First Report of an Outbreak of African Horsesickness Virus Serotype 2 in the Northern Hemisphere

A case of a rapidly fatal disease in polo horses caused by African horsesickness (AHS) virus serotype 2 is described. The pattern of polo tournaments, environmental/management conditions (moist and warm), as well as probable importation strategies with no regard for import control and quarantine, favored introduction and spread of the virus. The outbreak, which involved a large number of horses, was characterized by severe respiratory distress, fever, supraorbital edema, and death. This is the first time a widespread epidemic of AHS has been reported in Nigeria and this is the first report of AHSV serotype 2 in the northern hemisphere. In addition, we amplified the complete genome of the virus using RNA extracted from clotted blood. This report indicates that AHS is expanding its geographical territory northwards and assuming a new microbial ecology.     

The Transfer of Resistance to the Russian Wheat Aphid from Triticum monococcum L. to Common Wheat

Two Triticum monococcum accessions were found to be highly resistant to the Russian wheat aphid. An attempt was made to transfer the resistance to common wheat through direct hybridization or by using bridge species. In each of the four crossing strategies tried, a gradual loss of resistance occurred as hybrids with higher ploidy levels were obtained. It appeared that the level of resistance observed was directly proportional to the ratio of the Triticum monococcum genome relative to other genomes. This would indicate suppression of the resistance gene(s) by the added genomes or dilution of its product(s) by those of homoeoloci. The degree of protection afforded by the gene(s) at the hexaploid level may prove to be small. Plants suspected to be homozygous for the resistance gene(s) were identified; however, further backcrossing to common wheat will be required to improve their agronomic types and meiotic regularities.     

后备小母牛限饲的可行性

<正>因为要在佛罗里达反刍动物营养讨论会上做一个题为《小母牛限饲方案》的报告,笔者查阅了大量的相关文献,对此有了较深的认识,本文是该报告的梗概。过去的40年里,生长小母牛的饲养方案经历了多个阶段     

Detection of bovine viral diarrhea virus by spot hybridization with probes prepared from cloned cDNA sequences

A cytopathic strain of bovine viral diarrhea virus (BVDV) was purified from infected cell culture fluids by isopycnic density-gradient centrifugation. Genomic RNA was extracted and tailed with adenine residues at the 3' end with poly-A polymerase. Double-stranded complementary DNA (cDNA) was synthesized, using the poly-A-tailed RNA as a template and oligo-dT as a primer, and then cloned into the pUC9 plasmid. Virus-specific cDNA sequences, varying in length from 0.5 to 2.5 kilobases (kb), were obtained. One BVDV-specific sequence of cloned cDNA, 1.1 kb in length and with an internal Pst I restriction endonuclease cleavage site, was selected for use as a probe. The cloned cDNA insert was removed from the plasmid either with or without flanking plasmid sequences and labeled with 32P-nucleotides by nick translation for use as hybridization probes for BVDV. The performance of probes of smaller fragments of the insert was compared to that of the intact sequence in hybridization assays. In addition, 2 methods of specimen preparation were compared to establish optimum parameters for hybridization. The hybridization assay was 10-100 times more sensitive than infectivity assays for BVDV in infected cell cultures. Freezing of specimens reduced by 10-fold the sensitivity of hybridization for BVDV target sequences. The probes prepared from the cloned cDNA hybridized with all cytopathic and noncytopathic BVDV strains tested but not with uninfected cell cultures, cellular ribosomal RNA, bovine coronavirus, bluetongue virus, or bovine adenovirus 3. Probes prepared with native plasmid DNA did not hybridize with BVDV or uninfected cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bovine herpesvirus-1 infection of cattle: kinetics of antibody formation after intranasal exposure and abortion induced by the virus

The kinetics of antibody formation in Holstein heifers after primary and secondary intranasal inoculation of bovine herpesvirus-1 (BHV-1) and after BHV-1-induced abortion was determined. Sera were fractionated by gel filtration and ion-exchange chromatography. The antibody activity within serum immunoglobulin (Ig) isotypes was assessed, using a plaque-reduction neutralization assay. The primary immune response to BHV-1 infection was characterized by the appearance of IgM and IgG antibodies in serum by postinoculation day (PID) 7. Maximal IgG antibody activity occurred at PID 35 in nonpregnant heifers and at PID 14 in pregnant heifers. Thereafter, IgG antibody activity declined slowly in both groups of heifers. Maximal IgM antibody activity occurred at PID 14 in both groups of heifers and declined rapidly thereafter. The IgG antibody activity during primary immune responses was restricted to the IgG1 subclass. Secondary responses were characterized by anamnestic IgG antibody responses. Antibody activity was present within the IgG1 and IgG2 subclasses during secondary immune responses, but the increase in antibody activity during this period was primarily in the IgG2 subclass. Secondary IgM antibody formation was elicited by abortion induced by the intra-amniotic inoculation of BHV-1, but not by reexposure by the intranasal route. Abortion occurred in 1 heifer 28 days after intranasal BHV-1 inoculation. Abortion in this heifer was not associated with a secondary antibody response. The nature of BHV-1 antigenic exposure in the bovine determined the relative distribution of anti-BHV-1 antibody activity in serum IgM, IgG1, and IgG2. The formation of IgM antibody, with the exception of secondary intranasal exposure, indicated recent BHV-1 antigenic exposure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of canine parvovirus on erythroid progenitors in phenylhydrazine-induced regenerative hemolytic anemia in dogs

The effects of canine parvovirus (CPV) infection in dogs with hemolytic anemia was compared with the clinical effects of human parvovirus-induced aplastic anemia in human beings with chronic regenerative anemias. Phenylhydrazine was used to induce a transient, severe, hemolytic anemia in dogs to evaluate the effects of CPV infection on rapidly dividing bone marrow precursors. Erythrocyte colony-forming unit bone marrow cultures and cytologic examination of bone marrow were used to determine the effects of CPV infection on erythroid bone marrow precursors. The induced hemolytic anemia regenerated rapidly and although the bone marrow was infected, it was determined that CPV infection did not induce a detectable decrease in erythroid progenitors in dogs with severe hemolytic anemia.     

An attempt to improve the immunization of sheep against heart-water by using different combinations of 3 stocks of Cowdria ruminantium

Neither sheep immune to the Ball 3, the Kwanyanga or the Mara stocks of Cowdria ruminantium nor those immunized with combinations of these 3 stocks were protected against challenge with the Mali stock. Against challenge with the Welgevonden stock, however, immunization with each of the 3 combinations and with single stocks effected a protective immunity.