Yellow fever haemagglutination-inhibiting, neutralising and IgM antibodies in vaccinated and unvaccinated residents of Ibadan, Nigeria

A survey for yellow fever virus haemagglutination inhibiting (HI) and neutralising (N) and IgM antibodies was carried out in unvaccinated people in Ibadan and in those immunised with the yellow fever 17-D vaccine. A total of 207 people were tested for HI antibody to yellow fever and two other flaviviruses namely: Wesselsbron and Uganda S. viruses. Prevalence of HI antibody to each flavivirus antigen was as follows: Yellow fever 26%, Wesselsbron 18% and Uganda S 33%. Of the 207 people, 37 (18%) had yellow fever N antibody. There was a higher prevalence of N antibody to yellow fever virus in adults than children. Twenty-one people vaccinated with 17-D yellow fever vaccine donated post-vaccination sera; 10 (48%) had no prevaccination HI antibody, 7 (33%) had HI antibody to one flavivirus and 4 (19%) to two or more flaviviruses. Ninety percent of seronegative people and all those with prevaccination flavivirus antibodies developed HI or N antibody, following vaccination. A total of 58 unvaccinated people were tested for yellow fever IgM antibody by an enzyme linked immunosorbent assay, 2 (3%) were positive; suggesting that active yellow fever transmission was in progress at the time of survey.     

Towards a better understanding of Rift Valley fever epidemiology in the south-west of the Indian Ocean

Rift Valley fever virus (Phlebovirus, Bunyaviridae) is an arbovirus causing intermittent epizootics and sporadic epidemics primarily in East Africa. Infection causes severe and often fatal illness in young sheep, goats and cattle. Domestic animals and humans can be contaminated by close contact with infectious tissues or through mosquito infectious bites. Rift Valley fever virus was historically restricted to sub-Saharan countries. The probability of Rift Valley fever emerging in virgin areas is likely to be increasing. Its geographical range has extended over the past years. As a recent example, autochthonous cases of Rift Valley fever were recorded in 2007–2008 in Mayotte in the Indian Ocean. It has been proposed that a single infected animal that enters a naive country is sufficient to initiate a major outbreak before Rift Valley fever virus would ever be detected. Unless vaccines are available and widely used to limit its expansion, Rift Valley fever will continue to be a critical issue for human and animal health in the region of the Indian Ocean.     

Immunological reactions of Rift Valley fever virus strains from East and West Africa.

Three strains of Rift Valley fever virus, namely Nigerian (NIG), Smithburn's neurotropic (SNT), and Lunyo variant (LUN) were compared by complement fixation (CF), neutralisation (N), haemagglutination/haemagglutination-inhibition (HA/HI) and agar gel diffusion (AGD) tests. They showed reciprocal cross-reactivity in CF tests. In N tests, using immune sheep sera, there was reciprocal cross-neutralisation between the NIG and SNT strains, but not with the LUN strain, the antiserum of which neutralised both NIG and SNT antigens whereas the reverse was not the case. When hyperimmune mouse ascitic fluid was employed in N tests, there was cross-reactivity between the three strains. Both the NIG and SNT strains yielded haemagglutinins, but not the LUN strain. Furthermore, by the antibody absorption and AGD techniques, the NIG and SNT strains were found to be identical and distinct from the LUN variant strain. The techniques found most useful in distinguishing between the three strains were HA and AGD. Laboratory neuro-adaptation of the classical pantropic virus did not appear to affect its haemagglutination activity.     

Serological survey of Rift Valley fever in sheep on the Ivory Coast]

A serological survey of Rift Valley fever was carried out in sheep in C?te-d'Ivoire. Thousand and fifty one seras collected between 1988 and 1990 in the South of the country were tested for IgG and IgM by ELISA with two objectives: determining the incidence of the Rift Valley fever and analysing the role of this virus in reproductive failure and abortion. The incidence rate was 6.85%. No difference was found between the three different geographic areas nor between the three years of the survey. Antibody prevalence increased significantly with age. The Rift Valley fever must be considered as enzootic in C?te-d'Ivoire. A significant relationship was found between positivity and abortion in ewes. Thus, the economic impact of Rift Valley fever has to be studied. The presence of antibodies in young animals aged from 6 months to 1 year, showed a recent activity of the virus; a permanent epidemio-surveillance of the Rift Valley fever in C?te-d'Ivoire is needed, because of the potential risk for human population in contact with the animals.     

Specific antibody responses to Mycobacterium bovis in infected cattle analysed with six mycobacterial antigens in enzyme-linked immunosorbent assays

A total of 23 (15.3 per cent) of 150 cattle infected with Mycobacterium bovis and which had never been tuberculin tested showed specific antibody responses to M bovis. Their sera may be important keys to the identification of unique M bovis antigens for use in specific serodiagnostic tests. Assessment of specific and non-specific responses was done by screening sera in six indirect anti-IgG enzyme-linked immunosorbent assays using whole cell sonicates of M bovis and five members of the Mycobacterium avium-intracellulare-scrofulaceum complex as respective antigens. Sera from 16 infected cattle that had been tuberculin tested positive and nine uninfected cattle (never tuberculin tested) were also assayed for specific and non-specific responses. Three other findings emerged. First, 43 of the 150 infected animals (28.7 per cent) showed no antibody responses to any of the mycobacterial antigens used. Secondly, the cattle showing the highest antibody levels were associated with the greatest cross reactivity. Lastly, the results indicated that tuberculin injections may increase antibody responses to shared, rather than specific, M bovis antigens in infected cattle.     

Human adenovirus antibody in sera of normal and tumour-bearing dogs.

Serum specimens from 42 normal dogs and 42 with untreated malignant tumours were assayed for the presence of antibodies to human adenovirus types 5, 21 and 31 and to infectious canine hepatitis (ICH) virus. Radioimmunoassays using human adenovirus antigens showed that 71 per cent (30/42) of all dogs with tumours, but only 19 per cent (8/42) of all normal dogs, were positive for human adenovirus antibody. Canine sera reactive with antigens of one human adenovirus type in radioimmunoassays were also reactive with antigens of the other two types. Dogs bearing malignant lymphoma or squamous cell carcinoma tumours had higher levels of antibody against adenovirus type 5 antigens. Human adenovirus type 5 was neutralised by sera from four tumour-bearing and two normal dogs, while sera from two normal and five tumour-bearing dogs were positive in immunodiffusion tests with human adenovirus antigens. Levels of ICH antibody in sera of normal adult dogs and adult dogs with tumours were not markedly different when measured by radioimmunoassays. Likewise, sera from these two groups of dogs had similar ranges of ICH neutralising antibody titres. In contrast, levels of ICH antibody detected by the serological assays in sera from non-pet, non-vaccinated pups were either markedly low or absent. Possible explanations for the observed increased levels of human adenovirus antibody in sera of tumour-bearing canine pets are discussed.     

Use of two polysaccharide antigens in ELISA for the detection of antibodies to Echinococcus granulosus in sheep sera

Polysaccharide antigens were obtained from either the secretions produced during in vitro cultivation of Echinococcus granulosus protoscoleces or from mouse hydatid cyst membranes by phenol extraction. When either of these antigens was used in an enzyme-linked immunosorbent assay antibody activities were detected in sera from sheep infected 27 or more weeks earlier with at least 100 E granulosus eggs. These antibody responses were significantly higher (P less than 0.05) than those of sheep infected with Taenia hydatigena or T ovis and tested with the E granulosus antigens. Very high cross-reacting antibody responses in sera from sheep recently infected with T hydatigena were only detected with the protoscoleces secretions antigen. Neither antigen was sufficiently sensitive or specific for serodiagnostic use. However, when sera were first tested with one antigen and then with the other, and only sera that were positive in both tests were regarded as positive, the overall sensitivity and specificity of this two antigen method increased to about 80 per cent.     

Hydrops amnii in sheep associated with hydranencephaly and arthrogryposis with wesselsbron disease and rift valley fever viruses as aetiological agents.

During the 1974/75 lambing season numerous reports were received from various parts of the Republic of South Africa and South West Africa of severe abdominal distension in ewes after vaccination with the attenuated Rift Valley fever and/or attenuated Wesselsbron disease vaccine. The ewes were vaccinated at different stages of gestation in spite of recommendations to the contrary, the syndrome being especially obvious in ewes immunized with one or both of these vaccines during the first trimester of pregnancy. In some of the flocks hydrops amnii was recorded in as many as 15% of the ewes. Many of the ewes so affected showed a prolonged gestation of up to 6-7 months and, towards the end of gestation, were unable to rise or walk. They eventually died of ketosis, hypostatic pneumonia and complications due to dystocia. The foetuses examined were malformed and larger than normal with a mass of 3,6-6,7 kg. They usually showed arthrogryposis, brachygnathy inferior, hydranencephaly, hypoplasia or segmental aplasia of the spinal cord and neurogenic muscular atrophy. The amnion contained 8,0-18,0 1 of amniotic fluid, the endometrium was oedematous, and cystic tube-like dilatations, 1-10 mm in diameter, filled with a clear fluid, were scattered in the endometrium. No definite conclusions as to the aetiology of the syndrome could be drawn from serological tests performed on the ewes, lambs or foetuses. Preliminary experimental work confirmed previous observations that the attenuated Wesselsbron disease vaccine virus is responsible for this syndrome and that the wild-type virus is also implicated. In addition, the attenuated Rift Valley fever vaccine virus was found to the responsible for arthrogryposis and hydranencephaly without hydrops amnii and for micrencephaly and arthrogryposis associated with hydrops amnii in the ewe.     

Management of horses showing stereotypic behaviour, owner perception and the implications for welfare

A telephone survey was conducted of 100 racing stables, 100 riding schools and 100 competition establishments (8,427 horses in total) to determine what management practices were being applied to horses showing stereotypic behaviour, and to determine the underlying reasons for them by assessing the perceptions and opinions of the people working with the horses. The results indicated that horse owners are concerned about stereotypic behaviour, first, because it reduces the performance of the animal (31, 30 and 27 per cent of the owners of racing stables, riding schools and competition establishments respectively), secondly, because it has adverse clinical effects on the horse (52, 55 and 56 per cent), and thirdly, because it reduces the monetary value of the animal (45, 59 and 31 per cent). The belief that these behaviours are learnt or copied also affects the management of affected horses: they are not allowed on to the premises by 4, 32 and 17 per cent of owners of racing stables, riding schools and competition establishments, respectively; attempts are made to remove the causal factors of the stereotypy by 35, 43 and 36 per cent; the behaviours are physically prevented by 77, 67 and 79 per cent, and the affected horses are kept separate from other horses by 39, 30 and 48 per cent.     

Wesselsbron virus infection in West African Dwarf Sheep: Effect of pre-infection serum flavivirus antibodies on severity of disease

West African Dwarf Sheep inoculated sequentially with two flaviviruses: yellow fever and Dakar bat or West Nile and yellow fever viruses, developed neutralizing (N) and haemagglutination inhibiting (HI) antibodies to several flaviviruses; dengue type 1, dengue type 2, yellow fever, West Nile and Wesselsbron viruses. Experimental infection of these animals with the indigenous strain of Wesselsbron virus resulted in the modification of the clinical disease. The disease was reduced in severity and there was complete absence of, or marked reduction in the level and duration of circulating virus and fever. Seronegative animals infected with the same strain of Wesselsbron virus developed the classical disease characterized by a high fever, anorexia, leucopenia and a high level of viraemia. The absence of clinical reports of Wesselsbron disease and lack of other isolations of the virus from Nigeria could possibly be explained by the presence of the flavivirus group antibodies in domestic animal sera.     

Clinical and pathological studies in adult sheep and goats experimentally infected with Wesselsbron disease virus

The clinical symptoms and pathology in 33 adult sheep and 31 adult goats experimentally infected with Wesselsbron disease virus are described. There was moderate to severe hyperthermia in most animals, but no other clinical signs of disease or deaths were recorded. Eleven sheep and 6 goats were sacrificed for pathological studies at various stages during the febrile response. The macroscopic and microscopic lesions in these cases are described. Microscopic studies revealed that the liver was consistently affected and showed small foci of necrosis. These were sparsely distributed and associated with a marked localized Kupffer cell response ("retothelial nodules"). In addition, acidophilic bodies and small groups of necrotic hepatocytes were evident in some lobules. Apart from the hepatic lesions, mild to moderate pyknosis and karyorrhexis of lymphocytes were seen in the spleen and lymph nodes. This report also compares the microscopic lesions in the livers of adult sheep and goats with those of new-born lambs for Wesselsbron disease as well as with those reported for Rift Valley fever in adult sheep.     

A survey for haemagglutination-inhibiting antibody to West Nile virus in human and animal sera in Nigeria

A survey for West Nile Virus (WNV) haemagglutination-inhibition (HI) antibody was carried out in humans and domestic animals. Human sera were collected from Ibadan, while the animal sera were collected from both Ibadan and Maiduguri. Out of 304 human sera tested, 123 were positive (40%). There was a higher prevalence of HI antibody in adults than children. Sex distribution of positive sera showed that 37% of males and 43% of females had WNV HI antibody. There was no significant difference in the prevalence of HI antibody in both sexes. On the 123 WNV HI positive sera tested, 104 (85%) and 78 (75%) had yellow fever and Potiskum HI antibody respectively. Monotypic WNV virus reactions were frequently found in children while polytypic reactions were frequently found in adults. A total of 200 animal sera were examined, 50 camels, 50 goats, 49 cattle and 51 sheep. The highest prevalence of HI antibody was found in camels (26%), followed by sheep (20%). Percentage of positive sera in other species were: goat (18%) and cattle (6%). Of the 35 WNV HI positive animal sera, 26 and 20% reacted with Yellow fever and Potiskum virus antigens respectively.     

Epidemiological investigations of outbreaks of bovine ephemeral fever in Israel

In two epidemics of bovine ephemeral fever (BEF) in Israel, one in 1990 and one in 1999, the virus was probably carried by vectors transported by air currents across the Rift Valley and through the Red Sea trough. The disease broke out under optimal ecological conditions among vulnerable cattle populations and spread rapidly; it developed in the spring and summer and ended soon after the daily average ambient temperature fell below 16 degrees C in late autumn. The proportion of herds affected reached 78.4 and 97.7 per cent in 1990 and 1999, respectively. The highest rates of incidence, morbidity and mortality were recorded in dairy cattle herds in the Jordan Valley, the initial focus of the outbreaks, with a morbidity of 20 and 38.6 per cent in 1990 and 1999, respectively, and mortality among the affected animals of 2 and 8.6 per cent in 1990 and 1999, respectively. In 1991, the disease recurred sporadically in the central and southern regions of Israel in only three herds, but in 2000 the disease returned on an epidemic scale, and 85 per cent of herds were affected, with morbidity and mortality rates of 4-3 and 0-3 per cent, respectively. In the 1999 epidemic, the morbidity rate decreased from 38-6 per cent on average in the Jordan Valley to 12.8 per cent in the inner valleys and 5.3 per cent on the Mediterranean coastal plain, but the mortality rate increased from 8-6 per cent in the Jordan Valley to 14-3 per cent in the inner valleys, and to 28 per cent on the Mediterranean coastal plain, where the outbreak declined. An average of 2-7 per cent of the animals experienced a second attack of the disease two to six weeks later. The epidemic in 2000 was milder and shorter than that in 1999. All the cattle affected in both outbreaks were more than three months old. The vector(s) is not known for certain but the available evidence indicates that mosquitoes, and not Culicoides species, are the natural vectors of BEF virus in Israel.     

Neutralising antibody to herpesviruses dervied from wildebeest and hartebeest in wild animals in East Africa.

The sera of 728 game animals, collected in East Africa, were tested for neutralising antibody to a strain (WC11) of wildebeest herpesvirus, which is an important cause of malignant catarrhal fever of cattle. In addition, 290 of these sera were tested for neutralising activity against a closely related herpesvirus (K/30) from hartebeest (Alcelaphus sp.). Antibody was frequently present in three species of the subfamily Alcelaphinae (wildebest, hartebeest and topi) and one of the subfamily Hippotraginae (oryx). No activity was found in the sera of nine other species of four additional subfamilies. The proportion of hartebeest sera positive for WC11 virus (60 per cent) was not significantly different from that neutralising the K/30 isolate (77 per cent) and antibody titres against the two agents did not differ significantly. Of 62 topi sera 40 per cent neutralised WC11 virus, while all of three oryx sera were positive. It is suggested that the antibody detected in hartebeest, topi and oryx was induced by infection with viruses related to, but not identical with, the WC11 and K/30 strains. Some characteristics of the latter indicated that it was not the usual herpesvirus of hartebeest and may have been derived from wildebeest. It is proposed that the group of viruses involved should be provisionally designated as 'alcelaphine herpesviruses' in order to separate them from the rest of the 'bovid' herpesviruses, a name proposed by the Herpesvirus Sbucommittee of the International Committee on the Nomenclature of Viruses.     

Rift Valley fever virus(Bunyaviridae: Phlebovirus): an update on pathogenesis, molecular epidemiology, vectors, diagnostics and prevention

Rift Valley fever(RVF) virus is an arbovirus in the Bunyaviridae family that, from phylogenetic analysis, appears to have first emerged in the mid-19th century and was only identified at the beginning of the 1930's in the Rift Valley region of Kenya. Despite being an arbovirus with a relatively simple but temporally and geographically stable genome, this zoonotic virus has already demonstrated a real capacity for emerging in new territories, as exemplified by the outbreaks in Egypt (1977), Western Africa (1988) and the Arabian Peninsula (2000), or for re-emerging after long periods of silence as observed very recently in Kenya and South Africa. The presence of competent vectors in countries previously free of RVF, the high viral titres in viraemic animals and the global changes in climate, travel and trade all contribute to make this virus a threat that must not be neglected as the consequences of RVF are dramatic, both for human and animal health. In this review, we present the latest advances in RVF virus research. In spite of this renewed interest, aspects of the epidemiology of RVF virus are still not fully understood and safe, effective vaccines are still not freely available for protecting humans and livestock against the dramatic consequences of this virus.     

Cloning and expression of Rift Valley fever virus nucleocapsid (N) protein and evaluation of a N-protein based indirect ELISA for the detection of specific IgG and IgM antibodies in domestic ruminants

Serodiagnosis of Rift Valley fever (RVF) currently relies on the use of live or inactivated whole virus as antigens. The recombinant nucleocapsid (N) protein of RVF virus was tested for diagnostic applicability in an indirect enzyme-linked immunosorbent assay (I-ELISA), using sera from experimentally infected sheep (n=128), vaccinated sheep (n=240), and field-collected sera from sheep (n=251), goats (n=362) and cattle (n=100). The N-protein based I-ELISA performed at least as good as VN and HI tests. In goat the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the I-ELISA was 100% when using the anti-species IgG conjugate. Using protein G as a detection system, the D-Sn and D-Sp in goats were 99.4% and 99.5%, in sheep field sera both 100%, in cattle 100% and 98.3%, respectively. The I-ELISA based on recombinant N-protein has the potential to complement the traditional assays for serodiagnosis of RVF. Advantages of the N-protein are its safety, stability and cost-effectiveness in use and production.     

Enzyme-linked immunosorbent assay for detection of antibodies to Rift Valley fever virus in ovine and bovine sera

An enzyme-linked immunosorbent assay (ELISA) was developed for the rapid detection of antibodies to Rift Valley fever virus (RVFV) in ovine and bovine sera. Conditions to reduce nonspecific reactions were optimized. The ELISA results correlated with those of a plaque-reduction neutralization test, revealing 100% specificity and 90.7% sensitivity. In sera from sheep and cattle inoculated against RVFV, the hemagglutination-inhibition test in combination with the ELISA provided a better indication of response to killed RVFV vaccine than did either test alone.     

Comparison of competitive ELISA, indirect ELISA and standard AGID tests for detecting blue-tongue virus antibodies in cattle and sheep

The performances of a competitive enzyme-linked immunosorbent assay (ELISA) using a group specific monoclonal antibody against bluetongue virus, an indirect ELISA and the standard agar gel immunodiffusion (AGID) test were compared in the detection of serum antibody against bluetongue virus. Test sera consisted of 1300 bovine, 530 ovine and 160 carpine samples from bluetongue-free areas of Canada, 605 bovine and ovine field samples from the USA and Barbados and 464 samples from 79 cattle and sheep experimentally infected with 19 South African and five USA serotypes of bluetongue virus. The diagnostic specificity of the competitive ELISA, as determined for the bluetongue virus-free cattle sera was superior (99.92 per cent) to that of the indirect ELISA (99.85 per cent) and the AGID (99.0 per cent). The specificities of the competitive ELISA for sheep (99.63 per cent) and goats (100.0 per cent) sera were also higher than those of the AGID test. The performance of the ELISA tests was similar whether a gamma-ray-irradiated (2.0 Mrad) or a non-irradiated bluetongue virus antigen preparation was used. The competitive ELISA results for bovine field sera from endemic areas demonstrated a relatively low level of agreement (92.04 per cent) with AGID test results, with 9.7 per cent false negatives. The possible presence in these sera of antibody to cross-reacting antigens or to other orbiviruses, eg, epizootic haemorrhagic disease virus, which react in the AGID but not in the competitive ELISA may account for this lack of agreement.(ABSTRACT TRUNCATED AT 250 WORDS)     

Seroepidemiological studies on the detection of Q fever in sheep in middle Thuringia]

In a random samples test altogether 4337 sheep of varying ages from several herds of different sizes in the middle region of Thuringia were investigated with complement fixing test for the existence of Q fever. In 47.1 per cent of the tested herds and in 5 from 8 of the included districts Q fever reagents were provable. The serological detection quota of all tested sheep amounts to 1.11 per cent, but the percentage of serological reagents in mother-sheep was 1.36 per cent, in the female young sheep 1.04 per cent and in the lambs 0.74 per cent. The investigations of rams and sheep for slaughter were negative. Serological testing in 7 sheep showed a Q fever antibody persistence about 6 until 10 months. Increased animal concentration and adverse conditions led to an increase of the Q fever seroprevalence in the herds.     

裂谷热病毒Gn蛋白主要抗原区的串联表达和多克隆抗体制备

裂谷热(Rift Valley fever,RVF)是由裂谷热病毒(Rift Valley fever virus,RVFV)引起的一种烈性人兽共患传染病.RVFV囊膜蛋白Gn可诱导产生中和抗体,是RVFV检测方法和疫苗研究的重要抗原靶标.本研究通过分析蛋白抗原位点信息,构建包含Gn蛋白两个主要抗原区域的重组表达载体,...