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T R Barton

Publications and source records attributed to T R Barton.

5 recordsLinked to original sources
PubMed2005

Tick-borne Great Island Virus: (I) Identification of seabird host and evidence for co-feeding and viraemic transmission.

Great Island Virus (GIV) is an arbovirus present in the tick Ixodes uriae, a common ectoparasite of nesting seabirds. Common guillemot (Uria aalge) and black-legged kittiwake (Rissa tridactyla) are the preferred and most abundant hosts of I. uriae on the Isle of May, Scotland. As part of a study to understand the epidemiology of GIV, the ability of guillemot and kittiwake to support tick-borne transmission of GIV was examined. GIV was present in ticks feeding in isolated guillemot colonies and guillemots had virus-specific neutralizing antibodies demonstrating previous GIV infection. By contrast, only uninfected ticks were found in colonies inhabited solely by kittiwakes. GIV was isolated from kittiwake ticks in colonies which also contained breeding guillemots but no virus-specific neutralizing antibodies were present in blood samples of kittiwake on which infected ticks were feeding. Thus guillemots are the main vertebrate hosts of GIV on the Isle of May whereas kittiwakes do not appear to be susceptible to infection. Virus infection of adult ticks feeding on guillemots was highly efficient and may involve both viraemic transmission and transmission from infected to uninfected ticks feeding together on birds that do not develop a patent viraemia.

Animals↗
PubMed2005

Tick-borne Great Island Virus: (II) Impact of age-related acquired immunity on transmission in a natural seabird host.

Tick-borne pathogen transmission is dependent upon tick number per host and the physical and temporal distribution of each feeding stage. Age-related acquired immunity to tick and pathogen may also be important but has received less attention. In this study we evaluate which of these parameters has the greatest impact on Great Island Virus (GIV) transmission between Ixodes uriae ticks and common guillemots (Uria aalge). The study system is well suited to investigate age-related effects because the guillemot population is naturally divided into 2 groups, older breeding and younger pre-breeding adult birds. The physical distribution and timing of adult and nymphal tick feeding was similar for both guillemot age groups. However, breeding birds were parasitized by significantly more ticks (mainly nymphs). Calculations based on tick number predict virus prevalence should be higher in ticks that have fed on breeding rather than pre-breeding birds. However, empirical evidence indicates the reverse. Protective acquired immunity to GIV infection may be the reason why GIV prevalence is actually significantly lower in ticks that have fed on breeders. Far more breeding (74%) than pre-breeding (12%) guillemots had antibodies that neutralized 1 or more GIV strains. Estimates of the force of infection support the view that pre-breeding birds experience higher rates of virus infection than breeding birds. The results indicate age-related acquired immunity is a key factor in GIV transmission and highlight the need to consider age-related effects and host immunity when undertaking quantitative studies of tick-borne pathogen transmission.

Age Factors↗
PubMed1999

Sexual activity among Zambian female teenagers: the role of interpersonal skills.

This study examined the relationship between interpersonal skills and sexual activity among female adolescents in Zambia. Data from 390 females in seven schools were analyzed. Results indicated that the inability to say no was associated with coital and noncoital sexual activity. The findings suggest that family planning programs should consider the role of interpersonal skills in controlling adolescent fertility.

Adolescent↗
PubMed1996

The activity periods and life-cycle of the tick Ixodes uriae (Acari: Ixodidae) in relation to host breeding strategies.

We investigated the timing of seasonal activity of the seabird tick Ixodes uriae by examining engorgement rates of off-host ticks and the prevalence of infested common guillemots (Uria aalge) and kittiwakes (Rissa tridactyla) on the Isle of May, Scotland. More than 99% of I. uriae fed during the period late April to early August which coincided with the seabird breeding season. No ticks fed in the autumn and winter, and none over-wintered in the engorged state. Peak tick feeding activity was during the hosts' incubation period in May and early June, when over 70% of birds were parasitized. Few ticks were active when guillemot chicks were being brooded, or during the early part of kittiwake chick-rearing. Adult female tick feeding peaked in the first week of June, while nymphal and larval activity peaked in the third week of May. Adult female ticks fed later than nymphs on guillemots and larvae on both guillemots and kittiwakes; however, there was considerable temporal overlap in the feeding periods of the 3 stages of both hosts. All larvae and nymphs fed in May and early June, but up to 18% of adult females remained unengorged at this time, and probably deferred feeding by 1 year. A small proportion of individuals which fed as larvae in May appeared to feed again as nymphs in July of the same season, thereby shortening their life-cycle by 1 year. The duration of the life-cycle of I. uriae on the Isle of May is typically 3 years but varies from 2 to 4 years. Ticks feeding on guillemots did so significantly earlier than those feeding on kittiwakes, possibly because guillemots start breeding earlier in the year. Breeding of both guillemots and kittiwakes was later in 1994 than in 1993. This delayed the activity of all tick stages on kittiwakes and adult female ticks on guillemots, but did not affect the timing of activity of nymphs or larvae feeding on guillemots.

Animals↗