Cattle, sheep diseases

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC95770/

Schmallenberg_virus still fits the speculation. However I was also mistaking it for the above.
Note how little is known about these viruses, a common factor.

Caring

When one is approaching irreversible infirmity, there should be the option of euthanasia.
Not at all in a matter of fact way, however. Departure locations should be established where a form of life and work can be known, where the departing can reside, be engaged by those living, having worked, or knowing the life, there.