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D Geysen

Publications and source records attributed to D Geysen.

24 records · Page 2Linked to original sources
PubMed2003

Detection of antibodies to the Ehrlichia ruminantium MAP1-B antigen in goat sera from three communal land areas of Zimbabwe by an indirect enzyme-linked immunosorbent assay.

A total of 1,286 caprine serum samples collected from three communal land areas in Zimbabwe from March 1999 to February 2000 were tested for Ehrlichia ruminantium antibodies using the indirect MAP1-B enzyme-linked immunosorbent assay. Of the 480 samples tested from Mudzi, a non-heartwater area, 425 (89.4 %) were positive. In the heartwater endemic areas, of the 441 samples 352 (79.4 %) from Gwanda and 300 of the 365 samples (83.2 %) from Bikita tested positive. The seroprevalence in the Bikita and Gwanda (approaching 90 %) is consistent with reports in related serological surveys that puts the seroprevalence of E. ruminantium in goats from endemic areas of Zimbabwe at 90 %. However, the high seroprevalence in the non-heartwater area of Mudzi is unexpected and can be a result of the presence of a serologically cross-reacting organism, which has to be isolated and characterized. The results need to be confirmed by alternative tests, based on molecular diagnostic tools. There were no significant differences in seroprevalence between the three sampling areas as there were between the three sampling periods. The highest corresponded with the period January to February (peak tick activity) and the lowest with the period July to September (minimal tick activity).

Animals↗
PubMed2002

Comparison of conventional techniques to differentiate between Taenia solium and Taenia saginata and an improved polymerase chain reaction-restriction fragment length polymorphism assay using a mitochondrial 12S rDNA fragment.

Given the constraints of classical diagnostic methods, i.e., morphological and isoenzymatic studies of proglottids, a polymerase chain reaction test complemented with restriction enzyme analysis has been modified by redesigning one of the primers to reduce nonspecific amplifications experienced when using field samples. The use of these new, highly cestode-specific primers and the restriction enzyme Ddel led to the development of a diagnostic assay that clearly distinguishes between Taenia saginata and T. solium proglottids in field samples. This assay confirms the presence of T. saginata in Ecuador. DNA amplification of some of these taeniids showed different patterns, suggesting the possibility that strain differences exist. These results demonstrate the need for development of useful molecular assays as reliable tools for epidemiological studies on cestodes.

Animals↗
PubMed2001

Molecular and immunological characterisation of Theileria parva stocks which are components of the 'Muguga cocktail' used for vaccination against East Coast fever in cattle.

The 'Muguga cocktail' which is composed of three Theileria parva stocks Muguga, Kiambu 5 and Serengeti-transformed has been used extensively for live vaccination against East Coast fever in cattle in eastern, central and southern Africa. Herein we describe the molecular characterisation of the T. parva vaccine stocks using three techniques, an indirect fluorescent antibody test with a panel of anti-schizont monoclonal antibodies (MAb), Southern blotting with four T. parva repetitive DNA probes and polymerase chain reaction (PCR)-based assays detecting polymorphism within four single copy loci encoding antigen genes. The Muguga and Serengeti-transformed stocks exhibited no obvious differences in their reactivity with the panel of MAbs, whereas Kiambu 5 differed with several MAbs. Kiambu 5 DNA was very distinct from the Muguga and Serengeti-transformed isolates in the hybridisation pattern with all four nucleic acid probes, whereas Muguga and Serengeti-transformed isolates exhibited minor differences and could not be discriminated with one of the probes. PCR amplification in combination with restriction fragment length polymorphism analysis indicated that Kiambu 5 was also markedly divergent from the Muguga and Serengeti-transformed stocks within two of the four antigen coding genes. The T. parva Serengeti-transformed stock did not contain a 130 base pair insert within the p67 sporozoite antigen gene, which has been observed previously in most T. parva parasites isolated from buffalo, and could not be discriminated from T. parva Muguga at any of the four single copy loci. Collectively the data indicate that two of the cocktail components T. parva Serengeti-transformed and Muguga are genetically closely related, while the third component Kiambu 5 is quite distinct. Based on the findings, there may be a need to include only one of the T. parva Muguga and Serengeti-transformed components in the immunising cocktail. The study demonstrates the value of molecular characterisation data for monitoring of live vaccines.

Animals↗
PubMed1999

Molecular epidemiology of Theileria parva in the field.

Molecular tools based on seminested RFLP-PCR techniques to characterize field parasites in bloodspots dried on filter paper permitted investigation of the extent and the dynamics of diversity of Theileria parva populations in the field. Parallel molecular studies explored the long-term genome stability of various isolates by probing Southern blots of EcoRI digested total genomic DNA with four different reference nucleic acid probes. Three polymorphic single copy loci encoding for antigen genes were developed for seminested PCR detection in order to apply them for a multilocus approach in population genetic studies. Seven alleles were identified for the polymorphic immunodominant molecule (PIM) locus by using restriction enzymes, and 4 alleles each for the p150 and p104 loci. A simple DNA extraction method gave good results in amplifying these loci from carrier animals using samples of blood dried on filter papers. Results from probing Southern blots of cultures taken at sequential timepoints indicate relative genome stability in T. parva in comparison to other parasitic protozoa such as Plasmodium. Comparatively homogeneous profiles in sympatric isolates from Zambia were identified using all four probes and PCR amplified products which contrasted with the variety found amongst Kenyan stocks. Preliminary characterization of T. parva field samples from the Southern Province of Zambia strongly suggest clonal expansion of one of the components of a non-Zambian trivalent vaccine used on a limited scale in the Province from 1985 until 1992.

Animals↗
PubMed1985

Screening of medicinal plants of Rwanda for acaricidal activity.

A series of 108 samples from 42 medicinal plants of Rwanda have been screened for acaricidal activity against the female tick Rhipicephalus appendiculatus. Two plants, Solanum dasyphyllum (fruits) and Neorautanenia mitis (roots) showed apparent acaricidal activity in the petroleum ether fraction.

Animals↗