Applications of phage therapy in veterinary medicine

Abstract: This paper describes some different investigations of phage therapy within veterinary medicine, in treating some of the most common bacterial infections in poultry, cattle and fish. As a red thread, phage therapy is being compared and contrasted with the current standard antibiotic treatment within some common diseases, as well as in general, in the discussion section. Bacteriophages, also known simply as phages, are bacterial (obligate) parasites or viruses that infect, replicate inside and eventually lyse their host bacterium, letting out hundreds of new phages. Since phages depend on bacteria as their host, they can be used for therapeutic purposes to help the immune system against the pathogens by killing the bacteria. Salmonellosis is caused by Salmonella bacteria and it is one of the most common and important infections transmitted between animals and man (zoonosis). Salmonella phages proved very effective in treating mice and chicken infected with Salmonella with a success rate of 90-100% (Lenev, 2013). Treatment of rabbits infected with Vibrio cholera by phages did not provide any successful results on the rabbit models, in contrast to the successful trial of treating cholera in humans. This is one of the examples how the effect of phage therapy application can vary within different species. Phages have shown to be effective against Enterococcus in mice models, with the pathogen’s significant decrease under infective dose; however, a tendency has been found that the earlier the treatment started the better result was obtained. When tested against Clostridium difficile, phages were able to protect the mice models from the disease but the effect did not endure for long. In all the different trials, it remains important to neutralise the gastric acid before administering phages orally, since low pH deactivates them. In the aquatic sphere, the two principle diseases have been taken up – aeromonosis and pseudomonosis, where phage therapy is still in the mode of trial, but already suggested by some researchers (Kafydova and Grinyova, 2014) to be used for treatment. Phage therapy has shown significant effects on Pseudomonas pleoglossicida, and a very promising result has been demonstrated on the Lactococcus bacteria, with maximal success and absolute protection of fish against the pathogen.