In the United States around 1890-1910, How were these diseases treated by pioneers traveling west?

Question

Cholera
Quinsy
Malnutrition

Answer 1

The death rate for each of these conditions was astronomical compared to modern medicine.

Cholera is a diarrheal illness, and the danger to life is dehydration, so attempts were made to get them to drink water.

Quinsy is a peritonsilar abscess, and the danger is impediment to the airway. Various liquids and snake oils were tried, but time and the body's own immune system were the only reliable cures.

Malnutrition was not understood in the same way that it is today, and there were various snake oils that purported to "cure" the ailments associated with malnutrition, or with the vitamin deficiencies associated with it.

In short, nothing that would be considered mainstream today.
BTW, none of the diseases you have inquired about even come close to a description or symptoms of bubonic plague.

Answer 2

I think that one of them wuz "The Bueboneck peag"