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A highly fatal insect-borne viral disease of horses and mules, and a mild, subclinical disease in donkeys and zebras. African horse sickness occurs in sub-Saharan Africa, but incursions outside Africa have been documented. Dogs may be affected by…

An age-contingent reduction in physiological function and activity, with a concomitant increase in mortality rate and a diminution in reproductive rate. Aging is the process of becoming older, which is influenced by genetic and environmental…

The repeated and/or excessive use of alcohol (ethanol) that continues despite negative physical, psychiatric, or social consequences. Alcoholism is characterized by consuming alcohol more often, in larger amounts, or over longer periods than…

Altered reactivity in humans and other animals to allergens (substances foreign to the body that trigger an allergic response) induced by exposure through injection, inhalation, ingestion, or skin contact. An allergy (or allergic reaction; Fig. 1)…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

An alloy of mercury. Practically all metals will form alloys, or amalgams, with mercury, with the notable exception of iron. Amalgams are used as dental materials (see illustration), in the concentration of gold and silver from their ores, and as…

Any of the organic compounds possessing one or more basic amino groups and one or more acidic carboxyl groups. Of the more than 80 amino acids that have been found in living organisms, approximately 20 serve as the building blocks for proteins.…

A stimulating drug that affects the brain and the body. Amphetamine is a stimulant of the central nervous system. Chemically, amphetamine is a racemic mixture of the l and d isomers of α-methyl-β-phenethylamine (see illustration). The l isomer has…

A disorder characterized by the accumulation of an unusual extracellular fibrous protein (amyloid) in the connective tissue of the body. The deposition of amyloid may be widespread, involving major organs and leading to serious clinical…

An infection caused by anaerobic bacteria (organisms that are intolerant of oxygen). Most anaerobic infections are mixed, involving more than one anaerobe and often aerobic or facultative bacteria as well.Bacteria InfectionAnaerobes are prevalent…