Prevalence of bluetongue virus antibodies in sheep in central Ethiopia

Competitive ELISA was applied to detect antibodies against bluetongue virus in sheep sera collected from different agro-climatic areas in Ethiopia. A total of 90 serum samples were tested and 42 (46.67%) were positive for bluetongue virus antibodies. A prevalence rate ranging from 9.67% for sheep sampled in the highland to 92.85% for sheep sampled in the lowland was recorded. The prevalence correlated with the probable distribution of the Culicoides vector. This is the first report indicating the presence of bluetongue virus infection in animals from Ethiopia.     

Preparation and properties of a crude extract toxic to guinea-pigs from Pachystigma pygmaeum, a plant causing heart failure in ruminants

Pachystigma pygmaeum is a rubiaceous plant which causes heart failure after ingestion by ruminants. Isolation or characterization of a toxic entity has hitherto been unsuccessful. Extraction of the plant material with water or organic solvents gave poor yields of toxicity in guinea-pigs because of some unusual properties of the toxic entity. We present a method whereby liberation of a toxic entity from the plant material was achieved by fermentation with baker's yeast to give a crude extract with sufficient yield of toxicity for use in further isolation work.     

The inability of a South African Babesia bovis vaccine strain to infect Boophilus microplus

A strain of Babesia bovis that had been attenuated by rapid syringe passage through a series of 23 splenectomized calves was unable to infect its vector Boophilus microplus. An attempt to transmit the attenuated Australian Babesia bigemina G strain with a South African strain of B. microplus was likewise unsuccessful. The epidemiological implication of these observations in terms of babesiosis control is discussed.     

The persistence of colostral Anaplasma antibodies and incidence of in utero transmission of Anaplasma infections in calves under laboratory conditions

Twenty-six calves, born from 25 Anaplasma-infected, intact and splenectomized cows, from a herd kept under strict tick-free laboratory conditions, were monitored for the presence of Anaplasma antibodies, using the rapid card agglutination test. Serum was collected at birth, weekly for 12 weeks, and then monthly for approximately 6 months. Specific antibodies passively acquired could be detected in calf sera for an average period of 8 weeks after birth. Calves that remained positive for longer than 12 weeks were suspected of having contracted in utero infections. Infection of the calves was confirmed by splenectomy. It was concluded that 4 calves in Group I contracted in utero infections. Two of the dams were chronically infected, whilst the other 2 underwent acute primary reactions during the 1st and 2nd trimesters of gestation, respectively. Subsequently all calves born from infected cows in this tick-free herd were serologically screened before being splenectomized at an average age of 8 months. Out of 50 cows, 8 in utero infected calves were identified serologically and this finding was confirmed through splenectomy or subinoculation of blood. Both Anaplasma centrale and Anaplasma marginale were carried transplacentally. Splenectomized and intact cows, chronically infected or undergoing primary reactions during the 1st, 2nd or 3rd trimester of gestation, produced infected calves. A 15,6% incidence of in utero transmitted infections were observed amongst 77 calves under these conditions. None of the 13 splenectomized cows, undergoing primary A. centrale infections during gestation, aborted. Clinical signs of disease were not observed in any of the 12 in utero infected calves prior to splenectomy. The implications of these findings are discussed.     

Rapid fluorescence detection of in situ hybridization with biotinylated bovine herpesvirus-1 DNA probes

The use of biotinylated DNA hybridization probes for clinical detection of bovine herpesvirus-1 was investigated. Biotinylated DNA hybridization probes were prepared from bovine herpesvirus-1 DNA purified from infected cell cultures. The viral DNA was nick translated in the presence of biotin-dUTP with DNA polymerase to incorporate biotin into the newly synthesized strand. The probe was tested for specificity in in situ hybridization assays with bovine herpesvirus-1 DNA. Hybridization was detected using avidin-fluorescein single sandwich systems and an avidin-globulin with anti-globulin-fluorescein double sandwich system. Hybridization was detected by specific fluorescence of infected cells. Fluorescence was present only in bovine herpesvirus-1-infected cell culture and not in noninfected cell culture or cell cultures infected with several other viruses. The assay was performed in 6 hr.     

A column purification procedure for the removal of leucocytes from parasite-infected bovine blood

A cellulose column procedure is described which removes white cells from bovine blood infected with Babesia and Anaplasma. The efficiency of this method was confirmed by the absence of white blood cell DNA in lysates from column-filtered infected as well as non-infected blood.     

Pathogenesis of viral infections

The article considers factors that influence pathogenesis, initiation of infection, dissemination of virus within a host, lytic viral infections, viral immunosuppression, viral immunopathology, and viral oncogenesis.     

Genetic analysis of feline caliciviruses associated with a hemorrhagic-like disease.

Feline calicivirus (FCV) is 1 of the most common causes of upper respiratory tract disease in cats. Other disease syndromes associated with FCV infection have been reported. Recently, calicivirus infection associated with a hemorrhagic-like disease leading to significant mortality in cats has been reported. The clinical signs are similar to those observed with the calicivirus of rabbit hemorrhagic disease. This study characterized 2 FCV isolates associated with hemorrhagic-like disease. Nucleotide sequencing of the complete genome has been done for these 2 isolates as well as for 4 additional isolates representing other disease syndromes. Previously reported sequence data for the entire genome of classical FCV (6 isolates) and a portion of the capsid gene for hemorrhagic-like FCV (3 isolates), isolated in different regions of United States were used in the genetic analysis. Sequence data were used to determine relationships among the isolates and any correlation with phenotype. Nucleotide sequence comparisons of the entire genome and individual open reading frames revealed high homology among all isolates. Data suggest that the virulence may have genetic determinants on the basis of phylogenetic clustering of the isolates associated with hemorrhagic-like disease.     

VP2‐segment Sequence Analysis of Some Isolates of Bluetongue Virus Recovered in the Mediterranean Basin During the 1998–2003 Outbreak

The complete nucleotide sequences of the VP2 segments of bluetongue virus (BTV) isolates recovered from Italy, Greece and Israel, from 1998 to 2003, were determined. Phylogenetic analysis of these sequences, those from related viruses and the South African vaccine strains, were used to determine the probable geographic origin of BTV incursions into Italy. Results indicated that viruses from each of the four serotypes isolated in Italy (2, 4, 9 and 16) possibly had a different origin. Analysis of the bluetongue virus serotype 2 (BTV‐2) isolates gave evidence that this serotype probably moved from Tunisia. BTV‐4 results showed probable incursion from the southwest and not from Greece or Israel. BTV‐9 isolates clearly have an eastern origin (most probably Greece), whereas BTV‐16 isolates are indistinguishable from the BTV‐16 live attenuated vaccine strain. The phylogenetic findings were supported by polyacrylamide gel electrophoresis (PAGE) analysis of the complete amplified genome of each isolate except for BTV‐16 Italian field isolate, which showed a slightly different PAGE profile. A combination of the complete VP2 sequencing and PAGE analysis of complete genomes, allowed not only phylogenetic analysis, but also vaccine detection and assessment of reassortment events.     

Validation of synthetic peptide enzyme immunoassays in differentiating two subgroups of ruminant respiratory syncytial virus.

Subgroup-specific peptide-based enzyme immunoassays from each respective G-glycoprotein of the ovine and the bovine respiratory syncytial virus (RSV) were developed to detect RSV-specific IgG responses in cattle. Antigenic peptides from the respective G-glycoprotein were identified from the extracellular central hydrophobic region (amino acids 158-189) located between 2 mucin-rich regions. These antigenic peptides identified by epitope mapping from each G-glycoprotein were synthesized and used to develop the subgroup-specific enzyme immunoassays. The negative cutoff for each enzyme immunoassay was established as the mean optical density of indirect immunofluorescent antibody-negative bovine sera plus 3 SDs. The sensitivity (82.9%) and specificity (100%) of the bovine enzyme immunoassay and the specificity (95.8%) of the ovine enzyme immunoassay were determined by comparison with indirect immunofluorescence (used as the "gold standard"). The negative and positive predictive values were calculated for each assay. The presence of serum antibody to ovine RSV in cattle implies that this virus infects cattle and may contribute to the pathogenesis of bovine respiratory disease.