From a horse owner standpoint, says Weese, the key concern is about pathogens developing resistance in the horse and becoming more difficult to treat. | Photo: Anne M. Eberhardt/The Horse

There’s an “anti” for almost everything. Here’s a rundown on our arsenal of equine disease-fighting drugs and their proper uses.

Humans have been waging war against the soldiers of disease for hundreds of years, long before fabled scientist Antonie van Leeuwenhoek first discovered these tiny organisms under a microscope. In fact, in March 2015 a team of biologists and medieval scholars at the University of Nottingham uncovered a 10th century recipe for antibacterial eye ointment. After recreating the salve, they confirmed their predecessors in the laboratory were on to something—the concoction was effective against today’s methicillin-resistant Staphylococcus aureus (MRSA), bacterial species that earned their name because of broad resistance to most modern drugs.

Indeed, the battle with pathogens, or agents of disease, continues today, but current mainstays of the human-led arsenal in the disease wars are an array of “anti” drugs, which include antimicrobials (more commonly called antibiotics), antivirals, antiparasitics, and antifungals. These are designed to fight enemies that use guerrilla-type tactics against the horse’s immune system—targeting its weaknesses and adapting quickly to changes in the environment.

The Enemy

Different pathogens cause similar signs of disease. Bacteria, viruses, and fungi, for instance, can all cause nasal discharge, while bacteria, parasites, protozoa, and viruses can all cause diarrhea. However, each pathogen is a unique organism carrying its own strengths and weaknesses into battle. Recognizing the ploys of each—and applying proper treatment—can mean a more successful outcome