(ong″kŏ-sĕr′kă) [Gr. onkos, barb (of an arrow) + Gr. kerkos, tail] A genus of filarial worms that live in the subcutaneous and connective tissues of their hosts, usually enclosed in fibrous cysts or nodules.
O. volvulus A species of Onchocerca, a parasitic worm that is transmitted to people by the bite of black flies of the genus Simulium. Tiny, threadlike offspring of the worm migrate to the skin and eyes and produce inflammatory reactions that result in skin swellings and river blindness. The inflammation produced by the parasites may be mediated by a bacterium, Wolbachia, which in turn infests the parasitic worm.
(ong″kō-sĕr″kī′ă-sĭs, ong″kō-sĕr″kī′ă-sēz″) pl. onchocerciases [Onchocerca + -iasis] Infection with Onchocerca volvulus.
INCIDENCE: About 100 million people are infected with Onchocerca volvulus worldwide. The disease is common in the tropics but not in temperate regions.
CAUSES: The parasite is transmitted to people when they are bitten by a species of black fly (genus Simulium). Tiny threadlike offspring of the worm migrate to the skin and eye and produce inflammation that result in Calabar swellings (temporary, painless swelling of the skin) and river blindness. The inflammation produced by the parasites may be mediated by a bacterium, Wolbachia, which in turn infests the parasitic worm.
TREATMENT: Ivermectin, an anti-parasitic, antihelminthic drug is used to treat onchocerciasis.
IMPACT ON HEALTH: Blindness and elephantiasis are common complications of infection.
PATIENT CARE: Mass public health campaigns in nations where river blindness is common can limit the spread of the disease. SYN: onchocercosis; river blindness.
[Gr. onkos, bulk, mass] Prefix meaning tumor, swelling, mass.
(ŏn′kō-sīt) [″ + kytos, cell] A large columnar cell with granular, acidophilic cytoplasm and a large number of mitochondria. They may become neoplastic.
(ong″kō-sit′ik) [oncocyte] An increase in cell size accompanied by eosinophilic granules in the cytoplasm. It is produced by abnormalities in cellular mitochondria and is a common abnormal finding in biopsy specimens of the salivary glands and the liver. Oncocytic change is not cancerous despite the word oncocytic.
(ŏng″kō-sī-tō′mă) [″ + ″ + oma, tumor] An adenoma composed of eosinophilic-staining epithelial cells with abundant mitochondria, esp. one of the salivary or parathyroid glands, or the kidneys.
(ŏng″kō-fē′tăl) Concerning tumors in the fetus.
(ong′kō-jēn″) [onco- + gene] A gene in a virus that has the ability to induce a cell to become malignant. Oncogenes have been identified ...