Structure of dengue virus

  Malaria and dengue

Difference between Malaria and Dengue fever 

♣ Malarial is spread by a female mosquito Anopheles wherease Dengue fever is spread by Aedes aegypti.
 ♣ Symptoms of Malaria are Severe chills with goose flesh and shivering with high fever.

 

Malarial vector(Anophelis)

General headache,fever becomes normal by profuse sweating after a specific time (3-4) but if not treated, it occurs again after an interval depending upon the life cycle of Plasmodium (usually 48 hours).There will not be muscle ,joint pain, rash on the body and leakage of fluid / plasma from blood capillaries. Symptoms of Dengue Fever are high fever , chill and headache especially behind the eyes. There is high fever which become normal after 2-7 days and no recurrence of fever. There is severe muscle and joint pain and rashes on the body.There is leakage of fluid/plasma from the blood capillaries. 

Dengue vector(Aedes Aegypti)

♣Anopheles prefer to live outdoors and dirty water. Aedes prefer to live close to human habitat in urban areas particularly indoors 
♣ Anopheles is mostly active at night but Aedes is active at day time and aggressive biter with feeding peaks of two hours before and after dawn and dusk. 
 ♣ Primary infection y Anopheles cannot induce life long protective immunity and secondary infection is not severe than primary infection. Primary infection can induce life long protective immunity to the infecting serotype. Secondary infection by some other serotype is severe than primary infection. 
♣ Malaria can be treated by bed rest, sponging and anti malarial drugs. While dengue can treated by 
♣ Bed rest, sponging, rehydration (more fluid intake), anti pyretic drug. Structure of dengue virus clip_image002 Dengue virus This tiny creature contains all information for its horrible mode of attack on poor patient .
 Dengue Virus has four distinct serotypes, known as DEN-1 DEN-2, DEN-3 DEN-4 Dengue virus is transmitted by the bite of infected female of Aedes mosquito. 
It can also be transmitted by infected blood products and through organ transplant. The life cycle of the dengue virus involves mosquito as a vector and human beings as a host. Man is the primary host and can be infected by a single bite of infected Aedes. After getting entry into the human blood stream through the mosquito's saliva, the virus attacks and reproduces in various target cells, in skin, lymph nodes and liver. New viruses attack white blood cells to further increase in number.
 WBCs produce a number of proteins, responsible for many of the symptoms such as fever, flu and severe pains. Mosquitoes are important vectors of human and animal diseases. Aedes aegypti and Aedes albopictus are considered as vectors of dengue virus . The male mosquitoes of all types feed only on plant juices while females, in addition to plant juices, may feed on blood. It needs blood proteins to produce eggs. 
Without blood meal it cannot lay eggs. Aedes female generally acquires the virus by feeding on the blood of an infected person. Virus replicates within its body. It then moves to the mosqjuito's salivary glands where it continues to replicate. Life cycle in the mosquito usually completes within 8-10 days, depending upon suitable environmental conditions, especially temperature. The virus seems to have no harmful effect on infected mosquito, which can transmit the virus to human beings during blood meal. Infected female may also transmit the vims to its next generation through her eggs. Water is necessary for all mosquitoes to complete their life cycle. 
Their development shows complete metamorphosis with four stages; egg, larva, pupa, and adult .The first three stages occur in water while adult stage can fly in air freely. The life span from egg to adult takes about one to six weeks, depending upon the availability of food, optimum temperature and humidity. The most favorable temperature is twenty eight to eighty percent humidity.  

Eggs of Dengue vector

Aedes mosquitoes prefer to lay eggs on rough and moist surfaces. The eggs of Aedes are black in color and ova1 in shape. They are shielded by a rigid shell having minute pores for g;as exchange. Each female can lay eggs upto five times in her life and the number of eggs varies from fifty to three hundred eggs. 
Eggs of Aedes remain donnant in winter and can withstand drying up to one year. They can hatch when water is available. Exposure to high humidity at the water line for two to three days is required for larva to hatch from the egg. 

 Larva of dengue vector

Larva has a well-developed head with mouth brushes for feeding, a large thorax, a long abdomen and has no legs.
 The posterior part of the abdomen has four lobed gills and a shorter air tube (siphon) used for breathing. They actively feed on bacteria and tiny organic matter found in water. 

  Pupa of dengue vector

After replacing its covering four times, it becomes pupa within two to four days. 
Pupa is motile but does not feed at all. 

Adult Dengue vector

This stage ends by shedding of pupal case and emergence of adult within one to two days. The newly emerged adult rests on the surface of the water for a short time to allow itself to dry and its parts to harden. The adult mosquito usually lives for 2-4 weeks. 
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