Antibiotics are drugs used to treat infections caused by bacteria, which are tiny organisms that can sometimes cause illness to humans and animals.
- Some bacteria are harmless, and are good for us, such as those in a pet’s intestines helping digest food.
- Antibiotics target microorganisms such as bacteria, fungi and parasites but are not effective against viruses.
That’s why a vet will not prescribe antibiotics for a viral infection such as canine parvovirus. However, sometimes the weakened virus-infected pet may succumb to a secondary bacterial infection.
For example, cat flu (Feline Upper Respiratory Disease) is a very infectious disease caused by two viruses. Initially, the affected cat sneezes a lot, and has runny eyes and nose. The cat may then go off its food, with a fever and general depression. The eyes and nose can become ulcerated. The affected cat may salivate excessively, cough and lose its voice. A secondary bacterial infection can result in a very thick nasal and eye discharge.
- Pets as well as humans have special white blood cells that are triggered by harmful bacteria.
- These cells eat the bacteria and destroy them, which often means that any infection is fought off. Sometimes these white blood cells get overwhelmed and need some help – that’s where antibiotics come in.
- There are lots of different antibiotics but they work in two ways.
- They either kill the bacteria or they stop them from multiplying.
- They can be broad spectrum where they work against lots of different types of bacteria or narrow spectrum where they are effective against only a few types.
- If antibiotics are overused or used incorrectly there is a chance that the bacteria will become resistant – the antibiotic becomes less effective against that type of bug.
- Antibiotics are not completely powerless against resistant bacteria, but patients may need a much higher dose over a longer period or an alternative antibiotic to which the bacteria have less resistance.
Author – Elaine Pendlebury BA BSc BVetMed DMS MRCVS Senior Veterinary Surgeon (Science & Welfare) PDSA