Biomedical subjects

R Queval

Publications and source records attributed to R Queval.

At least 19 recordsLinked to original sources

PubMed1987

Studies on the major histocompatibility complex of indigenous cattle in the Ivory Coast.

The MHC (BoLA) type has been determined for cattle from three breeds in West Africa. Seventy Baoule, 50 N'Dama and 30 Zebu cattle from the centre and north of the Ivory Coast were tested. Lymphocytes from these cattle were tested in a lymphocytotoxicity test with alloantisera detecting all of the internationally recognised BoLA sera. 78 sera prepared in Edinburgh and 57 in Jouy-en-Josas were used in the study. The results showed that sera prepared in Europe detect similar specificities in West Africa. Although with some specificities the frequencies differ from those seen in Europe. The frequency of null alleles is higher than in Europe in the Ndama and Zebu animals indicating the existence of additional specificities which will require the production of alloantisera in these breeds. However in the Baoule the null allele frequency is lower even then in some European breeds. The population data in which no animals have more than two workshop specificities is consistent with a single locus control in West Africa as in Europe.

Alleles↗

PubMed1987

Identification and selection of cattle naturally resistant to African trypanosomiasis.

Cattle were exposed to natural trypanosome challenge in an area of high Glossina density (Samandéni, Burkina Faso) for various periods of time during 1982, 1983, 1984 and 1985. All of 30 Zebu proved to be sensitive to trypanosomiasis i.e. they died or were treated in extremis in 10 +/- 4 weeks. Twenty-one (31%) Baoulé were as sensitive as the Zebu while 47 (69%) were resistant i.e. they survived in good condition. Twenty Ndama/Baoulé crosses, indigenous to Samandéni were all resistant. Weekly blood samples were taken (2,317 in total) for the determination of parasitaemia and packed cell volume (PCV) as a measure of anaemia, the most important pathological feature of cattle trypanosomiasis. In both Zebu and sensitive Baoulé 59% of the blood samples showed positive parasitaemia, of which 38% and 52% respectively were T. congolense the major cattle pathogen in the area considered. In resistant Baoulé and Ndama/Baoulé 11% and 10% of the samples were positive for trypanosomes of which only 4% and 2% were T. congolense respectively. PCV decreased from 35 to 20 in Zebu, 39 to 20 in sensitive Baoulé and 40 to 34 in resistant Baoulé, there was no change in the indigenous Ndama/Baoulé. Six Ndama/Baoulé indigenous to Samandéni remained resistant to trypanosomiasis when moved to another area of high Glossina challenge. Seven Ndama/Baoulé calves, conceived in Samandéni but born and kept for 2 1/2 years in a Glossina-free area, also proved to be resistant to challenge. Twelve Baoulé calves, born from cattle selected under natural field challenge, and which had not come in contact with trypanosomes for the first 10 months of their life, proved to be resistant when exposed in the field. These observations show that some, but not all, cattle from the Baoulé breed are naturally resistant to African trypanosomiasis, that this resistance does not need repeated exposure to trypanosomes early in life but appears to be inherited and functional against many types of antigenically different trypanosomes. Thus, selective breeding of trypanoresistant animals and their successful introduction, without trypanocidal drug protection, into areas of high Glossina density appears feasible.

Animals↗

PubMed1985

High and low responsiveness of bovine lymphocytes to Trypanosoma brucei in vitro: lack of correlation with resistance to trypanosomiasis.

Bovine peripheral blood lymphocytes (PBL) were stimulated to proliferate in vitro by live, irradiated or freeze-thawed Trypanosoma brucei, but not by the isolated variant surface glycoprotein. The optimal dose was 10(5) trypanosomes per 5 X 10(5) lymphocytes in 0.2 ml. Maximal proliferation was at day 5. Of the 98 cattle tested, 36 were high-responders (stimulation indexes 20-104), 49 were low or non-responders (SI 1-10) and 13 were intermediate. The responder status of individual animals did not change over a period of 1 year, nor did it alter following deliberate trypanosome infection. The stimulation was dependent on macrophage/monocyte type accessory cells, and this co-operation did not seem to be MHC restricted. Lack of stimulation of non-responder PBL did not appear to be due to the activation of suppressor cells. Accessory cells from non-responder animals could complement PBL from responders, but accessory cells from responders could not complement non-responder PBL. Responsiveness is therefore a characteristic of lymphocytes. Analysis of the surface markers of these lymphocytes or the blast cells generated in culture showed that they were a subpopulation of T cells, possibly TH cells. Analysis of PBL from 98 animals, which had been selected for trypanoresistance or trypanosensitivity under natural tsetse fly challenge, failed to establish a correlation between resistance and level of lymphocyte stimulation by trypanosomes in vitro.

Animals↗

PubMed1984