Dictionary of Tropical Medicine

Nairobi eye

An acute inflammation of the eye resulting from an irritant secreted by beetles of the genus Paederus, getting onto the eye.

Nanometer

A unit used in electronmicroscopy and virology. 1 nm = 1 thousandth of a um.

Natural history of disease

The progressive development of a disease that runs its course without treatment.1. Stage of susceptibility2. Stage of presymptomatic3. Stage of clinical disease4. Stage of disability/resolution

Neck

The connecting tissues between the scolex and strobila of a tapeworm. This part is unsegmented.

Negri bodies

Inclusions found in the cytoplasm of brain neurons in rabies.

Nematocyst

The stinging cells present on the tentacles (and the bell of some species) of cnidarian. Each nematocyst consists of an coiled tube which may be bathed in venom. When the trigger on the outside of the nematocyst is touched, the tube rapidly inverts itself firing rather like a harpoon into the tissues of the prey. Venom on the outside of this tube is thus deposited in the tissues, and possibly into blood vessels during this trajectory. Finally, in some specialised nematocysts venom is then discharged through the open end of this thread tube and is deposited in the tissues of the prey.

Nematodes

Unsegmented worms having a gut and a body cavity (pseudocoel). Are round in transverse section. Many species are parasitic.

Neoplasm

New or abnormal uncontrolled growth.

Neurone

The cell of a nerve responsible for transmission of the signal along the nerve fibre.

Nipah virus

Virus first identified from the village of Nipah in Malaysia. Carried by flying foxes (fruit bats). Can infect pigs and humans.

NMR

Nuclear magnetic resonance. A technique for making images of the organs of the body using the way protons resonate in a magnetic field.

Nodular worms

Nematodes which live in nodules in the wall of the large intestine. Belong to the genus Oesophagostomum. Infect a range of mammal species including humans.

Norwegian scabies

A severe form of scabies presenting often in immunosuppressed individuals, often presenting with a generalised dermatitis, extensive scaling and occasionally vesiculation and crusting. The severe itch may be reduced or absent. Secondary infection can develop. See also Scabies.

Nosocomial infection

Infection pertaining to a hospital or an infirmary.

Notifiable Disease

An infectious or other disease required to be notified to the relevant State Government Authority for entry onto the Notifiable Diseases Register.

Nucleic acid

Group of chemicals found in cells and which carry biochemical codes for heredity and day-to-day functioning of cells.