Some English technical terms in the field of malaria
ABER - Annual Blood Examination Rate. Calculated as (number of slides examined/population) x 100. WHO recommendation for malarious areas is that the number of slides examined per month should equal at least 1% of the population.
Active case detection - The detection by health workers of malaria infections at community and household level in population groups that are considered to be at high risk. Active case detection can be conducted as fever screening followed by --parasitological examination of all febrile patients or as parasitological examination of the target population without prior fever screening.
Anaemia - decrease in number of red blood cells and/or quantity of hemoglobin. Malaria causes anemia through rupture of red blood cells during merozoite release. The anaemia caused may be extreme. Pallor may be visible in the patient.
Animal trap - A cage, generally made of cloth, that is baited with an animal such as a cow, goat, etc. Collections of mosquitoes are made on the walls of this trap to assess and compare populations biting domestic animals with populations in dwellings.
Annual blood examination rate: The number of examinations of blood slides for malaria by microscopy per 100 population per year.
Anopheles: Anopheles is a genus of mosquito of about 460 species are recognized; while over 100 can transmit human malaria, only 30?40 commonly transmit parasites of the genus Plasmodium, which cause malaria in humans in endemic areas.
Anthropophagy - the process of feeding on people. Similar to anthropophilic.
Anthropophilic species prefer to feed on people as opposed to animals.
API - Annual Parasite Incidence. API = (confirmed cases during 1 year/population under surveillance) x 1000.
Autochthonous - locally transmitted by mosquitoes. Differentiated from imported, congenital, or blood-borne malaria.
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.
Congenital malaria - malaria acquired from the mother at birth.
Cryptic - an isolated case of malaria not associated with secondary cases, as determined by appropriate epidemiologicinvestigations.
Diurnal - during the daytime. The diurnal resting places of mosquitoes, especially newly-fed females, may be important in malaria control.
EIR = Entomological Inoculation Rate = mas, where ma = number of mosquito bites per night and s = proportion of those bites positive for sporozoites.
Elimination - The process of removing something on a temporary or semipermanent basis.
ELISA - enzyme-linked immunosorbent assay. ELISA is now often used to determine whether mosquito salivary glands are positive for sporozoites.
Endophagic - feeds indoors.
Endophilic - tends to inhabit/rest in indoor areas. Examples of endophilic anopheline species include Anopheles darlingi and An. funestus. Endophilism makes the blocking of malaria transmission through application of residual insecticides to walls easier to accomplish. (MacDonald 1956).
Eradication - The process of removing something permanently.
Erythrocyte - a red blood cell
Erythrocytic schizogony - the process of asexual reproduction of malaria parasites within red blood cells
Exerythrocytic schizogony - the process of asexual reproduction of malaria parasites outside of red blood cells, usually in the liver. This process is asymptomatic.
Exit trap - A trap constructed to capture mosquitoes that are exiting a house or structure. Exit traps are often used in studies that compare the tendency of mosquitoes to rest indoors after feeding versus to fly outside after feeding.
Exophagic - feeds outdoors.
Exophilic - tends to inhabit/rest in outdoor areas. After biting, an exophilic mosquito flies outside and rests woods, grass, or other outside areas.
Exophilism makes use of residual insecticides in buildings less effective.
GIS - Geographic Information System
GPS - Global Positioning System. Common GPS systems receive data that is sensitive enough to map blocks of a city.
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.
Gametocyte rate - percentage of persons in an area who carry gametocytes. Expressed as a percentage. The less the gametocyte rate of an area, the fewer infective humans are available for mosquitoes, and the less likely that transmission is to occur. (MacDonald 1956).
Gametocyte count - number of gametocytes per mm3 of blood. The lower the gametocyte count, the lower the infectivity of the human to the mosquito
Hypnozoite - a stage of malaria parasites found in liver cells. After sporozoites invade liver cells, some develop into latent forms called hypnozoites. They become active months or years later, producing a recurrent malaria attack. only P. vivax and P. ovale species that infect humans develop latent stage hypnozoites. Primaquine is the only available drug active against hypnozoites.
Hypoglycaemia - hypoglycemia -blood glucose less than the lower value of normal (70-110 mg/dl). Glucose levels of 40 and below constitute severe hypoglycemia, a life-threatening emergency.
Hypoglycemia is common in malaria, as malaria parasitized red blood cells utilize glucose 75 times faster than uninfected cells. In addition, treatment with quinine and quinidine stimulate insulin secretion, reducing blood glucose.
Imported malaria - A case of malaria that is brought into an area by someone who has become infected somewhere else. The person could be either a tourist or immigrant.
Induced malaria - Malaria acquired through artificial means (e.g. blood transfusion, dirty syringes, or malariotherapy).
Introduced malaria - malaria acquired by mosquito transmission from an imported case in an area where malaria is not a regular occurrence.
Infant parasite rate - The percentage of infants below one year old who show parasites in their blood films. If the infant parasite rate is zero for three consecutive years in a locality, this is regarded as absence of local transmission, provided that the survey is done every year and enough slides have been examined.
Longevity - the longevity, or length of lifespan of the mosquito is of considerable importance in malaria control. There are two reasons for this. The first is that the reproductive cycle of malaria in the mosquito takes 10-11 days, and the second is that if the mosquito lives a long time, it will be able to take several blood meals, and will have a higher chance of biting a human who has malaria parasites.
Macrogametocyte - the female form of the gametocyte.
Malaise - subjective feeling of being sick, ill, or not healthy. The feeling is generalized, varying from mild to severe in intensity. It may be the lone clinical manifestation of malaria, or may accompany other signs and symptoms, such as fever, headache, or nausea. This may be expressed as "feel achey all over," "flu-like symptoms," etc.
Microgametocyte - the male form of the gametocyte.
Oocyst - oocysts are Plasmodium cysts located in the outer stomach wall of mosquitoes, where sporozoite development takes place. When mature, the oocysts rupture and release sporozoites. Sporozoites subsequently migrate to the mosquito's salivary gland, and are injected into the host when the mosquito feeds.
Orthostatic hypotension - decrease in blood pressure occurring when an individual arises from a seated or lying position. A small decrease in blood pressure is normal, but large decreases are abnormal, especially if accompanied by clinical manifestations such as faintness, light-headedness, dizziness, or increased pulse. Orthostatic hypotension is a common finding in patients with malaria infections. The patient may complain of notable tiredness after conducting light office work, etc.
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.
Pandemic: A pandemic is an epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide. A widespread endemic disease that is stable in terms of how many people are getting sick from it is not a pandemic. Further, flu pandemics generally exclude recurrences of seasonal flu. Throughout history there have been a number of pandemics, such as smallpox and tuberculosis. More recent pandemics include the HIV pandemic as well as the 1918 and 2009 H1N1 pandemics.
Parasitaemia - the status of having parasites. This term is often used to express the quantity of parasites in the blood. If no fever or other symptoms are present, the condition is referred to as 'asymptomatic parasitaemia.'
Paroxysm - paroxysm - a sudden attack or increase in intensity of a symptom, usually occurring in intervals. Malaria is classically described as producing fever paroxysms; sudden severe temperature elevations accompanied by profuse sweating. Paroxysms occurring at 48-hr intervals are typical of Plasmodium vivax infection, particularly in semi-immune persons.
Plasmodium: Plasmodium is a genus of Apicomplexan parasites. Infection by these organisms is known as 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.
Pathogen: A pathogen in the oldest and broadest sense is anything that can produce disease. Typically the term is used to mean an infectious agent (colloquially known as a germ) - a microorganism, in the widest sense such as a virus, bacterium, prion, or fungus, that causes disease in its host. The host may be an animal, human, a plant, or even another microorganism. There are several substrates including pathways whereby pathogens can invade a host. The principal pathway s have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen. Diseases caused by organisms in humans are known as pathogenic diseases. Some of the diseases that a pathogen can cause are smallpox, influenza, mumps, measles, chickenpox, ebola and rubella.
Not all pathogens are necessarily undesirable to humans. In entomology, pathogens are one of the "Three P's" (predators, pathogens and parasitoids) that serve as natural or introduced biological controls to suppress arthropod pest populations.
Proportional case rate: The number of cases diagnosed as clinical malaria for every 100 patients attending hospitals and dispensaries .
Protozoan: A member of the Kingdom Protista. Protozoa are single-celled organisms . 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.
Radical Cure - treatment intended to achieve cure of P. vivax or P. malariae malaria. These two species have exoerythrocytic stages. Requires primaquine treatment, which destroys latent exoerythrocytic stage parasites (hypnozoites). Typical case patient: a returned traveller from Central America who has had a relapse of malaria.
Recrudescense - a repeated attack of malaria (short term relapse or delayed), due to the survival of malaria parasites in red blood cells. Characteristic of P. malariae infections.
Recurrence - a repeated attack weeks, months, or occasionally years, after initial malaria infection, also called a long-term relapse. Due to re-infection of red blood cells from malaria parasites (hypnozoites) that persisted in liver cells (hepatocytes).
Relapsing malaria - Renewed manifestation (of clinical symptoms and/or parasitemia) of malaria infection that is separated from previous manifestations of the same infection by an interval greater than any interval resulting from the normal periodicity of the paroxysms.
Refractory malaria - malaria that is not responsive to residual treatment. The cause of the lack of response to residual treatment is usually defined to be factors other than physiological insecticide resistance. Examples of causes of refractory malaria are vector exophily and zoophily with failure to enter houses. An example of refractory malaria occurred in the Jordan Valley during the early 1950s. Anopheles sergenti and Anopheles superpictus were evading residual treatment of dwellings by resting in caves and natural fissures in earth (Farid 1954).
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.
Reduction of mosquito numbers through larval control is less effective by itself than causing mosquito mortality through adult control. The reason is that not only does adult control cause a reduction in mosquito numbers, but it also causes reduction in longevity of female anophelines . The fewer gonotrophic cycles that a female mosquito has, the less likely that it is to transmit sporozoites (MacDonald 1956, p. 620).
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.
Splenomegaly - an enlarged spleen. A common finding in malaria patients that sometimes can be detected by physical examination. May occur in otherwise asymptomatic patients and is of use in conducting malaria surveys of a community, although it should not be the only factor considered when counting cases.
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.
Sporozoite rate - The percentage of female anopheline mosquitoes of a particular species that bear sporozoites in their salivary glands. Expressed as a percentage.
Stockouts: A stockout, or out-of-stock (OOS) event is an event that causes inventory to be exhausted. While out-of-stocks can occur along the entire supply chain, the most visible kind are retail out-of-stocks in the fast moving consumer goods industry (e.g., sweets, diapers, fruits). Stockouts are the opposite of overstocks, where too much inventory is retained. Stockout is generalized problem in Togo, as retailers do not buy again until stockout causing delays that are often months.
Temperature - the optimal temperature for development of P. falciparum is 30oC , while the optimal temperature for development of P. vivax is 25oC . The time required for development of the sexual phases of the malaria parasite in the mosquito is 10-11 days at these temperatures.
Tinnitus - ringing sound in the ears, a common side effect of quinine treatment.
Vector competence - the ability to transmit malaria. Said of Anopheles mosquitoes.
Vulnerability: Either proximity to a malarious area or the frequency
of influx of infected individuals or groups and/or infective anophelines.
Zoophagy - the process of feeding on animals (example: cattle).
Zoophilous - prefers to feed on animals.
Acronyms and Abbreviations
ACD Active case detection
ACT Artemisinin-based combination therapy
AMC Anti-Malaria Campaign
API Annual parasite index
G6PD Glucose-6-phosphate dehydrogenase
IRS indoor residual spraying
ITN insecticide-treated net
LLIN long-lasting insecticidalnet
PCD Passive case detection
PCR polymerase chain reaction
RDT Rapid diagnostic test
WHO World Health Organization
acrOnyms and abbrEviatiOns
Annual parasite index
The number of reported malaria cases per 1 000 population at risk per year.
Case-based surveillance Every case is reported and investigated immediately
(and also included in the weekly reporting system).
Case definition (control programmes)
Suspected malaria case in which malaria parasites have
been demonstrated in a patient?s blood by microscopy
or a rapid diagnostic test.
Suspected malaria case with no diagnostic test to
confirm malaria but nevertheless treated presumptively
Patient illness suspected by a health worker to be due
to malaria. Fever is usually one of the criteria.
Case definition (elimination programmes)
A case locally acquired by mosquito-borne transmission,
i.e. an indigenous or introduced case (also called
A case the origin of which can be traced to a known
malarious area outside the country in which it was
Any case contracted locally (i.e. within national
boundaries), without strong evidence of a direct link
to an imported case. Indigenous cases include delayed
first attacks of Plasmodium vivax malaria due to locally
acquired parasites with a long incubation period.
A case the origin of which can be traced to
a blood transfusion or other form of parenteral inoculation
but not to normal transmission by a mosquito.
A case contracted locally, with strong epidemiological
evidence linking it directly to a known imported case
(first generation from an imported case, i.e. the mosquito
was infected from a case classified as imported).
A case locally acquired by mosquito-borne transmission,
i.e. an indigenous or introduced case (also called
Any case in which, regardless of the presence or
absence of clinical symptoms, malaria parasites have
been confirmed by quality-controlled laboratory
x Eliminating Malaria | Progress towards elimination in Sri Lanka | Glossary
Collection of information to allow classification of a
malaria case by origin of infection, i.e. imported, introduced,
indigenous or induced. Case investigation includes
administration of a standardized questionnaire
to a person in whom a malaria infection is diagnosed.
Diagnosis, treatment, clinical care and follow-up of
Compulsory reporting of detected cases of malaria by
all medical units and medical practitioners, to either
the health department or the malaria elimination
service (as laid down by law or regulation).
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.
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.
Applied to malaria when there is an ongoing,
measurable incidence of cases and mosquito-borne
transmission in an area over a succession of years.
Entomological inoculation rate
The number of infectious mosquito bites received per
person per unit time.
Occurrence of cases in excess of the number expected
in a given place and time.
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
Attempts to determine as systematically and objectively
as possible the relevance, effectiveness and impact of
activities in relation to their objectives.
A defined, circumscribed locality situated in a currently
or former malarious area containing the continuous
or intermittent epidemiological factors necessary for
malaria transmission. Foci can be classified as endemic,
residual active, residual non-active, cleared up, new
potential, new active or pseudo.
The sexual reproductive stage of the malaria parasite
present in the host?s red blood cells.
The dormant stage of the malaria parasite present in
the host?s liver cells (limited to infections with P. vivax
and P. ovale).
The time between infection (by inoculation or
otherwise) 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.
Local mosquito-borne malaria transmission
Occurrence of human malaria cases acquired in a
given area through the bite of infected Anopheles
Eliminating Malaria | Progress towards elimination in Sri Lanka | Glossary xi
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.
The number of newly diagnosed malaria cases during
a specified time in a specified population.
The number of malaria cases at any given time in a
specified population, measured as positive laboratory
Monitoring (of programmes)
Periodic review of the implementation of an activity,
seeking to ensure that inputs, deliveries, work schedules,
targeted outputs and other required actions are
proceeding according to plan.
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
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.
Population at risk
Population living in a geographical area in which locally
acquired malaria cases occurred in the current
year and/or previous years.
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
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.
Renewed manifestation of an infection after temporary
latency, arising from activation of hypnozoites
(and therefore limited to infections with P. vivax and
Sensitivity (of a test)
Proportion of people with malaria infection (true
positives) who have a positive test result.
Slide positivity rate
Proportion of microscopy slides found to be positive
among the slides examined.
Specificity (of a test)
Proportion of people without malaria infection
(true negatives) who have a negative test result.
The prevalence of splenomegaly.
Surveillance (control programmes)
Ongoing, systematic collection, analysis and interpretation
of disease-specific data for use in planning,
implementing and evaluating public health practice.
Surveillance (elimination programmes)
That part of the programme designed for the identification,
investigation and elimination of continuing
transmission, the prevention and cure of infections,
and the final substantiation of claimed elimination.
xii Eliminating Malaria | Progress towards elimination in Sri Lanka | Glossary
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.
Period of the year during which mosquito-borne transmission of malaria infection usually takes place.
Measures of any kind against malaria-transmitting mosquitoes intended to limit their ability to transmit the disease.
Ability of a mosquito species, in comparison with another species in a similar climatic environment, to transmit malaria in nature.
Number of new infections that the population of a given vector would induce per case per day at a given place and time, assuming conditions of non-immunity.
Factors affecting vectorial capacity include: the density of female anophelines relative to humans; their longevity, frequency of feeding and propensity to bite humans; and the length of the extrinsic cycle of the parasite.
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.
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