Recurrent mastitis-persistent or new infections?

Recurrent clinical mastitis contributes to around half of all infections having an economic impact in the dairy industry. It leads to milk yield reduction, increased risk of mortality, and culling, and may be caused by new infections or a persistent infection after previous treatment. Disease management is dependent on the infecting species, necessitating accurate identification of the pathogen in the range of persistent and reinfection cases among recurrent infections using culture and molecular biological analysis. Milk samples from diagnosed clinical mastitis cases were collected from three Northern German dairy farms between 2011 and 2015. Totally, 2043 diagnosed mastitis cases were examined at quarter level (1598 (78.2 %) first and 445 (21.8 %) recurrent mastitis cases in lactation). Among the recurrent cases, 145 (32.6 %) cases were confirmed to harbor the same pathogenic species as previous infections. RAPD PCR confirmed the same species strain in 49 (11 %) of the recurrent infections. The contribution of new infections as compared to persistent infections in cases of clinical mastitis is clear from the data. Future studies in recurrent clinical mastitis control should be focused on influencing factors to prevent new infections in addition to therapeutic intervention and bacteriological cure.

Associations between Streptococcus uberis strains from the animal environment and clinical bovine mastitis cases.

Bovine clinical mastitis quarter foremilk samples were collected from 15 German dairy farms for the isolation of Streptococcus uberis strains. Samples were also collected from the 8 spots where Streptococcus uberis was most expected in the dairy environment to investigate the transmission behavior of Streptococcus uberis within the farm. The selected environmental spots for sampling were the inner surface of the milking liner, drinking troughs (on pasture and in the barn), exit area of milking parlor, bedding material from the lying area in the barn, passageway to pasture, lying area of soil or vegetation on pasture, and the barn area in front of the milking parlor. We performed pulsed-field gel electrophoresis on 237 Streptococcus uberis isolates to identify environmental strains that matched those from mastitis milk. The same strains were detected on the passageway to the pasture, milking parlor waiting area, in one of the liners, and a drinking trough. Streptococcus uberis strains showed high variability within farms and because identical strains (in mastitis milk and environment) were found in different environmental localizations, its transmission appears to be farm specific. Thus, to establish a farm-specific mastitis control strategy, the main environmental sources of Streptococcus uberis must be analyzed for matching strains. A molecular method such as pulsed-field gel electrophoresis is an important tool that can be used to obtain the necessary information.

Longitudinal study of the effects of teat condition on the risk of new intramammary infections in dairy cows.

Machine milking-induced alterations of teat tissue may impair local defense mechanisms and increase the risk of new intramammary infections. The objective of the current study was to assess the influence of short-term and long-term alterations of teat tissue and infectious status of the udder quarter on the risk of naturally occurring new intramammary infections, inflammatory responses, and mastitis. Short-term and long-term changes in teat condition of right udder quarters of 135 cows of a commercial dairy farm in Saxony-Anhalt, Germany, were recorded monthly for 10 mo using simple classification schemes. Quarter milk samples were collected from all examined quarters at each farm visit. Bacteriological culture results and somatic cell counts of quarter milk samples were used to determine new inflammatory responses (increase from ≤100,000 cells/mL to >100,000 cells/mL between 2 samples), new infections (detection of a pathogen from a quarter that was free of the same pathogen at the preceding sampling), and new mastitis (combination of new inflammatory response and new infection). Separate Poisson mixed models for new inflammatory responses, new infections, and new mastitis caused by specific pathogens or groups of pathogens (contagious, environmental, major, minor, or any) were used to estimate risk ratios and 95% confidence intervals. Data preparation and parameter estimation were performed using the open source statistical analysis software R. We observed no effect of any variable describing teat condition on the risk of new intramammary infections, inflammatory responses, or mastitis. Intramammary infections of the same udder quarter in the preceding month did not affect risk either.

E. coli Lipopolysaccharide: acute oral toxicity study in mice.

A single dose of endotoxin (lipopolysaccharide) from a common laboratory cloning and expression strain (Escherichia coli BL21[DE3]) was administered to groups of male and female CD-1 mice (n=5/group) at doses up to 1,000,000 endotoxin units (EU) per mouse by oral gavage. The mice were observed for mortality, body weight effects, and clinical signs for 14 days after which they were sacrificed for gross organ necropsy. All mice survived until the scheduled sacrifice, no clinical signs of toxicity were observed, no test substance-related body weight losses occurred and no gross lesions were present at necropsy. Under the conditions of this study, oral administration of E. coli BL21(DE3) endotoxin to mice at a dose of up to 1,000,000 EU/mouse produced no evidence of toxicity.

Altitude-related illnesses.

Altitude-related illnesses are a frequent cause of morbidity and occasional mortality in travelers to high altitudes in the United States and throughout the world. The primary altitude illnesses are acute mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema. The pathogenesis of these syndromes remains unclear despite considerable research. Altitude also has potential deleterious effects on common medical conditions including coronary artery disease, pulmonary disease, hemoglobinopathies, and pregnancy. Most of these problems are primarily preventable with appropriate information before travel. Education should include information about rate of ascent, diet, alcohol intake, physical activity, and preventive medications, including acetazolamide, nifedipine, and dexamethasone in selected circumstances.

The piglet as an animal model for hypobaric hypoxia.

The objective of this study was to evaluate the piglet as a suitable animal model for human diseases of high altitude. We studied 12 piglets, 4-10 weeks old, in a hypobaric chamber under conditions of high altitude at a pressure of 1/2 atmosphere (to approximately 320 Torr) for various periods of time (12, 24, 36, 48, and 72 hours) with continuous monitoring. The animals were decompressed every 24 hours for grooming and feeding. Two animals were studied as nonexposed controls, and one was studied as a control in the chamber without decompression. The animals were euthanized after the exposure, and a complete autopsy was performed. The tissues were then analyzed with light and electron microscopy. The animals all exhibited clinical features of ataxia, tachypnea with Cheyne-Stokes respiration, and lethargy. One animal vomited. The histologic and ultrastructural analysis showed normal organs, particularly lung and brain. The piglet may be a suitable animal model for the study of high altitude-related diseases in humans, but prolonged uninterrupted exposure and a delay in euthanasia after exposure to high altitude may be necessary for the development of reactive pathologic changes.