Epidemiological implications of the contact network structure for cattle farms and the 20-80 rule

The network of movements of cattle between farm holdings is an important determinant of the potential rates and patterns of spread of infectious diseases. Because cattle movements are uni-directional, the network is unusual in that the risks of acquiring infection (by importing cattle) and of passing infection on (by exporting cattle) can be clearly distinguished, and there turns out to be no statistically significant correlation between the two. This means that the high observed degree of heterogeneity in numbers of contacts does not result in an increase in the basic reproduction number, R0, in contrast to findings from studies of other contact networks. Despite this, it is still the case that just 20% of holdings contribute at least 80% of the value of R0.     

Regulation of endocytic traffic by rho family GTPases

Endocytosis is a complicated yet highly efficient process that involves the uptake and processing of cargoes, ranging from small molecules, to activated signalling receptors, to whole microorganisms. Regulation of endocytic pathways is poorly understood. Recent evidence suggests that the Rho GTPase family of signalling proteins is intimately involved in endocytic traffic, providing novel insights into the control mechanisms that govern this process.     

The novel Rho-family GTPase rif regulates coordinated actin-based membrane rearrangements

Small GTPases of the Rho family have a critical role in controlling cell morphology, motility and adhesion through dynamic regulation of the actin cytoskeleton [1,2]. Individual Rho GTPases have been shown to regulate distinct components of the cytoskeletal architecture; RhoA stimulates the bundling of actin filaments into stress fibres [3], Rac reorganises actin to produce membrane sheets or lamellipodia [4] and Cdc42 causes the formation of thin, actin-rich surface projections called filopodia [5]. We have isolated a new Rho-family GTPase, Rif (Rho in filopodia), and shown that it represents an alternative signalling route to the generation of filopodial structures. Coordinated regulation of Rho-family GTPases can be used to generate more complicated actin rearrangements, such as those underlying cell migration [6]. In addition to inducing filopodia, Rif functions cooperatively with Cdc42 and Rac to generate additional structures, increasing the diversity of actin-based morphology.     

The Most Likely Time and Place of Introduction of BTV8 into Belgian Ruminants

Background

In northern Europe, bluetongue (BT) caused by the BT virus (BTV), serotype 8, was first notified in August 2006 and numerous ruminant herds were affected in 2007 and 2008. However, the origin and the time and place of the original introduction have not yet been determined.

Methods and Principal Findings

Four retrospective epidemiological surveys have been performed to enable determination of the initial spatiotemporal occurrence of this emerging disease in southern Belgium: investigations of the first recorded outbreaks near to the disease epicenter; a large anonymous, random postal survey of cattle herds and sheep flocks; a random historical milk tank survey of samples tested with an indirect ELISA and a follow-up survey of non-specific health indicators. The original introduction of BTV into the region probably occurred during spring 2006 near to the National Park of Hautes Fagnes and Eifel when Culicoides become active.

Conclusions/Significance

The determination of the most likely time and place of introduction of BTV8 into a country is of paramount importance to enhance awareness and understanding and, to improve modeling of vector-borne emerging infectious diseases.     

The Spread of Bluetongue Virus Serotype 8 in Great Britain and Its Control by Vaccination

Background

Bluetongue (BT) is a viral disease of ruminants transmitted by Culicoides biting midges and has the ability to spread rapidly over large distances. In the summer of 2006, BTV serotype 8 (BTV-8) emerged for the first time in northern Europe, resulting in over 2000 infected farms by the end of the year. The virus subsequently overwintered and has since spread across much of Europe, causing tens of thousands of livestock deaths. In August 2007, BTV-8 reached Great Britain (GB), threatening the large and valuable livestock industry. A voluntary vaccination scheme was launched in GB in May 2008 and, in contrast with elsewhere in Europe, there were no reported cases in GB during 2008.

Methodology/Principal Findings

Here, we use carefully parameterised mathematical models to investigate the spread of BTV in GB and its control by vaccination. In the absence of vaccination, the model predicted severe outbreaks of BTV, particularly for warmer temperatures. Vaccination was predicted to reduce the severity of epidemics, with the greatest reduction achieved for high levels (95%) of vaccine uptake. However, even at this level of uptake the model predicted some spread of BTV. The sensitivity of the predictions to vaccination parameters (time to full protection in cattle, vaccine efficacy), the shape of the transmission kernel and temperature dependence in the transmission of BTV between farms was assessed.

Conclusions/Significance

A combination of lower temperatures and high levels of vaccine uptake (>80%) in the previously-affected areas are likely to be the major contributing factors in the control achieved in England in 2008. However, low levels of vaccination against BTV-8 or the introduction of other serotypes could result in further, potentially severe outbreaks in future.     

In vitro synthesis of estrogen glucuronides and sulfates by human renal tissue.

17beta-[6,7-3H]Estradiol (E2) was incubated with slices and homogenates of adult human renal tissue. The metabolites formed were identified by chromatography on DEAE-Sephadex, thin layer chromatography and crystallization with carrier steroids or steroid derivatives. The major metabolites formed by slices were estradiol-17-glucuronide (E217G), estrone sulfate and estradiol-3-sulfate. This is the first report of in vitro synthesis of estrogen sulfates by adult renal tissue. Minor quantities of the 3-glucuronides of estrone and estradiol were also found. An oxygen atmosphere appeared to stimulate the production of E217G. A time study with tissue slices showed similarities between the in vitro pattern of glucuronide synthesis and the excretion pattern of these compounds seen in earlier in vivo studies. Homogenates fortified with uridine diphosphoglucuronic acid formed the same pattern of glucuronide products but in lesser amounts. No sulfates were formed under these conditions. Testosterone did not act as a substrate in the experimental conditions used.