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U.W. Bangor - School of Informatics - Mathematics Preprints 1992

Biological and medical statistics


The role of temperature and nutritional status in flight initiation by Triatoma infestans


Flight initiation in Triatoma infestans is associated with low nutritional status and increases with rising temperature; it appears to be largely independent of bug age and sex. A predictive model for the probability of flight initiation was constructed based on weight:length ratios of the bugs and maximum ambient temperature, both of which can be ascertained in the field. The model accurately predicted the proportion of bugs initiating flight in >85% of the groups used in our study. The predictive equation was found to give significant fits with two independent data sets. From our results it might be expected that flight would be rare during colder (< 20 C) months but that 5-10% of the normal population of an infested house would fly on any given night during the hotter months when temperatures appraoch 30 C. If bug nutritional status falls significantly, this proportion could be expected to rise to 30%.

Published in:

Acta Tropica 52 (1992) 27-38.


Social and geographical risk factors in Helicobacter pylori infection


A correlation between childhood crowding and the later development of gastric cancer has been demonstrated by Barker and colleagues, who proposed that the relationship was a consequence of infection by an organism such as Helicobacter pylori. In order to test this hypothesis the presence of IgG antibodies to H. pylori in sera from blood donors in North Wales has been investigated. During donation sessions, donors answered questions relating to social conditions and domicile in childhood (at age 10 years) and adult life (the preceding 2 years).
A stepwise logistic regression analysis of the data demonstrated significant independent relationships between seropositivity and the following factors: sharing a bed in childhood, housing density, locality of birth, adult social class and age.

Published in:

Epidemiol. Infect. 111 (1993) 63-70.

92.30 : THOMAS, F.D. & KASSAB. J.Y.

Flouridation in Anglesey. A clinical study of dental caries in mothers at term.

Published in:

British Dental Journal 172 (1992) 136-140.

92.31 : WHITAKER, C.J.

Finite Mixture Distributions

Published in:

Genstat Newsletter 28 (November 1992) 27-38.

92.32 : McEWAN, P.K., LEHANE, M.J. & WHITAKER, C.J.

The effect of adult population density on flight initiation in Triatoma infestans (Klug) (Hem., Reduviidae)


This studt suggests that whilst nutritional status is the key factor determining flight initiation in Triatoma infestans the density of the adult bug population is also a significant factor. Under our experimental conditions there was an inverse relationship between density and flight activity in these bugs.

Published in:

J. Appl. Ent. 116 (1993) 321-325.

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