increased pathogenicity of an ehrlichia-like agent after passage through amblyomma hebraeum: a preliminary report. | after being passaged through 3 generations of amblyomma hebraeum, an ehrlichia-like agent isolated from an adult hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater. cross-immunity between this agent and several stocks of cowdria ruminantium and high levels of antibody elicited by the agent against 2 stocks of c. ruminantium in the indirect fluorescent antibody test, confirmed its close relationship to cowdria. | 1990 | 2293132 |
the relationship between cowdria and ehrlichia: change in the behaviour of ehrlichial agents passaged through amblyomma hebraeum. | following an earlier report that an ehrlichia-like agent isolated from an adult hyalomma truncatum female became more pathogenic and elicited a disease in sheep indistinguishable from heartwater after having been passaged through amblyomma hebraeum, a similar phenomenon is herewith recorded. an ehrlichial agent demonstrated in the blood smear of a serologically positive, naturally infected lamb, changed in behaviour and assumed the characteristics of cowdria after passage through a. hebraeum. cr ... | 1993 | 8134623 |
evidence to show that an agent that cross-reacts serologically with cowdria ruminantium in zimbabwe is transmitted by ticks. | the serological diagnosis of heartwater based on reactions to the immunodominant cowdria ruminantium major antigen protein-1 (map-1) is impaired by the detection of false-positive reactions. in this study, the prevalence of false-positive reactions on seven heartwater-free farms in zimbabwe was determined to be 8-94% by immunoblotting against c. ruminantium antigens. the highest prevalence of false-positives on spring valley farm correlated with the presence of rhipicephalus evertsi evertsi tick ... | 1998 | 9493330 |
ehrlichia ruminantium variants which do not cause heartwater found in south africa. | in 1994 a batch of apparently healthy goats was selected for intended export to the usa from a heartwater-free and vector tick-free region of south africa. the animals were tested serologically for heartwater, using either or both an ifa and an elisa test, and 52% were found to be serologically positive. a pcr assay based on ehrlichia ruminantium 16s gene sequences gave positive results for 54% of the animals, suggesting that apparently non-pathogenic e. ruminantium variants existed in this hear ... | 2007 | 17123750 |
the prevalence of serum antibodies to ehrlichia ruminantium infection in ranch cattle in tanzania: a cross-sectional study. | serum samples collected in a cross-sectional survey of grazing cattle on manyara ranch, monduli district, tanzania, were tested by indirect major antigenic protein 1 fragment b (map 1-b) elisa to determine the seroprevalence of ehrlichia ruminantium and to assess ranch-level risk factors for heartwater. heartwater-exposed cattle were widespread on the ranch and overall seroprevalence was 50.3% (95% ci, 44.9-55.6), enough to indicate an endemically unstable situation. multivariate logistic regres ... | 2008 | 18846851 |
multiple pathogens including potential new species in tick vectors in côte d'ivoire. | our study aimed to assess the presence of different pathogens in ticks collected in two regions in côte d'ivoire. | 2016 | 26771308 |