Anopheles A genus of mosquito, some species of which can transmit human malaria.

Annual Parasite Incidence (API) The number of reported malaria cases per 1,000 population at risk per year.

Artemisinins A class of drugs used for the treatment (not prevention) of malaria usually as a part of a combination therapy, derived from the sweet wormwood or Qinghao plant (Artemisia annua).

Cerebral malaria This grave complication of malaria happens at times with P. falciparum infection and involves malaria infection of the very small capillaries that flow through the tissues of the brain. This complication has a fatality rate of 15% or more, even when treated and is extremely serious.

Certification of malaria-free status Certification granted by WHO after it has been proved beyond reasonable doubt that the chain of local human malaria transmission by Anopheles mosquitoes has been fully interrupted in an entire country for at least 3 consecutive years.

Chloroquine A drug used against malaria for both prevention and treatment. A very safe and inexpensive drug, its value has been compromised by the emergence of chloroquine-resistant malaria parasites.

Congenital malaria Malaria acquired from the mother at birth.

DEET: N,N-diethylmetatoluamide An ingredient of insect repellents.

Doxycycline An antibiotic drug that can be used against malaria; by itself for prevention or in combination with either quinine or quinidine when used for treatment.

Drug resistance The result of microbes changing in ways that reduce or eliminate the effectiveness of drugs, chemicals, or other agents to cure or prevent infections.

Entomological Inoculation Rate (EIR) Calculated by multiplying the number of mosquito bites per night by the proportion of those bites positive for sporozoites.

Elimination Reduction to zero of the incidence of infection by human malaria parasites in a defined geographical area as a result of deliberate efforts. Continued measures to prevent re-establishment of transmission are required.

Endemic Applied to malaria when there is an ongoing, measurable incidence of cases and mosquito-borne transmission in an area over a succession of years.

Epidemic Occurrence of cases in excess of the number expected in a given place and time.

Eradication Permanent reduction to zero of the worldwide incidence of infection caused by human malaria parasites as a result of deliberate efforts. Intervention measures are no longer needed once eradication has been achieved.

Erythrocytic stage A stage in the life cycle of the malaria parasite found in the red blood cells. Erythrocytic stage parasites cause the symptoms of malaria.

Exoerythrocytic stage A stage in the life cycle of the malaria parasite found in liver cells (hepatocytes). Exoerythrocytic stage parasites do not cause symptoms.

Falciparum See Plasmodium.

G6PD deficiency An inherited abnormality that causes the loss of a red blood cell enzyme. People who are G6PD deficient should not take the antimalarial drug primaquine.

Gametocyte The sexual reproductive stage of the malaria parasite. Gametocytes circulate in the blood stream, are picked up by the Anopheles mosquito, undergo sexual reproduction in the midgut of the mosquito, and attaches to the mosquito’s midgut, where they form an oocyst that eventually produces sporozoites.

Geographic Information System (GIS)

Global Positioning System (GPS) Common GPS systems receive data that is sensitive enough to map blocks of a city.

Hypnozoite Dormant form of malaria parasites found in liver cells. Hypnozoites occur only with Plasmodium vivax and P. ovale. After sporozoites (inoculated by the mosquito) invade liver cells, some sporozoites develop into dormant forms (the hypnozoites), which do not cause any symptoms. Hypnozoites can become activated months or years after the initial infection, producing a relapse.

Incubation period The time between infection and the first appearance of clinical signs.

Intervention (public health) Activity undertaken to prevent or reduce the occurrence of a health condition in a population. Examples of interventions for malaria control include the distribution of insecticide-treated mosquito nets, indoor residual spraying with insecticides, and the provision of effective antimalarial therapy for prevention or curative treatment of clinical malaria.

Larvae An immature stage of a developing mosquito. Mosquito larvae are wingless and develop in water.

Malaria-free An area in which there is no continuing local mosquito-borne malaria transmission and the risk for acquiring malaria is limited to introduced cases only.

Malaria incidence The number of newly diagnosed malaria cases during a specified time in a specified population.

Malaria prevalence The number of malaria cases at any given time in a specified population, measured as positive laboratory test results.

Mefloquine A drug used against malaria for both prevention and treatment.

Merozoite A daughter cell formed by asexual development in the life cycle of malaria parasites. Liver-stage and blood-stage malaria parasites develop into schizonts which contain many merozoites. When the schizonts are mature, they (and their host cells!) rupture; the merozoites are released and infect red blood cells.

Oocyst A stage in the life cyle of malaria parasites, oocysts are rounded structures located in the outer wall of the stomach of mosquitoes. Sporozoites develop inside the oocysts. When mature, the oocysts rupture and release the sporozoites, which then migrate into the mosquito’s salivary glands, ready for injection into the human host.

Outbreak of Malaria Outbreak is a term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected at a particular time and place. It may affect a small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious disease may be sufficient to constitute an outbreak. Outbreaks may also refer to epidemics, which affect a region in a country or a group of countries, or pandemics, which describe global disease outbreaks.

Parasite Any organism that lives in or on another organism without benefiting the host organism; commonly refers to pathogens, most commonly in reference to protozoans and helminths.

Parasite prevalence Proportion of the population in whom Plasmodium infection is detected at a particular time by means of a diagnostic test (usually microscopy or a rapid diagnostic test).

Passive case detection Detection of malaria cases among patients who, on their own initiative, go to a health post for treatment, usually for febrile disease.

Plasmodium Plasmodium is a genus of Apicomplexan parasites that causes malaria. Of the over 200 known species of Plasmodium , at least 11 species infect humans. The parasite always has two hosts in its life cycle: a vector – usually a mosquito – and a vertebrate host. The four species that naturally infect humans are Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. Plasmodium knowlesi is a zoonotic species that naturally infects macaques in Southeast Asia that can also infect humans.

Population at risk Population living in a geographical area in which locally acquired malaria cases occurred in the current year and/or previous years.

Proportional case rate The number of cases diagnosed as clinical malaria for every 100 patients attending hospitals and dispensaries.

Protozoa Single-celled organisms [eukaryotes]. The single cell performs all necessary functions of metabolism and reproduction. Some protozoa are free-living, while others, including malaria parasites, depend on other organisms for their nutrients and life cycle. Malaria parasites are members of the Phylum Apicomplexa.

Quinine A drug used against malaria, obtained from the bark of the cinchona tree. Quinine is used for treatment but not prevention of malaria.

Rapid diagnostic test An antigen-based stick, cassette or card test for malaria in which a coloured line indicates that plasmodial antigens have been detected.

Rapid diagnostic test positivity rate Proportion of positive results among all the rapid diagnostic tests performed.

Receptivity Relative abundance of anopheline vectors and existence of other ecological and climatic factors favouring malaria transmission.

Re-establishment of transmission Renewed presence of a constant measurable incidence of cases and mosquito-borne transmission in an area over a succession of years. An indication of the possible re-establishment of transmission would be the occurrence of three or more introduced and/or indigenous malaria infections in the same geographical focus, for two consecutive years for P. falciparum and for three consecutive years for P. vivax.

Reproduction rate Reproduction rates > 1.0 indicate an expansion of infections in a population while those < 1.0 indicate a decline in infections in the population. The goal of malaria control is to decrease the reproduction rate. This can be accomplished by altering mosquito numbers, longevity of female anophelines, biting habits, and recovery rate of gametocytemic person.

Residual treatment Treatment of houses, animal sheds, and other buildings where people or animals spend nighttime hours with insecticide that has residual efficacy. The goal of residual treatment is to block transmission by stopping human-vector contact.

Resistance The ability of an organism to develop ways to be impervious to specific threats to their existence. The malaria parasite has developed strains that are resistant to drugs such as chloroquine. The Anopheles mosquito has developed strains that are resistant to DDT and other insecticides.

Schizogony Asexual reproductive stage of malaria parasites. In red blood cells, schizogony entails development of a single trophozoite into numerous merozoites. A similar process happens in infected liver cells.

Sporozoite The infective stage of the malaria parasite that is passed to the human host from the salivary glands of the mosquito. Sporozoites infect liver cells, disappearing from bloodstream within 30 minutes. The mechanism for this amazingly rapid disappearance from the bloodstream to the liver is still unknown. Sporozoites are delicate and spindle-shaped stages that are released into the haemocoel of the mosquito when the oocyst ruptures. Some eventually find their way to the salivary glands of the mosquito.

Transmission intensity Rate at which people in a given area are inoculated with malaria parasites by mosquitoes. This is often expressed as the “annual entomological inoculation rate”, which is the number of inoculations with malaria parasites received by one person in one year.

Transmission season Period of the year during which mosquito-borne transmission of malaria infection usually takes place.

Vector An organism (e.g., Anopheles mosquitoes) that transmits an infectious agent (e.g. malaria parasites) from one host to the other (e.g., humans).

Vector competence The ability of a vector (e.g., Anopheles mosquitoes) to transmit a disease (e.g., malaria).

Vector control Measures of any kind against malaria-transmitting mosquitoes intended to limit their ability to transmit the disease.

Vigilance A function of the public health service during a programme for prevention of reintroduction of transmission, consisting of watchfulness for any occurrence of malaria in an area in which it had not existed, or from which it had been eliminated, and application of the necessary measures against it.

Vulnerability Either proximity to a malarious area or the frequency of influx of infected individuals or groups and/or infective anophelines.