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D J O'Brien

Publications and source records attributed to D J O'Brien.

At least 19 recordsLinked to original sources
PubMed2006

A study of helminth parasites in culled cows from Ireland.

The objective of this study was to determine the prevalence and intensity of gastrointestinal nematode, lungworm and liver fluke infection in culled cows in Ireland. Abomasa, colorectal contents and livers were collected from 30 to 68 culled beef and dairy cows during autumn 2002 and summer 2003, respectively. Ostertagia ostertagi were found in the abomasa of only three (10%) cows sampled in autumn and in 38 (57%) cows examined in summer. The majority of positive animals had low burdens of O. ostertagi but a few individuals in the group sampled during the summer had a moderate infection (5000-10,000 adult worms). A proportion of the cows in the summer group were also co-infected with small numbers of Trichostrongylus axei. Cooperia oncophora predominated in the recoveries from the larval cultures although O. ostertagi were also recovered. The overall prevalence of Dictyocaulus viviparus was 14%, based on larval identification in faecal samples. Liver fluke, or varying degrees of pathology attributable to Fasciola hepatica, were present in 65% of the livers. The results of this study extend those of previous workers, which were largely limited to dairy cows alone and which focussed on gastrointestinal nematodes and did not include simultaneous infections with lungworm and liver fluke. It was concluded, from the level of polyparasitism evident in this study, that adult cattle should be considered in preventative approaches to bovine helminthosis.

Abattoirs↗
PubMed2003

Mycobacterium bovis (bovine TB) exposure as a recreational risk for hunters: results of a Michigan Hunter Survey, 2001.

SETTING: Tuberculosis caused by Mycobacterium bovis (bovine TB) is endemic in the white-tailed deer population of north-eastern Michigan. Hunters may be exposed to M. bovis via cutaneous inoculation while field dressing deer or by ingestion of undercooked venison. Michigan hunters have received inconsistent messages about their risk of acquiring tuberculosis from recreational exposure to deer. The most common health advice offered has been to wear gloves while field dressing deer and to cook venison products thoroughly. OBJECTIVE: Data were collected to quantify these self-protective activities and to characterize hunters practicing these activities. DESIGN: In 2001, we surveyed 1833 hunters who had successfully harvested deer in or near Michigan's bovine TB endemic area in 2000. RESULTS: The survey response rate was 78%. Most hunters (89%) reported field dressing deer, 43% of whom wore gloves. Most hunters (95%) reported eating venison, 55% of whom reported their venison was always cooked thoroughly. Several hunter characteristics, including older age, female sex, higher awareness level, and area of residence, were significantly associated with the practice of these self-protective activities. CONCLUSION: The survey results suggest that hunters should receive consistent advice encouraging glove use while field dressing deer and the thorough cooking of venison products before consumption.

Adolescent↗
PubMed2002

Tuberculosis in free-ranging wildlife: detection, diagnosis and management.

Mycobacterium bovis is emerging as an important pathogen of free-ranging wildlife in which it is a potential source of infection for domestic animals and a threat to valuable wildlife species. This review examines the procedures for the detection, diagnosis and management of M. bovis in wildlife populations. The ante-mortem detection of M. bovis infection in wildlife is difficult, due to the common occurrence of subclinical infections and the deficiencies of the currently available diagnostic tests. Serological tests are insensitive, while tests measuring cell-mediated immune responses show promise, but have not been sufficiently developed for routine use in most species. The diagnosis of M. bovis in free-ranging wildlife relies on post-mortem examination supported by histopathology and microbiology. A feature of M. bovis infections is the variation in the appearance and distribution of lesions in the different host species. Bacterial culture remains the gold standard for diagnosis of tuberculosis, while histopathology is limited by the frequent inability to distinguish lesions caused by M. bovis from those produced by other mycobacterial species. Deoxyribonucleic acid (DNA) fingerprinting and advanced typing techniques are increasingly being used to unravel the epidemiology of mycobacterial infections, including tuberculosis in free-ranging wildlife. An understanding of the epidemiology is essential if procedures are to be developed for the management of tuberculosis in wildlife. Few management options are currently available, especially for protected wildlife. Vaccination is the subject of much research, but further developments are required before it can be used to control tuberculosis in any animals, let alone in free-ranging wildlife.

Animals↗
PubMed2001

Unilateral vs. bilateral ultrasound in the monitoring of cerebral microemboli.

We used bilateral transcranial Doppler to monitor the number of microembolic events (ME) in the left and right middle cerebral arteries of 29 patients during cardiac surgery that required extracorporeal circulation. Based on a previously published study, we hypothesized that the commonly used method of doubling unilateral ME counts to obtain an estimated bihemispheric load would result in significant errors of estimation. In our sample, estimated bihemispheric counts were inaccurate by an average of 18% (range 0--80%). Despite this large range of error, calculation of Cronbach's alpha revealed that actual error due to unreliability (4%) was small relative to the large variation in ME counts across subjects in this patient series. These findings suggest that unilateral monitoring is sufficient when the goal is to characterize a given subject's ME load within the context of the other subjects in the sample. However, when precise ME counts are required, bilateral monitoring is essential.

Cardiac Surgical Procedures↗
PubMed2001

Tuberculous lesions in free-ranging white-tailed deer in Michigan.

Descriptions of the anatomical distribution of Mycobacterium bovis gross lesions in large samples of white-tailed deer (Odocoileus virginianus) are lacking in the scientific literature. This report describes the distribution of gross lesions in the 58 white-tailed deer that cultured positive for M. bovis among the 19,500 submitted for tuberculosis testing in Michigan (USA) in 1999. For the vast majority (19,348) of those tested, only the head was submitted; for others, only extracranial tissues (33) or both the head and extracranial tissues (119) were available. Among those deer that cultured positive, cranial gross lesions were noted most frequently in the medial retropharyngeal lymph nodes, although solitary, unilateral parotid lymph node lesions also were found. Extracranial lesions occurred most commonly in the thorax. The distribution of lesions largely agreed with the few existing case reports of the M. bovis in white-tailed deer, although gross lesions were also found in sites apparently not previously reported in this species (liver, spleen, rumen, mammary gland). Some practical issues that may assist future surveillance and public education efforts are also discussed.

Animals↗
PubMed2000

Spatial and temporal comparison of selected cancers in dogs and humans, Michigan, USA, 1964-1994.

Our aim was to investigate the geographic and time distributions of some biologically similar neoplasms in dogs and humans living in Michigan, USA, between 1964 and 1994. Our objective was to describe and compare the patterns of cancer in the two species while assessing the strength and dependence of those patterns. In this retrospective, registry-based study, histologically confirmed incident human and canine cancer cases were mapped, and second-order (K function) spatial analysis and one-dimensional nearest neighbor temporal analysis were performed on residence addresses and dates of hospital discharge/diagnosis. Included in the study were all 528 incident cases of canine lymphosarcoma, mammary adenocarcinoma, melanoma and spindle-cell sarcomas diagnosed at a veterinary teaching hospital between 1964 and 1994 having residence addresses in Ingham, Oakland, and Wayne Counties; and a stratified random sample of 913 incident human cases of comparable cancers diagnosed during the same time period from the same counties. Results suggest that processes determining spatial aggregation of cases in dogs and humans were not independent of each other, did not act uniformly over different geographic areas, operated at spatial scales <2000 m regardless of species, and tend to act upon dogs more strongly at shorter distances than on humans. Little evidence of interspecies concurrence of temporal clustering was found.

Adenocarcinoma↗
PubMed2000

Subsequent pulmonary embolism: risk after a negative helical CT pulmonary angiogram--prospective comparison with scintigraphy.

PURPOSE: To determine whether a helical computed tomographic (CT) scan that is negative for pulmonary embolism (PE) is a sufficiently reliable criterion to safely withhold anticoagulation therapy. MATERIALS AND METHODS: Patients with negative helical CT scans were prospectively compared with patients with negative or low-probability scintigrams. In a 460-bed university hospital and clinic, 1,015 adult patients underwent either scintigraphy or helical CT for possible PE for 25 months. Five hundred forty-eight patients who had negative images and were not receiving anticoagulation therapy were prospectively followed up for 3 months for clinical, new imaging, death certificate, or autopsy evidence of subsequent PE. Ninety-seven patients were lost to follow-up. RESULTS: Subsequent PE was found in two (1.0%) of 198 patients with negative CT scans, none of 188 patients with negative ventilation-perfusion (V-P) scans, and five (3.1%) of 162 patients with low-probability V-P scans (not statistically significant). Patients in the helical CT group were hospitalized more often, had more severe disease, had more substantial PE risk factors, and had a higher death rate. No deaths were attributed to PE in either group. CONCLUSION: The frequency of clinical diagnoses of PE after a negative CT scan was low and similar to that after a negative or low-probability V-P scan. Helical CT is a reliable imaging tool for excluding clinically important PE.

Adult↗
PubMed1999

Spatial and temporal distribution of selected canine cancers in Michigan, USA, 1964-1994.

Although rates are commonly used to compare regional disease occurrence, rate-independent methods might also be useful in circumstances where geographic occurrence of a disease is known, but calculation of disease rates is not feasible. This is frequently the case for diseases in companion animals, where accurate enumeration of populations-at-risk is often arduous. This study had two objectives: to demonstrate a rate-independent method for investigating disease aggregation in companion animals; and, to assess the spatial and temporal clustering of canine cases of four cancers that are biologically similar in dogs and humans. Geographic information systems and point-pattern analysis were used to assess the spatial and temporal clustering of incident cases of four types of canine cancer in three counties in Michigan between 1964 and 1994, and to generate hypotheses concerning disease aggregation. Significant (P < or = 0.01) spatial clustering was found that varied by county and cancer type. No definitive temporal patterns could be deduced from a temporal analysis of the cases of canine cancer in this study. These results demonstrate distance-based methods for assessing clustering of disease, and suggest that processes determining the aggregation of canine cancer cases do not act in a spatially uniform manner.

Animals↗
PubMed1999

Treatment and prophylaxis of psoroptic mange (sheep scab) using an ivermectin intraruminal controlled-release bolus for sheep.

In an experiment to determine the therapeutic efficacy of an ivermectin intraruminal controlled-release (CR) bolus, 14 mixed breed sheep of one lot were infested with Psoroptes ovis and subsequently divided into two groups of seven. In one of these groups each sheep received one ivermectin CR bolus appropriate to its weight, the other group remained as an untreated control. All mites were eliminated from the group receiving the bolus while the control group remained infested, the disease progressed, and all but one sheep required treatment for psoroptic mange before the end of the experimental period. A second lot of 14 sheep, free from P. ovis, were divided equally into two groups to determine the prophylactic efficacy of the ivermectin CR bolus. In one group, each sheep was given an ivermectin CR bolus according to body weight and the sheep in the other group received no medication and served as untreated controls. Twenty-one days later two sheep infested with psoroptic mange were introduced into each of the groups. These donor sheep were removed 10 days later. The group treated with the ivermectin CR bolus remained mange-free and did not harbour any mites. All of the sheep in the control group developed psoroptic mange and required treatment to control the infestation at the end of the experimental period. Sheep that received the ivermectin CR bolus had greater mean weight gains than the control groups in these experiments. The ivermectin CR bolus releases a minimum dose of 20 microg ivermectin kg/day for 100 days: this prolonged activity should prove a valuable asset for the treatment and control of psoroptic mange in sheep.

Animals↗
PubMed1999

Treatment of psoroptic mange with reference to epidemiology and history.

Treatment methods in the last century involved the use of substances such as sulphur, mercury, hellebore, arsenic, nicotine and others, applied in various ways. The advent of dips in 1843 signalled an advance. However, the biology of the mite, Psoroptes ovis, the epidemiology of sheep scab and the lack of persistence of the acaricides necessitated repeated laborious treatments to ensure success. In 1947 this changed with the use of organo chlorines (OCs) which had up to 3 months residual activity. The use of OCs led to the eradication of psoroptic mange of sheep in USA. Organo phosphates (OPs) were introduced in the late fifties and synthetic pyrethroids (SPs) in the early seventies. In 1985, due to sheep tissue residues, lindane (OC) was withdrawn from the market and this greatly reduced the capacity for effective sheep scab control. Before the arrival of the endectocidal avermectin, ivermectin in 1978 and its successful use as an acaricide in 1992, control of psoroptic mange was limited to plunge dipping. In 1994 moxidectin, a milbemycin, was found to be effective and to have the added benefit of at least 4 weeks persistent activity. Another avermectin doramectin was shown, in 1995, to successfully treat scab and recently an ivermectin bolus has been introduced which has a 100 days' activity and is fully therapeutic and prophylactic. Strict attention to detail in the use of injectable products is essential in order to achieve satisfactory results. Work is progressing on the use insect growth regulators (IGRs) and also on naturally occurring substances such as linalool, neem and lavender oil. At the CVRL Dublin, promising results have been achieved with neem and some IGRs. Other areas of interest are allemones, synergists, microclimate manipulation, sheep breed resistance and vaccines. Successful control depends on epidemiological knowledge, accurate diagnostic techniques, intimate knowledge of the mite's life cycle, its behaviour on and off the host, its macro and molecular biology, the nature of the pathogenesis of the disease, sheep husbandry practices, nutritional and environmental factors; also farmer awareness and attitudes. The variable responses of sheep to the mite, the unpredictable incubation period, course, manifestations and outcome make this an intriguing and perplexing disease. Ways to overcome these problems and to achieve possible eradication are discussed.

Acyclic Monoterpenes↗
PubMed1999

The use of moxidectin for the prevention and treatment of psoroptic mange (scab) in sheep.

The introduction of systemic injectable products, belonging to the avermectin/milbemycin class of antiparasitic compounds, has provided an alternative to dips for sheep scab control. Their main advantages are that they are quicker and safer to use, cause less stress to the sheep (hence can be used in heavily pregnant ewes), do not require any special handling facilities for their use and do not present the same environmental concerns over disposal of spent product. Moxidectin, a second generation milbemycin, has recently been registered as an injectable product for the prevention and treatment of sheep scab. Laboratory and field studies carried out in the UK and Ireland have shown that two injections at a dose rate of 200 mg/kg bwt., 10 days apart, are 100% effective in the treatment of scab. Further studies have shown that a single injection at the same dose rate will protect against infestation or reinfestation for a period of at least 28 days. This long persistent activity has been evaluated in two large-scale field prophylactic trials, one in Ireland and one in the UK, involving over 16,000 sheep, in which it was demonstrated that a single injection of moxidectin is a safe and effective alternative to dips for routine prevention of scab.

Administration, Topical↗
PubMed1999

A review of the use of a controlled-release formulation of ivermectin in the treatment and prophylaxis of Psoroptes ovis infestations in sheep.

The options for the treatment and control of sheep scab (psoroptic mange) have been increased in recent years through the introduction of the endectocides ivermectin, doramectin and moxidectin. Whilst therapeutic efficacy is good, the current injectable formulations offer limited protection against re-infestation with Psoroptes ovis. An intraruminal controlled-release formulation of ivermectin has been developed to provide therapeutic and prophylactic activity against a range of sensitive endo- and ecto-parasites of sheep for 100 days after administration. These ivermectin boluses are designed to release ivermectin at 20-40 microg/kg/day over 100 days and were developed for use in sheep of 20-90 kg bodyweight. Several controlled therapeutic and prophylactic trials against sheep scab have been conducted under a variety of protocols with such boluses in Europe and South America. The results of these studies indicate that the bolus provides 100% therapeutic efficacy against established P. ovis infestations and equivalent prophylactic efficacy against challenge infestations administered during the active life of the bolus.

Animals↗
PubMed1999

Oxytocin, vasopressin, and autism: is there a connection?

Autism is a poorly understood developmental disorder characterized by social impairment, communication deficits, and compulsive behavior. The authors review evidence from animal studies demonstrating that the nonapeptides, oxytocin and vasopressin, have unique effects on the normal expression of species-typical social behavior, communication, and rituals. Based on this evidence, they hypothesize that an abnormality in oxytocin or vasopressin neurotransmission may account for several features of autism. As autism appears to be a genetic disorder, mutations in the various peptide, peptide receptor, or lineage-specific developmental genes could lead to altered oxytocin or vasopressin neurotransmission. Many of these genes have been cloned and sequenced, and several polymorphisms have been identified. Recent gene targeting studies that alter expression of either the peptides or their receptors in the rodent brain partially support the autism hypothesis. While previous experience suggests caution in hypothesizing a cause or suggesting a treatment for autism, the available preclinical evidence with oxytocin and vasopressin recommends the need for clinical studies using gene scanning, pharmacological and neurobiological approaches.

Autistic Disorder↗
PubMed1998

Effect of CTP synthetase regulation by CTP on phospholipid synthesis in Saccharomyces cerevisiae.

CTP synthetase (EC 6.3.4.2, UTP:ammonia ligase (ADP-forming)) activity in Saccharomyces cerevisiae is allosterically regulated by CTP product inhibition. Amino acid residue Glu161 in the URA7-encoded and URA8-encoded CTP synthetases was identified as being involved in the regulation of these enzymes by CTP product inhibition. The specific activities of the URA7-encoded and URA8-encoded enzymes with a Glu161 --> Lys (E161K) mutation were 2-fold greater when compared with the wild-type enzymes. The E161K mutant URA7-encoded and URA8-encoded CTP synthetases were less sensitive to CTP product inhibition with inhibitor constants for CTP of 8.4- and 5-fold greater, respectively, than those of their wild-type counterparts. Cells expressing the E161K mutant enzymes on a multicopy plasmid exhibited an increase in resistance to the pyrimidine poison and cancer therapeutic drug cyclopentenylcytosine and accumulated elevated (6-15-fold) levels of CTP when compared with cells expressing the wild-type enzymes. Cells expressing the E161K mutation in the URA7-encoded CTP synthetase exhibited an increase (1.5-fold) in the utilization of the Kennedy pathway for phosphatidylcholine synthesis when compared with control cells. Cells bearing the mutation also exhibited an increase in the synthesis of phosphatidylcholine (1.5-fold), phosphatidylethanolamine (1.3-fold), and phosphatidate (2-fold) and a decrease in the synthesis of phosphatidylserine (1.7-fold). These alterations were accompanied by an inositol excretion phenotype due to the misregulation of the INO1 gene. Moreover, cells bearing the E161K mutation exhibited an increase (1.6-fold) in the ratio of total neutral lipids to phospholipids, an increase in triacylglycerol (1.4-fold), free fatty acids (1.7-fold), and ergosterol ester (1.8-fold), and a decrease in diacylglycerol (1. 3-fold) when compared with control cells. These data indicated that the regulation of CTP synthetase activity by CTP plays an important role in the regulation of phospholipid synthesis.

Amino Acid Substitution↗
PubMed1997

Association between blood pressure and dietary factors in the dietary and nutritional survey of British adults.

OBJECTIVES: To measure the associations among blood pressure, hypertension, and recorded dietary factors. METHODS: Data were analyzed from the computer file of the Dietary and Nutritional Survey of British Adults, in which persons of both sexes aged 16 to 64 years living in private households (excluding pregnant women) had been randomly selected from the United Kingdom Electoral Register. Main outcome measures were systolic blood pressure, diastolic blood pressure, and hypertension (defined as systolic blood pressure of > or = 140 mm Hg, diastolic blood pressure of > or = 90 mm Hg, or both, or receiving antihypertensive medication). RESULTS: After controlling for 24-hour urinary potassium excretion, age, obesity, alcohol intake, and season of interview, a single measure of 24-hour urinary sodium excretion was significantly associated with systolic blood pressure (P < or = .001), diastolic blood pressure (P < .05), and hypertension (P = .009). These associations persisted after controlling for many variables of blood chemistry and dietary intake. CONCLUSIONS: Sodium is positively associated with blood pressure over a range of sodium excretion rates from 70 to 400 mmol/d. This finding supports the international consensus that the risk of hypertension is lower when salt intake is lower and suggests that a proportion of the British population has a sodium excretion rate that is habitually low enough to have some preventive effect.

Adult↗
PubMed1997

A novel dip formulation of a synthetic pyrethroid (SP) for the control of blowfly myiasis of sheep.

Field trials were carried out during the summer months of 1994 and 1995 to ascertain the prophylactic effects of a 10% w/w formulation of a synthetic pyrethroid (Ecofleece, Cross Vetpharm Group Ltd.) against sheep blowfly myiasis (fly strike). The trials were carried out on the same three farms each year. The flocks, of mixed breeds, comprised between 500 and 700 sheep. Treated sheep which consisted of ewes and lambs were plunge dipped, with at least one complete immersion. At least 10% of each flock were left untreated to act as sentinels. Both sentinel and treated sheep mixed freely at pasture. All recorded cases of fly myiasis were treated by topical applications of the same formulation. Inspections of the flocks were made daily by the farmers and weekly by one of the investigators. Prophylaxis against blowfly myiasis was achieved for periods ranging from 3 to 9 weeks. On some occasions, fly larvae developed in faecal dags but failed to establish on the sheep or cause lesions.

Animals↗
PubMed1997

Treatment and prophylaxis of psoroptic mange of sheep by a 10% w/w dip formulation of high CIS-cypermethrin.

A 10% w/w dip formulation of high CIS-cypermethrin (Ecofleece sheep dip) was evaluated as a prophylactic and treatment method against Psoroptes ovis of sheep. A laboratory trial using groups of healthy sheep under challenge showed that, when dipped as directed for 1 min, they were protected against infection for at least 4 weeks. Twelve sheep infected with psoroptic mange at the laboratory were effectively treated by one dipping in Ecofleece. A field outbreak of psoroptic mange in a flock of 237 crossbred ewes was likewise successfully treated by just one dipping. As this formulation is also effective against blowfly myiasis it is a useful alternative to organophosphate dual purpose dips.

Animals↗