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.