The emergence of vampire bat rabies in Uruguay within a historical context.

Pathogen spillover from wildlife to humans or domestic animals requires a series of conditions to align with space and time. Comparing these conditions between times and locations where spillover does and does not occur presents opportunities to understand the factors that shape spillover risk. Bovine rabies transmitted by vampire bats was first confirmed in 1911 and has since been detected across the distribution of vampire bats. However, Uruguay is an exception. Uruguay was free of bovine rabies until 2007, despite high-cattle densities, the presence of vampire bats and a strong surveillance system. To explore why Uruguay was free of bovine rabies until recently, we review the historic literature and reconstruct the conditions that would allow rabies invasion into Uruguay. We used available historical records on the abundance of livestock and wildlife, the vampire bat distribution and occurrence of rabies outbreaks, as well as environmental modifications, to propose four alternative hypotheses to explain rabies virus emergence and spillover: bat movement, viral invasion, surveillance failure and environmental changes. While future statistical modelling efforts will be required to disentangle these hypotheses, we here show how a detailed historical analysis can be used to generate testable predictions for the conditions leading to pathogen spillover.

Conditions affecting the timing and magnitude of Hendra virus shedding across pteropodid bat populations in Australia.

Understanding infection dynamics in animal hosts is fundamental to managing spillover and emergence of zoonotic infections. Hendra virus is endemic in Australian pteropodid bat populations and can be lethal to horses and humans. However, we know little about the factors driving Hendra virus prevalence in resevoir bat populations, making spillover difficult to predict. We use Hendra virus prevalence data collected from 13 000 pooled bat urine samples across space and time to determine if pulses of prevalence are periodic and synchronized across sites. We also test whether site-specific precipitation and temperature affect the amplitude of the largest annual prevalence pulses. We found little evidence for a periodic signal in Hendra virus prevalence. Although the largest amplitude pulses tended to occur over winter, pulses could also occur in other seasons. We found that Hendra virus prevalence was weakly synchronized across sites over short distances, suggesting that prevalence is driven by local-scale effects. Finally, we found that drier conditions in previous seasons and the abundance of Pteropus alecto were positively correlated with the peak annual values of Hendra virus prevalence. Our results suggest that in addition to seasonal effects, bat density and local climatic conditions interact to drive Hendra virus infection dynamics.

Persistent infections support maintenance of a coronavirus in a population of Australian bats (Myotis macropus).

Understanding viral transmission dynamics within populations of reservoir hosts can facilitate greater knowledge of the spillover of emerging infectious diseases. While bat-borne viruses are of concern to public health, investigations into their dynamics have been limited by a lack of longitudinal data from individual bats. Here, we examine capture-mark-recapture (CMR) data from a species of Australian bat (Myotis macropus) infected with a putative novel Alphacoronavirus within a Bayesian framework. Then, we developed epidemic models to estimate the effect of persistently infectious individuals (which shed viruses for extensive periods) on the probability of viral maintenance within the study population. We found that the CMR data analysis supported grouping of infectious bats into persistently and transiently infectious bats. Maintenance of coronavirus within the study population was more likely in an epidemic model that included both persistently and transiently infectious bats, compared with the epidemic model with non-grouping of bats. These findings, using rare CMR data from longitudinal samples of individual bats, increase our understanding of transmission dynamics of bat viral infectious diseases.

The effect of seasonal birth pulses on pathogen persistence in wild mammal populations.

The notion of a critical community size (CCS), or population size that is likely to result in long-term persistence of a communicable disease, has been developed based on the empirical observations of acute immunizing infections in human populations, and extended for use in wildlife populations. Seasonal birth pulses are frequently observed in wildlife and are expected to impact infection dynamics, yet their effect on pathogen persistence and CCS have not been considered. To investigate this issue theoretically, we use stochastic epidemiological models to ask how host life-history traits and infection parameters interact to determine pathogen persistence within a closed population. We fit seasonal birth pulse models to data from diverse mammalian species in order to identify realistic parameter ranges. When varying the synchrony of the birth pulse with all other parameters being constant, our model predicted that the CCS can vary by more than two orders of magnitude. Tighter birth pulses tended to drive pathogen extinction by creating large amplitude oscillations in prevalence, especially with high demographic turnover and short infectious periods. Parameters affecting the relative timing of the epidemic and birth pulse peaks determined the intensity and direction of the effect of pre-existing immunity in the population on the pathogen's ability to persist beyond the initial epidemic following its introduction.

Deciphering serology to understand the ecology of infectious diseases in wildlife.

The ecology of infectious disease in wildlife has become a pivotal theme in animal and public health. Studies of infectious disease ecology rely on robust surveillance of pathogens in reservoir hosts, often based on serology, which is the detection of specific antibodies in the blood and is used to infer infection history. However, serological data can be inaccurate for inference to infection history for a variety of reasons. Two major aspects in any serological test can substantially impact results and interpretation of antibody prevalence data: cross-reactivity and cut-off thresholds used to discriminate positive and negative reactions. Given the ubiquitous use of serology as a tool for surveillance and epidemiological modeling of wildlife diseases, it is imperative to consider the strengths and limitations of serological test methodologies and interpretation of results, particularly when using data that may affect management and policy for the prevention and control of infectious diseases in wildlife. Greater consideration of population age structure and cohort representation, serological test suitability and standardized sample collection protocols can ensure that reliable data are obtained for downstream modeling applications to characterize, and evaluate interventions for, wildlife disease systems.

The effect of feeder location on pollen collection by bumble bees in a tomato greenhouse in Ontario, Canada.

The foraging behavior of bumble bees (Bombus impatiens Cresson) was examined as a function of feeder location containing sugar solution in a commercial tomato greenhouse in Manotick, Ontario, Canada. The feeders were located within the nest-box (fed-close) or placed 1.5 m away (fed-far) and the placement of the two types of colonies was counterbalanced over time. No effect of feeder location was found in colony activity levels or in pollen load size. A foraging trade-off between sugar solution and pollen collection, however, was found: the proportion of foraging trips in which pollen was brought back was significantly reduced for fed-far colonies, which contrasts with our laboratory study in which the opposite effect was found. We interpret our findings as possibly reflecting a limitation in pollen supply in the greenhouse: an already possibly strained ability to find and bring back pollen to the colony was accentuated by increasing the task demands of collecting sugar solution.

Genetic and morphometric evidence for the conspecific status of the bumble bees, Bombus melanopygus and Bombus edwardsii.

The taxonomic status of closely related bumble bee species is often unclear. The relationship between the two nominate taxa, Bombus melanopygus Nylander (Hymenoptera: Apidae) and Bombus edwardsii Cresson (Hymenoptera: Apidae), was investigated using genetic (enzyme electrophoretic) and morphometric analyses. The taxa differ in the color of the abdominal terga two and three, being ferruginous in B. melanopygus and black in B. edwardsii. B. edwardsii occurs throughout California, while B. melanopygus extends north through Oregon, to Alaska and Canada. They are sympatric only in southern Oregon and northern California. The taxonomic status of these taxa was questioned when Owen and Plowright (1980) reared colonies from queens collected in the area of sympatry, and discovered that pile coloration was due to a single, biallelic Mendelian gene, with the red (R) allele dominant to the black (r). Here it is shown that all the taxa, whether from California, Oregon, or Alberta, have the same electrophoretic profile and cannot be reliably distinguished by wing morphometrics. This strongly supports the conclusion that B. melanopygus and B. edwardsii are conspecific and should be synonymized under the name B. melanopygus. Hence, there is a gene frequency cline running from north to south, where the red allele is completely replaced by the black allele over a distance of about 600 km.

Crevasse fall in the Antarctic: a patient's perspective.

As a veterinarian working on an Adélie penguin research program, I was to spend six months on an island off the coast of Mawson Station in the Australian Antarctic Territory. During a field training exercise on my third day at Mawson, I fell into a crevasse with my four-wheel-drive quad bike and was crushed between the bike and the crevasse wall six metres below the rim. I had hypothermia and abdominal injuries, and underwent two emergency surgical procedures at Mawson Station. Sixteen days after the accident, I was evacuated by helicopter and ship. Here, I describe my experiences.

The development of an individualized questionnaire measure of perceived impact of diabetes on quality of life: the ADDQoL.

The objectives of the study were to design and develop a questionnaire to measure individuals' perceptions of the impact of diabetes on their quality of life (QoL). The design of the ADDQoL (Audit of Diabetes Dependent QoL) was influenced by patient-centred principles underlying the SEIQoL interview method. Respondents rate only personally-applicable life domains, indicating importance and impact of diabetes. Fifty-two out-patients with diabetes and 102 attending diabetes education open days provided data for psychometric analyses. Each of the 13 domain-specific ADDQoL items was relevant and important for substantial numbers of respondents. Factor analysis and Cronbach's alpha coefficient of internal consistency (0.85) supported combination of items into a scale. Insulin-treated patients reported greater impact of diabetes on QoL than table/diet-treated patients. People with microvascular complications showed, as expected, greater diabetes-related impairment of QoL than people without complications. Unlike other QoL measures, the ADDQoL is an individualized questionnaire measure of the impact of diabetes and its treatment on QoL. Preliminary evidence of reliability and validity is established for adults with diabetes. Findings suggest that the ADDQoL will be more sensitive to change and responsive to differences than generic QoL measures.

An appraisal of cardiovascular standards for Australian civilian flying licences.

This paper summarises recommendations drawn up at a meeting of a group of Cardiologists and Aviation Medical personnel to review cardiovascular standards for Australian Civil Flying Licences. Major recommendations were in the field of ischemic heart disease which remains the commonest cause of disqualification. The panel recommended consideration of coronary risk factors and increased attention to the high risk group as a preventive measure for loss of licence. Licensing, with appropriate safeguards and continued supervision, was considered permissible in carefully selected subjects with ischemic heart disease. Guidelines were also drawn up for various licence categories for subjects with valvular heart disease, cardiac arrhythmias, implanted pacemakers, cardiomyopathy and hypertension.

Competition between hummingbirds and bumble bees for nectar in flowers of Impatiens biflora.

Using removal experiments and concurrent measurement of resource levels, evidence was obtained for exploitation competition between Ruby-throated hummingbirds and two bumble bee species (Bombus fervidus and B. vagans) foraging for nectar on Impatiens biflora.When all three species were active, flower visitors showed a complex pattern of resource partitioning involving both diel and spatial changes. Hummingbirds foraged almost exclusively from the outermost exposed flowers on plants from which they drained nectar levels beyond the reach of bees over most of the day. In contrast the longtongued bee species (B. fervidus), and the shorter-tongued B. vagans, displayed a preference for the innermost flowers on plants which were protected from hummingbird visitation by surrounding vegetation. The two Bombus spp. began foraging at different times during the day: B. vagans were most active in early morning but were replaced by B. fervidus later in the day.When hummingbirds were rare, only B. fervidus showed evidence of competitive release: an increase in the number of foragers and a broadening of flower choice to include more outer flowers. Workers of B. vagans showed a similar response to temporary removal of B. fervidus and also extended their foraging over the entire day. These responses were consistent with changes in the availability of nectar to different species.Removal experiments demonstrated that individuals of one species can be largely excluded from access to nectar resources as a direct result of exploitation of nectar by foragers of other species with longer tongues. Thus in this system interspecific exploitation is an important mechanism involved in resource partitioning.

Behavior of bumble bee pollinators of Aralia hispida Vent. (Araliaceae).

The andromonoecious plant Aralia hispida has a complicated blooming schedule involving alternations between male and female phases.Nectar and pollen are released gradually through the day. Plants vary considerably in number of flowers per umbel and number of umbels per plant. The major pollinators, bumble bees, show several characteristic behaviors in response to the plant's presentation. 1. Foraging bees preferentially visit umbels that bear large numbers of open, male-phase flowers. They also prefer shoots with large numbers of umbels. 2. If bees have received high nectar rewards at one umbel, they are more likely to visit a neighboring umbel rather than leaving the area. On drained umbels, bees probe more empty flowers before rejecting the umbel if they have been rewarded just previously. 3. Individual bees restrict their foraging to limited areas. Within these areas, they concentrate their visits on certain shoots which they tend to visit in repeatable sequences, or "traplines". It is inappropriate to consider these bees as "searching". 4. We discuss some of the implications of these data for two areas of current theoretical interest: plant reproductive strategies and optimal foraging.

Pollen carryover, nectar rewards, and pollinator behavior with special reference to Diervilla lonicera.

Pollen carryover was measured in three species of bumble bee pollinated plants by counting the numbers of foreign grains applied to the stigmas of a series of flowers by bumble bees. Deposition declined with the number of flowers visited in a roughly exponential fashion; most grains were deposited on the first few flowers, but some grains went much farther, the maximum carryover being 54 flowers. Variation in deposition was very high. In Diervilla lonicera, bees desposited significantly more grains on flowers which contained large amounts of nectar than on drained flowers. The implications are discussed in terms of plant strategies for optimizing pollination.