Pathogens Part 1

Pathogens Think about it: • What sicknesses have you had? • Can you name an infectious disease that causes people or animals to die? • What is an infectious disease that has been in the news recently? Epidemiology • The branch of medical science dealing with the transmission and control of disease. • There are human physicians that study epidemiology and also veterinarians that study animal epidemiology. Both of these types of epidemiologists also deal with diseases that are transmitted from humans to animals and from animals to humans. Infectious Diseases are Caused by Pathogens What’s a pathogen? What are Pathogens? • Pathogens are microbes (microscopic living organisms) or other agents that cause diseases. • Example: Foot and mouth disease is a highly contagious disease of cattle, swine, and other cloven-hoofed animals. – It is caused by a viral pathogen called picornavirus. – It causes blisters in the mouths and hooves of animals. Not all microbes are pathogens • There are many types of microbes that are actually beneficial to animals. • Examples include the symbiotic bacteria found in the digestive system of cattle and horses that help them digest cellulose in roughage. • There can be one trillion or more microbes in 1 ounce of rumen fluid from a cow!* Common Types of Pathogens Viruses Bacteria Fungi Prions Protozoa A Closer Look at the types of Pathogens: Bacteria • Bacteria are single celled organisms that are prokaryotic. • There are countless numbers of bacteria on the Earth but less than 1% of them cause diseases. • Bacterial infections make an animal noticeably sick. • Bacteria reproduce rapidly and many give off toxins which damage body tissue. Bacteria are shaped like cocci (spheres), bacilli (rods), or spirilla (spirals). Bacteria • Symptoms of bacterial infections depend on the type of bacteria but can include fever, pain, swelling, vomiting, diarrhea, formation of pus, and even abortion. • Body fluids can be sampled and cultured to grow and identify the bacterial pathogen. • Antibiotics are the usual treatment for bacterial infections, but treatment can vary. Strangles in horses is caused by Streptococcus equi bacteria A positive culture for Streptococcus bacteria • Bacteria adapt quickly and may become resistant to antibiotics. A broad spectrum antibiotic Common Bacterial Diseases Disease Body System Symptoms Examples Dermatitis Skin Inflammation, pruritus (itching) skin lesions (bumps, blisters, scales, crusts) Staphylococcus aureus Pyoderma Skin Purulent exudate (pus) from skin lesions Staphylococcus intermedius Keratocunjunctivitis Eye Inflammation of cornea and conjunctiva , pain, sensitivity to sunlight, tears, squinting “Pinkeye” is common name Staphylococcus aureus Otitis Externa Ear Inflammation of external ear canal with reddening, drainage and itching Staphylococcus Rhinitis and Sinusitis Respiratory Inflammation of the membranes of the nasal passages and sinuses. Mucus nasal discharge, open-mouth breathing, sneezing. Strangles in horses caused by Streptococcus equi Pneumonia Respiratory Deep cough and difficulty breathing Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), Streptococcus species Gastroenteritis Digestive Inflammation of stomach and intestines, excessive salivation, vomiting, diarrhea, straining, abdominal pain. Salmonellosis, colibacillosis, eneterotoxemia Metritis Reproductive Inflammation of uterus. Purulent vaginal discharge, abortion, premature birth. Contagious Equine Metritis (CEM) Abortion Reproductive Premature birth (expelling) of fetus by pregnant female. Brucellosis, leptospirosis and camphylobacteriosis (vibriosis) Mastitis Reproductive Inflammation of mammary gland or udder tissue. Swollen, warm and painful mammary glands. Pseudomonas aeruginosa and many other bacteria Anthrax Skin, Digestive, Respiratory Sudden death in cattle Varied in humans depending on exposure method Bacillus anthracis is reportable disease responsible for outbreaks in cattle. Zoonotic, possible bioterrorism agent