Assessing animal welfare impact of fourteen control and dispatch methods for house mouse (Mus musculus), Norway rat (Rattus norvegicus) and black rat (Rattus rattus).

Population control of the house mouse (Mus musculus), Norway rat (Rattus norvegicus) and black rat (Rattus rattus) is common practice worldwide. Our objective was to assess the impact on animal welfare of lethal and non-lethal control methods, including three dispatch methods. We used the Sharp and Saunders welfare assessment model with eight experts scoring eleven control methods and three dispatch methods used on the three species. We presumed the methods were performed as prescribed, only taking into account the effect on the target animal (and not, for example, on non-target catches). We did not assess population control efficacy of the methods. Methods considered to induce the least suffering to the target animal were captive-bolt traps, electrocution traps and cervical dislocation, while those with the greatest impact were anticoagulants, cholecalciferol and deprivation. Experts indicated considerable uncertainty regarding their evaluation of certain methods, which emphasises the need for further scientific research. In particular, the impact of hydrogen cyanide, chloralose and aluminium phosphide on animal welfare ought to be investigated. The experts also stressed the need to improve Standard Operating Procedures and to incorporate animal welfare assessments in Integrated Pest Management (IPM). The results of our study can help laypeople, professionals, regulatory agencies and legislators making well-informed decisions as to which methods to use when controlling commensal rodents.

Serologic Surveillance for SARS-CoV-2 Infection among Wild Rodents, Europe.

We report results from serologic surveillance for exposure to SARS-CoV-2 among 1,237 wild rodents and small mammals across Europe. All samples were negative, with the possible exception of 1. Despite suspected potential for human-to-rodent spillover, no evidence of widespread SARS-CoV-2 circulation in rodent populations has been reported to date.Esitämme tulokset serologisesta tutkimuksesta, jossa seulottiin SARS-CoV-2 tartuntojen varalta 1,237 luonnonvaraista jyrsijää ja piennisäkästä eri puolilta Eurooppaa. Kaikki näytteet olivat negatiivisia, yhtä näytettä lukuun ottamatta. SARS-CoV-2:n läikkymisen ihmisistä jyrsijöihin on arveltu olevan mahdollista, mutta todisteet viruksen laajamittaisesta leviämisestä jyrsijäpopulaatioissa puuttuvat.

Historical and genomic data reveal the influencing factors on global transmission velocity of plague during the Third Pandemic.

Quantitative knowledge about which natural and anthropogenic factors influence the global spread of plague remains sparse. We estimated the worldwide spreading velocity of plague during the Third Pandemic, using more than 200 years of extensive human plague case records and genomic data, and analyzed the association of spatiotemporal environmental factors with spreading velocity. Here, we show that two lineages, 2.MED and 1.ORI3, spread significantly faster than others, possibly reflecting differences among strains in transmission mechanisms and virulence. Plague spread fastest in regions with low population density and high proportion of pasture- or forestland, findings that should be taken into account for effective plague monitoring and control. Temperature exhibited a nonlinear, U-shaped association with spread speed, with a minimum around 20 °C, while precipitation showed a positive association. Our results suggest that global warming may accelerate plague spread in warm, tropical regions and that the projected increased precipitation in the Northern Hemisphere may increase plague spread in relevant regions.

The effects of personality on survival and trappability in a wild mouse during a population cycle.

The pace-of-life syndrome (POLS) theory provides an evolutionary explanation for the existence of consistent among-individual variation in behaviour, or animal personality. Herein, individuals with a fast lifestyle are considered to be bolder and should take more risks resulting in a lower life expectancy compared to shyer individuals with a slower lifestyle. However, this assumption depends on the levels of intra-specific competition that the individuals experience which has rarely been tested in species that experience large changes in competition on a very short time scale. We used the multimammate mice (Mastomys natalensis) as a model system to study the POLS assumption by investigating the effects of two personality traits (exploration and stress-sensitivity) on survival, maturation (a proxy for reproductive investment) and recapture probability during one population cycle (Nindividuals = 201). Such a cycle consists of two phases in which the levels of intra-specific competition vary drastically. We found that only one personality trait, namely stress-sensitivity, had a negative effect on both survival and recapture probability but none of them affected maturation. This suggests that less stress-sensitive individuals take more risks in the wild and have a higher survival probability compared to high stress-sensitive individuals. However, the effect of personality on survival was only present during the population decrease phase, when the levels of intra-specific competition are high due to a scarcity of food. This suggests that seasonal changes in competition might be important in the evolution and maintenance of animal personalities in species whose population dynamics have a clear seasonal component.

Population cycles and outbreaks of small rodents: ten essential questions we still need to solve.

Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate over almost a century, we here discuss the driving forces of these different rodent population dynamics. We highlight ten questions directly related to the various characteristics of relevant populations and ecosystems that still need to be answered. This overview is not intended as a complete list of questions but rather focuses on the most important issues that are essential for understanding the generality of small rodent population dynamics.

Role of Wildlife in Emergence of Ebola Virus in Kaigbono (Likati), Democratic Republic of the Congo, 2017.

After the 2017 Ebola virus (EBOV) outbreak in Likati, a district in northern Democratic Republic of the Congo, we sampled small mammals from the location where the primary case-patient presumably acquired the infection. None tested positive for EBOV RNA or antibodies against EBOV, highlighting the ongoing challenge in detecting animal reservoirs for EBOV.

Density dependence and persistence of Morogoro arenavirus transmission in a fluctuating population of its reservoir host.

A key aim in wildlife disease ecology is to understand how host and parasite characteristics influence parasite transmission and persistence. Variation in host population density can have strong impacts on transmission and outbreaks, and theory predicts particular transmission-density patterns depending on how parasites are transmitted between individuals. Here, we present the results of a study on the dynamics of Morogoro arenavirus in a population of multimammate mice (Mastomys natalensis). This widespread African rodent, which is also the reservoir host of Lassa arenavirus in West Africa, is known for its strong seasonal density fluctuations driven by food availability. We investigated to what degree virus transmission changes with host population density and how the virus might be able to persist during periods of low host density. A seven-year capture-mark-recapture study was conducted in Tanzania where rodents were trapped monthly and screened for the presence of antibodies against Morogoro virus. Observed seasonal seroprevalence patterns were compared with those generated by mathematical transmission models to test different hypotheses regarding the degree of density dependence and the role of chronically infected individuals. We observed that Morogoro virus seroprevalence correlates positively with host density with a lag of 1-4 months. Model results suggest that the observed seasonal seroprevalence dynamics can be best explained by a combination of vertical and horizontal transmission and that a small number of animals need to be infected chronically to ensure viral persistence. Transmission dynamics and viral persistence were best explained by the existence of both acutely and chronically infected individuals and by seasonally changing transmission rates. Due to the presence of chronically infected rodents, rodent control is unlikely to be a feasible approach for eliminating arenaviruses such as Lassa virus from Mastomys populations.

When Viruses Don't Go Viral: The Importance of Host Phylogeographic Structure in the Spatial Spread of Arenaviruses.

Many emerging infections are RNA virus spillovers from animal reservoirs. Reservoir identification is necessary for predicting the geographic extent of infection risk, but rarely are taxonomic levels below the animal species considered as reservoir, and only key circumstances in nature and methodology allow intrinsic virus-host associations to be distinguished from simple geographic (co-)isolation. We sampled and genetically characterized in detail a contact zone of two subtaxa of the rodent Mastomys natalensis in Tanzania. We find two distinct arenaviruses, Gairo and Morogoro virus, each spatially confined to a single M. natalensis subtaxon, only co-occurring at the contact zone's centre. Inter-subtaxon hybridization at this centre and a continuum of quality habitat for M. natalensis show that both viruses have the ecological opportunity to spread into the other substaxon's range, but do not, strongly suggesting host-intrinsic barriers. Such barriers could explain why human cases of another M. natalensis-borne arenavirus, Lassa virus, are limited to West Africa.

Discovery and genome characterization of three new Jeilongviruses, a lineage of paramyxoviruses characterized by their unique membrane proteins.

BACKGROUND: In the past decade, many new paramyxoviruses that do not belong to any of the seven established genera in the family Paramyxoviridae have been discovered. Amongst them are J-virus (JPV), Beilong virus (BeiPV) and Tailam virus (TlmPV), three paramyxovirus species found in rodents. Based on their similarities, it has been suggested that these viruses should compose a new genus, tentatively called 'Jeilongvirus'. RESULTS: Here we present the complete genomes of three newly discovered paramyxoviruses, one found in a bank vole (Myodes glareolus) from Slovenia and two in a single, co-infected Rungwe brush-furred rat (Lophuromys machangui) from Mozambique, that represent three new, separate species within the putative genus 'Jeilongvirus'. The genome organization of these viruses is similar to other paramyxoviruses, but like JPV, BeiPV and TlmPV, they possess an additional open reading frame, encoding a transmembrane protein, that is located between the F and G genes. As is the case for all Jeilongviruses, the G genes of the viruses described here are unusually large, and their encoded proteins are characterized by a remarkable amino acid composition pattern that is not seen in other paramyxoviruses, but resembles certain motifs found in Orthopneumovirus G proteins. CONCLUSIONS: The phylogenetic clustering of JPV, BeiPV and TlmPV with the viruses described here, as well as their shared features that set them apart from other paramyxoviruses, provide additional support for the recognition of the genus 'Jeilongvirus'.

Estimating Time of Infection Using Prior Serological and Individual Information Can Greatly Improve Incidence Estimation of Human and Wildlife Infections.

Diseases of humans and wildlife are typically tracked and studied through incidence, the number of new infections per time unit. Estimating incidence is not without difficulties, as asymptomatic infections, low sampling intervals and low sample sizes can introduce large estimation errors. After infection, biomarkers such as antibodies or pathogens often change predictably over time, and this temporal pattern can contain information about the time since infection that could improve incidence estimation. Antibody level and avidity have been used to estimate time since infection and to recreate incidence, but the errors on these estimates using currently existing methods are generally large. Using a semi-parametric model in a Bayesian framework, we introduce a method that allows the use of multiple sources of information (such as antibody level, pathogen presence in different organs, individual age, season) for estimating individual time since infection. When sufficient background data are available, this method can greatly improve incidence estimation, which we show using arenavirus infection in multimammate mice as a test case. The method performs well, especially compared to the situation in which seroconversion events between sampling sessions are the main data source. The possibility to implement several sources of information allows the use of data that are in many cases already available, which means that existing incidence data can be improved without the need for additional sampling efforts or laboratory assays.

Polymorphism in vkorc1 Gene of Natal Multimammate Mice, Mastomys natalensis, in Tanzania.

Resistance of rodents to anticoagulant rodenticides has emerged in several areas across the world. Single nucleotide mutations in the vkorc1 gene have been shown to elicit various levels of anticoagulant resistance, and these mutations are prevalent in several Rattus and Mus musculus populations. In sub-Saharan Africa, the Natal multimammate mouse, Mastomys natalensis, is one of the most damaging pests to crops, and anticoagulant poisons such as bromadiolone are frequently used to control these rodents in agricultural fields. Here, we investigate if vkorc1 shows any polymorphism in natural populations of M. natalensis. We sequenced the third exon of vkorc1 of 162 M. natalensis captured from 14 different agricultural sites in Morogoro Region, Tanzania. In addition to 6 SNPs in the noncoding flanking region, we detected 3 nonsynonymous SNPs in this exon: 10 animals (6.2%) carried a Leu108Val variant, 2 animals (1.2%) an Ala140Thr variant, and 1 animal (0.6 %) an Arg100His variant, all 3 in heterozygous form. Ala140Thr is just one residue from a mutation known to be involved in anticoagulant resistance in Rattus and Mus. While in vitro or in vivo experiments are needed to link vkorc1 genetic polymorphisms to level of VKOR activity and anticoagulant susceptibility, our results suggest that M. natalensis individuals may vary in their response to anticoagulant rodenticides. This is the first vkorc1 sequence data from a species outside the Rattus or Mus genera, and for the first time from a rodent species endemic to Africa.

Pan-African phylogeny of Mus (subgenus Nannomys) reveals one of the most successful mammal radiations in Africa.

BACKGROUND: Rodents of the genus Mus represent one of the most valuable biological models for biomedical and evolutionary research. Out of the four currently recognized subgenera, Nannomys (African pygmy mice, including the smallest rodents in the world) comprises the only original African lineage. Species of this subgenus became important models for the study of sex determination in mammals and they are also hosts of potentially dangerous pathogens. Nannomys ancestors colonized Africa from Asia at the end of Miocene and Eastern Africa should be considered as the place of their first radiation. In sharp contrast with this fact and despite the biological importance of Nannomys, the specimens from Eastern Africa were obviously under-represented in previous studies and the phylogenetic and distributional patterns were thus incomplete. RESULTS: We performed comprehensive genetic analysis of 657 individuals of Nannomys collected at approximately 300 localities across the whole sub-Saharan Africa. Phylogenetic reconstructions based on mitochondrial (CYTB) and nuclear (IRBP) genes identified five species groups and three monotypic ancestral lineages. We provide evidence for important cryptic diversity and we defined and mapped the distribution of 27 molecular operational taxonomic units (MOTUs) that may correspond to presumable species. Biogeographical reconstructions based on data spanning all of Africa modified the previous evolutionary scenarios. First divergences occurred in Eastern African mountains soon after the colonization of the continent and the remnants of these old divergences still occur there, represented by long basal branches of M. (previously Muriculus) imberbis and two undescribed species from Ethiopia and Malawi. The radiation in drier lowland habitats associated with the decrease of body size is much younger, occurred mainly in a single lineage (called the minutoides group, and especially within the species M. minutoides), and was probably linked to aridification and climatic fluctuations in middle Pliocene/Pleistocene. CONCLUSIONS: We discovered very high cryptic diversity in African pygmy mice making the genus Mus one of the richest genera of African mammals. Our taxon sampling allowed reliable phylogenetic and biogeographic reconstructions that (together with detailed distributional data of individual MOTUs) provide a solid basis for further evolutionary, ecological and epidemiological studies of this important group of rodents.

Are the specialized bird ticks, Ixodes arboricola and I. frontalis, competent vectors for Borrelia burgdorferi sensu lato?

Our study tested whether two European bird-specialized ticks, Ixodes arboricola and I. frontalis, can act as vectors in the transmission cycles of Borrelia burgdorferi s.l. The ticks have contrasting ecologies but share songbird hosts (such as the great tit, Parus major) with the generalist I. ricinus which may therefore act as a bridging vector. In the first phase of the experiment, we obtained Borrelia-infected ornithophilic nymphs by exposing larvae to great tits that had previously been exposed to I. ricinus nymphs carrying a community of genospecies (Borrelia garinii, valaisiana, afzelii, burgdorferi s.s., spielmanii). Skin samples showed that birds selectively amplified B. garinii and B. valaisiana. The spirochetes were transmitted to the ornithophilic ticks and survived moulting, leading to infection rates of 16% and 27% in nymphs of I. arboricola and I. frontalis respectively. In the second phase, pathogen-free great tits were exposed to the Borrelia-infected ornithophilic nymphs. None of these ticks were able to infect the birds, as indicated by the tissue samples. Analysis of xenodiagnostic I. ricinus larvae found no evidence for co-feeding or systemic transmission of B. burgdorferi s.l. These outcomes do not support the occurrence of enzootic cycles of Borrelia burgdorferi s.l. involving songbirds and their specialized ornithophilic ticks.

Insertion sequence element single nucleotide polymorphism typing provides insights into the population structure and evolution of Mycobacterium ulcerans across Africa.

Buruli ulcer is an indolent, slowly progressing necrotizing disease of the skin caused by infection with Mycobacterium ulcerans. In the present study, we applied a redesigned technique to a vast panel of M. ulcerans disease isolates and clinical samples originating from multiple African disease foci in order to (i) gain fundamental insights into the population structure and evolutionary history of the pathogen and (ii) disentangle the phylogeographic relationships within the genetically conserved cluster of African M. ulcerans. Our analyses identified 23 different African insertion sequence element single nucleotide polymorphism (ISE-SNP) types that dominate in different areas where Buruli ulcer is endemic. These ISE-SNP types appear to be the initial stages of clonal diversification from a common, possibly ancestral ISE-SNP type. ISE-SNP types were found unevenly distributed over the greater West African hydrological drainage basins. Our findings suggest that geographical barriers bordering the basins to some extent prevented bacterial gene flow between basins and that this resulted in independent focal transmission clusters associated with the hydrological drainage areas. Different phylogenetic methods yielded two well-supported sister clades within the African ISE-SNP types. The ISE-SNP types from the "pan-African clade" were found to be widespread throughout Africa, while the ISE-SNP types of the "Gabonese/Cameroonian clade" were much rarer and found in a more restricted area, which suggested that the latter clade evolved more recently. Additionally, the Gabonese/Cameroonian clade was found to form a strongly supported monophyletic group with Papua New Guinean ISE-SNP type 8, which is unrelated to other Southeast Asian ISE-SNP types.

Plague epizootic cycles in Central Asia.

Infection thresholds, widely used in disease epidemiology, may operate on host abundance and, if present, on vector abundance. For wildlife populations, host and vector abundances often vary greatly across years and consequently the threshold may be crossed regularly, both up- and downward. Moreover, vector and host abundances may be interdependent, which may affect the infection dynamics. Theory predicts that if the relevant abundance, or combination of abundances, is above the threshold, then the infection is able to spread; if not, it is bound to fade out. In practice, though, the observed level of infection may depend more on past than on current abundances. Here, we study the temporal dynamics of plague (Yersinia pestis infection), its vector (flea) and its host (great gerbil) in the PreBalkhash region in Kazakhstan. We describe how host and vector abundances interact over time and how this interaction drives the dynamics of the system around the infection threshold, consequently affecting the proportion of plague-infected sectors. We also explore the importance of the interplay between biological and detectability delays in generating the observed dynamics.

Puumala hantavirus infection alters the odour attractiveness of its reservoir host.

The random-mixing assumptions of many parasite-transmission models are challenged if healthy individuals can alter their behaviour to reduce their risk of infection. Some pathogens reduce the attractiveness of their hosts' excretions, for example, potentially altering contact rates and thus the predicted force of infection for pathogens transmissible by contact with excretions. For bank voles (Myodes glareolus), contact with contaminated urine is an important route of transmission for Puumala hantavirus (PUUV); however, it is not known whether PUUV infection changes the voles' urinary odours or their attractiveness. Here, we use a Y-maze to test whether PUUV infection alters the attractiveness of male bank voles' urine. We presented wild-caught PUUV-free male and female bank voles with PUUV-infected conspecific urine, uninfected urine and a water control, and measured the relative and absolute latency to first visit, number of visits, and total time bank voles spent investigating each treatment over 30 min. PUUV infection significantly altered the bank voles' initial response to conspecific urine, with fewer visits and less time spent close to infected urine relative to uninfected urine, and less total time spent near the infected urine than the uninfected urine or control. These strong preferences weakened over the 30-min trial, however, partly due to a general decline in male activity, and there were no absolute differences between the treatments overall. This suggests that PUUV infection does change the attractiveness of bank vole urine to conspecifics, and we discuss the implications of these results for random-mixing assumptions.

Variable effects of host characteristics on species richness of flea infracommunities in rodents from three continents.

We studied the effect of host gender and body mass on species richness of flea infracommunities in nine rodent host species from three biomes (temperate zone of central Europe, desert of the Middle East and the tropics of East Africa). Using season- and species-specific generalized linear mixed models and controlling for year-to-year variation, spatial clustering of rodent sampling and over-dispersion of the data, we found inconsistent associations between host characteristics and flea species richness. We found strong support for male-biased flea parasitism, especially during the reproductive period (higher species richness in male hosts than in females) in all considered European rodents (Apodemus agrarius, Myodes glareolus and Microtus arvalis) and in one rodent species from the Middle East (Dipodillus dasyurus). In contrast, two of three African rodent species (Lophuromys kilonzoi and Praomys delectorum) demonstrated a trend of female-biased flea species richness. Positive associations between body mass and the number of flea species were detected mainly in males (five of nine species: A. agrarius, M. glareolus, M. arvalis, D. dasyurus and Mastomys natalensis) and not in females (except for M. natalensis). The results of this study support earlier reports that gender-biased, in general, and male-biased, in particular, infestation by ectoparasites is not a universal rule. This suggests that mechanisms of parasite acquisition by an individual host are species-specific and have evolved independently in different rodent host-flea systems.

Lions select larger prey in a Central African protected area with increasingly effective management.

Lions and their prey are threatened across most of their range and especially in West and Central Africa. Prey availability influences carnivore densities, social structure, prey preference and home ranges, and changes in prey are important for carnivore management. Scarcity of large prey in many West and Central African ecosystems has been described as leading to a preference for hunting smaller prey in smaller groups. Here we investigated the changes in prey selection of lions in Zakouma National Park (Chad), a protected area in Central Africa that showed significant recovery in wildlife numbers, by collecting feeding data through observations of lions on kills during monitoring drives and GPS cluster points of lion collars. Compared to similar data collected prior to this significant recovery, lions preferred larger prey and fed in larger groups. Our results show that diet shifts due to prey losses can be reversed with restoration of prey populations thanks to improved management, and we speculate that this may be true across large carnivores and across regions.

A century of medical records reveal earlier onset of the malaria season in Haut-Katanga induced by climate change.

BACKGROUND: Despite worldwide efforts to eradicate malaria over the past century, the disease remains a significant challenge in the Democratic Republic of the Congo (DRC) today. Climate change is even anticipated to worsen the situation in areas with higher altitudes and vulnerable populations. This study in Haut-Katanga, a highland region, aims to evaluate the effectiveness of past control measures and to explore the impact of climate change on the region's distinct seasonal malaria pattern throughout the last century. METHODS: We integrated colonial medical records (1917-1983) from two major mining companies (Union Minière du Haut-Katanga and the Générale des Carrières et des Mines) with contemporary data (2003-2020) from Lubumbashi. Concurrently, we combined colonial climate records (1912-1946) with recent data from satellite images and weather stations (1940-2023). We used Generalised Additive Models to link the two data sources and to test for changing seasonal patterns in transmission. RESULTS: Malaria transmission in Haut-Katanga has fluctuated significantly over the past century, influenced by evolving control strategies, political conditions and a changing climate. A notable decrease in cases followed the introduction of dichlorodiphenyltrichloroethane (DDT), while a surge occurred after the civil wars ended at the beginning of the new millennium. Recently, the malaria season began 1-2 months earlier than historically observed, likely due to a 2-5°C increase in mean minimum temperatures, which facilitates the sporogonic cycle of the parasite. CONCLUSION: Despite contemporary control efforts, malaria incidence in Haut-Katanga is similar to levels observed in the 1930s, possibly influenced by climate change creating optimal conditions for malaria transmission. Our historical data shows that the lowest malaria incidence occurred during periods of intensive DDT use and indoor residual spraying. Consequently, we recommend the systematic reduction of vector populations as a key component of malaria control strategies in highland regions of sub-Saharan Africa.