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

Investigation of optimized observation periods for estimating a representative home range of free-roaming domestic dogs

Free-roaming domestic dogs (FRDD), as vectors of zoonotic diseases, are of high relevance for public health. Understanding roaming patterns of dogs can help to design disease control programs and disease transmission simulation models. Studies on GPS tracking of dogs report stark differences in recording periods. So far, there is no accepted number of days required to capture a representative home range (HR) of FRDD. The objective of this study was to evaluate changes in HR size and shape over time of FRDD living in Chad, Guatemala, Indonesia and Uganda and identify the period required to capture stable HR values. Dogs were collared with GPS units, leading to a total of 46 datasets with, at least, 19 recorded days. For each animal and recorded day, HR sizes were estimated using the Biased Random Bridge method and percentages of daily change in size and shape calculated and taken as metrics. The analysis revealed that the required number of days differed substantially between individuals, isopleths, and countries, with the extended HR (95% isopleth value) requiring a longer recording period. To reach a stable HR size and shape values for 75% of the dogs, 26 and 21 days, respectively, were sufficient. However, certain dogs required more extended observational periods.

Soares Magalhães R, Weese JS, Ahmed NO, Rupprecht CE, Clark NJ. Modelling modifiable factors associated with the probability of human rabies deaths among self-reported victims of dog bites in Abuja, Nigeria

Canine-mediated rabies kills tens of thousands of people annually in lesser-developed communities of Asia, Africa, and the Americas, primarily through bites from infected dogs. Multiple rabies outbreaks have been associated with human deaths in Nigeria. However, the lack of quality data on human rabies hinders advocacy and resource allocation for effective prevention and control. We obtained 20 years of dog bite surveillance data across 19 major hospitals in Abuja, incorporating modifiable and environmental covariates. To overcome the challenge of missing information, we used a Bayesian approach with expert-solicited prior information to jointly model missing covariate data and the additive effects of the covariates on the predicted probability of human death after rabies virus exposure. Only 1155 cases of dog bites were recorded throughout the study period, out of which 4.2% (N = 49) died of rabies. The odds for risk of human death were predicted to decrease among individuals who were bitten by owned dogs compared to those bitten by free-roaming dogs. Similarly, there was a predicted decrease in the probability of human death among victims bitten by vaccinated dogs compared to those bitten by unvaccinated dogs. The odds for the risk of human death after bitten individuals received rabies prophylaxis were predicted to decrease compared to no prophylaxis. We demonstrate the practical application of a regularised Bayesian approach to model sparse dog bite surveillance data to uncover risk factors for human rabies, with broader applications in other endemic rabies settings with similar profiles. The low reporting observed in this study underscores the need for community engagement and investment in surveillance to increase data availability. Better data on bite cases will help to estimate the burden of rabies in Nigeria and would be important to plan effective prevention and control of this disease.

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.

Oral rabies vaccination of dogs—Experiences from a field trial in Namibia

Dog-mediated rabies is responsible for tens of thousands of human deaths annually, and in resource-constrained settings, vaccinating dogs to control the disease at source remains challenging. Currently, rabies elimination efforts rely on mass dog vaccination by the parenteral route. To increase the herd immunity, free-roaming and stray dogs need to be specifically addressed in the vaccination campaigns, with oral rabies vaccination (ORV) of dogs being a possible solution. Using a third-generation vaccine and a standardized egg-flavoured bait, bait uptake and vaccination was assessed under field conditions in Namibia. During this trial, both veterinary staff as well as dog owners expressed their appreciation to this approach of vaccination. Of 1,115 dogs offered a bait, 90% (n = 1,006, 95%CI:91–94) consumed the bait and 72.9% (n = 813, 95%CI:70.2–75.4) of dogs were assessed as being vaccinated by direct observation, while for 11.7% (n = 130, 95%CI:9.9–17.7) the status was recorded as “unkown” and 15.4% (n = 172, 95%CI: 13.4–17.7) were considered as being not vaccinated. Smaller dogs and dogs offered a bait with multiple other dogs had significantly higher vaccination rates, while other factors, e.g. sex, confinement status and time had no influence. The favorable results of this first large-scale field trial further support the strategic integration of ORV into dog rabies control programmes. Given the acceptance of the egg-flavored bait under various settings worldwide, ORV of dogs could become a game-changer in countries, where control strategies using parenteral vaccination alone failed to reach sufficient vaccination coverage in the dog population.

Rabies in dogs can be prevented by vaccination, and this approach has become a cornerstone in the control and eventual elimination of the disease. However, vaccinating hard-to-reach often free-roaming dogs are a challenge and represents one of the challenges to reach sufficient herd-immunity. A potential solution would be to vaccinate these dogs using oral baits filled with a vaccine. In this study we have assessed the acceptability of oral rabies vaccination (ORV) in Namibian dogs under field conditions. The results demonstrate that the method is acceptable both for the owners and the dogs, with a very high uptake of the egg-flavored bait. This supports the potential of ORV to contribute to vaccination programs where parenteral vaccination alone failed to reach sufficient vaccination coverage in the dog population.

Immune Response After Rabies Vaccination in Owned Free-Roaming Domestic Dogs in Flores Island, Indonesia

Vaccination is the main tool to prevent the circulation of rabies in dog populations. The development of an immune response after vaccination differs between individual dogs and depends on many factors such as dog characteristics, management, or genetics. Here, we first investigated the level of, and associated factors for, the presence of binding antibodies in 130 healthy dogs from Flores Island, Indonesia. Secondly, we identified factors associated with the development of binding antibodies within 30 days after vaccination among a subsample of dogs that had a binding antibody titre <0.5 EU/ml at the day of vaccination (D0, N = 91). Blood samples were collected from the individual dogs immediately before vaccination at D0 and 30 days after vaccination (D30). The rabies antibody titres were determined using ELISAs. Information on potential risk factors such as the dog's age and sex, history of vaccination, type and frequency of feeding, and BCS (body condition score) were gathered during interviews at D0. Regression analyses were performed to identify the risk factors associated with the presence of binding antibody titre ≥0.5 EU/ml at D0 for the 130 dogs and the development of binding antibody titre ≥0.5EU/ml at D30 for the 91 dogs. The results showed that the proportion of dogs with antibody titre ≥0.5 EU/ml was 30% (39/130) at D0. The only factors found to be significantly influencing the presence of binding antibodies titres ≥0.5 EU/ml was previous vaccination within 1 year before D0 [46.8 vs. 14.7%, Odds ratio (OR) = 3.6, 95%CI 1.5–9.3; p-value = 0.006], although the same trend was found for dogs of higher age and better BCS. Eighty-six percent (79/91) of dogs whose rabies binding antibody level was <0.5 EU/ml at D0 had developed an adequate immune response (≥0.5 EU/ml) at D30. Almost a significantly higher proportion developed an adequate immune response in dogs of good BCS compared to those of poor BCS (95.3% vs. 79.2%, OR = 4.7, 95%CI 1.1–32.5; p-value = 0.057. Twelve (13.2%) dogs retain binding antibody level <0.5 EU/ml at D30, indicating poor immune response after vaccination. A majority of them did not receive vaccine before D0 according to the owner and had poor BCS (83.3%; 10/12). Our findings show the high effectiveness of rabies vaccine in under field conditions to develop measurable immunity and the importance of a good BCS, often achievable by good dog keeping conditions, for developing efficient immunity after parenteral vaccination in dogs.

Awareness, Knowledge, and Perceptions Regarding Rabies Prevention Among Rural Communities in Masaka District, Central Uganda: A Qualitative Study

Rabies is a zoonotic disease that is mainly transmitted to humans through dog bites. It remains a major public health threat in many Asian and African countries, including Uganda. The main objective of this study was to investigate awareness, knowledge, and perceptions of communities toward human and dog health related to rabies prevention, as well as dog management practices within Masaka district, central Uganda. Data collection involved nine key informant interviews (KIIs) and six focus group discussions (FGDs). Methods used during focus group discussions included qualitative interviews (using open-ended questions), simple ranking, and proportional piling. Data from KIIs and FGDs were analyzed using content analysis in NVivo (version 12.0). This study reveals that community members in the rural settings uses herbal concoctions in replacement or as an alternative to dog vaccination. Furthermore, the study reveals that dogs play the vital roles in the households like as they offer protection to people and household properties, despite being ranked second least among the household animals. The commonest livelihood activity was a small-scale mixed farming. Most of the households kept dogs, but they are ranked at second lowest in terms of economic value among all domestic animals. Free roaming and tethering were the common dog-keeping systems, and home-based feed (food leftovers, bones) was provided mainly to the tethered dogs. Rabies, also locally known as “Eddalu Lyembwa” (that can be translated as “madness of the dogs”), was ranked as the disease of most important among dogs, besides other common diseases such as skin diseases, venereal diseases, worm infestations, and tick infestations. Inadequate vaccination services for both humans and dogs were reported, and dog bite victims traveled a long distance to seek for post-exposure prophylaxis after dog bites. It can be concluded that there is a clear request for periodic mass vaccination campaigns against rabies among dogs, and access to vaccines within reasonable distances by humans after a rabies exposure, but also pre-emptive vaccination for those at high risk, such as veterinarians, needs to be improved.

Rabies in the Tropics

Purpose of Review

Rabies is an ancient yet still neglected tropical disease (NTD). This review focuses upon highlights of recent research and peer-reviewed communications on the underestimated tropical burden of disease and its management due to the complicated dynamics of virulent viral species, diverse mammalian reservoirs, and tens of millions of exposed humans and animals – and how laboratory-based surveillance at each level informs upon pathogen spread and risks of transmission, for targeted prevention and control.

Recent Findings

While both human and rabies animal cases in enzootic areas over the past 5 years were reported to PAHO/WHO and OIE by member countries, still there is a huge gap between these “official” data and the need for enhanced surveillance efforts to meet global program goals.

Summary

A review of the complex aspects of rabies perpetuation in human, domestic animal, and wildlife communities, coupled with a high fatality rate despite the existence of efficacious biologics (but no therapeutics), warrants the need for a One Health approach toward detection via improved laboratory-based surveillance, with focal management at the viral source. More effective methods to prevent the spread of rabies from enzootic to free zones are needed.

Ranging patterns and factors associated with movement in free-roaming domestic dogs in urban Malawi

Rabies is a neglected zoonotic disease that causes around 59,000 deaths per year globally. In Africa, rabies virus is mostly maintained in populations of free-roaming domestic dogs (FRDD) that are predominantly owned. Characterizing the roaming behavior of FRDD can provide relevant information to understand disease spread and inform prevention and control interventions. To estimate the home range (HR) of FRDD and identify predictors of HR size, we studied 168 dogs in seven different areas of Blantyre city, Malawi, tracking them with GPS collars for 1-4 days. The median core HR (HR50) of FRDD in Blantyre city was 0.2 ha (range: 0.08-3.95), while the median extended HR (HR95) was 2.14 ha (range: 0.52-23.19). Multivariable linear regression models were built to identify predictors of HR size. Males presented larger HR95 than females. Dogs living in houses with a higher number of adults had smaller HR95, while those living in houses with higher number of children had larger HR95. Animals that received products of animal origin in their diets had larger HR95, and only in the case of females, animals living in low-income areas had larger HR50 and HR95. In contrast, whether male dogs were castrated or not was not found to be associated with HR size. The results of this study may help inform rabies control and prevention interventions in Blantyre city, such as designing risk-based surveillance activities or rabies vaccination campaigns targeting certain FRDD subpopulations. Our findings can also be used in rabies awareness campaigns, particularly to illustrate the close relationship between children and their dogs.

Analyses of Contact Networks of Community Dogs on a University Campus in Nakhon Pathom, Thailand

Free-roaming dogs have been identified as an important reservoir of rabies in many countries including Thailand. There is a need for novel insights to improve current rabies control strategies in these countries. Network analysis is commonly used to study the interactions between individuals or organizations and has been applied in preventive veterinary medicine. However, contact networks of domestic free-roaming dogs are mostly unexplored. The objective of this study was to explore the contact network of free-roaming dogs residing on a university campus. Three one-mode networks were created using co-appearances of dogs as edges. A two-mode network was created by associating the dog with the pre-defined area it was seen in. The average number of contacts a dog had was 6.74. The normalized degree for the weekend network was significantly higher compared to the weekday network. All one-mode networks displayed small-world network characteristics. Most dogs were observed in only one area. The average number of dogs which shared an area was 8.67. In this study, we demonstrated the potential of observational methods to create networks of contacts. The network information acquired can be further used in network modeling and designing targeted disease control programs.

Loss of binding antibodies against rabies in a vaccinated dog population in Flores Island, Indonesia

Effective parenteral vaccines are available to control rabies in dogs. While such vaccines are successfully used worldwide, the period between vaccine boosters required to guarantee protection of the population against rabies varies between vaccines and populations. In Flores Island, Indonesia, internationally and locally produced rabies vaccines are used during annual vaccination campaigns of predominantly free-roaming owned domestic dogs. The study objective was to identify the duration of the presence and factors associated with the loss of adequate level of binding antibodies (≥0.5 EU/ml) following rabies vaccination in a domestic dog population on Flores Island. A total of 171 dogs that developed an antibody titre higher or equal to 0.5 EU/ml 30 days after vaccination (D30), were repeatedly sampled at day 90, 180, 270, and 360 after vaccination. On the day of vaccination (D0), an interview was performed with dog owners to collect information on dog characteristics (age, sex, body condition score (BCS)), history of rabies vaccination, kind of daily food, frequency of feeding, and origin of the dog. Serum samples were collected and the level of antibodies was quantitatively assessed using ELISA tests. Dogs were categorized as having an adequate level of binding antibodies (≥0.5 EU/ml) or inadequate level of binding antibodies (<0.5 EU/ml) at each time points examined. A total of 115, 72, 23, and 31 dogs were sampled at D90, D180, D270, and D360, respectively, with the highest proportion of antibodies ≥ 0.5 EU/ml (58%, 95% CI, 49-67%) at D90, which reduced gradually until D360 (35%, 95% CI, 19-52%). Multivariable logistic regression models showed that loss of adequate level of binding antibodies is significantly associated with dogs having no history of vaccination or vaccination applied more than 12 months before D0, being less than 12 months of age, and having a poor BCS. These results highlight the importance of BCS regarding the immune response duration and provide insights into frequency of vaccination campaigns required for the internationally available vaccine used on Flores Island. For dogs without vaccination history or vaccination being applied more than 12 months before D0, a booster is recommended within 3 months (a largest drop of antibodies was detected within the first 90 days) after the first vaccination to guarantee measurable protection of the population that lasts at least for one year.