Search PubMed⌕ Search

Biomedical subjects

W G Ryan

Publications and source records attributed to W G Ryan.

At least 55 records · Page 3Linked to original sources
PubMed1989

Comparative study of early-season prophylaxis using ivermectin with lungworm vaccination in the control of parasitic bronchitis and gastroenteritis in cattle.

Twenty-four first-season calves were randomly allocated to three similar groups (1-non-treated controls; 2 - vaccinated against lungworm; 3 - treated with ivermectin 21, 56 and 91 days after turnout) and set-stocked on separate pastures. Parasitic bronchitis became evident in the controls and signs of parasitic gastroenteritis were seen later in the vaccinates, but the ivermectin-treated calves remained healthy. After autumn housing, all were kept as a single group for the winter. The following summer, six of the ivermectin-treated animals and their matching vaccinates were grazed together, without further prophylaxis, along with six first-season calves. The latter displayed evidence of mild but debilitating pulmonary and gastrointestinal parasitic disease while both groups of yearlings remained healthy (with the exception of one diarrhoeic vaccinate). Thus, the immune status of the ivermectin-treated animals appeared to be comparable to that of the vaccinates. This conclusion was supported by parasitological observations and by artificial challenge at the end of the second grazing season.

Animals↗
PubMed1989

Chemoprophylaxis and immunity to parasitic bronchitis in cattle--a field experiment comparing topical ivermectin and an oxfendazole intraruminal device.

Seeder calves infected with Dictyocaulus viviparus were used to contaminate a field divided into three similar paddocks. Twenty-four autumn-born calves were allocated to three matched groups; one group was given topical ivermectin treatments (0.5 mg/kg) at 3, 8 and 13 weeks after turnout (Day 0); each member of a second group was given an oxfendazole pulse-release intraruminal device (OPRB) at turnout; while a third group was kept as untreated controls to monitor the natural epidemiological pattern of events. Severe pasteurella pneumonia exacerbated by lungworm infection occurred in the controls after Day 24. Two died and repeated doses of antibiotic and anthelmintic therapy were necessary to save the remainder. Clinical signs were much milder in the ivermectin and OPRB groups and resolved with only a single dose of antibiotic. The OPRB group excreted some lungworm larvae at this time, but none was detected in the faeces of the ivermectin group during the grazing season. At housing, five calves from each group and four lungworm-naive calves were challenged with D. viviparus larvae. The infection became patent in all challenge-control calves, but no larvae were passed by any of the trial animals. Post-mortem worm-counts revealed percentage takes for the challenge controls, trial controls, ivermectin and OPRB groups of 16.7, 0.01, 0.9 and 0.2, respectively. All trial groups had therefore developed a substantial immunity.

Administration, Topical↗
PubMed1989

Fine-needle aspiration biopsy of the thyroid. Diagnostic accuracy when performing a moderate number of such procedures.

The diagnostic accuracy of fine-needle aspiration biopsy of the thyroid was evaluated. Between June 1982 and July 1987, 354 fine-needle aspiration biopsies were performed on 289 patients with thyroid nodules. The ages of the patients ranged from 21 to 86 years (median, 45 years); 61 (21%) were men and 228 (79%) were women. Surgical confirmation of the cytologic diagnosis was obtained in 59 patients. Fine-needle aspiration biopsy identified 10% of the nodules as probably malignant and 10% as possibly malignant. Of these nodules, 30.5% were proved to be malignant by histologic examination. The accuracy of distinction between a benign (class I or II) or probably malignant (class IV) diagnosis was 95.2%. Patient acceptance of this procedure was good and complications were infrequent. These results indicate that fine-needle aspiration biopsy of the thyroid is accurate, safe, well tolerated, and easily applied, without its highly desirable features being compromised, even when a moderate number of such procedures are performed.

Adult↗
PubMed1988

Immunity of ivermectin treated cattle to challenge from helminth parasites in the following season.

Two groups of yearling cattle which had been treated with ivermectin either three and eight, or three, eight and 13 weeks after turn out to trichostrongyle contaminated pasture in their first grazing season were exposed in the following season to natural challenge with helminth parasites. To assess their immunity to this challenge each group shared a pasture with parasite naive first season calves. No anthelmintic treatments were administered at any time during the year. Throughout the grazing period the yearlings showed normal respiratory rates, negative faecal lungworm larval counts, and, relative to the calves, low faecal trichostrongyle egg counts. All the first season calves developed patent lungworm infections and on one occasion the mean respiratory rates of each group of calves were significantly greater than those of the yearling cattle. At the end of the grazing period, from early May until late September or October 1986, the cattle were removed from pasture and together with parasite naive controls challenged with either 10 or 22 third stage larvae of Dictyocaulus viviparus/kg bodyweight and necropsied between 18 and 23 days later. Although the experimental challenge resulted in relatively heavy lungworm infection of the naive controls, none of the yearlings and only three of the 11 calves which had been at pasture were found to be infected. However, large numbers of arrested fourth stage larvae of Ostertagia ostertagi were present in all the naturally infected yearlings and calves.

Animals↗
PubMed1987

Control of parasitic bronchitis and gastroenteritis in grazing cattle by strategic prophylaxis with ivermectin.

In May 1985 four groups of 10 calves, aged between four and five months, were turned out on to separate, permanent pastures of equal area which had been seeded during the previous few days with larvae of Dictyocaulus viviparus. One group acted as a control, the second was vaccinated with lungworm vaccine before turnout and treated with thiabendazole three, eight and 13 weeks after turnout, while the third and fourth groups were given ivermectin three times (three, eight and 13 weeks after turnout) and twice (three and eight weeks after turnout), respectively. A severe outbreak of parasitic bronchitis resulted in the death of three control calves within five weeks of turnout and parasitic bronchitis and gastroenteritis affected the second group of calves after approximately four months at pasture. The calves given ivermectin excreted no lungworm larvae and remained free of clinical parasitism throughout the trial.

Animals↗
PubMed1987

Early season parasitic gastroenteritis in calves and its prevention with ivermectin.

In a two-year trial involving successive batches of 36 autumn-born steers on two adjacent sites in Hertfordshire, calves treated with ivermectin at three and eight weeks after turn out contaminated pastures much less than untreated control animals. Each year dry summers prevented the larval challenge on the control pastures from building up to high levels until about the time of autumn housing. Atypical outbreaks of parasitic gastroenteritis were recorded in May and June of the second year in both groups of control calves. Clinical and parasitological aspects of these outbreaks are discussed in the context of the epidemiology of the disease. It is concluded that the application of measures to control gastroenteritis can bring benefits in the early part of the grazing season as well as later in the year.

Animals↗