Mosquitoes Health Dictionary

An organism which carries or transmits a pathogen from a plant or animal to another plant or animal of the same species which is free of the disease. Anopheline mosquitoes are the vectors of human malaria.... vector

A protozoan disease of humans caused by blood parasites of the species, Plasmodium falciparum, P. vivax, P. ovale or P. malariae and transmitted by anopheline mosquitoes. P. falciparum is most likely to cause death, if untreated,. and can also be a great mimicker in its presentation. Malaria should be suspected in anyone with a fever or who is otherwise unwell and has returned from a malarious area.... malaria

An acute arbovirus (see ARBOVIRUSES) infection caused by a ?avivirus of the togavirus family, transmitted from animals to humans by various species of forest mosquito (jungle/sylvan yellow fever), and from human to human by Aëdes aegypti (urban yellow fever). Mosquito transmission was shown by Walter Reed and his colleagues in 1900. It is ENDEMIC in much of tropical Africa and Central and South America but does not occur in Asia. In the urban cycle, humans constitute the reservoir of infection, and in the jungle/sylvan variety, mammals – especially subhuman primates – are involved in transmission. Historically, yellow fever was enormously important, causing devastating epidemics (see EPIDEMIC); it also carried a high mortality rate in travellers and explorers. Differentiation from other infections associated with JAUNDICE was often impossible.

Clinically, yellow fever is characterised by jaundice, fever, chills, headache, gastrointestinal haemorrhage(s), and ALBUMINURIA. The incubation period is 3–6 (up to 10) days. Differentiation from viral hepatitides, other viral haemorrhagic fevers, severe Plasmodium falciparum malaria, and several other infections is often impossible without sophisticated investigative techniques. Infection carries a high mortality rate. Liver histology (biopsy is contraindicated due to the haemorrhagic diathesis) shows characteristic changes; a fulminating hepatic infection is often present. Acute in?ammation of the kidneys and an in?amed, congested gastric mucosa, often accompanied by haemorrhage, are also demonstrable; myocardial involvement often occurs. Diagnosis is primarily based on virological techniques; serological tests are also of value. Yellow fever should be suspected in any travellers from an endemic area.

Management consists of instituting techniques for acute hepatocellular (liver-cell) failure. The affected individual should be kept in an isolation unit, away from mosquitoes which could transmit the disease to a healthy individual. Formerly, laboratory infections were occasionally acquired from infected blood samples. Prophylactically, a satisfactory attenuated VACCINE (17D) has been available for around 60 years; this is given subcutaneously and provides an individual with excellent protection for ten years; international certi?cates are valid for this length of time. Every traveller to an endemic area should be immunised; this is mandatory for entry to countries where the infection is endemic.... yellow fever

The generic name of a widely distributed group of mosquitoes, certain species of which transmit to humans the parasitic protozoa Plasmodium, the agent that causes MALARIA. Anopheles maculipennis and A. bifurcatus are both found in England and can both transmit the malaria parasite.... anopheles

A virus disease, caused by a phlebovirus and transmitted by mosquitoes, at one time con?ned to sub-Saharan Africa and predominantly found in domestic animals such as cattle, sheep and goats. The only humans affected were veterinary surgeons, butchers and others exposed to heavy infection by direct contact with infected animals; these usually recovered. In the 1970s the disease ?ared up in Egypt, probably owing to a more virulent virus. The illness in humans is characterised by fever, haemorrhages, ENCEPHALITIS and involvement of the EYE. An e?ective vaccine protects both animals and human beings against the disease (see IMMUNISATION).... rift valley fever

Acquired Immune De?ciency Syndrome (AIDS) is the clinical manifestation of infection with Human Immunode?ciency Virus (HIV). HIV belongs to the retroviruses, which in turn belong to the lentiviruses (characterised by slow onset of disease). There are two main HIV strains: HIV-1, by far the commonest; and HIV-2, which is prevalent in Western Africa (including Ivory Coast, Gambia, Mali, Nigeria and Sierra Leone). HIV attacks the human immune system (see IMMUNITY) so that the infected person becomes susceptible to opportunistic infections, such as TUBERCULOSIS, PNEUMONIA, DIARRHOEA, MENINGITIS and tumours such as KAPOSI’S SARCOMA. AIDS is thus the disease syndrome associated with advanced HIV infection.

Both HIV-1 and HIV-2 are predominantly sexually transmitted and both are associated with secondary opportunistic infections. However, HIV-2 seems to result in slower damage to the immune system. HIV-1 is known to mutate rapidly and has given rise to other subtypes.

HIV is thought to have occurred in humans in the 1950s, but whether or not it infected humans from another primate species is uncertain. It became widespread in the 1970s but its latency in causing symptoms meant that the epidemic was not noticed until the following decade. Although it is a sexually transmitted disease, it can also be transmitted by intravenous drug use (through sharing an infected needle), blood transfusions with infected blood (hence the importance of e?ective national blood-screening programmes), organ donation, and occupationally (see health-care workers, below). Babies born of HIV-positive mothers can be infected before or during birth, or through breast feeding.

Although HIV is most likely to occur in blood, semen or vaginal ?uid, it has been found in saliva and tears (but not sweat); however, there is no evidence that the virus can be transmitted from these two body ?uids. There is also no evidence that HIV can be transmitted by biting insects (such as mosquitoes). HIV does not survive well in the environment and is rapidly destroyed through drying.

Prevalence At the end of 2003 an estimated 42 million people globally were infected with HIV – up from 40 million two years earlier. About one-third of those with HIV/AIDS are aged 15–24 and most are unaware that they are carrying the virus. During 2003 it is estimated that 5 million adults and children worldwide were newly infected with HIV, and that 3 million adults and children died. In Africa in 2003,

3.4 million people were newly infected and 2.3 million died, with more than 28 million carrying the virus. HIV/AIDS was the leading cause of death in sub-Saharan Africa where over half of the infections were in women and 90 per cent of cases resulted from heterosexual sex. In some southern African countries, one in three pregnant women had HIV.

In Asia and the Paci?c there were 1.2 million new infections and 435,000 deaths. The area with the fastest-growing epidemic is Eastern Europe, especially the Russian Federation where in 2002 around a million people had HIV and there were an estimated 250,000 new infections, with intravenous drug use a key contributor to this ?gure. Seventy-?ve per cent of cases occurred in men, with male-to-male sexual transmission an important cause of infection, though heterosexual activity is a rising cause of infection.

At the end of 2002 the UK had an estimated 55,900 HIV-infected adults aged between 15 and 59. More than 3,600 individuals were newly diagnosed with the infection in 2000, the highest annual ?gure since the epidemic started

– in 1998 the ?gure was 2,817 and in 1999 just over 3,000 (Department of Health and Communicable Disease Surveillance Centre). The incidence of AIDS in the UK has declined sharply since the introduction of highly active antiretroviral therapy (HAART) and HIV-related deaths have also fallen: in 2002 there were 777 reported new AIDS cases and 395 deaths, compared with 1,769 and 1,719 respectively in 1995. (Sources: UNAIDS and WHO, AIDS Epidemic Update, December 2001; Public Health Laboratory Services AIDS and STD Centre Communicable Disease Surveillance and Scottish Centre for Infection and Environmental Health, Quarterly Surveillance Tables.)

Poverty is strongly linked to the spread of AIDS, for various reasons including lack of health education; lack of e?ective public-health awareness; women having little control over sexual behaviour and contraception; and, by comparison with the developed world, little or no access to antiretroviral drugs.

Pathogenesis The cellular target of HIV infection is a subset of white blood cells called T-lymphocytes (see LYMPHOCYTE) which carry the CD4 surface receptor. These so-called ‘helper T-cells’ are vital to the function of cell-mediated immunity. Infection of these cells leads to their destruction (HIV replicates at an enormous rate – 109) and over the course of several years the body is unable to generate suf?cient new cells to keep pace. This leads to progressive destruction of the body’s immune capabilities, evidenced clinically by the development of opportunistic infection and unusual tumours.

Monitoring of clinical progression It is possible to measure the number of viral particles present in the plasma. This gives an accurate guide to the likely progression rate, which will be slow in those individuals with fewer than 10,000 particles per ml of plasma but progressively more rapid above this ?gure. The main clinical monitoring of the immune system is through the numbers of CD4 lymphocytes in the blood. The normal count is around 850 cells per ml and, without treatment, eventual progression to AIDS is likely in those individuals whose CD4 count falls below 500 per ml. Opportunistic infections occur most frequently when the count falls below 200 per ml: most such infections are treatable, and death is only likely when the CD4 count falls below 50 cells per ml when infection is developed with organisms that are di?cult to treat because of their low intrinsic virulence.

Simple, cheap and highly accurate tests are available to detect HIV antibodies in the serum. These normally occur within three months of infection and remain the cornerstone of the diagnosis.

Clinical features Most infected individuals have a viral illness some three weeks after contact with HIV. The clinical features are often non-speci?c and remain undiagnosed but include a ?ne red rash, large lymph nodes, an in?uenza-like illness, cerebral involvement and sometimes the development of opportunistic infections. The antibody test may be negative at this stage but there are usually high levels of virus particles in the blood. The antibody test is virtually always positive within three months of infection. HIV infection is often subsequently asymptomatic for a period of ten years or more, although in most patients progressive immune destruction is occurring during this time and a variety of minor opportunistic infections such as HERPES ZOSTER or oral thrush (see CANDIDA) do occur. In addition, generalised LYMPHADENOPATHY is present in a third of patients and some suffer from severe malaise, weight loss, night sweats, mild fever, ANAEMIA or easy bruising due to THROMBOCYTOPENIA.

The presentation of opportunistic infection is highly variable but usually involves either the CENTRAL NERVOUS SYSTEM, the gastrointestinal tract or the LUNGS. Patients may present with a sudden onset of a neurological de?cit or EPILEPSY due to a sudden onset of a STROKE-like syndrome, or epilepsy due to a space-occupying lesion in the brain – most commonly TOXOPLASMOSIS. In late disease, HIV infection of the central nervous system itself may produce progressive memory loss, impaired concentration and mental slowness called AIDS DEMENTIA. A wide variety of opportunistic PROTOZOA or viruses produces DYSPHAGIA, DIARRHOEA and wasting. In the respiratory system the commonest opportunistic infection associated with AIDS, pneumonia, produces severe shortness of breath and sometimes CYANOSIS, usually with a striking lack of clinical signs in the chest.

In very late HIV infection, when the CD4 count has fallen below 50 cells per ml, infection with CYTOMEGALOVIRUS may produce progressive retinal necrosis (see EYE, DISORDERS OF) which will lead to blindness if untreated, as well as a variety of gastrointestinal symptoms. At this stage, infection with atypical mycobacteria is also common, producing severe anaemia, wasting and fevers. The commonest tumour associated with HIV is Kaposi’s sarcoma which produces purplish skin lesions. This and nonHodgkin’s lymphoma (see LYMPHOMA), which is a hundred times more frequent among HIV-positive individuals than in the general population, are likely to be associated with or caused by opportunistic viral infections.

Prevention There is, as yet, no vaccine to prevent HIV infection. Vaccine development has been hampered

by the large number of new HIV strains generated through frequent mutation and recombination.

because HIV can be transmitted as free virus and in infected cells.

because HIV infects helper T-cells – the very cells involved in the immune response. There are, however, numerous research pro

grammes underway to develop vaccines that are either prophylactic or therapeutic. Vaccine-development strategies have included: recombinant-vector vaccines, in which a live bacterium or virus is genetically modi?ed to carry one or more of the HIV genes; subunit vaccines, consisting of small regions of the HIV genome designed to induce an immune response without infection; modi?ed live HIV, which has had its disease-promoting genes removed; and DNA vaccines – small loops of DNA (plasmids) containing viral genes – that make the host cells produce non-infectious viral proteins which, in turn, trigger an immune response and prime the immune system against future infection with real virus.

In the absence of an e?ective vaccine, preventing exposure remains the chief strategy in reducing the spread of HIV. Used properly, condoms are an extremely e?ective method of preventing exposure to HIV during sexual intercourse and remain the most important public-health approach to countering the further acceleration of the AIDS epidemic. The spermicide nonoxynol-9, which is often included with condoms, is known to kill HIV in vitro; however, its e?ectiveness in preventing HIV infection during intercourse is not known.

Public-health strategies must be focused on avoiding high-risk behaviour and, particularly in developing countries, empowering women to have more control over their lives, both economically and socially. In many of the poorer regions of the world, women are economically dependent on men and refusing sex, or insisting on condom use, even when they know their partners are HIV positive, is not a straightforward option. Poverty also forces many women into the sex industry where they are at greater risk of infection.

Cultural problems in gaining acceptance for universal condom-use by men in some developing countries suggests that other preventive strategies should also be considered. Microbicides used as vaginal sprays or ‘chemical condoms’ have the potential to give women more direct control over their exposure risk, and research is underway to develop suitable products.

Epidemiological studies suggest that male circumcision may o?er some protection against HIV infection, although more research is needed before this can be an established public-health strategy. Globally, about 70 per cent of infected men have acquired the virus through unprotected vaginal sex; in these men, infection is likely to have occurred through the penis with the mucosal epithelia of the inner surface of the foreskin and the frenulum considered the most likely sites for infection. It is suggested that in circumcised men, the glans may become keratinised and thus less likely to facilitate infection. Circumcision may also reduce the risk of lesions caused by other sexually transmitted disease.

Treatment AIDS/HIV treatment can be categorised as speci?c therapies for the individual opportunistic infections – which ultimately cause death – and highly active antiretroviral therapy (HAART) designed to reduce viral load and replication. HAART is also the most e?ective way of preventing opportunistic infections, and has had a signi?cant impact in delaying the onset of AIDS in HIV-positive individuals in developed countries.

Four classes of drugs are currently in use. Nucleoside analogues, including ZIDOVUDINE and DIDANOSINE, interfere with the activity of the unique enzyme of the retrovirus reverse transcriptase which is essential for replication. Nucleotide analogues, such as tenofovir, act in the same way but require no intracellular activation. Non-nucleoside reverse transcriptase inhibitors, such as nevirapine and EFAVIRENZ, act by a di?erent mechanism on the same enzyme. The most potent single agents against HIV are the protease inhibitors, such as lopinavir, which render a unique viral enzyme ineffective. These drugs are used in a variety of combinations in an attempt to reduce the plasma HIV viral load to below detectable limits, which is achieved in approximately 90 per cent of patients who have not previously received therapy. This usually also produces a profound rise in CD4 count. It is likely, however, that such treatments need to be lifelong – and since they are associated with toxicities, long-term adherence is di?cult. Thus the optimum time for treatment intervention remains controversial, with some clinicians believing that this should be governed by the viral load rising above 10,000 copies, and others that it should primarily be designed to prevent the development of opportunistic infections – thus, that initiation of therapy should be guided more by the CD4 count.

It should be noted that the drug regimens have been devised for infection with HIV-1; it is not known how e?ective they are at treating infection with HIV-2.

HIV and pregnancy An HIV-positive woman can transmit the virus to her fetus, with the risk of infection being particularly high during parturition; however, the risk of perinatal HIV transmission can be reduced by antiviral drug therapy. In the UK, HIV testing is available to all women as part of antenatal care. The bene?ts of antenatal HIV testing in countries where antiviral drugs are not available are questionable. An HIV-positive woman might be advised not to breast feed because of the risks of transmitting HIV via breastmilk, but there may be a greater risk associated with not breast feeding at all. Babies in many poor communities are thought to be at high risk of infectious diseases and malnutrition if they are not breast fed and may thus be at greater overall risk of death during infancy.

Counselling Con?dential counselling is an essential part of AIDS management, both in terms of supporting the psychological wellbeing of the individual and in dealing with issues such as family relations, sexual partners and implications for employment (e.g. for health-care workers). Counsellors must be particularly sensitive to culture and lifestyle issues. Counselling is essential both before an HIV test is taken and when the results are revealed.

Health-care workers Health-care workers may be at risk of occupational exposure to HIV, either through undertaking invasive procedures or through accidental exposure to infected blood from a contaminated needle (needlestick injury). Needlestick injuries are frequent in health care – as many as 600,000 to 800,000 are thought to occur annually in the United States. Transmission is much more likely where the worker has been exposed to HIV through a needlestick injury or deep cut with a contaminated instrument than through exposure of mucous membranes to contaminated blood or body ?uids. However, even where exposure occurs through a needlestick injury, the risk of seroconversion is much lower than with a similar exposure to hepatitis C or hepatitis B. A percutaneous exposure to HIV-infected blood in a health-care setting is thought to carry a risk of about one infection per 300 injuries (one in 1,000 for mucous-membrane exposure), compared with one in 30 for hepatitis C, and one in three for hepatitis B (when the source patient is e-antigen positive).

In the event of an injury, health-care workers are advised to report the incident immediately where, depending on a risk assessment, they may be o?ered post-exposure prophylaxis (PEP). They should also wash the contaminated area with soap and water (but without scrubbing) and, if appropriate, encourage bleeding at the site of injury. PEP, using a combination of antiretroviral drugs (in a similar regimen to HAART – see above), is thought to greatly reduce the chances of seroconversion; it should be commenced as soon as possible, preferably within one or two hours of the injury. Although PEP is available, safe systems of work are considered to o?er the greatest protection. Double-gloving (latex gloves remove much of the blood from the surface of the needle during a needlestick), correct use of sharps containers (for used needles and instruments), avoiding the resheathing of used needles, reduction in the number of blood samples taken from a patient, safer-needle devices (such as needles that self-blunt after use) and needleless drug administration are all thought to reduce the risk of exposure to HIV and other blood-borne viruses. Although there have been numerous cases of health-care workers developing HIV through occupational exposure, there is little evidence of health-care workers passing HIV to their patients through normal medical procedures.... aids/hiv

A heterogenous group of around 500 viruses, which are transmitted to humans by ARTHROPODS. Grouped in four families, they include the viruses of DENGUE and YELLOW FEVER which are transmitted by mosquitoes.... arboviruses

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

An arboviral disease in Australia transmitted by mosquitoes.... australian encephalitis

Assessment of the efficacy and persistence of an insecticidal treatment by exposing mosquitoes of known susceptibility to a treated surface or area for a standard period of time.... bioassay

A plant in the family which includes pineapples. They often have small collections of water at the base of the leaves and are favoured breeding places of Aedes aegypti and other mosquitoes.... bromeliad

An insecticide which has been used sucessfully against ?ies and mosquitoes resistant to DDT (see DICHLORODIPHENYL TRICHLOROETHANE), and for the control of ticks and mites. It requires special handling as it is toxic to humans when applied to the skin.... chlordane

A chemical used for immobilising mosquitoes to facilitate their handling. It is toxic and should be used with extreme care.... chloroform

Cocos nucifera

Description: This tree has a single, narrow, tall trunk with a cluster of very large leaves at the top. Each leaf may be over 6 meters long with over 100 pairs of leaflets.

Habitat and Distribution: Coconut palms are found throughout the tropics. They are most abundant near coastal regions.

Edible Parts: The nut is a valuable source of food. The milk of the young coconut is rich in sugar and vitamins and is an excellent source of liquid. The nut meat is also nutritious but is rich in oil. To preserve the meat, spread it in the sun until it is completely dry.

Other Uses: Use coconut oil to cook and to protect metal objects from corrosion. Also use the oil to treat saltwater sores, sunburn, and dry skin. Use the oil in improvised torches. Use the tree trunk as building material and the leaves as thatch. Hollow out the large stump for use as a food container. The coconut husks are good flotation devices and the husk’s fibers are used to weave ropes and other items. Use the gauzelike fibers at the leaf bases as strainers or use them to weave a bug net or to make a pad to use on wounds. The husk makes a good abrasive. Dried husk fiber is an excellent tinder. A smoldering husk helps to repel mosquitoes. Smoke caused by dripping coconut oil in a fire also repels mosquitoes. To render coconut oil, put the coconut meat in the sun, heat it over a slow fire, or boil it in a pot of water. Coconuts washed out to sea are a good source of fresh liquid for the sea survivor.... coconut

Most mosquitoes that are not anophelines fall into this group. Culicines are not vectors of human malaria, but the subfamily includes the important genera Aedes, Culex and Mansonia. May transmit a number of diseases (eg, yellow fever, dengue fever, filariasis, viral encephalitis).... culicine

Also known as dengue fever, breakbone fever, and dandy fever, dengue is endemic and epidemic in tropical and subtropical regions. It is an acute infection caused by a ?avivirus (family togaviridae) transmitted by mosquitoes – especially Aedes aegypti. Incubation period is 5–8 days, and is followed by abrupt onset of symptoms: fever, facial ERYTHEMA with intense itching (which spreads throughout the body), sore throat, running eyes, and painful muscles and joints are common accompaniments. The symptoms subside within a few days and are frequently succeeded by a relapse similar to the ?rst. Further relapses may occur, and joint pains continue for some months. In uncomplicated dengue the mortality rate is virtually zero. Diagnosis is by virus isolation or demonstration of a rising antibody-concentration in the acute phase of infection. There is no speci?c treatment, but mild analgesics can be used to relieve the pains, and calamine lotion the itching. Prevention can be achieved by reduction of the mosquito-vector population.

Dengue haemorrhagic fever This is a more severe form of the disease which usually occurs in young children; it is largely con?ned to the indigenous population(s) of south-east Asia. It is accompanied by signi?cant complications and mortality. Immunological status of the host is considered important in pathogenesis.... dengue

(Syn. “Breakbone fever”) A flavivirus, dengue virus types 1-4, transmitted by infected specific Aedes spp mosquitoes. Sudden abrupt onset of high fever, headache, retrobulbar pain and lumbosacral pain. Fever lasts 6-7 days and may be ‘saddleback’. Initial symptoms followed by generalised myalgia, bone pain, anorexia, nausea, vomiting and weakness. A transient mottled rash may appear on 1st/2nd day and a second rash appears with resolution of fever - at first on trunk, spreading outward. WCC and platelet count depressed. Mild haemorrhagic phenomena in a few.... dengue fever

A large net on a rigid frame, which is dropped over vegetation to collect specimens of outdoor-resting mosquitoes.... drop net

Fertilised female reproductive cells (ova) with nutrient material, e.g. those deposited by female mosquitoes and developing in water to produce free-swimming larvae.... eggs

Chronically oedematous (see OEDEMA) and thickened tissue, especially involving the lower extremities and genitalia, which arises from repeated attacks of in?ammation of the skin and subcutaneous tissue, with concurrent obstruction of lymphatic vessels. In a tropical country, the usual cause is lymphatic FILARIASIS.

Filarial elephantiasis Wuchereria bancrofti and Brugia malayi are conveyed to humans by a mosquito bite. Resultant lymphatic obstruction gives rise to enlargement and dis?guration, with thickening of the skin (resembling that of an elephant) in one or both lower limbs and occasionally genitalia (involving particularly the SCROTUM). By the time the condition is recognised, lymphatic damage is irreversible. However, if evidence of continuing activity exists, a course of diethylcarbamazine should be administered (see FILARIASIS). Relief can be obtained by using elastic bandaging, massage, rest, and elevation of the affected limb. Surgery is sometimes indicated. For prevention, destruction of mosquitoes is important.... elephantiasis

Encephalitis means in?ammation or infection of the brain, usually caused by a virus; it may also be the result of bacterial infection. It occurs throughout the world and affects all racial groups and ages. Rarely it occurs as a complication of common viral disease such as measles, mumps, glandular fever, or chickenpox. It may occur with no evidence of infection elsewhere, such as in HERPES SIMPLEX encephalitis, the most common form seen in Europe and America. RABIES is another form of viral encephalitis, and the HIV virus which causes AIDS invades the brain to cause another form of encephalitis (see AIDS/HIV). In some countries – North and South America, Japan and east Asia and Russia

– there may be epidemics spread by the bite of mosquitoes or ticks.

The clinical features begin with in?uenza-like symptoms – aches, temperature and wretchedness; then the patient develops a headache with drowsiness, confusion and neck sti?ness. Severely ill patients develop changes in behaviour, abnormalities of speech, and deterioration, sometimes with epileptic seizures. Some develop paralysis and memory loss. CT (see COMPUTED TOMOGRAPHY) and MRI brain scans show brain swelling, and damage to the temporal lobes if the herpes virus is involved. ELECTROENCEPHALOGRAPHY (EEG), which records the brainwaves, is abnormal. Diagnosis is possible by an examination of the blood or other body ?uids for antibody reaction to the virus, and modern laboratory techniques are very speci?c.

In general, drugs are not e?ective against viruses – antibiotics are of no use. Herpes encephalitis does respond to treatment with the antiviral agent, aciclovir. Treatment is supportive: patients should be given painkillers, and ?uid replacement drugs to reduce brain swelling and counter epilepsy if it occurs. Fortunately, most sufferers from encephalitis make a complete recovery, but some are left severely disabled with physical defects, personality and memory disturbance, and epileptic ?ts. Rabies is always fatal and the changes found in patients with AIDS are almost always progressive. Except in very speci?c circumstances, it is not possible to be immunised against encephalitis.

Encephalitis lethargica is one, now rare, variety that reached epidemic levels after World War I. It was characterised by drowsiness and headache leading on to COMA. The disease occasionally occurs as a complication after mumps and sometimes affected individuals subsequently develop postencephalitic PARKINSONISM.... encephalitis

Disease common in Australia and caused by the Ross River Virus, an arbovirus transmitted by mosquitoes.... epidemic polyarthritis

Devices typically placed over doors and windows of houses or animal shelters to catch mosquitoes leaving these buildings.... exit traps

Habits determining the times and places of feeding and the sources of blood meals for mosquitoes.... feeding habits

A two winged insect of the Order Diptera. Includes the housefly and the myiasis - causing flies. Also includes the mosquitoes and the tsetse flies.... fly

The proprietary name for a synthetic insecticide which is a formulation of benzene hexachloride. It is active against a large range of insects and pests, including mosquitoes, ?eas, lice, cockroaches, house-?ies, clothes moths, bed-bugs, ants, and grain pests.... gammexane

The condition of female mosquitoes during blood ingestion, ovarian development, leading to oviposition.... gonotrophic stage

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

A flavivirus, related to Murray Valley virus (see Australian Encephalitis). Rice paddybreeding Culicine mosquitoes, Culex tritaeniorhyehus, often transmit the disease. Mosquitoes are largely zoophilic. Occasionally Aedes spp and Anopholines implicated in transmission. Disease consists of prodrome, encephalitis and recovery (or death on average in 7%). Affects mostly children less than five years of age and leaves sequelae. A vaccination is available.... japanese encephalitis

A mechanical trap which use a combination of light and/or carbon dioxide to attract and trap adult mosquitoes, e.g. Centres for Disease Control and Prevention (CDC) Light Trap.... light traps

A genus of mosquitoes, some species of which can be involved in the transmission of human filariasis due to Brugia malayi and Wuchereria bancrofti.... mansonia

The process by which a disease is transmitted via micro-organisms from one person to another. The micro-organism may be a bacterium (see BACTERIA), a RICKETTSIA, a VIRUS, a protozoon – single-celled animal organism – or a metazoon – multicellular animal organism. Invasion of the body by a metazoon (e.g. by an intestinal worm) is more often known as an infestation.

The skin is an important protection against micro-organisms entering the body tissues. A large measure of protection is a?orded by the factors which ensure IMMUNITY against diseases.

Modes of infection The infective material may be transmitted to the person by direct contact with a sick person, when the disease is said to be contagious, although such a distinction is purely arti?cial. Di?erent diseases are especially infectious at di?erent periods of their course. Protecting people can be di?cult, since some diseases are infectious before the patient shows any symptoms (see INCUBATION).

Infection may be conveyed on dust, in drinking-water, in food (particularly milk), in the body’s waste products and secretions, or even on clothes and linen which have been in contact with the infected individual (called fomites).

Some people who have recovered from a disease, or who have simply been in contact with an infectious case, harbour the infectious agent. This is particularly the case in typhoid fever (see ENTERIC FEVER), the bacillus continuing to develop in the gall-bladder of some people who have had the disease for years after the symptoms have disappeared. In the case of CHOLERA, which is ENDEMIC in some developing countries with hot climates, 80 per cent or more of the population may harbour the bacillus and spread infection when other circumstances favour this. Similarly in the case of DYSENTERY, people who have completely recovered may still be capable of infecting dust and drinking-water by their stools. DIPHTHERIA and meningococcal MENINGITIS, which is particularly liable to infect children, are other examples.

Flies can infect milk and other food with the organisms causing typhoid fever and food poisoning. Mosquitoes carry the infective agents of MALARIA, DENGUE and YELLOW FEVER, these undergoing part of their development in the body of the mosquito. Fleas convey the germ of plague from rats to humans, and lice are responsible for inoculating TYPHUS FEVER and one form of RELAPSING FEVER by their bite. A tick is responsible for spreading another form of relapsing fever, and kala-azar (LEISHMANIASIS) is spread by the bites of sand?ies.

Noti?able diseases Certain of the common and most serious infectious diseases are noti?able in the United Kingdom. A doctor diagnosing someone infected by a noti?able disease must inform the authorities. For the current list of noti?able infectious diseases in the UK, see the main entry for NOTIFIABLE DISEASES.

Prevention is an important aspect of the control of infectious diseases, and various steps can be taken to check the spread of such infections as dysentery, tuberculosis, malaria and others. (See also IMMUNITY; INCUBATION.)... infection

The stages of development through which a plant or animal passes during its life. For mosquitoes these stages are: egg, larva, pupa, adult. Normally, development of nematodes included four moults and five successive stages as follows: Adult eggs • (fourth moult) ¯ • Fourth-stage larva First-stage larva • (third moult) (first moult) • Third-stage larva ¬ Second-stage larva (second moult) Generally, there are two types of life cycle for nematodes: direct and indirect types. 1. Direct Life Cycle: requires no intermediate host, after hatching from the eggs the larvae develop in the open from free-living to infective stages and gain access to the definitive host by mouth or penetration through skin. 2. Indirect Life Cycle: requires one or two intermediate hosts for development to infective stage.... life cycle

Any substance producing a negative response in mosquitoes, causing them to avoid a close approach (such as alighting on the skin of a host animal or entering a treated room). (See also DEET).... mosquito repellent

The proportion of female mosquitoes that have laid eggs at least once. Use for age-grading a mosquito population.... parous rate

Mentha pulegium. N.O. Labiateae.

Synonym: European Pennyroyal.

Habitat: Not common as a wild plant, except on damp heaths and commons. Frequently seen in cottage gardens. Indigenous to Britain and Europe.

Features ? This member of the mint family grows up to twelve inches high, the stem

being bluntly quadrangular. The one to one and a half inch long, egg-shaped leaves are opposite, on short stalks ; they are slightly serrate and nearly smooth. Purple flowers appear in August. The odour is rather pungent, mint-like but characteristic.

Part used ? The whole herb.

Action: Carminative, emmenagogue, diaphoretic and stimulant.

An infusion of 1 ounce to 1 pint of boiling water, taken warm in teacupful doses frequently repeated, is helpful in hysteria, flatulence and sickness. For children's ailments such as feverish colds, disordered stomach and measles, Pennyroyal infusion may be given in appropriate doses with confidence. Its diaphoretic and stimulant action recommends it for chills and incipient fevers, and the infusion works as an emmenagogue when such ailments retard and obstruct menstruation. The oil of Pennyroyal is a first-rate protection against the bites of mosquitoes, gnats, and similar winged pests. The herb is used to some extent as a flavouring. Although not so popular as other herbs for this purpose, the mint-like flavour and carminative virtues of Pennyroyal should recommend it to cooks as adding to both palatability and digestibility of various dishes.

American or Mock Pennyroyal are the names given to the dried leaves and flowering tops of Hedeoma pulegioides. This plant, although quite different in appearance from the European Pennyroyal, has similar medicinal values.... pennyroyal

The habits determining the places and times of day or night that mosquitoes rest.... resting habits

The proportion of female mosquitoes that have sporozoites in the salivary gland.... sporozoite rate

The monitoring of changes in the numbers of mosquitoes or disease cases over a period of time.... surveillance

Nets used to sample the living mosquito population. By permitting access to a bait but restricting movement away from it, trap nets tend to concentrate female mosquitoes near the bait.... trap nets

A mosquito-borne viral infection that is normally harmless to healthy people who, if infected, develop a mild ?u-like illness. However, if the elderly and those in poor health, particularly immunocompromised patients, are infected, they may develop fatal in?ammation of the brain and spinal cord. In Israel in 2000, 12 people died and more than 155 survived an outbreak; and in New York in 1999, more than 60 people were infected, of whom six died. The disease was ?rst reported in Uganda in 1937 and became ENDEMIC in the Middle East and Africa, recently spreading to Europe, central Asia, Oceania and America. Mosquitoes bearing the ?aviviridae-family virus usually contract it by biting infected poultry, but the infection has been found in mammals, such as cats, dogs and horses.... west nile virus

Anacardium occidentale L. Active ingredient: anacardic acid – an inhibitor of prostaglandin synthetase. Kills laval mosquitoes and water snails. Dumped by natives into ponds where mosquitoes and snails breed. The apple-like fruit serves as a pesticide to control malaria, schistosomiasis and other parasitic diseases from drinking water. (Dr Isao Kubo, University of California-Berkeley, USA)

Leaves used by natives of West Africa for malaria. ... cashew tree fruit

Oils: Lavender, Pennyroyal, Cloves, Thyme. Apply to exposed areas. Avoid contact with mucous membranes.

Popular Indian: 2-3 drops oil Citronella on handkerchief and dabbed behind ears, on neck, hair, etc. Garlic repels all insects and beetles. Cedarwood essential oil kills houseflies, mosquitoes and cockroaches in concentrations of less than 1 per cent. (Central Institute for Medicinal Plants, Lucknow) ... insect repellents

A tropical viral illness, also called dengue, that is spread by mosquitoes.... breakbone fever

n. a genus of widely distributed mosquitoes occurring throughout the tropics and subtropics. Most species are black with distinct white or silvery-yellow markings on the legs and thorax. Aëdes species are not only important as vectors of *dengue, *yellow fever, *filariasis, and Group B viruses causing encephalitis but also constitute a serious biting nuisance. A. aegypti is the principal vector of dengue and yellow fever.... aëdes

n. any member of a genus of *arboviruses transmitted by mosquitoes. Many alphaviruses can cause disease in humans and animals, including *O’nyong nyong fever and *Ross River fever.... alphavirus

n. a genus of threadlike parasitic worms (see filaria). B. malayi infects humans throughout southeast Asia, causing *filariasis and *elephantiasis (especially of the feet and legs). B. pahangi, a parasite of wild cats and domestic animals, produces an allergic condition in humans, with coughing, breathing difficulty, and an increase in the number of *eosinophils in the blood. Brugia undergoes part of its development in mosquitoes of the genera Anopheles and Mansonia, which transmit the parasite from host to host.... brugia

Beverage and medicine. Whilst not a herb, honey is processed by bees from the nectar of flowers and has an ethereal quality that enhances its healing properties. A source of vitamins and minerals.

Action. Many bacteria cannot live in the presence of honey since honey draws from them the moisture essential to their existence. It is a potent inhibitor of the growth of bacteria: salmonella, shigella and E. coli. Taken internally and externally, hastens granulation and arrests necrotic tissue. A natural bacteriostatic and bactericide.

Of an alkaline action, honey assists digestion, decreasing acidity. It has been used with success for burns, frostbite, colic, dry cough, inflammations, involuntary twitching of eyes and mouth; to keep a singer’s throat in condition. Some cases of tuberculosis have found it a life-preserver.

A cooling analgesic: dressings smeared with honey and left on after pain has subsided to prevent swelling – for cuts, scratches, fistula, boils, felon, animal bites; stings of mosquitoes, wasps, bees, fleas, etc. May be applied to any kind of wound: dip gauze strips in pure honey and bind infected area; leave 24 hours.

Insomnia: 2 teaspoons to glass of hot milk at bedtime.

Arterio-sclerosis: with pollen, is said to arrest thickening of the arteries.

2, 3 or more teaspoons daily to prevent colds and influenza.

2 teaspoons in water or tea for renewed vitality when tired.

Rheumatism and arthritis: 2 teaspoons honey and 2 teaspoons Cider vinegar in water 2-3 times daily.

“The taking of honey each day is advised in order to keep the lymph flowing at its normal tempo and thus avoid degenerative disease which shortens life. The real value of honey is to maintain a normal flow of the tissue fluid called lymph. When this flow-rate slows down, then calcium and iron are precipitated as sediment. When the lymph flow is stagnant, then harmful micro-organisms invade the body and sickness appears.” (D.C. Jarvis MD)

Where sweetening is required to ensure patient compliance, honey is better than sugar. Its virtues deteriorate in open sunlight. Should not be heated above 40°C. ... honey

Puncture wounds inflicted by bloodsucking insects such as gnats, mosquitoes, fleas, and lice. Most bites cause only temporary pain or itching, but some people have severe skin reactions. In the tropics and subtropics, insect bites are potentially more serious because certain biting species can transmit disease (see insects and disease).

All insect bites provoke a skin reaction to substances in the insect’s saliva or faeces, which may be deposited at or near the site of the bite. Reactions vary from red pimples to painful swellings or an intensely itching rash; some insects, such as bees and wasps, have stings (see insect stings) that can produce fatal allergies. (See also lice; spider bites; mites and disease; ticks and disease.)... insect bites

Relatively few insect species cause disease directly in humans. Some parasitize humans, living under the skin or on the body surface (see lice; chigoe; myiasis). The most troublesome insects are flies and biting insects. Flies can carry disease organisms from human or animal excrement via their feet or legs and contaminate food or wounds.

A number of serious diseases are spread by biting insects.

These include malaria and filariasis (transmitted by mosquitoes), sleeping sickness (tsetse flies), leishmaniasis (sandflies), epidemic typhus (lice), and plague (rat fleas).

Mosquitoes, sandflies, and ticks can also spread illnesses such as yellow fever, dengue, Lyme disease, and some types of viral encephalitis.

Organisms picked up when an insect ingests blood from an infected animal or person are able to survive or multiply in the insect.

Later, the organisms are either injected into a new human host via the insect’s saliva or deposited in the faeces at or near the site of the bite.

Most insect-borne diseases are confined to the tropics and subtropics, although tick-borne Lyme disease occurs in some parts of the.

The avoidance of insect-borne disease is largely a matter of keeping flies off food, discouraging insect bites by the use of suitable clothing and insect repellents, and, in parts of the world where malaria is present, the use of mosquito nets and screens, pesticides, and antimalarial tablets.... insects and disease

Mosquitoes are flying insects found throughout the world. The females bite humans or animals to obtain blood, which they need to produce eggs. The males do not bite. A doctor should be consulted if there is a severe skin reaction to a mosquito bite.

As well as being irritating, mosquito bites can also transmit diseases. The main disease-transmitting mosquitoes belong to 3 groups: ANOPHELES (which transmits malaria), AEDES (which carries yellow fever), and CULEX (which transmits filariasis).

Preventive measures should be taken in any area where mosquitoes are rampant. The most effective measures are wearing long sleeves and socks, placing mosquito screens over windows, and using insect-repellent sprays or slowburning coils that release insecticidal smoke. Mosquito nets should be placed over beds. (See also insect bites; insects and disease.)... mosquito bites

a disease caused by an *arbovirus and transmitted to humans by mosquitoes of the genus Aëdes. The disease is similar to *dengue and symptoms include fever, headache, joint and muscle pain, and an irritating rash. The patient is given drugs to relieve the pain and reduce the fever; the joint pain, which may progress to arthritis, can persist for up to three years after the infection. Chikungunya was first reported in Tanzania in 1952 and has since occurred in over sixty countries worldwide.... chikungunya fever

n. a genus of mosquitoes, worldwide in distribution, of which there are some 600 species. Certain species are important as vectors of filariasis (see also Wuchereria) and viral encephalitis.... culex

n. an agent that destroys mosquitoes or gnats.... culicide

n. a genus of nonbloodsucking flies inhabiting lowland woods and forests of South and Central America. The parasitic maggots of D. hominis can cause a serious disease of the skin in humans (see myiasis). The maggots burrow into the skin, after emerging from eggs transported by bloodsucking insects (e.g. mosquitoes), and produce painful boil-like swellings. Treatment involves surgical removal of the maggots.... dermatobia

n. a large group of insects, including *mosquitoes, gnats, midges, house flies, and *tsetse flies, that possess a single pair of wings. The mouthparts of many species, e.g. mosquitoes and tsetse flies, are specialized for sucking blood; these forms are important in the transmission of disease (see vector). See also fly.... diptera

n. a disease, common in the tropics and subtropics, caused by the presence in the lymph vessels of the parasitic nematode worms Wuchereria bancrofti and Brugia malayi (see filaria). The worms, which are transmitted to humans by various mosquitoes (including Aëdes, Culex, Anopheles, and Mansonia), bring about inflammation and eventual blocking of lymph vessels, which causes the surrounding tissues to swell (see elephantiasis). The rupture of urinary lymphatics may lead to the presence of *chyle in the urine. Filariasis is treated with the drug *diethylcarbamazine.... filariasis

n. any member of a genus (and family) of *arboviruses that cause a wide range of diseases in vertebrates (including humans). Transmitted by ticks or mosquitoes, these include *yellow fever, *dengue, *Kyasanur Forest disease, *Russian spring-summer encephalitis, and *West Nile fever.... flavivirus

n. a small winged bloodsucking insect belonging to a large group – the *Diptera (two-winged flies). Its mouthparts are formed into a long proboscis for piercing the skin and sucking blood. Female mosquitoes transmit the parasites responsible for several major infectious diseases, such as *malaria. The mosquito-borne zika virus has recently been shown to cause *microcephaly. See Anopheles; Aëdes; Culex.... mosquito

(joint-breaker fever) a disease of Africa and Malaysia, caused by an *arbovirus and transmitted by mosquitoes of the genus *Anopheles. It is similar to *dengue and symptoms include rigor, severe headache, an irritating rash, fever, and pains in the joints. The patient is given drugs to relieve the pain and fever.... o’nyong nyong fever

the branch of medicine whose main aim is the prevention of disease. This is a wide field, in which workers tackle problems ranging from the immunization of persons against infectious diseases, such as diphtheria or whooping cough, to finding methods of eliminating *vectors, such as malaria-carrying mosquitoes. See primary prevention; secondary prevention; tertiary prevention. See also World Health Organization.... preventive medicine

a viral disease caused by an *alphavirus transmitted by mosquitoes. Various vertebrates can be infected, and wild rodents may be reservoirs of the infection. The virus can cause epidemics of *polyarthritis and skin rashes (macules and papules). It occurs in Australia and the western Pacific region.... ross river fever

n. a genus of white threadlike parasitic worms (see filaria) that live in the lymphatic vessels. W. bancrofti is a tropical and subtropical species that causes *elephantiasis, lymphangitis, and chyluria. The immature forms concentrate in the lungs during the day. At night they become more numerous in the blood vessels of the skin, from which they are taken up by blood-sucking mosquitoes, acting as carriers of the diseases they cause.... wuchereria

Juniperus virginiana

FAMILY: Cupressaceae

SYNONYMS: Red cedar, eastern red cedar, southern red cedar, Bedford cedarwood (oil).

GENERAL DESCRIPTION: A coniferous, slow-growing, evergreen tree up to 33 metres high with a narrow, dense and pyramidal crown, a reddish heartwood and brown cones. The tree can attain a majestic stature with a trunk diameter of over 1.5 metres.

DISTRIBUTION: Native to North America, especially mountainous regions east of the Rocky Mountains.

OTHER SPECIES: There are many cultivars of the red cedar; its European relative is the shrubby red cedar (J. sabina) also known as savin – see entry. It is also closely related to the East African cedarwood (J. procera).

HERBAL/FOLK TRADITION: The North American Indians used it for respiratory infections, especially those involving an excess of catarrh. Decoctions of leaves, bark, twigs and fruit were used to treat a variety of ailments: menstrual delay, rheumatism, arthritis, skin rashes, venereal warts, gonorrhoea, pyelitis and kidney infections.

It is an excellent insect and vermin repellent (mosquitoes, moths, woodworm, rats, etc.) and was once used with citronella as a commercial insecticide.

ACTIONS: Abortifacient, antiseborrhoeic, antiseptic (pulmonary, genito-urinary), antispasmodic, astringent, balsamic, diuretic, emmenagogue, expectorant, insecticide, sedative (nervous), stimulant (circulatory).

EXTRACTION: Essential oil by steam distillation from the timber waste, sawdust, shavings, etc. (At one time a superior oil was distilled from the red heartwood, from trees over twenty five years old.)

CHARACTERISTICS: A pale yellow or orange oily liquid with a mild, sweet-balsamic, ‘pencil wood’ scent. It blends well with sandalwood, rose, juniper, cypress, vetiver, patchouli and benzoin.

PRINCIPAL CONSTITUENTS: Mainly cedrene (up to 80 per cent), cedrol (3–14 per cent), and cedrenol, among others.

SAFETY DATA: Externally the oil is relatively non-toxic; can cause acute local irritation and possible sensitization in some individuals. Use in dilution only with care, in moderation. ‘The oil is a powerful abortifacient … use of the oil has been fatal.’. Avoid during pregnancy. Generally safer to use Atlas cedarwood.

AROMATHERAPY/HOME: USE

Skin Care: Acne, dandruff, eczema, greasy hair, insect repellent, oily skin, psoriasis.

Circulation, Muscles And Joints: Arthritis, rheumatism.

Respiratory System: Bronchitis, catarrh, congestion, coughs, sinusitis.

Genito-Urinary System: Cystitis, leucorrhoea.

Nervous System: Nervous tension and stress-related disorders.

OTHER USES: Extensively used in room sprays and household insect repellents. Employed as a fragrance component in soaps, cosmetics and perfumes. Used as the starting material for the isolation of cedrene.... cedarwood, virginian