Intra-farm variation of rodent infestations on poultry farms of central Argentina

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.

Salmonella in broiler litter and properties of soil at farm location

Contamination of litter in a broiler grow-out house with Salmonella prior to placement of a new flock has been shown to be a precursor of the flock's Salmonella contamination further down the production continuum. In the southern USA, broiler grow-out houses are primarily built on dirt pad foundations that are placed directly on top of the native soil surface. Broiler litter is placed directly on the dirt pad. Multiple grow-out flocks are reared on a single litter batch, and the litter is kept in the houses during downtime between flocks. The effects of environmental determinants on conditions in broiler litter, hence Salmonella ecology within it, has received limited attention. In a field study that included broiler farms in the states of Alabama, Mississippi and Texas we assessed Salmonella in broiler litter at the end of downtime between flocks, i.e. at the time of placement of a new flock for rearing. Here we utilized these results and the U.S. General Soil Map (STATSGO) data to test if properties of soil at farm location impacted the probability of Salmonella detection in the litter. The significance of soil properties as risk factors was tested in multilevel regression models after accounting for possible confounding differences among the farms, the participating broiler complexes and companies, and the farms' geographical positioning. Significant associations were observed between infiltration and drainage capabilities of soil at farm location and probability of Salmonella detection in the litter.