Mosquitoes for Science Projects in Schools Part 2

Having made suggestions for science projects involving mosquitoes in my blog of January 20, 2016, I  set up a simple experiment to find out whether Aedes aegypti mosquitoes will lay eggs in water with or without dead leaves in it, in the shade or in the sun. 4 jars were set up accordingly. A second purpose was to follow the life cycle of A. aegypti, photograph the different stages and find out how long it takes from egg to adult. The experiment produced rather unexpected results, so may require some modifications, which I have suggested in an edited version of the previous blog post. I should have learnt a lesson here: "Don't suggest an experiment without trying it first", but had I done so, I mightn't have written the blog!



Jars set up to be placed in sun or shade
with or without dead leaves.
Which do mosquitoes prefer?

  

The jars were set up on Feb 7, 2016. As of Feb 9, there were no eggs.



March 3, 2016. Still no eggs!

    March 3, 2016 - still no eggs, nor larvae. I have decided to abandon this experiment and comment on why it didn't proceed as planned.
1. The week following setting up the experiment, it rained every day and there was little sun. The jars put in the sun filled up and overflowed with rainwater. (I poured off some of it.)
2. I may have put too many leaves in the jars. As they rotted, they depleted the water of oxygen. Whether this would affect larvae, I don't know, as they do come to the surface of the water for air, but it would certainly make it more difficult to see them.
3. Leaves fell into the jars without dead leaves, so they were no longer accurate controls. Algae started to grow in the jar without dead leaves in the sun. This would also provide food for potential mosquito larvae.
4. The failure of this experiment doesn't mean there were no Aedes around. I observed larvae in other containers, such as a bowl I use to water orchids. I disposed of most of them, but kept a few in a jar with a lid so that I could confirm that the adults, when they hatched out, were indeed Aedes, and they were.
5. Another drawback to this experiment is that young larvae are so small they are hard to see.

Final stage larvae of Aedes,
barely 1 cm long.

            I had suggested this experiment for primary school children, but it might be more suitable as a project for students of biology doing CSEC or CAPE (Caribbean exams.) It would be useful for them to have access to a microscope or a binocular microscope so that they could observe young larvae.
             A more suitable activity for primary school children would be for them to hunt for existing mosquito breeding  sites and record the conditions under which the larvae of Aedes were found. A follow-up activity, ridding the environment of these breeding sites, needs to be an on going one.  My own observation is that Aedes are more prevalent after about a week of fine weather following a period of heavy rains.
      Another source of confusion in relation to mosquitoes is that there are so many similar species, identifiable more by their habits than appearance. Aedes breeds close to human habitation, not  in forests - the Cockpit Country is full of mosquitoes, none of them Aedes. Mosquito larvae found in bromeliads or Traveller's Palm are unlikely to be those of Aedes, and it is hard for the casual observer to distinguish between the larvae of different species of mosquito.
        However, the behavior of the adult Aedes is well known to us. We know they are hard to swat and quickly fly off, while another species sitting on your arm feeding will allow you to swat her. The reason is that the latter must fill her stomach from her first victim, while Aedes will fly off and feed off as many people as necessary to fill her stomach. However, if Aedes catches you sleeping, you could well be her only victim. If Aedes feeds on the blood of someone with Chikungunya, Dengue or Zika, the viruses will remain in the mosquito and can be passed on the eggs.  Within 8 - 10 days of hatching, the eggs will give rise to adults which will infect humans when they feed on them.
     Our best defense against these pests continues to be vigilance in removing the breeding sites of Aedes around our homes, schools, business places, churches and other meeting places. For other breeding sites, such as potholes in roads, we need to put relentless pressure on the authorities.

Mosquitoes for Science Projects in Schools

     

The chikungunya outbreak and now the threat of Zika in Jamaica, and the comments about mosquitoes by callers to talk-shows made me aware that much of the ignorance exposed could be addressed by students doing science projects on mosquitoes, with primary research in addition to research on the internet.

There are more than 3,000 species of mosquito world-wide and over 50 in Jamaica. The identification of species is highly technical and carried out by a limited number of persons. However, at the primary school level, children can observe and classify a few species.

Male Aedes with
feathery antennae

For example, all children would be familiar with the Aedes aegypti, which is active during the day, has white stripes on its legs, and breeds in small amounts of water. Other children will be familiar with species which breed in swamps and swarm at dusk, and are bigger than Aedes. The mosquito which transmits malaria, Anopheles, is longer and thinner and rests with its two hind legs in mid- air. Perhaps children are also able to detect a difference in the sounds made by these mosquitoes. It should be pointed out that, although there are some disease carrying species, mosquitoes serve useful purposes as pollinators, as food for bats (who are pollinators and aid in seed dispersal), as food for frogs, lizards and birds, and in their larval stages as food for fish and larval amphibians. Research on mosquitoes is carried out at the Windsor Research Centre in the Cockpit Country. http://www.jamaicaobserver.com/environment/Meet-the-mosquitoes_15093379

In the USA, much research is carried out on mosquitoes and suggestions for school projects are described on Clark University’s website.

 The following projects are suitable for biology students taking external exams at end of Grade 11 and higher. They require patience and persistence. It would be helpful is hand lenses and binocular microscopes were available.

A project could proceed as follows :

1.               choose an investigation

2.               conduct background research

3.               list materials needed

4.               list steps involved

5.               estimate the time involved

6.               set up the investigation

7.               collect and record data

8.               analyse data and draw conclusions

9.               present data to the class or school

Example  

Aedes  - male to left,
female in center

1.               To investigate the life cycle of Aedes aegypti.

2.               Background research: Reading.

           

3. Materials: jar containing water with a piece of dead leaf (about 1 cm sq. ) in it/

 

4.               Steps: Place the jar in places frequented by mosquitoes, and observe daily. When eggs are seen inside the jar, just above the water line, add water to cover the eggs. Take the jar to where they can be observed easily (out of the sun).

5.               Time: 7 to 10 days.

6.               Set up experiment.

7.               Record when the eggs hatch and when the larvae moult. When the larvae become pupae (comma-shaped), cover the jar, to prevent adult mosquitoes escaping. A hand lens would be useful to observe the eggs and the young larvae.

8.               Analyze findings: Did observations correspond with background research?

9.               Present findings to the class.

Suggestions for other projects:

1.     Do Aedes mosquitoes show preferences for

a)     Jars set up in the shade or in the sun?

b)     Jars with dead leaves in them or without dead leaves?

c)     Water with or without food coloring? (use different colors).

2.     What attracts Aedes mosquitoes to people? If students let out the mosquitoes from the above experiments in a fish tank with a tightly fitting mesh cover, they could try the following, being careful not to let out the mosquitoes

a)     Temperature – fill some balloons with warm and others with cold water.

b)     Color – use different colored balloons.

c)     Gases – carbon dioxide from fermentation using yeast; oxygen from hydrogen peroxide.

 

3.     Survey of persons who had chikungunya. Each child can conduct a survey in their community. Did everyone in the household catch it? Make a map showing where these persons are located. Do they believe that ChikV is transmitted by mosquitoes? Analyze arguments for and against this.

4. What is the effectiveness of different mosquito repellants? Design an experiment to find out.

             For primary school children, a more straightforward project would be to investigate where mosquitoes breed, by searching for mosquito larvae in discarded containers and old tyres. The larvae are most likely to be the final stage before they become pupae. These breeding sites should be destroyed after collecting some of the larvae.These can be put in a glass jar in order to observe when they become pupae and then adults. The jars should be  covered to prevent the adults from escaping. How they could be disposed of is a topic for discussion.

 

 

 

Chikungunya and Dengue Fever - A Public Health Responsibility

Zapped Aedes aegypti mosquitoes.
The small divisions on the scale are millimeters.

Nobody can tell me that I didn't have chikungunya, (chickV), although I'm not prepared to pay Ja$14,000.00 to confirm that diagnosis. Tests done on the a few hundred cases when the virus first appeared in Eastern Jamaica confirmed that is was indeed chikungunya. It spread quickly. It has got to the point now when we ask who hasn't had it, rather than who has had it. Nearly everybody on our street has had it.
     When it first arrived, it was made light of. "You'll have pains for about three days, maybe a rash, then you'll get better and will be immune to further attacks." Not so for many, including myself. Those of us over 45 may take 1 to 2 or more months to get over the acute phase. After that there is the possibility of the subacute phase with arthritis and the possibility of disorders of the blood vessels. Then there is the chronic phase, occurring beyond 3 months and persisting for 2 -3 years. The symptoms include prolonged and severe arthritis, fatigue, body weakness, and depression (no wonder, with the prospect of these symptoms for 3 years!) The chronic phase occurs in 13% of people who contract the disease. If 2 million people in Jamaica contract it, that means that about 260,000 will be affected for up to 3 years. More tragically, many people have died. Yes, they had other conditions such as sickle cell, hypertension and diabetes, or were undergoing cancer treatment, but without chickV they would still be alive.
     I think it is gross negligence on the part of WHO, PAHO and the Jamaican Ministry of Health, who were aware of this disease 2 years ago, to have done nothing. The least they could have done was to mount a public education campaign in the media, schools, churches and business places. The usual cry is that there is no money, but this outbreak has cost far more than a public education campaign would have. A public education campaign, at minimum could give the following information, which could be presented in simpler or more sophisticated ways depending on the audience.
1. Chikungunya is caused by a virus. What is a virus?
A virus is so small it cannot be seen with a regular (light) microscope, but only with an electron microscope. Viruses range in  size from 2 millionths to 30 millionths of a millimetre. What they lack in size, they make up for in numbers. We can have 100 trillion viruses in our bodies at the peak of infection.
2. How do viruses make us ill? 
Viruses consist of a protein coat surrounding a DNA (or RNA) core. The protein coat attaches to the outside of a cell in our bodies and the core is injected. It takes over the machinery of the cell and makes new viruses (about 10,000). Our cells burst open and lets them out to infect other cells. Each cell that is attacked dies. Different viruses attack different parts of the body.
3. What do our bodies do?
Our immune system manufactures antibodies to disable the virus. It takes about 5 days for the immune system to produce enough antibodies to get rid of all the viruses. After the viruses have been killed, some of the protein coats are still sticking to the outside of cells, so our immune system attacks these too, prolonging the symptoms.
4. How is the chikungunya virus spread?
It is spread by the female Aedes aegypti mosquito. (Males do not bite.) Aedes is a small mosquito which can be recognized by its stripey legs and body. It is around all day, and lurks under tables, beds and other pieces of furniture. It moves quickly, usually flying off before you can swat it.  There are over 50 species of mosquito in Jamaica, but Aedes is the only one that can transmit the chikungunya, and also dengue fever. When an Aedes bites a person infected with chickV, she sucks up some of the viruses in the person's blood. She will then digest the blood meal and find some water in which to lay her eggs. After about a week, she is ready for another blood meal. By that time, the viruses have moved from her stomach to her salivary glands. When she bites the next person, she injects some saliva to stop the blood from clotting while she sucks it up. The viruses are then let loose in that person's blood. It can take 2 - 7 days of incubation, during which time the viruses are multiplying, before the victim shows any symptoms. The mosquito can live for at least 3 weeks and bite many more persons. It could take only one infected person travelling from the site of the initial outbreak to another part of the country to take it there, without even being aware that they have the disease. Also, an infected person could be bitten by many mosquitoes. Alarmingly, an infected Aedes passes on the chikungunya virus to her eggs, which will give rise to mosquitoes already infected with the virus, without catching it from a person. Presumably, all subsequent generations will also carry the virus. Thus, the virus could remain dormant through the dry season, and re-emerge in the rainy season.

5. How can we stop it?
(i) Get rid of the mosquitoes, or stop them biting us -easier said than done. Adult mosquitoes can be killed by fogging, with malathion mixed with diesel oil,  which also kills other insects, including bees, and gives some people asthma. However, it is of limited usefulness, because the day after fogging, more mosquitoes hatch out. Using mosquito coils and vape - mosquitoes are becoming immune to these and they are not good for our health. Swatting them with a zapper - but you can't catch all of them.
(ii) Spray the skin with insect repellant containing Deet. I know people who have escaped ChickV this way, but surely it can't be good for you to spray yourself every day for months on end. It is good advice for tourists who are here for a few weeks.
(iii) Prevent Aedes from breeding. This should ultimately be the main form of control. In the limited public education we have had, people have been urged to check the following for mosquito larvae: flower vases, plant-pot holders, animal water containers, drums holding water for domestic use, old tyres, plastic bottles, styrofoam boxes and anything else that can catch water.

Careless garbage disposal leads to mosquito breeding.

Even if every householder followed these instructions, there are still too many places left where mosquitoes can lay their eggs - too many empty, overgrown lots in our towns and cities. There is one across the street from our house, and another one two houses away. Into these lots, people throw garbage which collects water in the rainy season. People living in the surrounding community are the target of mosquitoes which breed there, so it is really up to us to put pressure on the owners, or on Parish Council to get them cleaned up. Also, we need to be more responsible about garbage disposal. Business places shouldn't employ coke-heads to take away their garbage, knowing they will dump it on an empty lot or in a gully. We have an anti-litter law in Jamaica. Why is it not being enforced? Potholes in roads also fill with water in the rainy season, providing another suitable place for Aedes to lay their eggs.
"Too late now," we may say, as we've already caught ChickV, but there is the ever present threat of the 4 strains of dengue fever, including the life-threatening hemorrhagic dengue fever.
          A better long-term solution is to reduce the Aedes population significantly by releasing sterile males, which mate with females which then lay eggs which are not viable. Research into this by Oxitec has been going on for 10 years, and had now reached the testing stage. The method was successful in the Cayman Islands, just in time to spare them from chikungunya. They are now going on to test larger urban communities in Brazil. Their video is well worth watching.
     My final word is to those who work for WHO, PAHO, Ministries of Health in Caribbean countries, and governments who make the final decisions. We pay you. Without our taxes, you would not have the jobs you have. Jamaicans, already suffering under the IMF, now have to endure more pain as a result of chickV, when that pain could have been prevented. Is that fair?