Michel Bigras-Poulin

Projected effects of climate change on tick phenology and fitness of pathogens transmitted by the North American tick Ixodes scapularis.

Ixodes scapularis is the principal tick vector of the Lyme borreliosis agent Borrelia burgdorferi and other tick-borne zoonoses in northeastern North America. The degree of seasonal synchrony of nymphal and larval ticks may be important in influencing the basic reproductive number of the pathogens transmitted by I. scapularis. Because the seasonal phenology of tick vectors is partly controlled by ambient temperature, climate and climate change could shape the population biology of tick-borne pathogens. We used projected monthly normal temperatures, obtained from the second version of the Canadian Coupled Global Climate Model (CGCM2) under emissions scenario A2 of the Intergovernmental Panel on Climate Change for a site in southern Ontario, Canada, to simulate the phenology of I. scapularis in a mathematical model. The simulated seasonal abundance of ticks then determined transmission of three candidate pathogens amongst a population of white-footed mice (Peromyscus leucopus) using a susceptible-infected-recovered (SIR) model. Fitness of the different pathogens, in terms of resilience to changes in tick and rodent mortality, minima for infection duration, transmission efficiency and particularly any additional mortality of rodents specifically associated with infection, varied according to the seasonal pattern of immature tick activity, which was different under the temperature conditions projected for the 2020s, 2050s and 2080s. In each case, pathogens that were long-lived, highly transmissible and had little impact on rodent mortality rates were the fittest. However, under the seasonal tick activity patterns projected for the 2020s and 2050s, the fitness of pathogens that are shorter-lived, less efficiently transmitted, and more pathogenic to their natural hosts, increased. Therefore, climate change may affect the frequency and distribution of I. scapularis-borne pathogens and alter their evolutionary trajectories.

FACTORS AFFECTING MILK UREA NITROGEN AND PROTEIN CONCENTRATIONS IN QUEBEC DAIRY COWS

Milk urea nitrogen (MUN), together with percentage milk protein (PROT), are increasingly used as indicators of the protein-energy balance and for monitoring nutrition and diagnosing feeding disorders. The goal of this study was to analyze the effects of parity, milk yield, days in lactation, somatic-cell count, and herd and feeding factors on MUN and PROT. In 10 dairy herds, one milk sample was taken from each of 418 cows, within +/- 2 days of the routine milk-test visit. We used a four-step multiple linear-regression model with backward elimination, including interactions between herd and the different factors. For both dependent variables, there were significant interactions with herd. Herd-specific models were markedly different; however, the daily amount of protein concentrates fed remained (and had a positive coefficient) in seven of 10 herd models for MUN. This factor is easy to record under field conditions and has to be considered in the evaluation of the ration by means of MUN and PROT. Overfeeding of rumen soluble protein can be easily diagnosed and corrected using MUN analyses. The relationships between MUN and PROT in respect of the factors parity, daily milk yield, and days postpartum also vary considerably among herds.

Body condition evaluation in sows

In the porcine species the ‘thin sow syndrome’, the ‘fat sow syndrome’ and the ‘second parity syndrome’ have been related to problems with the regulation and dynamics of body condition. There is, therefore, a need to adequately monitor body condition. In a first study, a new body condition monitoring technique was developed. Several body measurements of sows were related, by multiple regression, to an indirect representation of body composition based on principal components derived from live weight and backfat measurements. In a second study, the reliability of this new technique was also determined and compared to that of a more traditional scoring system based on visual appraisal and palpation. Five observers independently evaluated thirty sows three times using the two techniques. Both techniques were found to be similarly repeatable. The new technique, however, was found to have higher reproducibility. It is concluded that body condition is better represented by the use of principal components and that they can be predicted from body morphology under field conditions.

Characterization of Serpulina hyodysenteriae isolates of serotypes 8 and 9 by random amplification of polymorphic DNA analysis.

A PCR-based DNA fingerprinting method termed RAPD (Random Amplification of Polymorphic DNA), or AP-PCR (for Arbitrary Primed PCR) was used to detect sequence diversity among reference strains and isolates of Serpulina hyodysenteriae. RAPD fingerprinting of 20 S. hyodysenteriae isolates of serotypes 8 or 9 from Quebec was generated with 2 different 10-base primers used independently. Reference strains and field isolates belonging to serotypes 8 or 9 revealed polymorphisms in RAPD fingerprints with both primers. Interspecies polymorphisms were observed by RAPD analysis of S. hyodysenteriae representing serotypes 1 to 9, S.innocens, and 5 other weakly beta-hemolytic intestinal spirochetes. A dendrogram based on the analysis of RAPD profiles of the strains tested with one of the primers (#17), permitted the clustering of these strains into 11 divisions. The predominance of particular RAPD profiles among S. hyodysenteriae isolates isolated from cases of swine dysentery in different herds suggested that certain S. hyodysenteriae types could be epidemiologically important. Our results indicate that RAPD could be used as a typing method for S. hyodysenteriae and as an epidemiological method for identifying spirochetes isolated from swine.

Spatio-temporal variations and age effect on Toxoplasma gondii seroprevalence in seals from the Canadian Arctic

Toxoplasmosis is a significant public health threat for Inuit in the Canadian Arctic. This study aimed to investigate arctic seals as a possible food-borne source of infection. Blood samples collected from 828 seals in 7 Canadian Arctic communities from 1999 to 2006 were tested for Toxoplasma gondii antibodies using a direct agglutination test. Polymerase chain reaction (PCR) was used to detect T. gondii DNA in tissues of a subsample of seals. Associations between seal age, sex, species, diet, community and year of capture, and serological test results were investigated by logistic regression. Overall seroprevalence was 10·4% (86/828). All tissues tested were negative by PCR. In ringed seals, seroprevalence was significantly higher in juveniles than in adults (odds ratio=2·44). Overall, seroprevalence varied amongst communities (P=0·0119) and by capture year (P=0·0001). Our study supports the hypothesis that consumption of raw seal meat is a significant source of infection for Inuit. This work raises many questions about the mechanism of transfer of this terrestrial parasite to the marine environment, the preponderance of infection in younger animals and the natural course of infection in seals. Further studies to address these questions are essential to fully understand the health risks for Inuit communities.

Influence of management, housing and personality of the stockperson on preweaning performances on independent and integrated swine farms in Québec

Abstract A cross-sectional study was implemented to determine which factors related to management, housing and stockperson in the farrowing quarters were associated with preweaning mortality and piglets weaned per litter in swine breeding herds. The associations were sought separately for the two most common types of swine production in Quebec. Forty-eight randomly-selected independent farms and 38 others belonging to integrated organizations specialized in swine production conveniently chosen among the largest organizations in Quebec participated in the study. Preweaning performances were computed from the sow records. Information on housing features was gathered during the visit to the farrowing quarters. Management practices were obtained through a questionnaire from the stockperson working in the farrowing quarters and his or her personality traits were evaluated through a personality test. Backward elimination procedure was used to build multiple linear regression models for each measure of performance for each type of farm. The procedures started from the management, housing and stockperson groups of variables taken separately and altogether, leading to the building of different regression models. Piglets weaned per litter averaged 8.9 and 8.6 on the independent and integrated farms, respectively and preweaning mortality, 14.4 and 15.4%, respectively. On the independent farms, high preweaning performances (high number of piglets weaned per litter and low preweaning mortality) were associated with routinely washing the farrowing crates, vaccination of the sows against neonatal diarrhea, farrowing crates equipped with high bottom bars, partially-slotted floors in the farrowing pens and high self-discipline from the stockperson. Poor performances were associated with the use of oxytocin around farrowing, mixed nursery-farrowing quarters and a stockperson being exaggeratedly self-assured and sensitive. On the integrated farms, the use of oxytocin at farrowing was also associated with poor performances, as well as several rooms or all-in/all-out farrowing quarters, farrowing crates equipped with high or medium bottom bars, totally-slotted floors and a stockperson being rather bold, suspecting and tense. High performances were positively associated with warmth, emotional stability and self-discipline from the stockperson. These findings provided evidences of the influence of the stockpersons personality on performances in particular, on the integrated farms on which the management in the farrowing quarters was more proactive (implying a stronger relationship between the stockperson and the pigs). In contrast, the importance to preweaning performances of general hygiene and health control was emphasized on the independent farms.

Description of cow-calf productivity in Northwestern Quebec and path models for calf mortality and growth

Abstract A random sample of 651 assumed-pregnant cows was drawn from 26 randomly selected beef herds in Northwestern Quebec, Canada. The cows were followed with their calves (n = 568) for one production period. Data were collected on calving conditions, calf mortalities, and the presence of diarrhea and pneumonia in calves during the first 2 weeks of life. The calves were weighed and measured for withers height, at 3–4 weeks of age and at the weaning (median of 203 days of age). Cow-calf productivity was described and two path models were built, one for calf mortalities and the other for calf growth. The percentage of weaned calves was 78.8%, the risk of perinatal mortality, within 24 h of birth, 4.4%, and the risk of neonatal mortality, from 24 h to 30 days of age, 7.7%, were estimated. The mean 200 day weight (adjusted for sire breed) was 217 kg for female calves and 232 kg for male calves. Birth with assistance and birth between December and March (versus in April or May) were associated with an increased risk of dying during the perinatal period; birth in a maternity pen was associated with a decreased risk of perinatal mortality. The presence of diarrhea or pneumonia during the first 2 weeks of life was associated with an increased risk of dying between 24 h and 30 days of age and with a decreased achieved growth at 30 days without a subsequent full compensatory gain at the weaning.

Risk factors associated with West Nile virus mortality in American Crow populations in Southern Quebec.

Soon after the appearance of West Nile virus (WNV) in North America, a number of public health authorities designated the American Crow (Corvus brachyrhynchos) a sentinel for WNV detection. Although preliminary studies have suggested a positive association between American Crow mortality and increased risk of WNV infection in humans, we still know little about dynamic variation in American Crow mortality, both baseline levels and mortality associated with WNV. We hypothesized that the complex social behavior of American Crows, which is shaped by age and seasonal factors, influences both baseline mortality and WNV mortality in American Crow populations. We examined American Crow mortality data from Quebec for the 2005 WNV surveillance year, which lasted from 5 June to 17 September 2005. The variables of interest were age, gender, body condition index, time of year, and land cover. We used a log-linear model to examine baseline mortality. Logistic regression and general linear regression models were constructed to examine variables associated with mortality due to WNV. We found that both age and time of year were key variables in explaining baseline mortality. These two variables were also risk factors for WNV mortality. The probability that a carcass tested positive for WNV increased with the age of the dead bird and as summer progressed. WNV-positive carcasses also had a lower body condition index than WNV-negative carcasses. We believe that the first major wave of American Crow mortality observed in the early summer of 2005 was the result of natural mortality among young American Crows. Because this mortality was not linked to WNV, it appears that American Crow may not be a good species for early detection of WNV activity. Our data also suggest that second-year American Crows play a major role in propagating WNV during their movements to urban land covers during midsummer.

Development of agroenvironmental indicators to evaluate the hygienic pressure of livestock production on human health

Infections by enteropathogenic microorganisms linked to agroenvironmental contamination represent a significant threat to urban and rural communities. To better characterize and manage this risk, it is necessary, not only to accurately describe enteric illnesses occurring over time or across regions, but also to correctly assess exposure attributable to this environmental pollution. New agroenvironmental hygienic pressure indicators (AHPIs) were developed to synthesise relevant data expressing this exposure. They were derived from a conceptual framework for developing sustainable agriculture indicators and specifically adapted for describing the microbial risk of water contamination by livestock operations. The proposed indicators include two components, and five attributes whose values are calculated at the livestock operation level from a set of available data related to the fields of microbiology, animal production, agronomy, hydrology, and meteorology. They are then aggregated at a higher geographical level to better express exposure of human populations to potential of water contamination by zoonotic enteropathogens. The indicators are calculated separately by zoonotic enteropathogens, and by water source (surface or groundwater). They take into account the various animal species within each livestock operation. When validated, the proposed indicators will allow decision-makers and public health officials to better manage crucial issues in the area of water safety and agriculture.

Bioeconomic Modelling of Raccoon Rabies Spread Management Impacts in Quebec, Canada

Beginning in 2006, point infection control operations and aerial distribution of oral rabies vaccines along the US border were performed in Quebec, Canada, to control the potential spread of raccoon rabies. A benefit-cost analysis assessed the economic efficiency of this rabies control programme into the future. In this study, a mathematical simulation model was used to determine the potential spread of raccoon rabies from the 2006 index case, and incidence rates of human post-exposure prophylaxis (PEP), animal testing and human exposure investigations were calculated. Benefits were calculated as the potential savings from reduced numbers of human PEP, animal testing and human exposure investigations owing to control, which ranged from