Taxonomic anxieties: Axis I and Axis II in prison

This essay describes the use of the Diagnostic and Statistical Manual of Psychiatry in the prison setting. The distinction between the Axis I disorders (major mental illness) and those designated Axis II (character disorders) is explored in terms of the professional division of labor in prison and the problems posed for prison discipline by "behaviorally disturbed" inmates. Conflicts over diagnosis are placed in ethnographic and historical perspective and form the basis for a discussion of the problematic relationship between disciplinary space and issues of subjection and agency.     

Heroin epidemics, treatment and ODE modelling

The UN [United Nations Office on Drugs and Crime (UNODC): World Drug Report, 2005, vol. 1: Analysis. UNODC, 2005.], EU [European Monitoring Centre for Drugs and Drug Addiction (EMCDDA): Annual Report, 2005.http://annualreport.emcdda.eu.int/en/home-en.html.] and WHO [World Health Organisation (WHO): Biregional Strategy for Harm Reduction, 2005-2009. HIV and Injecting Drug Use. WHO, 2005.] have consistently highlighted in recent years the ongoing and persistent nature of opiate and particularly heroin use on a global scale. While this is a global phenomenon, authors have emphasised the significant impact such an epidemic has on individual lives and on society. National prevalence studies have indicated the scale of the problem, but the drug-using career, typically consisting of initiation, habitual use, a treatment-relapse cycle and eventual recovery, is not well understood. This paper presents one of the first ODE models of opiate addiction, based on the principles of mathematical epidemiology. The aim of this model is to identify parameters of interest for further study, with a view to informing and assisting policy-makers in targeting prevention and treatment resources for maximum effectiveness. An epidemic threshold value, R(0), is proposed for the drug-using career. Sensitivity analysis is performed on R(0) and it is then used to examine the stability of the system. A condition under which a backward bifurcation may exist is found, as are conditions that permit the existence of one or more endemic equilibria. A key result arising from this model is that prevention is indeed better than cure.     

Collapsing fish stocks,gendered economies,and anxieties of entrapment in coastal Sierra Leone

This article explores the economic negotiations between Sierra Leonean fishermen and the women who compete to buy their fish, tracing how relationships of gendered intimacy and interdependence are being reconfigured in a context of deepening economic precarity. Fish stocks in Sierra Leone are in crisis. Fisherfolk look back with nostalgia to a past in which bountiful harvests had made it possible for transactions of fish to be simple and impersonal. Today, by contrast, it is almost impossible for women to access fish without working to develop strong personal relationships with fishermen: deploying gifts of food, loans of money, and even secret ‘medicines’ to secure the loyalty of potential customers. I analyse how men and women reflect on their growing impoverishment through discourses that emphasize their moral ambivalence at being drawn back into webs of interpersonal dependency, and argue that these anxieties need to be understood in the context of Sierra Leone's history of domestic slavery.     

Networks, epidemics and vaccination through contact tracing

We consider a (social) network whose structure can be represented by a simple random graph having a pre-specified degree distribution. A Markovian susceptible-infectious-removed (SIR) epidemic model is defined on such a social graph. We then consider two real-time vaccination models for contact tracing during the early stages of an epidemic outbreak. The first model considers vaccination of each friend of an infectious individual (once identified) independently with probability ρ. The second model is related to the first model but also sets a bound on the maximum number an infectious individual can infect before being identified. Expressions are derived for the influence on the reproduction number of these vaccination models. We give some numerical examples and simulation results based on the Poisson and heavy-tail degree distributions where it is shown that the second vaccination model has a bigger advantage compared to the first model for the heavy-tail degree distribution.     

Heterogeneous network epidemics: real-time growth,variance and extinction of infection

Journal of Mathematical Biology - Recent years have seen a large amount of interest in epidemics on networks as a way of representing the complex structure of contacts capable of spreading...     

Primitivist medicine and capitalist anxieties in ayahuasca tourism Peru

Analysing healing practices at an ayahuasca tourism centre in Peru, this article illustrates how Shipibo practices of curing and sorcery have adapted to the demands of international clients searching for primitivist healing experiences. At the core of this adaption is the thorny issue of occult power and its relation to capital accumulation. Sorcery here does not serve clients but is manifest among healers working to capitalize on the guests’ primitivist rejections of modern life while operating in environments of economic scarcity and ambient poverty. Ayahuasca tourists do not request and generally do not believe in sorcery, but their very presence generates and negates the local moral economy of sorcery in novel ways. The article explores a paradoxical aspect of ayahuasca tourism wherein guests purge similar anxious desires for capital accumulation that healers achieve when curing them.     

Critical thresholds in sea lice epidemics: evidence, sensitivity and subcritical estimation

Host density thresholds are a fundamental component of the population dynamics of pathogens, but empirical evidence and estimates are lacking. We studied host density thresholds in the dynamics of ectoparasitic sea lice (Lepeophtheirus salmonis) on salmon farms. Empirical examples include a 1994 epidemic in Atlantic Canada and a 2001 epidemic in Pacific Canada. A mathematical model suggests dynamics of lice are governed by a stable endemic equilibrium until the critical host density threshold drops owing to environmental change, or is exceeded by stocking, causing epidemics that require rapid harvest or treatment. Sensitivity analysis of the critical threshold suggests variation in dependence on biotic parameters and high sensitivity to temperature and salinity. We provide a method for estimating the critical threshold from parasite abundances at subcritical host densities and estimate the critical threshold and transmission coefficient for the two epidemics. Host density thresholds may be a fundamental component of disease dynamics in coastal seas where salmon farming occurs.     

Bionomic studies of Cavernicola lenti Barrett & Arias, 1985 (Hemiptera, Reduviidae, Triatominae)

In the biological study, the development of the biological cycle of the insect under different feeding conditions was evaluated. The insects were fed on either mouse blood (c) or pigeon blood (p) using two types of rearing techniques (individual or group) at 28 degrees C and 90% relative humidity (which is equivalent to their natural environment). A fifth cycle studied, was fed on mouse blood reared on group, and maintained at laboratory environmental temperature. In the five cycles analyzed, it was found that groups on mouse blood at near natural conditions developed more rapidly (between 60 and 73 days) and had a lower rate of mortality (16.66%). The daily handling and changes in environment, of the individually reared insects, for observation of biological characteristics (no. and duration of bloodmeal, defecation and first fed of each stage) had a negative influence. None of the individuals fed on mouse or pigeon blood reached adult hood. It was found that the longevity and the fertility rate were significantly superior on couples maintained individually on mouse blood. These males had an average lifespan of 110.26 days and the females had an average lifespan of 104.46 days. The average number of eggs laid by each female was 21.26. Four couples kept in groups (five couples in each group) under the same condition, the longevity for males was 51.86 days and for females was 81.06 days. An average of 10.5 eggs were laid by each female. However, the percentage of fertile eggs was higher in couples kept in groups (72.15%) than in the individual couples (57.68%).     

New diversity,old anxieties in New Zealand: the complex identity politics and engagement of a settler society

Superdiversity signals the common experience in many countries and cities of the enhanced levels of diversity that are associated with contemporary immigration, yet there are a range of permutations and possibilities. One example of superdiversity – that of a particular group of settler societies represented by New Zealand – is explored, as the colonization of indigenous peoples has occurred alongside a nation-building project that centres on mass immigration, and which in turn has been layered by a more recent immigrant recruitment project that ostensibly values immigrants for the skills that they contribute to economic development. Since the 1970s, there have been limited but still important concessions made in terms of diversity recognition and group rights. This article explores the nature of this settler society superdiversity and its politics.     

From heroin epidemics to methamphetamine epidemics: Modelling substance abuse in a South African province

The global rise in the use of methamphetamine has been documented to have reached epidemic proportions. Researchers have focussed on the social implications of the epidemic. A typical drug use cycle consists of concealed drugs use after initiation, addiction, treatment-recovery-relapse cycle, whose dynamics are not well understood. The model by White and Comiskey [41], on heroin epidemics, treatment and ODE modelling, is modified to model the dynamics of methamphetamine use in a South African province. The analysis of the model is presented in terms of the methamphetamine epidemic threshold R₀. It is shown that the model has multiple equilibria and using the center manifold theory, the model exhibits the phenomenon of backward bifurcation where a stable drug free equilibrium co-exists with a stable drug persistent equilibrium for a certain defined range of R₀. The stabilities of the model equilibria are ascertained and persistence conditions established. Furthermore, numerical simulations are performed; these include fitting the model to the available data on the number of patients with methamphetamine problems. The implications of the results to drug policy, treatment and prevention are discussed.     

The epidemics of donations: logistic growth and power-laws

This paper demonstrates that collective social dynamics resulting from individual donations can be well described by an epidemic model. It captures the herding behavior in donations as a non-local interaction between individual via a time-dependent mean field representing the mass media. Our study is based on the statistical analysis of a unique dataset obtained before and after the tsunami disaster of 2004. We find a power-law behavior for the distributions of donations with similar exponents for different countries. Even more remarkably, we show that these exponents are the same before and after the tsunami, which accounts for some kind of universal behavior in donations independent of the actual event. We further show that the time-dependent change of both the number and the total amount of donations after the tsunami follows a logistic growth equation. As a new element, a time-dependent scaling factor appears in this equation which accounts for the growing lack of public interest after the disaster. The results of the model are underpinned by the data analysis and thus also allow for a quantification of the media influence.     

Stochastic epidemics in dynamic populations: quasi-stationarity and extinction

Empirical evidence shows that childhood diseases persist in large communities whereas in smaller communities the epidemic goes extinct (and is later reintroduced by immigration). The present paper treats a stochastic model describing the spread of an infectious disease giving life-long immunity, in a community where individuals die and new individuals are born. The time to extinction of the disease starting in quasi-stationarity (conditional on non-extinction) is exponentially distributed. As the population size grows the epidemic process converges to a diffusion process. Properties of the limiting diffusion are used to obtain an approximate expression for τ, the mean-parameter in the exponential distribution of the time to extinction for the finite population. The expression is used to study how τ depends on the community size but also on certain properties of the disease/community: the basic reproduction number and the means and variances of the latency period, infectious period and life-length. Effects of introducing a vaccination program are also discussed as is the notion of the critical community size, defined as the size which distinguishes between the two qualitatively different behaviours. Received: 14 February 2000 / Revised version: 5 June 2000 / Published online: 24 November 2000