Physical barriers and the immune system defend an animal’s body against organisms that can cause disease. Physical barriers include outer coverings, such as skin, fur, feathers, and scales. Additional barriers include the mucous membranes, tears, ear wax, mucus,
Microorganisms are tiny living creatures, such as bacteria, fungi, and viruses. Microorganisms are present everywhere. Despite their overwhelming abundance, relatively few of the hundreds of thousands of species of microorganisms invade, multiply, and cause illne
Although not a test or imaging procedure, radiation therapy is discussed here because, like several imaging techniques, it uses ionizing radiation and is typically done under the direction of a veterinary radiologist. In veterinary practice, this treatment is ver
Viruses are much smaller than fungi or bacteria, and they must invade a living cell to reproduce, or replicate. The virus attaches to a cell, enters it, and releases its DNA or RNA inside the cell. The DNA or RNA of the virus is its genetic information, which tak
A parasite is an organism that lives on or in another organism (usually referred to as the host), causing harm to the host. Parasites enter the body most often through the mouth or skin. Parasites that enter through the mouth are swallowed and can either remain
Rickettsiae are an unusual type of bacteria that cause several diseases, including Rocky Mountain spotted fever. Rickettsiae differ from most other bacteria in that they can only live and multiply inside the cells of another organism (host) and cannot survive on
A wide range of dosage formulations and delivery systems has been developed to provide for the care and welfare of animals. Using the correct dosage is very important in terms of effectiveness and safety. Drug treatment and delivery strategies can be complicated
If your pet has been diagnosed with a condition or disease that can be managed or cured, your veterinarian will discuss treatment options. He or she will recommend drugs that are necessary, safe, and effective for both the individual animal and the specific disor
The zoonoses table in the Public Health section of the professional version of the MSD Veterinary Manual lists the most important zoonoses that have been documented. Many of these are quite rare and only occ