Lesson on TATAKalikasan, Ateneo de Manila University 87.9 FM Radyo Katipunan, every Thursday, 11 to 12 a.m., August 22, 2024
World Mosquito Day, August 20 2024
The Mosquito – World’s Deadliest Creature
Author's Note: Re-written and updated to address the extreme importance to be vigilant against the present outbreak of Dengue and other mosquito-related diseases that threaten many parts of the world.
Dengue mosquito (Aedes) after feeding. (Internet)
Dr Abe V Rotor*
Living with Nature School on Blog [avrotor.blogspot.com]
Co-Host with Fr JM Manzano SJ, and Prof Emoy Rodolfo, AdMU
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. It 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 pest 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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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. Realy? 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. ~
Fighting the World's Deadliest Animal
Feb 12, 2024 — CDC is the nation's leading science-based, data-driven, service organization that protects the public's health.
Background
Mosquitoes are common, flying insects that live in most parts of the world. Over 3,700 types of mosquitoes can be found worldwide. Some mosquitoes are vectors. A vector is an animal, insect, or tick that spreads germs to people or animals that can make them sick.
Preventing mosquito-borne diseases
West Nile virus disease (West Nile) is caused by a virus that is found in the United States and many other places in the world. West Nile is the leading cause of mosquito-borne disease in the continental United States. The virus belongs to a group of viruses called flaviviruses.
Dengue
Dengue is a common disease in many countries globally, including the Americas, Africa, the Middle East, Asia, and the Pacific Islands. Almost half of the world's population, about 4 billion people, live in areas with a risk of dengue. Dengue is often a leading cause of febrile illness in areas with risk.
Chikungunya
Chikungunya virus disease (chikungunya) cases and outbreaks have been identified in more than 100 countries in the Americas, Africa, Asia, Europe, and the Indian and Pacific Oceans. Find more information on countries with current outbreaks and on countries that have had evidence of chikungunya virus transmission among people within the last 5 years.
Zika
Zika virus disease (Zika) cases and outbreaks have been reported in areas of Africa, the Americas, southern Pacific, and western Pacific. Zika virus is most commonly spread to a person by the bite of an infected Aedes species mosquito. The virus can also be spread through sex from a person who is infected with Zika virus to their sexual partner(s). The virus can be passed from a pregnant person to their fetus. Infection during pregnancy can cause certain birth defects. Check for countries and territories at risk for Zika before making travel plans.
Lymphatic filariasis (LF)
Lymphatic filariasis (LF) is a parasitic disease transmitted through repeated mosquito bites over a period of months. Globally, the World Health Organization estimates that at least 51 million people in 44 countries are infected with LF.
Malaria
Malaria continues to be a leading cause of preventable illness and death in the world, resulting in nearly 249 million cases and 608,000 deaths across 85 countries in 2022. Nearly 3.2 billion people of the world's population is at risk of this preventable disease.
Since 2000, CDC and partners have saved nearly 12 million lives and prevented over 2 billion malaria infections. CDC co-implements the President's Malaria Initiative (PMI) with the U.S. Agency for International Development (USAID) in 24 African partner countries (with plans to expand to three more) and three programs in the Greater Mekong Subregion of Southeast Asia.
Threats continue to pose ongoing challenges to the elimination of malaria, including drug and insecticide resistance, invasive mosquito species, severe weather events, and limitations of rapid diagnostic tests.
Last year, for the first time in 20 years, the United States experienced cases of locally acquired mosquito-transmitted malaria. CDC experts supported early detection and a prompt response. With state and local partners in the lead, CDC acted as a technical co-pilot, strengthening public health capacity. Public health teams working together was essential in limiting further local spread beyond the 10 cases across four states (Florida, Texas, Maryland, and Arkansas), serving as an important reminder that a global problem can quickly become a local one.
Revolutionizing Malaria Detection: CDC’s New Assay
Creating innovative tools to detect malaria vectors is key to global malaria control and elimination.
Rapid diagnostic testing (RDTs)
Malaria rapid diagnostic tests, or RDTs, are useful test options when reliable microscopic diagnosis is not readily available. Malaria RDTs detect very small pieces from malaria parasites. A small sample of blood from the patient is collected and applied to the test card's sample pad. RDTs are less sensitive than other lab tests. A blood smear microscopy test must always confirm both positive and negative RDT results in a patient with suspected malaria. Despite these limitations, RDTs can provide results in less than 15 minutes.
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The invasive Anopheles stephensi (An. stephensi) mosquito poses a huge risk to global progress against malaria because it thrives in urban environments, is resistant to common insecticides, and can transmit malaria year-round. However, An. stephensi can be difficult to distinguish from other mosquitoes, making it tough for scientists to track its spread. Until now, there were no easily accessible molecular tools to rapidly detect invasions of An. stephensi. In 2023, in partnership with USAID, a CDC team of experts created an innovative, simple, and accessible assay to identify An. stephensi in the field.
The team worked tirelessly to get the assay right—rearing mosquitoes, conducting DNA extraction, analyzing PCRs and gels, and testing with different reagent concentrations at different times and temperatures. The result is known as the CLASS assay, and it can be used anywhere, without the need for a full molecular laboratory or highly trained molecular biologists. The CLASS assay will not only help with early detection and accurate identification of An. stephensi, but also help researchers understand the changing malaria landscape and how to best prepare and rapidly respond. (Internet). ~
The team worked tirelessly to get the assay right—rearing mosquitoes, conducting DNA extraction, analyzing PCRs and gels, and testing with different reagent concentrations at different times and temperatures. The result is known as the CLASS assay, and it can be used anywhere, without the need for a full molecular laboratory or highly trained molecular biologists. The CLASS assay will not only help with early detection and accurate identification of An. stephensi, but also help researchers understand the changing malaria landscape and how to best prepare and rapidly respond. (Internet). ~
Mosquito Repellant Plants
Mosquito plant (Citronella malvarosa); Citronella grass (Cymbopogon nardus)
Eucalyptus tree (Eucalyptus globulus) showing leaves and flowers
San Francisco plant or croton (Codiaum variegatum);
Philippine basil (Ocimum basilicum)
Peppermint (Mentha piperita); lavender (Lavandula angustifolia)
Citronella Malvarosa or Mosquito Plant Geranium is popular for its mosquito repelling properties. It has the fragrance of citrus on its ruffled, lacy leaves. They also produce flowers in the color of pink, purple or white. Not to be confused with Citronella grass as they are both different plants. Both plants however are effective mosquito repellants.
Many natural scents that are appealing to humans repel mosquitoes, including lavender, peppermint, basil, and eucalyptus. You might find you already choose these scents as perfume or cologne, in candles or sprays. (Internet photos)
Update on Malaria
World Health Organization (WHO)
https://www.who.int › Newsroom › Fact sheets › Detail
Dec 4, 2023 — According to the latest World malaria report, there were 249 million cases of malaria in 2022 compared to 244 million cases in 2021. Global Malaria Programme · World malaria report 2023
What is the current status of malaria in the Philippines?
The number of malaria cases has decreased over the years, from 19,102 cases in 2010 to 3150 in 2022 . Currently, only three provinces, Mindoro Occidental, Palawan, and Sultan Kudarat, report the disease. Over 95% of cases are in Palawan, where more than 60% are reported from Rizal municipality. Feb 8, 2024
Nearly every minute, a child under five dies of malaria. Many of these deaths are preventable and treatable. In 2022, there were 249 million malaria cases globally that led to 608,000 deaths in total. Jan 1, 2024 ~
https://www.who.int › Newsroom › Fact sheets › Detail
Dec 4, 2023 — According to the latest World malaria report, there were 249 million cases of malaria in 2022 compared to 244 million cases in 2021. Global Malaria Programme · World malaria report 2023
What is the current status of malaria in the Philippines?
The number of malaria cases has decreased over the years, from 19,102 cases in 2010 to 3150 in 2022 . Currently, only three provinces, Mindoro Occidental, Palawan, and Sultan Kudarat, report the disease. Over 95% of cases are in Palawan, where more than 60% are reported from Rizal municipality. Feb 8, 2024
Nearly every minute, a child under five dies of malaria. Many of these deaths are preventable and treatable. In 2022, there were 249 million malaria cases globally that led to 608,000 deaths in total. Jan 1, 2024 ~
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*Dr Rotor is an entomologist. He taught the subject and other biological subjects at UST, DLSU and SPU-QC until his retirement in 2010. He also served as director of the National Food Authority.
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