Long-term acute infections during a bovine viral diarrhea virus (BVDV) outbreak in dairy farm from Galicia (NW Spain).

An observational study describes an outbreak of bovine viral diarrhea virus (BVDV) in a dairy herd in Spain. The herd was subjected to a voluntary control program. In a sampling carried out in June 2020, bulk tank milk antibody levels increased compared to the previous sampling. Additionally, serum samples from 4 young heifers also tested positive for antibodies. Since the results were consistent with a recent infection, we proceeded to detect possible persistently infected (PI) animals using antigen ELISA (on serum/ear-notch samples), following the program guidelines. From this moment on, 42 animals tested positive for BVDV antigen, of which 17 were under typical acute infection (AI), 13 were deemed as PI, and eight died early on the farm before having information to determine their status. The remaining 4 showed intriguing test results consistent with a long-term AI since they tested BVDV positive in at least two antigen tests more than 3 weeks apart. Thus, one animal was positive until 80 days of age in serum, and others even for longer periods in ear-notch samples, until they finally tested negative for BVDV. Based on these results, longer follow-up may be necessary in BVDV positive animals to accurately confirm persistent infection.

Relativistic statistical thermodynamics of dense photon gas.

We discuss some aspects of interactions of high-frequency electromagnetic waves with plasmas, assuming that the intensity of radiation is sufficiently large, so that the photon-photon interaction is more likely than the photon-plasma particle interaction. In the stationary limit, solving the kinetic equation of the photon gas, we derive a distribution function. With this distribution function at hand, we investigate the adiabatic photon self-capture and obtain the number density of the trapped photons. We employ the distribution function to calculate the thermodynamic quantities for the photon gas. Having expressions of the entropy and the pressure of the photon gas, we define the heat capacities and exhibit the existence of the ratio of the specific heats Gamma , which equals 7/6 for nonrelativistic temperatures. In addition, we disclose the magnitude of the mean square fluctuation of the number of photons. Finally, we discuss the uniform expansion of the photon gas.