Dictionary of Tropical Medicine


Sperm or ova.


These are sexual forms of the malarial parasite that develop within red blood cells. The male gametocytes are known as microgametocytes and the female gametocytes are known as macrogametocytes.

Gas embolism

A blockage of a blood vessel by air or gas, usually caused when a diver ascends too rapidly, when the air expands, causing rupture of the lung tissues which then allows the air into the blood stream. It often results in death due to air bubbles occluding the blood vessels supply the brain (cerebral gas embolism).

Gastric cirri

Hair-like appendages in the stomach of most cubozoan jellyfish. They contain nematocysts and aid in digestion.

Gastrovascular cavity

The digestive system of the cnidarian, consisting of the stomach and its connecting canals which perform a similar task to vascular system of higher orders.


The functional unit of heredity. A segment of DNA (or RNA in certain viruses) that encodes a single protein or confers a specific trait.

Gene expression

The full use of the information in a gene via transcription and translation leading to production of a protein.


Comprising similar species; a rank between Family and Species.


The total genetic information present in a cell or organism.


(pl. genera) The taxonomic category below Family, but above Species. A taxonomic grouping of closely related species. A category of biological classification, see genera and Taxonomy.

Glucose-6-phosphate-dehydrogenase (G6PD) deficiency

A deficiency in the enzyme G6PD resulting in a haemolytic anaemia. This haemoglobinopathy contraindicates the use of the 4-aminoquinolines such as primaquine for the radical treatment of benign tertian and ovale tertian malaria.


A group of male or female reproductive cells, which in jellyfish often line the sides of the stomach, but may extend through the bell of a jellyfish in the most mature specimens, especially the chirodropids.


Neisseria gonorrhoeae.


A sexually transmitted disease caused by the Gram negative diplococcus, Neisseria gonorrhoeae

Gonotrophic stage

The condition of female mosquitoes during blood ingestion, ovarian development, leading to oviposition.


Estimate of the degree of malignancy of a neoplasm.

Gram stain

Stain developed in 1884 by Hans Christian Gram, whereby Gram positive bacteria stain purple while Gram negative bacteria stain red.

Granuloma inguinale



A cuticular thickening of the dorsal wall of the spicular pouch in nematodes.

Guinea worm

Dracunculus medinensis.