The isolation and identification of further antigenic types of African horsesickness virus

Two new strains of horsesickness virus were isolated m suckling mice by the intracerebral route. These strains were identified as horsesickness by:- (a) Demonstration of fixation of complement by the group specific complement fixation test. (b) Non-inactivation by sodium desoxycholate and diethyl ether under standard conditions. (c) Preliminary screen serum virus neutralisation tests. Detailed serum virus cross neutralisation tests showed that these virus strains belong to two new antigenic types, which have been designated Groups 8 and 9. The two strains were isolated from widely separated geographical regions and are regarded as the prototypes of the two new groups which have been shown to include other strains of virus. The significance of the finding is discussed in relation of control of horsesickness by mass immunisation.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Observations on the occurrence of African horsesickness amongst immunised horses

During the course of an epizootic of African horsesickness it was possible to establish that:- (1) strains of virus apparently homologous with components of the polyvalent vaccine could be reisolated from clinically affected equines previously immunised; (2) infection by a specific immunological type of virus could be correlated with an absence of homologous antibody in the reacting animal; (3) animals failed to develop specific antibodies to certain components of the polyvalent vaccine in spite of repeated immunisation.The articles have been scanned in colour with a HP scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to final presentation PDF-Format

A preliminary antigenic classification of strains of bluetongue virus

As a preliminary investigation the existence of 12 distinct antigenic types of bluetongue virus was established. Where the facilities are available, the methods employed provide a rapid and accurate procedure for the antigenic identification of field specimens.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Multiplication of an attenuated RVII strain (type SATI2) of foot-and-mouth disease virus in sheep

A duplicate sample of the RV 11 vaccine used in the field against the SAT1 epizootic in South West Africa in 1960-1961 retained its infectivity after storage for three years at -20° C. When inoculated intramuscularly into sheep 15 to 18 months old, it stimulated an antibody response. The site of multiplication of the modified virus appeared to be the muscle tissue into which the vaccine was inoculated. A viraemia was detected in a few sheep three to four days after vaccination, but no other clinical signs or macroscopic lesions were observed on post mortem. Attempts to induce involvement of the central nervous system by simultaneous intracerebral inoculation of starch, or by intranasal or intraspinal inoculation of the vaccine diluted hundredfold, were unsuccessful. No evidence of abnormal behaviour was detected over a 15 week period of observation.The journals have been scanned in colour with a HP 5590 scanner; 600 dpi. Adobe Acrobat v.11 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Molecular hybridization studies on the relationships between different serotypes of bluetongue virus and on the difference between the virulent and attenuated strains of the same serotype

Isolates of ³H-labelled messenger RNA of a number of different bluetongue virus serotypes were hybridized with saturating amounts of denatured ³²P-labelled double-stranded RNA of different serotypes. These cross-hybridization products were then analysed by polyacrylamide gel electrophoresis. The results indicate relatively large differences between the various serotypes. Only a few of the genome segments in the different serotypes were completely homologous. Each of the cross- hybridization patterns obtained using the genome of Serotype 10 and any one of the other serotypes was unique and characteristic for the strain under investigation. The patterns furthermore clearly indicated different degrees of homology between the genomes of the different serotypes. The immunological specificity of the serotypes appears to be determined mainly by the second genome segment of the virus while genome segment six could be of secondary importance. These results were supported by a study of the cross-hybridization patterns between different isolates of Serotype 4. Cross-hybridization experiments between virulent and attenuated strains of the same serotype also indicated small differences. In all the serotypes investigated the process of attenuation involved changes in genome segments two and six. This result would tend to implicate the same genome segments in the determination of both the immunological specificity and the virulence of the virus.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Clinical foot-and-mouth disease in the African buffalo (Syncerus caffer)

The articles have been scanned in colour with a HP Scanjet 5590;300dpi. adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Foot-and-mouth disease in the African elephant (Loxodonta africana)

A strain of SAT 2 foot-and-mouth disease virus which was experimentally inoculated into the epidermis of the tongues of captive African elephants produced vesicular lesions at the site of inoculation. After a short period of viraemia, secondary lesions developed in the mouth and on the feet giving rise to extensive tissue damage and the separation of the soles. In spite of close contact there was no spread of the disease to other elephants and by conventional sampling techniques no carrier virus could be demonstrated. The neutralizing antibody response was of a low order and this finding together with the observations made during the course of the experimental disease are discussed in relation to the possible role of the elephant in the epizootiology of foot-and-mouth disease in Africa.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

The application of improved techniques to the identification of strains of bluetongue virus

Previously the isolation and identification of strains of bluetongue virus has been tedious, so that the introduction of techniques to shorten the delay was considered highly desirable. Neutralization tests were conducted on the principle of the inhibition of plaque development by serum diffusing through an agarose overlay. Fish spine beads filled with serum were placed on the overlying cells. The utilization of serum mixtures further provided a saving of materials. These techniques when applied to a group of field specimens were found to give reliable results. Similarly homologous antibody in the convalescent serum of recovered donor sheep could be demonstrated by this technique and served to confirm the immunological classification of the samples.The journals have been scanned in colour with a HP 5590 scanner; 600 dpi. Adobe Acrobat v.11 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.

Natural and sail-displaced doubly-symmetric Lagrange point orbits for polar coverage

This paper proposes the use of doubly-symmetric, eight-shaped orbits in the circular restricted three-body problem for continuous coverage of the high-latitude regions of the Earth. These orbits, for a range of amplitudes, spend a large fraction of their period above either pole of the Earth. It is shown that they complement Sun-synchronous polar and highly eccentric Molniya orbits, and present a possible alternative to low thrust pole-sitter orbits. Both natural and solar-sail displaced orbits are considered. Continuation methods are described and used to generate families of these orbits. Starting from ballistic orbits, other families are created either by increasing the sail lightness number, varying the period or changing the sail attitude. Some representative orbits are then chosen to demonstrate the visibility of high-latitude regions throughout the year. A stability analysis is also performed, revealing that the orbits are unstable: it is found that for particular orbits, a solar sail can reduce their instability. A preliminary design of a linear quadratic regulator is presented as a solution to stabilize the system by using the solar sail only. Finally, invariant manifolds are exploited to identify orbits that present the opportunity of a ballistic transfer directly from low Earth orbit

Plaque formation by bluetongue virus

The formation of plaques in a line of mouse fibroblast cells under agarose, by 16 tissue culture and 14 egg adapted strains of bluetongue virus is described. Optimal conditions for routine plaque assay were determined and certain basic requirements substantiated. The technique was used to determine the thermal stability of the virus under various conditions and in selected biological stabilizers.The journals have been scanned in colour with a HP 5590 scanner; 600 dpi. Adobe Acrobat v.11 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format