I see horses literally every day of my life (which is why it’s so important to keep lifestyle in mind) also that’s far from the only place one can get tetanus and yes you can opt out of the TDAp and request a straight tetanus vaccine. The pertussis vaccine came out in 1914, the combo vaccine was available in the 1940s so the decline in the disease points to the success of the vaccine not a lack of a need for it.