perpendicular to the spine axis) and insertion of a 13 cm, 18 g spinal needle monitored until bone contact using medial (right side) and lateral (left side) approaches. Number of needle insertions at each site, needle repositioning, and insertion depth were recorded. On bone contact 2 mL latex was injected. Intraarticular deposition, distance of latex from the closest articular margin, and presence of latex in the multifidus muscle were established by dissection. Results: Of 96 attempts, only 1 site require reinsertion of the needle; however, 46% of the injections required needle repositioning. Mean ± SD insertion depth was 8.5 ± 1.1 cm. Most injections (86%) were intraarticular and 96% were at or within 0.5 cm of the closest articular margin. Needle insertion relative to the transducer (lateral, medial) had no effect on the distance from the latex to the closest articular margin and all injections were performed into the multifidus muscle. Conclusions: Ultrasound‐guidance facilitated accurate periarticular injection of thoracolumbar IFJ irrespective of using a medial or lateral approach.     

Functional genomics analysis of plant growth-promoting rhizobacterial traits involved in rhizosphere competence

In soil, some specific bacterial populations, called plant growth-promoting rhizobacteria are able to promote plant growth and/or reduce the incidence of soil-borne diseases. Rhizosphere competence is an important prerequisite for the efficacy of these biocontrol strains. Therefore, over decades, multiple approaches have been combined to understand the molecular basis of bacterial traits involved in rhizosphere competence. This review addresses the bacterial genes expressed during bacterial–plant interactions in the rhizosphere of different plant species. The distribution of these key genes in natural populations of rhizobacteria is also discussed.     

Diversity and distribution of pathotypes of the soybean rust fungus Phakopsora pachyrhizi in East Africa

Phakopsora pachyrhizi is a biotrophic fungus that causes rust on soybean, leading to devastating yield losses. Development of resistant cultivars for deployment in different geographic regions requires a comprehensive understanding of the prevalent P. pachyrhizi pathotypes. To determine the pathotypes existing in four East African countries, 65 isolates were tested on 11 soybean host differentials. In addition, the virulence spectrum of isolates collected from the same region over multiple years was compared. The majority of the isolates (54%) belonged to pathotype 1000, which was found in all countries. The pathotypes with the most complex virulence spectrum, which comprised isolates from Kenya and Malawi, were virulent on four differentials. All pathotypes were virulent on soybean genotypes carrying the Rpp1 resistance gene to P. pachyrhizi, but they were avirulent on cultivars carrying the Rpp1b, Rpp2, or Rpp3 gene, as well as on cultivar No6-12-1 that carries Rpp2, Rpp4, and Rpp5. Two of the pathotypes were virulent on cultivar UG 5 that carries Rpp1 and Rpp3 and on Hyuuga that carries Rpp3 and Rpp5. The isolates collected from different countries differed in their virulence spectrum across the years. Shannon's index (H) and Simpson's index (S) of diversity indicated that the isolates from Malawi were more diverse (H = 1.55, S = 0.90) while those from Uganda had lower diversity (H = 0.78, S = 0.46 ). The Rpp genes that were found to provide resistance to all pathotypes of P. pachyrhizi can be employed for soybean breeding aimed at durable rust resistance.