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The Vector organism that is responsible for the transmission of this disease is Female Anopheles Mosquito. Malaria is caused by four organisms:
Life Cycle of Plasmodium:
Sexual cycle in Mosquito
Asexual Cycle in humans
There are two types of host for the transmission of the malaria. These are humans and mosquitoes.
The saliva is entered by the saliva of mosquito when it bites. Plasmodium from sporozoite enters into the blood. As it enters in to the blood, the sporozoites are taken by the hepatocytes or liver cells in 30 minutes. Exo-erythrocytic phase starts when life cycle begins in the liver while erythrocytic phase starts when the life cycle starts in red blood cells. After this, a merozoite form of plasmodium is released in blood from hepatocytes.
Sexual life of plasmodium occurs in mosquito. In human RBC's, some of the merozoites give birth to the male or female gametocytes. The gametocytes containing RBC's are taken up by mosquito. In mosquito's gut, a female gamete (macrogamete) and eight male sperm like microgametes are produced. After fertilization, diploid zygote that is produced in the motile ookinete is differentiated. Motile ookinete burrow through mosquito gut and grows into oocysts. In oocyst, many haploid sporozoites are produced which then migrate to mosquito salivary glands.
Pathogenesis and epidemiology:
Pathogenesis is the mechanism by which a parasite causes the disease. Pathogenesis in Malaria is the destruction of Red Blood Cells. This results in the enlargement of the spleen.
Malaria that is caused by P. Falciparum is:
Far more RBC's destructive than any other plasmodium
More severe condition
Occlusion of capillaries
Hemorrhage and necrosis of brain (cerebral malaria)
Dark colored urine due to heamoglobinuria and it is known as Black Water fever
P. Malariae causes Quartan Malaria because it recurs in four days. Tertian Malaria is either benign or malignant. Malignant is caused by P. Falciparum while benign is caused by P. Vivax and P. Ovale.
Individuals with genetic resistance to Malaria:
Sickle Cell Anemia:
People with homozygous sickle cell anemia are protected from malaria because their RBC's produce little energy to support the growth of parasite.
Duffy Blood Group Antigen:
People who are homozygous recessive for Duffy Blood Group Antigen are resistant to P. Vivax. E.g., 90% west black Africans are recessive for this antigen.
People with glucose 6 - phosphate dehydrogenase deficiency are also resistant to severe P. Falciparum infection.
People who have partial immunity against the plasmodium based on humeral antibodies that block merozoites from invading RBC's. They develop a low level of parasitema as compared to severe life threatening infection. This condition is known as Premunition.
More than 200 million people worldwide are infected with this disease.
1 million malarial patients died every year in the world.
It occurs in tropical and sub tropical areas of Asia, Africa and Central South America.
Malaria in US is seen in people who travel to the areas of endemics infection
They should seek chemoprophylaxis for at least 3 years after leaving that area.
Abrupt onset of fever
Chills and headache
Myalgias (muscle pain)
Arthralgias (joint pain)
Fever upto 41 degree centigrade followed by drenched sweating
Splenomegaly (enlargement of spleen)
Anemia (Loss of RBC's)
Cerebral malaria and black water fever
Microscopic examination of blood by Thick and Thin giemsa stain smears where thin stain is for the identification of species while thick stain is for identification of the organisms
Ring shaped Trophozoites seen in infected RBC's
Crescent Shaped or banana shaped gametophytes of P. Falciparum
Polymerase chain reaction test detects the plasmodium nucleic acid in patient
Enzyme Link Immunosorbant Assays or ELISA tests is available for the detection of proteins specific for the plasmodium Falciparum.
Chloroquine is used for acute malaria and it only kills merozoites instead of hyonozoites.
Primaquine is used to prevent relapses
For Chloroquine resistant P. Falciparum, we use:
Combination of quinine and deoxycycline
Malarone which is a combination of atoraquone and progunail
In some sever cases, intravenous administration of quinidine + deoxycycline is used
Mostly, we use artesunate and artemether in USA because they are inexpensive and have fewer side effects.
There is lots of prevention methods used for the malarial disease.
Taking antibiotics without appearance of disease or in order to prevent the patient from a disease is known as Chemoprophylaxis. It is usually done by:
Malarone (Atoraquone + proguanil)
While travelling to areas of endemics, starts chemoprophylaxis before 2 weeks of arrival upto 6 weeks after the departure.
Other preventive measures are:
Protection at night is important
Use insecticide spray instead of DDT because the mosquito has developed resistance against it.
Epidemics of malaria in the world or a region of tropical and sub tropical areas not only results in the loss of life but also it causes chaos and bad impact on the economy of that region in every other field of life like business and education etc.
Socially, malaria is known as a deadly disease that ruins your social life completely. Due to the severely life threatening conditions caused by malaria, people are unable to carry on their daily life or business which results in the loss of the investments as well.
Dengue virus belongs to the Flairivirus class of Arbo Virus. These are single stranded, positive polarity and RNA containing virus that directly attack on the platelets in the human blood.
Transmission to Humans (contraction):
It is transmitted to the humans by AEDES AEGYPTI MOSQUITO. Human are the main reservoir for this virus. In some places, a jungle cycle involving the monkeys as reservoir is also suspected.
Clinical Presentation or Symptoms:
Dengue Virus causes three important types of the Clinical Symptoms:
Classic Dengue Fever:
This is a type of Dengue Fever and it is also known as Bread Bone Fever. It causes sudden onset with Influenza like Syndrome. The fever is responsible for Malaise which is known as Body pain in the human body. Some of its symptoms cause by this fever is:
Cough, Headache and Myalgia
Arthralgia - Joint Pain (break bone)
Enlarged lymph Nodes
Leukopenia which cause the deficiency of leukocytes or platelets in blood
It has a few sequelae and after a week its symptoms regress
Dengue Hemorrhagic Fever:
It is severe than the Classic dengue fever. Its mortality rate is up to 10%. Its initial picture is somehow same as that of Classic Dengue Fever but later, it produces a more severe stage in a patient than a classic fever consisting of:
In gastrointestinal tract
In the skin of the human body
Hemorrhagic Shock syndrome:
It occurs in patient who has infection with dengue virus for the second time. After having the second infection, the patient develops severe hemorrhage and goes into the shock.
Pathogenesis of Hemorrhagic Shock Syndrome (impact on health of a patient):
There are mainly four serotypes of a dengue virus:
When infection with the first serotype if produced, antibodies against this is produced
On the occurrence of second serotype, antibodies for second serotype is produced
In the third serotype, the antibodies from first and second serotypes cross react with each other to produce anamnestic heterotypic response is occurred
About the fourth stage, there are two hypothesis
It states that the immune complex is formed which consists of virus and antibody. It produces compliment and causes. It increases the vascular permeability and becomes a cause of Thrombocytopenia which decreases the number of platelets.
It states that second antibody increases the entry of virus into monocytes and macrophages. It results in the release of the cytokines present in these cells.
Outcome of both hypotheses:
No matter what the Pathogenesis is, the resultant outcome of both these hypotheses is:
Development of shock
Epidemiology (Distribution in world):
Epidemiology is the term that is used for the transmission of the disease from one place to another. It is not epidemic in the United States. It is epidemic in the tropical areas specially the Caribbean. In recent years, there were 100-200 cases per year are reported in USA. About 20 million people are being infected by the Dengue Virus per year, worldwide. Dengue fever is one of the most common arboviral diseases in the world. In Southern Asia, mostly the dengue hemorrhagic fever occurs while in tropical areas, most of the areas have classic dengue fever.
Laboratory Diagnosis is done by following methods:
Isolation of virus in cell culture
By serologic test i.e. by detection of IgM Antibody in patient serum
Also by detecting four folds or more rise in antibody in the serum of a patient
No antiviral therapy or vaccine is available against dengue virus
Its mortality rate is very high
It can be prevented by following methods:
Use of insecticides
Drainage of stagnant water
Close windows and doors in evening and at night
Dengue Virus is a very bad type of virus and it occurred mostly in poor and rural areas. The industries in those areas mostly depend upon the workers from those areas. When dengue fever spread out, the workers get sick by it and hence have direct impact on the factory work. Due to this, it has direct impact on the industries and economics.
Dengue Fever has direct impact on the social issues. It is unaffordable in its peak form. It has direct impact on children and pregnant women and most of the deaths in the world are of children and pregnant women.
Yellow fever is a very deadly virus and it is known for the infections developed in the people. Yellow fever is caused by Yellow fever virus and it belongs to Flair virus class of Arbo virus that is 40-50nm enveloped RNA containing parasite.
Transmission to Humans:
Yellow fever completes its life cycle in two parts:
In Jungle, monkeys are the most infected species from this virus. Monkeys are known as permanent reservoir or host.
In human beings, it is transmitted by the bite of haemagogus species of mosquito
Humans are the accidental hosts here because they are infected when they enter occupationally i.e., tree cutters or wood cutters etc.
In Urban Areas:
Urban yellow fever is a disease that is spread out in humans.
It is transmitted by the mosquito AEDES AEGYPTI
Mosquito breeds in stagnant water
Incubation period of virus for replication in mosquito is 12-14 days. It is known as Extrinsic incubation
Incubation period in humans is 3 to 6 days long and it is known as intrinsic Incubation
The patient of Yellow Fever presents with following symptoms:
Sudden onset fever
Myalgia - muscle pain
Sensitivity of light - photophobia
Damage of liver, heart and kidneys
Prostration and shock
Upper gastrointestinal tract hemorrhage
Hematemaesis (bloody vomiting)
Malena and tarry stools
Its diagnosis can be done by the isolation of virus from patient's serum and by detecting the rise of antibody titer in patient's serum.
No antiviral therapy is available and due to this reason, the mortality rate is very high.
This disease does not occur in the United States rather, it occurs in the tropical areas of the Africa and South America like Brazil etc. the disease was spread in America trough slave trade from Africa and it was known as a deadly disease in 19th century. There were many epidemics of this disease in Europe, USA and Africa in 17th century and lots of people died in the epidemics.
Cure and prevention:
It is cured by:
A liver vaccine is available in the market consisting of yellow fever virus attenuate
This vaccine imparts immunity for 10 years
As the vaccine contains living viruses, it should not be given to the immunocompromised patients, i.e. patients with low immunity.
Yellow fever is always been known as a deadly disease and it is a threat for the industries of forest and agriculture. There are also some threats that are produced due to this fever in tourism, trade and business etc.
In Paraguay, there is also a social impact of this disease. In this disease, some pesticides are sprayed on the crops and this produces more bugs than before. Due to this, it has a direct impact on the social customs and values.
West Nile Virus
Every disease is caused by something like virus, bacteria or pathogenesis. West Nile is a virus and its Causative agent is Encephalitis. Encephalitis is known as the inflamination of the human brain.
WNV belongs to the class of dangerous viruses that are known as Flair virus. It is classified in same antigenic group such as SLE Virus (St. Louis encephalitis). Flair Virus is a class of Arbo Virus Group. The main hosts and reservoirs for the West Nile virus are the wild birds.
Transmission in human (Contraction):
It is transmitted to the humans by virtue of a mosquito that is mostly known as Culex. Human beings are the dead end hosts for the virus. When it enters into a human body, its life cycle cannot progress ahead.
Epidemics (Worldwide distribution):
It has huge epidemics in the United States. In 1999, epidemic in New York City confirmed 27 cases infected by the same virus - 23 probable cases and 5 deaths. In 2000, 18 cases and 1 death recorded in United States. In July 2001, the virus caused deaths and diseases in the East Coast of USA (from New Hampshire to Florida). There were 48 cases and 5 deaths recorded in the East Coast. In 2002, there were 4000 cases and 274 deaths recorded in Colorado. Virus spread out in California in 2003 and caused 7700 cases with 166 deaths.
By isolation of virus from the brain tissues, blood or spiral flood.
Detection of antibodies in the spinal fluid
PCR based tests are also available for its diagnosis
Fever and confusion
Striking muscle weakness
Guillain Barre Syndrome in an individual over 60 years of age
The syndrome develop only in 1 percent of the infected individuals
Following are the treatments used for this virus:
No antiviral therapy is currently in used
No vaccine is available against this virus
Only Symptomatic treatment is done for an infected individual by given him drugs to alleviate the symptoms.
Blood born transmission from blood transfusion is prevented by screening tests for the virus in blood banks all over the states.
West Nile virus has a severe economical impact in a country. In USA, there is a study for WNV vaccination for this virus is going on. According to Dr. Tricia Salazar," To fully understand the impact of West Nile virus infections in equids, it is important to also consider variables beyond the cost of treating the disease, such as the cost of not being able to use the animal during its illness and recovery and the cost of disease prevention". Mostly, virus infected the poor people of a country or a state. These poor people work as a man power and labors in factories and by infecting these people it directly affected the economics of a place, area or a country.
West Nile Virus is a deadly virus and it socially affects the life of a community. It occurs mainly in slum areas where there is poverty and rate of illiteracy is high. People do not meet with each other due to the terror of being infected by an already infected person. Children are not allowed to go to school and in this way, the rate of illiteracy keep on increasing day by day.
Comparison between These four Diseases:
The following is the relative impact of malaria:
500 malarial cases registered per year
2.7 million deaths per year
Pregnant women and children under five years are its victims
12 Billion US$ annually imposed by malaria as a growth penalty
It kills about 1.1 million children every year and 2,800 deaths per day
It has a direct social and economic effect on an area
There were 5821 infected and 20 death cases registered in 2010 in Puerto Rico.
In 2010, there were total 1,508,173 registered cases in the world and it is greater than the malarial cases.
The dengue virus directly attacks on the platelets of the human blood and reduces its amount suddenly.
The sudden reduce in the WBC's causes the death of the patient immediately.
There are total 2124 deaths reported this year which is far less than malaria
It causes 2 billion dollars use as growth penalty
Directly affect the poor people who do not have money and enough resources for their treatments
There are about 300,000 reported cases for this disease.
The rate of death is greater than the Dengue virus
There are 30,000 deaths per year due to this disease
90% of the infection is spread out through the African Countries
There are WHO programs in 32 out of 44 countries and 50% of the disease is controlled.
Vaccination helps 95% people to vaccinate them for the disease and cure them
There is about 6Billion US$ penalty caused by this disease.
West Nile Virus:
The mortality rate of this disease is far less than the other above mention diseases.
There were about 635 cases recorded in United States in 2009.
This disease is spread out in western countries like Russia, USA and Romania etc.
The death rate is very low
Government is planning to develop a center for this disease to help people safer from the West Nile virus
And in my view Malaria is one of the most dangerous diseases. Africa is far and above the worst area where majority of the deaths are caused by malaria. 40% of the world population lives in a malaria risk zone which causes about 300-500 million cases of malaria per year and about 100 million deaths every single year. About 1,500 cases are reported every year in US. Malaria occurred mostly in poor and rural areas. The industries in those areas mostly depend upon the workers from those areas. When malaria spread, the workers get sick by it and hence have direct impact on the factory work. Due to this, it has direct impact on the industries and economics. Malaria has direct impact on the social issues. It is unaffordable in its peak form. It has direct impact on children and pregnant women and most of the deaths in the world are of children and pregnant women.