Abstract : Use of the electromagnetic spectrum for man's benefit has increased tremendously. However, the complete understanding of its potential and real biologic hazards has failed to keep pace. The present threshold limit value for microwaves is the subject of much debate. The eye and lens have been damaged by microwaves experimentally, but the mechanism of damage is as yet unexplained. A preliminary study was performed using radiofrequency exposure and rhesus monkeys. No cataracts were formed at a frequency of 19.27 MHz. Problems involved in future radiofrequency studies, and areas which require further studies, are discussed. (Author)
Objective To determine the prevalence of Mycoplasma spp in herds that were members of a milk cooperative. Design Epidemiologic study. Sample Population 267 dairy herds that were members of a milk cooperative. Procedure Bulk-tank milk samples were collected monthly during a 6-year period from all dairies in the cooperative. Samples were submitted to the cooperative's laboratory for bacterial culture for Mycoplasma spp, using direct plating. Milk samples positive for Mycoplasma organisms were speciated. Results Prevalence of positive samples varied from 1.8 to 5.8% for all species of Mycoplasma and from 1.2 to 3.1% for Mycoplasma spp known to be mastitis pathogens. One mycoplasmal species was isolated initially on 99 of 198 (50.0%) dairies, but 68 of 198 (34.3%) dairies had 2 species isolated. Mycoplasma bovis, M californicum, and M bovigenitalium were consistently isolated, but M bovis (243/499; 48.6%) was the most commonly isolated species. Acholeplasma laidlawii was more prevalent in 1989 and 1995 than other years. Mycoplasma bovigenitalium and M californicum had a seasonal distribution. Less than 50 colonies per plate were isolated for most (317/500; 63.4%) bulk-tank samples. Of the milk samples with > 100 colonies/plate, Mycoplasma bovis was isolated most frequently (73/243; 30.0%). Clinical Implications Distribution of Mycoplasma spp varied by year, number of colonies isolated per sample, season, and herd. Therefore, it may be necessary to routinely sample bulk-tank milk, and all isolates should be speciated. Culture results from milk cooperatives should be used with other monitoring information to determine the Mycoplasma status of herds. ( J Am Vet Med Assoc 1997;211:1036–1038)
SUMMARY Of 254 sheep examined for antibodies to the virus of ovine progressive pneumonia, 162 (63.8%) were seropositive. The mean age of the seropositive ewes was 4.9 ± 1.8 years, which was significantly greater than that for the seronegative ewes (4.1 ± 2.3 years). The age-specific prevalence increased with ewe age, from 25% among yearling ewes to 85% among 7-year-old ewes. Seropositive ewes produced more pounds of live lamb at birth than did seronegative ewes.
Summary Nonclinical mastitis in the dairy herds on St Croix, US Virgin Islands, represents a prevalent (97%) and severe problem (44% of quarters had California Mastitis Test results of 2 or 3). Streptococcus agalactiae (26%) and Staphylococcus aureus (22%) were the most prevalent pathogens. More than half (54%) of all organisms isolated and tested for resistance were resistant to ampicillin and benzyl penicillin; 29% were resistant to trimethoprim/sulfadiazine. Estimates of the loss of milk production suggested that there was a loss of 4.40 to 13.33 lb/cow/day. The yearly economic cost of prevention was estimated for each cow ($22.07); yearly income loss attributable to mastitis was estimated to be from $339 to $1,022/cow/yr. Suggestions for the prevention and control of mastitis are included.
Clinical mastitis is becoming more important as management improvements have resulted in greater control of nonclinical pathogens (2,11). Economic losses due to clinical mastitis include decreased milk production, discarded milk, loss of animals due to culling or death, therapeutic costs, veterinary fees, and labor (1,5). Clinical mastitis cases vary greatly in lost milk production, duration of treatment, duration of clinical signs, and risk of culling from the herd. At the onset of signs, it is difficult to predict which cases will be most severe. Accurate early prognosis for mastitis has economic value. This study was conducted to assess the ability of a single milk NA Gase level (obtained at clinical onset) to predict severity of mastitis.
