Animal Viral Diseases


Ebola hemorrhagic fever (Ebola HF) is a severe, often-fatal disease in humans and non-human primates (monkeys, gorillas, and chimpanzees).

A notoriously deadly virus causing fearsome symptoms, the most prominent being high fever and massive internal bleeding. Ebola virus kills as many as 90% of the people it infects. It is one of the viruses that is capable of causing hemorrhagic (bloody) fever.

The initial symptoms are usually high fever, headache, muscle aches, stomach pain, and diarrhea. There may also be sore throat, hiccups, and red and itchy eyes. The symptoms that tend to follow include vomiting and rash and bleeding problems with bloody nose, spitting up blood from the lungs and vomiting it up from the stomach, and bloody eyes (conjunctival hemorrhages). Then finally come chest pain, shock, and death.
A protein on the surface of the virus has been discovered that is responsible for the severe internal bleeding (the death-dealing feature of the disease). The protein attacks and destroys the endothelial cells lining blood vessels, causing the vessels to leak and bleed.

The incubation period –the period between contact with the virus and the appearance of symptoms – ranges from 2 to 21 days.

There is no specific treatment for the disease. Currently, patients receive supportive therapy. This consists of balancing the patient’s fluids and electrolytes, maintaining their oxygen level and blood pressure, and treating them for any complicating infections. Death can occur within 10 days of the onset of symptoms.

The prevention of the spread of Ebola fever involves practical viral hemorrhagic fever isolation precautions, or barrier nursing techniques. These techniques include the wearing of protective clothing, such as masks, gloves, gowns, and goggles; the use of infection-control measures, including complete equipment sterilization; and the isolation of Ebola fever patients from contact with unprotected persons. The aim of all of these techniques is to avoid any person’s contact with the blood or secretions of any patient. If a patient with Ebola fever dies, it is equally important that direct contact with the body of the deceased patient be prevented.

The exact origin, locations, and natural habitat (known as the “natural reservoir”) of Ebola virus remain unknown. However, on the basis of available evidence and the nature of similar viruses, researchers believe that the virus is zoonotic (animal-borne), with 4 of the 5 subtypes occurring in an animal host native to Africa. A similar host, most likely in the Philippines, is probably associated with the Ebola-Reston subtype, which was isolated from infected cynomolgous monkeys that were imported to the United States and Italy from the Philippines. The virus is not known to be native to other continents, such as North America.

Infection with Ebola virus in humans is incidental – humans do not “carry” the virus. The way in which the virus first appears in a human at the start of an outbreak has not been determined. However, it has been hypothesized that the first patient becomes infected through contact with an infected animal.

After the first case-patient in an outbreak setting is infected, the virus can be transmitted in several ways. People can be exposed to Ebola virus from direct contact with the blood and/or secretions of an infected person. Thus, the virus is often spread through families and friends because they come in close contact with such secretions when caring for infected persons. People can also be exposed to Ebola virus through contact with objects, such as needles, that have been contaminated with infected secretions.



People who are most at risk for developing viral hepatitis are workers in the health care professions, people with multiple sexual partners, intravenous drug users, and hemophiliacs who receive blood clotting factors. Blood transfusion, once a common means of spreading viral hepatitis, now is a rare cause of hepatitis.

Hepatitis means inflammation of the liver. There are several hepatitis viruses; they have been named types A, B, C, D, E, F (not confirmed), and G.

The most common signs are flu- like symptoms including loss of appetite, nausea, vomiting, fever, weakness, tiredness, aching in the abdomen. Less common symptoms include dark urine, light-colored stools, fever, jaundice.

Common types of viral hepatitis

  • Hepatitis A

The hepatitis caused by HAV is an acute illness (acute viral hepatitis) that never becomes chronic. Infection with hepatitis A virus can be spread through the ingestion of food or water, especially where unsanitary conditions allow water or food to become contaminated by human waste containing hepatitis A (the faecal-oral mode of transmission).


  • Hepatitis B

About 6-10% of patients with hepatitis B develop chronic HBV infection (infection lasting at least six months and often years to decades) and can infect others as long as they remain infected. Patients with chronic hepatitis B infection also are at risk of developing cirrhosis, liver failure and liver cancer.


  • Hepatitis C

An estimated 50-70% of patients with acute hepatitis C infection develop chronic HCV infection. Patients with chronic hepatitis C infection are at risk for developing cirrhosis, liver failure, and liver cancer.

The incubation period varies depending on the specific hepatitis virus. Hepatitis A has an incubation period of about 15-45 days; hepatitis B from 45-160 days, and hepatitis C from 2 weeks to 6 months.
The prognosis of viral hepatitis for most patients is good. Symptoms of viral hepatitis such as fatigue, poor appetite, nausea, and jaundice usually subside in several weeks to months, without any specific treatment. Virtually all patients with acute infection with hepatitis A and most adults (greater than 95%) with acute hepatitis B recover completely. However, not all patients with viral hepatitis infections recover completely. Five percent of patients with acute hepatitis B infection and 80% of patients with acute hepatitis C infection develop chronic hepatitis.

Treatment of acute viral hepatitis and chronic viral hepatitis are different. Treatment of acute viral hepatitis involves relieving symptoms and maintaining adequate intake of fluids. Treatment of chronic viral hepatitis involves medications to eradicate the virus and taking measures to prevent further liver damage.

Prevention of hepatitis involves measures to avoid exposure to the viruses, using immunoglobulin in the event of exposure, and vaccines. Administration of immunoglobulin is called passive protection because antibodies from patients who have had viral hepatitis are given to the patient. Vaccination is called active protection because killed viruses or non-infective components of viruses are given to stimulate the body to produce its own antibodies.

Hepatitis A typically is spread among household members and close contacts through the passage of oral secretions (intimate kissing) or stool (poor hand washing). It also is common to have infection spread to customers in restaurants and among children and workers in day care centres if hand washing and sanitary precautions are not observed.

Hepatitis B can be spread by sexual contact, the transfer of blood or serum through shared needles in drug abusers, accidental needle sticks with needles contaminated with infected blood, blood transfusions, hemodialysis, and by infected mothers to their newborns. The infection also can be spread by tattooing, body piercing, and sharing razors and toothbrushes (if there is contamination with infected blood).
The hepatitis C virus (HCV) usually is spread by shared needles among drug abusers, blood transfusion, hemodialysis, and needle sticks. Approximately 90% of transfusion-associated hepatitis is caused by hepatitis C. Transmission of the virus by sexual contact has been reported, but is considered rare. Patients with chronic hepatitis C infection can continue to infect others.



Tyzzer’s disease is an illness that can cause cell death in the liver and intestinal tract of many small mammals including rabbits, guinea pigs, hamsters, and gerbils. It has also been reported less commonly in rats, mice, cats, dogs, and horses.

Tyzzer’s disease is caused by the bacteria, Clostridium piliforme (C. piliforme), formerly called Bacillus piliformis. C. piliforme lives in the intestine. Animals with Tyzzer’s disease often have watery diarrhoea, staining around the anal area, depression, dehydration, lethargy, and scruffy hair coats. It is more frequently and likely to cause acute death (within 48 hours of the first signs) in young animals or those stressed by overcrowding, poor hygiene, extreme environmental temperatures and humidity, parasitic infections, or malnutrition.

There is no specific therapy that will kill C. piliforme, although tetracycline is often administered. Treatment is generally aimed at supportive care including fluids, good nutrition, and providing the optimal temperature and humidity. In young and stressed animals, treatment is usually unsuccessful.

Conditions that cause stress should be avoided, especially in young animals during weaning. Extreme care should be taken to assure animals have a proper environment, diet, and treatment of any parasitic infections. Healthy animals should be separated from any animals showing signs of the disease. There is no vaccine for Tyzzer’s disease. The bacteria and spores can be killed using a 1:10 dilution of household bleach and water (½ cup of bleach to 5 cups of water).

It is spread from animal to animal through faecal contamination of food and water. The bacteria can produce spores, which can survive for years in the environment, and are very resistant to heat and many disinfectants. The spores are shed in the faeces of infected animals.


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