Pig herds having a single reactor to serum antibody tests to Aujeszky's disease virus.

The introduction of Aujeszky's disease virus into a herd of pigs usually results in a rapid spread of the virus and a high percentage of pigs become seropositive. However, herd monitoring for the virus occasionally reveals a single seropositive breeding pig, referred to as a single reactor. The seropositive status of single reactors may be due to previous vaccination against Aujeszky's disease, or to exposure to a field strain of the virus, or to a false positive reaction in the serological assay. During a monitoring programme in Minnesota, 30 pig herds with single serological reactors were detected. Twenty-seven of these single reactors from 19 herds were segregated from their herds immunosuppressed with dexamethasone. Aujeszky's disease virus was isolated from four of the 27 pigs. Three of the four herds subsequently had outbreaks of Aujeszky's disease, suggesting that some single reactors were infected with Aujeszky's disease virus and had the potential to spread the virus within and between herds.     

Eradication of Aujeszky's disease from New Zealand pig herds 1976-1997.

Aujeszky's disease was first diagnosed in the North Island of New Zealand in 1976. It has never been reported in the South Island. An industry-funded eradication programme was initiated in 1989 to eradicate the disease from the national pig herd. By using a combination of serological surveys, abattoir surveillance, test and slaughter, depopulation, vaccination and movement restrictions, Aujeszky's disease was eradicated by 1997.     

Vaccination and eradication programme against Aujeszky's disease in five Swedish pig herds with special reference to herd owner attitudes

A vaccination eradication programme against Aujeszky's disease (AD), based on the use of gE-negative killed vaccine, was carried out between 1987 and 1992 in 5 Swedish weaner pig producing or farrow-to-finish herds, with 63 to 398 breeding animals. All breeding animals were tested at the start and the end of the programme. Seroprevalence to Aujeszky's disease virus (ADV) ranged between 47% and 100% in the herds at the first test. During the programme, all breeding animals were vaccinated simultaneously every 4 months and ADV-free replacement animals were vaccinated shortly after arrival and boostered within a month. In one herd only, a limited number of fatteners were vaccinated. The herds were declared free (gE-negative) 12 to 53 months after the start of the programme. When all seropositive breeding animals had been culled, the programme ended after 2 negative tests of the breeding animals. Seroconversion was limited in all herds but one, where initially no isolation unit was available for replacement animals. The attitude of the herd owners towards the programme and the special conditions prevailing in the herds are discussed. It is suggested that vaccination may promote risk behaviour of herd managers.     

Vaccination and eradication programme against Aujeszky's disease in Sweden, based on a gI ELISA test

A killed gI-negative vaccine combined with a gI enzyme-linked immunosorbent assay (ELISA) test was used for the first time in Sweden in an attempt to eradicate Aujeszky's disease from a weaner pig producing herd. The herd had experienced three severe outbreaks of the disease during a 10 year period and at the start of the programme 96 per cent of the herd's 104 breeding animals were seropositive to the Aujeszky's virus. In addition, there was serological evidence of active virus circulation among younger animals. During the programme, all breeding animals were vaccinated every sixth month and replacement animals were tested free of disease and vaccinated before entry into the herd. When the originally seropositive animals had been rotated out of the herd, all breeding animals and a sample of weaner pigs were tested twice at six weeks' interval. No seroconversions to gI had taken place and the herd was declared Aujeszky's disease-free, 22 months after the start of the programme.     

On-farm eradication of foot-and-mouth disease as an alternative to mass culling

A control and eradication programme for foot-and-mouth disease (FMD) was initiated on a 1500-sow farm in Asia as an alternative to mass culling. The programme was based on mass vaccination and exposure to FMD virus to ensure the development of effective immunity throughout the population. Pigs are not long-term carriers of FMD virus and it should be eliminated by 21 days after infection. Entry of breeding stock was temporarily halted and the sow herd was partially depopulated in order to create a buffer between the infected and uninfected animals. After exposure to the virus and partial depopulation, the virus was eliminated through unidirectional pig flow and strict all-in/all-out procedures, and by thorough cleaning and disinfection of the buildings. Twelve months after the initial outbreak, the eradication plan was completed and successful. In parallel with the eradication programme, a small-scale isolated weaning project was carried out with the sow population that was moved out of the affected farm; 708 piglets were weaned to a separate facility 300 m away. No clinical signs of FMD were observed and the piglets remained serologically negative.     

A novel concept for the control of Aujeszky's disease: experiences in two vaccinated pig herds

A study was conducted to examine the usefulness of a glycoprotein I (gI)-ELISA to monitor Aujeszky's disease virus infection in two vaccinated pig herds; the gI-ELISA can differentiate between pigs infected with Aujeszky's disease virus and pigs vaccinated against Aujeszky's disease with gI-negative vaccines. The two herds had been vaccinated with gI-negative vaccines for several years. The first survey, in September 1986, revealed that approximately 10 per cent of the breeding pigs in a large multiplier herd were seropositive for antibodies to gI of Aujeszky's disease virus, and it was decided to try to eliminate the virus from the herd by gI-ELISA testing and culling of gI-seropositive pigs. A one month quarantine period for incoming stock was established, and only gI-seronegative pigs were admitted to the herd. After two rounds of testing and culling the herd appeared to be free of wild-type Aujeszky's disease virus, and neither Aujeszky's disease virus nor antibodies could be detected either in 21 sentinel pigs placed on the farm or in 347 stillborn piglets or piglets that died shortly after birth. The herd probably remained free of Aujeszky's disease virus until the end of the 27-month period of monitoring except for two of 639 breeding pigs that were unexpectedly found to be positive in the gI-ELISA in November 1987. These sows were culled. A second breeding herd was monitored for antibodies to gI of Aujeszky's disease virus for two years. The gI-seropositive sows constituted approximately 30 per cent of the herd's breeding pigs, but they were not culled.(ABSTRACT TRUNCATED AT 250 WORDS)     

Eradication of porcine sarcoptic mange within a health declared production model

The success of a large-scale eradication programme against sarcoptic mange was evaluated in piglet producing herds belonging to the health class LSO 2000. These farms are monitored to be free from sarcoptic mange, swine enzootic pneumoniae, swine dysentery and progressive atrophic rhinitis. The local veterinarians were instructed to eradicate sarcoptic mange from the herds by 2 ivermectin injections 14 days apart or 3 treatments with phoxim pour-on 6 days apart before the farms were able to join the health class. The study consisted of a questionnaire administered to the farmers, farm visits and follow-ups associated with the regular control of the health class. A questionnaire was sent to all of the 379 accepted farrowing farms. Altogether 323 farmers had initiated an eradication programme at least 7 months before the questionnaire was distributed and 96% of them believed that the mange eradication programme had been successful. In most of the successful herds (90%), the local veterinarian had treated the animals by the recommended methods, and the majority of the farmers (88%) had cleaned and sprayed the pens with insecticides on the days of treatment. Three out of the 7 unsuccessful farms had employed methods other than those recommended. Twenty-five herds were randomly selected for an intensified control. The rubbing index was < or = 0.1 in all herds visited, indicating freedom from mange. Sows or gilts, 15-20 animals per farm, were skin scraped and no Sarcoptes scabiei was found. The same animals were blood sampled and serum antibodies to S. scabiei were measured by an indirect ELISA. All except 1 farm had low optical density (OD) values in most of the samples. The owner of that farm had become uncertain about the mange status of the herd and had recently retreated all animals with acaricides. The number of complaints about mange in the finishing units buying health class feeder pigs was low. The study demonstrates that it is possible to run an eradication programme against sarcoptic mange, in which a large number of farmers together with their veterinarians participate. It is possible to eradicate mange not only at the herd but also at the population level. The ELISA test employed proved to be a possible tool to monitor the efficacy of mange-eradication programmes.     

Aujeszky's disease: sanitation of swine herds in enzootically infected areas using labelled vaccines

Both in the Federal Republic of Germany and in some neighbouring countries the epizootic situation of Aujeszky's disease has been unsatisfactory for a long time, especially in areas with a high pig density. New findings on vaccines with certain protein deletions have recently indicated the possibility that the disease might be eradicated even in vaccinated herds. By using labelled vaccines it seems possible to distinguish the carriers of vaccine virus antibodies from the carriers of field virus antibodies and to eliminate the animals infected with field virus, while leaving the other animals in the herd and protecting them from infection by vaccination. This procedure would also be practicable in epizootically infected areas and would be less expensive than eradicating the disease on the basis of serological tests without using vaccines. A skeleton of an eradication programme, which was discussed and agreed with scientific experts and with the Federal Laender, as well as rough estimates of costs are being presented.     

Eight years' experience with a register of pig herds monitored for Aujeszky's disease

The Pig Health Control Association launched a control scheme for Aujeszky's disease in Britain in January 1978. Participating herds must not show clinical signs suggestive of Aujeszky's disease and must be serum-sampled every six months for the absence of antibodies. Importations are allowed only from listed herds, or through hysterectomy or hysterotomy, embryo transfer, or artificial insemination (the donor animals in each case having been serologically screened beforehand). During the subsequent eight years, 103 herds have qualified, and at the end of 1985, 49 herds (average size 249 sows) were listed. Despite a high degree of inter-herd stock movements, no clinical or serological evidence of Aujeszky's disease has occurred, and the disease has not arisen in any herd established from the listed herds. During the same period, Aujeszky's disease was spreading in Britain and an eradication programme began in March 1983. By the end of 1985, 502 herds not on the Pig Health Control Association's scheme comprising 421,825 pigs had been slaughtered, together with 259 serologically positive animals in 69 other herds. The Pig Health Control Association's register has provided a safe source of stock.     

Influence of the vaccination regime on the herd immune response for swine fever

Surveys in three areas with emergency vaccination programmes revealed that 86-94% of the pigs vaccinated in the initial mass campaign had developed an adequate antibody titre against swine fever as compared with 29-55% of the pigs involved in supplementary vaccination campaigns. The serological response of piglets born from immunised sows rose with the age of vaccination from 11% at 5-6 weeks to 42% at 7-8 weeks and 77% at 9-10 weeks. In piglets born from immunised sows, a 50% 'take' of the vaccine was not obtained before the age of 8-9 weeks. Re-vaccination of gilts born from immunised dams improved the immune status to almost the level observed after mass campaigns. To strengthen herd immunity in vaccination areas, the age of supplementary vaccination has been raised to 7-9 weeks, while breeding gilts are re-vaccinated when 6-7 months old.     

Spread and control of Aujeszky's disease (AD).

The review deals with practical aspects of control and eradication of Aujeszky's disease (AD) and the various factors concerned with it. These are resistance of virus to environmental conditions, amounts of virus necessary for infection, virus excretion, virus latency, mode of virus transmission, and vaccination. Notification of AD is a precondition of control. Several measures are necessary on the infected farm to prevent virus spread. Eradication can be done by slaughter of all the seropositive animals. However, until recently this is impossible in severely infected vaccinated areas on economic reasons. The development of glycoprotein-deleted vaccines now allows the differentiation between vaccinated and infected animals by ELISA. Thus, a combination of vaccination and removal of infected pigs is possible, resulting in a more economic way of expanded eradication.     

Long-term study (2005–2010) on the vaccination with BoHV-1 glycoprotein E-deleted marker vaccine in selected two dairy herds in Turkey

A follow-up study from 2005 to 2010 was carried out in two herds where eradication programme for the bovine herpes virus-1 (BoHV-1) infection depends on the vaccination with inactivated glycoprotein E-deleted vaccine that was started in 2001 following the vaccination with inactivated conventional vaccine between 1999 and 2001. For serological screening, a total of 12,976 sera sampled over several sampling times approximately 6 months of interval during 5 years (2005–2010) were tested for glycoprotein E (gE)- and glycoprotein B-specific antibodies using ELISA. According to the serological evidence, the long-term persistence of BoHV-1 antibodies, success of marker vaccine, first vaccination time of the calves in herds regularly vaccinated, etc. were discussed in this paper. In conclusion, the vaccination programme using gE (?) marker vaccines, with making efforts to prevent the other factors about transmission of infection, was suggested for the eradication of BoHV-1 infection in Turkey as many EU countries. This is the first report on the BoHV-1 eradication programme in some dairy cattle in Turkey.     

Spatial relative risk mapping of pseudorabies-seropositive pig herds in an animal-dense region

This paper describes a new approach for spatial relative risk mapping as a tool for geographical risk assessment. The spatial epidemiological analysis is based on geographically referenced data about pseudorabies (Aujeszky's disease) virus infections at farm level in a region of high animal density in Germany at the beginning of the national eradication project. On the basis of serological findings 186 farms were classified as positive out of a total of 482 investigated farms listed in veterinary administrative registers. Geographical cluster analysis was used to identify two areas of high risk (RR = 2.4 and 3.3). Non-parametric density estimation was used to estimate the proportion of infected farms per square kilometre. Furthermore, the spatial relative risk function was approximated through the prevalence ratio defined by the ratio of the local prevalence and the overall prevalence of the farms outside the cluster regions. The corresponding approximated relative risk map indicates and quantifies a clear spatial pattern of disease frequency.     

Field trials of an inactivated virus vaccine against porcine parvovirus.

Serological response and reproductive performance were estimated in field trials of an inactivated virus vaccine against porcine parvovirus. Experiments were carried out in 10 selected pig breeding herds. A total of 277 seronegative gilts were used. Two hundred and twenty animals were vaccinated twice before mating, fourteen days apart and revaccinated after farrowing. Blood samples were obtained from both vaccinated and non-vaccinated (57 animal) control gilts, one week after the 2nd dose of vaccination, at farrowing time and one week after revaccination. Although there were considerable variations among the herds, the number of returns to oestrus in all herds was higher in vaccinated gilts (11.81%) than in the controls (10.52%). This difference, however, was not statistically significant. The reproductive performance results revealed the absence of an increase in the total born, as pooled values, in vaccinated gilts compared to controls. However, when these results are interpreted in relation to serological data, many control gilts were already seropositive before mating, or remained seronegative at farrowing. According to our results, the duration of immunity with this vaccine is apparently short, as there is a clear decrease in the titres between the 1st and the 2nd sampling times (2.35 +/- 0.14 and 1.97 +/- 0.08, respectively).     

猪场猪瘟、伪狂犬病免疫程序调整的可行性分析

为避免按不合理的免疫程序接种后给母猪的生产和仔猪的生长发育等带来负面影响,如仔猪应激,妊娠母猪流产及胚胎死亡等,金华种猪场以抗体测定为依据对猪瘟、伪狂犬病的免疫接种效果作了相应的试验后得出:后备母猪在配种前３周接种猪瘟疫苗,１５０日龄和２００日龄接种伪狂犬病疫苗;母猪在断奶时接种猪瘟疫苗,产前３周接种伪狂犬病疫苗;仔猪分别在２１日龄和５０~６０日龄接种猪瘟疫苗。     

Sarcoptes scabiei var. suis in a closed pig breeding and fattening herd and control possibilities after treatment

On an Austrian pig breeding and finishing farm containing 13,000 pigs a mange prevalence of 38.7% according to the results of the skin scraping and 28.2% based on serology was determined. Due to the insufficient treatment (single treatment of the sows using Phoxim [Sebacil pour on]), sustainable control was impossible. That could be confirmed by the high number of mange positive gilts and finishing pigs. Before eradication started the following prevalences of mange could be found: sows 6.74% (skin scrapings), respectively 6.18% (serologically), gilts 18.18% resp 28.67%, finishing pigs 54.35% and 38.58%. The breeding stock for eradication was treated with doramectin (Dectomax) injectable solution and the finishing pigs with Ivomec-praemix, both applied twice. The success of treatment of the different farm units and of different age groups was controlled for the following ten months by combined diagnostic methods. In addition to skin scrapings, serum and colostral samples were carried out using a commercially available ELISA licensed for investigation of blood serum and colostrum. After treatment antibodies in the serum of the sows and gilts and Sarcoptes mites in their skin scrapings were detectable for up to four months after treatment. In serum samples of piglets and colostrum samples antibodies against Sarcoptes mites were detectable up to five months after final treatment. Due to the higher level and longer verifiability of antibodies in blood samples of piglets for five months after treatment and high prevalences their use as a diagnostic tool can be recommended. In contrast the use of colostral samples for routine diagnosis should be investigated more thoroughly. The comparison of the results of different diagnostic methods showed that for reliable mange diagnosis combined methods are recommended.     

Field trials of an inactivated, oil-emulsion porcine parvovirus vaccine in British pig herds

Inactivated porcine parvovirus vaccines have been available commercially in Britain since 1984 and are now widely used in breeding herds. To investigate their value in cost benefit terms an oil-emulsion vaccine developed at Weybridge was used in trials on 1243 gilts in 12 herds during the period 1984 to 1986. In each herd approximately half the gilts were given the vaccine before breeding and the remainder were left unvaccinated. Blood samples were taken at vaccination and two to four weeks later to measure the serological responses, and the reproductive performances of the two groups were compared. When the data from all the gilts in the 12 herds were combined and analysed together there was surprisingly little difference between the reproductive performance of the vaccinated and unvaccinated groups. Only when the results from individual herds were analysed and interpreted against a background knowledge of wild parvovirus activity (as derived from a study of the serological results) did an understanding and evaluation of the benefits of vaccination become possible. As herds vary with respect to the absence or presence of porcine parvovirus and the epidemiology of the infection it is recommended that vaccination be used with discrimination; it should then prove highly cost effective.     

Effect of space allowance during rearing and selection criteria on performance of gilts over three parities in a commercial swine production system

A total of 1,257 gilts were used to determine the effect of space allowance during rearing and age at puberty on total pigs produced and removal rate over 3 parities. There were 2 treatments. In treatment 1, gilts were given a space allowance of 1.13 m(2)/gilt (15 gilts per pen), and in treatment 2, gilts were given 0.77 m(2)/gilt (22 gilts per pen). Gilts (38 kg and 75 d of age) were individually weighed upon entry and before leaving the rearing site. They were scanned for backfat thickness and loin depth and had their feet and legs scored for structure, movement, and toe evenness before leaving the rearing site. Commencing at approximately 140 d of age, gilts were exposed to a vasectomized boar once daily with age of puberty recorded for all gilts attaining puberty before leaving the rearing site. Gilts were then moved to a specialized gilt breeding farm. When confirmed pregnant, they were moved to 1 of 9 sow farms at random, where gilts remained until removal from that herd. Space allowance in rearing had no effect (P > 0.29) on growth rate in rearing, backfat thickness and loin depth, total pigs produced, or removal rate. A greater percentage of gilts attained puberty (P = 0.02) and attained puberty at a younger age (P < 0.01) when given the greater space allowance in rearing. Gilts given the lower space allowance in rearing had more (P = 0.04) cracks on their rear hooves. Gilts attaining puberty at a younger age (<185 d) had a greater growth rate in rearing, greater backfat thickness at 200 d of age, and produced more (P < 0.05) pigs over parities 1 to 3. Gilts in the fastest growth-rate group in rearing (>860 g/d) had greater (P < 0.05) total born in parity 1, but total pigs produced to the end of parity 3 was not different (P = 0.47). Contrary to expectation, a fast growth rate in rearing did not negatively affect removal rate. Gilts served between 240 to 260 d of age produced more (P < 0.01) pigs by the end of parity 3 than those served at >260 d of age, whereas a greater (P < 0.01) percentage of gilts served at >280 d of age were removed by the end of parity 3. In conclusion, space allowance in rearing did not affect total pigs produced or removal rate; however, gilts that attained puberty at a younger age produced more pigs over parities 1 to 3.     

Programming for Preventive Disease and Improved Production in Sheep

Sheep losses each year are high in all types of rearing systems throughout the United Kingdom. Losses could well be reduced by a closer relationship between the sheep owner and the veterinarian. A closer relationship should involve the development of a simple disease preventive programme requiring a number of regular farm visits each year. Any such programme could attempt to control disease mainly by preventive methods, establish a complete parasite control programme and incorporate a high degree of instruction. There is probably a need for many veterinarians to attend specialist sheep courses, and suggestions are offered whereby the situation could be improved.     

Dutch paratuberculosis programme history, principles and development

Organised disease control started in the Netherlands in the 18th century with governmental attempts to eradicate cattle plague. At the beginning of the 20th century, the dairy industry and cattle breeding organisations initiated a programme to control infectious diseases by means of a complex system of rewards and penalties. This was also the reason for establishing the Animal Health Service in Friesland in 1919. The history of programmes to control paratuberculosis in sheep, goats, and cattle in various countries is described. The vaccination of young animals seems to be an effective measure in the prevention of clinical paratuberculosis, although changes in management and hygiene practices are also important. A control programme for infectious cattle diseases has a number of phases (a lifecycle) and different components. Two components are essential for success, namely: open and regular communication with farmers, veterinary practitioners, and other people involved and a good registration and identification system for cattle, herds, and veterinary practitioners. The Dutch paratuberculosis programme has 10 herd status levels: 5-10 for non-suspect herds and 1-4 for infected herds or herds of unknown status. The higher the status, the greater the chance that a herd is free of paratuberculosis. An outline is given of the Dutch paratuberculosis programme including its objectives, basic principles for eradication, communication plan, legal action, logistic considerations, and complementary research programme.