Stress significantly increases mortality following a secondary bacterial respiratory infection

A variety of mechanisms contribute to the viral-bacterial synergy which results in fatal secondary bacterial respiratory infections. Epidemiological investigations have implicated physical and psychological stressors as factors contributing to the incidence and severity of respiratory infections and psychological stress alters host responses to experimental viral respiratory infections. The effect of stress on secondary bacterial respiratory infections has not, however, been investigated. A natural model of secondary bacterial respiratory infection in naive calves was used to determine if weaning and maternal separation (WMS) significantly altered mortality when compared to calves pre-adapted (PA) to this psychological stressor. Following weaning, calves were challenged with Mannheimia haemolytica four days after a primary bovine herpesvirus-1 (BHV-1) respiratory infection. Mortality doubled in WMS calves when compared to calves pre-adapted to weaning for two weeks prior to the viral respiratory infection. Similar results were observed in two independent experiments and fatal viral-bacterial synergy did not extend beyond the time of viral shedding. Virus shedding did not differ significantly between treatment groups but innate immune responses during viral infection, including IFN-γ secretion, the acute-phase inflammatory response, CD14 expression, and LPS-induced TNFα production, were significantly greater in WMS versus PA calves. These observations demonstrate that weaning and maternal separation at the time of a primary BHV-1 respiratory infection increased innate immune responses that correlated significantly with mortality following a secondary bacterial respiratory infection

Factors influencing aggression in newly mixed pigs

996 pigs were used to understand the effects of aggression on growth in swine, the role of previous experience on the level of aggression, and the basis on which a pig accesses recognition and familiarity when mixed with an unfamiliar pig. The hypothesis that fighting in newly mixed pigs is proximately triggered by an innate response to fight unfamiliar pigs as opposed to an alternative hypothesis that fighting is triggered by unknown dominance status was also addressed. Growth over a 2 week period was negatively effected when mixing near market weight pigs (average wt. 85.1 kg). Time spent eating, lying and standing were similar across all treatment groups by day 8 (P $>$.05), however time spent fighting for Mixed pigs continued to be higher than other treatments (P $>$.01). In a trial using 6 and 10 week old pigs, time spent fighting (TF), total number of fights and the winner loser of an encounter among unfamiliar dyads in a neutral pen during a 2 h period was not influenced by their previous dominance ranks (P $<$.10). Six week old pigs differed from 10 week pigs in TF (raw means 758 and 421 sec/2 h period respectively; P $<$.01). TF was positively correlated with the difference in weight between the paired pigs (maximum difference 6.2 kg; P $<$.05). Newly mixed pigs access strangeness based on familiarity gained through previous association as opposed to recognition based on phenotypic kin recognition. Pigs fought more if reared apart than separately (252 \sp{\rm \ a} 33 sec vs 67 \sp{\rm \ a} 45 sec respectively; P $<$.0001), but time spent fighting was not different between related or unrelated dyads. An attempt to exchange familiarity (FX) between two unfamiliar pigs prior to mixing was unsuccessful in eliminating aggression during a 2 h mixing period. FX pigs were pre-exposed to each other while one of the pair was under the influence of anesthesia. FX pigs were no different from Negative Control pigs (NC) or Sham Controls (SC) in time spent investigating each other or for any of the fighting parameters measured. FX pigs may have gained some familiarity during pre-exposure periods since they had a higher frequency of mounting during the 2 h mixing period then the NC and SC pigs (P $<$.01). (Abstract shortened with permission of author.)U of I OnlyETDs are only available to UIUC Users without author permissio

Infectious Disease and Grouping Patterns in Mule Deer

<div><p>Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (<i>Odocoileus hemionus hemionus</i>) from a chronic wasting disease (CWD) endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008–2013), we built a generalized linear mixed model (GLMM) to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes) to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics.</p></div

Stress significantly increases mortality following a secondary bacterial respiratory infection

Abstract A variety of mechanisms contribute to the viral-bacterial synergy which results in fatal secondary bacterial respiratory infections. Epidemiological investigations have implicated physical and psychological stressors as factors contributing to the incidence and severity of respiratory infections and psychological stress alters host responses to experimental viral respiratory infections. The effect of stress on secondary bacterial respiratory infections has not, however, been investigated. A natural model of secondary bacterial respiratory infection in naive calves was used to determine if weaning and maternal separation (WMS) significantly altered mortality when compared to calves pre-adapted (PA) to this psychological stressor. Following weaning, calves were challenged with Mannheimia haemolytica four days after a primary bovine herpesvirus-1 (BHV-1) respiratory infection. Mortality doubled in WMS calves when compared to calves pre-adapted to weaning for two weeks prior to the viral respiratory infection. Similar results were observed in two independent experiments and fatal viral-bacterial synergy did not extend beyond the time of viral shedding. Virus shedding did not differ significantly between treatment groups but innate immune responses during viral infection, including IFN-γ secretion, the acute-phase inflammatory response, CD14 expression, and LPS-induced TNFα production, were significantly greater in WMS versus PA calves. These observations demonstrate that weaning and maternal separation at the time of a primary BHV-1 respiratory infection increased innate immune responses that correlated significantly with mortality following a secondary bacterial respiratory infection.</p

Annual numbers of newly captured (and recaptured) mule deer in Antelope Creek by age and sex class.

<p>Annual numbers of newly captured (and recaptured) mule deer in Antelope Creek by age and sex class.</p