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horse shoe                                                        Terms and Definitions:

Acute:  a disease whose clinical signs develop quickly, opposite from chronic disease, which develops over a long period of time, where the symptoms progressively worsen.
Acyclovir:  this is an antiviral drug that acts on the transcription step during virus infection and replication.

Ataxia:  neurological sign meaning loss of balance, loss of limb coordination resulting in a staggering wobbly gait.  This symptom is observed for a variety of disorders, mainly neurological in origin.
Attenuated Live:  virus that has been rendered non-virulent due to repeated passage through cellular cultures where the virus has adapted to other conditions such as temperature.  Attenuated viruses are used in vaccines and can cause disease in some cases (fetus, newborn).
Conjunctivitis:  inflammation of the conjunctiva, which is the membrane which covers the front of the eye and lines the insides of the eyelids of all animals.
Deletion Mutant:  some of the viral DNA is deleted producing a less virulent viral strain capable of eliciting a more protective immune response in the host, used in vaccination.
Endothelial cells:  cells lining the blood vessels of the body
Immunoprophylaxis:  immunizing animals to prevent or protect against viral infection, could be compared to the prophylactic administration of antibiotics in order to prevent bacterial infection. 
Inactivated vaccine:  virus is unable to infect cells and is used in vaccination to elicit an immune reaction and confer immunity to the true pathogen. 
Inclusion bodies: 
morphological change due to viral replication within an infected cell seen histologically.   Each  virus has a  characteristic inclusion body, which aids in diagnosis of the specific viral pathogen. 
Incubation period:  the time required for infection to result in clinical signs of disease, in the case of EHV-1 it is the time required for infection to result in abortion, respiratory signs or neurological signs.
Ischemia:  when blood flow is cut-off to an area of tissue, that tissue undergoes "ischemic damage" due to impaired delivery of nutrients and oxygen, leading eventually to cell death, also called ischemic necrosis.  In this case the impaired blood flow is due to blood clot formation in blood vessels servicing that tissue. 
Latent Infection:  where a virus is not completely eliminated from a host's body, but actually remains dormant or sequestered in certain tissues, namely sensory neurons and lymphoid cells for EHV-1.  This latent infection has the potential to cause disease again if the host becomes stressed and its immunological defenses become compromised, and the virus can become reactivated causing the reoccurence of disease.  A herpesvirus infection is carried by a host for life after the initial infection, for example a cold sore is a herpes virus. 
Leukocytes:   white blood cells found in the blood and lymphoid tissue.
Modified live:  attenuated vaccines are an example of this, any virus whose virulence and disease causing nature has been altered in order for use in vaccination to confer immunity but not infection. 
Necrosis:  tissue death usually accompanied by inflammation; within the CNS this is termed malacia, which is a form of liquifactive necrosis where the necrotic or dying tissue actually appears to be liquid in consistency and texture. 
Thrombus:  blood clot, occurs in this case when blood vessels are damaged causing platelets to adhere to the damaged endothelium and clotting factors are activated.
Vascular Necrosis:  death to the tissues composing the blood vessels (endothelial cells mostly, due to infection)
Vasculitis:  an inflammation of the blood vessels, usually the result of infection of the endothelial cells.
Viral Antigens:  proteins projecting from the surface of a virus which are recognized and bound by antibodies  produced by the body's immune system to generate protection and immunity to viral infection. 
Viremia:  virus in the blood, either free virus or intracellular (within cells).
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