Effect of a disinfection strategy on the methicillin‐resistant Staphylococcus aureus CC398 prevalence of sows,their piglets and the barn environment

Aims

To assess, in a cleaned and disinfected barn environment, the efficacy of an animal disinfection strategy to reduce the livestock‐associated methicillin‐resistant Staphylococcus aureus (LA‐MRSA) prevalence in sows, their offspring and the barn environment.

Methods and Results

On each farm, six sow rounds were sampled; sows were divided into either a test or control group. Per round, 20 sows and 40 of their piglets were sampled at different time points together with the barn environment. The disinfection strategy of the test groups consisted of washing the sows with a shampoo followed by disinfection of the skin with a solution containing chlorhexidine digluconate and isopropanol. On the first day of disinfection and 6 days after stopping the disinfection, a significant decrease (P < 0·01) of on average 68 and 66% in sow MRSA prevalence was observed on both farms, whereas no decrease was seen in the control groups. Just before weaning, 21–28 days after the end of the disinfection strategy, the difference in MRSA prevalence between both groups was reduced to 4% and no longer significant (P = 0·20). The MRSA prevalence of the piglets in the test groups was significantly lower (26%; P < 0·01) 6 days after the end of disinfection. Just before weaning, this difference was reduced to 5% but still significant (P < 0·01). In the swine nursery unit, no significant difference (P = 0·99) was seen between both groups. Based on semi‐quantitative counts, a relationship (r² > 0·6; P < 0·01) was seen between MRSA contamination in the barn environment and the MRSA prevalence in pigs.

Conclusion

Results show that the tested disinfection strategy reduces temporarily the sow and piglet MRSA status, but does not result in a final reduction in MRSA at weaning or in the nursery unit.

Significance and Impact of the Study

First report on the efficacy of an animal disinfection strategy to reduce LA‐MRSA prevalence in sows, their offspring and the barn environment.     

Sexually dimorphic swallows have higher extinction risk

The effect of sexual selection on extinction risk remains unclear. In theory, sexual selection can lead to both increase and decrease extinction probability depending on the ecology of the study system. Thus, combining different groups might obscure patterns that can be found in groups that share similar ecological features. Using phylogenetic comparative analysis, we studied sexual plumage dimorphism in relation to the perceived risk of extinction in hirundines (subfamily: Hirundininae), in which all species are socially monogamous aerial foragers. Among the 72 species studied, five species are facing a perceived threat of extinction. Species with sexually dimorphic plumage had a higher risk of extinction than did species with sexually monomorphic plumage. Likewise, when focusing solely on tail ornamentation, species that exhibit a sexual dimorphism in tail length had a higher risk of extinction than did other species. In Hirundininae, which are affected a great deal by severe weather, sexual selection and the resultant sexual dimorphism would increase extinction risk.     

Arrival date and microorganisms in barn swallows

Migration between breeding sites and winter quarters constitute a major life history strategy in birds. The benefits of such migrations must at least equal the costs for such behavior to evolve and be maintained. We tested whether there was a relationship between abundance and diversity of microorganisms on nest lining feathers and timing of arrival by barn swallows Hirundo rustica. Nest lining feathers are chosen and transported by adult barn swallows to their nests just before and during egg laying, at a time when barn swallows have arrived weeks earlier, implying that any heterogeneity in abundance and diversity of microorganisms on feathers in nests must arise from feather preferences. There was a negative relationship between arrival date and the total number of fledglings showing that early arrival is advantageous. The arrival date of adult barn swallows was significantly positively correlated with the abundance of specific bacteria (Bacillus licheniformis) and positively correlated with the abundance of the fungus Trichoderma reesei and negatively correlated with the abundance of the fungus Mucor circinelloides. Moreover, we found a significant positive relationship between arrival date and mean total number of bacterial colonies in TSA medium. There was a significant negative relationship between arrival date and mean total number of bacterial colonies in FMA medium, and Simpson's diversity index of the abundance of bacteria in FMA medium. Such heterogeneity may arise from some microorganisms being beneficial, others detrimental and yet others benign and of no significant importance. In contrast, there was no significant relationship between arrival date and age of individuals. These findings are consistent with the hypothesis that early arriving barn swallows differ in abundance and diversity of microorganisms from late arriving conspecifics, and that they choose feathers for their nests that differ in terms of microorganisms from those chosen by late arrival individuals.     

Quantitative genetics of plumage color: lifetime effects of early nest environment on a colorful sexual signal

Phenotypic differences among individuals are often linked to differential survival and mating success. Quantifying the relative influence of genetic and environmental variation on phenotype allows evolutionary biologists to make predictions about the potential for a given trait to respond to selection and various aspects of environmental variation. In particular, the environment individuals experience during early development can have lasting effects on phenotype later in life. Here, we used a natural full‐sib/half‐sib design as well as within‐individual longitudinal analyses to examine genetic and various environmental influences on plumage color. We find that variation in melanin‐based plumage color – a trait known to influence mating success in adult North American barn swallows (Hirundo rustica erythrogaster) – is influenced by both genetics and aspects of the developmental environment, including variation due to the maternal phenotype and the nest environment. Within individuals, nestling color is predictive of adult color. Accordingly, these early environmental influences are relevant to the sexually selected plumage color variation in adults. Early environmental conditions appear to have important lifelong implications for individual reproductive performance through sexual signal development in barn swallows. Our results indicate that feather color variation conveys information about developmental conditions and maternal care alleles to potential mates in North American barn swallows. Melanin‐based colors are used for sexual signaling in many organisms, and our study suggests that these signals may be more sensitive to environmental variation than previously thought.     

Sexual selection in the monogamous barn swallow (Hirundo rustica). II. Mechanisms of sexual selection

Mechanisms of sexual selection in the monogamous, sexually dimorphic barn swallow (Hirundo rustica) were studied during a seven-year period. First, the sex ratio of reproducing adults was male-biased, and mated males had significantly longer tail ornaments than unmated males. Secondly, some of the unmated individuals later committed infanticide and became mated with the mother of the killed brood. Fathers of killed broods had significantly shorter tails than other males, and there was a tendency for infanticidal males to have longer tail ornaments than other unmated males. Thirdly, long-tailed male barn swallows were more successful in acquiring extra-pair copulations than other males, and females involved in extra-pair copulations, as compared to females not involved in such copulations, had mates with shorter tail ornaments. Fourthly, male barn swallows having long tails as compared to short-tailed males acquired mates in better body condition. Females mated to long-tailed males reproduced earlier, laid more eggs and were more likely to have two clutches than were females mated to short-tailed males. Finally, females mated to long-tailed males put more effort into reproduction than did other females, as evidenced by their relatively larger contribution to feeding of offspring. Thus, at least five different components of sexual selection affected male reproductive success. Selection arising from differential success during extra-pair copulations, differential reproductive success and differential male reproductive effort thus accounted for most of the selection on tail ornaments in male barn swallows.     

Male barn swallows use different resource allocation rules to produce ornamental tail feathers

Sexual ornaments compete for resources with other functionaltraits. Such resource allocation trade-offs should ensure thehonesty of sexual ornaments according to the Zahavi's handicapprinciple. However, the existence of costly signals could notbe enough to guarantee honesty if different individuals investdifferent proportions of their limited resources in ornaments.Then, a certain level of sexual signaling would correspond toseveral levels of individual condition. Here, we explore whetherthere are different resource allocation rules in tail featherornaments between males within a barn swallow (Hirundo rustica)population and whether these different rules confer differentviability to males. We assessed the proportion of resourcesinvested in ornamental feathers compared with other functionalfeathers moulted and growing during the same period at expensesof the same resources. We found that 1) different males allocatea different proportion of resources to ornamental feathers inrelation to functional feathers and this proportion is repeatablebetween years and 2) male survival likelihood decreased as theproportion of resources allocated to ornamental feathers increased.Survival costs associated with increased investments in ornamentscan maintain the sexual signaling system honest at populationlevel but do not preclude the existence of an array of differentallocation rules between males. Thus, males with different viabilitycan produce ornamental feathers of the same length. These resultsshow that the relationship between male viability and ornamentexpression can be less straightforward than considered previously.     

First record of greater white‐toothed shrew Crocidura russula in Ireland

• 1 Skeletal remains of greater white‐toothed shrew Crocidura russula were recovered from barn owl Tyto alba and kestrel Falco tinnunculus pellets collected at 15 locations in Counties Tipperary and Limerick in Ireland in September 2007 and March 2008. Seven greater white‐toothed shrews were trapped at four locations in Tipperary in March 2008. This is the first Irish record of C. russula and compelling evidence that the species is established in Ireland.
• 2 The absence of C. russula from earlier surveys of owl pellets and small mammals in Ireland suggests a recent introduction by uncertain means, possibly since 2001. It seems likely that C. russula will expand its range in Ireland. Its impact on the ecology of habitats in which it is found is uncertain but may be considerable.

     

Structural coloration and sexual selection in the barn swallow Hirundo rustica

Structural coloration has been hypothesized to play a role insexual selection, and we tested whether this was the case ina field study of the barn swallow Hirundo rustica. The dorsaliridescent plumage of barn swallows has a strong reflectancein the ultraviolet (UV) region, with adult males on averagereflecting 8-9% more than adult females, as revealed by a 2-yearstudy in southwestern Spain. The correlation between structural coloration (described by the reflectance in the UV part of thespectrum, UV chroma and blue chroma) and three other secondarysexual characters significantly associated with male matingsuccess (tail length, tail asymmetry, and red facial coloration)was weak and generally nonsignificant. Nor was there a significantrelationship between color parameters and body condition. Wetested for an association between structural coloration of the dorsal plumage and sexual selection in a number of independenttests. Arrival date of males was not significantly relatedto color; there was no significant relationship between colorationand probability of survival or age; mated males did not havestronger reflectance than unmated males; and the duration ofthe premating period was not significantly related to color.Reproductive success was not significantly correlated withplumage coloration in males, nor was the feeding rate of offspringby brightly colored males higher than that of males with lessbright plumage. Given that sample sizes were large, and the power of statistical tests high, we conclude that current sexualselection on the coloration of the dorsal plumage in the barnswallow is, at best, weak.     

Precognitive and cognitive elements in sound localization

Sound localization behavior is of great importance for an animal's survival. To localize a sound, animals have to detect a sound source and assign a location to it. In this review we discuss recent results on the underlying mechanisms and on modulatory influences in the barn owl, an auditory specialist with very well developed capabilities to localize sound. Information processing in the barn owl auditory pathway underlying the computations of detection and localization is well understood. This analysis of the sensory information primarily determines the following orienting behavior towards the sound source. However, orienting behavior may be modulated by cognitive (top-down) influences such as attention. We show how advanced stimulation techniques can be used to determine the importance of different cues for sound localization in quasi-realistic stimulation situations, how attentional influences can improve the response to behaviorally relevant stimuli, and how attention can modulate related neural responses. Taken together, these data indicate how sound localization might function in the usually complex natural environment.     

Begging in the absence of parents by nestling tree swallows

Begging by nestling passerine birds has become a model systemfor studies in animal communication. Although most beggingoccurs when parents arrive at the nest to feed (here called"primary begging"), it also occurs between feeding visits andimmediately after parents leave the nest. Begging in thesecontexts (here called "secondary begging") may have relativelylittle influence on the probability of receiving food, but could increase the overall cost of the signal and thus influence nestlingbegging strategies. The purpose of our study was to determinehow often tree swallow (Tachycineta bicolor) nestlings begin contexts other than to parents with food and to examinewhat factors influence the frequency of this begging. Secondarybegging ranged from 7% of measured begging responses at day2 to 30% by day 8 and was more frequent when the interval betweenparental feeding visits was relatively long and when the timeto respond to the arrival of parents with food was short. Increasesin both age and intervisit interval were associated with decreasesin nestling response times, suggesting that secondary beggingmay be related to the speed with which nestlings respond to stimuli. We discuss possible functions of secondary beggingand raise the possibility that it may, in fact, be an error.