Dictionary of Tropical Medicine

Acquired Immune Deficiency Syndrome (AIDS)

A severe manifestation of infection with the Human immunodeficiency virus (HIV).

Acute

Occurring suddenly or over a short period of time.

Adder

A group of snakes with a wide geographical distribution. Belong to the family Elapidae. Also known as vipers.

Adenocarcinoma

Malignant tumour of glandular epithelium.

Adenoma

Benign tumour of glandular epithelium.

Adult Mosquito

The adult (imago) is a slender, delicate insect with six comparatively long, thin legs. The outer covering of the body is composed of a tough substance called chitin. The body is divided into three distinct parts: head, thorax and abdomen.

Aetiologic Agent

An agent pertaining to aetiology.

Aetiology

The cause of a disease. The study of the causes of diseases. May be classified as follows: Genetic, Congenital, Infection, Autoimmune, Nutrition, Toxic, Environment, Traumatic, Neoplastic, Metabolic, Psychosomatic, Degenerative, Iatrogenic, Idiopathic

Agent

A substance, living or inanimate, or a force, sometimes rather intangible, the excessive presence or relative lack of which is the immediate or proximal cause of a particular disease.

AIDS

See Acquired Immune Deficiency Syndrome.

AIDS-related complex

A variety of chronic symptoms and physical findings that occur in some persons who are infected with HIV, but do not meet the Centres for Disease Control's definition of AIDS. Symptoms may include chronic swollen glands, recurrent fevers, unintentional weight loss, chronic diarrhoea, lethargy, minor alterations of the immune system (less severe than those that occur in AIDS), and oral thrush. ARC may or may not develop into AIDS.

Ala

A winged-like expansion of cuticular integument of nematodes; an expansion at the oesophageal region called "cervical alae", e.g. in Toxocara species, or at the posterior end called "caudal alae" and in the larval stages of some nematodes the expansion may extend almost entire lateral aspects of the body, these expansions are called "lateral alae". In Oxyuridae, e.g. Enterobius vermicularis, the cuticle at the anterior end expands dorso-ventrally into "cephalic alae".

Algid

A fever in which the patient suffers from peripheral vascular collapse. Also known as a cold fever as their skin feels cold and clammy.

Alopecia

The loss of hair. Often occurs after treatment of cancer with chemotherapeutic agents.

Ameloblastoma

Agressive benign tumour of jaw, usually the lower jaw. It is more common in Asian and African people. It results from a proliferation of ameloblast cells, which is the cell that forms enamel.

Amoebiasis

Protozoal disease caused by Entamoeba histolytica, which may present as an amoebic liver abscess, intestinal amoebiasis or disseminated amoebiasis.

Amoebic Liver Abscess (ALA)

Abscess of the liver caused by Entamoeba histolytica and often containing so-called anchovy sauce fluid.

Anaemia

A reduced number or volume of red blood cells, which results in lowered haemoglobin levels as seen in a number of tropical diseases, e.g. malaria, hookworm disease. It may present with a number of symptoms and signs including fatigue and pallor, especially of the conjunctival and mucous membranes. There are many possible causes.

Anaerobic

A process where oxygen is not used.

Analgesia

Pain reduction or relief.

Anaphylaxis

Increasing sensitivity of the body to a protein after an initial reaction which may have been mild. The second or third exposure to this protein may cause severe respiratory or circulatory embarrassment, leading to death.

Anaplasia

Type of cancerous change in which the cancer cells involved do not resemble the cells from which they arose. Undifferentiated.

Anemone

A usually colourful group of Anthozoans common on reefs. Contact with human skin of divers or snorkellers may cause severe, localised skin reactions, and systemic symptoms including severe tiredness. Research is current in this area.

Anorexia

Loss of appetite for food.

Anthozoa

The taxonomic Class of animals, including sea anemones, and hard and soft corals.

Anthrax

A zoonotic infection of humans contracted from sheep, cows and similar animals and their products. Caused by Bacillus anthracis, a spore-bearing Gram positive rod. Anthrax includes a cutaneous form (malignant pustule), a pneumonic form (Woolsorters disease) and intestinal anthrax. The form of the disease depends largely of the site of entry.

Antibody

A protein belonging to the class of proteins called immunoglobulins. Antibodies are produced by plasma cells to counteract specific antigens or foreign proteins (including infectious agents like viruses, bacteria, etc... or venom). The antibodies then combine with the antigen they are made to fight and often cause the death of that infectious agent. Their presence helps prevent symptoms or disease processes on further exposures to the same antigen.

Antigen

A substance (often a protein or carbohydrate on the surface of an infectious agent) foreign to the body that stimulates the formation of specific antibodies to combat its presence. Any protein (including toxins) encountered that may cause the body to produce antibodies against it.

Antivenom

Antibody mixtures produced by an animal after exposure to small doses of an injected venom that may be harmful to man. As the doses are small, the injection is not lethal and antibodies are formed. This resultant antibody mixture is then collected from the animal's blood, purified, concentrated, and thus becomes an antivenom. It can then be injected into humans to counteract symptoms (or death) produced by the venom of the animal potentially lethal to humans. An antivenom is specific for the venom against which it is prepared, and does not neutralise other antivenoms. A rare exception to this is Tiger snake (Notechis scutatus) antivenom which can be used to effectively counteract the venom of the sea snakes if specific sea snake antivenom is not available.

Anus

In nematodes, an opening of the alimentary system on the ventral side at the posterior end of the female nematodes.

API

The Annual Parasitic Index per 1000 population in obtained by dividing positive cases (x 1000) by total population.

Apicomplexa

Sporozoan protozoa which have no organs of locomotion. Includes the malaria parasites (Plasmodium) and Toxoplasma.

Arbovirus

A class of viruses transmitted by arthropods. Name contracted from arthropod-borne viruses.

Argassid

A family of ticks the soft ticks or tampans. Vectors of Endemic relapsing fever.

Artemether

Also called Arteether and more soluble forms called Artesunate. An antimalarial drug derived from artemisinin. Artemisinin is produced from the Chinese herbal drug Qinghaosu. It is used for rapid clearance of susceptible peripheral parasites, especially in the treatment of severe malaria, due to Plasmodium falciparum.

Arthropod

Animals characterised by several jointed legs and a hard outer exoskeleton, eg, spiders, ticks, mites and insects (the group that includes mosquitoes).

Ascites

An accumulation of a serous effusion in the abdominal cavity seen in a number of conditions such as cirrhosis and schistosomiasis.

Asepsis

Absence of septic matter, or freedom from infection. The prevention of the access of microorganisms.

Aseptic technique

Not septic; free from septic material technique.

Ashdown's medium

A differential selective culture medium for Burkholderia pseudomallei, devised by Dr Lesley Richard Ashdown (1943-93), Townsville, Australia. B. pseudomallei grows as distinctive purple rugose colonies on this medium.

Aspergillosis

Infection caused by the opportunistic saprophytic fungus, Aspergillus. Can include the effects of aflatoxin which is formed by the fungi growing on mouldy foods such as peanuts and which can be associated with cancer of the liver.

Assessment

A process of evaluating options which enables informed choices to be made between alternatives.

Asystole

Absence of visible contraction of the heart, and consequent circulation of the blood, resulting rapidly in death. This may occur after envenomation.

Attenuated

Weakened.

Atypical mycobacteria

A group of mycobacteria which differ in their growth characteristics from Mycobacterium tuberculosis but which they resemble in being acid-fast. The atypical mycobacteria are also known as the Potentially Pathogenic Environmental Mycobacteria (P.P.E.M.). They can cause a spectrum of human disease which in some cases can resemble tuberculosis. Mostly they cause disease in immunologically compromised humans such as those suffering from AIDS.

Australian encephalitis

An arboviral disease in Australia transmitted by mosquitoes.

Autoinfection

Self-infection eg from one body site to another.

Average incidence density

The ratio of the number of new cases of the disease and the amount of population-time of follow-up (e.g. person-year) of the disease-free population.