Tag Archives: Dengue fever

Stop Dengue in its Tracks

Dengue fever is caused by the Aedes egypti mosquito. Culex and Anophelesmosquitoes (which cause diseases like malaria and filaria) are nocturnal — that is, they emerge and bite at night. They can be effectively kept at bay by using mosquito nets while sleeping at night. Aedes egypti, however, is a daytime urban insect. It cannot live above 1,220m or fly more than a hundred metres. It is easily identifiable — its body is striped like that of a tiger. It lives in houses and breeds in stagnant water. This could be in flower vases, old tyres, upturned bottle caps, and even water that collects on leaves and plants.

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Eradication of their breeding grounds is, therefore, a Herculean task, which cannot be achieved by the government alone. Citizens need to do their bit, awaken their civic sense and keep their neighbourhood garbage free. At home, flower vases, water cooler trays, and all sorts of open containers — including broken mugs and bottle caps — should be emptied.

The government often uses frogs or sprays of insecticides to reduce the population of Aedes egypti in populated areas. The sprays need to be used every eight to 10 days to interrupt the cycle of virus transmission. Also, people must leave their doors and windows open so that the insecticide can penetrate indoors, into the nooks and crannies where the mosquitoes rest. We often close all openings to prevent the “harmful chemicals” from entering inside. This negates the effects of spraying.

Once an infected mosquito bites, there is an asymptomatic incubation period of five to six days. After this, dengue sets in abruptly with headache and high fever. There is pain behind the eyes and on moving the eyes. Severe body ache makes it difficult for the person to move, giving dengue the nickname “back breaking” fever. There may be rashes on the skin and inside the mouth. There may also be bleeding into the conjunctiva of the eyes, making them appear blood shot.

After three or four days, the temperature returns to normal. But this is only a temporary respite; the fever returns a few days later with all the previous symptoms but in a milder form. Dengue is, therefore, also called “saddle back” fever.

Unfortunately, there is no specific treatment for dengue. There is no vaccination (as yet) to prevent infection or specific antiviral medication to combat the condition. Affected persons have to ride out the disease with supportive treatment, hoping for the best. Treatment is symptomatic with paracetamol for lowering the fever and fluids for hydration. Aspirin and non-steroidal anti-inflammatory agents like brufen must be avoided. Blood transfusions may have to be given if there is bleeding and shock.

The first attack of dengue usually takes a few weeks to completely recover from. Overall, the disease has a five per cent mortality. It is especially dangerous in children. The dangerous form, called dengue haemorrhagic fever, which is accompanied by shock and bleeding, occurs with subsequent infections with the virus, especially if they are of a different “serotype”.

Humans are infective during the first three days when the virus is multiplying in the blood. During this period, it’s important they lie inside a mosquito net all day and night. This is to prevent them from infecting other members of the household.

The diagnosis is made by excluding other causes of fever. Blood tests may show a low white cell count and platelets. There are, however, some confirmatory tests, like complement fixation, Elisa and an increasing number of antibodies.

Dengue is a self-limited disease. The severity of the symptoms depends on the serotype of the virus, immunological status of the host and, to some extent, genetics.

Herbal products — such as fresh leaves and extracts of neem and tulasi — are being investigated for their anti viral and immune boosting properties. The results are not conclusive. Claims and counterclaims about the efficacy of herbal products are difficult to evaluate. Double blind control studies have not yet been done to prove or disprove their efficacy.

One can prevent mosquito bites to a certain extent by wearing long-sleeved clothing, sleeping inside a mosquito net, and using mosquito meshes for windows and doors. Water should not be allowed to stagnate in containers in and around residential areas. Adding a handful of rock salt or pouring kerosene into stagnant water prevents mosquitoes from breeding.

Remember, no vaccine or specific treatment exists — the only way to escape dengue is to prevent being stung by these pesky insects.

Source: The Telegraph (Kolkata, India)

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Second Time Dengu Attack Spells Danger

Scientists now know why a second dengue infection is much more severe than the first.
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The long-kept secrets of the dengue virus — which affects between 50 and 100 million people every year — are tumbling out.

Scientists have long wondered why a re-infection (in the same or subsequent year) causes more complications, even becoming fatal, than when it strikes the first time. The puzzle has been finally solved — by two independent research teams. The knowledge gained by the scientists is expected to help design drugs and vaccines against dengue fever, which currently has no treatment.

Normally, viruses — which have very little genetic material of their own — co-opt the host’s genetic machinery to survive and replicate. More often than not, if the host has an efficient immune system, the invaders are destroyed. In most cases, the antibodies produced by the body stay for long, if not permanently, and fight off any subsequent attack by the same virus. But in the case of dengue, the second infection proves to be much more severe than the first.

Back in the 1970s, US virologist Scott Halstead hypothesised that the dengue virus may be receiving help from the very antibodies that are supposed to fight the infection. Halstead termed the phenomenon antibody-dependent enhancement (ADE) of infection. He got an inkling of this during his extensive clinical studies in Thailand in the 1960s.

For a good part of the ensuing four decades, Halstead’s assumption remained mere theory. But in February this year, Sujan Shresta, a Nepal-born virologist at the La Jolla Institute of Allergy and Immunology in California, came up with conclusive proof for Halstead’s hypothesis. “It’s a situation where antibodies can be bad for you — it’s counter to everything we know about the normal function of antibodies,” she says.

Dengue infection is transmitted by the Aedes aegypti mosquito. There are four known strains of the virus circulating in the world. Infection can cause diseases ranging from dengue fever, a flu-like illness, to the severest form — dengue haemorrhagic fever or dengue shock syndrome. The latter can cause the blood vessels to leak, leading to life-threatening shock. It is estimated that 2.5 billion people — that is, two-fifth of the world’s population — live in regions where dengue fever is rampant. While it is more common in South East Asia and South America, the incidence is rising in India too. Since 1996, the country had witnessed a number of dengue outbreaks and a few hundred Indians die of dengue-related complications every year.

Shresta’s team at La Jolla developed the first ever mouse model to study the disease. The scientists conducted experiments to prove that certain antibodies produced by the body against the virus indeed exacerbate the condition. The four strains of the virus circulate simultaneously, says Shresta. Infection with one provides lifelong immunity against that particular strain. In subsequent infections, where a different strain of the virus is involved, the antibodies do not recognise enough of the virus to neutralise it. “This starts a cascade of unusual molecular events — the ADE process — which leads to the antibodies contributing to, rather than fighting, the infection,” she explains.

Taking the research forward, a team of UK and Thai scientists identified specific antibodies involved in the ADE process. The study, reported early this month in the journal Science, showed that the culprits are antibodies against a particular viral protein called precursor membrane protein (prM). According to the researchers, if the antibodies are present in the body, the infection spreads faster with the antibodies against prM helping the virus infect more host cells. In fact, there is a several hundred-fold increase in the number of infected cells in the presence of the antibodies, they say.

“This is a significant piece of work. It shows the exact region for the enhancement — which is the prM, and not the E region of the virus, as we have been thinking so long,” says Shamala Devi Sekaran, a virologist at the University of Malaysia who has been studying the dengue virus for years.

“The study pinpoints the nature of the antibodies that are likely to cause the severest form of the disease in humans,” says Shresta. It will greatly help those trying to develop vaccines against dengue, she adds.

“Our research gives us some key information about what is not likely to work when trying to combat the virus. We hope our findings will bring scientists one step closer to creating an effective vaccine,” says Gavin Screaton, head of medicine, Imperial College London, and lead author of the study.

The biggest challenge is that the dengue vaccine will need to provide immunity against all the four strains of the virus at the same time. “If protection is incomplete, the vaccine can potentially protect against some viruses but leave the individual primed for a more severe outcome if he or she is infected with the others,” Screaton told Knowhow.

In addition to these developments, there have been two recent breakthroughs in controlling the dengue mosquito. Oxford University scientists developed sterile male Aedes aegypti mosquitoes which have undergone successful semi-field trials in Asia. And scientists at the University of Queensland developed a mutant strain of a bacterium called Wolbachia, which halves the adult life span of female Aedes aegypti mosquitoes in laboratory conditions.


Source:
The Teleghraph ( Kolkata, India)

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New Clue to Fighting Dengue Fever

New clues into how the body fights off the tropical disease Dengue fever could help in the search for a vaccine.

The research, published in Science, also explains why those who recover from the virus have much worse symptoms if they catch it again.

Dengue fever is a viral infection spread by a mosquito bite. It is a major cause of illness worldwide, and cases are on the rise.

There is currently no licensed vaccine or drug treatment.

The researchers, based in the UK and Thailand, took blood samples from infected volunteers.

They found antibodies produced in response to the virus do not do a very effective job.

Rather than neutralising the virus, they actually help it infect more cells, springing into action when a person is infected a second time by a different strain of the virus.

Key information

This phenomenon accounts for why a second bout of dengue fever can be more severe and dangerous.

DENGUE FEVER
*Dengue fever is prevalent in sub-tropical and tropical regions including South East Asia and South America

*It is a major cause of illness worldwide, causing about 100 million episodes of feverish illness a year

*Symptoms include high fever, aching in the joints and vomiting

*Complications can rarely prove fatal

*There are four major strains of the virus

It also provides new insight into how to design a vaccine for dengue fever.

The authors of the Science paper say vaccines that steer clear of a key viral protein involved in the immune response should be the most effective.

Professor Gavin Screaton, head of the Department of Medicine at Imperial College London, led the study.

He said: “Our new research gives us some key information about what is and what is not likely to work when trying to combat the dengue virus.

“We hope that our findings will bring scientists one step closer to creating an effective vaccine.”

Professor Screaton said one of the major challenges was developing a vaccine for a virus that has four very different strains.

“The need for vaccines is enormous but the challenge is that in this case you need to hit four bugs all at once down a single needle,” he added.

Source
: BBC NEWS: May 6. 2010

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Dengue Virus Growth Protein Identified

A TEM micrograph showing Dengue virus virions ...

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By silencing genes one by one, scientists have identified dozens of proteins that help the dengue fever virus to grow and spread among  mosquitoes and humans. The research paves the way to potentially prevent or treat the disease, which infects millions worldwide every year.

Dengue is a mosquito-borne illness that can cause debilitating sickness and death. “Dengue is a nasty disease, and right now, there is no treatment for it and no way to prevent it,” said Mariano Garcia-Blanco, professor of molecular genetics and microbiology at Duke University Medical Centre (DUMC) and study co-author.

“But if we can find a weakness in the virus, we can design a strategy to fight it. This study has helped us identify some gaps in dengue’s armour,” he said.

Almost half the people in the world are vulnerable to the dengue virus, says the World Health Organisation. Public health officials are worried because dengue appears to be popping up in places where it has rarely appeared before. It may be fuelled by global warming.

Garcia-Blanco, used RNA interference (RNAi) to unlock dengue’s secrets. RNA interference is a normal biological process cells use to turn gene expression on or off depending upon which gene products, or proteins, are needed at any given moment.

“That very same system proved to be the perfect investigative tool for our study,” said Garcia-Blanco.

Garcia-Blanco and colleagues in Duke’s RNAi facility were able to knock down gene function in fruit fly cells infected with a strain of the dengue virus known as DENV-2.

Silencing one gene at a time allowed researchers to pinpoint which genes, or host factors, were essential to viral growth and which ones were not.

They used fruit flies as a model because the genetic tools needed for the same work in mosquitoes have not been developed as yet. The process yielded 116 host factors that appeared to be important for successful dengue infection in fruit flies.

In testing several of these host factors in mosquitoes at Johns Hopkins University, researchers subsequently discovered that at least one – and possibly a second – was necessary for dengue infection to occur in the insects, said a DUMC release.

Sources: The Times Of India

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Amebic Liver Abscess

Alternative Names:Hepatic amebiasis; Extraintestinal amebiasis; Abscess – amebic liver
Definition :
Amebic liver abscess is a collection of pus in the liver caused by an intestinal parasite.Organisms that carry disease can travel through the blood stream into the liver and form an abscess, a collection of infected tissue and pus.

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Amebic liver abscess is an extraintestinal manifestation caused by a protozoa Entamoeba histolytica. The disease spreads through the ingestion of cysts in fecally-contaminated food or water. The infection is worldwide, most common in tropical areas usually in developing countries where poor sanitation exist.

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This is an Abscess (walled area of infection/pus) in the liver that is caused by the organism Entamoeba histolytica.  It is common in tropical and subtropical areas (southeast Asia, Africa, India, Latin America).  In the U.S., it is most common in young Hispanic adults.  It is also seen in those with recent travels to tropical areas, homosexuals, and among the inhabitants of institutions for the mentally ill.

Causes :-
Travel to endemic areas (as above), where the cysts of the parasite may be ingested by consuming water or food contaminated by fecal matter.
Amebic liver abscess is caused by Entamoeba histolytica, the same organism that causes amebiasis, an intestinal infection. The organism is carried by the blood from the intestines to the liver.

The disease spreads through ingestion of cysts in fecally-contaminated food or water, use of human waste as fertilizer, and person-to-person contact.

The infection occurs worldwide, but is most common in tropical areas where crowded living conditions and poor sanitation exist. Africa, Latin America, Southeast Asia, and India have significant health problems associated with this disease.

Risk Factors :-
*Malnutrition
*Old age
*Pregnancy
*Steroid use
*Cancer
*Immunosuppression
*Alcoholism
*Recent travel to a tropical region
*Homosexuality, particularly in males

Symptoms :-
There may or may not be symptoms of intestinal infection. Symptoms may include:
*Right upper abdominal pain
*Right sided chest pain worse on a deep breath
*Intense, continuous, or stabbing pain
*Chills
*Diarrhea precedes infection in 20% of patients
*Fever
*General discomfort, uneasiness, or ill feeling (malaise)
*Jaundice
*Joint pain
*Loss of appetite
*Sweating
*Weight loss
*malaise

Nature of the disease:-
Most infected people, perhaps 90%, are asymptomatic, but this disease has the potential to make the sufferer dangerously ill. It is estimated by the World Health Organization that about 70,000 people die annually worldwide.

Infections can sometimes last for years. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks. Symptoms can range from mild diarrhoea to dysentery with blood and mucus. The blood comes from amoebae invading the lining of the intestine. In about 10% of invasive cases the amoebae enter the bloodstream and may travel to other organs in the body. Most commonly this means the liver, as this is where blood from the intestine reaches first, but they can end up almost anywhere.

Onset time is highly variable and the average asymptomatic infection persists for over a year. It is theorised that the absence of symptoms or their intensity may vary with such factors as strain of amoeba, immune response of the host, and perhaps associated bacteria and viruses.

In asymptomatic infections the amoeba lives by eating and digesting bacteria and food particles in the gut, a part of the gastrointestinal tract. It does not usually come in contact with the intestine itself due to the protective layer of mucus that lines the gut. Disease occurs when amoeba comes in contact with the cells lining the intestine. It then secretes the same substances it uses to digest bacteria, which include enzymes that destroy cell membranes and proteins. This process can lead to penetration and digestion of human tissues, resulting first in flask-shaped ulcers in the intestine. Entamoeba histolytica ingests the destroyed cells by phagocytosis and is often seen with red blood cells inside when viewed in stool samples. Especially in Latin America,  a granulomatous mass (known as an amoeboma) may form in the wall of the ascending colon or rectum due to long-lasting immunological cellular response, and is sometimes confused with cancer.

Theoretically, the ingestion of one viable cyst can cause an infection.

Diagnosis:
Exams and Tests
Tests that may be done include:
*Abdominal ultrasound
*Abdominal CT scan or MRI
*Complete blood count
*Liver biopsy – rarely done due to high risk of complications
*Liver scan
*Liver function tests
*Serology for amebiasis

Treatment
A medicine called metronidazole (Flagyl) is the usual treatment for liver abscess. Medications such as paromomycin must also be taken to remove intestinal amebiasis to prevent recurrence of the disease.

In rare cases, the abscess may need to be drained to help relieve some of the abdominal pain.

Prognosis:
Without treatment, the abscess may rupture and spread into other organs, leading to death. Persons who receive treatment have a very high chance of a complete cure or having only minor complications.
Possible Complications :In the majority of cases, amoebas remain in the gastrointestinal tract of the hosts. Severe ulceration of the gastrointestinal mucosal surfaces occurs in less than 16% of cases. In fewer cases, the parasite invades the soft tissues, most commonly the liver. Only rarely are masses formed (amoebomas) that lead to intestinal obstruction.

The abscess may rupture into the abdominal cavity, the lining of the lungs, the lungs, or the sac around the heart. The infection can also spread to the brain.

When to Contact a Medical Professional
Call your health care provider if symptoms develop after travel to an area where the disease is known to occur.

Prevention:
To help prevent the spread of amoebiasis around the home :
*Wash hands thoroughly with soap and hot running water for at least 10 seconds after using the toilet or changing a baby’s diaper, and before handling food.
*Clean bathrooms and toilets often; pay particular attention to toilet seats and taps.
*Avoid sharing towels or face washers.

To help prevent infection:
*Avoid raw vegetables when in endemic areas, as they may have been fertilized using human feces.
*Boil water or treat with iodine tablets.
*When traveling in tropical countries where poor sanitation exists, drink purified water and do not eat uncooked vegetables or unpeeled fruit.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.

Resources:
http://www.nlm.nih.gov/medlineplus/ency/article/000211.htm
http://www.ecureme.com/emyhealth/data/Amebic_Liver_Abscess.asp
http://organizedwisdom.com/Amebic_Liver_Abscess
http://organizedwisdom.com/helpbar/index.html?return=http://organizedwisdom.com/Amebic_Liver_Abscess&url=en.wikipedia.org/wiki/Amoebiasis#Diagnosis_of_human_illness

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