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Biomedical subjects

G T Edwards

Publications and source records attributed to G T Edwards.

At least 19 recordsLinked to original sources
PubMed1984

Prevalence of equine sarcocystis in British horses and a comparison of two detection methods.

Sarcocystis was detected in oesophageal samples from 245 (62 per cent) of 394 horses and ponies killed at a Cheshire abattoir between February and August 1981. Prevalence of infection was closely related to age, increasing from 28.6 per cent of animals up to two years old to 88.9 per cent of those over eight years old. There were no significant regional differences in prevalence between horses from north west England, Yorkshire or South Wales. Significantly more female horses were infected (69.7 per cent) compared with males (56.2 per cent). Gross examination methods detected fewer than 55 per cent of all infections compared with a tissue digest method. Sarcocysts ranged from 1 to 15 mm in length (mean 5.5 mm) and were up to 0.5 mm wide. Cyst wall morphology and bradyzoite dimensions suggest that the species involved is Sarcocystis bertrami (syn equicanis).

Animals↗
PubMed1982

Observations on the epidemiology of equine hydatidosis in Britain.

Of 1388 horses and ponies examined at two abattoirs in the north of England from November 1979 to September 1981, 123 (8.7 per cent) showed evidence of hydatid infection. Prevalence of infection was closely related to age, rising from nil in animals up to two years old to over 20 per cent of those over eight years. Full-mouthed horses and ponies had similar prevalence rates (14.9 and 14.5 per cent, respectively), but horses had nearly twice as many viable infections as ponies. The prevalence of infection varied with the region of origin of full-mouthed horses and ponies, with 18 per cent of those from mid and north west England infected, compared with approximately 12 per cent of horses and ponies from mid and south Wales, Yorkshire and Scotland. The highest rates of transmission of equine hydatidosis are believed to occur in south and east England. Infections were mainly hepatic, with only 11 per cent lung involvement. Sixty-six per cent of the infections were viable, 71 per cent of which had between one and 10 cysts. Multiocular cysts occurred in 26 per cent of infections.

Animals↗
PubMed1982

The prevalence of Gasterophilus intestinalis in horses in northern England and Wales.

The stomachs of 448 horses from northern England and Wales were examined for Gasterophilus larvae, and 237 (52.7%) were found to be infected with G. intestinalis. Larvae were present in stomachs examined during each month of the year except August. Second instar larvae occurred from September through February and third instars were present from November through July. Adult fly activity began in August as indicated by the presence of eggs on horses. The life-cycle of G. intestinalis in northern England and Wales is outlined from the data presented. The mean instar burdens were 15.7 second and 38.0 third instars, and more than 75% of the infections consisted of up to 50 larvae. Prevalence of infection and mean larval burdens declined with increasing age of host. Only one of 258 duodena examined was infected with G. nasalis and this horse originated from the south coast of England, outside of the catchment area of the other horses examined.

Animals↗
PubMed1982

Preliminary investigations into the immunization of lambs against infection with Taenia multiceps metacestodes.

Two trials were carried out to investigate the protective value of various antigens in the immunization of lambs against Taenia multiceps metacestode infections. The first trial involved groups of 5 or 6 lambs immunized with activated T. multiceps oncospheres; activated T. hydatigena oncospheres; T. multiceps coenurus fluid antigens, and two untreated control groups. All except one of the control groups were challenged orally with T. multiceps oncospheres 5 weeks later. The results of the trial were equivocal with 1 to 3 lambs from each group showing post-mortem evidence of infection. There was evidence that some lambs from this trial had previously been exposed to Taenia oncospheres, thus nullifying possible effects of immunization. A second trial used two groups of 5 "cestode free" lambs. One group was immunized with T. multiceps oncosphere-derived antigens prior to challenge and showed significant protection when compared with the sham-vaccinated controls.

Age Factors↗
PubMed1981

Some quantitative characters used in the identification of Taenia hydatigena, T. ovis, T. pisiformis and t. multiceps adult worms, and T. multiceps metacestodes.

Measurements were made of gravid worm lengths, scolex diameter, rostellum diameter, sucker diameter, and large and small rostellar hooks of adult Taenia hydatigena, T. multiceps, T. ovis and T. pisiformis obtained from dogs in North Wales. Values recorded agreed closely with published values. None of these characters could be used to differentiate reliably between the species except that, of the worms examined, those with large rostellar hooks greater than 228 microns were T. pisiformis and those with large hooks less than 168 microns were T. multiceps. The range of hook lengths of the different species overlapped considerably. Reliable identification required examination of mature proglottis morphology of specimens which were relaxed before fixation. Relaxed mature proglottides often showed a characteristic shape. Lengths of rostellar hooks of scolices from T. multiceps coenuri followed the same frequency distribution as adult worm books. A strong correlation was shown between coenurus volume and the number of scolices on the coenurus membrane, with a poor correlation between coenurus age and volume.

Animals↗
PubMed1978

The prevalence of Sarcocystis spp in dogs and red foxes.

Protozoan parasites of the genus Sarcocystis have been recognised for many years as intramuscular cysts of numerous vertebrates. It is only comparatively recently that the two-host nature of the life cycle has been recognised and that the intramuscular cysts are a stage in the developmental cycle of coccidian parasites of flesh eating mammals (Fayer 1974, Fayer and Johnson 1973, 1974, Rommel and others 1972, Dubey 1976). Carnivores ingest the intramuscular cysts from herbivores and presumably from other animals too and eventually shed sporulated tetrazoic sporocysts in their faeces. The cystic stages which occur in the flesh of herbivores are probably non-pathogenic but the earlier stages in which schizonts develop in vascular endothelium may be severely pathogenic. Sarcocystis cruzi, S ovicanis and S porcifelis are known to be severely pathogenic in cattle, sheep and pigs respectively (Dubey 1976). Observations on the prevalence of Sarcocystis spp in the faeces of working farm dogs, greyhounds and foxes (Vulpes vulpes) are recorded.

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