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)     

Survey of the seroprevalence of brucellosis in ruminants in Kosovo

A cross-sectional survey of the seroprevalence of brucellosis in sheep, goats and cattle in Kosovo was made in January 2001. A total of 12,000 serum samples, from 7941 cattle, 3548 sheep and 511 goats, were screened using the Rose Bengal test. Doubtful and positive results were further tested with competitive and indirect ELISAS. The overall serological prevalences derived from the samples positive to all three tests, were 6.26 per cent (95 per cent confidence intervals [CI] 5.5 to 7.1 per cent) for sheep, 7.24 per cent (5.3 to 9.8 per cent) for goats and 0.58 per cent (0.43 to 0.77 per cent) for cattle. The survey covered 26 of the 29 municipalities and showed that brucellosis was widely but unevenly distributed throughout the province. Seropositive animals were found in 25 per cent (19 to 32 per cent) of 162 villages surveyed. The risk of cattle being infected on holdings where both cattle and sheep were kept was greater, with a risk ratio of 4.6 (2.2 to 9.6), than on holdings where only cattle were kept. Brucella melitensis probably predominates as the cause of brucellosis in ruminants in the province of Kosovo.     

Serological survey for antibodies against pestiviruses in sheep in Austria

The prevalence of antibodies to pestiviruses was investigated in 4931 sheep, in 377 flocks, in four federal states of Austria, by means of an indirect elisa that detected antibodies to Border disease virus (BDV) and bovine viral diarrhoea virus (BVDV). The mean flock prevalence was 62.9 per cent and the mean individual prevalence was 29.4 per cent. Comparative neutralisation studies on the elisa-positive samples with BVDV type 1 (BVDV-1), BVDV type 2 (BVDV-2) and BDV recorded 336 samples with higher titres (more than four times average) to BVDV-1, three samples with higher titres to BVDV-2 and 55 samples with higher titres to BDV. The other samples did not show clear differences in antibody titres against the strains of pestivirus tested because of cross-reactions. The seroprevalence of pestiviruses in sheep was significantly higher on farms with cattle. There were significant regional differences between the prevalences in flocks and individual sheep, the highest prevalences being in the region of Austria where communal alpine pasturing of sheep, goats and cattle is an important part of farming.     

Longitudinal fracture of the scapula in a dog

A survey was carried out at Kano abattoir in order to estimate the incidence of hydatidosis and cysticercosis in slaughtered livestock. Of the animal species examined, hydatid disease was found in sheep (11.4 per cent), goats (26.5 per cent), cattle (14.7 per cent) and camels (55.5 per cent). Cysticercus tenuicollis was found to be most prevalent in goats (34.2 per cent), followed by sheep (21.4 per cent) and cattle (0.1 per cent). Out of 4844 cattle examined, less than 2 per cent haboured Cysticercus bovis cysts; while Cysticercus ovis cysts were found in sheep (1 per cent) and goats (0.8 per cent).     

Bluetongue serotype 8 vaccine coverage in northern and south-eastern England in 2008

A postal survey of all registered cattle and sheep farmers in East Anglia was carried out from July 2008 to determine bluetongue virus serotype 8 (BTV-8) vaccine uptake in the region. The vaccine was available to farmers in this region from May 2008. The survey was repeated in Cumbria and Northumberland at the beginning of 2009. In these regions, the vaccine was not available until September 1, 2008. Holding-level vaccine uptake was estimated to be 85 per cent (95 per cent confidence interval [CI] 83 to 87 per cent, n=1623) in East Anglia and 36 per cent (95 per cent CI 32 to 40 per cent, n=633) in northern England. A telephone follow-up of non-responders reduced these estimates to 79 and 29 per cent in East Anglia and northern England, respectively. In both regions, vaccine coverage was higher in sheep than in cattle, with 92 per cent of sheep in East Anglia having been vaccinated. The proportion of holdings that had applied the vaccine or were intending to apply the vaccine in 2009 in the northern region was 51 per cent (95 per cent CI 47 to 54 per cent, n=664), with a further 37 per cent undecided at the time of response.     

Studies with bluetongue virus in Nigeria.

Using an agar gel diffusion test antibody evidence indicates that bluetongue virus is widely distributed in Nigeria and commonly infects cattle, sheep and goats. In a single dairy herd serological conversions were observed in both wet and dry seasons.     

Serological reactions in sheep and cattle experimentally infected with three Australian isolates of bluetongue virus

Serums from 103 sheep and 24 cattle experimentally infected with one of 3 serotypes of bluetongue virus isolated in Australia were tested for antibody to bluetongue virus in the serum neutralisation test and the agar gel diffusion precipitin test. Antibody to bluetongue virus was first detected by these tests 8 to 10 days after intravenous infection in 4 sheep that were bled daily for serum analysis. The agar gel diffusion test failed to detect antibody in 28% (29/103) of sheep which had seroconverted in the serum neutralisation test. A further 7% (7/103) of sheep serums were negative in both tests 14 to 22 d after infection. Both tests detected antibody to bluetongue virus in all cattle serums by 10 days after detection of viraemia. In comparison with the intravenous route of infection, extended prepatent periods for the commencement of viraemia resulting from intradermal, subcutaneous and intrauterine routes of infection in the cattle caused corresponding delays in the detection of antibody. For example, one cow that was infected by intrauterine inoculation did not become viraemic until 22 d after inoculation and antibody was not detected until 32 d after inoculation.     

Survey of the seroprevalence of brucellosis in ruminants in Tajikistan

A cross-sectional serological survey of the prevalence of brucellosis in ruminants in the Region of Republican Subordination and Khatlon oblasts (provinces) in Tajikistan was conducted in May 2003. Sera from 13,625 ruminants involving 3513 households in 172 kishlaks (villages) were collected and screened by the rose bengal test. Doubtful and positive results were further tested with competitive and indirect elisas. The overall serological prevalences (95 per cent confidence intervals [cis]) were 5.8 per cent (5.2 to 6.4 per cent) for sheep, 5.5 per cent (5.0 to 6.0 per cent) for goats and 2.1 per cent (1.0 to 3.2 per cent) for cattle. The results show that brucellosis was a common disease of ruminants that was widely but unevenly distributed throughout the two oblasts. Seropositive animals were found in 119 of the 172 kishlaks (69.2 per cent [95 per cent ci 61.9 to 75.6 per cent]) and 14.4 per cent (95 per cent ci 13.3 to 15.6 per cent) of the 3513 households. Evidence of infection was also found in cattle kept for milk production in urban kishlaks in two major cities and in state-owned dairy farms.     

The seasonal incidence of coccidia infections in trade cattle,sheep, and goats in Nigeria

Summary

A survey of coccidia infections in trade cattle, sheep, and goats was undertaken in Nigeria between April 1978 and March 1979.

Faecal examinations showed coccidia oocysts in 1,456 (56 per cent) of 2,600 calves, 832 (80 per cent) out of 1,040 sheep, and 468 (45 per cent) out of 1,040 goats. There were relatively few coccidia oocysts between October and March and peaks occurred in August and September. Nine species of Eimeria were identified in bovine faeces, and seven species in both sheep and goats.

Eimeria bovis and E. zurnii are predominant in cattle, whereas E. faurei and E. ninakohlyakimovae have the highest percentage occurrence in sheep and goats in Nigeria. The effects of seasonal influences on the abundance of coccidia oocysts among ruminants in Nigeria are stressed.     

Diagnostic performance of PCR and ELISA on blood and milk samples and serological survey for small ruminant lentiviruses in central Spain

The diagnostic performance of an ELISA for the detection of antibodies to the small ruminant lentiviruses (SRLVs) maedi-visna virus and caprine arthritis-encephalitis virus in milk and corresponding blood samples was evaluated in 50 sheep. The agreement between ELISA results in blood and milk was 90 per cent, and the κ value was 0.79. In addition, a serological survey in the central zone of Spain was performed using milk samples from 413 animals (250 sheep and 163 goats) from 12 flocks/herds. All flocks/herds had some animals that were positive for SRLV. Among the animals, 60.0 per cent of the sheep and 8.0 per cent of the goats tested were seropositive. Each sample was also tested using a PCR technique, which increased the percentage of positive animals detected. Using a combination of ELISA and PCR gave a total of 72.2 per cent of sheep and 28.8 per cent of goats positive for SRLV.     

Seroprevalence of malignant catarrhal fever-related gammaherpesviruses in domestic ruminants in Turkey

The prevalence of malignant catarrhal fever (MCF) virus infection in cattle, sheep and goat populations and also the prevalence of recovered and chronic MCF cases in north-western Turkey are reported. A total of 600 animals, 200 individuals of each species, located in four provinces were sampled between December 2003 and July 2005. A monoclonal antibody-based competitive inhibition (ci) ELISA were used to detect infection status of the animals. Detected antibody prevalence was 97.5%, 96.0% and 15.0% in sheep, goats and cattle, respectively. These results showed that MCF related gammaherpesvirus infections are common in north-western Turkey. There was no significant difference between prevalences detected in sheep and goats, as well as various breeds of these species. There was also no significant difference among locations. Results of this study show that sheep and goats may equally be important in the epidemiology of MCF in Turkey. Seropositivity against MCF agents among cattle was 15.0%. The results indicate that MCF infections may be maintained in intensively managed cattle herds having no close contact with small ruminants.     

Epizootiologic study of bluetongue: virologic and serologic results

Heparinized blood and serum samples were obtained from 1,295 ruminants in herds or flocks with bluetongue virus (BTV) infection in 4 western states. Submissions were from herds or flocks with clinical bluetongue (BT), as well as from animals on premises with no history of BT disease. Insects, including Culicoides variipennis, were collected in areas enzootic for BT disease. Viral isolations were in 10-day-old embryonating chicken eggs that were then adapted to Vero cells for serotyping. Sera were tested from group-specific antibody to BTV by the micro agar gel precipitin (AGP) test. Viral isolations were from cattle (81), sheep (122), goats (9), antelope (2), and C varipennis (5). There were 7 isolates of serotype 120, 114 of serotype 11, 42 of serotype 13, and 56 of serotype 17. In herds or flocks from which BTV was isolated, 51% of cattle, 56% of sheep, 21% of goats, and 52% of antelope had AGP antibodies. Virus was isolated from 43% of the cattle and 23% of the sheep that had no demonstrable evidence of AGP antibodies. Viral isolations were seasonal, occurring from August until December. Approximately 30% of the herds or flocks from which virus was isolated had more than one serotype of virus causing infection.     

EPIZOOTIOLOGY OF BLUETONGUE: THE SITUATION IN THE UNITED STATES OF AMERICA

Bluetongue was first reported in the United States in 1948 in sheep in Texas. The virus has now been isolated from sheep in 19 States. When the disease first occurs in a flock, the morbidity may reach 50 to 75% and mortality 20 to 50%. In subsequent years, the morbidity may be only 1 to 2% with very few deaths. Difference in breed susceptibility has not been observed. Natural bluetongue infection has not been observed in Angora or dairy goats. Bluetongue virus was first isolated from cattle, in Oregon, in 1959. The virus has now been isolated from cattle in 13 States. In cattle, the disease is usually inapparent but can cause mild to severe clinical disease and neonatal losses. Natural clinical bluetongue has also been reported in bighorn sheep, exotic ruminants in a zoo, mule deer, and white-tailed deer. Serological evidence of exposure to the virus has also been found in other species of ruminants in the wild. Inoculation of virulent bluetongue virus, vaccine virus, or natural disease can cause congenital deformities and neonatal losses in calves, lambs, and white-tailed deer fawns. Culicoides is considered the important insect vector of bluetongue. The virus has also been isolated from sheep keds and cattle lice. U.S. field strains of the virus fit into four serologic groups. No cross reactions were found between bluetongue and epizootic haemorrhagic disease of deer viruses. Cattle are considered significant virus reservoirs. It is necessary to use washed erythrocytes, rather than whole blood, and to inoculate susceptible sheep, rather than embryonated chicken eggs, to detect longer-term viraemia in cattle.     

Chiral behaviour of the metabolite albendazole sulphoxide in sheep, goats and cattle

Three sheep, three goats and three cattle were dosed orally with 5.0, 7.5 and 10 mg albendazole kg-1 bodyweight, respectively. Blood samples were taken at intervals for 48 hours after administration. The enantiomeric ratio of the metabolite albendazole sulphoxide (SO.ABZ) was determined by liquid chromatography on chiral stationary phases. At To, the plasma concentration ratio (+)SO.ABZ/(-)SO.ABZ was estimated at 3.0 in sheep, 1.5 in goats and 4.0 in cattle. The proportion of the (+) enantiomer then increased linearly as a function of time during the course of the kinetics. In comparison to the area under the curve for total SO.ABZ, the (+) enantiomer represented 86 per cent in sheep, 80 per cent in goats and 91 per cent in cattle. The specific behaviour of the two enantiomers is probably the result of the enantioselectivity of the flavine adenosine dinucleotide and cytochrome P450 dependent enzymatic systems which are involved in the sulphoxidation and the sulphonation of ABZ.     

A SEROLOGICAL SURVEY FOR BLUETONGUE VIRUS ANTIBODY IN WESTERN AUSTRALIA

A serological survey was carried out to detect specific (serotype 20) and a group bluetongue virus antibody in cattle and sheep serums collected in Western Australia during the period January 1 1978 to June 30 1979. Of 18,849 cattle serums examined by the gel diffusion precipitin test (GDPT), 9.7% were positive and 6.1% gave doubtful results. All 1949 sheep serums tested were negative. Precipitin antibody was demonstrated in 22.5% of serums from Kimberley cattle and 3.6% of cattle serums from the Northwest. Serums collected from cattle in the South were consistently negative in GDPT. When 915 serums that reacted in the GDPT were further tested by the complement fixation test (CFT), 164 were positive. The percentage of CFT positive serums increased as the GDPT reaction became stronger. 2467 serums collected from cattle in Kimberley and Northwest areas and tested by the CFT, 175 (7.1%) were positive. These 175 positive serums were also examined by GDPT and 164 doubtful or positive reactions were obtained. The virus neutralisation (VNT) using serotype 20 virus was carried out on 3804 serums, including all serums that reacted in the GDPT, and 57 were positive. When the VNT positive serums were examined in the other 2 tests, 47 serums were either positive or doubtful in the GDPT and 8 were positive in the CFT. The presence of bluetongue virus group antibody in cattle serums closely followed the suggested distribution pattern of Culicoides brevitarsis but specific serotype 20 neutralising antibody was limited to cattle serums from stations situated north of latitude 17 degrees S in an area of mean annual rainfall higher than 700 mm.     

Serological survey of ruminants in some Caribbean and South American countries for type-specific antibody to bluetongue and epizootic haemorrhagic disease viruses

The results of a serological survey of ruminant livestock in some countries of the Caribbean and South America for type-specific antibody to bluetongue virus are reported. Using the microneutralisation test with the international serotypes 1 to 22 of bluetongue virus, antibodies to several types were detected. Analysis of the data indicated that in 1981-82 bluetongue virus types 6, 14 and 17, or viruses closely related to them, were infecting ruminants in this region of the world. Antibody to the related virus of epizootic haemorrhagic disease (serotype 1) was also detected in cattle. The difficulty in interpreting the epidemiological significance of data generated by a serological survey of this kind is discussed.     

An outbreak of bluetongue in sheep in the Sudan

An outbreak of bluetongue and the first isolation of the virus in the Sudan are reported. The disease occurred in sheep stressed by walking for five days when biting arthropods were prevalent. Estimates of the morbidity and mortality rates ranged from about 30 per cent and 2 per cent respectively in adult sheep to around 80 per cent and 100 per cent respectively in lambs. The virus was isolated by the inoculation of suckling mice and embryonated eggs with whole blood from febrile sheep. In a gel precipitation test it reacted with specific antiserum to type 10 BT8 strain. No other agent was isolated. Given the relatively mild nature of bluetongue in indigenous sheep, it is believed that the long walking stress coupled with exposure to sunlight might have aggravated the severity of the disease in this particular outbreak.     

THE EPIZOOTIOLOGY OF BLUETONGUE: THE AFRICAN SITUATION

Bluetongue virus is transmitted biologically by various species of Culicoides, notably C. pallidipennis and C. variipennis. Factors such as rainfall, temperature and relative altitude, which influence the breeding of the insect vectors also govern the incidence and distribution of the disease. The host range of bluetongue virus includes sheep, cattle, goats and various antelopes. Many other, as yet unidentified hosts could perhaps harbour the virus and influence the epizootiology of the disease. The close relationship between C. pallidipennis and cattle is indicated and the efficient mechanism for virus maintenance which this relationship constitutes is emphasised. It is further postulated that sheep are not essential for the continued survival of bluetongue virus, but merely function as accidental or indicator hosts.     

Seasonal variation of Oestrus ovis-specific antibodies in sheep and goats mixed flocks in Greece

The aim of this survey was to investigate the year-round epidemiological patterns of Oestrus ovis ELISA sero-prevalence in sheep and goats kept together under the same husbandry system in an endemic area of Greece. Twenty-five adult female sheep and 25 adult female goats, coming from a large mixed flock, were randomly selected, eartaged and monthly blood sampled during 1 year period (November 1998-October 1999). Serological prevalence in sheep was 100% all around the year. Mean intensities of specific O. ovis antibodies follow a seasonal evolution with higher mean titers between March and July than in winter. In contrast, the serological prevalences in goats were low specially in winter months (from October to January). No significant difference were noticed in goats antibody levels during the year period. The possible reasons of this difference of O. ovis sero-prevalence between sheep and goats are discussed.     

Susceptibility of Sudanese sheep to a bluetongue virus isolated from apparently healthy cattle in the Sudan

This study intends to clarify the role of apparently healthy cattle as a reservoir of bluetongue (BT) virus to sheep in the Sudan. It confirms earlier work and establishes that cattle can harbour bluetongue virus to which sheep are susceptible in the country. Experimental transmission of BT virus between the two species suggests that the best indicator to determine viraemia in apparently healthy cattle is to inoculate susceptible sheep with suspected cattle virus. The condition of the viraemia and the virus survival in the field are discussed.