Common Infectious diseases

 

ABOUT COMMON INFECTIOUS DISEASES ……………

Infectious diseases are known as communicable diseases. These diseases are passed on from one person to another that is they are transmitted and are thus said to be infectious, contagious, communicable or transmissible. Diseases that are caused by bacteria, viruses and fungi are commonly referred to as infectious diseases. These are transmitted by way of droplets of liquid (small drops of liquid extruding from sneezing or coughing) in the air, food or water, by sexual intercourse or simply by touching.

Infectious diseases are those caused by other living organisms which invade the body and live parasitically. The following technical terms are of use when discussing infectious diseases.

Causative agent: The organism that causes the disease. 

Source of infection: How the infection occurs.

Incubation period: The period between the original infection and the appearance of signs and symptoms.

Infective period: the time during which a person is capable of passing the disease on to another person.

Carrier: A person who has been infected but develops no symptoms, the carrier can pass disease into another person.

Notifiable disease: A disease that must be reported by doctors to the health authorities due to its seriousness. (E.g. cholera, T.B., polio)

Epidemic: Situation in which a disease spreads rapidly through a large number of people and later disappears again.

Pandemic: an epidemic that spreads across the whole continent.

Endemic describes a disease that is always present at a low level in a given population.

Signs: Visible expression of the disease which can be found by examining a patient. E.g. a rash or a high temperature

Symptoms: An indication of a disease that is not detectable by examination and can only be reported by the patient. E.g. headache, nausea.

Prevention: Measures taken to prevent a person from getting a disease E.g. vaccination, sewage treatment, hygiene.

Treatment: Measures taken to cure a disease

In Sri Lanka, some infectious diseases cause epidemics from time to time. These epidemic diseases are cholera, typhoid, tuberculosis, diphtheria, measles, mumps, poliomyelitis, and hepatitis B. Some of the above diseases such as cholera, typhoid, diphtheria, tetanus and tuberculosis are caused by bacteria. Other diseases such as measles, mumps, poliomyelitis and hepatitis B are caused by a virus.

Cholera is one of the diseases which spread easily in a population and then disappear. Therefore it is an epidemic disease. Actually, it is one of the major five epidemic diseases in the world. The causative agent is Vibrio cholera which is a comma-shaped motile bacterium. The Source of infection is the water contaminated with the faeces of a sufferer or a carrier. A carrier is an individual infected with Vibrio cholera who does not develop typical symptoms of cholera.

It is estimated that only about one infected person in 50 develops the disease, the rest being carriers. Thus the faeces containing Vibrio are a considerable threat when the carriers are free moving in society.

The most common ways of transmission are drinking or washing food or utensils with contaminated water.  Direct contamination of food with faeces as a result of poor hygiene is possible. Once enter the intestine the bacteria multiply after 4 or 4 and 1/2 hours and release a powerful toxin. This will result in violent inflammation of the intestine and the production of watery diarrhoea. World Health Organization in Geneva should be informed to take international action to prevent the spreading of the disease. This can be done by restricting travel into or out of the affected area.

Signs and symptoms of the disease: No fever. The main sign is severe diarrhoea due to irritation of the bowel by toxins from the Vibrio. The liquid of the faeces is so profuse and cloudy that is called “rice-water”. Abdominal pain and vomiting also will be common symptoms among the patients. Skin is deathly cold and damp. Muscle cramps also may develop due to loss of minerals through diarrhoea.

Dehydration is rapid and quickly results in death unless rehydration treatment is given. The prime cause of death is the loss of minerals with its water.

Treatment: should be admitted to a hospital. Cheap and immediate therapy can be done by giving oral rehydration solutions like JEEVANI. Various antibiotics like Chloramphenicol and tetra cycling are effective at destroying the Vibrio.

Prevention and control:

 

• Provision of clean drinking water

 

• Proper sewage disposal methods

 

• High stand of personal hygiene

 

• Health education

 

• Control of flies which act as vectors in transferring the faecal matter to food.

 

• Isolation of patients and hygienic disposal of faeces and vomit from patients.

 

• Identification of carriers and prevention of their working in the food industry.

 

• Immediate examination of diarrhoea diseases for bacterial content.

 

• People in the area should be vaccinated.

 

Typhoid fever: An epidemic disease. The causative agent is a bacterium named

Salmonella typhi.

Source of infection: The bacteria are derived from the faeces of a sufferer from the disease or from a carrier. The disease is spread by water or from contaminated food. Typhoid spread needs only a small number of organisms. That means it has a high infectious rate. Water supplies may be contaminated by human faeces through seepage of sewage into a reservoir. Salmonella can live for about one week in sewage or longer in water that has been diluted with sewage. Food can be contaminated by a carrier or from dirty equipment which has been washed with contaminated water

Incubation period:  When the infecting organisms have been swallowed they migrate to the lymph glands, where they multiply during a 10 day incubation period. Then they enter the bloodstream. Now the patient develops signs like headache and muscular pain. A fever develops reaching its peak after about one week. A paint rash may appear. In the 2^nd week, diarrhoea develops and the patient may have mental confusion. If not treated at the end ulceration and rupturing of the intestine occur. The 3^rd week shows the peak of the illness and the patient deteriorates and may die.

Diagnosis: Blood samples will confirm, after culturing, the presence of antibodies against

Salmonella typhi

Treatment: Chloramphenicol and ampicillin are effective.

Prevention:

·         Patients should be isolated and hygienic disposal of faeces. Sewage disposal should be done properly.

·         Purification of water supplies should be done. Hygienic measures in the food trade and in the home.

·         Control of flies which can be transferred the faecal matter to food.

Diphtheria: An epidemic disease. The causative agent is a rod-shaped bacteria which is known as Corynebacterium diphtheriae and controlled by vaccination at the age of.

Method of infection: Droplet infection through the respiratory system. Bacteria grow on the moist mucous membrane of the upper part of the respiratory tract release toxins. The toxin is spread by blood to all parts of the body.

Symptoms and signs: Slight fever, sore throat, followed by severe damage to heart, nerve cells and adrenal glands.

Prevention:  Vaccination should be given to all children at the age of

Tuberculosis is also an infectious disease that can be seen from time to time in Sri Lanka. The causative agent of this disease is a fungal-like bacterium called Mycobacterium tuberculosis.  (Tubercle bacilli) .This is a rod-shaped bacterium and can be found in the air. Therefore tuberculosis is an airborne disease.

 

Source of infection: Transmission is by inhaling the bacteria into the lungs (droplet infection). It is much less infectious than the common cold and required prolonged contact between people to get the disease. Therefore this is associated with overcrowded living conditions, poor ventilation etc. It is a common disease and can be found in refugee camps, military camps and dormitories. Bacteria can resist drying out and can survive in the air and in the house dust for a longer period. Malnutrition and other infections resulting in a weakened immune system can reduce the resistance to the disease.

The outcome of infection by tubercle bacilli depends on a variety of factors.

 

·         Age of person

 

·         State of nutrition

 

·         Presence or absence of the immunity. (Immunity can be obtained by

 

      vaccination or previous mild infection)

 

Symptoms and signs: The disease starts as inflammation in one lung which develops into a cavity. Then further, cavities may develop, spreading into both lungs. As progressive destruction of the lung occur the symptoms become more dramatic with coughing, the appearance of blood in the sputum, chest pains, shortness of breath, fever, poor appetite and weight loss. The disease consumes the body causing it to waste away.

Treatment and prevention: To prevent the disease a vaccine had introduced by two French scientists named Albert Chalmette and Camille Guerin. So the vaccine has been named after them as BCG. (Bacilli Chalmette Guerin) This Vaccine should be given in the first week of birth. To treat the disease antibiotic Streptomycin can be used. The full course of treatment lasts 6-8 months and requires the consumption of several tablets a day, every day. This gives the combination of at least three or four antibiotics to reduce the chance of a strain multiplying that is resistant to one of the antibiotics. Some patients feel well after a few weeks of treatment so they stop getting treatments. After some time they will get the disease again. Therefore World   Health Organization launched Directly Observed Treatment under Supervision campaigns. With these programmes, the patient is given pills under supervision and watched each time to check the pills are swallowed. This is done over 6 to 8 months.

Measles: This is also a viral disease and Sinhalese think that this has the influence of God. So, they consider the patient as a holy person. They keep the place very clean where the patient is staying and the things he uses. They keep the patient separate from others. They spread Khomba leaves on the patient’s bed. (Actually, these khomba leaves have a germicidal effect.) As this disease is an air-borne disease and the virus enter through the respiratory tract it is rapidly spread from one person to the other. Therefore these habits are very important in controlling the disease.

Symptoms and signs: High fever 104- 105, reddened eyes, dry cough, sore throat, runny nose, watery eyes, cough. After2 or 3 days small white spots koplik’s spots appear inside the mouth on the wall of the cheek. On the 4^th day, the reddish rash will appear on the face then it is spread to the neck and chest. After 3 or 4 days these patches become brown and then the skin will peal out. Recovery will occur after one week. Sometimes viruses may damage kidneys and the brain.

Spreading of the disease: When a patient with the disease sneeze or coughs droplets that contain millions of viruses will be mixed with the air. Then this virus can enter the respiratory tract of another person. This type of infection is called “droplet infection

Prevention and treatment: Patients should be isolated from others. The people who nurse the patients should have to think much about their personal hygiene. They can use a mask to cover the respiratory tract and should keep their hands clean. No special treatment as the disease is a viral disease. Patients should be given more liquid food and if they are coughing medicine should be given. There is a vaccine to prevent the disease. Vaccination should be done at the age of 9 months. With one dose of vaccine one can get immunity for the whole lifetime. A child who did not get the vaccination may get the disease at any age.

Mumps: This is also an airborne viral disease and easily spread from one person to another. Entering the virus into the body occurs via the respiratory system. Parotid glands which are a type of salivary gland are affected by the virus.

Symptoms and signs:

Due to the viral activity parotid glands may be swollen up. Therefore patients feel difficulties in swallowing. Soreness of the throat, mild fever, loss of appetite, body pains may be occurring. Symptoms may last after 10 days. Sometimes viruses will affect the function of the organs brain, pancreas, thyroid, testes and kidneys. The inflammation of the testes after puberty may cause sterility

Prevention and treatment: MMR vaccination. This stands for three diseases are Measles Mumps and Rubella. Children should be vaccinated after 1 and ½ years of age.

Poliomyelitis: Causative agent is poliovirus. Infection is done by droplet infection or via human faeces.

Signs and symptoms: Fever, headache, and feeling of stiffness in the neck and other muscles. Nerve cells to muscles will

Destroy causing paralysis and muscle wasting. Most cases of paralysis occur in children aged 4-12 years but adults may also be affected by the disease.

Hepatitis A:

A causative agent is a virus. Water and food contaminated with the faeces of a patient will cause the disease 

Signs and symptoms: Loss of appetite, vomiting, mild fever. After 3 or 4 days eyes will become yellow colour. After 2 weeks liver may be enlarged. Sometimes liver may be damaged.

Infective period: For two weeks from the beginning of the disease.

Prevention: Personal hygiene should be improved. Food preparation should be done hygienically. Carriers should be avoided in food preparation.

                Now we can see that most of the above diseases can be prevented by following good hygienic habits. Waterborne diseases can be prevented by drinking boiled water. Water should be kept at the boiling point at least for 15 minutes. When breakout of diseases occur strict care have to be taken about the food you eat and drink. Eating from outside will increase the chance of spreading the disease because most of the outside food sellers do not follow hygienic methods in preparing food. Once, a cooking woman of a hotel who had suffered from typhoid fever earlier had caused to spread the disease for hundreds of people because she had acted as a carrier of the disease. Airborne diseases are rapidly spread because we can’t take any measures to keep out of the germs (causative agents). If a person who has such a disease should avoid mixing with other people even in their homes also they should be kept isolated. Especially, school children who are suffered from measles, mumps and chickenpox will help to spread the disease easily throughout a large area.                                                          

                                                

 

                          

Human impact on ecosystems

 

                                            HUMAN IMPACTS ON ECOSYSTEM

Now the world is in the computer age. Man has conquered every aspect of life by developing technology, medicine, and agriculture. Today man has reached the maximum height he can go by damaging the environment. Without thinking he is also a part of it man has done great damage to the environment for the sake of development. If he damages the environment he also has to suffer the effect of it.

The impacts of man on the ecosystem can be discussed under the following aspect

Commercialization of agriculture

·     Industrialization

·     Urban expansion

  War

  Exploiting of natural resources

 Pollution of soil, water, and atmosphere

Growing population

 When we think about the commercialization of agriculture every country has to give some percentage of their forests to clear out. When we think about our country the forest coverage is 44% in 1956 but in 1992 it has declined up to 22%. This clearing of forests had done after introducing large-scale projects like Mahaveli. To supply the needs of the grown population of a country like food, fuel, timber, shelter, and other resources many forest, woodland, and scrub were cleared.

Due to this deforestation, many serious problems have arisen. Loss of traditionally harvested products such as timber, fuelwood, honey, fruit, and herbs. Forests catch a large amount of rain. An intact forest canopy softens the impact of heavy tropical rainfall in many ways. It releases a large amount of water back into the atmosphere in evaporation and transpiration and channels water gently through the vegetation to the soil. If the forest canopy is removed tropical soil surface bakes hard in the intense heat. Rainfall cannot easily penetrate and is rapidly lost from the area in surface run-off. And at the same time, flood hazard is created in the plains below. Furthermore rapid run-off of rainwater results in soil erosion. This can remove topsoil and make ground unsuitable for growing crops. It can also lead to silting of reservoirs which reduces their usage time; dams must be continuously dredged to keep them open. In Sri Lanka, to cultivate cash crop cardamom, 2400 hectares were cleared in the Knuckles range. Being hilly areas with a steep slope and also having high rainfall these places are especially susceptible to soil erosion.

The effects of deforestation are very hazardous. Some of them are as follows.

1.  Deforestation increases global carbon dioxide concentration which may have long    term effects on the global climate

2.  Forests have diverse wildlife communities. Their destruction will lead to innumerable extinction of little known forms of life

3. Competition between native and invasive species may occur.

Areas in the Ratnapura district were mined for precious stones. The rainwater collected in these pits makes good breeding places for mosquitoes.

                              When we consider industrialization, we can see that it alters the gaseous content of the atmosphere, and adds harmful things like soot, heat to the air, chemicals to the soil and water. Therefore, industrialization causes pollution of the environment in every way. Now let me define what pollution is?

Pollution: Is the release into the environment of substances or energy in such quantities and for such duration that they cause harm to people or other organisms or their environment.

Pollution can affect all the aspects of the environment that is natural (living and non-living) or man m, made environment.

• Pollution of the atmosphere
• Pollution of water
• Pollution of soil
• Pollution of the atmosphere: The earth’s atmosphere is a mixture of gasses. The lowermost layer of the atmosphere, 10km thick, is the layer that gas exchange occurs between the atmosphere and the living organisms. Above this layer, there is the stratosphere layer which contains the ozone layer. This layer absorbs UV and IR from the sun. Therefore organisms protect from harmful radiations by the Ozone layer. Chlorofluorocarbon (CFC) is one of the harmful gases that destroy the ozone canopy. There are many naturally found gases in the atmosphere and they are incorrect proportions. Industrialization alters this proportion of natural constituents. When we consider the gas carbon dioxide its natural percentage is 0.03% in the atmosphere. But many human activities such as the burning of fuel (coal, oil, and gas) farming of animals will change this proportion by adding carbon dioxide. The earth reflects some of the heat it gained from the sun and cools the atmosphere. When the air has more carbon dioxide than the normal percentage in the atmosphere the reflection of heat will not occur properly because carbon dioxide absorbs some of the heat. So, the part of the heat is not reflected in the space. Due to this heat, global warming may happen and ice caps of the poles will melt out, and rising up of sea levels will occur. One of the consequences of this would be the flooding of large areas of the lowlands where many modern cities are built. For example city of Bangkok.

The other air pollutant gases such as oxides of nitrogen and sulfur dioxide may cause great harm. Bronchitis, pneumonia, and heart failure may cause by inhaling sulfur dioxide with soot and ash. These gas pollutants are released into the atmosphere when fossil fuels are burnt. When raining, sulfur dioxide in the air will dissolve in the water and be converted to sulfate ions. Then “acid rain” occurs and it changes the pH value of the inland water masses like rivers and ponds. This will lead to the death of living things in it. Sulfates can be absorbed by plant roots and plants may be affected by them. On the other hand, small apertures of the plant leaves (stomata) can absorb sulfur dioxide in the air. In Sri Lanka, forests are dying back in Horton plains due to acid rains. Lichens that are sensitive to aerial pollutants can be considered as bio-indicators of aerial pollution.

As a country, we can try to minimize air pollution but we can’t escape from it because air pollutants can be transported in the air to a long-distance through wind currents. So, pollutants can be found in places that are far away from the place where emissions of the pollutant occur. At present, heavy metal lead is considered to be the most serious pollutant in the atmosphere. There is lead in the air we breathe, in the water we drink, and in the food we eat.

Lead in the air: Combustion of petrol in motor vehicles accounts for 80% lead in the air. People who work close to motor vehicles have a higher concentration of lead in their blood. To avoid this now lead-free petrol has been introduced.

Lead in water: Lead in the air is washed by falling rain. Aquatic plant roots absorb lead from their roots. Aquatic animals who are feeding on plants get lead into their bodies. People who feed on these will ingest lead.

Lead in humans: Whether inhaled or ingested lead is absorbed into the bloodstream and accumulates in the liver. When canning food they use lead to seal the containers. This may be added to the food

Water pollution: In Sri Lanka, there is recent evidence for water pollution. The main causes for water pollution are:

• Sewage disposal into the water masses
• Industrial activities
• Commercial agriculture

Sewage is the biggest pollutant of freshwater masses like lakes, ponds, and estuaries. This led to an immediate drop in the amount of oxygen dissolved in the water mass. Organic matter in the sewage will stimulate the microbial population in the water mass, especially bacteria. As they respire they use up oxygen. Further, they use oxygen to the breakdown of organic matter. If the water masses are not flowing (stagnate) this will affect adversely. In polluted lakes, mineral content is higher than that of polluted lakes. Therefore, the polluted water is enriched with minerals and now it is eutrophic and the growth of the phytoplankton is stimulated. Blooms of algae, especially blue-greens quickly appear. Some of the released toxins will kill fish. After some time anaerobic bacteria release gases ammonia, methane, and hydrogen sulfide giving a bad smell and making the water unfit for most forms of aquatic life. Sometimes nitrogen and phosphorus run-offs from fertilizers used in agriculture also will increase the mineral content hence the algal blooms.

Industrial activities may cause chemical pollution and thermal pollution. Major industries in Sri Lanka are

 Milk and food processing

Textile and rubber

Paper and pulp

Tanneries

Formulation of fertilizers and pesticide

Formulation of fertilizers and pesticides

                                      When hot industrial wastes are released into the water masses it will increase the temperature of the water and living creatures could not tolerate that increased temperature. Some heavy metals such as mercury, copper, lead, and zinc may be added to the water masses as by-products of the above industries. These chemicals will give hazardous effects on the living creatures of those water masses as well as on human health.

Commercial agriculture depends on agrochemicals. Agro-chemicals are not naturally found substances and they add to our soil and water bodies then gradually into our bodies causing many unidentifiable diseases. Further, chemical fertilizers, not like organic manure, decrease the quality of the soil such as its texture, microbial content, etc. When we consider agrochemicals pesticides perform a major role in killing pests as well as other natural species which are very important in biological control. Pesticides include insecticides, fungicides, and herbicides. Pesticides have some characteristics that harm the living organisms in the environment. They are as follows,

• Toxicity
• Persistence
• Specificity.

  Toxicity tells about a dose that kills half of an experimental laboratory population of the pest. So, it is very important to apply the correct dosage.

 Persistence is the length of time that pesticide remains in the environment including within the organisms without being broken down.

Specificity: This indicates the most susceptible pests to the pesticide. In our country, most of the farmers are not aware of these things and they use pesticides as they like. The only thing they need is the eradication of the pest population as soon as possible. On the other hand, they should know about the life cycles of the pest. It is much needed to choose the right time to apply the pesticide. Further, they do not take preventive measures to avoid inhaling, ingesting or contacting with pesticides. The farmers when they are spraying pesticides do not wear masks and sometimes do not even cover their bodies. They spray the pesticides on hot and windy days. Wind causes to bring the pesticide all over their bodies. Sweating causes to bring the pesticide in through pores of the skin.

   After spraying the pesticides to the paddy fields they used to wash the spraying tanks in nearby water streams. This causes great harm to the aquatic life of the paddy fields as well as the streams. For example, in those days there were many fish, tadpoles, crabs, snails, and insects like pond skaters, water scorpion unicellular animals like an amoeba, and paramecium as for animals. (That is almost all the animal phyla has represented) Mosses and algae, like Spirogyra, aquatic ferns like Azolla, aquatic flowering plants like aponegetum, pistia also were there in the water streams and in the paddy fields in our village. But alas! Today we can’t see any creature. The same thing has happened to the plant life also that is mosses and algae in the streams and “Gotu kola” and “mukunuvenna” in the fields all are disappeared due to these agrochemicals. 

Effect of pesticides:  1. Directly the species can be affected by eating food with pesticides. 2. When they ate primary or secondary consumers they will be affected secondarily.

This is caused the extinction of some species hence the diversity of species. Among these extinction species, there may be predators of the pests. It prevents the biological control of pests. When we consider decomposers like bacteria and fungi they also may be affected and this reduces the soil fertility. On the other hand nutritious food species also extinct and it is affected the nutrition of village people.

 To avoid the hazardous effect of pesticides can use two main alternatives.                                                              

  1. Biological control: Biological control can be done by introducing natural enemies such as predators, pathogens, and parasites. Sometimes predators of a pest may harm the other important non-pest species. For example, the mongoose which was introduced to Jamaica to control black rats severely reduced some bird populations and caused the extinction of several reptiles.                                                             

2. Integrated control: This method combines and sensitively integrates biological and chemical control. In this method, all the pest controlling methods can be used such as Cultural methods which include crop rotation, mixed cropping, removal of crop residues, using naturally found pesticides such as the juice of Khomba seeds. This will not eradicate the entire pest population but it will keep the pest population below the level of economic in agriculture.

 

sustainable development

                             SUSTAINABLE DEVELOPMENT OF THE

                                          ENVIRONMENT                              

                                           To live and to develop we need to use resources in the environment. When we consider natural resources they are not growing parallel with the needs of the increasing population. Therefore we can’t use natural resources excessively because some resources are cannot be renewable. Before we continue further we should understand many phenomena which come under natural resources. First, let me define what natural resources are.

                     “The things we use in our day to day life and to develop our economies are known as natural resources”. The main three natural resources are air, land, and water. But solar energy, animals, plants, and minerals also can be considered as natural resources. Natural resources can be categorized into two, 1. Living resources           2. Non-living resources.

Living resources contain the organisms found in forests, grasslands, deserts, wetlands, and aquatic systems, (marine and freshwater)

Under non-living resources; air, land, minerals, and solar energy can be considered.

Living resources can be categorized into two groups renewable resources and non-renewable resources.

Renewable resources: If the rate of consumption is less than the rate of renewable we can call it renewable resources.

Nonrenewable resources: When the rate of consumption of a resource is more than the rate of renewable it will become a nonrenewable resource.

 Some living resources are renewable in nature under natural conditions. Edible living organisms like fish can be taken as an example to explain this phenomenon. If overfishing is done some fish species may be extinct. Then it will become a nonrenewable resource. How does overfishing cause the extinction of a fish species? When they overfish they catch the entire fish population including young small fish (fingerlings). Therefore renewal ability depends on the consumption rate. Because of the greediness of man some food species plants as well as animals may be extinct from the world. Excessive cutting of trees also may cause the extinction of plant species. Once destroyed forests could not be easily recovered again. Some biologists consider a forest as one organism and they expect to protect the forest as an individual. So, fish, forests, and other animals can be considered critical resources.

Non-living resources can be categorized into 3 groups,

1. Resources that have a continuous supply.

        Solar energy, Tidal waves

2. Resources that can be renewable

Water by the hydrological cycle

Clean air by photosynthesis of green plants

             These 1st and 2nd resources are noncritical

3. Resources that cannot be renewable (non-renewable resources)

              These are the resources that take millions of years to generate. They have some amount in the earth and when man consumes them it will decrease in quantity. E.g. Fossil fuels, coal, hydrocarbons, minerals, metallic (copper, iron, silver, gold), and nonmetallic (gemstones)

 After studying the problem of non-renewable resources in 1987 a new concept has introduced as Sustainable development of the environment. This has been defined as “meeting the needs of the present without compromising the ability of future generations to meet their needs”.

“The earth summit” held at Rio de Janeiro in 1992 had put forward a convention and was signed by 175 countries including Sri Lanka. There are three main objectives of the convention and the most important objective is “the sustainable use of the environment”. When we consider sustainable development we should not act as “preservationists” but should act as “conservationists”. Preservationists never get any use from the environment. That is they never try to get resources from the environment and they think of that environment as a sacred thing. But conservationists use natural resources more carefully and sensibly. They use the resources to a certain extent but do not overuse them. So, for the people who seek economical development as well as environmental development they have to be conservationists. In the recent past when we had the Tsunami disaster great damage was done to the regions along with the coastal line areas where people have over mined the coral reefs. When we think about forest ecosystems they are like living beings. We can’t keep them without touching them because as a country with not much economic development we want to obtain many things from forests such as timber, fuel, medicine, food, fodder, animals, etc. But we have to use these sensibly and sustainably that is we should not bargain with the future generations' needs.

For the sustainable development of the forests, a government should introduce effective management of forests programs all over the country. Under these programs can introduce the following things.

1. Prevention of overexploitation of plants for timber, medicine, fuel.
2. Prevention of overuse of animals for flesh, skin, teeth, and for raring.
3. Prevention of introduction of new invasive species
4. Control of deforestation
5. Monitoring of depletion of natural resources.
6.  Re forestation programmes
7. Prevention of dumping of garbage.
8. Prevention of extracting plant species and throwing garbage on visitation.
9. Conserve the lands which were cleared and used for agricultural purposes and now abandoned.
10.  Ex-situ conservation should be done. That is the conservation of some rare plant and animal species outside their natural habitats. For example, keeping animals in zoos,
11.  Increase the efficiency of resource use.
12.  Promote sustainable consumption
13.  Establishment and management of protected areas and buffer zones. Now it is about 14% of the land area.
14. Further, can conduct education and awareness programs

What is the importance of sustainable development?

• Creating human and other animals' security
• Conservation of natural resources endowments
• Securing the natural resources as conservationists

Make use of the natural ecosystems without damaging

DISEASES SPREAD THROUGH MOSQUITOES AND HOW TO PREVENT FROM THEM

                                          DISEASES SPREAD THROUGH 

                      MOSQUITOES AND HOW TO PREVENT 

                                            FROM THEM

There are 4 major epidemic diseases in Sri Lanka, which are transmitted by mosquitoes. Some general information about these diseases is shown in the table.

Name of the disease	Causative agents (Parasitic pathogen )	The place where they live in man (primary host)	Mosquito species that spread the disease (only by females) (Vector or intermediate host)
1. Malaria   2. Brain malaria	1. Plasmodium vivax 2. P. falciparum (protozoan)	1. Blood   2. Blood vessels in the brain	Anopheles culicifacis
Filariasis (Elephantiasis)	Wucheraria bancrofti (A nematode worm)	In lymph nodes	Culex quncifaciatus
Dengue	A virus	Blood	Aedes aegyptii,  Albofictus aegyptii
Japanes Encephalitis	A virus	Cerebral fluid and spinal fluid	Culex tritinioryncus    Culex gellidus

 

These diseases are most common in Africa and the South Asian region because mosquitoes flourish well in these regions due to the favorable climates.

Malaria has been one of the world’s worst killer diseases throughout recorded human history. In Sri Lanka also a large number of people had been killed by malaria in the decade 1940-1950. To identify the persons who are suffering from malaria their blood smears (thin films of stained blood on glass slides) should be observed under a microscope by Medical Laboratory Technicians. They can differentiate the causative pathogen species as P. vivax or P .falciparum. 

 When a mosquito with pathogens in its salivary glands sucks blood from a person, parasitic pathogens enter the bloodstream of that person. This type of transmission is called an active transmission and it assures the transmission of vectors by a hundred percent. Then these pathogens enter the liver cells and there increase in number by multiplication. After rupturing of the liver cells some may enter again into new liver cells. Then they multiply there and increase their number in hundreds. Then rupturing of those liver cells occurs and parasites enter the bloodstream and then into the red blood cells. In each red blood cell, parasites undergo further division and as a result, the red blood cells break. Because of this rupture, the toxic substances of the parasites are released into the bloodstream and the person develops fever due to these toxic substances. After the infection, it takes ten days to develop a fever. And body temperature increases rapidly up to 40.6˚ C-41.7˚ C. The fever may last as long as 12 hrs was accompanied by headache, generalized aches, and nausea. When the fever lasts sweating starts and then the temperature falls. The fever and other symptoms coincide with the multiplication of the parasite. 

Plasmodium falciparum causes malignant malaria (This is out of control and likely to cause death) in which the fever is accompanied by other complications. The parasites tend to accumulate in blood vessels of the brain, causing convulsion and coma. Other common complications include kidney failure and pneumonia. Therefore, malaria caused by Plasmodium falciparum can be fatal within 2 or 3 days.

Prevention and treatment: There are drugs to prevent disease and can be used by people who enter areas endemic for malaria. Plasmodium falciparum is now resistant in most areas where malaria is endemic such as Sri Lanka and Thailand.

 How to identify the mosquito Anopheles culicifacis?

This is a medium-size mosquito that sucks blood from the man when only they are inside houses. When these mosquitoes are at rest on a wall or such a place they make an angel of 45˚ with the surface. They suck blood from 6.00pm to 10.00pm or otherwise, 4.00am to 6.00am.

                                Filariasis (Elephantiasis)

                        The causative agent is microfilaria larvae which is one of the stages of the life cycles of nematode parasitic worm called Wuchereria bancrofti. The permanent host of this parasite is a man and the intermediate host is a female mosquito called Culex quncifaciatus. The disease spread through an intermediate host which is an active vector. So to control the disease the vector should be controlled.

 What is the life cycle of Wuchereria bancrofti?

The mature male and female parasitic worms live in the lymph nodes of the lymphatic system of man. They give rise to larvae called microfilaria. They produce a large number of microfilaria larvae at a time. These larvae go to the lungs and concentrate there. Then they go to the peripheral blood system (blood vessels in the skin) of man during the period of time 10.00 pm and 4.00a.m.The mosquitoes of this species are nocturnal and feed on human blood only at these hours. When the mosquitoes suck blood these microfilariae enter their stomachs. Inside it, they complete their life cycles and come through the thoracic muscles, and land on the mouthparts of the mosquito. When a mosquito with these parasites sucks blood from man, parasites can enter into the bloodstream. They enter in pairs and then to the lymph vessels and to the lymph nodes where they become sexually mature. Then again they give rise to micro filarial larvae and complete their life cycles.

Effects of the parasite: Adult worms that are in lymph vessels obstruct lymph vessels.  Due to the obstruction of lymph vessels, lymphatic fluid may come out through the walls of the ducts and collect in large amounts in some organs like kidneys, scrotum, and in the bladder. Therefore these organs become enlarged.

Signs and symptoms ׃ muscle pains, red patches, swollen lymph nodes. Enlargement of limb joints, breasts, and scrotum, Mild fever develops and loss of appetite may occur.

Identification of diseases׃ Sometimes the people who are not showing the symptoms may have microfilaria in their blood. These can be identified by observing their blood smears. Blood should be taken for testing during the period when microfilaria can be seen in the peripheral blood vessels. Therefore, the government has organized special clinics within the hrs 8.30pm-10.30pm.

Sometimes PHI visits homes during that time and obtains blood smears.

Some other 2 tests also can be done.

1. Fluorescent antibody test (FAT).

This test is done to find whether there are antibodies against the filarial worms in the blood or not.

2. Eosinophil – Increasing the Eosinophil count also indicates the disease Filariasis.

Treatments: can give drugs. Diethyl carbamazine (Hetrazan)

To eradicate Filariasis from Sri –Lanka, the government has introduced–a one-day treatment

method- In this method, the people who lived in the Following eight districts, Colombo, Gampaha, Kalutara, Gall, Matara, Hambantota, Kurunagala, Puttlam are treated with 2 tablets in the same day. The two tablets are Hetrazan and albendazole.

                                              Dengue fever

 This is a disease that spreads rapidly in tropical countries. The causative agent is a virus. Yearly 50-100 Million people suffer from this disease and about 500,000 of them are hospitalized due to dengue hemorrhage fever. After 1989 in Sri Lanka there is a trend to increase the number of dengue patients. Most of the deaths were reported from the urbanized districts like Colombo, Kandy, Gampaha, and Kurunagala.

Causative agent:  A virus

Vectors: Two mosquito species named Aedes aegyptii, Aedes albofictus. Feed on human blood in the daytime (diurnal) mostly activated within the hours 7.00 am- 10.00 am and 3.00pm- 5.00 pm. Mosquitoes can be found among trees in the open air.

 There are two stages of the disease.

1. Dengue fever.

2. Dengue Hemorrhage Fever.

 Sign and symptoms: High fever, headache, pain under the eyes, and pains in muscles and bones sometimes red patches can be seen on the skin.  These will last after 3 or 4 days. If we suspect a person to have dengue fever we should,

1. Reduce the temperature of him by wetting the body with a damp cloth.

2. Should give more fluid. (Soup, milk, fruit juice, and jeewani)

3. Allow the patient to have a rest.

4. Do not give aspirin. Paracetamol can be given four times per day.

Dengue Hemorrhage Fever: High fever. Sometimes internal or external bleeding may occur. Sometimes a patient may have a shock. After 2 or 3 days after the fever blood will flow from gums, high fever (39˚c - 40˚c) will continue for 5 to 6 days. But sometimes on the 3rd or 4th day, the fever may last.

                                           Japanese encephalitis

                   This is a disease of the central nervous system characterized by the inflammation of the brain, headache, fever, and lead to coma, double vision, and deafness.  A causative agent is a virus and the vector is a mosquito. This is a fatal disease or sometimes it may cause mental retardation or muscle paralysis.

Vector: These mosquitoes are of genus Culex. Culex gellidus Or Culex tritiniorynx species will act as active carriers. The mosquitoes lay eggs on shallow water masses which can be found in paddy fields or in puddles of any other cultivated land. So the disease is reported in areas that have agricultural lands. Mosquitoes can be found among trees in the open air. Feed on human blood and highly activated within the following period of 4.00 am -6.00 am and 6.00pm-10.00pm

                            Normally, the Japanese encephalitis virus enters the bodies of mosquitoes, pigs, birds, cattle, horses, geese, and leads their life cycle in them. In pigs, the virus grows and multiplies rapidly but they don’t show any symptoms. So pigs act as reservoirs of the virus. When mosquitoes bite these animals the virus enters into the mosquitoes. Then when a man is bitten by these vector mosquitoes he will get the disease.

Signs and symptoms: Even though they are infected by the virus, some people do not develop the symptoms of encephalitis. They show only the symptoms of viral fever and that also will last after a few days. After 5-15 days having entered the virus the signs symptoms will appear. In the first two days high fever, headache, nausea, and vomiting may occur. It is difficult to identify the disease at this stage. Then the symptoms and signs related to the nervous system may appear. They may be convulsions, stiffness of neck muscles, changes in behavior, difficulties in speaking, paralysis of one side or part of the body. Urination and defecation occur without control.

Treatments: No special treatments because the disease is caused by a virus. Careful Nursing should be done to reduce the symptoms.

Prevention of Japanese Encephalitis

•   Controlling of the other host of the pathogen. Examples: Pigs by giving encephalitis vaccination to them, reducing of raring pigs.
•  Protect the children and adults from mosquito bites.

 

• Vaccination of children (1-10yrs) by Japanese encephalitis vaccine.

 

• Controlling the mosquito population.

 

                       In Sri Lanka; this vaccination is done in June and August. Districts where vaccination is done are Anuradhapura, Polonnaruwa, Kurunagala, Puttlam, Ampara, Kalmunai, Trincomalee, Batticaloa, Gampaha, Colombo, Kalutara, Gall, Matara, Hambantota, Ratnapura.

Before vaccinating her child the mother should make aware the doctor of the following things.

        If the child has an illness at the moment of vaccination

•  If there are any drugs given to the child
• Were there any side effects due to previous vaccination?
• What are the vaccinations given to the child earlier?.Does the child have any disease in the brain or nervous system?
• After getting the vaccination did the child develop febrile fits?

                                  Suppression of mosquitoes

Before controlling the mosquito population one has to know about their life cycles. Mosquitoes are insects that lay eggs to propagate. There are 4 stages in the life cycle of mosquitoes as eggs, larvae, pupa, and adults. From these stages, the adult stage is aerial and the other 3 stages are in the water. So, if someone tries to eradicate the mosquito population only by killing one of the above stages it could not be done. So they have to understand the stages of the life cycle and their living places to get rid of them. Even though there are many campaigns to eradicate the mosquito population they flourish well in almost every part of our country.

Some of the reasons for their flourishing are as follows:

• Being insects they can withstand adverse conditions.
• Small size.
• Flying ability.
• High breeding capacity.

·         Rapid life cycles(Can make a new progeny within a short period)

·         Having 4 stages in the life cycle and different stages living in different places.

There is one chance in suppressing the mosquito population that is they need water to breed or to complete their life cycle. So removing the breeding places of mosquitoes as far as possible can suppress them to a certain extent. But we know the quality and the amount of water they need to breed are different from one mosquito species to another. We know that the mosquito species which carry causative agents for dengue fever need a very small amount of water. Some plants of the family Bromeliaceae such as pineapple collect water at the base of their leaves. Even in these places with that small amount of water they can breed well. So they can breed in many places we can’t think even.

The following table shows the breeding places of some of the mosquito vectors.

 

Mosquito species	Carrying disease	Quality of the water and breeding places
Aedes albofictus Aedes aegyptii	Dengue fever Dengue Hemorrhage Fever	In clean fresh water, a small amount of water is enough. The water is collected in thrown-away yogurt cups, coconut shells, tiers, flower vases, Base of the plant leaves such as in dracaena and plants in Bromeliaceae. Vessel breeders.
Culex quncifaciatus	Filariasis	In polluted water masses such as toilet pits, drainages, puddles where organic matter is decaying, Coconut husk pits.
Anopheles culicifacis	Malaria	In fresh clean water masses. In deserted gem mines, deserted limestone mines, granite quarries. In excavated pits for brick casting.
Culex tritrenioryncus Culex gellidus	Japanese encephalitis	In paddy fields, in other agricultural lands.

 

. Suppression of mosquitoes can be done in three ways.

 

1. Eradication of adults

       2.   Eradication of larval and pupa stages

       3.  Destroying the breeding places

 

                                                1.  Eradication of adult can be done using insecticides but it is not recommended because residues of insecticides may collect in the water masses hence to the drinking water. Further, mosquito species develop resistance to the insecticide and cannot be controlled by it again. It is not advisable to use insecticides in houses without the permission of Public Health Inspectors.

2.  Larval stages can be controlled biologically. For example, adding mosquitofish and Guppy fish into freshwater masses.

3. Destroying breeding places is a very important and less hazardous way of suppressing. Actually, everyone can help with these projects. Proper sanitation methods should practice in our day-to-day life. In every house, there should be a proper process of sanitation. Once a week they can clean their surroundings regularly. They can search for the following places such as blocked drainages, eve gutters, thrown away vessels, broken toilet pits, ant traps, ponds, collected water on the ground, flower vases, etc. There are other methods to avoid mosquito bites such as,

Using mosquito nets,

 Using mosquito repellents such as smoke of cashew husks, coconut husks. Applying citronella oil.

Closing windows before the sunset.

The government has taken many measures to suppress the mosquito population but it will be not successful without our help. So, as citizens we all have to support the projects launched by the government.