The importance of dog population contact network structures in rabies transmission

Modeling the effectiveness of targeting Rift Valley fever virus vaccination using imperfect network information

Livestock movements contribute to the spread of several infectious diseases. Data on livestock movements can therefore be harnessed to guide policy on targeted interventions for controlling infectious livestock diseases, including Rift Valley fever (RVF)-a vaccine-preventable arboviral fever. Detailed livestock movement data are known to be useful for targeting control efforts including vaccination. These data are available in many countries, however, such data are generally lacking in others, including many in East Africa, where multiple RVF outbreaks have been reported in recent years. Available movement data are imperfect, and the impact of this uncertainty in the utility of movement data on informing targeting of vaccination is not fully understood. Here, we used a network simulation model to describe the spread of RVF within and between 398 wards in northern Tanzania connected by cattle movements, on which we evaluated the impact of targeting vaccination using imperfect movement data. We show that pre-emptive vaccination guided by only market movement permit data could prevent large outbreaks. Targeted control (either by the risk of RVF introduction or onward transmission) at any level of imperfect movement information is preferred over random vaccination, and any improvement in information reliability is advantageous to their effectiveness. Our modeling approach demonstrates how targeted interventions can be effectively used to inform animal and public health policies for disease control planning. This is particularly valuable in settings where detailed data on livestock movements are either unavailable or imperfect due to resource limitations in data collection, as well as challenges associated with poor compliance.

The Amazonian Tropical Bites Research Initiative, a hope for resolving zoonotic neglected tropical diseases in the One Health era

BACKGROUND

Neglected tropical diseases (NTDs) disproportionately affect populations living in resource-limited settings. In the Amazon basin, substantial numbers of NTDs are zoonotic, transmitted by vertebrate (dogs, bats, snakes) and invertebrate species (sand flies and triatomine insects). However, no dedicated consortia exist to find commonalities in the risk factors for or mitigations against bite-associated NTDs such as rabies, snake envenoming, Chagas disease and leishmaniasis in the region. The rapid expansion of COVID-19 has further reduced resources for NTDs, exacerbated health inequality and reiterated the need to raise awareness of NTDs related to bites.

METHODS

The nine countries that make up the Amazon basin have been considered (Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Surinam and Venezuela) in the formation of a new network.

RESULTS

The Amazonian Tropical Bites Research Initiative (ATBRI) has been created, with the aim of creating transdisciplinary solutions to the problem of animal bites leading to disease in Amazonian communities. The ATBRI seeks to unify the currently disjointed approach to the control of bite-related neglected zoonoses across Latin America.

CONCLUSIONS

The coordination of different sectors and inclusion of all stakeholders will advance this field and generate evidence for policy-making, promoting governance and linkage across a One Health arena.

Advancing One human-animal-environment Health for global health security: what does the evidence say?

In this Series paper, we review the contributions of One Health approaches (ie, at the human-animal-environment interface) to improve global health security across a range of health hazards and we summarise contemporary evidence of incremental benefits of a One Health approach. We assessed how One Health approaches were reported to the Food and Agricultural Organization of the UN, the World Organisation for Animal Health (WOAH, formerly OIE), and WHO, within the monitoring and assessment frameworks, including WHO International Health Regulations (2005) and WOAH Performance of Veterinary Services. We reviewed One Health theoretical foundations, methods, and case studies. Examples from joint health services and infrastructure, surveillance-response systems, surveillance of antimicrobial resistance, food safety and security, environmental hazards, water and sanitation, and zoonoses control clearly show incremental benefits of One Health approaches. One Health approaches appear to be most effective and sustainable in the prevention, preparedness, and early detection and investigation of evolving risks and hazards; the evidence base for their application is strongest in the control of endemic and neglected tropical diseases. For benefits to be maximised and extended, improved One Health operationalisation is needed by strengthening multisectoral coordination mechanisms at national, regional, and global levels.

Habitat selection by free-roaming domestic dogs in rabies endemic countries in rural and urban settings

Domestic dogs can affect human health through bites and pathogen transmission, particularly in resource-poor countries where dogs, including owned ones, predominantly roam freely. Habitat and resource selection analysis methods are commonplace in wildlife studies but have not been used to investigate the environmental resource use of free-roaming domestic dogs (FRDD). The present study implements GPS devices to investigate habitat selection by FRDD from an urban site and a rural site in Indonesia, and one urban and two rural sites in Guatemala (N = 321 dogs). Spatial mixed effects logistic regression models, accounting for heterogeneous distribution of the resources, showed that patterns of habitat selection by FRDD were similar across study sites. The most preferred resources were anthropogenic, being buildings and roads, which implies selection for human proximity. Vegetation and open fields were less preferred and steep terrain was avoided, indicating that FRDD were synanthropic and that their space patterns likely optimised energy use. Results presented here provide novel data on FRDD habitat selection patterns, while improving our understanding of dog roaming behaviour. These findings provide insights into possible high-risk locations for pathogen transmission for diseases such as rabies, and can assist management authorities in the planning and deployment of efficient disease control campaigns, including oral vaccination.

Spatial and temporal dynamic analysis of rabies: A review of current methodologies

Rabies continues to be one of the deadliest, high risk diseases worldwide, posing a severe threat to public health. The lack of human-to-human transmission means that the spread of rabies is not significantly affected by the distribution of humans or migra- tion. Thus, the spatiotemporal dynamic of cases in both wild and domestic animals is an important issue that can result in human cases. This paper gives an overview of the methodologies for the spatial and temporal dynamic analysis of this disease. It introduces the most representative research progress of spatial aggregation, dynamic transmission, spatiotemporal distribution, epidemiologi- cal analysis and application of modelling in the study of rabies transmission in recent years. This overview should be useful for investigating the spatial and temporal dynamics of rabies, as it could help understanding the spread of cases as well as contribute to the development of better prevention and control strategies in ecology and epidemiology.

The effects of geographical distributions of buildings and roads on the spatiotemporal spread of canine rabies: An individual-based modeling study

Rabies is a fatal disease that has been a serious health concern, especially in developing countries. Although rabies is preventable by vaccination, the spread still occurs sporadically in many countries, including Thailand. Geographical structures, habitats, and behaviors of host populations are essential factors that may result in an enormous impact on the mechanism of propagation and persistence of the disease. To investigate the role of geographical structures on the transmission dynamics of canine rabies, we developed a stochastic individual-based model that integrates the exact configuration of buildings and roads. In our model, the spatial distribution of dogs was estimated based on the distribution of buildings, with roads considered to facilitate dog movement. Two contrasting areas with high- and low-risk of rabies transmission in Thailand, namely, Hatyai and Tepha districts, were chosen as study sites. Our modeling results indicated that the distinct geographical structures of buildings and roads in Hatyai and Tepha could contribute to the difference in the rabies transmission dynamics in these two areas. The high density of buildings and roads in Hatyai could facilitate more rabies transmission. We also investigated the impacts of rabies intervention, including reducing the dog population, restricting owned dog movement, and dog vaccination on the spread of canine rabies in these two areas. We found that reducing the dog population alone might not be sufficient for preventing rabies transmission in the high-risk area. Owned dog confinement could reduce more the likelihood of rabies transmission. Finally, a higher vaccination coverage may be required for controlling rabies transmission in the high-risk area compared to the low-risk area.

Dog rabies control in West and Central Africa: A review

Rabies is a neglected but preventable zoonotic disease that predominantly affects the most vulnerable populations living in remote rural areas of resource-limited countries. To date, every country on the African mainland is considered endemic for dog-mediated rabies with an estimated 21'500 human rabies deaths occurring each year. In 2018, the United Against Rabies collaboration launched the Global Strategic Plan to end human deaths from dog-mediated rabies by 2030. The epidemiology of rabies from most Western and Central African countries remains poorly defined, making it difficult to assess the overall rabies situation and progress towards the 2030 goal. In this review, we attempt to provide an overview of the current rabies situation in 22 West and Central African countries based on published scientific literature and information obtained from rabies focal points. To this end, information was collected on i) established surveillance, ii) diagnostic capacity, iii) post-exposure prophylaxis (PEP) availability and coverage, iv) dog population estimates, v) dog vaccination campaigns, vi) animal and human health communication (One Health), vii) molecular studies, viii) Knowledge, Attitude and Practices (KAP), ix) cost estimates and x) national control strategies. Although rabies is a notifiable disease in the majority of the studied countries, national surveillance systems do not adequately capture the disease. A general lack of rabies diagnostic capacity has an additional negative impact on rabies surveillance and attempts to estimate rabies burden. Recurrent shortages of human rabies vaccine are reported by all of the countries, with vaccine availability usually limited to major urban centers but no country has yet adopted the new WHO-recommended 1-week intradermal vaccination regimen. Most countries carry out subsidized mass dog vaccination campaigns on World Rabies Day. Such activities are indispensable to keep rabies in the public consciousness but are not of the scale and intensity that is required to eliminate rabies from the dog population. Countries will need to scale up the intensity of their campaigns, if they are to progress towards the 2030 goal. But more than half of the countries do not yet have reliable figures on their dog populations. Only two countries reached stage 2 on the Stepwise Approach towards Rabies Elimination ladder - indicating that their national governments have truly prioritized rabies elimination and are thus providing the necessary support and political buy-in required to achieve success. In summary, the sub-region of West and Central Africa seems to be divided into countries which have accepted the challenge to eliminate rabies with governments committed to pushing forward rabies elimination, while other countries have achieved some progress, but elimination efforts remain stuck due to lacking government commitment and financial constraints. The possibility to meet the 2030 goal without international solidarity is low, because more than two-thirds of the countries rank in the low human development group (HDI ≤ 152). Leading countries should act as role models, sharing their experiences and capacities so that no country is left behind. Unified and with international support it is possible to reach the common goal of zero human rabies deaths by 2030.

From reverse innovation to global innovation in animal health: A review

Reverse innovation refers to learning from or diffusion of innovations developed in low income settings and further translated to industrialized countries. There is lack of consensus regarding terminology, but the idea that innovations in low-income countries are promising for adoption in high-income contexts is not new. However, in healthcare literature globally, the vast majority of publications referring to 'disruptive innovation' were published in the last ten years. To assess the potential of innovative developments and technologies for improving animal health, we initiated a literature review in 2020. We used a combined approach, incorporating targeted searching in PubMed using a key word algorithm with a snowball technique, to identify 120 relevant publications and extract data for qualitative coding. Heterogeneity of articles precluded meta-analysis, quality scoring and risk of bias analysis. We can distinguish technical innovations like new digital devices, diagnostic tests and procedures, and social innovations of intersectoral cooperation. We profile two case studies to describe potential global innovations: an integrated surveillance and response system in Somali Regional State, Ethiopia and a blockchain secured One Health intervention to optimally provide post-exposure prophylaxis for rabies exposed people in West Africa. Innovation follows no borders and can also occur in low-income settings, under constraints of cost, lack of services and infrastructure. Lower administrative and legal barriers may contribute to produce innovations that would not be possible under conditions of high density of regulation. We recommend using the term global innovation, which highlights those emanating from international partnership to solve problems of global implications.

Modelling the influence of naturally acquired immunity from subclinical infection on outbreak dynamics and persistence of rabies in domestic dogs

A number of mathematical models have been developed for canine rabies to explore dynamics and inform control strategies. A common assumption of these models is that naturally acquired immunity plays no role in rabies dynamics. However, empirical studies have detected rabies-specific antibodies in healthy, unvaccinated domestic dogs, potentially due to immunizing, non-lethal exposure. We developed a stochastic model for canine rabies, parameterised for Laikipia County, Kenya, to explore the implications of different scenarios for naturally acquired immunity to rabies in domestic dogs. Simulating these scenarios using a non-spatial model indicated that low levels of immunity can act to limit rabies incidence and prevent depletion of the domestic dog population, increasing the probability of disease persistence. However, incorporating spatial structure and human response to high rabies incidence allowed the virus to persist in the absence of immunity. While low levels of immunity therefore had limited influence under a more realistic approximation of rabies dynamics, high rates of exposure leading to immunizing non-lethal exposure were required to produce population-level seroprevalences comparable with those reported in empirical studies. False positives and/or spatial variation may contribute to high empirical seroprevalences. However, if high seroprevalences are related to high exposure rates, these findings support the need for high vaccination coverage to effectively control this disease.

Spatial and temporal dynamics of space use by free-ranging domestic dogs Canis familiaris in rural Africa

Variation in the spatial ecology of animals influences the transmission of infections and so understanding host behavior can improve the control of diseases. Despite the global distribution of free-ranging domestic dogs Canis familiaris and their role as reservoirs for zoonotic diseases, little is known about the dynamics of their space use. We deployed GPS loggers on owned but free-ranging dogs from six villages in rural Chad, and tracked the movements of 174 individuals in the dry season and 151 in the wet season. We calculated 95% and core home ranges using auto-correlated kernel density estimates (AKDE₉₅ and AKDE_core ), determined the degree to which their movements were predictable, and identified correlates of movement patterns. The median AKDE₉₅ range in the dry season was 0.54 km² and in the wet season was 0.31 km² , while the median AKDE_core range in the dry season was 0.08 km² and in the wet season was 0.04 km² . Seasonal variation was, in part, related to owner activities; dogs from hunting households had ranges that were five times larger in the dry season. At least 70% of individuals were more predictably "at home" (<50 m from the household) throughout the day in the dry season, 80% of dogs demonstrated periodicity in activity levels (speed), and just over half the dogs exhibited periodicity in location (repeated space use). In the wet season, dogs mostly exhibited 24-h cycles in activity and location, with peaks at midday. In the dry season, dogs exhibited both 12- and 24-h cycles, with either a single peak at midday, or one peak between 06:00 and 12:00 and a second between 18:00 and 22:00. Strategies to control canine-mediated zoonoses can be improved by tailoring operations to the local spatial ecology of free-ranging dogs. Interventions using a door-to-door strategy in rural Chad would best conduct operations during the dry season, when access to dogs around their household more reliably exceeds 70% throughout the day. Given the importance of use in hunting for explaining variation in dog space-use, targeting approaches to disease control at the household level on the basis of owner activities offers potential to improve access to dogs.

Rabies Hotspot Detection Using Bipartite Network Modelling Approach

Despite entering its fourth year, the rabies outbreak in the East Malaysian state of Sarawak has claimed another nine lives in 2020, culminating with a total of 31 laboratory-confirmed cases of human rabies as of 31st December 2020. One of the outbreak control challenges faced by the authorities within a previously rabies-free area, such as in the case of Sarawak, is the lack of information regarding possible starting sources, notably hotspot locations of the outbreak. Identification of potential high-risk areas for rabies infection is a sine qua non for effective disease interventions and control strategies. Motivated by this and in preparation for future similar incidents, this paper presented a preliminary study on rabies hotspot identification. The modelling approach adopted the bipartite network where the two disjoint sets of nodes are the Location node and Dog (Bite Cases) node. The formulation of the network followed closely the Bipartite Modeling Methodology Framework. Thorough model verification was done in an attempt to show that such problem domain can be modelled using the Bipartite Modeling approach.

Predictors of free-roaming domestic dogs' contact network centrality and their relevance for rabies control

Free roaming domestic dogs (FRDD) are the main vectors for rabies transmission to humans worldwide. To eradicate rabies from a dog population, current recommendations focus on random vaccination with at least 70% coverage. Studies suggest that targeting high-risk subpopulations could reduce the required vaccination coverage, and increase the likelihood of success of elimination campaigns. The centrality of a dog in a contact network can be used as a measure of its potential contribution to disease transmission. Our objectives were to investigate social networks of FRDD in eleven study sites in Chad, Guatemala, Indonesia and Uganda, and to identify characteristics of dogs, and their owners, associated with their centrality in the networks. In all study sites, networks had small-world properties and right-skewed degree distributions, suggesting that vaccinating highly connected dogs would be more effective than random vaccination. Dogs were more connected in rural than urban settings, and the likelihood of contacts was negatively correlated with the distance between dogs' households. While heterogeneity in dog's connectedness was observed in all networks, factors predicting centrality and likelihood of contacts varied across networks and countries. We therefore hypothesize that the investigated dog and owner characteristics resulted in different contact patterns depending on the social, cultural and economic context. We suggest to invest into understanding of the sociocultural structures impacting dog ownership and thus driving dog ecology, a requirement to assess the potential of targeted vaccination in dog populations.

Mathematical modelling and phylodynamics for the study of dog rabies dynamics and control: A scoping review

BACKGROUND

Rabies is a fatal yet vaccine-preventable disease. In the last two decades, domestic dog populations have been shown to constitute the predominant reservoir of rabies in developing countries, causing 99% of human rabies cases. Despite substantial control efforts, dog rabies is still widely endemic and is spreading across previously rabies-free areas. Developing a detailed understanding of dog rabies dynamics and the impact of vaccination is essential to optimize existing control strategies and developing new ones. In this scoping review, we aimed at disentangling the respective contributions of mathematical models and phylodynamic approaches to advancing the understanding of rabies dynamics and control in domestic dog populations. We also addressed the methodological limitations of both approaches and the remaining issues related to studying rabies spread and how this could be applied to rabies control.

METHODOLOGY/PRINCIPAL FINDINGS

We reviewed how mathematical modelling of disease dynamics and phylodynamics have been developed and used to characterize dog rabies dynamics and control. Through a detailed search of the PubMed, Web of Science, and Scopus databases, we identified a total of n = 59 relevant studies using mathematical models (n = 30), phylodynamic inference (n = 22) and interdisciplinary approaches (n = 7). We found that despite often relying on scarce rabies epidemiological data, mathematical models investigated multiple aspects of rabies dynamics and control. These models confirmed the overwhelming efficacy of massive dog vaccination campaigns in all settings and unraveled the role of dog population structure and frequent introductions in dog rabies maintenance. Phylodynamic approaches successfully disentangled the evolutionary and environmental determinants of rabies dispersal and consistently reported support for the role of reintroduction events and human-mediated transportation over long distances in the maintenance of rabies in endemic areas. Potential biases in data collection still need to be properly accounted for in most of these analyses. Finally, interdisciplinary studies were determined to provide the most comprehensive assessments through hypothesis generation and testing. They also represent new avenues, especially concerning the reconstruction of local transmission chains or clusters through data integration.

CONCLUSIONS/SIGNIFICANCE

Despite advances in rabies knowledge, substantial uncertainty remains regarding the mechanisms of local spread, the role of wildlife in dog rabies maintenance, and the impact of community behavior on the efficacy of control strategies including vaccination of dogs. Future integrative approaches that use phylodynamic analyses and mechanistic models within a single framework could take full advantage of not only viral sequences but also additional epidemiological information as well as dog ecology data to refine our understanding of rabies spread and control. This would represent a significant improvement on past studies and a promising opportunity for canine rabies research in the frame of the One Health concept that aims to achieve better public health outcomes through cross-sector collaboration.

Rabies in Tunisia: A spatio-temporal analysis in the region of CapBon-Nabeul

Human rabies is a significant public health concern in Tunisia. However, the spatiotemporal spread pattern of rabies in dogs, the major reservoir and vector, and its determinants are poorly understood. We collected geographic locations and timeline of reported animal rabies cases in the region of CapBon (study area), for the years 2015-2019 and integrated them in Geographical Information System (GIS) approach to explore the spatio-temporal pattern of dog rabies. The results show that roads and irrigated areas can act as ecological corridors to viral spread. Our study showed that there was a significant seasonal variation in the number of cases of rabies recorded, with a strong peak in spring and lower peak in winter and summer. These findings may play a role in updating and directing public health policy, as well as providing opportunities for authorities to explore control options in time and space. A better knowledge of the ecology and dog population dynamics is still necessary and important to achieve an effective rabies control.

Management practices of dog and cat owners in France (pet traveling, animal contact rates and medical monitoring): Impacts on the introduction and the spread of directly transmitted infectious pet diseases

A number of owner practices among the pet dog and cat population can influence the dynamics of directly transmitted infectious dog and cat diseases, including zoonotic ones. To better depict these management practices, which include pet traveling, contact rates with other companion animals and their medical monitoring (which herein includes prevention aspects), we surveyed 2,122 dog- and/or cat-owning French households through an anonymous online questionnaire. Trips with dogs within the European Union (EU) were frequent, while cats travelled less frequently within the EU and both cats and dogs travelled less frequently outside the EU. Recurrent illegal trips with dogs and cats (non-compliant with regulatory measures) were observed in a context of non-systematic pet border controls. We found that a large proportion of dogs are taken for walks in metropolitan France, with frequent intraspecific contacts (1.4 contacts/day on average), but only a minority (1.4%) of dogs were allowed to roam freely. On the other hand, 59.7% of cat owners allowed their cats to roam freely. We classified pet owners according to different profiles, some of which may be considered 'at risk' for directly transmitted infectious pet diseases. Indeed, one dog owner profile and one cat owner profile depict 'spreaders' of pet diseases (high connectivity with other individuals, little medical monitoring but no traveling) and another dog owner profile describes a potential 'introducer' and 'spreader' of pet diseases (foreign travel, high connectivity with other individuals, and intermediate medical monitoring). While these 'at risk' profiles represent only a minority of French pet owners, they should be better characterized to reinforce targeted prevention designed to minimize the risk of (re)introduction and (re)emergence of directly transmitted infectious dog and cat diseases in France, especially when considering zoonoses with a significant potential impact, such as rabies.

Comparative Study of Free-Roaming Domestic Dog Management and Roaming Behavior Across Four Countries: Chad, Guatemala, Indonesia, and Uganda

Dogs play a major role in public health because of potential transmission of zoonotic diseases, such as rabies. Dog roaming behavior has been studied worldwide, including countries in Asia, Latin America, and Oceania, while studies on dog roaming behavior are lacking in Africa. Many of those studies investigated potential drivers for roaming, which could be used to refine disease control measures. However, it appears that results are often contradictory between countries, which could be caused by differences in study design or the influence of context-specific factors. Comparative studies on dog roaming behavior are needed to better understand domestic dog roaming behavior and address these discrepancies. The aim of this study was to investigate dog demography, management, and roaming behavior across four countries: Chad, Guatemala, Indonesia, and Uganda. We equipped 773 dogs with georeferenced contact sensors (106 in Chad, 303 in Guatemala, 217 in Indonesia, and 149 in Uganda) and interviewed the owners to collect information about the dog [e.g., sex, age, body condition score (BCS)] and its management (e.g., role of the dog, origin of the dog, owner-mediated transportation, confinement, vaccination, and feeding practices). Dog home range was computed using the biased random bridge method, and the core and extended home range sizes were considered. Using an AIC-based approach to select variables, country-specific linear models were developed to identify potential predictors for roaming. We highlighted similarities and differences in term of demography, dog management, and roaming behavior between countries. The median of the core home range size was 0.30 ha (95% range: 0.17-0.92 ha) in Chad, 0.33 ha (0.17-1.1 ha) in Guatemala, 0.30 ha (0.20-0.61 ha) in Indonesia, and 0.25 ha (0.15-0.72 ha) in Uganda. The median of the extended home range size was 7.7 ha (95% range: 1.1-103 ha) in Chad, 5.7 ha (1.5-27.5 ha) in Guatemala, 5.6 ha (1.6-26.5 ha) in Indonesia, and 5.7 ha (1.3-19.1 ha) in Uganda. Factors having a significant impact on the home range size in some of the countries included being male dog (positively), being younger than one year (negatively), being older than 6 years (negatively), having a low or a high BCS (negatively), being a hunting dog (positively), being a shepherd dog (positively), and time when the dog was not supervised or restricted (positively). However, the same outcome could have an impact in a country and no impact in another. We suggest that dog roaming behavior is complex and is closely related to the owner's socioeconomic context and transportation habits and the local environment. Free-roaming domestic dogs are not completely under human control but, contrary to wildlife, they strongly depend upon humans. This particular dog-human bound has to be better understood to explain their behavior and deal with free-roaming domestic dogs related issues.

Modelling the factors affecting the probability for local rabies elimination by strategic control

Dog rabies has been recognized from ancient times and remains widespread across the developing world with an estimated 59,000 people dying annually from the disease. In 2011 a tri-partite alliance consisting of the OIE, the WHO and the FAO committed to globally eliminating dog-mediated human rabies by 2030. Regardless of global support, the responsibility remains with local program managers to implement successful elimination programs. It is well known that vaccination programs have a high probability of successful elimination if they achieve a population-coverage of 70%. It is often quoted that reducing population turnover (typically through sterilizations) raises the probability for local elimination by maintaining herd immunity for longer. Besides this, other factors that affect rabies elimination are rarely mentioned. This paper investigates the probability for local elimination as it relates to immunity, fecundity, dog population size, infectivity (bite rates), in-migration of immune-naïve dogs, and the initial incidence. To achieve this, an individual-based, stochastic, transmission model was manipulated to create a dataset covering combinations of factors that may affect elimination. The results thereof were analysed using a logistic regression model with elimination as the dependent variable. Our results suggest that smaller dog populations, lower infectivity and lower incidence (such as when epidemics start with single introductions) strongly increased the probability for elimination at wide ranges of vaccination levels. Lower fecundity and lower in-migration had weak effects. We discuss the importance of these findings in terms of their impact and their practical application in the design of dog-mediated rabies control programs.

Most guidelines for rabies control call for at least 70% vaccination coverage of dogs. This level of immunity has a very high probability for the local elimination of rabies, but it is often not an achievable ideal due to resource constraints. Campaign managers can be strategic on how they allocate their resources. Lower infectivity rates are present in areas with more restricted dog movements and have higher probabilities for elimination at lower vaccination rates. Smaller sub-populations have higher probabilities for elimination at the same vaccination coverage levels compared to larger sub-populations. Vaccinating immune corridors can divide meta-populations into smaller sub-populations that are likely to result in elimination either due to their small size or due to the local low infectivity. Areas already free of rabies require lower vaccination levels to maintain freedom compared to endemic areas. Where donors do not specifically require sterilization campaigns, funds meant for rabies control should not be diverted to sterilizations.

Comparative Study of Free-Roaming Domestic Dog Management and Roaming Behavior Across Four Countries: Chad, Guatemala, Indonesia, and Uganda

Dogs play a major role in public health because of potential transmission of zoonotic diseases, such as rabies. Dog roaming behavior has been studied worldwide, including countries in Asia, Latin America, and Oceania, while studies on dog roaming behavior are lacking in Africa. Many of those studies investigated potential drivers for roaming, which could be used to refine disease control measures. However, it appears that results are often contradictory between countries, which could be caused by differences in study design or the influence of context-specific factors. Comparative studies on dog roaming behavior are needed to better understand domestic dog roaming behavior and address these discrepancies. The aim of this study was to investigate dog demography, management, and roaming behavior across four countries: Chad, Guatemala, Indonesia, and Uganda. We equipped 773 dogs with georeferenced contact sensors (106 in Chad, 303 in Guatemala, 217 in Indonesia, and 149 in Uganda) and interviewed the owners to collect information about the dog [e.g., sex, age, body condition score (BCS)] and its management (e.g., role of the dog, origin of the dog, owner-mediated transportation, confinement, vaccination, and feeding practices). Dog home range was computed using the biased random bridge method, and the core and extended home range sizes were considered. Using an AIC-based approach to select variables, country-specific linear models were developed to identify potential predictors for roaming. We highlighted similarities and differences in term of demography, dog management, and roaming behavior between countries. The median of the core home range size was 0.30 ha (95% range: 0.17-0.92 ha) in Chad, 0.33 ha (0.17-1.1 ha) in Guatemala, 0.30 ha (0.20-0.61 ha) in Indonesia, and 0.25 ha (0.15-0.72 ha) in Uganda. The median of the extended home range size was 7.7 ha (95% range: 1.1-103 ha) in Chad, 5.7 ha (1.5-27.5 ha) in Guatemala, 5.6 ha (1.6-26.5 ha) in Indonesia, and 5.7 ha (1.3-19.1 ha) in Uganda. Factors having a significant impact on the home range size in some of the countries included being male dog (positively), being younger than one year (negatively), being older than 6 years (negatively), having a low or a high BCS (negatively), being a hunting dog (positively), being a shepherd dog (positively), and time when the dog was not supervised or restricted (positively). However, the same outcome could have an impact in a country and no impact in another. We suggest that dog roaming behavior is complex and is closely related to the owner's socioeconomic context and transportation habits and the local environment. Free-roaming domestic dogs are not completely under human control but, contrary to wildlife, they strongly depend upon humans. This particular dog-human bound has to be better understood to explain their behavior and deal with free-roaming domestic dogs related issues.

Increasing rabies data availability: The example of a One Health research project in Chad, Côte d'Ivoire and Mali

Rabies is a fatal but preventable disease that remains notoriously underreported. Weak data availability hampers advocacy, constitutes a barrier to resource allocation and inhibits effective prevention and control. To gain better insight into the global rabies burden and human vaccine demand several studies were funded through the Vaccine Alliance (GAVI) learning agenda. With the help of this funding, Swiss TPH and local in country partner organizations implemented a One Health research project in Chad, Côte d'Ivoire and Mali to collect data at household, public health facility and veterinary level. This paper describes the implementation of this research project and evaluates its success on amount of information gained, achieved capacity building, impact on knowledge creation and influence on national and international policies. The project was based on the One Health concept and guided by the principles of transboundary research partnerships formulated by the Swiss Academy of Sciences. Data was collected on bite incidents and health seeking from over 24'000 households, on access to treatment of over 8'800 bite cases registered in public health facilities and on the status of over 1'800 rabies suspect animals. Selected country specific datasets have contributed to more than 10 scientific articles so far. On the international level, the multi-level data collection provided a unique set of indicators to inform, along with results from other studies, new WHO rabies immunization recommendations and a vaccine investment case scenario to prevent human rabies. New rabies burden estimates based on the data gathered are published for Mali and will be modelled for the whole West and Central African region. On the national level, the project facilitated communication between animal health and human health workers catalyzing creation of local and national committees and formulation of national action plans for Mali and Côte D'Ivoire. Major challenges arose from lack of data collection and documentation experience of human health and veterinary workers and weak infrastructural capacities of the veterinary and human health systems of the project countries. Through adherence to the principles of transboundary research partnerships, project team members acquired valuable research and networking skills despite language barriers, enabling them to play key roles in the future agenda towards national, regional and global canine rabies elimination. Project external collaborations with local public institutions was facilitated through long-term local partnerships. Both factors enabled success in project implementation and outcomes by identifying and mitigating risks in advance, resolving challenges amiably and enabling mutual knowledge creation as a fructuous ground for sustained commitment. Lack of immediate follow-up funding did not allow to maintain activities beyond the project timeframe. However, the national and international policy changes triggered, as well as the strengthened local disease control and research capacities provides sustainable basis for the elimination of dog transmitted human rabies.

A Practical Introduction to Mechanistic Modeling of Disease Transmission in Veterinary Science

Computer-based disease spread models are frequently used in veterinary science to simulate disease spread. They are used to predict the impacts of the disease, plan and assess surveillance, or control strategies, and provide insights about disease causation by comparing model outputs with real life data. There are many types of disease spread models, and here we present and describe the implementation of a particular type: individual-based models. Our aim is to provide a practical introduction to building individual-based disease spread models. We also introduce code examples with the goal to make these techniques more accessible to those who are new to the field. We describe the important steps in building such models before, during and after the programming stage, including model verification (to ensure that the model does what was intended), validation (to investigate whether the model results reflect the modeled system), and convergence analysis (to ensure models of endemic diseases are stable before outputs are collected). We also describe how sensitivity analysis can be used to assess the potential impact of uncertainty about model parameters. Finally, we provide an overview of some interesting recent developments in the field of disease spread models.

Evaluation of the Worldwide Occurrence of Rabies in Dogs and Cats Using a Simple and Homogenous Framework for Quantitative Risk Assessments of Rabies Reintroduction in Disease-Free Areas through Pet Movements

Dog and cat rabies cases imported from rabies enzootic countries represent a major threat for areas that have acquired rabies-free status and quantitative risk analyses (QRAs) are developed in order to assess this risk of rabies reintroduction through dog and cat movements. Herein we describe a framework to evaluate dog and cat rabies incidence levels in exporting countries along with the associated uncertainty for such QRAs. For enzootic dog rabies areas (EDRAs), we extended and adapted a previously published method to specify the relationship between dog rabies vaccination coverage and canine rabies incidence; the relationship between dog and cat rabies incidences; and then to predict annual dog and cat rabies incidences. In non-enzootic dog rabies areas (nEDRAs), we provided annual incidence based on declared dog and cat rabies cases. For EDRAs, we predicted an annual incidence potentially greater than 1.5% in dogs and about ten times lower in cats with a high burden in Africa and Asia but much lower in Latin America. In nEDRAs, the occurrence of rabies was lower and of similar magnitude in dogs and cats. However, wildlife could still potentially infect dogs and cats through spillover events. This framework can directly be incorporated in QRAs of rabies reintroduction.

Local rabies transmission and regional spatial coupling in European foxes

Infectious diseases are often transmitted through local interactions. Yet, both surveillance and control measures are implemented within administrative units. Capturing local transmission processes and spatial coupling between regions from aggregate level data is therefore a technical challenge that can shed light on both theoretical questions and practical decisions. Fox rabies has been eliminated from much of Europe through oral rabies vaccination (ORV) programmes. The European Union (EU) co-finances ORV to maintain rabies freedom in EU member and border states via a cordon sanitaire. Models to capture local transmission dynamics and spatial coupling have immediate application to the planning of these ORV campaigns and to other parts of the world considering oral vaccination. We fitted a hierarchical Bayesian state-space model to data on three decades of fox rabies cases and ORV campaigns from Eastern Germany. Specifically, we find that (i) combining regional spatial coupling and heterogeneous local transmission allows us to capture regional rabies dynamics; (ii) incursions from other regions account for less than 1% of cases, but allow for re-emergence of disease; (iii) herd immunity achieved through bi-annual vaccination campaigns is short-lived due to population turnover. Together, these findings highlight the need for regular and sustained vaccination efforts and our modelling approach can be used to provide strategic guidance for ORV delivery. Moreover, we show that biological understanding can be gained from inference from partially observed data on wildlife disease.

Long-range movements coupled with heterogeneous incubation period sustain dog rabies at the national scale in Africa

Dog-transmitted rabies is responsible for more than 98% of human cases worldwide, remaining a persistent problem in developing countries. Mass vaccination targets predominantly major cities, often compromising disease control due to re-introductions. Previous work suggested that areas neighboring cities may behave as the source of these re-introductions. To evaluate this hypothesis, we introduce a spatially explicit metapopulation model for rabies diffusion in Central African Republic. Calibrated on epidemiological data for the capital city, Bangui, the model predicts that long-range movements are essential for continuous re-introductions of rabies-exposed dogs across settlements, eased by the large fluctuations of the incubation period. Bangui's neighborhood, instead, would not be enough to self-sustain the epidemic, contrary to previous expectations. Our findings suggest that restricting long-range travels may be very efficient in limiting rabies persistence in a large and fragmented dog population. Our framework can be applied to other geographical contexts where dog rabies is endemic.

Movement patterns of free-roaming dogs on heterogeneous urban landscapes: Implications for rabies control

In 2015, a case of canine rabies in Arequipa, Peru indicated the re-emergence of rabies virus in the city. Despite mass dog vaccination campaigns across the city and reactive ring vaccination and other control activities around positive cases (e.g. elimination of unowned dogs), the outbreak has spread. Here we explore how the urban landscape of Arequipa affects the movement patterns of free-roaming dogs, the main reservoirs of the rabies virus in the area. We tracked 23 free-roaming dogs using Global Positioning System (GPS) collars. We analyzed the spatio-temporal GPS data using the time- local convex hull method. Dog movement patterns varied across local environments. We found that water channels, an urban feature of Arequipa that are dry most of the year, promote movement. Dogs that used the water channels extensively move on average 7 times further (p = 0.002) and 1.2 times more directionally (p = 0.027) than dogs that do not use the water channels at all. They were also 1.3 times faster on average, but this difference was not statistically significant (p = 0.197). Our findings suggest that water channels can be used by dogs as 'highways' to transverse the city and have the potential to spread disease far beyond the radius of control practices. Control efforts should focus on a robust vaccination campaign attuned to the geography of the city, and not limited to small-scale rings surrounding cases.

Using roaming behaviours of dogs to estimate contact rates: the predicted effect on rabies spread

Domestic dogs display complex roaming behaviours, which need to be captured to more realistically model the spread of rabies. We have previously shown that roaming behaviours of domestic dogs can be categorised as stay-at-home, roamer and explorer in the Northern Peninsular Area (NPA), Queensland, Australia. These roaming behaviours are likely to cause heterogeneous contact rates that influence the speed or pattern of rabies spread in a dog population. The aim of this study was to define contact spatial kernels using the overlap of individual dog utilisation distributions to describe the daily probability of contact between pairs of dogs exhibiting these three a priori roaming behaviours. We further aimed to determine if the kernels lead to different predicted rabies outbreaks (outbreak duration and number of rabid dogs) by incorporating the spatial kernels into a previously developed rabies spread model for the NPA. Spatial kernels created with both dogs in a pair being explorers or one dog explorer and one dog roamer (who roamed away from their residence) produced short but large outbreaks compared with spatial kernels with at least one stay-at-home dog. Outputs from this model incorporating heterogeneous contacts demonstrate how roaming behaviours influence disease spread in domestic dog populations.

Impact of One-Health framework on vaccination cost-effectiveness: A case study of rabies in Ethiopia

Livestock losses due to rabies and health and the corresponding benefits of controlling the disease are not often considered when the cost-effectiveness of rabies control is evaluated. In this research, assessed the benefits of applying a One Health perspective that includes these losses to the case of canine rabies vaccination in Ethiopia. We constructed a dynamic epidemiological model of rabies transmission. The model was fit to district-specific data on human rabies exposures and canine demography for two districts with distinct agro-ecologies. The epidemiological model was coupled with human and livestock economic outcomes to predict the health and economic impacts under a range of vaccination scenarios. The model indicates that human exposures, human deaths, and rabies-related livestock losses would decrease monotonically with increasing vaccination coverage. In the rural district, all vaccination scenarios were found to be cost-saving compared to the status quo of no vaccination, as more money could be saved by preventing livestock losses than would be required to fund the vaccination campaigns. Vaccination coverages of 70% and 80% were identified as most likely to provide the greatest net health benefits at the WHO cost-effectiveness threshold over a period of 5 years, in urban and rural districts respectively. Shorter time frames led to recommendations for higher coverage in both districts, as did even a minor threat of rabies re-introduction. Exclusion of rabies-related livestock losses reduced the optimal vaccination coverage for the rural district to 50%. This study demonstrated the importance of including all economic consequences of zoonotic disease into control decisions. Analyses that include cattle and other rabies-susceptible livestock are likely better suited to many rural communities in Africa wishing to maximize the benefits of canine vaccination.

Targeted pre-emptive rabies vaccination strategies in a susceptible domestic dog population with heterogeneous roaming patterns

Australia is free of canine rabies, however northern regions - such as the Northern Peninsula Area (NPA), Queensland - are at risk of an incursion from nearby rabies-infected Indonesian islands. Early detection and reactive vaccination is the current Australian policy to eradicate an incursion. Early detection in this region is challenging, so pre-emptive vaccination might be an effective strategy. The NPA dog population also has a heterogenous contact structure, with three roaming categories previously characterised, which could be exploited in targeted pre-emptive vaccination strategies for more efficient use of limited resources. To evaluate the effectiveness of a pre-emptive vaccination program, an agent-based rabies spread simulation model was used to simulate outbreaks with a range of pre-emptive vaccination coverages. Increasing proportions (10% increments) of the dog population randomly vaccinated were modelled, and at the most efficient random vaccination coverage we then explored 10 pre-emptive vaccination strategies targeting different dog roaming categories (whilst maintaining the same overall population level vaccination coverage). All pre-emptive vaccination strategies were simulated 2000 times without and with a 70% random reactive vaccination strategy, following rabies detection. All random pre-emptive vaccination coverages reduced outbreak size and duration compared to no pre-emptive vaccination. A 40% random coverage was most efficient. Targeted strategies that pre-emptively vaccinated proportionally more roaming dogs were more effective than a random 40% vaccination coverage and strategies that targeted non-roaming dogs. The pre-emptive vaccination strategies that targeted non-roaming dogs produced significantly larger and longer outbreaks. These results suggest that pre-emptive vaccination can reduce potential rabies outbreaks in this region and that such a strategy should not just focus on easily accessible dogs that do not roam often or at all. A cost-benefit analysis is required to determine whether the implementation of such pre-emptive vaccination strategies is also cost-effective, which is essential in the resource-poor communities of this region.

Rabies-induced behavioural changes are key to rabies persistence in dog populations: Investigation using a network-based model

Canine rabies was endemic pre-urbanisation, yet little is known about how it persists in small populations of dogs typically seen in rural and remote regions. By simulating rabies outbreaks in such populations (50-90 dogs) using a network-based model, our objective was to determine if rabies-induced behavioural changes influence disease persistence. Behavioural changes-increased bite frequency and increased number or duration of contacts (disease-induced roaming or paralysis, respectively)-were found to be essential for disease propagation. Spread occurred in approximately 50% of model simulations and in these, very low case rates (2.0-2.6 cases/month) over long durations (95% range 20-473 days) were observed. Consequently, disease detection is a challenge, risking human infection and spread to other communities via dog movements. Even with 70% pre-emptive vaccination, spread occurred in >30% of model simulations (in these, median case rate was 1.5/month with 95% range of 15-275 days duration). We conclude that the social disruption caused by rabies-induced behavioural change is the key to explaining how rabies persists in small populations of dogs. Results suggest that vaccination of substantially greater than the recommended 70% of dog populations is required to prevent rabies emergence in currently free rural areas.

Dog Ecology, Bite Incidence, and Disease Awareness: A Cross-Sectional Survey among a Rabies-Affected Community in the Democratic Republic of the Congo

Despite the existence of safe and efficacious human and animal rabies vaccines, millions of people remain at risk of exposure to this deadly zoonotic disease through bites of infected dogs. Sub-Saharan African countries, such as the Democratic Republic of the Congo (DRC), bear the highest per capita death rates from rabies where dog vaccination and availability of lifesaving post-exposure prophylaxis (PEP) is scarce. Mass dog vaccination is the most cost-effective and sustainable approach to prevent human rabies deaths. We conducted a cross-sectional household survey in a rabies-affected community in Matadi, DRC, to estimate the size of the owned dog population and dog bite incidence and assess knowledge and practices regarding rabies, as preparation for future mass dog vaccination campaigns. Our study revealed that the owned dog population in Matadi was almost ten times larger than assumed by local veterinary officials, with a large proportion of free-roaming unvaccinated dogs. The annual dog bite incidence of 5.2 per 1000 person years was high, whereas community rabies knowledge was low resulting in poor practices. Given these findings, human rabies deaths are likely to occur in this community. Lack of disease awareness could negatively affect participation in future mass dog vaccination campaigns. A public sensitization campaign is needed to promote appropriate rabies prevention (washing bite wounds and PEP) and control (dog vaccination) measures in this community.

Modelling targeted rabies vaccination strategies for a domestic dog population with heterogeneous roaming patterns

Australia is currently canine rabies free. However, communities located on the northern coastline-such as the Northern Peninsula Area (NPA), Queensland-are at risk of an incursion due to their large populations of susceptible free-roaming dogs and proximity to rabies-infected Indonesian islands. A rabies-spread model was used to simulate potential outbreaks and evaluate various disease control strategies. A heterogeneous contact structure previously described in the population of interest-explorer dogs, roamer dogs and stay-at-home dogs-was incorporated into the model using six spatial kernels describing contacts between dog roaming categories. Twenty-seven vaccination strategies were investigated based on a complete block design of 50%, 70% and 90% coverage for each of the three roaming categories to simulate various targeted vaccination strategies. The 27 strategies were implemented in four population structures in which the proportion of dogs in each category varied-explorer dominant, roamer dominant, stay-at-home dominant and a field population (based on field estimates of population structure). The overall vaccination coverage varied depending on the subpopulation targeted for vaccination and the population structure modelled. A total of 108 scenarios were simulated 2000 times and the model outputs (outbreak size and duration) were compared to Strategy 14 (a standard recommended overall 70% vaccination coverage). In general, targeting explorer dogs-and to a lesser extent roamer dogs-produced similar outbreaks to Strategy 14 but with a lower overall vaccination coverage. Similarly, strategies that targeted stay-at-home dogs required a higher vaccination coverage to produce significantly smaller and shorter outbreaks. This study provides some theoretical evidence that targeting subpopulations of dogs for vaccination based on their roaming behaviours (and therefore risk of rabies transmission) could be more efficient than blanket 70% vaccination campaigns. Such information can be used in preparedness planning to help improve control of a potential rabies incursion in Australia.

High-resolution contact networks of free-ranging domestic dogs Canis familiaris and implications for transmission of infection

Contact patterns strongly influence the dynamics of disease transmission in both human and non-human animal populations. Domestic dogs Canis familiaris are a social species and are a reservoir for several zoonotic infections, yet few studies have empirically determined contact patterns within dog populations. Using high-resolution proximity logging technology, we characterised the contact networks of free-ranging domestic dogs from two settlements (n = 108 dogs, covering >80% of the population in each settlement) in rural Chad. We used these data to simulate the transmission of an infection comparable to rabies and investigated the effects of including observed contact heterogeneities on epidemic outcomes. We found that dog contact networks displayed considerable heterogeneity, particularly in the duration of contacts and that the network had communities that were highly correlated with household membership. Simulations using observed contact networks had smaller epidemic sizes than those that assumed random mixing, demonstrating the unsuitability of homogenous mixing models in predicting epidemic outcomes. When contact heterogeneities were included in simulations, the network position of the individual initially infected had an important effect on epidemic outcomes. The risk of an epidemic occurring was best predicted by the initially infected individual's ranked degree, while epidemic size was best predicted by the individual's ranked eigenvector centrality. For dogs in one settlement, we found that ranked eigenvector centrality was correlated with range size. Our results demonstrate that observed heterogeneities in contacts are important for the prediction of epidemiological outcomes in free-ranging domestic dogs. We show that individuals presenting a higher risk for disease transmission can be identified by their network position and provide evidence that observable traits hold potential for informing targeted disease management strategies.

System dynamics modelling approach to explore the effect of dog demography on rabies vaccination coverage in Africa

BACKGROUND

Dogs are important reservoirs of rabies, a zoonotic viral encephalitis that kills thousands of people in Asia and Africa annually. Mass dog vaccination is recommended for the prevention of rabies in both humans and dogs. Mass vaccinations should be conducted annually but more frequent campaigns may be required in areas with high dog turnover rates. Consequently, a good understanding of dog demography is essential for the control of the disease. The aim of this study was to explore the effect of dog demography on rabies vaccination coverage following a mass vaccination campaign with at least 70% vaccination coverage.

METHODOLOGY/PRINCIPAL FINDINGS

A dog population model was constructed to explore the effect of dog demography on rabies vaccination coverage decline. Important model parameters were identified through a comprehensive literature search on dog demography in Africa. A system dynamics approach was adopted to build a dog population model to simulate the effects of demographic processes on rabies vaccination coverage. Vensim PLE Plus software was used to construct the model. Multivariate sensitivity simulations using data from 22 studies and 12 African countries were performed to investigate the effect of dog turnover rates on vaccination coverage decline. In addition, an adjusted vaccination coverage to estimate the proportion of vaccinated dogs with adequate immunity at 12 months post-vaccination was calculated. The results demonstrated that the vaccination coverage and adjusted vaccination coverage remained over 30% and 20% respectively at 12 months if annual mass vaccinations achieved at least 70% coverage.

CONCLUSIONS/SIGNIFICANCE

The results demonstrated that annual mass vaccination campaigns with at least 70% vaccination coverage would maintain a herd immunity of 20‒45% between campaigns.