Dictionary of Tropical Medicine

Iatrogenic

Describes any adverse condition resulting from medical treatment.

Ice

An excellent analgesic to stop the skin pain of many envenomations, especially those of jellyfish stings. It is usually less effective than heat for the treatment of stonefish, stingray and other venomous-spined fish envenomations.

Icterus

Jaundice

Idiopathic

No known cause.

Immune person/animal

A person or animal that possesses specific previous antibodies or cellular immunity as a result of previous infection or immunisation, or is so conditioned by such previous specific experience as to respond adequately with production of antibodies sufficient to prevent illness following exposure to the specific infectious agent of the disease. Immunity is relative; an ordinarily effective protection may be overwhelmed by an excessive dose of the infectious agent or an unusual portal of entry.

Immunity

The body's ability to resist and overcome infection and cancer.

Immunoglobulins

Body proteins that act as antibodies.1. IgG: The immunoglobulin that can be measured in the serum approximately two weeks after a challenge by an antigen. Can cross the placenta from mother to foetus.2. IgM: The immunoglobulin that can be measured very soon after a challenge by an antigen. The level returns to a non-measurable level very quickly and so this measurement is useful as a test for recent envenomation (or illness). Cannot cross the placenta from mother to foetus. Presence in a neonate therefore indicates infection of the body.3. IgE: Reaginic antibody; immunoglobulin found in association with allergic or homocytotrophic responses.4. IgA: Secretory antibody; immunoglobulin found in nonvascular fluids, such as the saliva, bile, aqueous humor, synovial fluide etc.

Immunosuppressed

A state of the body where the immune system defences do not work properly. This can be the result of illness or the administration of certain drugs (commonly ones used to fight cancer).

Immunotherapy

A type of cancer treatment which involves stimulating the body's immune system.

Inapparent infection

The presence of infection in a host without occurrence of recognisable clinical signs or symptoms. Inapparent infections are only identifiable by laboratory means. A synonym would be subclinical infection.

Incidence

Number of new cases of a disease or deaths within the specified period of time and population.

Incidence rate

A quotient, with the number of cases of a specified disease diagnosed or reported during a stated period of time as the numerator, and the number of persons in the population in which they occurred as the denominator.

Inclusions

Particles in the cytoplasm or nucleus of cells infected with certain viruses or bacteria such as the chlamydiae.

Incubation period

The time interval between exposure to an infectious agent (eg, bite) and appearance of the first sign or symptom of the disease in question.

Infected person

A person who harbours an infectious agent and who has either manifest disease or inapparent infection. An infectious person is one from whom the infectious agent can be naturally acquired.

Infection

The entry and development or multiplication of an infectious agent in the body of humans or animals. Infection is not synonymous with infectious disease; the result may be inapparent or manifest. The presence of living infectious agents on exterior surfaces of the body, or upon articles or apparel or soiled articles, is not infection but contamination of such surfaces and articles.

Infectious agent

An organism, chiefly a microorganism but including helminths, that is capable of producing infection or infectious disease.

Infectious disease

A disease of humans or animals resulting from an infection.

Infectivity

The quality of being infectious; infectiousness.

Infestation

An invasion by animal ectoparasites. Infestation is used more for gross parasites on the surface of the body that produce mechanical effects; infection of parasites within the body.

Inflammation

The condition into which tissues enter as a reaction to injury. Usually manifested by heat, pain and swelling.

Insecticide

Chemical that kills insects and other arthropods, such as mites. Chemicals that kill ticks and mites often termed acaricides.

Insecticide resistance

The ability of a mosquito or other insect to survive contact with an insecticide in quantities that would normally kill a mosquito of the same species.

Instars

Stages of insect growth and development. In mosquitoes there are four larval instars, each terminating with the shedding of the cuticle.

Integrated control

A combination of biological and insecticidal methods of control, e.g. the introduction of predacious fish to breeding places which are also sprayed with insecticides that have minimum effect on the fish.

Interferon

An antiviral chemical secreted by an infected cell which strengthens the defence of nearby cells not yet infected.

Interleukin-2

A substance produced by T-lymphocytes that stimulates activated T-lymphocytes and some activated B-Lymphocytes to proliferate. Also known as T-Cell growth factor.

Intermediate host

An animal or human host where the juvenile stages of the parasite undergo an asexual reproductive phase of development but not reaching adult stage.

Interval

Time between paroxysms in malaria.

Intravenous

Injected into or delivered through a needle in a vein.

Invasiveness

The ability of a microorganism to enter the body and to spread more or less widely throughout the tissues. The organism may or may not cause clinical symptoms.

Irukandji

A jellyfish and a syndrome name derived from the name of a tribe of Aboriginals near Palm Cove, Cairns in north Queensland where many jellyfish stings with severe systemic symptoms were first reported (and still occur).

Ischaemia

Lack of tissue oxygen and nutrients usually due to impaired (arterial) blood flow.

Isolation

The separation, for the period of communicability, of infected persons or animals from others, in such places and under such conditions as will prevent the direct or indirect conveyance of the infectious agent from those infected to those who are susceptible or who may spread the agent to others. Can also be used in relation to microorganisms (e.g. a bacterial species isolated from the patient).

Ixodid

Hard tick (ie tick with a hard dorsal scutum) belonging to the family Ixodidae. Includes amongst others, the genera Amblyomma, Dermacentor, Ixodes Rhipicephalus and Hyalomma.