The mosquito changed the course of history. When irrigation canals built by the Babylonians joined the Tigris and Euphrates rivers, a vast swamp developed and became infested with malaria. It was here Alexander the Great and his powerful army lost - to malaria.
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Zika mosquito (Aedes) before and after feeding; Zika victim, Brazil
Dr Abe V Rotor
Living with Nature School on Blog [avrotor.blogspot.com]
Zika mosquito (Aedes) before and after feeding; Zika victim, Brazil
Dr Abe V Rotor
Living with Nature School on Blog [avrotor.blogspot.com]
Paaralang Bayan sa Himpapawid (People's School-on-Air) with Ms Melly C Tenorio
738 DZRB AM Band, 8 to 9 evening class Monday to Friday
Virtually no one escapes this cosmopolitan uncanny vampire, that hardly a day passes without sustaining a surreptitious bite from it.
The mosquito follows wherever man goes, and oftentimes is even ahead in the frontiers. Its is there in the polar regions of Siberia, marshes of tropical America and Asia, at the Dead Sea basin, 1,300 feet below sea level, and on the Andes and Himalayas.
They come in armies or swarms but are not true colonies like those of the bees and ants. Swarming is just an accident of enormous population buildup concentrated in a local breeding area.
The mosquito changed the course of history. When irrigation canals built by the Babylonians joined the Tigris and Euphrates rivers, a vast swamp developed and became infested with malaria. It was here Alexander the Great and his powerful army lost - to malaria.
The mosquito has successfully defended the wildlife bastions such as the Amazon, the jungles of India and Africa, and the forest islands of the Pacific. The development of the tropics - the mosquito belt - was retarded for centuries, and mosquitoes almost prevented the building of the Panama and Suez Canals.
The mosquito occupies a vital link in the food chain, being a major food source for fish and amphibians. Fishes feed upon its larvae, the wrigglers, while the adults are frog's favorite. Man's dependence on fish, - which are dependent on mosquitoes in turn - places him at the apex of the food pyramid. There is only one guarantee that man continues to occupy this position - if he is willing to shed blood for it. Without blood, mosquito eggs fail to hatch and without a sip once in every 25 generations, its particular generation dies out, thus breaking the food chain and toppling the food pyramid.
In today's modern living, with technological breakthroughs in pests and disease control, human encounters with the once dreaded mosquito have been reduced mainly to physical annoyance and "pesky" problems. This is not however, entirely true as we shall see later.
Here are some questions commonly raised about the mosquito, and their scientific answers to update our acquaintance with our old enemy and friend.
Q. Do mosquitoes bite only warm-blooded animals?
A. In general yes, but there are also species of mosquitoes that bite turtles and snakes.
Q. Do all mosquitoes bite?
A. Only the female mosquito does. The regular food of adult, male mosquitoes is plant sap and nectar.
Q. How are mosquitoes able to locate their suitable hosts?
A. They have chemoreceptors - a combination of smell and touch - located at the plumose antennae and hairy legs. These are sensitive to heat waves and odor emitted by the hosts.
Q. Do mosquitoes invade places far from their breeding grounds?
A. Yes, although they seldom travel farther than 1000 feet from their birthplace. Mass raids have been monitored to as far as 50 to 75 miles away, the swarm usually riding on air currents.
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The British named their bombers and reconnaissance planes in World War II, Mosquito, so with the Italians for their anti-tank rockets – a tribute to the superb agility of this pesky minutia.
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Q. What is the needle of the mosquito made of?
A. Actually it is a sheath bundle of modified mouthparts, the equivalent of teeth, lips and whiskers elongated to form a drill, siphon, probe and guide and rolled into a needle or proboscis.
Q. How can this tiny needle penetrate tough skin and clothing?
A. It works on the principle of jackhammer with high frequency.
Q. What prevents blood from clotting in the body of the mosquito?
A. The blood, before it is sucked, is first thinned by the mosquito's saliva, which contains an anti-coagulant substance. It has also an anesthesia effect on the host.
Q. Is this the reason why we do not feel a mosquito bite at once?
A. Yes, and probably the location of the bite is away from a nerve.
Q. Why do mosquitoes make their presence known by buzzing near the ear?
A. This is not true. They simply whine and emit short wave buzzing which is picked up when passing near the ear. (Wing beat is 600 per second, and the cymbal sound-producing membrane vibrates nearly 7000 cycles per second.).
Q. How do you recognize disease-carrying species from one another?
A. Anopheles, the malaria carrier has its head, body, and proboscis in straight line to each other but at an angle to the resting surface. It has spotted colorings on the wings. Its wrigglers lie parallel to the water surface.
Culex, the carrier of viral encephalitis and filariasis holds its body parallel to the resting surface. Its scaly proboscis is bent and uniform in color. Its wrigglers are slender and long with breathing tubes covered with hair tufts.
Aedes, the carrier of yellow fever, dengue and encephalitis, holds body parallel to the resting surface with proboscis bent down, thorax silvery with white markings. Its wrigglers are short and stout with breathing tubes containing a pair of tufts. They hang from the water surface at 45 degrees angle.
When you see a mosquito resting, or wrigglers hanging down from the surface of a pond, use the above reference.
Q. How serious is Dengue fever? How can it be controlled?
A. The disease threatens two billion people in 100 countries. In 1998 alone, 514 died of Dengue in the Philippines with one death for every 100 patients who were mostly children. Metro Manila had the highest incidence with more than six thousand cases. Since the disease is specifically transmitted by Aedes egpypti, the key to the control of the disease is the extermination of the breeding places of the mosquito vector.
Q. Do mosquitoes follow certain feeding hours?
A. Yes. For example, the Anopholes or malarial mosquito bites chiefly in the evening and early morning, while the Aedes bites during the day.
Q. How fast do mosquitoes multiply?
A. In a year's time there may be from 15 to 20 generations produced. At the normal rate of 100 eggs laid per generation, a common mosquito could spawn 31 billion descendants in six generations.
Q. What attracts mosquitoes?
A. They are attracted by the regular breathing, color and texture of clothing, and odor. Dr. A. Brown of the University of Ontario reported that the rate of breathing is the principal factor in attracting mosquitoes. He also found that only one-tenth landed on white clothing than on dark or black material. The texture most avoided is luminescent satin. A person who has not taken a bath gets more mosquito bites. Try it.
Q. What is the best insecticide to make our homes "mosquito- proof?"
A. When DDT was not yet banned, 200 milligrams of the powder could give effective proofing from 6 to 12 months. Dieldrin at 50 milligrams gives a three-month proofing. Carbamates, like Sevin, are preferred. Even if they have shorter residual effect, they are safer to health and the environment. Eucalyptus trees in the surroundings repel mosquitoes. Now and then smudge the area by burning dried leaves of Eucalyptus specially in the afternoon.
Q. Do mosquitoes develop resistance to chemicals?
A. Yes, through biological specialization, survivors from previous sprayings tend to carry on a certain degree of resistance, which could be passed on to the next generation. Chemical control should be judiciously practiced to cushion this phenomenon. Return to plant derivative insecticide like pyrethrum, rotenone, nicotine and derris is highly recommended.
Q. How does a film of oil on water kill mosquito wrigglers?
A. When they stick their tails out of the water to breath, the oil slick clogs the breathing tube, thus resulting to asphyxiation.
Q. If it is impractical to drain the breeding ground of mosquitoes, how do we get rid of wrigglers and pupae?
A. Keep the water free from organic matter and scum which are food of wrigglers. Better still, put some fish, like kataba (Poecilia) and Gambusia, to feed on them.
Q. Do mosquitoes fight each other?
A. They seldom engage in combat, but there are species, which have preying habits. These are Toxorphynchites nornatus, T. splendens, and T. brevipalpis which were introduced into Hawaii, Fiji, Australia and Southeast Asia to control pest mosquitoes. Their wrigglers are larger and larvivorous, feeding on the smaller wrigglers of other mosquito species.
Next time a mosquito comes buzzing around your ears, take the message seriously because it is the world’s deadliest creature. More people have died because of its bite than all who perished in all wars combined.
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GETTYZika virus: 1.5 million people xxx infectedThe risk in Europe is highest on the island of Madeira and the north-eastern coast of the Black Sea, according to the World Health Organisation.
In its first assessment of the threat Zika poses to Europe, the WHO’s European office classified the overall risk as small to moderate.
In February the WHO declared a global health emergency over the Zika virus. The outbreak has now spread to more than 50 countries.
Here is everything you need to know about the disease, symptoms and ways to prevent its spread.
It is an “arbovirus” - spread by mosquitoes and belongs to the same family as dengue fever and the chikungunya virus.
Because the virus has been so rare prior to 2015, there has been little research in to the virus, meaning it is difficult to clinically diagnose someone.
In some cases, Zika virus is transmitted through sex.
In May 2015 Zika virus was first reported in Brazil. The disease has since struck other parts of South America as well as Central America, the Caribbean and Pacific Islands.
The illness is mild with symptoms lasting several days to a week. Those who have it are advised to rest, drink plenty of fluids and take medicines to reduce pain and fever.
Because four out of five don’t develop symptoms, virologists are concerned that it could be easily spread by people who don’t know they have the Zika virus.
Microcephaly is a birth defect being associated to women who have been infected by the virus. It is caused by below normal brain development in utero.
Babies born with the birth defect have a below-average head size often caused by failure of brain to grow at a healthy and normal rate.
There is a link between birth defects and the Zika virus The severity can vary, but some babies are left with brains so underdeveloped they might experience walking, sight, hearing and learning difficulties.
Children who survive face severe disabilities and possible seizures.
The rates of microcephaly in Brazil shot up by 1,792 per cent between 2013 and 2015.
People should avoid getting bitten by using insect repellents, covering up with long-sleeved clothes and keep doors and windows closed.
Pregnant women should not travel to affected areas.
Male travellers should wear condoms to prevent the transmission of Zika virus through sex.
THE Zika virus, which is causing panic across the Americas, could be passed on through sex, findings suggest.
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Two cases have been unearthered whereby Zika could have been spread sexually
The condition, which has been linked to birth defects and is rapidly spreading through Brazil, has been linked to intercourse twice in medical literature.
It has led to calls for urgent research into the virus.
The first known case occurred when scientists found high levels of the virus in the semen of a 44-year-old man from French Polynesia.
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Workers fumigate the sambadrome to protect against the Zika virus ahead of carnival
What is the Zika virus? Everything you need to know about the outbreak
ZIKA virus could spread to Europe this summer, world health leaders have warned. But what is it and what threats does it pose?
GETTYIn its first assessment of the threat Zika poses to Europe, the WHO’s European office classified the overall risk as small to moderate.
In February the WHO declared a global health emergency over the Zika virus. The outbreak has now spread to more than 50 countries.
Here is everything you need to know about the disease, symptoms and ways to prevent its spread.
What is the Zika virus?
The virus - a once rare disease confined to the depths of subtropical Africa - was first identified in Uganda in 1947.It is an “arbovirus” - spread by mosquitoes and belongs to the same family as dengue fever and the chikungunya virus.
Because the virus has been so rare prior to 2015, there has been little research in to the virus, meaning it is difficult to clinically diagnose someone.
GETTY
The virus is transmitted by mosquitoes How is Zika virus spread?
The virus is spread by a certain type of mosquito that transmits the disease when it bites someone infected with Zika, and then goes on to bite another person.In some cases, Zika virus is transmitted through sex.
Where has Zika virus been reported?
Previous outbreaks were confined to small regions in Africa, South East Asia and the Pacific Islands.In May 2015 Zika virus was first reported in Brazil. The disease has since struck other parts of South America as well as Central America, the Caribbean and Pacific Islands.
What are the symptoms of Zika virus?
Only one in five of the infected is thought to develop symptoms including, mild fever, sore eyes, headache, joint pain and a red, bumpy rash.The illness is mild with symptoms lasting several days to a week. Those who have it are advised to rest, drink plenty of fluids and take medicines to reduce pain and fever.
Because four out of five don’t develop symptoms, virologists are concerned that it could be easily spread by people who don’t know they have the Zika virus.
Which birth defects can Zika virus cause?
The biggest concern - and why so many pregnant women are being urged to avoid pregnancy - is microcephaly.Microcephaly is a birth defect being associated to women who have been infected by the virus. It is caused by below normal brain development in utero.
Babies born with the birth defect have a below-average head size often caused by failure of brain to grow at a healthy and normal rate.
Children who survive face severe disabilities and possible seizures.
The rates of microcephaly in Brazil shot up by 1,792 per cent between 2013 and 2015.
How is Zika virus treated?
There is currently no vaccine for Zika virus.People should avoid getting bitten by using insect repellents, covering up with long-sleeved clothes and keep doors and windows closed.
Pregnant women should not travel to affected areas.
Male travellers should wear condoms to prevent the transmission of Zika virus through sex.
ZIKA SEX WARNING: Mosquito virus linked to baby brain damage may spread via intercourse
in Health
THE Zika virus, which is causing panic across the Americas, could be passed on through sex, findings suggest.
Two cases have been unearthered whereby Zika could have been spread sexually
The condition, which has been linked to birth defects and is rapidly spreading through Brazil, has been linked to intercourse twice in medical literature.
It has led to calls for urgent research into the virus.
The first known case occurred when scientists found high levels of the virus in the semen of a 44-year-old man from French Polynesia.
Workers fumigate the sambadrome to protect against the Zika virus ahead of carnival
While his blood and urine were clear, traces were found in his semen.
The second case happened in 2008 when Dr Brian D Foy, a disease expert at Colorado State University, came down with the virus after travelling to Senegal and collecting mosquitoes for a study. Both he and a colleague fell ill when he returned to the US.
In a strange twist, his wife also displayed Zika virus-like symptoms. Both Dr Foy, his wife and his colleague tested negative for malaria, dengue fever and yellow fever.
It was only after a fellow scientists recommended they get re-tested that they discovered it was in fact the Zika virus.
The WHO says more evidence needs to be proven before a link between sex and Zika can be made
Neither passed the disease to their kids or close family, so the couple believe it could have been sexually transmitted.
Health experts have said while the cases do not warrant a health warning, it should be investigated further.
The World Health Organisation says more evidence is needed to prove that sexual contact is a means of transmitting the virus.
The US Centers for Disease Control and Prevention say the cases are a “theoretical risk” but there is insufficient evidence to issue public health warnings.
The virus has been linked to a birth defect called microcephaly
Only 20 per cent of those infected show symptoms of the short-lived virus.
Typically symptoms include low-grade fever, joint pain, a rash, conjunctivitis, headache, muscle and eye pain.
The virus itself is not thought to be dangerous to most people but it has been linked to pregnant women and the birth defect microcephaly.
Countries in the affected regions are warning women to postpone pregnancy until more is known about the previously rare virus.
Zika outbreak: What you need to know
- 31 May 2016
- From the section Health
The World Health Organization has declared the Zika virus a global public health emergency.
The infection is suspected of leading to thousands of babies being born with underdeveloped brains.Some areas have declared a state of emergency, doctors have described it as "a pandemic in progress" and some are even advising women in affected countries to delay getting pregnant.
But there is much we do not know in this emerging infection.
What are the symptoms?
Deaths are rare and only one-in-five people infected is thought to develop symptoms.These include:
- mild fever
- conjunctivitis (red, sore eyes)
- headache
- joint pain
- a rash
There is no vaccine or drug treatment so patients are advised to rest and drink plenty of fluids.
But the biggest concern is the impact it could have on babies developing in the womb and the surge in microcephaly.
Zika virus: Special report
What is microcephaly?
The severity varies, but it can be deadly if the brain is so underdeveloped that it cannot regulate the functions vital to life.
Children that do survive face intellectual disability and development delays.
It can be caused by infections such as rubella, substance abuse during pregnancy or genetic abnormalities.
Case study: 'It's not the end of the world'
Brazil had fewer than 150 cases of microcephaly in the whole of 2014.
But more than 4,700 cases have been reported since 22 October 2015, with 404 confirmed and 3,670 still being investigated.
The link with Zika has not been confirmed, but the WHO says it is "strongly suspected".
Some babies who died had the virus in their brain and it has been detected in placenta and amniotic fluid too.
Why hasn't microcephaly been seen in other countries?
Cases of microcephaly have been centred in north-east Brazil, but the outbreak has affected more than 20 countries.So where are the other cases of microcephaly?
The outbreak started in Brazil before spreading elsewhere, and the World Health Organization says there will be a lag of several months to know if pregnant women in these newly affected countries are affected too.
There have been suggestions that Zika led to a rise in birth defects after the 2013 outbreak in French Polynesia.
The race to understand link to microcephaly
Is it safe to try for a baby?
The link to microcephaly is not certain, but some governments have advised women to delay getting pregnant until more is known.Experts now believe the virus is linked to a broader set of complications in pregnancy, including miscarriage, stillbirth, premature birth and eye problems.
The US Centres for Disease Control says Zika lingers in the blood for about a week and can be spread by sexual intercourse.
"The virus will not cause infections in a baby that is conceived after the virus is cleared from the blood," it says.
"There is currently no evidence that Zika-virus infection poses a risk of birth defects in future pregnancies."
The WHO advises couples practice safer sex or abstain for at least eight weeks if they are returning from Zika-affected areas. If the man in the couple planning a pregnancy develops Zika symptoms, then this period of abstinence or safe sex should be extended to six months.
Why is it a public health emergency?
The World Health Organization is worried that Zika is spreading far and fast, with devastating consequences.Declaring Zika as a "public health emergency of international concern" singles the disease out as a serious global threat. It puts it in the same category of importance as Ebola.
Unlike Ebola, where the focus was on boots on the ground, with Zika the attention will be on understanding the link with microcephaly.
The WHO will coordinate countries' health agencies to conduct trials to determine the risk.
It will also encourage efforts to stop the mosquito that spreads the disease as well as finding a treatment or a vaccine to stop the virus.
The work will depend on money donated by countries.
Where did Zika come from?
It was first identified in monkeys in Uganda in 1947.The first human case was detected in Nigeria in 1954 and there have been further outbreaks in Africa, South East Asia and the Pacific Islands.
But in May 2015 it was reported in Brazil and has spread rapidly.
It has since also been reported in: Barbados, Bolivia, Colombia, the Dominican Republic, Ecuador, El Salvador, French Guiana, Guatemala, Guadeloupe, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname and Venezuela.
"Its current explosive pandemic re-emergence is, therefore, truly remarkable,"the US National Institutes of Health said.
How does it spread?
They are found throughout the Americas except for Canada and Chile where it is too cold for them to survive.
If they drink the blood of an infected person they can then infect subsequent people they bite.
It is unclear for how long someone can transmit the virus after being infected.
And, unlike the mosquitoes that spread malaria, they are mostly active during the day, so bed nets offer limited protection.
The WHO expects Zika to spread throughout the Americas, but other scientists have warned that countries in Asia could face large outbreaks too.
Can it be spread through sex?
There have been reported cases of sexual transmission with the virus spreading to people who have not visited affected countries.This seems to be a very rare event, but it means Zika has a limited potential to spread in any country - not just those with the Aedes mosquito.
Some countries advise men returning home from affected countries to use condoms if their partner is pregnant or might become pregnant.
This should be done for 28 days after coming home if you have no symptoms, and for six months if Zika symptoms do develop.
Zika virus has also been found in other bodily fluids including saliva and urine, but it is unknown whether the virus can spread through these routes.
How long are people infectious?
The best evidence so far suggests that people can spread the virus via mosquitoes for a week after being infected.In semen it may persist for two weeks.
Countries have advised safe sex and a ban on blood donations for a month after just visiting such countries and for longer if they developed symptoms.
What can people do?
As there is no treatment, the only option is to reduce the risk of being bitten.Health officials advise people to:
- use insect repellents
- cover up with long-sleeved clothes
- keep windows and doors closed
The US Centers for Disease Control has advised pregnant women not to travel to affected areas.
What is being done?
He also said more money was being put into the development of a vaccine.
Some scientists are also trialling the use of genetically modified sterile mosquitoes that appear to reduce mosquito populations by 90%.
Meanwhile, efforts are under way to kill the mosquitoes with insecticide.
Zika vaccine
US experts from the National Institutes of Health say trials of a Zika vaccine will likely start in September this year. Depending on the results, larger trials could begin at the start of 2017."The very, very best scenario" would be a vaccine ready for the general public by the beginning of 2018, they say.
Are the Olympic Games under threat?
The Brazilian authorities will be targeting the mosquitoes' breeding grounds in the run-up to the Games.
The International Olympic Committee says it is in "close contact" with the Rio organisers and that Olympic venues will be inspected daily in the lead-up to and during this summer's Games.
It will be to ensure puddles of stagnant water, where mosquitoes breed, are removed to minimise the risk of athletes and visitors coming into contact with the insects.
There is also some hope there will be fewer mosquitoes in August as the month is both cooler and drier.