Social, conservation and economic implications of rabies in Australia
Biophilia, our inherent love of living things, is a major driver of the modern conservation ethic worldwide. Australians are particularly fond of wildlife and consequently, our fauna are key to our national image. As a nation, we are known for our relatively carefree attitude towards some of the world's most dangerous animals, including venomous snakes and spiders, as well as sharks. This has arisen largely because we are familiar with these species, understand the actual level of risk they pose and have some idea of how to safely interact with them. Unfortunately, the relationship between Australians and our wildlife could change significantly. Canine rabies, an infamous, fatal, viral zoonosis, is now less than 300 kilometers from the Australian mainland. We must face the possibility of a 'when', rather than 'if' scenario and begin to plan for rabies management on a continent where virtually the entire population is naïve. Human and animal health would be affected. People, domestic animals and wildlife may die. Perhaps worse, in terms of scale, is the likely change in the Australian way of life, including the way we perceive, value and interact with wildlife, pets and livestock. Of course, rabies is endemic in many other countries and people continue to actively engage in conservation programs, but these people have had a long time to come to terms with the risk in their midst and many undergo prophylactic vaccination to enable them to work with wildlife. Here, we discuss Australia's impending future with particular regard to how canine rabies could change our lives, the impacts it could have on wildlife conservation and the steps we must take to be prepared.
Effects of Sex and Reproductive State on Interactions between Free-Roaming Domestic Dogs
Free-roaming dogs ('Canis familiaris') are common worldwide, often maintaining diseases of domestic pets and wildlife. Management of these dogs is difficult and often involves capture, treatment, neutering and release. Information on the effects of sex and reproductive state on intraspecific contacts and disease transmission is currently lacking, but is vital to improving strategic management of their populations. We assessed the effects of sex and reproductive state on short-term activity patterns and contact rates of free-roaming dogs living in an Australian Indigenous community. Population, social group sizes and rates of contact were estimated from structured observations along walked transects. Simultaneously, GPS telemetry collars were used to track dogs' movements and to quantify the frequency of contacts between individual animals. We estimated that the community's dog population was 326±52, with only 9.8±2.5% confined to a house yard. Short-term activity ranges of dogs varied from 9.2 to 133.7 ha, with males ranging over significantly larger areas than females. Contacts between two or more dogs occurred frequently, with entire females and neutered males accumulating significantly more contacts than spayed females or entire males. This indicates that sex and reproductive status are potentially important to epidemiology, but the effect of these differential contact rates on disease transmission requires further investigation. The observed combination of unrestrained dogs and high contact rates suggest that contagious disease would likely spread rapidly through the population. Pro-active management of dog populations and targeted education programs could help reduce the risks associated with disease spread.
Quantifying effects of wild dogs, domestic dogs and humans on the spread of rabies in Australia
Rabies is a preventable viral zoonosis that causes inflammation of the brain, and eventually death, in infected mammals. With few exceptions, including Australia, terrestrial rabies can be found worldwide. More than 55,000 deaths from rabies infection are reported annually; these are mainly in Asia and Africa where the primary reservoir is the domestic dog.
Despite ongoing control efforts in Indonesia, canine rabies remains a disease of critical concern there. Although rabies is not endemic in Australia, at less than 300km away in Indonesia, a rabies incursion is a likely and imminent threat.
To improve preparedness for a canine rabies outbreak in Australia, I collected data on a number of extant dog populations in northern and eastern Australia. I used a range of methods including self-administered questionnaires, GPS telemetry collars, camera trapping and mark-recapture studies. Using my own data and parameters collected from the wider literature, I developed state-transition models to determine how rabies could spread through these dog populations. Finally, I used these same models to evaluate a range of control strategies, including dog removal and vaccination, to identify the most effective options for reducing impacts in Australian communities following a rabies incursion.
Model outputs suggested that rabies will progress differently within functionally different dog populations present within Australia. Restrained domestic dogs posed limited risk for rabies transmission, because interactions with other dogs were limited and generally supervised by owners. Free-roaming domestic and hunting dogs will likely play an important role in rabies transmission in some situations only, primarily based on their ability to roam, access to other free-roaming dogs and their interactions within and between dog groups. Wild dogs (including dingoes) proved the most critical type of dog for rabies spread and maintenance in Australia, because they are widely distributed, often in high abundance, roam over large distances and frequently interact.
I found that time to detection for rabies in wild dogs will likely be lengthy, probably due to low infection rates prior to an epidemic and limited contact with humans, relative to the other categories of dog that I studied. Further, the capacity of authorities to implement effective control strategies for wild dogs will likely be restricted because of limited access to individual animals. The economic costs of controlling a rabies outbreak involving wild dogs will be substantial and likely equivalent to the costs for extensive aerially-based wild dog control that are currently used in some areas of Australia (~Aus$34 km-2).
Australia’s current plans to address rabies incursions, which were developed in the 1990s are clearly outdated. My findings reveal that revision of these plans, taking specific account of relevant differences between restrained domestic dogs, free-roaming domestic dogs and extensive wild dog populations is necessary to ensure that Australia is adequately prepared for the arrival of canine rabies.
Canine rabies in Australia: Modelling spread through the landscape
Introduction: Canine rabies, a fatal viral zoonosis, is now less than 300 kilometres from Indonesian archipelago. To respond to this imminent threat, we need to model how rabies will spread through Australian ecosystems, to develop effective rabies management plans. This will improve our chances of minimising reaction times and containing outbreaks. Aims: To quantify contact rates, abundance, population turnover and dog bite frequency, in order to inform models of canine rabies spread. This is essential for identifying critical control points.
Rabies disease dynamics in naȉve dog populations in Australia
Currently, Australia is free from terrestrial rabies but an incursion from nearby Indonesia, where the virus is endemic, is a feasible threat. Here, we aimed to determine whether the response to a simulated rabies incursion would vary between three extant Australian dog populations; free-roaming domestic dogs from a remote indigenous community in northern Australia, and free-roaming domestic and wild dogs in peri-urban areas of north-east New South Wales. We further sought to predict how different management strategies impacted disease dynamics in these populations. We used simple stochastic state-transition models and dog demographic and contact rate data from the three dog populations to simulate rabies spread, and used global and local sensitivity analyses to determine effects of model parameters. To identify the most effective control options, dog removal andvaccination strategies were also simulated. Responses to simulated rabies incursions varied between the dog populations. Free-roaming domestic dogs from north-east New South Wales exhibited the lowest risk for rabies maintenance and spread. Due to low containment and high contact rates, rabies progressed rapidly through free-roaming dogs from the remote indigenous community in northern Australia. In contrast, rabies remained at relatively low levels within the north-east New South Wales wild dog population for over a year prior to an epidemic. Across all scenarios, sensitivity analyses revealed that contact rates and the probability of transmission were the most important drivers of the number of infectious individuals within a population. The number of infectious individuals was less sensitive to birth and death rates. Removal of dogs as a control strategy was not effective for any population modelled, while vaccination rates in excess of 70% of the population resulted in significant reductions in disease progression. The variability in response between these distinct dog groups to a rabies incursion, suggests that a blanket approach to management would not be effective or feasible to control rabies in Australia. Control strategies that take into account the different population and behavioural characteristics of these doggroups will maximise the likelihood of effective and efficient rabies control in Australia.
Resolving the value of the dingo in ecological restoration
There is global interest in restoring populations of apex predators, both to conserve them and to harness their ecological services. In Australia, reintroduction of dingoes (Canis dingo) has been proposed to help restore degraded rangelands. This proposal is based on theories and the results of studies suggesting that dingoes can suppress populations of prey (especially medium- and large-sized herbivores) and invasive predators such as red foxes (Vulpes vulpes) and feral cats (Felis catus) that prey on threatened native species. However, the idea of dingo reintroduction has met opposition, especially from scientists who query the dingo's positive effects for some species or in some environments. Here, we ask 'what is a feasible experimental design for assessing the role of dingoes in ecological restoration?' We outline and propose a dingo reintroduction experiment-one that draws upon the existing dingo-proof fence-and identify an area suitable for this (Sturt National Park, western New South Wales). Although challenging, this initiative would test whether dingoes can help restore Australia's rangeland biodiversity, and potentially provide proof-of-concept for apex predator reintroductions globally.
Signaling systems in Australian wild dogs: Who's calling and who cares?
Alarm and distress vocalizations are important anti-predator strategies for many species. An alarm call is a particular vocal response to potential or actual danger, whereas a distress call is an involuntary emotional response to a similar situation and/or stimuli. Alarm and distress calls are often associated with prey species. Australian wild dogs (dingoes, feral dogs and their hybrids) have been observed utilizing similar strategies in response to intense human interactions. We analyzed the spectral (frequency and amplitude shifts) and temporal (call length) components of vocalizations recorded from trapped wild dogs and compared these to vocalizations from captive individuals under non-stressful situations. (i) Vocal responses to trapping are not restricted to distress calls. (ii) The structure of wild dog vocalizations differs across sites, suggesting local dialects or individual differences exist. (iii) Age and social status may affect the type of call elicited by an individual. Understanding the differences in vocalizations of wild dogs in varying environments is vital to the success of remote acoustic monitoring endeavors and to the improvement of wildlife management as a proxy for individual stress. Understanding how vocal communication varies across groups will aid in understanding the evolution of the dingo.
Roles for the Canidae in food webs reviewed: Where do they fit?
The roles of the 37 species in the family Canidae (the dog family), are of great current interest. The Gray Wolf is the largest canid and their roles in food webs are much researched, as are those of Domestic Dogs, Coyotes and Red Foxes. Much less is known about the other canid species and their ecological roles. Here we describe general food web theory and the potential application of network theory to it; summarise the possible roles of predators in food webs; document the occurrence, diet and presumed functions that canids play in food webs throughout the world; give case studies of four threatened canid species of top, middle and basal trophic positions and six anthropogenically affected species; and identify knowledge limitations and propose research frameworks necessary to establish the roles of canids in food webs. Canids can be top-down drivers of systems or responsive to the availability of resources including suitable prey. They can be affected anthropogenically by habitat change, lethal control and changes to basic resource availability. They can be sustainable yield harvesters of their indigenous prey or passengers in complex ecosystems, and some are prey of larger canids and of other predators. Nevertheless, the roles of most canids are generally poorly studied and described, and some, e.g. Gray Wolves, Coyotes and Australian dingoes, are controversial. We advocate mensurative and experimental research into communities and ecosystems containing canids for a quantitative understanding of their roles in food webs and consequent development of better management strategies for ecosystems.