Bluetongue virus in South America: overview of viruses, vectors, surveillance and unique features.

Since the first published report of bluetongue (BT) virus (BTV) infection in South America from Brazil in 1978, serological surveys have determined that the infection is widespread in sheep, cattle, goats and water buffalo but generally without clinical signs. Only four outbreaks of BT disease have been reported so far in Brazil. Brazil and Argentina are the only countries in South America where BTV serotypes 12 and 4 have been isolated, respectively. By serology, serotypes 4, 6, 14, 17, 19 and 20 were detected in Brazil, 12, 14 and 17 in Colombia, 14 and 17 in Guyana and 6, 14 and 17 in Suriname. Culicoides insignis is the predominant vector in the area, but C. pusillus could also be a BTV vector. The virus has not yet been isolated from the vector in the region.

Incidence and isolation of bluetongue virus infection in cattle of the Santo Tomé Department, Corrientes Province, Argentina.

Sentinel herds were monitored for the detection of bluetongue (BT)-specific antibodies and virus over two periods, namely: June 1999 to August 2000 and September 2000 to April 2001. Herds were located in Santo Tomé (Herds 1 and 2) where BTV activity was known to occur. From June 1999 to August 2000, the cumulative incidence (CI) of bluetongue virus (BTV) infection was 0% and 35% in Herds 1 and 2, respectively. In the second period, the CI of BTV infection was 10% and 97% in Herds 1 and 2, respectively. The virus was isolated from red blood cells of animals that seroconverted and was identified as serotype 4. Averages of the monthly maximal temperatures were always above 19 degrees C. However, averages of the monthly median temperatures were below 19 degrees C and averages of the monthly minimal temperatures were below 15 degrees C from May 2000 to August 2000. There was no viral activity detected at that time. Culicoides insignis was identified as the predominant potential vector species (99%) trapped near sentinel herds. Although clinical disease has never been reported in Argentina, viral activity was detected and the virus has been isolated in sentinel herds.

[Contamination of bovine fetal serum with bovine viral diarrhea virus]. / Contaminación del suero fetal bovino con virus de la diarrea viral bovina.

Fetal bovine serum (FBS) used in cell culture may be contaminated with viruses, among them bovine viral diarrhea virus (BVDV) affecting the production of biological reagents and the results of diagnosis. The filtration process used in the preparation of commercial FBS abrogates most viral agents that may be present in raw FBS, but BVDV may pass through the filters because of its small size and its pleomorphism. While detection of bovine herpes virus-1 and parainfluenza-3 (PI-3) is determined by observation of the cytopathic effect, and also by hemadsorption in the case of PI-3, the most frequently isolated BVDV is non cytopathic, and infects cells without morphological alterations, inducing problems that arise after several cell generations. Batches of raw and processed FBS were analyzed. Frequencies of BVDV detection in raw serum in Argentina were similar to those published for USA. By conventional methods for BVDV detection, only 2 of 20 commercial batches of FBS had BVDV. Using cell cultures maintained with high concentrations of the serum under study for at least 2 weeks, with detection of viral antigen by indirect immunofluorescence, the percentage of BVDV detection was 80%. This method shows that most lots of commercial FBS contain BVDV. RT-PCR allows faster detection of the viral genome, but it must be validated, as it does not show viral replication. To eliminate the problem of BVDV contamination in FBS, only gamma irradiated FBS is used in our laboratory.

Contaminación del suero fetal bovino con virus de la diarrea viral bovina / Contamination of bovine fetal serum with bovine viral diarrhea virus

Fetal bovine serum (FBS) used in cell culture may be contaminated with viruses, among them bovine viral diarrhea virus (BVDV) affecting the production of biological reagents and the results of diagnosis. The filtration process used in the preparation of commercial FBS abrogates most viral agents that may be present in raw FBS, but BVDV may pass through the filters because of its small size and its pleomorphism. While detection of bovine herpes virus-1 and parainfluenza-3 (PI-3) is determined by observation of the cytopathic effect, and also by hemadsorption in the case of PI-3, the most frequently isolated BVDV is non cytopathic, and infects cells without morphological alterations, inducing problems that arise after several cell generations. Batches of raw and processed FBS were analyzed. Frequencies of BVDV detection in raw serum in Argentina were similar to those published for USA. By conventional methods for BVDV detection, only 2 of 20 commercial batches of FBS had BVDV. Using cell cultures maintained with high concentrations of the serum under study for at least 2 weeks, with detection of viral antigen by indirect immunofluorescence, the percentage of BVDV detection was 80. This method shows that most lots of commercial FBS contain BVDV. RT-PCR allows faster detection of the viral genome, but it must be validated, as it does not show viral replication. To eliminate the problem of BVDV contamination in FBS, only gamma irradiated FBS is used in our laboratory.

Contaminación del suero fetal bovino con virus de la diarrea viral bovina / Contamination of bovine fetal serum with bovine viral diarrhea virus

Fetal bovine serum (FBS) used in cell culture may be contaminated with viruses, among them bovine viral diarrhea virus (BVDV) affecting the production of biological reagents and the results of diagnosis. The filtration process used in the preparation of commercial FBS abrogates most viral agents that may be present in raw FBS, but BVDV may pass through the filters because of its small size and its pleomorphism. While detection of bovine herpes virus-1 and parainfluenza-3 (PI-3) is determined by observation of the cytopathic effect, and also by hemadsorption in the case of PI-3, the most frequently isolated BVDV is non cytopathic, and infects cells without morphological alterations, inducing problems that arise after several cell generations. Batches of raw and processed FBS were analyzed. Frequencies of BVDV detection in raw serum in Argentina were similar to those published for USA. By conventional methods for BVDV detection, only 2 of 20 commercial batches of FBS had BVDV. Using cell cultures maintained with high concentrations of the serum under study for at least 2 weeks, with detection of viral antigen by indirect immunofluorescence, the percentage of BVDV detection was 80. This method shows that most lots of commercial FBS contain BVDV. RT-PCR allows faster detection of the viral genome, but it must be validated, as it does not show viral replication. To eliminate the problem of BVDV contamination in FBS, only gamma irradiated FBS is used in our laboratory.(AU)

Contaminación del suero fetal bovino con virus de la diarrea viral bovina. / [Contamination of bovine fetal serum with bovine viral diarrhea virus]

Fetal bovine serum (FBS) used in cell culture may be contaminated with viruses, among them bovine viral diarrhea virus (BVDV) affecting the production of biological reagents and the results of diagnosis. The filtration process used in the preparation of commercial FBS abrogates most viral agents that may be present in raw FBS, but BVDV may pass through the filters because of its small size and its pleomorphism. While detection of bovine herpes virus-1 and parainfluenza-3 (PI-3) is determined by observation of the cytopathic effect, and also by hemadsorption in the case of PI-3, the most frequently isolated BVDV is non cytopathic, and infects cells without morphological alterations, inducing problems that arise after several cell generations. Batches of raw and processed FBS were analyzed. Frequencies of BVDV detection in raw serum in Argentina were similar to those published for USA. By conventional methods for BVDV detection, only 2 of 20 commercial batches of FBS had BVDV. Using cell cultures maintained with high concentrations of the serum under study for at least 2 weeks, with detection of viral antigen by indirect immunofluorescence, the percentage of BVDV detection was 80

. This method shows that most lots of commercial FBS contain BVDV. RT-PCR allows faster detection of the viral genome, but it must be validated, as it does not show viral replication. To eliminate the problem of BVDV contamination in FBS, only gamma irradiated FBS is used in our laboratory.

Foetal infections with bovine viral diarrhoea virus in Argentina.

The frequency of isolation of bovine viral diarrhoea virus (BVDV) from primary tissue cultures and organs from bovine foetuses was studied between 1992 and 1994. Around 25% of primary tissue cultures were BVDV positive. Primary testis cultures were inoculated with homogenates of spleen, kidney, lung and liver from 52 foetuses. Cells were passaged twice and BVDV antigen investigated by indirect immunofluorescence. Non-cytopathic BVDV was detected in at least one organ in 11/52 foetuses (21.2%): 6/10 spleens, 4/7 kidneys, 7/9 lungs and 3/5 livers. Cytopathic BVDV was detected in lung and kidney from two foetuses. Since only gamma-irradiated sera are used in the laboratory and only inactivated BVDV vaccines are applied in Argentina, it was concluded that these isolations represented field infections. In addition to the 11 virus positive foetuses, two foetuses were positive for BVDV antibodies, which suggested a 25% prevalence of infection. These results stress the need for disease control on a herd basis and the requirement for biological reagents of bovine origin for the detection of BVDV.

Viral antibodies in bovine fetuses in Argentina.

In order to establish the prevalence of viral infections of the bovine fetus in Argentina, a serological survey for antibodies against viral agents currently affecting cattle in this country was conducted. Antibodies against foot-and-mouth disease virus (FMDV), bovine herpesvirus-1 (BHV-1), bovine leukaemia virus (BLV), bovine rotavirus (BRV), bovine coronavirus (BCV), bovine viral diarrhoea virus (BVDV) and parainfluenza-3 (PI-3) were investigated in a total of 315 fetal serum samples. Conventional techniques were used: indirect immunofluorescence (FMDV, BHV-1, BVDV and BCV), radial immunodiffusion (BLV), ELISA (BRV) and haemagglutination inhibition (PI-3). Antibodies against BHV-1, BVDV and PI-3 were detected in samples from fetuses in the second and third trimester of gestation, with a prevalence of 1.21 per cent (two of 165), 2.03 per cent (four of 197) and 5.08 per cent (nine of 177), respectively. Either antibodies or non-antibody factors able to bind to BRV and BCV antigens were detected with a prevalence of 2.44 per cent (five of 205) and 4.54 per cent (five of 110), respectively. In addition, 14.68 per cent of non-specific inhibitors of PI-3 mediated haemagglutination were found. No seropositives against FMDV and BLV were detected.

Incidence, epidemiology and control of bovine virus diarrhoea virus in South America.

Outbreaks of diarrhoea associated with mucosal erosions of the mouth, tongue and digestive tract, clinically diagnosed as bovine virus diarrhoea-mucosal disease (BVD-MD), have been reported in Argentina and Brazil since the 1960's. However, primary isolation of the virus of BVD-MD is fairly recent, occurring in 1974 for Brazil, 1984 for Argentina, 1985 for Chile and 1981 for Colombia. In Argentina both cytopathogenic and non-cytopathogenic BVD virus strains have been identified. Elsewhere in South America this differentiation does not seem to have been carried out. Serological surveys have confirmed the existence of BVD virus infection in six countries (Argentina, Brazil, Chile, Colombia, Peru and Uruguay), with an incidence rate ranging between 37 and 77% of cattle in the areas surveyed. Diarrhoea in calves between 3 and 18 months of age, often associated with mucosal erosions, has been the most commonly observed syndrome. In some cases an upper respiratory tract involvement was described. In one epizootic, in the Sabana de Bogota plateau of Colombia, reproductive failure associated with abortions or birth of weak calves was the main clinical syndrome.

[Infectious bovine rhinotracheitis (VHB-1). II. Physico-chemical properties of strain L-114]. / Rinotraqueítis infecciosa bovina (VHB-1). II: Propiedades físico-químicas de la cepa L-114.

The thermal stability, density gradient and morphological features of a recently isolated L-114 strain of infectious bovine rhinotracheitis virus were determined. Morphology studies showed an enveloped virus with 200 nm of total diameter, a core diameter of 90 nm and an icosaedral-type structure; purified preparations contained both complete and empty viral particles. More than 90% of the infectivity was lost after 15 hours at 37 degrees C; at 56 degrees C, inactivation was much faster, with a 3 log titer reduction, in 24 minutes. Density gradient studies in cesium chloride, carried out with virus concentrated on sucrose gradient, gave an estimated density of 1.25 g/ml for the purified virus, which fits with light herpesviruses.

Rinotraqueitis infecciosa bovina (VHB-1). II: Propiedades fisico-quimicas de la cepa L-114. / Infectious bovine rhinotracheitis (VHB-1). II.Physico-chemical properties of the L-114 strain

Se determino la estabilidad termica, densidad de flotacion y morfologia de la cepa L-114 de virus de la rinotraqueitis infecciosa bovina, aislada recientemente en el pais. La morfologia correspondio a un virus con envoltura, de 200 mm de diametro total y 90 mm de diametro del "core". La estructura de este ultimo fue de tipo icosaedrica, observandose particulas vacias y completas en la preparaciones purificadas de virus. A 37o C, cepa L-114 perdio mas del 90% de su infectividad en 15 hs. y a 56o C se inactivo muy rapidamente, perdiendo 3 log en 24 minutos. La densidad de flotacion en cloruro de cesio, luego de su concentracion por sedimentacion a traves de sacarosa al 47% (p/v), indica que el virus purificado tiene una densidad estimada de 1,25 g/ml, correspondiente a los virus herpes denominados livianos

Rinotraqueítis infecciosa bovina (VHB-1). II: Propiedades físico-químicas de la cepa L-114. / [Infectious bovine rhinotracheitis (VHB-1). II. Physico-chemical properties of strain L-114]

The thermal stability, density gradient and morphological features of a recently isolated L-114 strain of infectious bovine rhinotracheitis virus were determined. Morphology studies showed an enveloped virus with 200 nm of total diameter, a core diameter of 90 nm and an icosaedral-type structure; purified preparations contained both complete and empty viral particles. More than 90

of the infectivity was lost after 15 hours at 37 degrees C; at 56 degrees C, inactivation was much faster, with a 3 log titer reduction, in 24 minutes. Density gradient studies in cesium chloride, carried out with virus concentrated on sucrose gradient, gave an estimated density of 1.25 g/ml for the purified virus, which fits with light herpesviruses.

Rinotraqueitis infecciosa bovina (VHB-1). II: Propiedades fisico-quimicas de la cepa L-114. / Infectious bovine rhinotracheitis (VHB-1). II.Physico-chemical properties of the L-114 strain

Se determino la estabilidad termica, densidad de flotacion y morfologia de la cepa L-114 de virus de la rinotraqueitis infecciosa bovina, aislada recientemente en el pais. La morfologia correspondio a un virus con envoltura, de 200 mm de diametro total y 90 mm de diametro del "core". La estructura de este ultimo fue de tipo icosaedrica, observandose particulas vacias y completas en la preparaciones purificadas de virus. A 37o C, cepa L-114 perdio mas del 90% de su infectividad en 15 hs. y a 56o C se inactivo muy rapidamente, perdiendo 3 log en 24 minutos. La densidad de flotacion en cloruro de cesio, luego de su concentracion por sedimentacion a traves de sacarosa al 47% (p/v), indica que el virus purificado tiene una densidad estimada de 1,25 g/ml, correspondiente a los virus herpes denominados livianos