Salmonella in fattening pigs in Reunion Island: herd prevalence and risk factors for infection.

Our objective was to identify the risk factors for Salmonella infection in fattening pigs in Reunion Island. Sixty pig farms were studied from April to August 2008 on the whole island. A questionnaire was submitted to the farmers, and samples of fresh faeces and gauze socks were taken to assess the Salmonella status of each herd. 40% of the herds tested positive for Salmonella spp. The most prevalent serovars were S. Typhimurium and S. Derby. The risk of Salmonella infection for the fattening pigs was increased when there was no disinfection at the farrowing stage (OR=5.2), when large numbers of cockroaches were present on the premises (OR=5.5) and when these facilities were not resistant to feral birds (OR=4.5). The risk for Salmonella infection of the herd was decreased when the number of visits from technical personnel was limited (<1 per month) (OR=0.38), when castration of piglets was done after 1 week of age (OR=0.38) and when the all-in all-out system was respected (OR=0.13).

Field efficacy and safety of an oral formulation of the novel combination anthelmintic, derquantel-abamectin, in sheep in New Zealand.

AIM: To evaluate the efficacy and safety of the novel anthelmintic combination, derquantel-abamectin, against gastrointestinal nematode populations in sheep, under field-use conditions. METHODS: Controlled faecal egg count reduction tests (FECRT) were conducted in New Zealand in 14 trials, covering a range of geographic locations, farming enterprises, breeds, nematode populations, and anthelmintic-resistance profiles. Enrolled animals were naturally infected with mixed populations of gastrointestinal nematodes. All trials included a group treated with derquantel-abamectin, and a negative control group. Nine trials included additional groups each treated with a single- or dual-active oral reference anthelmintic, selected from albendazole, levamisole, albendazole-levamisole, ivermectin, abamectin and moxidectin. A total of 838 animals were enrolled across all trials, and were randomly allocated to treatment groups within blocks defined by faecal nematode egg counts (FEC) pretreatment. On Day 0 derquantel-abamectin was administered orally at 1 ml/5 kg bodyweight (2 mg/kg derquantel, 0.2 mg/ kg abamectin), and each reference anthelmintic was given at the recommended label dose. Faecal samples were collected on Day 14 (+/- 1 day), to determine the percentage reduction in mean FEC for each anthelmintic tested. Larval differentiation was also performed post-treatment, to estimate efficacy at the genus level. Animals were weighed on or before Day 0, and on Day 14 (+/- 1 day) in 13 trials. RESULTS: The efficacy of derquantel-abamectin against mixed strongyle populations was > or =99.2%, based on the percentage reduction in geometric mean FEC. Nematodirus sp. was present in six trials at a level sufficient for efficacy calculations to be conducted; in all cases, the efficacy of derquantel-abamectin was 100%. In those trials where the efficacy of at least one reference anthelmintic was <95% against strongyles and/or Nematodirus sp., derquantel-abamectin was 100% effective. In five trials, the mean gain in bodyweight was significantly greater in the derquantel- abamectin group than the negative controls. CONCLUSIONS AND CLINICAL RELEVANCE: When administered orally at 1 ml/5 kg bodyweight, derquantel-abamectin is highly effective for the treatment of gastrointestinal nematodes in sheep, including populations of strongyles and Nematodirus sp. with resistance to one or more single- or dual-active anthelmintics. Derquantel-abamectin presents sheep producers with a unique opportunity to introduce a new class of anthelmintic to their nematode control programmes, with the added benefits offered by a combination anthelmintic.

Comparative evaluation of the immune status of congenitally athymic and euthymic rat strains bred and maintained at different institutes: 1. Euthymic rats.

We performed a comparative evaluation of the immune status, focused on the T-cell system, of euthymic rat strains in which the nude mutation had been introduced. From 10 institutes, we sampled 12 groups of euthymic rats at ages of 1 1/2-2 months and 1/2 year. We analyzed weight of body, spleen and thymus; antibody response and delayed-type hypersensitivity response to ovalbumin immunization; and (immuno)histopathology of spleen, lymph nodes, and lymphoid tissue along the gastrointestinal tract. In the spleen morphometric analysis was done of the periarteriolar lymphocyte sheath (using the antibody R73 recognizing the alpha beta-T-cell receptor) and of the red pulp (using the antibody ED2 recognizing red pulp macrophages). For almost all parameters tested, statistically significant differences between the groups (origin of the animals) were observed. A cluster analysis on the basis of body weight, spleen weight, and morphometric data of spleen did not yield clusters with a different composition among animals from individual groups. Based on the antibody response to ovalbumin, clustering revealed groups of "fast-and-high", "slow-and-low", and "intermediate" responders. The various groups differed in location within these clusters, i.e. the speed and extent of the immune response depends on the background euthymic strain. Considering the microbiological status assessed by serology, a variation was found both in post-infection state at entrance in the study, and in primo-infection associated with a rise in antibody concentrations during the study. These states showed no negative effect on anti-ovalbumin reactivity. Rather, the response in primo-infection to Rat Corona Virus, Sendai Virus, and Pneumonia Virus of Mice was the highest in animals clustered as "fast-and high" responders to ovalbumin.

Comparative evaluation of the immune status of congenitally athymic and euthymic rat strains bred and maintained at different institutes: 2. Athymic rats.

We performed a comparative evaluation of the immune status, focused on the T-cell system, in congenitally athymic rat strains. From 11 institutes around the world, we sampled 15 groups of animals at ages of 1 1/2-2 months and 1/2 year. The analysis included weight of body and spleen; antibody response and delayed-type hypersensitivity response after immunization with ovalbumin; and (immuno)histology of spleen, lymph nodes and lymphoid tissue along the gastrointestinal tract. Morphometric analysis was done for alpha beta-T-cell receptor-bearing cells in spleen tissue as a measure of the periarteriolar lymphocyte sheath; it was also done for splenic red pulp using the antibody ED2 recognizing red pulp macrophages. For almost all variables analyzed, statistically significant differences between the groups were observed. The extent of alpha beta-T-cell receptor-bearing cells in the spleen increased with age. The functioning of these cells in immunological responses can be questioned, because an immune response to ovalbumin was invariably absent. But secondary follicles with germinal centers, reflecting T-cell-dependent B-cell reactivity, were observed in lymph nodes and Peyer's patches (up to 40% and 75%, respectively, depending on the group), with a higher prevalence in older animals. A cluster analysis on the basis of body and spleen weight and composition of spleen compartments did not yield clusters with a different profile in regard to the animals' group of origin. The data presented are useful when comparing studies performed with various athymic rat strains at different institutes.