Benefit-cost analysis of the current African swine fever eradication program in Spain and of an accelerated program

We predicted the rate of spread and economic losses due to African swine fever (ASF) infections in Spanish swine for a 20 year period using current epidemiological data. Two possibilities for eradication were examined: continuation of the eradication program presently in use, assuming continued funding at present levels, and an accelerated eradication program using more frequent testing to identify seropositive carrier animals. Both programs theoretically would result in the eradication of African swine fever. The calculated benefit-cost ratios were 1.23 and 1.47 respectively. A reduction in current yearly funding would result in a benefit-cost ratio of 0.97, making the program unprofitable according to our model.

The projected year for the eradication of outbreaks is 1996 using provinces as units in the model. Similarly, the projected year for the eradication of seropositive animals is 2001.     

An epizootic of African swine fever in Belgium and its eradication

In March 1985 an outbreak of African swine fever was diagnosed in Belgium, in the province of West Flanders. The source of the infection was probably pork imported from Spain which was fed to only one boar. A total of 12 farms were infected in the epizootic out of 185 farms which were in contact. Severe control measures were imposed and the pigs on 60 farms were slaughtered (34,041 animals). In September 1985, it was concluded that African swine fever had been eradicated. This conclusion was based mainly on a serological survey of 3008 farms (116,308 blood samples) which remained negative.     

Distribution and biology of Ornithodoros erraticus in parts of Spain affected by African swine fever

Ornithodoros erraticus was found in 30.7 per cent, 35.0 per cent and 71.0 per cent of the pig-pens sampled in the provinces of Salamanca, Badajoz and Huelva in which African swine fever is a problem in the rearing of Iberian pigs. Between 38 and 65 per cent of the pig-pens in these areas are now abandoned and their populations of O erraticus are extinct or becoming so because they can no longer feed on pigs, which in Spain are their main hosts. The abandonment of pig-pens has resulted in the elimination of most soft ticks infected with the virus of African swine fever, and means that the distribution of ticks is now irregular and focal. Another factor affecting their distribution is the kind of soil on which the pig-pens are located. In abandoned pig-pens, the adults and large nymphs survive for about five years or longer when animals occasionally enter them. Hungry tick populations may transmit African swine fever when feeding in winter, whereas the populations that have continuous access to pigs do not feed until the pig-pens reach a temperature of 13 to 15 degrees C. In the latter populations, each stage exhibits a single annual peak of activity, which implies that the development from larva to adult takes two to three years. Pigs may die as a result of the bites, but on no occasion were 100 per cent of the fasting ticks seen to feed, even though they had the opportunity of doing so. This may hinder the eradication of this soft tick from infested pig-pens.     

Laboratory diagnosis, epizootiology, and efficacy of marker vaccines in classical swine fever: a review

Detection of classical swine fever virus (CSFV) can be achieved by a range of assays of which the most commonly used are: immunohistochemical and virus culture techniques. New developments have enabled the detection of viral proteins by enzyme-linked immunosorbent assays (ELISAs) and the detection of the viral genome by RT- PCR. So far, laboratory findings show that the latter assays may supplement or replace the conventional techniques in the near future. The detection of serum antibody against structural and non-structural proteins of CSFV has been improved by developments in recombinant DNA techniques and has lead to a range of ELISAs. Although the characteristics of these ELISAs are excellent, positive results still need to be confirmed in the virus neutralization test. The available amount of sequence data enables diagnosticians to type strains of CSFV as different by comparing several parts of the genome. In some cases, this can provide conclusive evidence if a primary or secondary outbreak has been detected. Increased efforts focused on the retrieval of relevant data on the introduction of CSFV in a pig holding and the spread of CSFV in- and between pig holding(s) has generated more insight into the epizootiology of the disease. A successful control and eradication programme for classical swine fever (CSF) can consist of zoosanitary measures and/or vaccination. The latter can compromise the export of live pigs and pig products considerably unless marker vaccines have been used. Several studies were performed to determine the efficacy of an E2 subunit vaccine and live recombinant vaccine candidates. Firstly, we determined the 95% protective dose of an E2 subunit vaccine at 32 microg E2 per dosage after a single application. Further studies with a single administration of the subunit vaccine showed that: the vaccine was stable for a prolonged period after production, was able to reduce horizontal and vertical transmission of CSFV among vaccinated pigs, and provided protection for at least 6 months. An E(rns) antibody discriminatory assay was developed for use in combination with the subunit vaccine. Evaluation of the E(rns) ELISA showed that the sensitivity of the assay was lower than but that the specificity was equal to that of existing antibody assays. Two live recombinant marker vaccines were evaluated for the induction of clinical protection and reduction of transmission of CSFV shortly after vaccination. Results showed that these vaccines provided good clinical protection 1 week after a single vaccination. Research has shown that marker vaccines can be used in the future to support the control and eradication of CSFV.     

Prevalence of African swine fever virus and classical swine fever virus antibodies in pigs in Benue State,Nigeria

Tropical Animal Health and Production - This study investigated the prevalence of African swine fever virus (ASFV) and classical swine fever virus (CSFV) antibodies in pigs in Benue State, Nigeria....     

A highly sensitive and specific gel-based multiplex RT-PCR assay for the simultaneous and differential diagnosis of African swine fever and Classical swine fever in clinical samples

The development and standardisation of a novel, highly sensitive and specific one-step hot start multiplex RT-PCR assay is presented for the simultaneous and differential diagnosis of African swine fever (ASF) and Classical swine fever (CSF). The method uses two primer sets, each one specific for the corresponding virus, amplifying DNA fragments different in length, allowing a gel-based differential detection of the PCR products. Universal detection of ASF and CSF virus strains was achieved through selection of primers in conserved viral genome regions. The detection range was confirmed by analysis of a large collection of isolates of the two viruses. The high specificity of the assay was proven by testing related viruses, uninfected cell line cultures and healthy pig tissues. Additional confirmatory tests of the ASF and CSF virus amplicon specificity, based on restriction endonuclease analysis with BsmA I or Ban II, respectively, are also described. The analysis of whole blood and serum samples from experimentally infected animals proved the usefulness of the method for an early diagnosis of both diseases, even before the appearance of the first clinical signs. A study of 150 positive field samples from several ASF and CSF outbreaks showed the suitability of this method for a rapid (less than five hours), sensitive and specific differential diagnosis in clinical samples. In addition, a highly sensitive and specific uniplex RT-PCR for CSFV was also developed and standardised as a powerful tool for fast and early diagnosis of the disease.     

非洲猪瘟防控的经验和误区

自从2018年8月我国报告首例非洲猪瘟疫情以来,经过3年多的艰难探索,我们面对非洲猪瘟疫情从最初的恐惧和束手无策,到现在的精准清除和“与狼共舞”,疫情防控从被动应对进入到常态化管理和无疫小区建设阶段;非洲猪瘟可防可控的预测得到了实践证明。但是由于我国幅员辽阔,养猪模式多样,疫情防控水平参差不齐;非洲猪瘟疫情零星散发的风险持续存在。下面就我们的观察和调查,对近年来非洲猪瘟防控上的一些经验和误区进行简要分析。     

Serum concentrations of C-reactive protein, serum amyloid A, and haptoglobin in pigs inoculated with African swine fever or classical swine fever viruses

OBJECTIVE: To determine serum concentrations of the selected acute-phase proteins (APPs) haptoglobin, serum amyloid A (SAA), and C-reactive protein (CRP) in pigs experimentally inoculated with classical swine fever (CSF) and African swine fever (ASF) viruses. ANIMALS: 8 crossbred (Large White x Landrace) 10-week-old pigs. PROCEDURES: Pigs were allocated to 2 groups (4 pigs/group). One group was inoculated with the CSF virus Alfort 187 strain, whereas the other groupwas inoculated with the ASF virus Spain 70 isolate. Blood samples were collected at various time points. At the end of the study, pigs were euthanized and a complete necropsy was performed, including histologic and immunohistochemical analyses. RESULTS: Serum concentrations of APPs increased in pigs inoculated with CSF and ASF viruses, which suggested an acute-phase response in the course of both diseases. The most noticeable increase in concentration was recorded for SAA in both groups (up to a 300-fold increase for CSF virus and an approx 40-fold increase for ASF virus), followed by CRP and then haptoglobin, which each had only 3- to 4-fold increases. CONCLUSIONS AND CLINICAL RELEVANCE: Serum concentrations of APPs increased significantly in pigs inoculated with CSF and ASF viruses. However, differences were evident in serum concentrations of the proteins evaluated in this study.     

The role of spatial factors in the success of an Aujeszky's disease eradication programme in a high pig density area (Northeast Spain, 2003–2007)

We tested the role of several spatial variables on the risk of a sow herd being Aujeszky's disease virus (ADV) seropositive in certain areas of North Eastern Spain and during different periods of the eradication programme. Distance to the nearest slaughterhouse, distance to the nearest conventional road and number of ADV serologically positive sows and ADV serologically positive fattening pigs within different distances (1000, 1500 and 2000 m) of each sow herd, were included in a hierarchical Bayesian binomial model. A variable without spatial characteristics, type of herd (farrow to weaning and farrow to finish), was also included. Presence of positive fattening pigs or positive sows up to a distance of 1500 m of a sow herd increased its risk of being seropositive, although this variable had no effect on the risk when located at distances up to 1000 or 2000 m. The number of seropositive sows increased the risk of a sow herd being ADV seropositive only in the first period of study, when the proportion of serologically positive sow herds was nearly 60%. The spatial pattern of the residuals of the hierarchical Bayesian binomial model (observed versus predicted) was very similar to the observed infection in sow herds in all of the eradication periods, showing that spatial factors might not be the main factors related to the eradication of Aujeszky's disease from sow herds. Other herd-specific risk factors might be much more strongly related to the risk of a sow herd being ADV seropositive.     

Laboratory diagnosis of foot-and-mouth disease and swine vesicular disease in the years 1962-1988 in Greece]

During 26 years (1962-1988) 499 samples from FMD-suspicious cases were examined in Greece. These materials came from 348 (70%) cattle, 95 (19%) pigs and 56 (11%) sheep and goats. The cattle with 197 (72.4%) positive cases seems to play the most important roll in FMD. The different isolated virus types belonged in 60 cases to type A, in 187 to type O, in 14 to type C, in 6 to type SAT 1 and in 2 cases to type ASIA 1, respectively. SVD was isolated in 3 cases from the same area and at the same time. Most samples have been examined by means of CF, cell culture, unweaned mice or by a combined way of these assays. From 363 samples have examined: A) 148 by CF, B) 32 by CF and cell culture, C) 64 by CF and baby mice D) 80 by CF, cell culture baby mice E) 8 by cell culture, F) 18 in cell culture and baby mice and G) 13 by baby mice. Form these samples were found positive in the case A) 74 (50%), E) 3 (38%) and none in case G. On the other hand, the correlation of the positive samples in combined assays were in case B) 9:21, C) 9:1, D) 8:22:16 and the case F) 3:2 respectively. The D case shows that CF detected less positive cases than the cell culture did. For a reliable labor diagnosis of FMD every sample must be examined by more than one method.     

African swine fever in Mozambique: review, risk factors and considerations for control

African swine fever (ASF) is the most important disease that constrains pig production in Mozambique. Until 1994 it was apparently restricted to the central and northern provinces, but since 1994 outbreaks have been experienced throughout the country. ASF causes severe economic losses both in the small commercial sector and among the large numbers of small-scale producers in the family sector in rural and peri-urban areas. The history of ASF in Mozambique since its first confirmation in 1960 is briefly reviewed, recent outbreaks are reported, and the available information on the virus genotypes that have been responsible for some of the outbreaks is presented. Epidemiological factors that contribute to ASF outbreaks and strategies for limiting the negative effects of the disease in the different pig farming sectors in Mozambique, including raising farmer and community awareness, are discussed.     

Electron microscopic virus diagnosis in dogs, cats, calves, swine and foals in the year 1989

During 1989 fecal and gut samples of 598 dogs, 189 cats, 496 calves, 100 pigs and 66 foals with diarrhoea were investigated for virus by electron microscopy. In samples of dogs and cats Parvovirus was detected in 18.5% and 8.5% of the samples, respectively; Coronavirus was found in 14.9% and in 16.4% of the specimens. In samples of calves Coronavirus dominated with a detection rate of 37.5%, followed by Rotavirus with 10.7% and not clearly identifiable particles resembling Coronavirus (4.2%). In 7.1% of the specimens Rotavirus as well as Coronavirus was found. In 33% of specimens from piglets Coronavirus was detected. 10.6% of the faeces from foals contained Coronavirus-like particles. Between 1987 and 1989 the detection rate of Parvovirus in faeces from dogs and cats decreased from 24.2% to 18.6% and from 17.5% to 8.5%. Coronaviruses in calves, dogs and cats increased from 22.9% to 37.5%, from 5.6% to 14.9% and from 8.2% to 16.4% of the samples investigated.     

臭氧在非洲猪瘟防控上的合理利用

非洲猪瘟病毒抵抗力强、危害严重,臭氧须合理利用,才能发挥其在猪场非洲猪瘟防控消毒中的相应效果。     

Analysis and evaluation of mortality losses of the 2001 African swine fever outbreak,Ibadan, Nigeria

The mortality losses of pigs of various age groups affected by the 2001 African swine fever outbreak in Ibadan Nigeria were analyzed and evaluated. Thirty one thousand nine hundred and sixteen (31,916) pigs on three hundred and six (306) farms reported by the Pig Farmers Association of Nigeria and the State Ministry of Agriculture and Natural Resources were involved. Gross mortality was ninety one percent (91%), while age group mortality ranged from 75.9% (growers), 83.1% (weaners), 91.2% (finishers) and 99.8% (piglets); to 100.0% in gilts, sow and boars. Losses were estimated to worth nine hundred and forty one thousand, four hundred and ninety one dollars, sixty seven cents (US $941,491.67). Highest financial loss was from sows (29.5% of total loss), followed by gilts (16.6%), finishers (15.2%), weaners (10.7%), boars (10.6%), growers (10.6%) and piglets (8.2%). Average mortality loss per farm of $3076.77 was of great financial and socioeconomic consequences for a developing country like Nigeria with a low Gross Domestic Product figures. In conclusion, the need to immediately revisit and take recommended actions on the 1998 Report of the FAO Consultancy Mission to Nigeria on Control and Eradication of an Outbreak of African swine fever in Western Nigeria is stressed.     

饲料添加剂在非洲猪瘟防控中的作用

非洲猪瘟是一种烈性传染病,其暴发给全球养猪业带来了巨大的损失。至今尚未研发成功相应的疫苗。文章主要探讨了新型添加剂中草药饲料添加剂、微生态制剂对于猪只非特殊免疫力的调节以及对防控非洲猪瘟所起的作用。