Rinderpest surveillance performance monitoring using quantifiable indicators.

This paper describes an objective system of monitoring the performance of disease surveillance. The system was developed through dialogue with a number of countries in Africa and adopted as part of the Global Rinderpest Eradication Programme of the Food and Agriculture Organization of the United Nations. The performance monitoring system uses a clinical stomatitis-enteritis case definition, an outbreak investigation classification scheme, and a series of eight performance indicators to measure the sensitivity, specificity and timeliness of the surveillance system. Field-testing indicates that the approach is successful when good record-keeping is practiced and highlights the importance of dialogue in helping to ensure that the system is simple and acceptable. The system provides a quantitative measure of the efficacy of national disease surveillance programmes and of the quality of data derived from such programmes for use in international disease control, animal health information exchange and trade risk analysis.

Competitive ELISA for serodiagnosis of bluetongue: evaluation of group-specific monoclonal antibodies and expressed VP7 antigen.

The performance of 2 competitive enzyme-linked immunosorbent assays (C-ELISA) was compared with the reference C-ELISA I for the detection of antibodies to bluetongue virus (BTV). One of the assays (C-ELISA II) used a group-specific monoclonal antibody (MAb) to BTV, obtained from the American Type Culture Collection (8A3B-6) and tissue culture (TC)-derived BTV antigen (Ag), and the other assay (C-ELISA III) used BTV core protein VP7 (expressed in yeast) and the reference MAb (Pirbright Laboratory, 3-17-A3). Test sera were obtained by sequential blood samples from 22 calves, each inoculated with a different serotype (T) of BTV (South African [SA] T-1-T-16 and T-18-T-20 and USA T-11, T-13, and T-17). Sera were also obtained from 4 calves and 4 sheep inoculated with USA BTV T-10 and from several groups of calves exposed to single or multiple doses of epizootic hemorrhagic disease virus (EHDV) T-1-T-4 grown in TC (BHK-21) or suckling mouse brain (SMB). A total of 618 bovine and ovine field sera collected from BT-free and BT-endemic areas were also tested. The C-ELISA III was more sensitive than the C-ELISA II in the detection of anti-BTV antibody in sera from cattle and sheep early after infection with BTV. Seroconversion was demonstrated by the 3 C-ELISAs in all animals inoculated with BTV by 20 days postinfection (DPI), except in calves that received SA T-3 or USA T-13, which became positive at 40 DPI.(ABSTRACT TRUNCATED AT 250 WORDS)

Importance of ovine cytotoxic T cells in protection against bluetongue virus infection.

In sheep, bluetongue virus (BTV) was shown to induce anti-BTV cytotoxic T lymphocytes (CTL) and their effect to be maximal around 14 days post inoculation (p.i.) of virus. Using cellular adoptive transfer techniques in monozygotic sheep, such cells were shown to partially protect animals from BTV challenge. A short-lived cross-protective mechanism was identified involving thoracic duct lymphocytes (TDL) and nonneutralising antibody. These observations suggest that T lymphocytes play an important role in protection against BTV and that current vaccine design based on in vitro serological typing of BTV can be improved.

A study of the role of cell-mediated immunity in bluetongue virus infection in sheep, using cellular adoptive transfer techniques.

The transfer of thoracic duct lymphocytes from sheep inoculated 14 days, but not 7 days previously with bluetongue virus into their monozygotic twin resulted in some protection from challenge with bluetongue virus. T cell enrichment of the 14 day thoracic duct lymphocyte population resulted in a similar effect, indicating the T cell basis of the observed protection. Animals recovered from infection with bluetongue virus type 3 and which received thoracic duct lymphocytes from an identical twin recently infected with the same bluetongue virus type were protected from challenge with bluetongue type 4. These observations suggest that T lymphocytes play an important role in protection against bluetongue virus.

Production of murine cytotoxic T lymphocytes by bluetongue virus following various immunisation procedures.

The induction of bluetongue virus specific cytotoxic T lymphocytes (CTLs) in C3H mice by various live and inactivated bluetongue virus preparations was studied. Live virus preparations were shown to induce good levels of CTLs; however, inactivation of virus preparations either by beta propriolactone or glutaraldehyde induced only a low level response. The use of Freund's adjuvants and double immunisation procedures failed to improve the response of the inactivated preparations. These findings are discussed in relationship to protection from bluetongue disease with various bluetongue virus vaccines.

Generation of cross-reactive cytotoxic T lymphocytes following immunization of mice with various bluetongue virus types.

Mice immunized with a single bluetongue (BT) virus type were shown to produce cytotoxic T lymphocytes (CTL's) which cross-reactive with a number of BT virus types. These cross-reactive CTL's could be induced by both primary in vivo and secondary in vitro stimulation. A varying degree of cross-reactivity occurred with the six BT types examined. Aspects of the character of this cross-reactivity were examined and its role in protection from disease and vaccination strategy is discussed.

The induction of murine cytotoxic T lymphocytes by bluetongue virus.

After inoculation with live bluetongue virus, mice produced cytotoxic T lymphocytes (CTL) which showed virus and H-2 restriction. Inactivated preparations failed to induce CTLs. On secondary in vitro stimulation, specifically sensitised memory cells also produced high numbers of CTLs. The need for replicating virus to induce primary CTLs, evidence for partial type specificity and the role which cell-mediated immunity might play in the early stages of a bluetongue virus infection are discussed.