Puncture Of The Anopheles Mosquito Biology Essay


Rachel Carson published a book in 1962 called "Silent Spring" which book brought a lot of controversy worldwide. The book mostly were about the environmental impacts of the indiscriminate spraying of DDT in the US particular and in the world in general and questioned the logic of releasing such large amounts of chemicals into the environment without fully understanding of their effects on ecology or human health.

Worse, Carson even suggested that DDT and other pesticides may cause cancer and that their agricultural use was a big threat to wildlife, particularly birds and insects. A lot of environmentalist organizations stood up against its uses. At the Stockholm Convention DDT was subsequently banned for agricultural use worldwide, but its still in use in disease vector control to this day in certain parts of the world especially in Africa and still remains controversial.

Preliminary Outline of this topic:

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Talking about disease vector control, Malaria is the first cause of death in Mali. The inside residential spraying of DDT is known to be the best vectors control technical of malaria. With the WHO's guideline, the atmospheric pollution resulting from this concentration of DDT inside a sprayed room will depend on the characteristics of a sprayed room, the number of emission sources and climatic conditions.

The rate of DDT emission into the atmosphere depends on the number and the frequency of the openings. Assuming that a typical bedroom in Mali has two windows of average sizes of 0.5m X 0.5m wide opened 24 hours, the rate of DDT input in the atmosphere with typical wind of 5km/hour outside the sprayed room will be 60mg/day/room. (Study done by UNEP organic pollutants used as disease vector control). This rate could be cut by two if the windows were close half the day. With the same wind speed, the rate of DDT emission in the atmosphere will go down with decreasing size of the openings. As function of the number of emission source, then number of emission source depends on the number of room sprays and this last one will depend on the number of people sharing the same bedroom for a given population.

A typical scenario in Mali will be three people sharing the same bedroom, for a population of about twelve million people, the total number of sprayed room will be three million. With out typical rate of DDT emission of 60 mg/day/room, the total DDT input in the atmosphere will be 86.40 ton in Mali. This will vary depending on how many people are sharing the room. More details will me discuss in each on of these chapters.

The intent of this study will be to contribute to the improvement of the quality of environment and health of general public especially in the country such as Mali were 80% of the population lives in rural areas, and only 20 percent of the rural population had access to potable drinking water.

The table of Contents (Each one of these contents will be a chapter)

1-Historical background

2-Environmental Risk in Mali

3-Introduction to the study

5-Five leading causes of death in Mali from (1996 to 2005)

6-Lost of economic growth in 29 Malaria endemic African countries, 1980-1995 PPP: (Purchasing Power Parity)

7-Malaria cases in relation with the annual rainfall from 1995 to 2005 in Bamako (Mali).

8-Treatments of malaria

9-Vector control

10-Biological control

11-Seasonal trends in less than five years old (1-59 months) child mortality during the insecticide-treated bed net trial in Mali

12-Mortality rates in infants 1-11 months of age during the insecticide-treated bed net (ITN) trial in Bamako, Mali

13-The inside residential spraying of DDT

14-What is DDT?

15-Physical and chemical properties of DDT

16-DDT and the environment

17-DDT and Human health

18-DDT and Cancer

19-DDT and Human fertility

20-Excretion of DDT

21-DDT and Malaria

22-Incidences of Malaria before and after use of DDT

23-Malaria mortality rates (per100, 000 population/year since 1990)

24-Risks of atmospheric pollution with the "Inside Residential Spraying of DDT"

25-Determination of the concentration ( C) of DDT inside a sprayed room

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26-Atmospheric pollution as function of the number of sprayed room characteristics

27-Atmospheric pollution as function of climatic conditions

28-The incremental risk of cancer on humans due to the inside residential spraying of DDT

29-Risk of food contamination /Indoor food contamination

30-How to spray DDT

31-When to spray DDT

32-Hygienic rules advised for the inside residential spraying of DDT

33-Conclusion and Recommendations for further study

The Preliminaries

1. Choose a topic

2. Begin preliminary reading

3. Restrict the subject

4. Develop a preliminary thesis statement

Gathering Data

1. Compile the working bibliography

2. Prepare the bibliography on cards in correct form (3" x 5" cards)

I will consider the writing style used by James D. Lester in "Writing Research Papers: A Complete Guide, 2nd ed". (1971; rpt. Glenview, Illinois: Scott, Foresman, 1976).

These will be the step I'm willing to follow:

I-Begin extensive work in the library reference room I will make sure to check:

1. General bibliographies

2. Trade bibliographies

3. Indexes (books and collections, literature in periodicals, newspaper indexes, and pamphlet indexes)

4. Library electronic catalogue

II-Taking Notes

1. Develop a preliminary outline

2. Evaluate your source material; which is primary material and which is secondary material

3. Begin note-taking

4. Avoid plagiarism

III-Writing the Paper

1. Develop the final outline; test my outline

2. Prepare my writing write:

3. I will put my note cards in the order that my outline is in

4. I will consider my (real and imagined) readers and how their expectations may affect my tone and style

5- Write the rough draft

6- Check my documentation carefully

7- Revise and rewrite

8- Check the format of the text, citations, notes, and bibliography

9- Proofread

This is what I been working on since our last meeting in your office:

I - Environmental risk in Mali

I-1 Introduction:

Environmental problems in Mali are multiple and complex, insalubrities due to the mismanagement of the existing resources cause many parasitic diseases in the country. There is no waste water treatment in Mali; all waste water (domestic and industrial) are dumped into the rivers. An estimation of 745, 384 m³ of industrial waste water is produced annually in Bamako only, and dumped without any kind of treatment into the river Niger. In urban areas, domestic waste water is evacuated through wide opened gutters, those infrastructures are very poorly maintained and constitute a pullulating site of vectors carrier of diseases. In rural areas, there is no waste water evacuation system, and used water is dump in the court yard, the back yard or in the street, solid wastes are collected and stock in the back yard and will be use later as fertilizer for the crops. Human waste, once out of the latrines, remains piled up in the nearby area and will later be washed out by the runoff water or utilized as fertilizer. In urban areas, household refuses are collected by the communities organized as "G. I. E." using donkey tracked cars, those waste are dumped into local landfills located about a half mile around the city. Air pollution in Mali takes the form of carbon monoxide release in the air by the few industries and motor vehicles, there are no many cars in the country, but there is no standardized level of emission on the existing vehicles. The country is entirely dependent to firewood as energy source, this situation is major source of air pollution; and also contributes to the deforestation of the country already suffering from desertification.

The determination of the general tendencies of the causes of mortality in Mali is difficult, because the estimates are not always consistent. Hospital data show that the defective hygienic conditions and a bad quality of water play an important part as causes of diseases. More precisely, the worst risk is malaria and diarrhea diseases in children at very young age.

The following table illustrates the first five causes of mortality in Mali for the last ten years.

Table 1: The four leading causes of death in Mali from 1996 to 2005 Ministry of environment and the public health (National Program of the public health) Nov 2008

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From this data, malaria is by far the first cause of death in Mali. For the last ten years, the number of hospital visits due to malaria is by far higher than the four other combined diseases. Human health in Mali is seriously shaken by malaria and diarrhea as indicated in the preceding table; unfortunately, these two diseases are related to deteriorate environmental conditions.

Several types of bacteria consumed with food and contaminated water can cause diarrhea of which, the most common are: campylobacter, salmonella, and Escherichia coli. Others virus can also cause diarrhea like: Norwalk virus, cytomegalovirus, herpes simplex virus and viral hepatitis. Diarrhea can also be caused by food intolerance, some people are unable to digest food components like lactose or the sugar contained in milk.

The best control of diarrhea will be to disinfect the drinking water and incorporate a better hygienic habit which will considerably reduce the incidence of this disease.

More attention must be given to malaria because of its effects on human health in Mali. The high cost of medical treatment and the very significant number of malaria cases combined together take an important share of the health budget of Mali. A substantial reduction of malaria cases in Mali could release some resources to be invested elsewhere. Thus, malaria constitutes a true problem of health in Mali and all the attention must be given to this pandemic because of its impact on human health, the high rate of mortality due to it, the number of day missed at work because of the disease and the time devoted by the medical personnel to treat the patients of malaria. The best means of controlling malaria is to understand the environmental conditions favorable to the expansion of the vector carrying the virus and correct them, thus to cut the transmission of the virus from anopheles to humans.

Malaria is caused by the parasite protozoan of the kind plasmodium; four specimens of plasmodium can cause the disease in its various forms:

     • Plasmodium falciparum

     • Plasmodium vivax

      • Plasmodium Oval

    • Plasmodium malaria

P. falciparum is the most geographically distributed and the most dangerous of the four specimens. Not treated, malaria can lead to death by cerebral malaria; it is transmitted from individual to individual by the puncture of the anopheles, the female of the mosquito. There are

Approximately 380 specimens of the anopheles mosquito but only about 60 are able to transmit the virus of malaria. Like any other mosquito, the anopheles reproduces in water, each specimen having its preferences places of reproduction, its preferences nutriment and places of distraction. The plasmodium develops in the intestine of the mosquito and passes by the saliva of the insect to men each time it takes a sample of blood like meal. The parasite thus is transported in the liver of the victim by blood where it invades cells and multiplies. After 9 to 16 days, they return in the blood and penetrate in the red globules where they still multiply and destroy the red cells, which induce crises of fever and anemia of the patient. In the cases of cerebral malaria, the infection of the red globules caused the obstructions of blood vessels in the cranium; other vital organs of the body can be infected, which may lead to the dead of the patient

Tableau 2: Loss of economic growth in 29 malaria endemic African countries, 1980 - 1995. PPP: Purchasing Power Parity .Ministry of environment and the public health (National Program of the public health review) Nov 2007


Aggregate loss

(million of PPP - adjusted in 1987 $)

Per person loss

(PPP - adjusted in 1987 $)

As a fraction of actual

1995 income













Burkina Faso








C.A R.












Dem. Congo Rep.




Cote d'Ivoire
















Bissau Guinea












































Sierra Leone




South Africa
















Source: Based on results in John Luke Gallup and Jeffrey D. Sachs, `` the Economic Burden of Malaria'' in Economics of Malaria (2003)

In this list of 29 countries in table 4, the loss of economic growth as fraction of 1995 income due to malaria is much less serious in two countries: South Africa (1 %) and Botswana (5 %). This situation can be explained by the use of DDT in residential spraying against mosquitoes in South Africa, which they have sustained and maintained for years. In Botswana, there is no transmission of malaria in almost 2/3 of the country. However, in the remaining 1/3 (northern part of the country), the duration of the transmission is 2-5 months and is concentrated between December an April. So malaria is a less serious problem for the country in general. However, the economic growth loss per person in Botswana was one of the worst ($ 347) in 1987.

Malaria is closely tied to water because the vectors responsible for the disease use stagnant water as place of breeding. The most dangerous and the most abundant vector responsible for malaria in the Sahel (Anopheles gambiae) uses temporarily small and shallow stagnant water resulting from precipitations to breed. Because of its dependence of surface water as breeding places of the mosquitoes, malaria could not be transmitted under environmental conditions not allowing the formation of surface water.

Rainwater is largely responsible for the creation of the favorable conditions to the formation for surface water of the reproduction of the mosquitoes; and consequently is a key factor influencing the transmission of malaria. Temperature also plays an important role in the transmission by regularizing the favorable conditions to the rate of larval development of the mosquito and by influencing the survival of the adult mosquito. In general, the mosquito develops more quickly and has an early food intake at a greater frequency during its life cycle in hot areas. Moreover, the plasmodium, malaria parasite, multiplies more quickly in its host in hot temperatures. Also, moisture has a positive impact on the survival of the mosquito. It mosquito will not survive long enough to complete the transmission cycle of malaria where the relative humidity is constantly less than 60 percent. These three variables create the favorable conditions to the transmission of malaria each year in the pandemic zones. 

The following figure (figure 1) illustrates the relationship between the number of cases of malaria and the annual rainfall in Mali for the last ten years. There is a general tendency between the annual rainfall in Bamako and the number of cases of malaria in Mali even if it is vague. Also it is advisable to take into account the difficulty of data collection of the actual number of cases of malaria in the country.

Figure 1: Malaria cases in relation with the annual rainfall from 1995 to 2005 in Bamako (Mali). Ministry of environment and the public health (National Program of the public health) June 2008

It can also be noted on the figure that the number of malaria cases almost doubled from 1995 to 2004. That can be due to the difficulty of record keeping and data collection in the past, but also to the increase of rainfall and the tremendous population growth with a growth rate of 2.4 percent. This last one, not only increases the number of people exposed to the disease, but also contribute to increase the pressure on existing resources and therefore to deteriorate the environmental conditions. From the figure, one can also note a fall of the number of case of malaria from 2004 to 2005. These very encouraging results were obtained thanks to many grants from exterior institutes accorded to my country to fight malaria. The following actions were taken as treatment methods:

- The chemo prevention of pregnant women by the intermittent preventive treatment using the "sulfadoxine".

- The chemo treatment of any cases of malaria as follow:

* In the case of uncomplicated malaria:

· "Artesunate + Amodiaquine''.

· "Artemether + Lumefantrine''.

* In case of complicated malaria, injectable quinine was retained.

Any case of malaria among pregnant women must be regarded as complicated and must be treated using quinine.

- The use of the impregnated bed nets has been implemented in all levels of the health system during antenatal consultations in Mali. In spite of the progress made due to the use of these methods, malaria remains the first cause of mortality in Mali and more attention must be accorded to this pandemic.

II- The inside residential spraying of DDT

II-1 what is DDT?

DDT was developed for the first time in 1873 by Zeidler, a German student in chemistry; however, there was no known use for the compound. In 1939, Paul Müller of Geigy pharmaceutical in Switzerland discovered the utility of DDT as insecticide while working on a project to develop an alternative to the Naphthalene ball. Because of its use against the insects' carrier of diseases, he was awarded the Nobel Prize of medicine and physiology in 1948. The first large scale application of DDT was in Naples (Italy) during the Second World War where it was used to stop an epidemic of typhus. 

DDT, with an acute toxicity on the warm-blooded animals, a broad spectrum of effectiveness, a long residual effect, and a very low toxicity on the plants, seemed to be in this time, the ideal pesticide for households and the agricultural use. After the Second World War, the use of the DDT increased particularly for the control of mosquitoes, vectors of malaria and lice which transmit typhus. It was estimated by WHO (World Health Organization) that up to twenty-five million lives were saved by the use of DDT to fight those parasites. Unfortunately, DDT was so intensively applied that part of the target insects developed resistance to it.

In 1984, as much as 233 species of insects were resistant to DDT, concern about its persistence in the environment, the possible effects on human health and its bio-accumulation in the food chain, lead to the restrictions and the prohibition of the production and the use of DDT in many places in the world. The countries which restricted or prohibited DDT include: Australia in 1967, Switzerland and Cuba in 1970, the United States of America in 1972, Germany in 1974, Poland in 1976, the United Kingdom in 1984, South Korea in 1986 and Canada in 1989. Internationally, the DDT remains in service for medical goals and the control of mosquitoes. It is still commercially manufactured in China, India, Indonesia, and probably in Mexico.

II- 2 Physical and chemical properties of DDT:

DichloroDiphenylTrichloroethane, DDT is an organochlorinated insecticide.

It is very effective against many organisms, and it most spectacular success was in the fight against the mosquitoes, the anopheles which transmit malaria.

The chemical formula is C14H9Cl5.

Aspect: DDT is a waxy solid, although in its pure form it is composed of colorless crystals.

Its chemical name is: 1,1' - ( 2,2,2 trichloroethylene) bis [ 4 chlorobenzène ]

Or 1,1,1 - trichloro - 2,2 bis (4 - chlorophenyl) ethane.

. Gas number is: 50-29-3.

. Molecular weight: 354.51 g/mole.

. Solubility in water < 1 mg/liter at 20 degree centigrade.

. Melting point: 108.5 - 109 degree centigrade.

. Vapor pressure: 1.1x10ˉ⁷ torr at 20 degree centigrade 17.

DDT is strongly persistent in the environment, with a half life thought to be between 2 to 15 years in the ground; and it is motionless in the majority of soil. The routes of losses and degradation include: the flow by surface waters, volatilization, photo decomposition and biological breakdown (aerobic and anaerobic).

DDE (1, 1 - dichloro - 2 bis (p-chlorophenyl) ethylene) and DDD (1,1 - dichloro - 2 bis (p-chlorophenyl) ethane) are form in the soil by the biodegradation of DDT, both metabolites may undergo further transformation, but the extend and the rate depend on soil conditions and, microbial population present in the soil.

DDD was also used to kill pest, but to a far lesser extent than DDT. One form of DDD

(o, p' DDD) has been used medically to treat cancer of the adrenal gland. There is no known use of DDE, and it is found in the environment only as a result of contamination or breakdown of DDT. Biodegradation may occur under both aerobic and anaerobic conditions due to soil microorganisms including bacteria, fungi and algae. In laboratory experiments with marine sediments, DDT has been shown to degrade to DDE under aerobic condition. And, it degrade to DDD under anaerobic condition. Recent laboratory experiments in marine sediments show that DDE is dechlorinated to DDMU (1-chloro-2,2-bis [p - chlorophenyl] ethylene) under methanogenic or sulfidogenic conditions. The rate of DDE dechlorination to DDMU was found to be dependant on the presence of sulfate and temperature. DDD is also converted to DDMU but at a much lower rate.

Because of its extremely low hydro solubility, DDT will be maintained in the ground in soil and fractions of soil with greater organic maters. It can accumulate in the upper lower of soils in situations where heavy applications are or have been made annually. Usually, DDT is mostly absorbed by the organic matters of the soil, but it (with its metabolites) had been detected in many places in the ground and in ground waters where it can be available to organisms. This phenomenon is probably due to its high persistence in the ground; even if it is motionless or very slightly mobile, through very long periods it may leach in ground waters, particularly in soil with little organic matters. Residues of the product in the upper level of the soil are more easily broken down than those below several centimeters.

II-2 DDT and the environment:

The DDT is an organochlorinated insecticide which had founded a broad spectrum of application in agricultural and other sectors in the whole world by the 1939s. In 1972, the use of the DDT had been prohibited in the United States and in much of areas of the world, except the emergency use in public health sectors. DDT is still in use in some areas of the world to control the vectors carrier of diseases, such as malaria.

Once in the environment, the DDT will enter the ground, water, and the air. DDT and its metabolites are primarily motionless in the ground, and become strongly absorbed in the external layer of the soil. In the same way, as consequences of their solubility in water extremely low, DDT and its metabolites become absorbed by the particles in water and are deposited in sediments. Because of its chemical characteristics, DDT can be transported through very long distances in the atmosphere through a process known as "global distillation" where DDT emigrates from the hotter areas to the colder areas during a repeated cycle of volatilization from the ground and water followed by deposit on the ground by dry and wet processes of deposit. This long range transport of DDT has a consequence of a very broad dispersion of DDT and its metabolites everywhere throughout the world. The rate and the extent of the disappearance of DDT can result from processes of transportation as well as degradation and transformation. The persistence of DDT and its metabolites, in combination with their great affinity for lipids, contribute to the bio-accumulation (increasing concentration of a chemical in an organism which exceeds that in its environment) and the bio magnification (increasing concentration of a chemical in an organism according to its level in the food chain) of the DDT and its breakdown products.

DDT, DDE and DDD accumulate in fatty tissues of humans and animals, with concentrations in tissues increasing typically with level of the organism in the food chain. The prevailing route of exposure of the general public to DDT and its metabolites is through food.

Although DDT and its metabolites are omnipresent in the atmosphere, they are present at concentrations so low that the inhalation through respiration or by the skin is considered negligible. The decision of the EPA to prohibit the use of DDT in the United States was most influenced by scientific information documenting the harmful effects of DDT and its metabolites on the fauna and the flora. Those observed effects were severe, including the lethality of DDT on the birds and fishes; the induced effect of DDE on the reproductive system of birds, in particular the thinning of the eggs shell. The thinning of eggs shell among the birds' population was a subject of public concern in the 1960s and 1970s; because of observations on the ground of the abrupt declines of population of certain species including the bald eagle, the falcon peregrine, and the osprey. Scientific experiments established a link between the exposure to the DDT, DDE and DDD, in particular DDE, and the thinning of avian egg shell, which weighed significantly in the decision to ban most of the uses of DDT in the 1970s.

Here are some topics I will be working on it before August 13 as mentioned above at page #1

1-Treatments of malaria

2-Vector control

3-Biological control:

4-Impregnated bed nets

5-DDT and Human health

6-DDT and Cancer:

7-DDT and Human fertility

8-DDT and malaria:

9-Risks of atmospheric pollution with the "Inside Residential Spraying of DDT"

10-Determination of the concentration (C) of DDT inside a sprayed room:

11-Atmospheric pollution as function of climatic conditions

12- Etc