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U.W. Bangor - School of Informatics - Mathematics Preprints 1999

Biological and medical statistics


99.38 : LEHANE, M.J., MSANGI, A.R., WHITAKER, C.J. & LEHANE, S.M.

Grouping of trypanosome species in mixed infections in Glossina pallipides

Abstract:

Trypanosomes in the dissection-positive proboscis of Glossina pallipides were identified by PCR using species-specific primers. Of the 3,741 flies dissected 643 were proboscis positive. PCR was performed on 406 dissection-positive probosces giving positive identifications in 352 (86.7%), and infection rates of 14.8% for congolense-type infections, 2.8% for vivax-type infections and 1.4% for the unidentified group. Of the 352 PCR identified infections 225 were single, 111 were double, 13 were triple infections and there were 3 quadruple infections. Statistical analysis suggests that mixed infections group into 3 largely separate divisions among the tsetse population
(i) Trypanosoma congolense savannah and T. congolense Kenya coast,
(ii) T. simiae, T. congolense Tsavo and T. godfreyi and
(iii) T. vivax.
We conclude that either differing feeding patterns among members of the fly population or the ability of the trypanosomes in each of the infection categories to significantly influence the maturation of trypanosomes in other categories are the most likely causes of the groupings noted.
Chi-squared analysis of dissection and PCR methods of trypanosome identification revealed profound differences (chi^2 = 19.1; D.F. = 1; P < 0.05). If confirmed in other studies these findings have serious implications for our understanding of trypanosome epidemiology in tsetse flies, much of which is founded on data from dissection-based trypanosome identifications.

Published in:

Parasitology 120 (2000) 583-592.


99.45 : CROWTHER, H.L., LEW, A.R. & WHITAKER, C.J.

The development of beacon use for spatial orientation in 6-8.5-month-old infants

Abstract:

The overall aim of this research was to establish the youngest age at which the use of beacons to aid spatial orientation could be demonstrated. Six- and 8.5-month-old infants were tested in a peekaboo paradigm in which they had to turn to a target location, either after displacement to a novel position and orientation (Study 1), or to a novel orientation only (Study 2). A beacon condition where there was a colourful landmark at the peekaboo location was contrasted with a non-beacon condition at each age. The 8.5-month-olds showed robust but modest gains in performance in the presence of a beacon, whereas the 6-month-old infants did not. A further study (Study 3) confirmed that performance was poor at 8.5 months in the absence of a beacon, even when displacements between training and test positions involved rotations only. This finding is contrary to that reported in earlier literature (Tyler and McKenzie, 1990). The possibility that onset of crawling (at a mean age of 8.5 months) could be linked both to the development of allocentric and egocentric spatial coding is left open by the relatively later age of competence found in the present series of studies.

Published in:

Infant Behaviour & Development 23 (2000) 41-59.


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