Biology subjects

Apolloni, A.

Publications and source records attributed to Apolloni, A..

6 recordsLinked to original sources

bioRxiv2025

Comparing Livestock Mobility-Informed Strategies for Peste des Petits Ruminants Control in Nigeria: The Central Role of the Network Backbone

Animal mobility is central to pastoral livelihoods and regional trade in West Africa, but it also facilitates the spread of transboundary animal diseases such as Peste des petits ruminants (PPR). In Nigeria, PPR outbreaks recur regularly, yet surveillance and control remain limited in the absence of routine animal-movement tracking. Here, we assess and compare movement-informed control options for PPR using a reconstructed livestock mobility network from a one-time market survey conducted in three northern Nigerian states. We simulate transmission on this network and evaluate three intervention strategies: (i) targeting vulnerable villages, (ii) targeting the links that connect movement communities, and (iii) targeting villages belonging to the network backbone. Across scenarios, backbone-based targeting consistently produced the largest reductions in network connectivity and epidemic outcomes, outperforming strategies focused on vulnerable nodes or inter-community links. These results suggest that backbone-informed control could provide a practical, resource-efficient pathway to strengthen PPR control in settings where routine movement data are scarce.

animal behavior and cognition↗

bioRxiv2025

How fast can PPRV spread? Analyzing the results of an experimental PPRV infection of goats equipped with Ultra-WideBand sensors

Peste des Petits Ruminants (PPR) is a highly contagious disease affecting goats and sheep. The speed and extent of its spread depend on contact patterns and the viruss intrinsic characteristics. To estimate propagation speed and the role of inter-individual patterns, we analyzed the results of a series of 12 experimental infections conducted in five different sessions, involving six or seven goats in a secured stable. In each experiment, one animal was inoculated with the PPR strain and placed in contact with the other naive animals. All the animals were equipped with Ultra-WideBand sensors to collect inter-individual distance data. The duration of this phase varied from 1 to 48 hours across the experiments. Afterwards, the animals were isolated and monitored for three to five weeks. Temperature, symptoms, nasal and ocular discharges, and blood samples were routinely collected to detect the presence of the virus. Using Bayesian statistical analysis, data on inter-individual distances, and health status were analyzed to estimate R0, the incubation period, and PPRV transmissibility. The latter was used to estimate the exposure period, i.e., the minimum amount of time for a naive animal to become infected. Of the 70 naive animals exposed to the virus, 18 were infected. R0 was estimated to be around 4.3 or 8.6, depending on the infectious period value. The incubation period was estimated to be around 16.3 days (95% CI: 12.6-23.3 days). The exposure time varies greatly depending on the density, ranging from nearly two days at low density to around four hours at high density. Large gatherings of animals, such as at livestock markets, could greatly facilitate the spread of PPRV. Furthermore, the long incubation period coupled with livestock mobility could favor the virus geographical dissemination on a large scale. Author summaryPPR is an infectious disease that is transmitted directly and affects goats and sheep. Since its discovery in the Ivory Coast in 1942, the PPR virus has spread worldwide, reaching China in 2010 and Europe in 2018. Despite the fact that PPR poses a huge threat to the lives of small ruminants and the livelihoods of smallholders, more research is needed into its epidemic potential and transmission speed. Here, we used a combined approach of experimental infections and contact tracing with UWB devices to estimate the probability of transmission of a specific PPRV strain, and to determine the minimum exposure time required for an animal to become infected. Our results indicate that reducing the average distance between animals by a factor of four could reduce exposure time tenfold, indicating a much higher risk for high-density herds compared to roaming ones. Coupled with new estimates of R0 and incubation time inferred from data analysis, our work sheds light on the danger posed by PPR. These informations are valuable to veterinarians and policymakers, to better assess the risk of introduction, spread, and impact of PPR, to implement timely and effective interventions.

animal behavior and cognition↗

bioRxiv2025

First detection of Crimean Congo Hemorrhagic Fever antibodies in cattle and wild fauna of southern continental France: investigation of explicative factors

Crimean-Congo Haemorrhagic Fever (CCHF) is a tick-borne zoonosis with significant public health implications due to its expanding geographic distribution and potential for severe outcomes in humans. This study represents the first serological survey conducted in mainland France to detect antibodies against the Crimean-Congo Haemorrhagic Fever Virus (CCHFV) in domestic and wild fauna, providing critical insights into the viruss circulation. We analyzed 8,609 cattle sera and 2,182 wildlife sera collected across the French Mediterranean region from 2008 to 2022, using enzyme-linked immunosorbent assays (ELISA) and pseudo-plaque reduction neutralization tests (PPRNT) for antibody detection and confirmation. Seropositivity was detected in both cattle (2.04%) and wildlife (2.25%), with higher rates observed in specific regions such as Pyrenees-Orientales and Hautes-Pyrenees. These findings reveal spatial clusters of CCHFV circulation and suggest the existence of enzootic transmission cycles involving local tick vectors and animal hosts. Our multivariate analysis identified key factors influencing seropositivity, including animal age, habitat characteristics, and potential wildlife interactions. The presence of natural open habitats and coniferous forests was significantly associated with higher seropositivity in cattle, while sex and geographical variability played a role in wildlife seroprevalence. These findings highlight the importance of environmental and anthropogenic factors in shaping the dynamics of CCHFV transmission. This study demonstrates that CCHFV is actively circulating in parts of mainland France, emphasizing the need for enhanced surveillance and integrated approaches to monitor zoonotic pathogens. It also raises questions about the role of additional tick vectors, such as Hyalomma lusitanicum, in the transmission cycle. These results contribute to a better understanding of CCHF epidemiology and offer valuable guidance for public health strategies to mitigate the risks associated with this emerging disease. Author SummaryCrimean-Congo Haemorrhagic Fever (CCHF) is a severe disease spread by ticks that affects humans and animals. Although the disease is largely distributed in parts of Europe, Africa, and Asia, its presence in France has been uncertain. My study investigated whether the virus causing this disease is circulating in southern mainland France by testing blood samples from domestic animals, like cattle, and wild animals, such as deer and wild boars, for signs of previous infection. I found evidence of the virus in several regions, particularly in the Pyrenees-Orientales, Hautes-Pyrenees and Alpes-maritimes, suggesting that the virus is indeed circulating among animals and ticks in some parts of mainland France. By studying where infected animals were found and considering factors such as age, habitat, and environmental conditions, I identified that older animals seem to have been more often exposed to the virus, as well as animals frequenting open environments favorable to ticks. These findings are important because they show that the disease could potentially spread to new areas and affect human populations. My work highlights the need for ongoing monitoring of ticks and animals for CCHFV epidemiological surveillance and the protection of public health.

ecology↗

bioRxiv2024

Simulating the diffusion of PPR-like disease to improve surveillanc

Animal mobility is a founding element of pastoral culture and fundamental to the economy in West Africa. Herds movement, involving mainly cattle, sheep, and goats, is vital for adapting to climate fluctuations, optimizing natural resources, and managing risks in livestock production, as well as livestock trade and exchanges. However, these movements contribute to the spread of transboundary animal diseases such as Peste des petits ruminants (PPR). Nigeria experienced its first PPR outbreak in the 1960s-1970s, and outbreaks have regularly occurred since then. Yet, no adequate surveillance system has been put in place, and the absence of proper animal movement tracking remains a critical shortcoming in addressing this ongoing threat. Because of this, we rely on ad-hoc activities, like mobility surveys, to collect this information. However, these data could be partial and limited in time and space, hindering the capacity to identify suitable areas for monitoring disease circulation (sentinel nodes). Market survey data from three northern states are collected once to reconstruct the small ruminant mobility network. A group of areas with a high potential to infect each other were identified (Contagion Cluster). A stochastic Susceptible-Infected-Recovered (SIR) was used to simulate the spread of a PPR-like disease through movements. Sentinel nodes and their key characteristics were identified using Random Forest classification. The network (missing movement) was predicted with a hierarchical random graph (HRG), and uncertainty analysis assessed the effects of missing movements on the epidemic extent and identity and characteristics of sentinel nodes. The number of sentinel nodes varied with the epidemics severity, but their characteristics remained consistent. The uncertainty analysis results showed that adding 1% of the most probable missing links did not affect the final size of the epidemic. However, a significant difference appears when adding more than 3% of the missing links, causing a gradual fluctuation in the epidemics final size. The final size of the epidemic stabilized when adding more than 50% of the most probable links. The challenge posed by incomplete animal movement data underscores the need for further research and data collection efforts. However, predicting missing links presents a promising method for enhancing the reliability of epidemic prediction and sentinel node identification. This potential to improve disease surveillance and control strategies is a significant implication of our study.

bioinformatics↗

bioRxiv2024

Assessing the impact of structural modifications in the construction of surveillance network for transboundary animal diseases: the role of backbone and sentinel nodes

Peste des Petits Ruminants (PPR) is a highly contagious disease that mainly affects sheep and goats and is transmitted through livestock movements. Because of its socio-economic impact, the Food and Agriculture Organisation (FAO) and the World Organization for Animal Health (WOAH) have set the goal to eradicate it by 2030, one of the key steps being the improvement of surveillance networks. The present study aimed to provide tools to identify areas that could serve as sentinel nodes, i.e. areas that may be rapidly infected at the onset of epidemics. Using data from a market survey conducted in the Northern Region of Nigeria, we analyzed which nodes, under which conditions, could serve as sentinel nodes. We considered several modified networks to get around the problem of data only being available for part of the overall network structure and to account for potential errors made during the field study. For each configuration, we simulated the spread of PPR using a stochastic Susceptible-Infectious (SI) model based on animal movements to assess the epidemics extent and the presence of recurrent patterns to identify potential sentinel nodes. We extracted the backbone of the reference network and checked for the presence of sentinel nodes within it. We then explored the possibility of using the backbone nodes as sentinel nodes. We investigated how the origin (seed) of the epidemics could affect the propagation pattern by comparing and grouping seeds based on their respective transmission paths. Results showed that the isolated backbone contains 45% sentinel nodes that remain stable or undergo only minor changes in 9 out of 11 configurations. On top of that, the characteristics of sentinel nodes identified in the backbone are not influenced by the severity of the disease. The H index, in-degree, and eigenvector are the most essential variables. This study provides an overview of the major axes of animal movements in Nigeria and the most vulnerable locations that should be prioritized for monitoring livestock diseases like PPR.

animal behavior and cognition↗

bioRxiv2018

Mechanisms for European Bat Lyssavirus subtype 1 persistence in non-synanthropic bats: insights from a modeling study

BackgroundLyssaviruses are pathogens of bat origin of considerable zoonotic concern being the causative agent for rabies disease, however our understanding of their persistence in bat populations remains very scarce.\n\nMethodsLeveraging existing data from an extensive ecological field survey characterizing Myotis myotis and Miniopterus schreibersii bat species in the Catalonia region, we develop a data-driven spatially explicit metapopulation model to identify the mechanisms of the empirically observed persistence of European Bat Lyssavirus subtype 1 (EBLV-1), the most common lyssavirus species found in Europe. We consider different disease progressions accounting for lethal infection, immunity waning, and potential cross-species transmission when the two populations share the same refuge along the migratory path of M. schreibersii.\n\nResultsWe find that EBLV-1 persistence relies on host spatial structure through the migratory nature of M. schreibersii bats, on cross-species mixing with M. myotis population, and on a disease progression leading to survival of infected animals followed by temporary immunity. The higher fragmentation along the northern portion of the migratory path is necessary to maintain EBLV-1 sustained circulation in both species, whereas persistence would not be ensured in the single colony of M. myotis. Our study provides first estimates for the EBLV-1 transmission potential in M. schreibersii bats and average duration of immunity in the host species, yielding values compatible with previous empirical observations in M. myotis bats.\n\nConclusionsHabitats sharing and the strong spatial component of EBLV-1 transmission dynamics identified as key drivers in this ecological context may help understanding the observed spatial diffusion of the virus at a larger scale and across a diverse range of host species, through long-range migration and seeding of local populations. Our approach can be readily adapted to other zoonotic pathogens of public health concern.

epidemiology↗