Complete In Vitro Life Cycle of Trypanosoma congolense: Development of Genetic Tools

Trypanosoma congolense is a parasite responsible for severe disease of African livestock. Its life cycle is complex and divided into two phases, one in the tsetse fly vector and one in the bloodstream of the mammalian host. Molecular tools for gene function analyses in parasitic organisms are essential. Previous studies described the possibility of completing the entire T. congolense life cycle in vitro. However, the model showed major flaws including the absence of stable long-term culture of the infectious bloodstream forms, a laborious time-consuming period to perform the cycle and a lack of genetic tools. We therefore aimed to develop a standardized model convenient for genetic engineering. We succeeded in producing long-term cultures of all the developmental stages on long-term, to define all the differentiation steps and to finally complete the whole cycle in vitro. This improved model offers the opportunity to conduct phenotype analyses of genetically modified strains throughout the in vitro cycle and also during experimental infections

Population Genetics of Trypanosoma evansi from Camel in the Sudan

Genetic variation of microsatellite loci is a widely used method for the analysis of population genetic structure of microorganisms. We have investigated genetic variation at 15 microsatellite loci of T. evansi isolated from camels in Sudan and Kenya to evaluate the genetic information partitioned within and between individuals and between sites. We detected a strong signal of isolation by distance across the area sampled. The results also indicate that either, and as expected, T. evansi is purely clonal and structured in small units at very local scales and that there are numerous allelic dropouts in the data, or that this species often sexually recombines without the need of the “normal” definitive host, the tsetse fly or as the recurrent immigration from sexually recombined T. brucei brucei. Though the first hypothesis is the most likely, discriminating between these two incompatible hypotheses will require further studies at much localized scales

Genetic selection for temperament affects behaviour and the secretion of adrenal and reproductive hormones in sheep subjected to stress

We investigated the effect of genetic selection for temperament on the way that stressors affect the behaviour and the adrenal and reproductive axes of sheep. We tested three hypotheses: (i) isolation would increase cortisol secretion and decrease luteinising hormone (LH) secretion more in nervous sheep than in calm sheep; (ii) isolation combined with simulated human presence would increase cortisol secretion and decrease LH secretion more in nervous sheep than in calm sheep and (iii) isolation combined with stressors that were not specific to the selection process (i.e. non-selection stressors) would increase cortisol secretion and decrease LH secretion equally in calm and nervous sheep. Isolation alone increased cortisol secretion and decreased LH secretion in nervous sheep but not in calm sheep. Compared to calm sheep, nervous sheep were more agitated during the first 2 h of isolation but not during the second 2 h of isolation. Exposure to non-selection stressors increased cortisol secretion, decreased LH pulse amplitude and the mean plasma concentrations of LH in both calm and nervous sheep. We conclude that genetic selection for temperament affects the behavioural expression of the stress response and the secretion of adrenal and reproductive hormones during isolation, but has less impact on their reactivity to non-selection stressors

Adaptation and validation of antibody-ELISA using dried blood spots on filter paper for epidemiological surveys of tsetse-transmitted trypanosomosis in cattle

The indirect enzyme-linked immunosorbent assay (ELISA) for the detection of anti-trypanosomal antibodies in bovine serum was adapted for use with dried blood spots on filter paper. Aborbance (450 nm) results for samples were expressed as percent positivity, i.e., percentage of the median absorbance result of four replicates of the strong positive control serum. The antibody-ELISA was evaluated in Zambia for use in epidemiological surveys of the prevalence of tsetse-transmitted bovine trypanosomosis. Known negative sample (sera, n=209; blood spots, n=466) were obtained from cattle from closed herds in tsetse-free areas close to Lusaka. Known positive samples (sera n=367; blood spots n=278) were obtained from cattle in Zambia's Central, Lusaka and Eastern Provinces, diagnosed as being infected with Trypanosoma brucei, T. congolense or T. vivax using the phase-contrast buffy-coat technique or Giemsa-stained thick and thin blood smears. For sera (at a cut-off value of 23.0 percent positivity) sensitivity and specificity were 86.1 and 95.2 percent respectively. For bloodspots (at a cut-off value) of 18.8 percent positivity) sensitivity and specificity were 96.8 and 95.7 percent respectively. The implications of persistence of antibodies following treatment or self-cure are discussed

Evaluation de quatre tests de diagnostic: frottis sanguins, CATT, IFI et ELISA-Ag dans l'étude de l'épidémiologie de la trypanosomose cameline à Trypanosoma evansi en Mauritanie

Une enquête sur l'épidémiologie de la trypanosomose cameline à T. evansi en Mauritanie a été conduite sur 2 078 dromadaires de tous âges dans quatre régions (Trarza, Gorgol, Adrar, Hodh El Chargui) à caractéristiques climatiques et écologiques différentes. La prévalence de l'infection a été déterminée par l'examen de frottis sanguins et par trois tests sérologiques, le card agglutination test for trypanosomosis (CATT), l'immunofluorescence indirecte (IFI) pour la détection d'anticorps et l'enzyme-linked immunosorbent assay (ELISA) pour la détection d'antigènes. La prévalence globale de l'infection était de 1,4 p. 100 à l'examen parasitologique. La séroprévalence était de 16,5 p. 100 au CATT, de 24,3 p. 100 à l'IFI et de 14, 1 p. 100 à l'ELISA-Ag. La prévalence variait selon la région, la stratégie de conduite d'élevage pratiquée par les éleveurs, les troupeaux et l'âge des animaux. Cette enquête a montré que la trypanosomose cameline était présente en Mauritanie, surtout dans les zones boisées, près des cours d'eau fréquentés par les animaux. (Résumé d'auteur