Spatial and temporal patterns of brown rat (Rattus norvegicus) abundance variation in poultry farms

Role of Mus musculus in the transmission of several pathogens in poultry farms

This study aimed to analyze the role of Mus musculus as a host of Leptospira spp., lymphocytic choriomeningitis virus (LCMV) and Toxoplasma gondii, in poultry farms of Buenos Aires province, Argentina, and to assess the potential risk of transmission to humans and domestic or breeding animals. Samplings were performed between 2009 and 2011 (S1) and during 2016 (S2). In S1, we studied the prevalence of infection for Leptospira spp. and LCMV, whereas, in S2, we studied the prevalence of infection for Leptospira spp. and T. gondii. In S1, we found an overall Leptospira spp. prevalence in M. musculus of 18% (14/79) and no positive serum samples for LCMV (0/166). In S2, we detected no positive individuals for Leptospira spp. (0/56) and an overall T. gondii seroprevalence of 3.6% (2/56). The probability of Leptospira spp. infection in M. musculus was higher in reproductively active individuals and in samplings subsequent to months with high accumulated precipitation. Our results suggest that, in the poultry farms studied, the presence of M. musculus may be a risk factor in the transmission of Leptospira spp. and T. gondii to humans and domestic animals. The management of farms should include biosecurity measures for farm workers and more effective rodent control.

Small-mammal assemblages in piggeries in a developing country: relationships with management practices and habitat complexity

Abstract ContextPig production is increasing in developing countries and is increasing the coexistence of different production systems regarding management practices. Small mammals can cause major economic and sanitary problems on pig farms. The interactions among small mammals, production practices and habitat complexity have been sparsely studied. AimsThe aim was to compare small-mammal assemblages on extensive and intensive pig-production systems, and to analyse the relationship with environmental characteristics and management practices. MethodsSeasonal live-trapping of small mammals within 18 farms (under intensive or extensive management) was performed in central Argentina, simultaneously with a survey of environmental and management practices. Multiple regression analyses were performed to assess the relation between infestation levels and environmental characteristics. Key results In total, 472 small mammals were captured, including the exotic murids Rattus norvegicus, R. rattus and Mus musculus, three native sigmodontines, namely, Akodon azarae, Oligoryzomys flavescens and Oxymycterus rufus, and two native marsupials, namely, Didelphis albiventris and Lutreolina crassicaudata. The location of waste deposits, the density of cats, the frequency of rodent control and the way pig food was stored influenced wild small-mammal abundance; exotic rodent species were lower when the density of cats increased. Rattus norvegicus was more abundant where rodent control was not frequent or null, contrary to M. musculus. Both species were more abundant in food and pig sheds, whereas native species were associated with vegetated areas outside of sheds. Also, A. azarae was associated with the density of pigs. Didelphis albiventris was more abundant on extensive farms, whereas L. crassicaudata was captured on intensive farms. Conclusions Small-mammal abundance did not respond to the type of production system per se, but exotic species abundance was influenced by management decisions. The most important human behaviours related to exotic rodent infestation were the possession of cats, the frequency of rodent control and the way waste and pig feed were managed. Implications Our findings highlighted the need for integrated studies on factors influencing the dynamics of rodent populations in commercial piggery systems, for the development of effective pest management. Management recommendations need to assess environmental complexity and human behaviour as important moderators of the population dynamics of small mammal species in and around piggeries.

Small rodent species on pig and dairy farms: habitat selection and distribution

BACKGROUND

Rodent species are common in livestock production systems, and some of them are considered serious pests because of the sanitary problems and economic losses they cause. Information about microhabitat selection by rodent species in livestock production systems is necessary for understanding rodent requirements and to contribute to effective prevention and development of control measures for pest rodent species. In this work we study microhabitat selection by rodent species that inhabit pig and dairy farms in central Argentina. Rodent trapping was conducted over three years (2008-2011) on 18 livestock farms, each one sampled seasonally during one year. To study habitat selection, microhabitat characterizations were performed describing 22 environmental variables in captured sites and random trap sites without captures.

RESULTS

With a trapping effort of 7333 Sherman and 7026 cage live trap-nights, 444 rodents of seven species were captured (including the murine pest species Rattus norvegicus, R. rattus and Mus musculus and four native species). The three murines selected characteristics related to building structure and/or to food sources availability/proximity, while Akodon azarae selected sites with tall herbatious vegetation.

CONCLUSIONS

We identified microhabitat characteristics that explain habitat distribution of small rodent species in these complex farm systems. This study contributes to broaden the integrated pest management of rodent pest species and could also contribute to the reduction of the use of rodenticides in these systems. © 2018 Society of Chemical Industry.

Evaluation of habitat requirements of small rodents and effectiveness of an ecologically-based management in a hantavirus-endemic natural protected area in Argentina

Hantavirus pulmonary syndrome is a severe cardio pulmonary disease transmitted to humans by sylvan rodents found in natural and rural environments. Disease transmission is closely linked to the ecology of animal reservoirs and abiotic factors such as habitat characteristics, season or climatic conditions. The main goals of this research were: to determine the biotic and abiotic factors affecting richness and abundance of rodent species at different spatial scales, to evaluate different methodologies for studying population of small rodents, and to describe and analyze an ecologically-based rodent management experience in a highly touristic area. A 4-year study of small rodent ecology was conducted between April 2007 and August 2011 in the most relevant habitats of El Palmar National Park, Argentina. Management involved a wide range of control and prevention measures, including poisoning, culling and habitat modification. A total of 172 individuals of 5 species were captured with a trapping effort of 13 860 traps-nights (1.24 individuals/100 traps-nights). Five rodent species were captured, including 2 hantavirus-host species, Oligoryzomys nigripes and Akodon azarae. Oligoryzomys nigripes, host of a hantavirus that is pathogenic in humans, was the most abundant species and the only one found in all the studied habitats. Our results are inconsistent with the dilution effect hypothesis. The present study demonstrates that sylvan rodent species, including the hantavirus-host species, have distinct local habitat selection and temporal variation patterns in abundance, which may influence the risk of human exposure to hantavirus and may have practical implications for disease transmission as well as for reservoir management.

Where do Norway rats live? Movement patterns and habitat selection in livestock farms in Argentina

Context The Norway rat (Rattus norvegicus) is recognised as one of the most harmful invasive mammal species in natural, urban and rural environments worldwide. Prevention and control of pest species in livestock farms is necessary to protect animal and human health, but control practices usually do not take into account the biology and ecology of the species to be controlled. The understanding of the biological requirements of Norway rats is necessary for the implementation of efficient management actions. Aims The aim of this research was to study movement patterns and habitat selection of Norway rats on livestock farms in central Argentina. We hypothesised that rats select specific areas within the farms according to the farm’s structure and to the availability of resources. Methods We conducted live-trapping of rats in a pig farm and a dairy farm, during each of four seasons over 1 year. Traps were active for three consecutive days at each trapping session. Movements and habitat selection were assessed by spool-and-line technique combined with environmental surveys and GIS tools. Key results We captured a total of 133 Norway rats and evaluated the movements of 47 individuals. The mean length travelled, registered for one night, was 84.28 ± 38.21 m. They did not travel great linear distances within the farms, but instead performed tortuous trajectories around specific sites. Norway rats selected sites containing food, water and refuges; and avoided travelling across areas with short vegetation. Sites containing food sources were most preferred. Conclusions Because food sources for rats were present ad libitum in farms, our findings strongly support the idea that management strategies of prevention and control of this species must include adequate rodent-proof food storage. Also, because rats are found close to livestock, improvement in preventing rats’ access to animal sheds is necessary to prevent contamination of livestock feeders with pathogens carried by rats. Implications The present study provides novel information about the ecology of Norway rats on livestock farms. We encourage farmers to follow our recommendations in order to improve rodent-control strategies.

Are life-history strategies of Norway rats (Rattus norvegicus) and house mice (Mus musculus) dependent on environmental characteristics?

Context Life-history theory attempts to explain the way in which an organism is adapted to its environment as well as explaining the differences in life-history strategies among and within species. Aims The aim of this paper was to compare life-history traits of the Norway rat and the house mouse living in different habitats and geographic regions so as to find patterns related to environmental characteristics on the basis of published ecological studies conducted before 2011. Methods The environments where rodent populations lived were characterised according to climate type, occurrence of freezing temperatures and frost, degree of anthropisation and trapping location. Four demographic characteristics were analysed. A canonical correspondence analysis was performed to explain the effects of environmental variables on the demographic characteristics of rodents. Information was gathered from 35 articles published between 1945 and 2010. Key results Most populations of both species showed differences in abundance throughout the year, but no defined pattern was common among populations. The pregnancy rate of Norway rat was highest during spring and autumn in urban environments, during spring and winter in rural environments and during summer in sylvan habitats. House mouse populations were most frequently reported to experience high pregnancy rates during summer. Contrary to urban and rural populations, in sylvan environments the occurrence of a reproductive break was the most commonly reported pattern for both species. Litter size of Norway rat depended on the degree of anthropisation and the occurrence of freezing temperatures and frost. Litter size was greater in rural environments and in areas without freezing temperatures and frost. House mouse did not show differences in litter size resulting from any of the environmental characteristics analysed. Conclusions Both species are able to modify their reproductive strategies according to environmental characteristics, especially according to the degree of anthropisation of the environment. In sylvan areas, where animals are more exposed to seasonal changes in weather conditions, changes in reproductive investment are more evident. Implications Regarding the implications for rodent control, the best time to apply control measures could be winter in sylvan and urban environments. In rural environments, the best time for conducting control efforts is less clear, although cold seasons seem also to be the best.