The Phylogeography of Rabies in Grenada,West Indies,and Implications for Control

In Grenada, West Indies, rabies is endemic, and is thought to be maintained in a wildlife host, the small Indian mongoose (Herpestes auropunctatus) with occasional spillover into other hosts. Therefore, the present study was undertaken to improve understanding of rabies epidemiology in Grenada and to inform rabies control policy. Mongooses were trapped island-wide between April 2011 and March 2013 and examined for the presence of Rabies virus (RABV) antigen using the direct fluorescent antibody test (dFAT) and PCR, and for serum neutralizing antibodies (SNA) using the fluorescent antibody virus neutralization test (FAVN). An additional cohort of brain samples from clinical rabies suspects submitted between April 2011 and March 2014 were also investigated for the presence of virus. Two of the 171 (1.7%) live-trapped mongooses were RABV positive by FAT and PCR, and 20 (11.7%) had SNAs. Rabies was diagnosed in 31 of the submitted animals with suspicious clinical signs: 16 mongooses, 12 dogs, 2 cats and 1 goat. Our investigation has revealed that rabies infection spread from the northeast to the southwest of Grenada within the study period. Phylogenetic analysis revealed that the viruses from Grenada formed a monophyletic clade within the cosmopolitan lineage with a common ancestor predicted to have occurred recently (6–23 years ago), and are distinct from those found in Cuba and Puerto Rico, where mongoose rabies is also endemic. These data suggest that it is likely that this specific strain of RABV was imported from European regions rather than the Americas. These data contribute essential information for any potential rabies control program in Grenada and demonstrate the importance of a sound evidence base for planning interventions.     

Modification of the interactions of myosin with actin and 5''-adenylyl imidodiphosphate by substitution of ethylene glycol for water.

We studied the effect of replacing water by ethylene glycol as solvent on the properties of skeletal muscle myosin, myosin subfragment-1 (S1) and heavy meromyosin. Ethylene glycol (50%, v/v) had no detectable effect on the affinity of myosin or actomyosin for the substrate analogue 5'-adenylyl imidodiphosphate (AMPPNP). However, the rate constants for formation and dissociation of the myosin X MgAMPPNP complex were reduced 200-fold; the logarithm of the dissociation rate was roughly proportional to the fractional concentration of ethylene glycol. Nucleotide dissociation was accelerated at least 300-fold by pure actin but remained slow with regulated actin in the absence of Ca2+. Ethylene glycol substitution reduced the affinity of S1 and the S1 X MgAMPPNP complex for actin equally (100-fold at 50% ethylene glycol). These results show that ethylene glycol has specific effects on myosin's enzymic mechanism, which can account for its effect on the tension and stiffness of glycerinated muscle fibres.     

The dissociation constant of the actin-heavy meromyosin subfragment-1 complex.

We measured the binding of [14C]iodoacetamide labeled heavy meromyosin subfragment-1 (S-1) to F-actin by sedimenting the actin-S-1 complex and assaying the radioactivity remaining in the supernatant. The apparent dissociation constants (Kd) at 25 degrees, pH 7.0, were 0.01 to 0.04 muM at 0.027 and 0.08 ionic strengths and 0.07 to 0.14 muM at 0.14 ionic strength. Kd was not altered when the troponin-tropomyosin complex was bound on the actin, nor was it affected by free calcium concentration in the range 10(-4) to 10(-9) M. Measurements of the displacement of labeled S-1 from actin by native S-1 showed labeling had not altered Kd. In control experiments we found that at the low actin concentrations used (0.001-0.5 muM) not all of the actin sedimented and, furthermore, the data suggested that some of the S-1 in the supernatant was bound to supernatant actin. Our estimation of Kd, based on the assumption that all the supernatant S-1 was free, therefore resulted in an apparent Kd greater than the true Kd. We minimized the effect of the supernatant actin artefact by using only the data for high ratios of S-1 to actin, where no less than 75% of the actin sedimented; we estimate that the true Kd values could not be less than half the apparent Kd values.     

Modelling local and global effects on the risk of contracting Tuberculosis using stochastic Markov-chain models

For some diseases, the transmission of infection can cause spatial clustering of disease cases. This clustering has an impact on how one estimates the rate of the spread of the disease and on the design of control strategies. It is, however, difficult to assess such clustering, (local effects on transmission), using traditional statistical methods. A stochastic Markov-chain model that takes into account possible local or more dispersed global effects on the risk of contracting disease is introduced in the context of the transmission dynamics of tuberculosis. The model is used to analyse TB notifications collected in the Asembo and Gem Divisions of Nyanza Province in western Kenya by the Kenya Ministry of Health/National Leprosy and Tuberculosis Program and the Centers for Disease Control and Prevention. The model shows evidence of a pronounced local effect that is significantly greater than the global effect. We discuss a number of variations of the model which identify how this local effect depends on factors such as age and gender. Zoning/clustering of villages is used to identify the influence that zone size has on the model’s ability to distinguish local and global effects. An important possible use of the model is in the design of a community randomised trial where geographical clusters of people are divided into two groups and the effectiveness of an intervention policy is assessed by applying it to one group but not the other. Here the model can be used to take the effect of case clustering into consideration in calculating the minimum difference in an outcome variable (e.g. disease prevalence) that can be detected with statistical significance. It thereby gauges the potential effectiveness of such a trial. Such a possible application is illustrated with the given time/spatial TB data set.     

A method for covalent insertion of mercury into the cysteine disulfide bridges of proteins

A method is described by which atomic mercury can be taken up by thiol groups and inserted into the disulfide bridges of proteins which can be reversibly reduced and denatured. The method utilizes tandem columns of Sephadex G-10 and Biogel P2. Protein samples are separated from reducing and denaturing agent on the Sephadex column and then react with mercury, which is bound to the Biogel P2 column. Of eight proteins tested, all took up mercury using this method. The amount of mercury incorporated by this method differed from that found using other methods and was closer to the stoichiometry of the disulfide bridges of the protein than these methods.     

Screening Global Positioning System Location Data for Errors Using Animal Movement Characteristics

Abstract: Animal locations estimated by Global Positioning System (GPS) inherently contain errors. Screening procedures used to remove large positional errors often trade data accuracy for data loss. We developed a simple screening method that identifies locations arising from unrealistic movement patterns. When applied to a large data set of moose (Alces alces) locations, our method identified virtually all known errors with minimal loss of data. Thus, our method for screening GPS data improves the quality of data sets and increases the value of such data for research and management.