Biomedical subjects

John M Gay

Publications and source records attributed to John M Gay.

9 recordsLinked to original sources

PubMed2006

Theriogenology and developments in epidemiology: future opportunities?

The concepts and methods of the different branches of epidemiology, particularly clinical epidemiology, have much to offer the discipline of theriogenology. As with theriogenology, epidemiologic methods evolve when technological innovation enables new approaches to old problems. The recent emergence, from clinical epidemiology, of the evidence-based medicine paradigm in human medicine, and the associated developments of systematic reviews and meta-analysis, present new opportunities for collaboration and synergy between the two disciplines.

Animals↗

PubMed2006

Neosporosis in dairy cattle: an update from an epidemiological perspective.

Our understanding of the epidemiology of bovine neosporosis is advancing rapidly with considerable research activity being facilitated by improving methods. The dynamics of the infection in the known definitive hosts, the dog and the coyote, are being described. Improved procedures for production of oocysts enables the horizontal transmission to intermediate hosts and the subsequent more natural infection process to be studied. Details of the sylvatic cycles, potentially involving other animals in the dairy environment, are also emerging.

Abortion, Veterinary↗

PubMed2006

Determining cause and effect in herds.

This article presents components of the logical process for deter-mining cause and effect and lists common cognitive errors of the medical decision-making process. Individuals who are aware of these errors may be better able to avoid committing them. The first section provides the concepts used in considering cause and effect relationships, the second section provides a logical basis for evaluating cause and effect relationships, and the third section illuminates potential reasoning errors.

Animal Diseases↗

PubMed2004

Comparison of plasma disposition of alkaloids after lupine challenge in cattle that had given birth to calves with lupine-induced arthrogryposis or clinically normal calves.

OBJECTIVE: To compare plasma disposition of alkaloids after lupine challenge in cattle that had given birth to calves with lupine-induced arthrogryposis and cattle that had given birth to clinically normal calves and determine whether the difference in outcome was associated with differences in plasma disposition of anagyrine. ANIMALS: 6 cows that had given birth to calves with arthrogryposis and 6 cows that had given birth to clinically normal calves after being similarly exposed to lupine during pregnancy. PROCEDURES: Dried lupine (2 g/kg) was administered via gavage. Blood samples were collected before and at various time points for 48 hours after lupine administration. Anagyrine, 5,6-dehydrolupanine, and lupanine concentrations in plasma were measured by use of gas chromatography. Plasma alkaloid concentration versus time curves were generated for each alkaloid, and pharmacokinetic parameters were determined for each cow. RESULTS: No significant differences in area under the plasma concentration versus time curve, maximum plasma concentration, time to reach maximum plasma concentration, and mean residence time for the 3 alkaloids were found between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Because no differences were found in plasma disposition of anagyrine following lupine challenge between cattle that had given birth to calves with arthrogryposis and those that had not, our findings do not support the hypothesis that between-cow differences in plasma disposition of anagyrine account for within-herd differences in risk for lupine-induced arthrogryposis.

Alkaloids↗

PubMed2003

Survival of Salmonella enterica in freshwater and sediments and transmission by the aquatic midge Chironomus tentans (Chironomidae: Diptera).

Survival of a nalidixic acid-resistant strain of Salmonella enterica serovar Typhimurium mr-DT-104 in water and sediments was tested using artificially contaminated aquaria. Water samples remained culture positive for salmonella for up to 54 days. Sediment samples were culture positive up to 119 days. In addition, potential mechanisms for spreading salmonella in the environments by chironomid larvae and adults were tested. We evaluated the acquisition of mr-DT-104 by chironomids from contaminated aquatic sediments and subsequent spread to uncontaminated sediments. Larval chironomids raised in contaminated sediments became culture positive, and the bacteria were carried over to adults after emergence. Contamination of clean sediments by chironomid larvae was not demonstrated. These findings clearly suggest that mr-DT-104 serovar organisms can survive in aquatic sediments for at least several months. Uptake of salmonellae by chironomid larvae and adults suggests that they are possible vectors of mr-DT-104 in both aquatic and terrestrial environments, although the role of larval defecation in movement of bacteria to new sediments was not demonstrated.

Animals↗

PubMed2003

Temporal patterns of diagnostic results in serial samples from cattle with advanced paratuberculosis infections.

As part of investigating diagnostic strategies for Mycobacterium avium subsp. paratuberculosis (Map), serial results from polymerase chain reaction (PCR) on extraintestinal tissues (blood, milk, and liver) were compared with those from more conventional detection methods including serum enzyme-linked immunosorbent assay (ELISA), fecal culture, and fecal PCR. Three cows previously identified as being subclinically infected with Map were selected for the study. Blood, milk, and feces were collected daily and liver biopsies were obtained weekly for a 30-day period. Unexpectedly, a substantial daily variation in serum ELISA sample to positive (S/P) ratios was observed in all 3 cows. In contrast, fecal culture results were consistently positive. However, whereas fecal culture colony counts were consistently high for 2 cows throughout the study, colony counts from the third cow varied from day to day. Diagnostic sensitivity of PCR for fecal, blood, milk, and liver samples in these advanced subclinically infected cows was 87%, 40%, 96%, and 93%, respectively.

Animals↗

PubMed2002

Seroprevalence of antibodies against Neospora caninum in diagnostic equine serum samples and their possible association with fetal loss.

A case-control study of the association between the presence of serum antibodies against Neospora spp. and fetal loss was performed on serum samples submitted to a veterinary diagnostic laboratory in northwestern United States. Control sera were randomly selected from those submitted from healthy horses for routine equine infectious anemia testing required for regulatory health certification. Case sera were randomly selected from those submitted from aborting mares for diagnostic workup. Based on a 1:50 or greater titer on the indirect fluorescent antibody test, 8% of the 160 control sera and 13% of the 140 case sera were titer positive. The association odds ratio of 1.67 fell short of statistical significance (p=0.124).

Abortion, Veterinary↗

PubMed2002

Biosecurity for neonatal gastrointestinal diseases.

Infectious diarrhea is an important cause of neonatal calf morbidity and mortality that results in significant economic losses in the beef and dairy industries. Although numerous risk factors related to the occurrence of neonatal diarrhea have been identified, they can all be categorized into those that are related to the calf, the pathogens involved, or the environment of the calf. The immune status of calves, specifically the level of passively acquired immunity through colostrum, is the major risk factor related to the calf and the occurrence of diarrhea. Although numerous pathogens have been implicated in the occurrence of neonatal diarrhea, only a relatively limited number are commonly involved. Most should be viewed as secondary opportunists rather than primary pathogens, because none are extraordinarily virulent, and with the exception of Salmonella spp., most are present within the gastrointestinal tract of many healthy, mature cattle. Important risk factors related to pathogens involved in neonatal calf diarrhea involve the size of the inoculum and the occurrence of multiple infections. Finally, when considering the environment and housing conditions in which beef and dairy calves may reside, it is clear that tremendous variations exist. Despite these variations, the risk factors associated with the environment of the calf are also those that are the most amenable to the implementation of general environmental control and monitoring strategies as well as specific biosecurity measures.

Animal Husbandry↗

PubMedDate not supplied

Effects of trimethoprim-sulfadiazine on tear production and the fluctuations of Schirmer tear test values in horses.

The objectives of this study were to observe the effects of trimethoprim-sulfadiazine on equine tear production and to determine normal fluctuations in Schirmer tear test (STT) values in horses. A randomized, placebo-controlled, blinded clinical trial measuring STT values in 15 horses over an 8-week period was performed. The treatment group (eight horses) received 30 mg/kg trimethoprim-sulfadiazine orally once a day and the control group (seven horses) received placebo (flour) at the same time. All horses were housed outdoors throughout the study. Schirmer tear test values were measured at 0, 2, 4, 6 and 8 weeks, and 4 weeks after discontinuation of treatment. There were no significant differences in tear production between the treated and control groups. Fluctuations in STT were observed and may result from individual and environmental variations. Trimethoprim-sulfadiazine did not decrease tear production in the horses in this study. Horses normally experience periodic fluctuations in STT values.

Administration, Oral↗