Viral and Bacterial Disease Structure

Viral Disease: Structure: Viral diseases are often associated as not living as they do not move and stay on the outside of a hosts cell. They are made up from strands of nucleic acids, these consist of either DNA or RNA, which are surrounded by capsid a protective protein layer. Viral disease can also have a tail section this helps them to move.

-How they grow/reproduce -Impacts of different environmental conditions on their growth/reproduction

Example 1- Canine Parvovirus (CPV) The Canine Parvovirus virus is shed in the faeces of infected dogs within 4-5 days after they have been exposed to the virus, throughout the period of the illness and for 10 days after clinical recovery. Symptoms: Symptoms that are often associated with CPV include being lethargic, showing signs of depression and a loss of appetite. After these symptoms appear, they are followed by an onset of high fever, vomiting and diarrhea, which is more serious in puppies. Transmission: The disease is transmitted via nasal or oral contact with a host or object that is contaminated such as, environment, personnel, equipment, material and faeces. Function: Once inside the dog, CPV uses rapidly dividing cells to successfully cause the disease. The viruses get a ride from the lymphocytes into the bloodstream so they are protected from the host’s defences. Once the virus has entered the bloodstream, it begins to target rapidly dividing cells, hitting hardest in the bone marrow and in the cells that line the walls of the small intestine.

Example 2- Feline Influenza Feline influenza, which is known as the cat flu, is a disease that affects the respiratory tract. Once the influenza is introduced into the respiratory system, it attaches to and replicates in epithelial cells. The virus replicates in both the upper and lower respiratory systems. Symptoms The symptoms associated with Feline Influenza include the cat seeming lethargic, depressed, high temperature, lack of appetite and discharge from the eyes and nose. These symptoms usually appear within 1 to 3 days after the virus has been transmitted. Transmission: The virus is transmitted through an infected cat. The virus is transmitted through the infected cat coughing and sneezing which releases the virus into the air meaning direct physical contact is not required. However, through direct physical contact with an infected cat the virus can lead to an infection. Function: Once the influenza is introduced into the respiratory system, it attaches to and replicates in epithelial cells. The virus replicates in both the upper and lower respiratory systems. Viral replication combined with the immunes responses to the infection causes the destruction and loss of cells lining the respiratory system. When the virus infects respiratory epithelial cells, it is detected by receptors. These receptors produce and activate antiviral responses. However, the virus can escape these antiviral responses by using NS1 (non-structural protein which stops the production of the antiviral responses- interferon synthesis). This allows the virus to overcome the cats defense systems.

Bacterial Disease: -Structure -How they grow/reproduce -impacts of different environmental conditions on their growth/reproduction

Example 1- Salmonella Salmonella is a type of bacteria that affects the stomach and intestines by attacking them causing food poisoning. Symptoms: The symptoms associated with salmonella include, diarrhoea, vomiting and will also cause abdominal pain 12 to 72 hours after the infection has taken place. Transmission: Salmonella is transmitted through the ingestion of contaminated foods. It can also be transmitted through food handlers. The bacteria contaminate the food which is then ingested into the body. Function: Salmonella is a type of bacteria that affects the stomach and intestines by attacking them causing food poisoning. Salmonella starts by invading the hosts healthy tissues. It then begins to reproduce and colonies in the stomach and intestines. It produces substances known as extracellular substances which helps with the reproducing and colonising. This gives the bacteria as chance to conquer the natural defenses of the host.

Example 2- Bordetella Bordetella is also known as kennel cough (infectious canine tracheobronchitis). It’s a highly contagious respiratory disease amongst dogs. Puppies often suffer the most serious complications as a result of this contagious disease due to their immature immune system. Dogs often develop symptoms associated with Bordetella (kennel cough) 3-4 days after they have been exposed to it (e.g., from boarding kennels and shows. Symptoms: Symptoms associated with Bordetella include, coughing, retching and nasal discharge. In some cases, dogs are still active and eating normally. However, in severe cases of Bordetella symptoms can get worse casing, pneumonia, fever, lethargy and can even cause death. Transmission: Bordetella can be transmitted via direct contact with a dog caring the bacterial disease, it can also be transmitted through respiratory aerosol droplets or fomites. Function: Bordetella is a type of bacteria that attacks the respiratory system. The bacteria start off by multiplying and spreading deeper into the respiratory system. Toxins are released which remove the effectiveness of cilia, this allows the bacteria to enter the body. One of the toxins released is known as tracheal cytotoxin. Tracheal cytotoxin paralyses the cilia and stops DNA synthesis in epithelial cells (a type of cell that line the surface of the body) and will kill the epithelial cells. Another toxin released is known as adenylate cyclase, this toxin helps by attacking innate immunity. This then stops the functions of immune cells.