Establishing a cost-effective national surveillance system for Bluetongue using scenario tree modelling

Vector-borne diseases pose a special challenge to veterinary authorities due to complex and time-consuming surveillance programs taking into account vector habitat. Using stochastic scenario tree modelling, each possible surveillance activity of a future surveillance system can be evaluated with regard to its sensitivity and the expected cost. The overall sensitivity of various potential surveillance systems, composed of different combinations of surveillance activities, is calculated and the proposed surveillance system is optimized with respect to the considered surveillance activities, the sensitivity and the cost. The objective of this project was to use stochastic scenario tree modelling in combination with a simple cost analysis in order to develop the national surveillance system for Bluetongue in Switzerland. This surveillance system was established due to the emerging outbreak of Bluetongue virus serotype 8 (BTV-8) in Northern Europe in 2006. Based on the modelling results, it was decided to implement an improved passive clinical surveillance in cattle and sheep through campaigns in order to increase disease awareness alongside a targeted bulk milk testing strategy in 200 dairy cattle herds located in high-risk areas. The estimated median probability of detection of cases (i.e. sensitivity) of the surveillance system in this combined approach was 96.4%. The evaluation of the prospective national surveillance system predicted that passive clinical surveillance in cattle would provide the highest probability to detect BTV-8 infected animals, followed by passive clinical surveillance in sheep and bulk milk testing of 200 dairy cattle farms in high-risk areas. This approach is also applicable in other countries and to other epidemic diseases.     

The effect of exposure to 400 kV transmission lines on the fertility of cows. A retrospective cohort study

In a nation-wide retrospective cohort study, farms that had cows grazing under 400-kV transmission lines in Sweden were investigated. All farms with cattle and grazing areas beneath 400-kV lines in Sweden, except for the northwestern part of the country where very few farms are located, were sent an inquiry. Information from these farms regarding the period during which the cows had been grazing on pastures exposed to 400-kV lines during the summers of 1978–1980 was collected. The proportion of grazing areas and the exposure time for each age group and 3-month period were calculated for each farm. Information was obtained on 106 farms that were exposed to 400-kV lines for 15 days or more per year and that used artificial insemination. This was the exposed group. Thus, 2050 inseminations could be analysed.In a comparison of the insemination results for each farm, using as non-exposed group all other farms belonging to the same livestock cooperative as the exposed, no statistically significant relationship between exposure of cows to 400-kV lines and inferior A.I. data could be found.Culling frequency as a result of reduced fertility was not significantly different between exposed and non-exposed groups.     

Optimizing early detection of avian influenza H5N1 in backyard and free-range poultry production systems in Thailand

For infectious diseases such as highly pathogenic avian influenza caused by the H5N1 virus (A/H5N1 HP), early warning system is essential. Evaluating the sensitivity of surveillance is a necessary step in ensuring an efficient and sustainable system. Stochastic scenario tree modeling was used here to assess the sensitivity of the A/H5N1 HP surveillance system in backyard and free-grazing duck farms in Thailand. The whole surveillance system for disease detection was modeled with all components and the sensitivity of each component and of the overall system was estimated. Scenarios were tested according to selection of high-risk areas, inclusion of components and sampling procedure, were tested. Nationwide passive surveillance (SSC1) and risk-based clinical X-ray (SSC2) showed a similar sensitivity level, with a median sensitivity ratio of 0.96 (95% CI 0.40-15.00). They both provide higher sensitivity than the X-ray laboratory component (SSC3). With the current surveillance design, the sensitivity of detection of the overall surveillance system when the three components are implemented, was equal to 100% for a farm level prevalence of 0.05% and 82% (95% CI 71-89%) for a level of infection of 3 farms. Findings from this study illustrate the usefulness of scenario-tree modeling to document freedom from diseases in developing countries.     

Spatiotemporal dynamics and risk factors of rotavirus A circulation in backyard pig farms in a Philippine setting

Rotavirus A is one of the leading etiological agents of porcine gastroenteritis, a condition which results to stunted growth among piglets. Moreover, there is increasing evidence for zoonosis of rotavirus A (RVA), which is also the principal cause of diarrhea in children. In the absence of rigorous animal health monitoring in Philippine backyard farms, there is therefore a strong need for RVA surveillance. In this study, 30 randomly selected backyard farms were subjected to surveillance for RVA for 12 months. Results show that RVA detection at a monthly farm-level rate ranged from 0 to 52%, with an overall average of 23%. RVA had higher detection rates in adult pigs compared to young piglets and was most prevalent in non-diarrheic stools, indicating asymptomatic circulation of the virus. Spatiotemporal analysis demonstrated that the viral circulation exhibits a seasonal pattern that peaks and forms geographical clusters during the cooler months of the year, suggesting farm-to-farm transmission. Risk factor analysis identified specific farm conditions that increase the likelihood of RVA circulation: presence of gilts, larger herd size, presence of other animals, and abiotic factors such as low relative humidity and low altitude. The same analysis also revealed three major management practices that can help reduce the pressure of infection in these farms: sanitation and waste disposal, animal grouping, and diet. This new perspective on porcine RVA circulation will benefit the underprivileged backyard farmers and help empower them to protect both animal and public health.

     

2006-2008年我国部分地区规模化猪场PRV血清流行病学调查

为了监测现有的防疫控制体系下我国规模化猪场PRV野毒感染情况,本研究应用IDEXX PRV gEELISA试剂盒对2006年9月～2008年9月送检的14个省（直辖市）89个规模化猪场的5312份样品血清进行PRV野毒抗体检测。结果显示,PRV野毒抗体阳性猪场有65个,占检测猪场总数的73．03％;各猪场血清样品中伪狂犬野毒抗体平均阳性率为23．40％。对不同生长阶段的猪群检测结果分析表明,PRV野毒抗体阳性率随猪龄的增长而升高,且不同生长阶段猪群PRV野毒抗体阳性率差异极显著,而不同季度送检的血清PRV野毒抗体阳性率没有显著差异。本次调查表明,我国免疫猪伪狂犬病毒基因缺失疫苗的规模化猪场仍存在猪伪狂犬野毒感染。     

Patterns of condemnation rates in swine from a federally inspected abattoir in relation to disease outbreak information in Ontario (2005-2007)

Strong correlations between clinical signs on farms and the presence of lesions at slaughter have been reported. The objective of this study was to determine if changes in condemnation rates provide a data source for surveillance of disease outbreaks in pigs. The data were obtained from 1 abattoir in Ontario (2005-2007). The epidemiological relevance of the results was based on an outbreak of porcine circovirus associated disease (PCVAD) in Ontario in 2005. The total condemnations and condemnations due to arthritis and pneumonia patterns reflected the field infection of PCVAD in 2005 followed by the widespread use of porcine circovirus type 2 (PCV-2) vaccine in 2007. In contrast, increased rates of nephritis and enteritis suggested areas for enhanced surveillance for unexplained changes in disease patterns not identified through traditional passive surveillance. Further studies looking at the benefits of using abattoir data should compare condemnation patterns with multiple sources of swine health data.     

我国蚕种场的生产经营状况分析——基于全国136家蚕种场的问卷调查

蚕种场是蚕种生产与经营的微观主体。通过对全国136家蚕种场问卷调查数据的统计分析,认为我国蚕种场普遍存在以下问题:生产设施陈旧,基础条件落后;人员负担沉重,科技力量薄弱;生产经营规模小,产能过剩严重;蚕种销售范围狭窄,区域分割依旧;科技创新能力不足,缺乏多元化拓展的技术支撑;等等。这些问题导致我国蚕种场整体劳动生产率和资产利用率较低,经济效益较差,除广西、广东和云南3省(区)外,其它省份的蚕种场基本处于亏损状态。从所有制结构来看,虽然各类所有制蚕种场总体都是亏损的,但私营蚕种场的亏损相对最小。建议通过深化蚕种场体制改革,放松对蚕种价格与流通的管制,实现规模化蚕种生产经营,推进科技创新步伐,拓展多元化发展渠道以及发挥政府扶持作用等途径,努力提高我国蚕种场的生产经营效益。     

Community-associated methicillin-resistant Staphylococcus aureus in horses and humans who work with horses

OBJECTIVE: To evaluate the prevalence of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) in horses and horse personnel. DESIGN: Prospective prevalence study. SAMPLE POPULATION: 972 horses and 107 personnel from equine farms in Ontario, Canada and New York state. PROCEDURE: Nasal swab specimens were collected from horses and humans on farms with (targeted surveillance) and without (nontargeted surveillance) a history of MRSA colonization or infection in horses during the preceding year. Selective culture for MRSA was performed. Isolates were typed via pulsed-field gel electrophoresis, and antibiograms were determined. RESULTS: MRSA was isolated from 46 of 972 (4.7%) horses (0/581 via nontargeted surveillance and 46/391 [12%] via targeted surveillance). Similarly, MRSA was isolated from 14 of 107 (13%) humans (2/41 [5%] from nontargeted surveillance and 12/66 [18%] from targeted surveillance). All isolates were subtypes of Canadian epidemic MRSA-5, an uncommon strain in humans. All isolates were resistant to at least 1 antimicrobial class in addition to beta-lactams. On all farms with colonized horses, at least 1 human was colonized with an indistinguishable subtype. For horses, residing on a farm that housed > 20 horses was the only factor significantly associated with MRSA colonization. For humans, regular contact with > 20 horses was the only identified risk factor. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirm a reservoir of colonized horses on a variety of farms in Ontario and New York and provide evidence that 1 MRSA strain is predominantly involved in MRSA colonization in horses and humans that work with horses.     

Application of non-structural protein ELISA kits in nationwide FMD surveillance in pigs to demonstrate virus circulation in Taiwan

Large scale surveillance of FMD non-structural protein (NSP) antibody in pigs was conducted to monitor for FMD virus circulation in Taiwan using Ceditest and UBI NSP ELISA kits after recurrence of FMD in 2009. A total of 53,759 serum samples were collected from pigs in the auction markets in 2009. There were 43 farms with positive FMD NSP reactors to both NSP ELISA tests in the nationwide surveillance. After tracing back, clinical examination and the NSP ELISA testing using both Ceditest and UBI on 14 follow-up serum samples from all the herds with confirmed NSP reactors in 2009, there were 4 farms classified as positive on follow-up testing criteria. In this surveillance, we have demonstrated that the NSP ELISA tests of outbreak farms followed by clinical and serological investigation could be used to detect FMD circulation in the pig population in Taiwan even while the national compulsory vaccination program is ongoing.     

Diagnosis of cystic echinococcosis on sheep farms in the south of Argentina: areas with a control program

In 2000 Guarnera et al. proposed using ELISA in canine faeces collected from the ground to detect dogs infected with Echinococcus granulosus, thus determining sheep farms with active transmission. The objective was to evaluate the prevalence of E. granulosus infection in sheep farms of the Patagonia. Sheep farms were randomly selected in the Provinces of Río Negro, Chubut, Neuquén, Santa Cruz and Tierra del Fuego (areas with control programs) and La Pampa (comparison area). From one to three samples of fecal matter were obtained for each sheep farm, which were processed by means of copro-ELISA test with confirmation of positive samples by copro-Western blot. A total of 1042 samples were obtained from 352 sheep farms, 26 (7.3%) proving positive. Of these 5 (6.3%) were from La Pampa, 9 (13.8%) from Neuquén, 4 (4.7%) from Río Negro, 2 (2.9%) from Chubut, 1 (5.9%) from Santa Cruz and 5 (13.9%) from Tierra del Fuego. The identification of parasitized dogs is an essential activity upon which rests the strategy of control and surveillance. Arecoline tests or coproantigen test with fecal matter obtained directly from the dog contribute information on individual prevalence, while the use of coproantigens detected in ground-collected samples transfers the dog unit of observation to units of greater epidemiological value. In the present experience, the technique employed seems promising for its application in systems of epidemiological surveillance of cystic echinococcosis and in drawing a baseline on which to measure the progress of control programs in the Argentine Patagonia in subsequent years.     

An outbreak of sheep-associated malignant catarrhal fever in bison (Bison bison) after exposure to sheep at a public auction sale.

An outbreak of malignant catarrhal fever (MCF) among bison sold at an auction market was studied for an 18-month period. Forty-five of 163 bison submitted for sale from 8 different bison farms died on 7 other destination farms. The outbreak began on day 50 after the sale, peaked between days 60 and 70, and ended on day 220. Twenty-one dead bison were confirmed to be MCF cases by clinical histories, pathology, and detection of ovine herpesvirus-2 DNA in their tissues with polymerase chain reaction assays. Twenty-four dead bison were classified as suspect MCF cases from clinical histories. No cases of MCF were observed among bison remaining on originating farms or resident bison mixed with sale bison on destination farms. There were no sheep reported within 3 km of originating or destination farms, limiting bison exposure to sheep to the auction facility, where sheep were present for less than 1 day. The outbreak provides an illustration of the temporal distribution of MCF mortality expected in bison and an estimate of the time from exposure until death from MCF after a single short exposure to sheep. The study provides evidence that bison with MCF do not transmit MCF to other bison.     

Seroprevalence and risk factors associated with exposure of water buffalo (Bubalus bubalis) to Neospora caninum in northeast Thailand

Water buffalo are important draft animals for agriculture in resource-restricted areas worldwide. Water buffalo were shown to be experimentally susceptible to infection with Neospora caninum, potentially affected by neosporosis, and naturally exposed to the parasite in Asia. Although enzootic to Thailand, the distribution of N. caninum among Thai water buffalo is unclear. The objectives of this study were to determine the seroprevalence of N. caninum among water buffalo of northeast Thailand and to identify risk factors associated with their exposure to N. caninum. Sera from 628 water buffalo from 288 farms were tested with an indirect fluorescent antibody test (IFAT). A total of 57 samples from 48 herds contained antibodies to N. caninum, indicating overall seroprevalence of 9.1% and 16.7% among individual animals and herds, respectively. The overall seroprevalence was highest in provinces located in the Khorat Basin in the southern part of the region tested. Host age was also associated with seroprevalence, with the greatest seroprevalence (16.1%) among buffalo over 10 years of age, followed by 5–10 years of age (13.4%), 3–5 years (9.2%), and less than 3 years (1.2%). These results collectively suggested that horizontal transmission from canine definitive hosts was an important route of water buffalo exposure to N. caninum. These results also verified the importance of risk factor analysis for effective bovine neosporosis control strategies at the local level.     

Comparison of performance of dairy herds that were or were not vaccinated with a bovine herpes virus 1 marker vaccine in 1998

This study analysed the effects of the use of bovine herpesvirus 1 (BHV1) marker vaccine on the performance of dairy cattle. In Spring of 1999, vaccination of 12 herds with the BHV1 marker vaccine resulted in severe animal health problems and mortality. The vaccines used on these farms were all from a batch that appeared to be contaminated with bovine virus diarrhoea virus type 2. This led to a general call to farmers and veterinary practitioners to report side-effects of this vaccine. As a result, more than 7000 farmers reported symptoms. The information was obtained by means of a questionnaire; there was no control group. To determine the effects of the use of the marker vaccine, it was necessary to perform a study based on objectively acquired information. The information collected by the Royal Dutch Cattle Syndicate and the office of Identification and Registration was complied into herd indices on production, udder health, reproduction, and culling. Two groups of dairy farms that had used the BHV1 marker vaccine (attenuated and inactivated vaccine) were compared with farms that were certified BHV1-free. The analyses were performed based on intra-herd comparisons, meaning that per herd each index calculated over a certain period of time after the use of the marker vaccine was compared to a similar period of time prior to the use of the marker vaccine. A total of 144 comparisons were made. Seven comparisons were statistically significant. In two comparisons, the results were in favour of the BHV1-free farms and in five comparisons, the result were in favour of the vaccinated farms. Thus use of the BHV1 marker vaccine could not be proven to affect herd performance. The sensitivity of the tests was very high, so with a high level of probability even very small differences in indices between groups would have been detected.     

Active circulation of bluetongue vaccine virus serotype-2 among unvaccinated cattle in central Italy

Several seroconversions occurring in 2002 among sentinel cattle during the bluetongue-vaccination campaign in Lazio and Tuscany (central Italy) led to the suspicion of vaccine-virus circulation. Therefore in 2003, 17 seroconverting sentinel herds were investigated for the characteristics of the virus involved. From these farms, 91 unvaccinated animals and 57 Culicoides pools were tested for the presence of the bluetongue vaccine virus (serotype-2) or other strains. The presence of vaccine virus serotype-2 was confirmed by PCR followed by restriction analysis in the whole blood of 17 unvaccinated sentinel cattle and 12 pools of Culicoides imicola or C. obsoletus. Of the 17 herds, five were positive only for vaccine virus serotype-2, four were positive for other strains and two for both the vaccine and other strains; the remaining premises were virologicaly negative. The vaccine virus serotype-2 also was detected in areas not included in the vaccination campaign.     

Bacteriologic findings in ostrich (Struthio camelus) eggs from farms with reproductive failures

From January 2001 to December 2002, 543 ostrich eggs were submitted for bacteriologic investigation. The eggs were laid by 387 domesticated ostriches that suffered fertility disorders and that came from 44 farms located in different areas of Northern and Central Italy. Microbiologic investigations showed bacterial isolation in 105 (19.3%) of 543 eggs examined, with a high prevalence of enterobacteria from albumen and yolk. In only a few cases did bacterial isolation result from yolk or albumen alone. An antibiotic sensitivity test was conducted on isolates by the Kirby-Bauer disc diffusion method. This is the first report regarding the microbiologic status of eggs from ostrich farms located in different Italian regions.     

Classical swine fever in The Netherlands 1997-1998: a description of organisation and measures to eradicate the disease

The central and regional organisation of the campaign to eradicate the CSF epidemic in the Netherlands in 1997/1998 is described. The main instruments used in the campaign were based on stamping-out and movement restrictions specified by the European Union. Additional instruments were used for the first time, namely, pre-emptive culling of contact and neighbouring farms, compartmentalisation of transport, monthly serological screening in established surveillance areas and supervised repopulation of all farms in the former surveillance zone. Two other measures, the killing of very young piglets and a breeding ban were introduced to reduce production in established surveillance zones. Several factors complicated the eradication campaign, for instance, the late detection of the first infection; artificial insemination as a source of infection; the organisation of pig farming in the Netherlands, with its highly concentrated production and dependence on the transport of stock from one unit to another; insufficient rendering capacity; decreasing sensitivity of clinical inspection; and extremely high costs.     

Effect of Pseudorabies Purification on the Production Performance in Pig

In order to identify the effect of pseudorabies purification on pig production performance, this paper based on the survey of 63 large-scale pig farms in 9 provinces of China, analyzed the effects of pseudorabies purification on the mortality of pigs, the positive rate of gE, the maternal abortion rate and so on, and compared pig production performance between purification and non-purifucation farms in different scale and different stages of purification. The results showed that the pig production performance was improved by the implementation of vaccine immunization, quarantine diagnosis, elimination of positive animals and culture of healthy animals; Pseudorabies purification had the best effect of improving production performance for the farms with the scale of 16 500 to 84 700 head. The longer the time of pseudorabies purification, the greater the production performance of pigs.     

猪伪狂犬病净化对猪生产性能影响的研究

为了评定猪伪狂犬病净化对猪生产性能的影响,作者调查了中国9个省63个规模化猪养殖场,以调查数据为基础,统计分析了伪狂犬病净化对猪死亡率、猪群伪狂犬gE阳性率、母猪流产率等生产性能的影响,对比了不同规模、不同净化阶段养殖场的猪生产性能的差异。统计结果表明,通过实施疫苗免疫、检疫诊断、淘汰阳性动物、培养健康动物等净化措施,生猪的生产性能明显提高;养殖规模在1.65~8.47万头的养殖场其生产性能提高的效果最优;伪狂犬病净化时间越长,猪的生产性能提高的幅度越大。     

新疆昌吉地区部分规模化猪场PRRSV抗体监测和免疫效果分析

为了查明昌吉地区地区部分规模化猪场猪PRRSV的抗体阳性率及免疫合格率,分别采集了昌吉地区4个免疫了弱毒苗的规模化猪场,和3个免疫了灭活苗的规模化猪场血清共1 036份,采用间接ELISA方法检测其抗体.经检测,4个免疫PRRS弱毒苗规模化猪场总阳性率为79.05％（468/592）,平均KQ为49.63,标准差为39.41.3个免疫PRRS灭活苗规模化猪场总阳性率为62.61％ （278/444）,平均KQ为45.88,标准差为31.22.结果表明,在规模化养猪场使用灭活苗免疫预防PRRS感染作用不如弱毒苗,因此,建议临床应用中应选择弱毒苗为宜,结合检测结果、临床生产数据及猪场已采用猪PRRS免疫程序,建议商品猪在仔猪断奶后初免.在高致病性猪蓝耳病流行地区,可根据实际情况在初免后1个月加强免疫一次,种母猪70日龄前免疫程序同商品猪,以后每次配种前加强免疫一次,种公猪70日龄前免疫程序同商品猪,以后每隔4～6个月加强免疫一次.