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298 GLOSSARY

Nymphs Stage of development for a variety of insects; the approximately 20 different species that is transmitted by sand-
nymph is an immature form of some invertebrates, particularly fly bites.
insects, which undergoes gradual metamorphosis (hemime- Oropharyngeal Part of the pharynx between the soft palate
tabolism) before reaching maturity. and the epiglottis.
Nymphal tick stage Immature stage of the tick, where the Osteitis deformans Chronic bone disorder caused by an in-
organism are small; for some species the nymphal stage may crease in the breakdown and re-growth of bone tissue.
also be an infective stage. Ovum An alternate term for egg.

O P

O & P examination Procedure for determining the pres- Paget’s disease Osteomalacia, or softening and bowing of
ence of either the ova (eggs) of a parasite or the parasite the long bones; also called osteitis deformans; disease occur-
itself. ring chiefly in the elderly in which the bones may become en-
Obligate Term for an absolute need or necessity for a material larged and weakened in structure, often leading to a fracture or
or condition. deformity.
Occult filariasis An infection in which microfilariae are not Palaeoparasitology Study of evidence from fossils of long
observed in the blood, although they may be found in other ago, showing evidence of parasitic infections.
body fluids. Pallor Paleness and lack of normal color.
Ocular micrometer The device enables the measurement Palpitations An unusually rapid or somewhat violent beating
of the size of magnified objects. Has a ruled scale etched into a of the heart; perhaps with ineffective pumping of blood.
glass disk that fits in a microscope eyepiece. Papillae Refers to small nipple-shaped projections or el-
Oculoglandular Enlargement of the lymph node around the evations such as those on the tongue or the small elevations
eye and in many cases is accompanied by conjunctivitis. at the root of a developing tooth, hair, feather projection, or
Ohara’s fever The disease is also known as or related to elevation.
deerfly fever or tularemia and is caused by infection by the bac- Paragonimiasis A food-borne parasitic infection caused by
terium Francisella tularensis. the lung fluke which is most frequently Paragonimus wester-
Onchocerciasis Infection by the organism Onchocerca vol- mani. Human infection occurs mainly via ingestion of raw or
vulus, known to cause river blindness; a parasitic worm that is undercooked freshwater crabs or crayfishes.
capable of migrating to the skin and into the eyes. Parasitism Condition of being infected with a parasite or
Oncosphere Tapeworm embryo with six hooks and is the parasites.
earliest differentiated stage of a cyclophyllidean tapeworm also Parthenogenetic A form of reproduction in which an un-
called a hexacanth embryo larval stage; the oncosphere bur- fertilized egg develops into a new organism; found frequently
rows through the gut wall to reach various tissues of the host, among insects and several other arthropods.
where they develop into encysted cysticerci or bladder worms. Pathogenesis The development or the source of a diseased
Oocyst Cystic form of a sporozoan (protozoan) that might or condition.
might not have a hard, resistant membrane for protection. Pathogenic Disease organisms that are capable of producing
Oocytes Refers to a female gametocyte, cell which develops disease (i.e., bacteria, viruses, or parasites).
into an egg or ovum by meiosis. Pathognomonic Term often used in medicine that indicates
Ookinete The fertilized form of the malarial parasite in a characteristics for a particular disease.
mosquito’s body, formed by fertilization of a macrogamete by Pediculosis Refers to an infestation of lice, the blood-feeding
a microgamete. ectoparasitic insects.
Operculum Something resembling a lid or cover; a lid or Pelvic veins Associated with the venous system in the pelvis,
covering is found in eggs of a pseudophyllidean tapeworm the lower abdomen, and groin.
but the cyclophyllidean species do not have an operculated Pemphigus Any of a variety of several acute or chronic auto-
ovum. immune skin diseases resulting in clusters of itching blisters,
Opisthorchiasis Condition in which an infection or disease particularly on the mucus membranes.
has occurred due to liver flukes of the genus Opisthorchis. Perianal Condition occurring in, or around, the tissues sur-
Opportunistic Refers to a microorganism that is able to rounding the anus.
avoid immune reactions only under certain predisposing dis- Periodontitis Infective disease process of the gums charac-
ease conditions, for example, when a person’s immune system terized by inflammation of the tissues caused by bacteria that
is impaired due to a variety of reasons. infect the roots of the teeth and surrounding gum crevices,
Orgnelles Literally means “small organs” and refers to in- sometimes by an amoebic gingivitis; produces bleeding, pus
tracellular structures in the cytoplasm of a cell or a one-celled formation, gradual loss of bone and tissues that support the
organism. teeth.
Oriental sore Known by a number of other names and is Peripheral chromatin Includes genetic material of DNA
the most common form of leishmaniasis. It is a skin infec- and proteins that condense to form chromosomes for cell divi-
tion caused by a single-celled parasite of which there are sion. This chromatin is located in the nucleus of a cell.