Effects of reduced kinematic and social play experience on affective appraisal of human-rat play in rats.

BACKGROUND: Play is a common and developmentally important behaviour in young mammals. Specifically in Norway rats (Rattus norvegicus), reduced opportunity to engage in rough-and-tumble (RT) play has been associated with impaired development in social competence. However, RT play is a complex behaviour having both a kinematic aspect (i.e., performing complex 3D manoeuvres during play fights) and a social aspect (interacting with a playful partner). There has been little research so far on disentangling the two aspects in RT play, especially on how these two aspects affect the affective appraisal of the intense physical contact during play. RESULTS: To examine the developmental effects of kinematic and social play reduction on affective appraisal in rats, we subjected male Long-Evans rats from 21 days old to RT play experience that was reduced either kinematically (through playing in a low ceiling environment) or socially (through playing with a less playful Fischer-344 rat). Starting at 35 days, we measured their production of positively (50-kHz) and negatively (22-kHz) valenced ultrasonic vocalisations (USVs) in a 2-min standardised human-rat play procedure that mimicked the playful sequences of nape contact, pinning, and belly stimulation ('tickling') for ten days. We hypothesised that the rats with kinematically or socially reduced play would perceive the 'tickling' less positively and thus emit positive ultrasonic vocalisations at lower rates compared to control rats with non-reduced play experience. Our results confirmed that each of the treatments reduced play differently: while the kinematic reduction abolished playful pinnings entirely, the social reduction decreased the pinnings and made play highly asymmetric. During the tickling procedure, rats mostly produced 50 kHz USV, indicating that they appraised the procedure as positive. There was a wide inter individual variance and high individual consistency in rats' USV responses to 'tickling'. Crucially, neither the kinematically nor the socially reduced play experience affected either type of USV production when rats were 'tickled'. CONCLUSIONS: This finding indicates that the ability to appraise play-like interactions as positive remains unaffected even when the kinematic or the social aspect of play experience was substantially curtailed.

Proteomics-Based Identification of Retinal Protein Networks Impacted by Elevated Intraocular Pressure in the Hypertonic Saline Injection Model of Experimental Glaucoma.

Elevated intraocular pressure is considered a major cause of glaucomatous retinal neurodegeneration. To facilitate a better understanding of the underlying molecular processes and mechanisms, we report a study focusing on alterations of the retina proteome by induced ocular hypertension in a rat model of the disease. Glaucomatous processes were modeled through sclerosing the aqueous outflow routes of the eyes by hypertonic saline injections into an episcleral vein. Mass spectrometry-based quantitative retina proteomics using a label-free shotgun methodology identified over 200 proteins significantly affected by ocular hypertension. Various facets of glaucomatous pathophysiology were revealed through the organization of the findings into protein interaction networks and by pathway analyses. Concentrating on retinal neurodegeneration as a characteristic process of the disease, elevated intraocular pressure-induced alterations in the expression of selected proteins were verified by targeted proteomics based on nanoflow liquid chromatography coupled with nano-electrospray ionization tandem mass spectrometry using the parallel reaction monitoring method of data acquisition. Acquired raw data are shared through deposition to the ProteomeXchange Consortium (PXD042729), making a retina proteomics dataset on the selected animal model of glaucoma available for the first time.

The smell of cooperation: rats increase helpful behaviour when receiving odour cues of a conspecific performing a cooperative task.

Reciprocity can explain cooperative behaviour among non-kin, where individuals help others depending on their experience in previous interactions. Norway rats (Rattus norvegicus) cooperate reciprocally according to direct and generalized reciprocity. In a sequence of four consecutive experiments, we show that odour cues from a cooperating conspecific are sufficient to induce the altruistic help of rats in a food-exchange task. When rats were enabled to help a non-cooperative partner while receiving olfactory information from a rat helping a conspecific in a different room, they helped their non-cooperative partner as if it was a cooperative one. We further show that the cues inducing altruistic behaviour are released during the act of cooperation and do not depend on the identity of the cue provider. Remarkably, olfactory cues seem to be more important for cooperation decisions than experiencing a cooperative act per se. This suggests that rats may signal their cooperation propensity to social partners, which increases their chances to receive help in return.

Reciprocity: Different behavioural strategies, cognitive mechanisms and psychological processes.

Reciprocity is probably one of the most debated theories in evolutionary research. After more than 40 years of research, some scientists conclude that reciprocity is an almost uniquely human trait mainly because it is cognitively demanding. Others, however, conclude that reciprocity is widespread and of great importance to many species. Yet, it is unclear how these species reciprocate, given its apparent cognitive complexity. Therefore, our aim was to unravel the psychological processes underlying reciprocity. By bringing together findings from studies investigating different aspects of reciprocity, we show that reciprocity is a rich concept with different behavioural strategies and cognitive mechanisms that require very different psychological processes. We reviewed evidence from three textbook examples, i.e. the Norway rat, common vampire bat and brown capuchin monkey, and show that the species use different strategies and mechanisms to reciprocate. We continue by examining the psychological processes of reciprocity. We show that the cognitive load varies between different forms of reciprocity. Several factors can lower the memory demands of reciprocity such as distinctiveness of encounters, memory of details and network size. Furthermore, there are different information operation systems in place, which also vary in their cognitive load due to assessing the number of encounters and the quality and quantity of help. We conclude that many species possess the psychological processes to show some form of reciprocity. Hence, reciprocity might be a widespread phenomenon that varies in terms of strategies and mechanisms.

Small GTPase Immunity-Associated Proteins Mediate Resistance to Toxoplasma gondii Infection in Lewis Rat.

Rats vary in their susceptibilities to Toxoplasma gondii infection depending on the rat strain. Compared to the T. gondii-susceptible Brown Norway (BN) rat, the Lewis (LEW) rat is extremely resistant to T. gondii Thus, these two rat strains are ideal models for elucidating host mechanisms that are important for host resistance to T. gondii infection. Therefore, in our efforts to unravel molecular factors directing the protective early innate immune response in the LEW rat, we performed RNA sequencing analysis of the LEW versus BN rat with or without T. gondii infection. We identified three candidate small GTPase immunity-associated proteins (GIMAPs) that were upregulated (false discovery rate, 0.05) in the LEW rat in response to T. gondii infection. Subsequently, we engineered T. gondii-susceptible NR8383 rat macrophage cells for overexpression of LEW rat-derived candidate GIMAP 4, 5, and 6. By immunofluorescence analysis we observed that GIMAP 4, 5, and 6 in T. gondii-infected NR8383 cells each colocalized with GRA5, a parasite parasitophorous vacuole membrane (PVM) marker protein, suggesting their translocation to the PVM. Interestingly, overexpression of each candidate GIMAP in T. gondii-infected NR8383 cells induced translocation of LAMP1, a lysosome marker protein, to the T. gondii surface membrane. Importantly, overexpression of GIMAP 4, 5, or 6 individually inhibited intracellular T. gondii growth, with GIMAP 4 having the highest inhibitory effect. Together, our findings indicate that upregulation of GIMAP 4, 5, and 6 contributes to the robust refractoriness of the LEW rat to T. gondii through induction of lysosomal fusion to the otherwise nonfusogenic PVM.

Effects of Culling on Leptospira interrogans Carriage by Rats.

We found that lethal, urban rat control is associated with a significant increase in the odds that surviving rats carry Leptospira interrogans. Our results suggest that human interventions have the potential to affect and even increase the prevalence of zoonotic pathogens within rat populations.

Inherent Oxidative Stress in the Lewis Rat Is Associated with Resistance to Toxoplasmosis.

The course of Toxoplasma gondii infection in rats closely resembles that in humans. However, compared to the Brown Norway (BN) rat, the Lewis (LEW) rat is extremely resistant to T. gondii infection. Thus, we performed RNA sequencing analysis of the LEW rat versus the BN rat, with or without T. gondii infection, in order to unravel molecular factors directing robust and rapid early T. gondii-killing mechanisms in the LEW rat. We found that compared to the uninfected BN rat, the uninfected LEW rat has inherently higher transcript levels of cytochrome enzymes (Cyp2d3, Cyp2d5, and Cybrd1, which catalyze generation of reactive oxygen species [ROS]), with concomitant higher levels of ROS. Interestingly, despite having higher levels of ROS, the LEW rat had lower transcript levels for antioxidant enzymes (lactoperoxidase, microsomal glutathione S-transferase 2 and 3, glutathione S-transferase peroxidase kappa 1, and glutathione peroxidase) than the BN rat, suggesting that the LEW rat maintains cellular oxidative stress that it tolerates. Corroboratively, we found that scavenging of superoxide anion by Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) decreased the refractoriness of LEW rat peritoneal cells to T. gondii infection, resulting in proliferation of parasites in LEW rat peritoneal cells which, in turn, led to augmented cell death in the infected cells. Together, our results indicate that the LEW rat maintains inherent cellular oxidative stress that contributes to resistance to invading T. gondii, and they thus unveil new avenues for developing therapeutic agents targeting induction of host cell oxidative stress as a mechanism for killing T. gondii.

COMPROMISED FERTILITY IN FREE FEEDING OF WILD-CAUGHT NORWAY RATS (RATTUS NORVEGICUS) WITH A LIQUID BAIT CONTAINING 4-VINYLCYCLOHEXENE DIEPOXIDE AND TRIPTOLIDE.

Wild rat pests in the environment cause crop and property damage and carry disease. Traditional methods of reducing populations of these pests involve poisons that can cause accidental exposures in other animals and humans. Fertility management with nonlethal chemicals would be an improved method of rat pest population control. Two chemicals known to target ovarian function in female rats are 4-vinylcyclohexene diepoxide (VCD) and triptolide. Additionally, triptolide impairs spermatogenesis in males. A liquid bait containing no active ingredients (control), or containing triptolide (0.001%) and VCD (0.109%; active) was prepared to investigate the potential use of these agents for wild rat pest population control. Liquid bait was made available to male (n = 8 control; n = 8 active) and female (n = 8 control; n = 8 active) Sprague Dawley rats ( Rattus norvegicus ) for oral consumption prior to breeding. Whereas, control bait-treated females produced normal-sized litters (10.0 ± 1.7 pups/litter), treated females delivered no pups. Wild Norway male (n = 20) and female (n = 20) rats ( Rattus norvegicus ) were trapped, individually housed, and one group given free access to control bait, one group to active bait. Following three cycles of treatment-matched mating pairs, females consuming control bait (control) produced normal litter sizes (9.73 ± 0.73 pups/litter). Females who had consumed active bait (treated) produced no litters on breeding cycles one and two; however, 2 of 10 females produced small litters on the third mating cycle. In a fourth breeding cycle, control females were crossmated with treated males, and treated females were crossmated with control males. In both groups, some dams produced litters, while others did not. The differences in response reflect a heterogeneity in return to cyclicity between females. These results suggest a potential approach to integrated pest management by compromising fertility, and could provide a novel alternative to traditional poisons for reducing populations of wild rat pests.

Activation of GPR30 improves exercise capacity and skeletal muscle strength in senescent female Fischer344 × Brown Norway rats.

The molecular mechanisms of muscle weakness and sarcopenia in postmenopausal women are largely unknown. To determine the effect of a new estrogen receptor, GPR30, in the maintenance of exercise capacity and skeletal muscle function in females, the selective GPR30 agonist, G1 (100 µg/kg/day), or vehicle (V, soybean oil) was administered subcutaneously daily (n = 7 per group) to ovariectomized (OVX) 27-month-old Fischer 344 × Brown Norway (F344BN) female rats. Following 8 weeks of treatment, the exercise capacity (treadmill walk time to exhaustion) was reduced in OVX vs. sham rats (5.1 ± 1.4 vs. 11.0 ± 0.9 min, P < 0.05), and chronic G1 restored exercise capacity (12.9 ± 1.2 min; P < 0.05 vs. OVX-V). Similarly, the peak twitch of electrically stimulated soleus muscles was decreased by 22% in OVX vs. sham rats (P < 0.05), and G1 attenuated this decline (P < 0.05). Western blot analysis showed that chronic G1 treatment attenuated OVX-associated decreases in heat shock protein (HSP) 90, HSP70, and HSP27 expressions. In vitro studies using the L6 myoblast cell line demonstrated that G1 increased mRNA levels of HSPs in cultured cells. Collectively, these data demonstrate that the activation of GPR30 mitigates the adverse effects of estrogen loss on exercise capacity and skeletal muscle contractile function in old F344BN rats. The protective effects of GPR30 might be through its upregulation of heat shock proteins in skeletal muscle.

A novel inhaled Syk inhibitor blocks mast cell degranulation and early asthmatic response.

Spleen tyrosine kinase (Syk) is essential for signal transduction of immunoreceptors. Inhibition of Syk abrogates mast cell degranulation and B cell responses. We hypothesized that Syk inhibition in the lung by inhaled route could block airway mast cells degranulation and the early asthmatic response without the need of systemic exposure. We discovered LAS189386, a novel Syk inhibitor with suitable properties for inhaled administration. The aim of this study was to characterize the in vitro and in vivo profile of LAS189386. The compound was profiled in Syk enzymatic assay, against a panel of selected kinases and in Syk-dependent cellular assays in mast cells and B cells. Pharmacokinetics and in vivo efficacy was assessed by intratracheal route. Airway resistance and mast cell degranulation after OVA challenge was evaluated in an ovalbumin-sensitized Brown Norway rat model. LAS189386 potently inhibits Syk enzymatic activity (IC50 7.2 nM), Syk phosphorylation (IC50 41 nM), LAD2 cells degranulation (IC50 56 nM), and B cell activation (IC50 22 nM). LAS189386 inhibits early asthmatic response and airway mast cell degranulation without affecting systemic mast cells. The present results support the hypothesis that topical inhibition of Syk in the lung, without systemic exposure, is sufficient to inhibit EAR in rats. Syk inhibition by inhaled route constitutes a promising therapeutic option for asthma.

Spinal mediation of motor learning and memory in the rat fetus.

Fetal rats can alter patterns of interlimb coordination after experience with a yoke that links two legs together. Yoke training results in a pronounced increase in conjugate limb movements (CLM). To determine whether yoke motor learning is mediated by spinal cord circuitry, fetal subjects at embryonic Day 20 (E20) received yoke training after mid-thoracic spinal cord transection or sham surgery. Both spinal and sham-treated fetuses exhibited an increase in CLM during training. In a second experiment, fetuses received initial yoke training, then were transected or sham treated before a 2nd training. Spinal and sham fetuses that were yoked during both training sessions exhibited a more rapid rise in CLM than those yoked only in the later session. These findings indicate that motor learning in fetal rats can be supported by spinal cord circuitry alone, and that savings implies a form of motor memory localized in the spinal cord.

The modulation of large airway smooth muscle phenotype and effects of epidermal growth factor receptor inhibition in the repeatedly allergen-challenged rat.

Allergen challenges induce airway hyperresponsiveness (AHR) and increased airway smooth muscle (ASM) mass in the sensitized rat. Whether the remodeled ASM changes its phenotype is uncertain. We examined, in sensitized Brown Norway rats, the effects of multiple ovalbumin (Ova) challenges on ASM remodeling and phenotype and the role of the epidermal growth factor receptor (EGFR) in these processes. Rats were sensitized with Ova and challenged three times at 5-day intervals with phosphate-buffered saline or Ova and pretreated with the EGFR inhibitor AG-1478 (5 mg/kg) or its vehicle dimethyl sulfoxide. Ova challenges increased ASM mass in all-sized airways and in large airway mRNA expression of smooth muscle myosin heavy chain (sm-MHC), assessed by laser capture. Myosin light chain kinase and the fast myosin isoform SM-B mRNA expressions were not affected. Ova induced AHR to methacholine, and, based on the constant-phase model, this was largely attributable to the small airways and lung derecruitment at 48 h that recovered by 1 wk. The EGFR ligands amphiregulin and heparin-binding epidermal growth factor (HB-EGF) were increased in bronchoalveolar lavage fluid at 48 h after Ova exposure. AG-1478 inhibited AHR and prevented ASM growth. Epithelial gene expression of EGFR, HB-EGF, matrix metalloproteinase (MMP)-9, Gro-α, and transforming growth factor-ß was unaffected by Ova challenges. We conclude that EGFR drives remodeling of ASM, which results from repeated Ova challenge. Furthermore, the latter results in excessive small airway and, to a lesser degree, large airway narrowing to methacholine, and large airway gene expression of contractile protein is conserved.

Oral administration of drugs with hypersensitivity potential induces germinal center hyperplasia in secondary lymphoid organ/tissue in Brown Norway rats, and this histological lesion is a promising candidate as a predictive biomarker for drug hypersensitivity occurrence in humans.

It is important to evaluate the potential of drug hypersensitivity as well as other adverse effects during the preclinical stage of the drug development process, but validated methods are not available yet. In the present study we examined whether it would be possible to develop a new predictive model of drug hypersensitivity using Brown Norway (BN) rats. As representative drugs with hypersensitivity potential in humans, phenytoin (PHT), carbamazepine (CBZ), amoxicillin (AMX), and sulfamethoxazole (SMX) were orally administered to BN rats for 28days to investigate their effects on these animals by examinations including observation of clinical signs, hematology, determination of serum IgE levels, histology, and flow cytometric analysis. Skin rashes were not observed in any animals treated with these drugs. Increases in the number of circulating inflammatory cells and serum IgE level did not necessarily occur in the animals treated with these drugs. However, histological examination revealed that germinal center hyperplasia was commonly induced in secondary lymphoid organs/tissues in the animals treated with these drugs. In cytometric analysis, changes in proportions of lymphocyte subsets were noted in the spleen of the animals treated with PHT or CBZ during the early period of administration. The results indicated that the potential of drug hypersensitivity was identified in BN rat by performing histological examination of secondary lymphoid organs/tissues. Data obtained herein suggested that drugs with hypersensitivity potential in humans gained immune reactivity in BN rat, and the germinal center hyperplasia induced by administration of these drugs may serve as a predictive biomarker for drug hypersensitivity occurrence.

The stop-feed effect of cholecalciferol (vitamin D3) and the efficacy of brodifacoum combined with cholecalciferol in Y139C-resistant Norway rats (Rattus norvegicus).

Second-generation anticoagulant rodenticides potentially build persistent residues in animals and accordingly pose a risk of secondary poisoning. We examined the effect of a low concentration of cholecalciferol in brodifacoum bait on bait consumption by Norway rats (Rattus norvegicus Berkenhout 1769) and on the control success in a laboratory study and in field trials. Additionally, the efficacy of both baits was determined against resistant Y139C rats. Cholecalciferol caused a strong stop-feed effect after two days in the laboratory study. On two field study sites each, bait containing either 25 mg kg-1 brodifacoum or 25 mg kg-1 brodifacoum and 100 mg kg-1 cholecalciferol was applied to treat infestations of Norway rats. Infestations were assessed pre- and post-treatment. Rats were radio-tagged, and carcasses were searched for during the treatment period. DNA of each rat was genotyped to determine the resistance status conferred by the VKORC1 gene. On all farms, control success exceeded 90%. On farms treated with brodifacoum only, the ratio of total bait consumption to pre-treatment census was significantly higher (6.6 and 4.8 times) than on farms treated with the combination (2.7 and 2.9 times). 78.8% of 183 rats were confirmed Y139C resistant. Bait ingestion was reduced by almost fifty per-cent when cholecalciferol was added to the bait with no impact on control success. All treatments resulted in control levels exceeding 90%, despite a high proportion of anticoagulant-resistant rats. When the use of highly toxic compounds is required in resistance management, addition of cholecalciferol to these baits may reduce the transfer of residues to the environment.

The "Second Life" of laboratory rats (Rattus norvegicus): Assessment of social behavior of a colony of rats based on social network analysis.

Rattus norvegicus is a social animal and holds a significant economic value, considering its use in scientific research. Here, we use the Social Network Analysis (SNA) approach to study the social interactions of a group of rats held in a post-laboratory animal care facility. We collected interaction data during four study periods, for a total of 60 days. At the group level, rats presented two communities for each study period, consisting mainly of littermates. At individual level, we found that the rats preferred to interact with individuals of the same strain and laboratory of origin and with littermates. At temporal level, we studied how stable social interactions were over time. During the first study period, we found high social stability, whereas the introduction of new individuals in the subsequent period caused social rearrangements; however, the initial social stability was restored. Our findings have shown that studying the social behavior of rats using SNA is a valuable tool for advancing our understanding of the social system of this species, which has the potential to enhance management and welfare practices.

Pet Rats as the Likely Reservoir for Human Seoul Orthohantavirus Infection.

Seoul orthohantavirus (SEOV) is a rat-associated zoonotic pathogen with an almost worldwide distribution. In 2019, the first autochthonous human case of SEOV-induced hemorrhagic fever with renal syndrome was reported in Germany, and a pet rat was identified as the source of the zoonotic infection. To further investigate the SEOV reservoir, additional rats from the patient and another owner, all of which were purchased from the same vendor, were tested. SEOV RNA and anti-SEOV antibodies were found in both of the patient's rats and in two of the three rats belonging to the other owner. The complete coding sequences of the small (S), medium (M), and large (L) segments obtained from one rat per owner exhibited a high sequence similarity to SEOV strains of breeder rat or human origin from the Netherlands, France, the USA, and Great Britain. Serological screening of 490 rats from breeding facilities and 563 wild rats from Germany (2007-2020) as well as 594 wild rats from the Netherlands (2013-2021) revealed 1 and 6 seropositive individuals, respectively. However, SEOV RNA was not detected in any of these animals. Increased surveillance of pet, breeder, and wild rats is needed to identify the origin of the SEOV strain in Europe and to develop measures to prevent transmission to the human population.

Large-scale identification of rodenticide resistance in Rattus norvegicus and Mus musculus in the Netherlands based on Vkorc1 codon 139 mutations.

BACKGROUND: Resistance to rodenticides has been reported globally and poses a considerable problem for efficacy in pest control. The most-documented resistance to rodenticides in commensal rodents is associated with mutations in the Vkorc1 gene, in particular in codon 139. Resistance to anticoagulant rodenticides has been reported in the Netherlands since 1989. A study from 2013 showed that 25% of 169 Norway rats (Rattus norvegicus) had a mutation at codon 139 of the Vkorc1 gene. To gain insight in the current status of rodenticide resistance amongst R. norvegicus and house mice Mus musculus in the Netherlands, we tested these rodents for mutations in codon 139 of the Vkorc1 gene. In addition, we collected data from pest controllers on their use of rodenticides and experience with rodenticide resistance. RESULTS: A total of 1801 rodent samples were collected throughout the country consisting of 1404 R. norvegicus and 397 M. musculus. In total, 15% of R. norvegicus [95% confidence interval (CI): 13-17%] and 38% of M. musculus (95% CI: 33-43%) carried a genetic mutation at codon 139 of the Vkorc1 gene. CONCLUSION: This study demonstrates genetic mutations at codon 139 of the Vkorc1 gene in M. musculus in the Netherlands. Resistance to anticoagulant rodenticides is present in R. norvegicus and M. musculus in multiple regions in the Netherlands. The results of this comprehensive study provide a baseline and facilitate trend analyses of Vkorc1 codon 139 mutations and evaluation of integrated pest management (IPM) strategies as these are enrolled in the Netherlands. © 2022 The Dutch Pest and Wildlife. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Linking rattiness, geography and environmental degradation to spillover Leptospira infections in marginalised urban settings: An eco-epidemiological community-based cohort study in Brazil.

Background: Zoonotic spillover from animal reservoirs is responsible for a significant global public health burden, but the processes that promote spillover events are poorly understood in complex urban settings. Endemic transmission of Leptospira, the agent of leptospirosis, in marginalised urban communities occurs through human exposure to an environment contaminated by bacteria shed in the urine of the rat reservoir. However, it is unclear to what extent transmission is driven by variation in the distribution of rats or by the dispersal of bacteria in rainwater runoff and overflow from open sewer systems. Methods: We conducted an eco-epidemiological study in a high-risk community in Salvador, Brazil, by prospectively following a cohort of 1401 residents to ascertain serological evidence for leptospiral infections. A concurrent rat ecology study was used to collect information on the fine-scale spatial distribution of 'rattiness', our proxy for rat abundance and exposure of interest. We developed and applied a novel geostatistical framework for joint spatial modelling of multiple indices of disease reservoir abundance and human infection risk. Results: The estimated infection rate was 51.4 (95%CI 40.4, 64.2) infections per 1000 follow-up events. Infection risk increased with age until 30 years of age and was associated with male gender. Rattiness was positively associated with infection risk for residents across the entire study area, but this effect was stronger in higher elevation areas (OR 3.27 95% CI 1.68, 19.07) than in lower elevation areas (OR 1.14 95% CI 1.05, 1.53). Conclusions: These findings suggest that, while frequent flooding events may disperse bacteria in regions of low elevation, environmental risk in higher elevation areas is more localised and directly driven by the distribution of local rat populations. The modelling framework developed may have broad applications in delineating complex animal-environment-human interactions during zoonotic spillover and identifying opportunities for public health intervention. Funding: This work was supported by the Oswaldo Cruz Foundation and Secretariat of Health Surveillance, Brazilian Ministry of Health, the National Institutes of Health of the United States (grant numbers F31 AI114245, R01 AI052473, U01 AI088752, R01 TW009504 and R25 TW009338); the Wellcome Trust (102330/Z/13/Z), and by the Fundação de Amparo à Pesquisa do Estado da Bahia (FAPESB/JCB0020/2016). MTE was supported by a Medical Research UK doctorate studentship. FBS participated in this study under a FAPESB doctorate scholarship.

Genome characterization, prevalence and tissue distribution of astrovirus, hepevirus and norovirus among wild and laboratory rats (Rattus norvegicus) and mice (Mus musculus) in Hungary.

Rodents including rats are reservoir of several pathogens capable of affecting human health. In this study, faecal and different organ specimens from free-living Norway rats (Rattus norvegicus) (N = 18) and faecal samples from laboratory rodents (rats N = 21 and mice N = 20) collected from different geographic areas in Hungary between 2017 and 2020 were investigated by viral metagenomics and conventional RT-PCR methods. The complete genome of three different RNA viruses, rat astrovirus, rat norovirus and rat hepevirus were characterized and analysed in detail. Rat norovirus was detected in faecal (17.6%, 3/17) and kidney (7.1%, 1/14) samples; rat astrovirus in faecal (23.5%, 4/17) and spleen (13.3%, 2/15) samples, and rat hepevirus in 43% to 67% the faecal, liver, kidney, lung, heart, muscle, brain and blood samples from Norway rats, respectively. Rat norovirus was also identifiable in 5% (1/21) of laboratory rats and rat astrovirus in 40% (8/20) of faecal samples from laboratory mice. Co-infections were found in 28% (5/18) wild Norway rats. The highest RNA viral load of astrovirus (1.81 × 108 copy/g) and norovirus (3.49 × 107 copy/g) were measured in faecal samples; while the highest RNA viral load of hepevirus (1.16 × 109 copy/g) was found in liver samples of Norway rats, respectively. This study confirms the wide geographic distribution and high prevalence of astrovirus, norovirus and hepevirus among wild rats in Hungary with confirmation of different organ involvement of as well as the detection of norovirus and astrovirus in laboratory rats and mice, respectively. This finding further strengthens the role of rodents in the spread of viral pathogens especially infecting human.

Presence and Diversity of Different Enteric Viruses in Wild Norway Rats (Rattus norvegicus).

Rodents are common reservoirs for numerous zoonotic pathogens, but knowledge about diversity of pathogens in rodents is still limited. Here, we investigated the occurrence and genetic diversity of enteric viruses in 51 Norway rats collected in three different countries in Europe. RNA of at least one virus was detected in the intestine of 49 of 51 animals. Astrovirus RNA was detected in 46 animals, mostly of rat astroviruses. Human astrovirus (HAstV-8) RNA was detected in one, rotavirus group A (RVA) RNA was identified in eleven animals. One RVA RNA could be typed as rat G3 type. Rat hepatitis E virus (HEV) RNA was detected in five animals. Two entire genome sequences of ratHEV were determined. Human norovirus RNA was detected in four animals with the genotypes GI.P4-GI.4, GII.P33-GII.1, and GII.P21. In one animal, a replication competent coxsackievirus A20 strain was detected. Additionally, RNA of an enterovirus species A strain was detected in the same animal, albeit in a different tissue. The results show a high detection rate and diversity of enteric viruses in Norway rats in Europe and indicate their significance as vectors for zoonotic transmission of enteric viruses. The detailed role of Norway rats and transmission pathways of enteric viruses needs to be investigated in further studies.