Q fever in humans and farm animals in four European countries, 1982 to 2010

Q fever is a disease of humans, caused by Coxiella burnetii, and a large range of animals can be infected. This paper presents a review of the epidemiology of Q fever in humans and farm animals between 1982 and 2010, using case studies from four European countries (Bulgaria, France, Germany and the Netherlands). The Netherlands had a large outbreak between 2007 and 2010, and the other countries a history of Q fever and Q fever research. Within all four countries, the serological prevalence of C. burnetii infection and reported incidence of Q fever varies broadly in both farm animals and humans. Proximity to farm animals and contact with infected animals or their birth products have been identified as the most important risk factors for human disease. Intrinsic farm factors, such as production systems and management, influence the number of outbreaks in an area. A number of disease control options have been used in these four countries, including measures to increase diagnostic accuracy and general awareness, and actions to reduce spill-over (of infection from farm animals to humans) and human exposure. This study highlights gaps in knowledge, and future research needs.

Risk factors for respiratory diseases in New Zealand pig herds

AIMS

A survey of lung lesions and risk factors for respiratory diseases was conducted in order to estimate the prevalence of respiratory diseases in the New Zealand pig population and to identify influential management practices.

METHODS

Eighty-nine New Zealand pig farms with a minimum herd size of 50 sows participated in the survey, and risk factor data were collected using a mailed questionnaire. Abattoir data were recorded once in winter 1995 and once in summer 1996. A total of 6887 lungs was inspected.

RESULTS

The prevalence of enzootic pneumonia, pleuropneumonia and pleurisy in winter was 63.4%, 2.7% and 19.1%, respectively. Enzootic pneumonia was significantly less frequent in summer. Pleuropneumonia/pleurisy was found to be more prevalent in the South Island. The univariate risk factor analysis was consistent with earlier published evidence on the importance of environmental factors related to housing and management of the farm. The multivariate models for enzootic pneumonia and pleuropneumonia or pleurisy had a reasonably good predictive power of 81-91% for farms with high disease prevalence.

CONCLUSION

The results are useful to model the disease process on high-risk farms, which account for a considerable proportion of the New Zealand pig population.

[Demographic characteristics of dog population in Switzerland]

Dog Registration data from three Cantons, patient data of 13 veterinary practices and registrations in the Swiss Dog Pedigree Book were collected, analysed and compared to results of a commercial household survey, to assess demographic characteristics of dog population in Switzerland. The proportion of "pure-bred" dogs was different depending on how the term was used, varying from 24% regarding registrations in the Swiss Dog Pedigree Book, to 75% regarding dogs with only one breed recorded in Veterinarian's patient-history-management systems. Most popular breeds were dogs called "German Shepherd/Shepherd", followed by the Labrador and Golden Retriever. Comparison of different data sources suggested regional differences in popularity of breeds. The average life expectancy was estimated on 10.5 and 11 years. Sex distribution was equal. One third of all male dogs and half of the female dogs were neutered. Regardless sex, neutering was more common in cross-bred dogs than in "pure-bred" dogs (OR = 1.9). Some bias in all sources had to be considered and there was a major concern regarding definition of breeds. However, the study was able to add different parameters out of different sources to a homogenous picture of demographic data of dog population in Switzerland.

Veterinary epidemiology--a key to sustainable pig production in Switzerland

Sustainable animal production requires a healthy production system including healthy animals producing wholesome products. Epidemiology as a discipline is concerned with the occurrence of disease or disease indicators in populations as well as with factors influencing disease occurrence. By providing this information, epidemiology contributes significantly to the development and maintenance of healthy livestock. This is illustrated with the example of the enzootic pneumonia (EP) eradication programme of Switzerland. A series of observational studies were conducted in order to obtain the necessary knowledge to implement an area-wide EP eradication programme. The issues of economical eradication strategies at the herd level and the risk of re-infections were addressed. Simulation modelling and economical analysis were also applied. These research projects led to the successful start of a national eradication programme. The example of the EP eradication programme illustrates that applied epidemiological research provides critical information for the planning, implementation and evaluation of disease control programmes and is thus a key tool in developing sustainable animal production.

Relationships between animal health monitoring and the risk assessment process

Risk assessment is part of the risk analysis process as it is used in veterinary medicine to estimate risks related to international trade and food safety. Data from monitoring and surveillance systems (MO&SS) are used throughout the risk assessment process for hazard identification, release assessment, exposure assessment and consequence assessment. As the quality of risk assessments depends to a large extent on the availability and quality of input data, there is a close relationship between MO&SS and risk assessment. In order to improve the quality of risk assessments, MO&SS should be designed according to minimum quality standards. Second, recent scientific developments on state-of-the-art design and analysis of surveys need to be translated into field applications and legislation. Finally, knowledge about the risk assessment process among MO&SS planners and managers should be promoted in order to assure high-quality data.

[Food safety achieved through herd management]

Most animal-derived food products originate from production chains consisting of a series of well-defined, separate production steps. Undesired events affecting food safety can principally occur at any point within the production chain. The principle of integrated food safety assurance from stable to table has therefore been established. The livestock holding has thus to be understood as a fix element of the production chain, and the producer has to accept a part of the responsibility for food safety. On a farm, food safety can be negatively affected by animal feed (microbiological or toxicological contamination), management (hygiene, stocking density, cleaning and disinfecting), veterinary treatments (use of antibiotics) and recycling of slurry. Most relevant practices can be summarised under the standard of "good farming practice". HACCP programmes as they are applied in the processing industries could in principle also be used at the farm level. Influential management steps would need to be identified and controlled. This approach is, however, still in its infancy at present. Using the current monitoring systems, microbiological and toxicological problems in food are difficult to be identified before the end of the production chain. As the cause of a problem can be found at the farm level, traceability of products through the production chain is essential. In Switzerland, traceability of animals is realised using compulsory animal identification and the animal movement database. Using this link, information on the health status of a herd could be made available to the slaughterhouse in order to classify animals into food-safety risk categories. This principle is a key element in the ongoing discussion about visual meat inspection in Europe and elsewhere.

Designing serological surveillance programmes to document freedom from disease with special reference to exotic viral diseases of pigs in Denmark

Surveillance programmes based on laboratory screening tests are increasingly used to document freedom from disease in order to facilitate trade. The following aspects must be considered when designing such programmes: diseases to be selected; epidemiology of the diseases; unit of analysis (animal or herd); target age group (or target farm type); test characteristics and sample size. Issues related to these aspects are discussed and illustrated using the example of serological surveillance for exotic viral diseases in the pig population of Denmark. Sampling designs based on individual animal samples are compared with herd-based sampling (two-stage sampling). While the latter is likely to require a larger sample size, the increased level of information and the reliability of the results obtained are considered to be worth the expense. Issues related to the development of international standards for declaring freedom from disease are discussed. The authors conclude that international standards are desirable, providing that these standards represent scientifically valid principles.

Epidemiological investigation of the influence of environmental risk factors on respiratory diseases in swine--a literature review

The influence of environmental and management factors on respiratory diseases in pigs is reviewed from an epidemiological point of view. The suitability of methods for the investigation of risk factors is discussed including aspects of study design, case definition, exposure assessment and data analysis. The results of published studies suggest a causal web of factor interaction, the analysis of which provides considerable challenges for current epidemiological techniques. New approaches to the problem should be further explored in the future in order to provide reliable advice to decision makers.

Within-farm spread of classical swine fever virus--a blueprint for a stochastic simulation model

A stochastic simulation model to investigate the transmission of classical swine fever (CSF) virus within an infected farm is described. The model is structured according to the processes that occur within and between management groups (pig units or houses). It uses the individual pig as the unit of interest and estimates the number of animals in the states 'susceptible', 'infected', 'infectious', and 'removed' for each day of the disease incident. Probabilities are assigned to the transitions between states. The probability of a pig becoming infected is made dependent on the probability of contact between a susceptible and an infectious pig as well as the probability of transmission. The more pigs become infected in one unit, the more likely is subsequent spread to another management group on the farm. Ultimately, the probability that a shipment of pigs from the farm will include at least one infected pig can be estimated in order to identify high-risk movements during a CSF epidemic. The model results were compared with experimental data on CSF transmission within one pig unit (management group). It could be shown that the model was capable of reproducing the experimentally observed infection and mortality rates. To improve the input parameters and for further model validation, more experimental data and field data from CSF outbreaks are needed.

The 1997-1998 classical swine fever epidemic in The Netherlands--a survival analysis

The aim of this analysis was to characterise the temporal pattern of infection during the 1997/98 classical swine fever (CSF) epidemic in The Netherlands and hence identify and quantify risk factors for infection in different enterprise types and areas. Survival analysis and Cox proportional hazards regression were used to describe the epidemic. Substantial differences in temporal survival patterns (herd breakdown rate) were found between areas where different control policies operated. Factors with a significant influence on the infection hazard of individual herds included: sow numbers as a percentage of total sows and fatteners (HR = 3.38 for mixed herds (0.1-60% sows) vs. fattening herds (0% sows) and HR = 2.74 for breeding herds (60-100% sows) vs. fattening herds), the number of 'transport contacts per month' (>0.3 vs. <0.3; HR = 4.11), pig density (pigs/km2) in the area (HR1000 pigs 1.48) and herd size (HR100 pigs = 1.01). Pre-emptive slaughter in an area appeared to be associated with lower subsequent disease levels. Higher frequency of transport contacts for welfare slaughter during the epidemic, however, well regulated and controlled, was associated with a substantially higher risk of becoming infected. The positive association of a higher pig density with CSF indicates the potential importance of local spread as a factor in disease transmission and emphasizes that dilution of the pig population can contribute to reduction in CSF occurrence. This analysis suggests however, that if pre-emptive slaughter can promptly be applied effectively in an area after initial diagnosis, pig density is then not a significant factor. Mixed and breeding herds had a higher probability of becoming infected than fattening herds, possibly due to different types and frequencies of inter-herd contacts. These contacts continue to some extent during the epidemic, despite the standstill of animal movements.

The role of infectious aerosols in disease transmission in pigs

Airborne transmission is of significance for a number of infectious diseases in pigs. The general principles of the airborne pathway, including aerosol production, decay and inhalation, are reviewed. Practical issues regarding aerosol sampling and sample analysis are also discussed. Details of the aerobiology of porcine diseases, including foot-and-mouth disease, Aujesky's disease, and respiratory diseases, are explained. Some additional, potentially airborne diseases are discussed in terms of the evidence for their aerosol transmission. In order to prevent airborne diseases in pigs, dust reduction, air filtration, air disinfection, vaccination and the establishment of disease-free regions could be considered.

EpiMAN-SF: a decision-support system for managing swine fever epidemics

During an outbreak of classical swine fever (hog cholera) or African swine fever, decisions in emergency headquarters have to be made under conditions of time pressure, limited resources and uncertainty. The computer program EpiMAN-SF is designed to support decision-making in this situation by providing up-to-date information and a structured approach to choosing from among competing tasks by combining electronic data management with expert system components. EpiMAN-SF provides accurate and timely summaries of the epidemic, using both text and graphics. In addition, the program provides tools for the epidemiological analysis and forecasting of the emergency, and for assessing current and alternative control strategies. The expert system and simulation models integrated in EpiMAN-SF have been evaluated using sensitivity analysis, historic outbreak data and expert opinion. The results demonstrate that EpiMAN-SF is a valid alternative to traditional data management during exotic disease epidemics.

Epidemiology of bovine virus diarrhoea in cattle on communal alpine pastures in Switzerland

The goal of this study was to determine the influence of communal pasturing on the spread of bovine virus diarrhoea (BVD). The investigation involved 990 Swiss Braunvieh cattle from 149 different owners on seven communal pastures in the Swiss Alps. Prior to pasturing, blood samples were collected from all animals for examination for BVD antigen and antibodies. Serological examinations were also performed during and after pasturing to determine possible increases in seroprevalence and to determine whether seroprevalence was different on pastures with and without persistently infected cattle. At the start of pasturing, nine (0.9%) animals were persistently viraemic. On three alpine pastures, no persistently viraemic animals were detected. The prevalence of persistently infected cattle on the remaining four pastures varied from 0.3 to 3.9%. Of the 990 animals tested at the start of pasturing, 632 (63.3%) were seropositive. Seroprevalence differed among pastures and varied from 21.8 to 85.9%. During the summer, seroprevalence increased on all pastures surveyed, and at the end of the pasture season, 778 (80.1%) of the 971 cattle that were examined twice were seropositive. The incidence of seroconversion was significantly higher on pastures with persistently infected cattle compared with those without; it ranged from 32.7 to 100.0% in the former and from 6.0 to 22.2 in the latter. The results of this study suggest that communal alpine pasturing does play a role in the spread of BVD. The extent of this role depends on the presence of persistently infected animals.

Molecular and immunodiagnostic investigations on bovine neosporosis in Switzerland

Neospora caninum has gained considerable attention through its role in the aetiology of bovine abortion. Due to its close phylogenetic relationship with Toxoplasma gondii, respective unequivocal differential diagnosis deserves special consideration. In order to evaluate the diagnostic performance of molecular and immunodiagnostic techniques and to provide insights into the epidemiological significance of bovine neosporosis in Switzerland, we conducted a study on 83 cases of bovine abortion: of these, 24 (29%) foetal brains were positive by Neospora-PCR, six of these foetuses were simultaneously seropositive in Neospora-IFAT and/or somatic antigen-ELISA. Conversely, four (5%) foetal brains were considered positive by Toxoplasma-PCR, two of which were also seropositive in the Toxoplasma-P30-ELISA and/or direct agglutination test. The seroprevalence in 1689 cattle sera obtained from 113 diary farms was 11.5% (95% confidence interval: 9.2-13.8) by Neospora-somatic antigen-ELISA were and 10.7% (95% confidence interval: 8.3-12.6) by Toxoplasma-P30-ELISA. From the same samples, 1.1%, less than statistically expected, were positive in both ELISA. Within selected groups of cow-calf farms, the seroprevalence determined using the Neospora-somatic antigen-ELISA was 14% (95% confidence interval 5.0-23.0) for dams and 15% (95% confidence interval: 3.0-28.0) for offspring calves. Seroprevalences determined by Toxoplasma-P30-ELISA were 8% (95% confidence interval: 4.0-12.0) for dams and 3% (95% confidence interval: 0.3-6.0) for calves. None of the sera gave a positive reaction in both ELISA. Our data indicated that prenatal neosporosis appears as an important cause of bovine abortion in Switzerland.

Detection of Mycoplasma hyopneumoniae by air sampling with a nested PCR assay

This article describes the first successful detection of airborne Mycoplasma hyopneumoniae under experimental and field conditions with a new nested PCR assay. Air was sampled with polyethersulfone membranes (pore size, 0.2 micron) mounted in filter holders. Filters were processed by dissolution and direct extraction of DNA for PCR analysis. For the PCR, two nested pairs of oligonucleotide primers were designed by using an M. hyopneumoniae-specific DNA sequence of a repeated gene segment. A nested PCR assay was developed and used to analyze samples collected in eight pig houses where respiratory problems had been common. Air was also sampled from a mycoplasma-free herd. The nested PCR was highly specific and 10(4) times as sensitive as a one-step PCR. Under field conditions, the sampling system was able to detect airborne M. hyopneumoniae on 80% of farms where acute respiratory disease was present. No airborne M. hyopneumoniae was detected on infected farms without acute cases. The chance of successful detection was increased if air was sampled at several locations within a room and a lower air humidity.

[Frequency and cost of health problems in Swiss dairy cows and their calves (1993-1994)]

Between July 1993 and July 1994 morbidity and management information related to dairy cows and their calves up to the age of 8 weeks were recorded in 113 randomly selected dairy herds. Also recorded were any costs incurred through disease and prevention. Blood and faeces were analysed with respect to selected pathogens. The health problems most frequently diagnosed in cows were reproductive and udder diseases. Calves suffered most often from diarrhea, omphalitis and pneumonia. The directly disease-related costs per cow-year on average amounted to CHF 139.44 and CHF 4.18 per calf. For prevention, farmers spent on average CHF 10.18 per cow-year. Results from the laboratory analyses indicate that in 68.1% of the farms antibodies against Leptospira hardjo and in 61.9% against Coxiella burnetii were detected. In 8.0% of the farms antibodies against Mycobacterium paratuberculosis were found. Antibodies against BVD virus was present in 99.4% of the farms. Cows from 63.7% farms were infected with gastrointestinal strongylids. Veterinary assistance was required on average 1.96 times per cow-year. In almost all reproductive and puerperal disease cases a veterinarian was consulted while lameness in the majority of cases was treated by the owner. The veterinary profession was hardly ever involved in disease prevention.

The production system and disease incidence in a national random longitudinal study of Swiss dairy herds

A prospective longitudinal observational study based on a stratified random sample of 113 Swiss dairy farms was conducted between April 1993 and July 1994 with the following objectives: (i) to provide statistically valid estimates of disease frequency in the Swiss dairy cow population, and (ii) to evaluate the feasibility and quality of an intensive farm-based data recording system. During the 15-month study period, farmers were asked to record every health and management event related to their cattle herd. This information was mailed back to the study centre at fortnightly intervals. Additionally, farms were visited regularly to verify received data and to discuss specific problems. During these farm visits, management data were recorded using questionnaires. A complete data set of individual animal events with a total observation time of about 1740 cow-years and 275 calf-years was collected and disease-incidence measures were calculated. The most frequent events were reproductive disorders and udder diseases, followed by lameness and metabolic disorders. Experience with the data collection technique used in this study suggests that a farm-based system is effective and reliable, as long as good contact with the farmers is maintained, and incentives to stimulate their motivation are provided.

Absence of chronic effect of exposure to short-wave radio broadcast signal on salivary melatonin concentrations in dairy cattle

A pilot study was conducted to investigate the influence of electromagnetic fields in the short-wave range (3-30 MHz) radio transmitter signals on salivary melatonin concentration in dairy cattle. The hypothesis to be tested was whether EMF exposure would lower salivary melatonin concentrations, and whether removal of the EMF source would be followed by higher concentration levels. For this pilot study, a controlled intervention trial was designed. Two commercial dairy herds at two farms were compared, one located at a distance of 500 m (exposed), the other at a distance of 4,000 m (unexposed) from the transmitter. At each farm, five cows were monitored with respect to their salivary melatonin concentrations over a period of ten consecutive days. Saliva samples were collected at two-hour intervals during the dark phase of the night. As an additional intervention, the short-wave transmitter was switched off during three of the ten days (off phase). The samples were analyzed using a radioimmunoassay. The average nightly field strength readings were 21-fold greater on the exposed farm (1.59 mA/m) than on the control farm (0.076 mA/m). The mean values of the two initial nights did not show a statistically significant difference between exposed and unexposed cows. Therefore, a chronic melatonin reduction effect seemed unlikely. However, on the first night of re-exposure after the transmitter had been off for three days, the difference in salivary melatonin concentration between the two farms (3.89 pg/ml, CI: 2.04, 7.41) was statistically significant, indicating a two- to seven-fold increase of melatonin concentration. Thus, a delayed acute effect of EMF on melatonin concentration cannot completely be excluded. However, results should be interpreted with caution and further trials are required in order to confirm the results.

Animal health monitoring and surveillance in Switzerland

Switzerland has traditionally used a passive disease reporting system for all notifiable diseases. This type of system is not suitable for the documentation of very low prevalences (freedom from disease), sub-clinical cases and non-notifiable diseases. In order to meet the high international standards for animal health surveillance and to fulfil the general need for sound animal health data, Switzerland has evaluated the feasibility of modern monitoring and surveillance concepts. In general, the principle of active surveillance has been acquired and is now being applied whenever possible. In this paper, several examples of Swiss surveillance systems are presented and discussed. They include systematic testing of random population samples, carcase screening at abattoirs and sentinel herd monitoring.

Surveillance of contagious bovine pleuropneumonia in Switzerland

An active surveillance system for contagious bovine pleuropneumonia (CBPP) has been established in Switzerland. The system is based on the detection of typical gross pathological lesions in the lungs of slaughtered cattle, followed by microbiological analysis of the sampled organs and sero-epidemiological investigation of the herd of origin for each suspect case. The programme was tested over six months. The prevalence of lung lesions detected in carcasses during this period in the 108 participating abattoirs was 0.04%, but Mycoplasma mycoides subsp. mycoides SC was not isolated from any of these organs. On the basis of the results presented, there is no evidence of CBPP in Switzerland. The surveillance programme will continue, however, in order to document the situation and eventually obtain a disease-free status in accordance with international standards.

[The changing role of the veterinarian in primary production (demands with respect to diagnostic tests, risk analysis and the need for certification of farms)]

Various new developments in livestock production confront the veterinarian. In addition to Integrated Food Chain Quality Control, certification of farms for animal health status and also for production methods is becoming increasingly important. Certification for veterinary practices is forthcoming. In order to optimize national herd health, quantitative information is needed and certain methods have to be improved. The veterinarian must be able to apply new techniques adequately and to interpret disease- and environment-related data properly. Problem areas are highlighted and different ways of dealing with them are elaborated upon. It is concluded that the veterinarian is strategically positioned to solve these problems, but that suitable, complementary training is needed, as well as new quantitative research.

Risk factors for the reinfection of specific pathogen-free pig breeding herds with enzootic pneumonia

A case control study was designed to determine the risk factors for the reinfection of Swiss specific pathogen-free (SPF) pig herds with enzootic pneumonia. Detailed housing, management and environmental data were collected from 42 case farms and 50 control farms by means of a questionnaire. Factors with a significantly asymmetrical frequency distribution among the two groups were considered to be possibly associated with reinfection; they included the distance to the nearest non-SPF pig herd, the size of that herd, the density of the pig population in the area, the distance to the next road regularly carrying pig transporters and differences in topography. The results tended to support the hypothesis of the airborne transmission of enzootic pneumonia. Using a formula considering the main risk factors, it was possible to classify farms as high or low risk with an 84 per cent specificity and 74 per cent sensitivity.