Monthly Archives: January 2012

Mosquitoes – Cont.2

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Mosquitoes – How They Affect Humans(Cont.)

Control of the mosquito population

 It is important to control the mosquito population in and around your house.

It would be attractive to eradicate all 3,500 species of mosquitoes, wasn’t it to be unpractical and senseless, as there are some harmless nectar sucking mosquito species, and some are preying on the “bad” mosquitoes. Further a worldwide eradication is more the task of governments and larger organizations. Although my advice should be, don’t do it as you might disrupt the natural balance. The purpose of this writing is to propose measurements which can be taken to safely get rid of an over-population of mosquitoes, in and around the home.

Life Cycle of the mosquito

It is beneficial to know the live cycle of mosquitoes.

mosquito life cycle

Mosquitoes have four stages in their life, which lengths are normally very much influenced by weather conditions like wind, temperature, pollution etc.

1.  Egg stage

The eggs are laid in numbers of 50 to 300, stuck together at the sidemosquito egg raft of a container or on soil which is flooded from time to time or on raft type structure, all dependent on the specie of mosquito. The eggs can survive a prolonged period of months of drought.

2.  Larva stage

The larvae are hatched when the eggs are covered by water. During their growth, they shed their skin four times. The larva normally hangs from the surface of the water from a breathing tube, except for the anopheles, which stays parallel to the water surface to breath. This stage takes a week or two, depending of conditions. The larva feeds on micro organisms and organic matter. 

3. Pupa stage

The pupa rests, breathes, but does not feed, near the surface of the water and evidently observes its surroundings. When it feels threatened the pupa manages to sink to the bottom to hide, only to rise to the water level later.

4.  Adult stage

Ultimately the Adult splits lose from the pupa and will rest for a day or two as a nymph, before flying away as a full grown adult. The female is then ready to prick for blood and on average lives from three days to 100 days, hibernating if the temperature drops. Below the 15° Celsius (±59F) activity of mosquitoes slows down and practically stops below 10º Celsius (50F). But still micro climates within may spike some more activity, determined by humidity, spot temperatures and low movement of air and of course in the house and other dwellings. Better always be on the alert if these conditions exist. Some species more than others, but in general mosquitoes are quick to adapt. Maybe that is the reason they are around for hundreds of millions years, doing what they do best.

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Mosquitoes – Cont.1

Mosquito_Header (550 x 195)

Mosquitoes – How They Affect Humans(Cont.)

Diseases transmitted by mosquitoes

 During the prick the mosquito releases some of its saliva to avoid coagulation of the blood. This is how the transmission of disease causing agent takes place.

The females, vectors of various fatal diseases are from genera such as Anopheles spp, Aedes spp and Culix spp

 The diseases transmitted by the various vectors are:

1.    Malaria

Vector: Various of the 30 species of the genus Anopheles such as gambiae. In Europe the aim is to eradicate the disease in all over 50 countries by 2015, by eradicating the prevailing vector

Agent: Plasmodium, a protozoan micro organism: Most deadly specie is the Plasmodium falciparum;

Disease: Malaria, also called third day fever, derived from the life cycle of the parasite. There are slight differences in the life cycle, some cause the fourth day fever as they jump one full day.

2.    Dengue Fever

Vector: Aedes aegypti the principal vector, of secondary importance is de Aedes albopictus. All have white dotted lines along the body. This vector also transmit the Zika virus and the Chikungunya virus. Diseases new to the America since the year 2015 and 2013 respectively. Zika is named after the Zika forest in Africa, while Chikungunya comes from a word in the Makonde or Kimakonde language spoken by the Makonde, ethnic people from SE Tanzania and Northern Mozambique, meaning “bend over”.

This vector is closely associated with humans and their surroundings as they prey primarily on humans and breed in clean still water. This is often found in and around the house.

Agent: Dengue virus, which seems to have evolved around the beginning of the 19th century. There are four genotypes distinguished.

 Agent for Zika and Chikungunya are viruses with the same names respectively.

Disease: Dengue fever, also called fever of the joints. The hemorrhagic fever (DHF), is the most potent form, which often occurs when someone has antibodies of the virus from a previous infection. Risk factors for DHF are age below 12, female and Caucasians.
The Zika and Chikungunya diseases are in general mild fevers , with pain in the joints. Zika also may provoke a rash. and is serious in pregnant women, causing birth defect as microcephaly .

3.    Rift Valley Fever

Vector: Some five species of Aedes mosquitoes are vector, together with some other bloodsucking insects. The disease can also be transmitted through contact with droppings of these insects and contact with body parts of infected and dead animals.

Agent: In 1977, agent was recognized as of viral origin, caused by the genus Phlebovirus, one of the five genera in the family Bunyaviridae, .

Disease: This hemorrhagic fever infects humans and livestock alike. It was named “Rift Valley Fever”, after the Rift Valley in Kenya. The mortality rate in humans is around 1%. Severity in humans may vary from no or mild symptoms to serious liver necrosis. Normally patients recover within a week. A previous name is also veterinarian desease as this professional was very much at risk to contract the disease.

4.    Encephalitis

Vector: Aedes albopictus is the principal vector, While in Japan and various other East Asian countries the vector is Aedes japonicus. A sub-specie of the latter was found in the eastern states of the US near the end of the 20th century

Agent: The virus belongs to a group named Arbovirus, which has no taxonomic meaning but include three viral families of Togaviridae (main genus Alphavirus), Flaviviridae and Bunyaviridae. 

Disease: The agents cause various types of encephalitis such as that caused by West Nile Virus, St Luis encephalitis, La Crosse  encephalitis, Western Equine encephalitis, Eastern Equine encephalitis and Japanese encephalitis.

5.    Filaria

Vector: Dependent of locations around the entire world, various species of mainly Anopheles mosquitoes, but also species of Aedes and Culex mosquitoes are instrumental in the transmission of filarial agents.

Agent: Lymphatic filariasis is predominantly caused by the microscopic worm Wuchereria bancrofti, while in some Asian regions de agent also can be Bruchia malayi or Bruchia timori. 

De adult worm lives in the human lymphatic system. It can also affect domestic animals. The adult worms are mating in that habitat and produce millions of microscopic worms.

When the mosquito sucks the blood of an infected person the micro-filariae enter the body of that mosquito where it develops another stage. Later this mosquito can infect another person, the worms are quickly migrating to the lymph vessels.

Disease: The agents cause the disease called filaria and is spread from human to human via pricks of the mosquito.

As this disease may go on unnoticed for years, unless tested, it is often neglected, until malfunctions of the lymphatic system cause swellings of mostly the legs and sometimes other parts of the body. This may provoke bacterial infections in the lymphatic system and skin. In this stadium the disease is also called elephantiasis. The bacterial infections can be controlled by proper care.

A final note: for sake of completeness, need to mention that there also exist non filarial elephantiasis.

6.    Yellow fever

Vector: Two types of yellow fever are distinguished:

Jungle yellow fever, most spread by Aedes species amongst monkeys or humans, working in the jungle and

Urban yellow fever, spread amongst humans and transmitted by the mosquito Aedes aegypti. These mosquitoes have a natural adaptation to live amongst humans. They breed in all forms of cavitations and containers holding water for a week or two.

Agent: The yellow fever is caused by a yellow fever virus, of the genus Flavivirus. It is spread through most of Sub Saharan Africa and tropical South America. The infections take place in both locations if the mosquito is also present.

Disease: Monkeys (primates) are the main holders of the disease.

If all urban conditions are favorable the disease may take epidemic proportions. At risk are young men, who are not vaccinated, visiting the jungle for leisure activities.

In older humans immunity accumulates naturally. The mortality rate is ten times higher in Africa. BUT don’t take the chance and have a vaccination, before you go to invested areas. The health authorities in your country have the correct information.

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Mosquitoes – Cont.3

Mosquito_Header (550 x 195)

Mosquitoes – How They Affect Humans(Cont.)

Preventative measures

 As a preventative measure take the following steps inconsideration.

Inspect your home and yard for waterholes, containers which may hold water. The fact that there is no water in any of these containers, does not mean that you are safe. small

There may be eggs of mosquitoes in the container, waiting to get hatched, with any rain shower or flood, which fills up the container.

Check the drain system of gutters and pipes coming off your roof. 

Inspect water containers in and around the house. If the water cannot be removed, use approved low toxic larvacides.  Or consider adding some etheric oil, like citronella or from the peel of citrus fruit, to cover the entire surface of the water

 In ponds and fountains consider holding some fishes, There are mosquito eating fishes available in some specialty stores, Gambusia affinis

 Keep the yard clean from weed. Empty drinking containers of pets and birds daily. Inspect the yard and drains after a rain shower. Remember the adult mosquito lays eggs every third day. All favorable conditions in place there is a new generation of mosquitoes in some eight days and there are many adults covering the blank spots.

If all your preventive measures are in place, think about a plan to get rid of the survivors. Here you will need the help of your neighbors. Educate them, from what you know. Why involve the neighbors? Think about new influx from their yards to yours.

Make one or more simple mosquito traps. Sophisticated traps can be bought, but try some simple self made ones first. Mosquitoes love to creep in your ear and nose, because the body exhales the most carbon dioxide at these spots. A fact is, that mosquitoes are attracted by carbon dioxide and lactic acid. Use this principle to lure them into a deadly trap.

Mosquito_Trap (150 x 200)At the left you see how the upper part is inverted in the lower part of the bottle

Mosquito _Trap_ covered (150 x 200)

At the right the trap is finished, except for the liquid, and covered with black plastic

 

 

 

 

Step one. Select a cylindrical plastic soda bottle of some two liters or half a gallon.

Step two. Cut the upper part one inch under the tapered neck and invert this part into the bottom part, like a funnel.

Step three. Seal the junction, with wide plastic tape. Wrap black plastic from a bag around the bottom part to lower the light level in the container. Tape the plastic in place.

Step four. Now mix in a measure cup, some 300 ml of luke warm water with two heaped table spoons of brown sugar. When well mixed, pour the sugary water in the bottom part of the bottle, through the funnel, but avoid the sugary water to stick to the funnel wall, using sealed aluminum foil, folded as a funnel.

Moisten the inner wall of bottom container with sugar water and wait until it is completely cooled off.

Step five. Add two grams of household yeast, which, together with the sugar, will produce carbon dioxide.

Your trap is ready to invite the mosquitoes in. Make sure to put your trap in a darker and less trafficked corner of the house.

 Do not spray insecticides near the trap, as this may mask the odors and keep the mosquitoes from entering the trap.

Inspect the trap every two weeks and refresh the content if necessary.
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Mosquitoes – Introduction

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Mosquitoes – How They Affect Humans

Introduction

There are some 3,500 species known in the world, and they sure make their presence known if you approach their habitat. Mosquitoes affect humans in many ways.

Mosquitoes are insects from the group of Diptera, having two wings and the family of Culicidae, from Latin, which means gnat, or small fly. The popular name mosquitoes comes from the Spanish word “mosca”, which also in this case means small fly.

 In many species the females are the bloodsucking pests, which need the blood to nourish their eggs. During the bloodsucking activities many species transmit diseases and as such are the dangerous vectors.

Males do not prick. Yes, I said prick, because the word bite is biologically incorrect. The mosquitoes have piercing and sucking mouth parts. This leads to this correction.

The mandibles and maxillae, original mouth parts, are fused and forming the stylet, or piercing mouth part, while the labrum forms the tube, through which the mosquito sucks the blood. The labium covers all the mouthparts as a sheath.

NB: There are insects of close relation to mosquitoes called pricking midges or no-see-ums, belonging to the family of Ceratopogonidae. with some 4000 species, one quarter of them within one genus Culicoides. They are smaller than mosquitoes (1-3mm) and mainly a nuisance, although some are known to transmit an agent causing filaria. The females also prick for blood on mammals and humans for their proteins needed for the eggs They are distributed all over the world. They are sometimes wrongly called “sand flies”.

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