Estimating loss of Brucella abortus antibodies from age-specific serological data in elk

Serological data are one of the primary sources of information for disease monitoring in wildlife. However, the duration of the seropositive status of exposed individuals is almost always unknown for many free-ranging host species. Directly estimating rates of antibody loss typically requires difficult longitudinal sampling of individuals following seroconversion. Instead, we propose a Bayesian statistical approach linking age and serological data to a mechanistic epidemiological model to infer brucellosis infection, the probability of antibody loss, and recovery rates of elk (Cervus canadensis) in the Greater Yellowstone Ecosystem. We found that seroprevalence declined above the age of ten, with no evidence of disease-induced mortality. The probability of antibody loss was estimated to be 0.70 per year after a five-year period of seropositivity and the basic reproduction number for brucellosis to 2.13. Our results suggest that individuals are unlikely to become re-infected because models with this mechanism were unable to reproduce a significant decline in seroprevalence in older individuals. This study highlights the possible implications of antibody loss, which could bias our estimation of critical epidemiological parameters for wildlife disease management based on serological data

On Process Equivalence = Equation Solving in CCS

Unique Fixpoint Induction (UFI) is the chief inference rule to prove the equivalence of recursive processes in the Calculus of Communicating Systems (CCS) (Milner 1989). It plays a major role in the equational approach to verification. Equational verification is of special interest as it offers theoretical advantages in the analysis of systems that communicate values, have infinite state space or show parameterised behaviour. We call these kinds of systems VIPSs. VIPSs is the acronym of Value-passing, Infinite-State and Parameterised Systems. Automating the application of UFI in the context of VIPSs has been neglected. This is both because many VIPSs are given in terms of recursive function symbols, making it necessary to carefully apply induction rules other than UFI, and because proving that one VIPS process constitutes a fixpoint of another involves computing a process substitution, mapping states of one process to states of the other, that often is not obvious. Hence, VIPS verification is usually turned into equation solving (Lin 1995a). Existing tools for this proof task, such as VPAM (Lin 1993), are highly interactive. We introduce a method that automates the use of UFI. The method uses middle-out reasoning (Bundy et al. 1990a) and, so, is able to apply the rule even without elaborating the details of the application. The method introduces meta-variables to represent those bits of the processes’ state space that, at application time, were not known, hence, changing from equation verification to equation solving. Adding this method to the equation plan developed by Monroy et al. (Autom Softw Eng 7(3):263–304, 2000a), we have implemented an automatic verification planner. This planner increases the number of verification problems that can be dealt with fully automatically, thus improving upon the current degree of automation in the field

Rabies in East and Southeast Asia: a mirror of the global situation

Despite the availability of efficacious and safe vaccines for human and animal use, rabies takes tens of thousands of human lives annually worldwide. The vast majority of human rabies cases are due to exposure through a rabid dog and subsequent lack of access to post-exposure prophylaxis (PEP) in remote and poor communities around the globe. Therefore, low- and middle-income countries and rural settings are highly affected by this deadly zoonotic disease, while rabies is eliminated from the domestic reservoir in most of the economically strong countries and areas. Although rabies reservoirs in wildlife remain a danger almost all around the world, human cases due to exposure to sylvatic and bat rabies is marginal. Recently momentum, fuelled by the World Health Organization and partners, has been gaining to achieve global elimination of dog-mediated human rabies. Main objectives are increasing efficiency of surveillance, wide scale vaccination of dog population together with dog population management and worldwide coverage for affordable PEP. Advances on the agenda to this global goal vary from country to country. Whereas surveillance and intervention in animals and humans remain patchy and inefficient in some countries, others are focussing on interventions in humans. Those most advanced in the control of rabies have implemented surveillance and prevention measures in the animal reservoir, which is the most cost-effective approach. The South and Southeast Asian region mirrors the described global situation comprising the whole spectrum from rabies-free countries, to countries with only sylvatic rabies and finally the largest group of those with endemic dog rabies. Within the latter, distinctions are made between those that focus on prevention in humans and those with a One Health approach including intervention in animals. Some areas have even adopted an integrative community participation approach including educational programmes. The different sections of this chapter describe the detailed rabies situation in South and Southeast Asian countries grouped by epidemiological context and implemented prevention measures. It highlights the need for holistic control programmes coordinated across the whole region to achieve sustainable elimination of rabies