prairie chicken: see grouse.

chicken pox or varicella, infectious disease usually occurring in childhood. It is believed to be caused by the same herpesvirus that produces shingles. Chicken pox is highly communicable and is characterized by an easily recognizable rash consisting of blisterlike lesions that appear two to three weeks after infection. Usually there are also low fever and headache. When the lesions have crusted over, the disease is believed to be no longer communicable; however, most patients simultaneously exhibit lesions at different stages of eruption. Chicken pox is usually a mild disease requiring little treatment other than medication to relieve the troublesome itching, but care must be taken that the rash does not become secondarily infected by bacteria. Pneumonia and encephalitis are rare complications. A vaccine for chicken pox was approved for use in the United States in 1995. The drug acyclovir may be used to treat the disease, particularly in older patients.

chicken: see poultry.

Rhode Island Red chicken, American breed of poultry, no longer raised commercially, but still maintained for use in breeding programs. See Red Rock chicken.

Red Rock chicken, the only chicken still popular to any large extent in the United States today for both meat and eggs. It resulted from a cross between a Rhode Island Red male and a Plymouth Rock female. The breed recently acquired new value when it was discovered that the sex of the day-old chicks could be determined by the differences in the color of their down. The variety is raised primarily in New England.

Plymouth Rock chicken, one of the most popular early breeds of poultry. The Barred Plymouth Rock was a favorite farm chicken since it was both a good egg producer and also developed a large quantity of meat. As the demand for white eggs increased, the breed lost popularity. It is still retained for breeding purposes, a popular cross being that of a Barred Plymouth Rock female and a Rhode Island Red male. See Red Rock chicken.

New Hampshire chicken, dual-purpose breed of poultry that is no longer grown commercially. It is retained for its genetic input into modern breeding programs.

Mother Carey's chicken: see petrel.

Leghorn chicken, relatively small, white-colored breed of poultry that currently dominates the American egg-producing class. The bird, as bred today, produces a good number of chalk white eggs, a feature which has brought it to the forefront of modern commercial egg production. Although only the "single comb" variety is popular today, many other strains with large egg, better shell, better interior egg qualities, or other desirable traits, are retained as breeding stock.

or varicella

Contagious viral disease producing itchy blisters. It usually occurs in epidemics among young children, causes a low fever, and runs a mild course, leaving patients immune. The blisters can scar if scratched. The virus that causes chickenpox (varicella-zoster virus) can reactivate years later, causing shingles. Zoster immune globulin (ZIG) can prevent chickenpox in children with leukemia or immunodeficiency disorders who are exposed to the virus. A vaccine has also been developed.

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