Viruses may infect all cells and each cellular organism has its own specific range of viruses that often infect only that species. Some viruses in addition can replicate only in cells that have been taken over by other viruses. These are called satellites or parasites of other viruses.
Viruses affecting animals and livestock
Viruses are important pathogens of livestock. Common infections include Foot and Mouth Disease and bluetongue etc.
Pets like cats, dogs, and horses are also susceptible to serious viral infections. For example, dogs may be affected by rabies, canine parvovirus infections (fatal to puppies) etc.
Honey bees used in agriculture may also be susceptible to many viral infections.
Birds may also be affected by viral infections and notable among these that may be transmitted to humans as well includes the bird flu or avian flu. Flu virus may also be transmitted from pigs to humans and is termed swine flu.
Other infections in animals and livestock include:
- viral pneumonia in pigs
- infectious atrophic rhinitis or rhinotrachitis in pigs
- myxovirus parainfluenza of cows
- keratoconjunctivitis (viral eye infections) of cows
- polio-encephalomyelitis virus infections or gastrointestinal infections of pigs
- transmissible gastroenteritis of pigs
- Beran’s swine enterovirus infections
- Foot-and-mouth disease
Horses may be affected by the Hendra virus that is highly contagious and fatal.
Viruses affecting plants and crops
Plant viruses are harmless to humans and other animals because they can reproduce only in living plant cells. Most plants have resistance genes that protect them against viruses. Each R gene confers resistance to a particular virus. The gene triggers death of the cells around the affected area. This stops the infection from spreading.
When they are infected, plants often produce natural disinfectants that kill viruses. This includes nitric oxide, salicylic acids and reactive oxygen molecules.
Viruses affecting bacteria
Viruses affecting bacteria are the Bacteriophages. These are the most common and the most diverse group as well as the most abundant form of biological entity in water environments. There are up to ten times more of these viruses in the oceans than there are bacteria.
Bacteriophages infect specific bacteria by binding to surface receptor molecules and then entering the cell. The bacterial polymerase enzyme then starts to translate the virus RNA into protein. These proteins go on to become either new virions within the cell that helps in assembling the new virions, or proteins involved in cell lysis.
The cell is broken down within twenty minutes after injection releasing over 300 new bacteriophages.
Viruses affecting arachea
Some viruses replicate within archaea. These are usually double stranded DNA viruses. They may have unique shapes.