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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. Growth and reproduction: The virus starts by attaching itself to a host cells surface, the virus uses this host cell to reproduce. The virus the releases nucleic acid into the host cell a genetic material. The nucleic acid then takes control over the host cells. The host cell then uses the nucleic acid to help create more viruses.

Once the new viruses have been produced the host cell opens releasing all the new viruses.  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:   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.        Fungal Disease:  Example 1- Aspergillus spp. Aspergillus is a type of species of fungus (mold) that is found in the environment for example in, dust, straw, cut grass, and hay. It occurs when an animal is infected by an organism that doesn’t usually cause any diseases. Symptoms: The symptoms associated with Aspergillus. Include, sneezing, nasal pain, loss of appetite, bleeding from nasal area, inflamed nose, nasal discharge containing mucus or blood.

 Transmission: There are two types of Aspergillus, the first type is spread through the nasal passage, which is transmitted through direct nasal and sinus contact with the fungus. The second type of Aspergillus, is spread throughout the body or organ, which there is no certain way in which this fungus enters the body. Once the fungus enters the body it uses the hosts blood stream to spread throughout the hosts body.   Function: Aspergillus is a type of species of fungus that is found in the environment for example in, dust, straw, cut grass, and hay. Aspergillus is a type of mold that appears on infected animals mostly around there nasal and sinus areas.

It occurs when an animal is infected by an organism that doesn’t usually cause any diseases. Meanwhile for Aspergillus, the fungus occurs when an animal’s immune system has been weekend by other diseases.       Example 2- Microsporum Canis (M.

 Canis) M. Canis usually affects dogs, cats, and other mammals and can even affect humans. It is known as a pathogenic fugus that affects the top layer of dead skin. Spores will produce and will attach themselves to the skin and grow, this produces hyphae a structure in the fungus that will then grow in the skin, nails and hair. Symptoms: The symptoms associated with M. Canis include, red skin, poor coat, dandruff, scratching, blisters and hair loss. The animals skin may also appear raised or bumpy. Transmission: M.

 Canis is very contagious and is easily spread fungus that has two different ways of being transmitted, the first is through direct contact with the fungus. The second way of transmission is through indirect contact with a material holding or containing the fungus.                                                                                  Function: M. Canis is known as a pathogenic fugus that affects the top layer of dead skin, this fugus usually infects dogs, cats, other mammals and sometimes humans if they come into direct contact with the fugus.

M. Canis infects the scalp and other body sites creating an area that is inflamed and results to hair loss. The animal’s natural immune systems are usually able to get rid of the fungus. However, when a dog has been put on medication or already has a disease they cannot fight the fungus by themselves as their immune systems are weaker.

     Parasites:   Example 1- Ticks Ticks are a small parasite. Known as arachnids, they feed on blood from a host, and are found worldwide, they can be found in woodlands and grasslands. Ticks infect a variety of animals but mostly infect mammals. Ticks drink blood from the host which weakens them, however the biggest problem with ticks is that some ticks are infected with diseases, an example of a disease carried by ticks is tick-borne disease.   Symptoms: Symptoms associated with ticks include, pain and swelling by the bite location, rash, blisters, burning sensation by the bite location, and in severe cases can cause breathing difficulties. Transmission: Ticks are transmitted through direct contact.

 This is because ticks cannot fly or jump so they wait for a host to pass by then they latch on. The tick then gets to the surface of the skin and uses their palps to get their head into the host, they then begin to drink the blood of the host.  Function: Ticks are a small parasite.

Known as arachnids, they feed on blood from a host, and are found worldwide, they can be found in woodlands and grasslands. Ticks drink blood from a host animal. However, the biggest problem with ticks is that some of the ticks can be infected with diseases, an example of a disease carried by ticks is, tick-borne disease. These diseases can ne life threatening.    Example 2- Fleas Fleas are a small external parasite. They drink blood from a host that they land on Symptoms: Symptoms associated with flea bites include, scratching/ itching, redness, blisters, and the area of bite will become inflamed.

People may also become very sensitive to a bite from a flea. In addition, secondary infections are also common from flea bites due to the scratching and itching of the area. Legs and feet are commonly the most attacked. 

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