Factors associated with improved haemagglutination by African horse sickness virus

Concentrated cell culture fluids of African horse sickness virus were shown to agglutinate erythrocytes from cattle, horses, sheep, goats, guinea pigs, rabbits, and poultry at 4°C, room temperature, and 37°C. The titres obtained were dependent on pH and NaCl molarity of the diluent, optimal titres being obtained at pH 7.5 and 0.6 M NaCl. The HA inhibiting antibodies to two AHS viruses were proven to be type specific.     

African horse sickness in Zimbabwe: 1972 to 1981

Summary During the nine years from October 1972 to September 1981 African horse sickness (AHS) virus was isolated from 23 suspected cases of the disease in Zimbabwe and complement fixation antibody titres indicative of recent infection were detected in a further 49 horses. The 23 isolations belonged to seven of the nine known serotypes of AHS virus. In response to a questionnaire in 1980 the owners of 20% (1,654/8,000) of the horses in Zimbabwe indicated that they had recorded 207 cases of clinically diagnosed AHS with 107 deaths from 1975 to 1980. Fifty-six cases with 50 deaths had occurred in foals and many of the other cases occurred in horses which had been vaccinated. It was concluded that the immunity induced by vaccine and maternal immunity warranted further investigation.

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Peste Equina Africana En Zimbabwe: 1972–1981

Resumen Se aisló virus de peste equina africana de 23 casos sospechosos de la enfermedad en Zimbabwe, detectándose infecciones recientes mediante fijación de complemento, en 49 caballos más. Los 23 aislamientos pertenecían a siete de los nueve serotipos conocidos de la enfermedad. Veinte por ciento de propietarios de equinos que respondieron a una encuesta formulada en 1980 (1654/8000), indicaron que habían reconocido 207 casos de la enfermedad, diagnosticados clínicamente, entre 1975 y 1980. Cincuenta y seis casos con 50 muertes ocurrieron en potros y los demás en caballos que habían sido vacunados. Se concluye, que se necesitan más investigaciones en cuanto a la inmunidad materna y aquella inducida por la vacuna ahora en al mercado.

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La Peste Equine Au Zimbabwe: 1972 À 1981

Résumé Durant les neuf ans allant d'octobre 1972 à septembre 1981, le virus de la peste équine a été isolé à partir de 23 cas de maladie suspectée au Zimbabwé, et par la fixation du complément, des titres indicateurs d'une infection récente ont été détectés chez 49 autres chevaux. Les souches isolées appartenant à sept des neuf sérotypes connus du virus. En réponse à un questionnaire de 1980, les propriètaires de 20% (1654/8000) des chevaux du Zimbabwé ont indiqué qu'ils ont recontré 207 cas de peste équine diagnostiquée cliniquement, avec 107 mortalités entre 1975 et 1980. Cinquante-cinq cas, dont 50 mortaliltés, se sont produits chez des poulains, et beaucoup des autres cas ont été observés chez des chevaux qui avaient été vaccinés. Il est conclu que l'immunité engendrée par le vaccin, ainsi que l'immunité maternelle, nécessite d'autres recherches.

     

Epizootiology and vectors of African horse sickness virus

African horse sickness (AHS) virus causes a non-contagious, infectious, arthropod-borne disease of equines and is enzootic in sub-Saharan Africa. The major vectors are species of Culicoides but mosquitoes and ticks may be involved. Periodically the virus makes excurisons beyond its enzootic zones but until recently has not been able to maintain itself outside these areas for more than 2–3 consecutive years. This is probably due to a number of factors including the absence of a long term vertebrate reservoir, the prevalence and seasonal incidence of the vectors and the efficiency of control measures. The recent AHS epizootics in Iberia and North Africa seem to have established a new pattern in AHS virus persistence. This is probably linked to the continuous presence of adult C. imicola in the area. Culicoides imicola is basically an Afro-Asiatic insect and prefers warm climates. Therefore its continuous adult presence in parts of Iberia may be due to some recent moderation of the climate in these areas.     

Adaptive strategies of African horse sickness virus to facilitate vector transmission

African horse sickness virus (AHSV) is an orbivirus that is usually transmitted between its equid hosts by adult Culicoides midges. In this article, we review the ways in which AHSV may have adapted to this mode of transmission. The AHSV particle can be modified by the pH or proteolytic enzymes of its immediate environment, altering its ability to infect different cell types. The degree of pathogenesis in the host and vector may also represent adaptations maximising the likelihood of successful vectorial transmission. However, speculation upon several adaptations for vectorial transmission is based upon research on related viruses such as bluetongue virus (BTV), and further direct studies of AHSV are required in order to improve our understanding of this important virus.     

Systemic and local antibody responses after experimental infection with Actinobacillus pleuropneumoniae in piglets with passive or active immunity

The objectives of the present study was to describe different dynamics of humoral immune responses to experimental infection in piglets of different stages of infection and immunity. Two groups of piglets originating from non-immune (group 1) and immune (group 2) sows at the age of 3 weeks were subdivided as follows: a half of each group of piglets was exposed to a low-dose infection with Actinobacillus pleuropneumoniae (APP) strain 9. At the age of 8 weeks, all four groups of piglets were challenged with a high infection dose of APP of the same strain. Isotype characterization of the specific antibodies in sera and in bronchoalveolar lavage fluids (BALF) to a lipopolysaccharide was carried out, besides monitoring clinical signs and post-mortem examinations. A typical primary immune response was observed in specific antibody-free piglets infected with a challenge infection. Colostrum-derived immunoglobulin-G (IgG) antibodies persisted in sera and BALF of piglets up to the age of 8 weeks. However, they did not prevent induction of specific-primary antibody response, either in 8 or 4 weeks of age, when levels of specific colostrum-derived antibodies were still high. It was demonstrated by the increase of specific IgM antibodies in sera. The infection induced an increase in the levels of IgA antibodies in BALF regardless the severity of infection and presence of specific colostrum-derived antibodies. The specific antibodies of IgG isotype increased only in BALF from piglets without colostrum-derived antibodies.     

Equine grass sickness is associated with low antibody levels to Clostridium botulinum: a matched case-control study

REASONS FOR PERFORMING STUDY: Equine grass sickness is a high mortality disease which, despite many years of investigation, is of unknown aetiology. Recent findings indicating that the disease is associated with Clostridium botulinum require support from an epidemiological study that recognises and controls for potential confounders, e.g. age, time of year and premises. HYPOTHESIS: EGS is associated with low antibody levels to C. botulinum antigens. METHODS: A matched case-control study was conducted. Data were collected from 66 histologically confirmed cases of EGS and 132 premises-matched control horses. The probability of EGS in horses was modelled using conditional logistic regression. RESULTS: EGS was significantly associated (age-adjusted P < 0.005) with low antibody levels to each of 3 clostridial antigens; C. botulinum type C and C. novyi type A surface antigens and a C. botulinum type C toxin complex toxoid. These serological risk factors for EGS remained highly significant when entered into multivariable models. This study also identified new horse-level risk factors for EGS; feeding hay or haylage was associated with a decreased risk of disease, change of feed type or quantity during the 14 days prior to disease was associated with increased risk, and the use of an ivermectin anthelmintic at both the ultimate and penultimate treatments was also associated with a significantly increased risk of EGS. CONCLUSIONS: This study provides strong support for the role of C. botulinum in the aetiology of EGS and identifies managemental risk factors for the disease. POTENTIAL RELEVANCE: Increasing anticlostridial antibody levels by vaccination and appropriate managemental interventions may decrease the risk of EGS occurring.     

A review of African horse sickness and its implications for Ireland

ABSTRACT: African horse sickness is an economically highly important non-contagious but infectious Orbivirus disease that is transmitted by various species of Culicoides midges. The equids most severely affected by the virus are horses, ponies, and European donkeys; mules are somewhat less susceptible, and African donkeys and zebra are refractory to the devastating consequences of infection. In recent years, Bluetongue virus, an Orbivirus similar to African horse sickness, which also utilises Culicoides spp. as its vector, has drastically increased its range into previously unaffected regions in northern Europe, utilising indigenous vector species, and causing widespread economic damage to the agricultural sector. Considering these events, the current review outlines the history of African horse sickness, including information concerning virus structure, transmission, viraemia, overwintering ability, and the potential implications that an outbreak would have for Ireland. While the current risk for the introduction of African horse sickness to Ireland is considered at worst 'very low', it is important to note that prior to the 2006 outbreak of Bluetongue in northern Europe, both diseases were considered to be of equal risk to the United Kingdom ('medium-risk'). It is therefore likely that any outbreak of this disease would have serious socio-economic consequences for Ireland due to the high density of vulnerable equids and the prevalence of Culicoides species, potentially capable of vectoring the virus.     

非洲马瘟病毒VP7蛋白原核表达及间接ELISA抗体检测方法的建立

为建立非洲马瘟病毒(African Horse Sickness Virus,AHSV)的血清学诊断方法,本研究构建了非洲马瘟病毒VP7蛋白的原核表达质粒pET-32a-VP7,诱导表达后使用Ni-NTA对可溶性VP7蛋白亲和纯化,以重组VP7蛋白作为包被抗原,优化建立检测血清抗体的间接ELISA方法,并对该方法进行敏感性、特异型和重复性验证,表明该方法的检测效果良好。本研究为非洲马瘟的血清检测试剂盒的开发提供的相关参考。     

Role of neutralising antibody in passive immunity to bluetongue infection

A group of sheep inoculated with serum obtained from sheep which had recovered from bluetongue virus type 3 infection were protected from challenge with the homologous virus type but not from heterologous challenge. Twin lambs which had received colostrum containing virus antibodies were shown to be only partially protected against homologous challenge. A monoclonal antibody directed against the type-determining protein of the virus was also shown to give partial protection against challenge. From this series of experiments it was concluded that antibody has a significant role in protection from bluetongue but that the outcome of challenge will depend on several interacting factors.     

Rapid and sensitive detection of African horse sickness virus by real-time PCR

A highly sensitive and specific TaqMan-MGB real-time RT-PCR assay has been developed and standardised for the detection of African horse sickness virus (AHSV). Primers and MGB probe specific for AHSV were selected within a highly conserved region of genome segment 7. The robustness and general application of the diagnostic method were verified by the detection of 12 AHSV isolates from all of the nine serotypes. The analytical sensitivity ranged from 0.001 to 0.15 TCID₅₀ per reaction, depending on the viral serotype. Real-time PCR performance was preliminarily assessed by analysing a panel of field equine samples. The same primer pair was used to standardise a conventional RT-PCR as an affordable, useful and simple alternative method in laboratories without access to real-time PCR instruments. The two techniques present novel tools to improve the molecular diagnosis of African horse sickness (AHS).     

Re-emergence of bluetongue, African horse sickness, and other Orbivirus diseases

Arthropod-transmitted viruses (Arboviruses) are important causes of disease in humans and animals, and it is proposed that climate change will increase the distribution and severity of arboviral diseases. Orbiviruses are the cause of important and apparently emerging arboviral diseases of livestock, including bluetongue virus (BTV), African horse sickness virus (AHSV), equine encephalosis virus (EEV), and epizootic hemorrhagic disease virus (EHDV) that are all transmitted by haematophagous Culicoides insects. Recent changes in the global distribution and nature of BTV infection have been especially dramatic, with spread of multiple serotypes of the virus throughout extensive portions of Europe and invasion of the south-eastern USA with previously exotic virus serotypes. Although climate change has been incriminated in the emergence of BTV infection of ungulates, the precise role of anthropogenic factors and the like is less certain. Similarly, although there have been somewhat less dramatic recent alterations in the distribution of EHDV, AHSV, and EEV, it is not yet clear what the future holds in terms of these diseases, nor of other potentially important but poorly characterized Orbiviruses such as Peruvian horse sickness virus.