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....     

Neutralization of African swine fever virus by sera from African swine fever-resistant pigs

Sera from African swine fever-resistant pigs with infection-inhibitory activity decreased virus replication in infected porcine buffy coat cultures. This same effect was observed even after virus was adsorbed. The infection-inhibition was not reversed by removing the immune serum from the assay cultures. Reduction of African swine fever virus replication by immune sera was demonstrated by fluorescent focus assay on MS cell line cultures. Virus-neutralization tests showed a persistent fraction of non-neutralized virus, which was not demonstrable by infection-inhibition tests. One hypothesis for explaining this difference is proposed.     

African swine fever among slaughter pigs in Mubende district, Uganda

Owing to frequent reports of suspected outbreaks and the presence of reservoir hosts and vectors (warthogs, bushpigs and O. moubata ticks), African swine fever (ASF) is believed to be an endemic disease in Uganda. There have, however, been very few studies carried out to confirm its existence in Uganda. This study was carried out to describe the prevalence of ASF based on pathologic lesions and analysis of serum samples from slaughtered pigs during a suspected outbreak in the Mubende district of Uganda. The study was based on visits to 22 slaughterhouses where individual pigs were randomly selected for a detailed ante-mortem and post-mortem inspections. Sera were also collected for laboratory analysis. A total of 997 pigs (53.7% male and 46.3% female) were examined for lesions suggestive of ASF and sero-positivity of sera for ASF antibodies. The sera were tested using enzyme-linked immunosorbent assay (ELISA) and positive samples were further confirmed with an immunoblot assay. The results showed that 3.8% (38/997) of the pigs examined had clinical signs and post-mortem lesions suggestive of ASF. Two of 997 (0.2%) sera analysed were positive for ASF antibodies. Of the sub-counties investigated, Bagezza (12%) and Kiyuni (11%) had the highest prevalence of lesions suggestive of ASF based on ante- and post-mortem examination results, while Mubende town council (1.7%) had the lowest. This study found a low number of pigs (3.8%) with lesions suggestive of ASF at slaughter and an even lower number of pigs (0.2%) that were seropositive at slaughter, however a significantly higher number of pigs were slaughtered during the outbreak as a strategy for farmers to avoid losses associated with mortality.     

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.     

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.     

Sanitary measures in piggeries,awareness, and risk factors of African swine fever in Benue State,Nigeria

The present study describes assessment of sanitary measures in piggeries of Benue State, Nigeria, to identify the risk factors of African swine fever. Questionnaires were distributed to 74 respondents consisting of piggery owners and attendants in different piggeries across 12 local government areas (LGAs) to collect data for this study. Sanitary measures in piggeries were observed to be generally very poor, though respondents admitted being aware of ASF. Piggeries located within 1-km radius of a slaughter slab (OR?=?9.2, 95% CI 3.0–28.8; p?<?0.0001) and piggeries near refuse dump sites (OR?=?3.0, 95% CI 1.0–9.5; p?<?0.05) showed higher chances of African swine fever virus (ASFV) infection, while piggeries where farm workers wear their work clothes outside of the piggery premises (OR?=?0.2, 95% CI 0.1–0.7; p?<?0.01) indicate less chances of infection but had a significantly associated p value thus were identified as potential risk factors. The study concluded that pigs in Benue State are still at risk of an ASF outbreak. Proper sanitary and hygienic practices are advocated and emphasized in piggeries, while routine surveillance for African swine fever virus antibodies in pigs in Benue State is strongly recommended to provide a reliable reference database to plan for the prevention of any devastating ASF outbreak.

     

Pathologic features of chronic pneumonia in pigs with experimentally induced African swine fever.

Chronic pneumonia developed in 14 pigs inoculated with an attenuated strain of African swine fever (ASF) virus. The pathogenesis of the pneumonia was as follows: (1) Interalveolar septums became thickened by accumulation of lymphocytes and monocytes; (2) lung developed focal areas of lymphocytes and macrophages; (3) necrosis began abruptly in these foci, beginning with the cells in the alveolar lumens, developing in centrifugal direction, and eventually affecting all structures in its path; (4) necrotic tissue became calcified; and (5) a mantle of mononuclear cells (including plasma cells) and fibrous tissue formed around the necrotic area. Viremia occurred in the 14 pigs at postinoculation day (PID) 14, and precipitating antibody was increased significantly at PID 58.     

应对非洲猪瘟疫情 保护种猪基本产能——对当前种猪产业的调研

<正>非洲猪瘟疫情对我国生猪产业的影响是深远的,究竟影响到什么程度,是我们春节期间调研的首选。通过对养猪场的访谈和种猪企业的交流与分析,深刻地认识到,非洲猪瘟对我国生猪产业的影响,远远超出了我们的想象。一、一个生猪养殖大户的起起落落河北省玉田县是生猪养殖大县,2017年生猪出栏110万头,鸦鸿桥镇生猪出栏量居该县之首,出栏20余万头。1986年,鸦鸿桥镇西牛各庄村张福胜从4头小仔猪起步,带领兄弟姐妹们养猪,经过20世纪90年代的起步     

Mechanism of thrombocytopenia in African swine fever

Pigs were inoculated with an African swine fever (ASF) isolate of moderate virulence, and the changes in the number of circulating blood platelets during infection were correlated with the appearance of antiviral antibody and fluctuations in total plasma hemolytic complement concentrations. Thrombocytopenia was detected by postinoculation days (PID) 7 and 8, and antiviral antibody was detected by PID 7, using an indirect immunofluorescence technique. The total hemolytic complement concentration was moderately and transiently decreased from PID 5 to 9, but was consistently low from PID 18 to 26. Pigs inoculated with an ASF virus isolate of greater virulence had a decrease in platelet counts on PID 6 and 7, and the total plasma hemolytic complement levels decreased in all pigs by PID 6 to 7. Antibody to ASF virus was not detected in pigs inoculated with the more virulent isolate. Pigs sensitized to ASF viral antigen with an inactivated-virus vaccine or by previous infection with ASF were challenge exposed. Sensitized pigs became clinically ill and thrombocytopenic by 24 to 72 hours earlier than did inoculated, nonsensitized pigs. Vaccinated pigs inoculated with homologous virus had lower blood virus concentrations than did nonvaccinated pigs. African swine fever virus-sensitized pigs inoculated with heterologous virus had a higher fatality rate than did nonsensitized pigs, and the pigs died peracutely, with only a few gross lesions in evidence. In vitro experiments demonstrated that ASF virus antigen induced platelet aggregation in platelet-rich plasma from recovered, nonviremic pigs. Viral antigen, antibody, or complement was not demonstrable on the surface of platelets from pigs inoculated with ASF virus isolate, by direct immunofluorescence testing.     

Diversity of African swine fever virus

An African swine fever virus is an heterogeneous population, consisting of clones having different biological characteristics in respect to hemadsorption, virulence, infectivity, plaque size, and antigenic determinants. The following observations were made: Nonhemadsorbing virus (NHV) have been segregated from field isolates from Haiti (HT-1) and a bone marrow- and buffy coat-passaged Portuguese isolate (L'60BM89BC1) and appear as a major, minor, or equal mixture with hemadsorbing viruses in the virus population. Biological characteristics of the virus inoculated into pigs often differed from viruses isolated later from the same pigs. Virulence and nonhemadsorbing characteristics of isolated clones were genetically stable. The lethal effect of 2 NHV clones of L'60BM89BC1 virus was dose-dependent; small doses of virus induced immunologic deaths or recoveries from the clinical disease in pigs, and large doses induced acute deaths. The NHV of Lisbon isolate of 1960 (L'60) and HT-1 isolate share the same antigenic determinants for inducing protection. Tengani isolate contained clones of distinctly different antigenic determinants, not shared by L'60 or HT-1 isolate that enabled it to overcome the protection induced by the other clones. Passaging of an African swine fever virus isolate in pigs or cell cultures may readily alter the proportions of the different clones in the population and thereby change its overall characteristics. A new virus population with atypical hemadsorption was found in HT-1 field isolate and L'60BM89BC1 virus.     

An immunohistochemical study of the tonsils in pigs with acute African swine fever virus infection

An immunohistochemical study of the tonsils was carried out to gain further insight in the pathogenesis of acute African swine fever (ASF). Twenty-one pigs were inoculated by intramuscular route with a highly virulent isolate of ASF virus and painlessly killed at 1-7dpi. Viral antigen was highly distributed in the tonsil from 3 to 4dpi and an increase in the number of monocyte-macrophages was very evident at the same days post inoculation. This phenomenon was observed together with an increase of the expression of proinflammatory cytokines (Tumour necrosis factor alpha and Interleukin-1 alpha) and the apoptosis of lymphocytes studied by the terminal deoxynucleotidyltransferase-mediated dUTP nick end labelling (TUNEL) technique and haemorrhages. With these results, we can conclude that the tonsil is suffering similar lesions than those observed in other lymphoid organs in acute African swine fever, even when the route of inoculation is the intramuscular and not oral-nasal.     

African swine fever and classical swine fever: a review of the pathogenesis

This paper describes major pathogenetic mechanisms of African and Classical Swine Fever virus infections. The interactions between both viruses and the monocyte-macrophage-system result in the release of mediator molecules, which are important for the further progression of the diseases. The causes of the thrombocytopenia and the mechanisms of the haemorrhages, which are characteristic in both infections, are described. Apoptotic cell death is regarded as the predominant cause of lymphopenia in both virus infections.