Confirmatory test for TB

If any person has positive TB skin test or QHT - G test then some additional tests should be performed for confirmation of TB infection. These usually include a chest x - ray & test of the phlegm coughed up by the patient. This is done because pulmonary TB is most common & it is highly contagious unlike other forms of TB. If these tests show negative results then one should go for other types of TB. For this purpose blood & urine samples of the patient will be tested. If one has active TB disease then he/she should start taking medicines as directed by the physician. One should also keep in mind that to treat TB one has to take medicine for at least 6 months even if the symptoms are no longer existing (i.e. have to complete the course). Otherwise the TB bacteria will develop resistance against the drugs, as latent asymptomatic form may still exist in the patient’s body if the course of medicine is not followed.

New findings in Malaria

Malaria is one of the most important infectious disease in human history. To eliminate Malaria, countries must treat their entire population, even asymtomatic adults. But there's rarely enough money and medicine for developing nations to do that. So Doctors focus their energies on the young people who are clearly ill. Adults who have developed some level of immunity to malaria end up as reservoirs for parasites, continuing to spread the illness without ever feeling sick.

QuantiFERON TB Gold or QFT G Test

QFT - G is a blood test is another very useful test to find TB infection. The QFT - G test measures the response t TB proteins when they are mixed with a small amount of blood collected from the patient. But the problem is that there are very few clinics, which actually offer this test. The test requires only one visit to the clinic instead of two in case of TB skin test.

Resistance of Malaria parasite against Chloroquine

Malaria was treated with quinine in the past. Recently Chloroquine (a derivative of quinine) is used effectively especially against Plasmodium falciparum. But recently Plasmodium falciparum (the deadliest of all) developed resistance against chloroquine. Malaria can be easily prevented using good health-care infrastructure. So there may be no requirement of drugs in 1st World Countries. But in third world countries like India the disease is treated primarily through chemotherapy. So scientists are searching for new drugs and also want to explore the reason behind resistance development. Recently $ 1.5 million grant is sanctioned from National Institute of Health (NIH) USA for this purpose. So we may hope something interesting in the coming year.

TB Skin Test

Today we will know about TB skin test. This test is a very good test for detection of TB infection. In that process a small amount of testing fluid (called tuberculin or PPD) is injected just under the skin on the underside of forearm. Actually tuberculin contains anti-antibody of TB bacteria. An infected person will have antibody against TB bacteria produced by immune system. So presence of antibody (against TB bacteria) confirms TB infection. After 2 – 3 days, there will be a swelling in the arm where tuberculin was injected. A positive reaction will result in more swelling due to the allergic reaction between the two antibodies. So by measuring the swelling a trained person can tell whether the person has TB infection or not.

If anyone has any question or insight regarding this feel free to ask and share.

Nine eleven and Malaria

Here I want to share another astonishing fact regarding Malaria. Do you know that malaria is responsible for 1 - 3 million deaths a year (mostly in sub-Saharan Africa), and this is equal to the death toll from the attacks of 9/11 every 8 to 24 hours. Think of it. More facts will follow.

Diagnosis of TB

Diagnosis of TB may be difficult due to the difficulty in culturing the slow growing organisms in Laboratory. So other methods besides culturing have to be employed. Medical history, chest X-ray & physical examinations are required for correct diagnosis. Currently two tests 1) The TB skin test & 2) QuantiFERON - TB Gold (QFT-G) test are employed to identify both Active & Latent form of the disease.

Testing for TB

As a precaution one should get tested for TB when one feels so. One should get tested if he/she has: -

Ø Spent time with a person having TB disease or suspected to have TB disease.

Ø HIV infection or any other immunosuppressed condition.

Ø Latent TB disease

Ø Gone to country/returned from a country with high active TB disease

Ø Gone to some areas where TB is common (homeless shelters, migrant camp, prison, hospitals etc.)

Ø Injected illegal drugs.

Mode of transmission of TB

Mode of transmission of TB is through air from infected to non-infected person when infected persons cough or sneezes. Each sneeze contains approximately 40,000 of infectious droplets (i.e. droplets containing TB bacteria) and when nearby person breath in these droplets they may become infected. The bacteria after entering a healthy individual settle in the lungs and grow and thus infection starts in the lungs of a new individual. From there they can be transmitted to other parts of the body (kidney, spine & brain) through blood and infect those organs.

One should keep in mind that though TB in lungs or throat is highly contagious that in other parts of the body are usually not. So people should be aware of the fact that person with Active lung TB (there is another Latent form of TB that I will discuss later) can spread the germ and hence family members, friends and co-workers of TB patients are the most susceptible persons to have TB.

Other strains of TB

There is not only one strain that can cause TB, instead there are many. The M. tuberculosis complex includes 3 other mycobacteria which can cause tuberculosis. They are M. bovis, M. africanum and M. microti. The first two types are very rare and cause TB usually to only immunocompromised people, and M. microti is not usually pathogenic. But in some cases it can cause minor infections.

Other names of TB

TB had many other names in the past and the most common was “Consumption”. This name came from the belief that TB consumes people from within with physical symptoms like bloodycough, fever, pallor (paleness) & relentless killing. There are many other names also arising mainly due to the fear in the past, as it was untreatable and extremely deadly. “Phthisis, phthisispulmonalis, scrofula, tabesmesenterica, lupusvulgaris, wastingdisease, white plague (due to paleness of the patient), king’s evil (it was believed that a King’s touch can heal the disease) and many more. This names originated in different communities and due to its ability to affect different parts of human body. Nowadays the term MiliaryTB is still occasionally used when the infection invades the circulatory system and the organism look like millet seeds when seen in x–ray plates although these form of TB is more commonly known as DisseminatedTB.

What is TB?

Tuberculosis (abbreviated as TB for Tubercle Bacillus) is a common and deadly infectious disease caused by the mycobacterium, Mycobacterium Tuberculosis or Mycobacterium bovis, which most commonly affects the lungs (pulmonary TB) but can also affect the central nervous system, lymphatic system, circulatory system, genitourinary system, bones, joints and even the skin. Over one-third of the world’s population now has the TB bacterium in their bodies & new infections are occurring at a rate of one per second. Not everyone who is infected develops the disease and asymptomatic latent TB infection is most common. However, one in ten latent infections will progress to active TB disease, which, if left untreated, will kill more than half of its victims. A rising number of people in developed world contract tuberculosis because their immune systems are compromised by immunosuppressive drugs, substance abuse, or due to HIV/AIDS. The rise in HIV infection levels and the neglect of TB control programs have caused a resurgence of tuberculosis.

My next focus

Hope you people have enjoyed my posts on Malaria. If you have any doubts or questions regarding Malaria, feel free to me. I will try my level best to solve your problem. Now after Malaria my focus will be Tuberculosis or TB, which, I think all know as a serious health problem especially in Third World Countries as well as in Developed Countries. So from my next posts I will try to give you an insight of TB. Happy blogging and Thank you for your support.

Prevention of Malaria

There are many ways of preventing Malaria. You can also take medicine to cure Malaria. Besides indoor residual spraying for eliminating mosquitoes & use of mosquito nets coated with insecticides during night sleep and insecticide coated bed cloths give good results. Use of DDT in the endemic areas & DDT-spraying the interior walls of living spaces, where mosquitoes land, is an effective control. A new approach, announced in Science on June 10, 2005, uses spores of the fungus Beauveria bassiana, sprayed on walls and bed nets, to kill mosquitoes. While some mosquitoes have developed resistance to chemicals, they have not been found to develop a resistance to fungal infections. Use of prophylactic drugs can be another option: - Currently available anti-malarial drugs include:

· Artemether-lumefantrine (Therapy only, commercial names Coartem® and Riamet®)

· Artesunate-amodiaquine (Therapy only)

· Artesunate-mefloquine (Therapy only)

· Artesunate-Sulfadoxine/pyrimethamine (Therapy only)

· Atovaquone-proguanil, trade name Malarone (Therapy and prophylaxis)

· Quinine (Therapy only)

· Chloroquine (Therapy and prophylaxis; usefulness now reduced due to resistance)

· Cotrifazid (Therapy and prophylaxis)

· Doxycycline (Therapy and prophylaxis)

· Mefloquine, trade name Lariam (Therapy and prophylaxis)

· Primaquine (Therapy in P. vivax and P. ovale only; not for prophylaxis)

· Proguanil (Prophylaxis only)

· Sulfadoxine-pyrimethamine (Therapy; prophylaxis for semi-immune pregnant women in

endemic countries as "Intermittent Preventive Treatment" - IPT)

· Hydroxychloroquine, trade name Plaquenil (Therapy and prophylaxis)

Severity of Malaria

P. falciparum causes the most severe type of malaria. Consequence of severe malaria include coma & death if untreated (specially children & pregnant women). Splenomegaly (enlarged spleen), severe headache, cerebral ischemia, hepatomegaly (enlarged liver) & hemoglobinuria with renal failure may occur. Renal failure may also cause black water fever, where hemoglobin from lysed RBC leaks into urine. This form cause death within hours or days in more than 20% cases even with intensive care & treatment. P. vivax & P. ovale produces chromic malaria, unlike P. falciparum. In this case the disease relapse months or years after exposure, due to presence of latent parasites in the liver. The largest incubation period reported for a P. vivax infection is 30 years. Malaria is often associated with hypoglycemia which has four causes – (i) High parasitemia (parasite’s inefficient use of glucose); (ii) you don’t as much because of loss of appetite; (iii) depletion of liver glucose & (iv) inhibition of gluconeogenesis.

More on symptoms of Malaria

The classical symptoms of malaria are cyclic occurrence of sudden coldness followed by rigor & then fever and sweating lasting 4 to 6 hr, occurring every two days. There may be a tingling in the skin as well. The symptoms vary with the species on plasmodium involved.

Symptoms of Malaria

As I have promised earlier, I am posting the symptoms of Malaria.

The following symptoms are common in malaria: -

· Fever

· Shivering

· Arthralgia (joint pain)

· Vomiting

· Anemia caused by hemolysis

· Hemoglobinuria

· Convalescence

The life cycle of Plasmodium

The life cycle of plasmodium has two stages. The asexual cycle takes place inside human body whereas the sexual cycle occurs within the body of the female Anopheles mosquitoes. Initially I thought of giving the life cycle in detail, but latter thought against it as it will be too complicated for common people without proper medical/biological back ground and hence may lose interest. So in my nest posts I will focus on symptoms, prevention & cure of malaria, which will be more useful to all.

Distribution and impact of Malaria on Human life

Malaria causes about 350 – 500 million infections in humans & approximately one to three million deaths annually – this represents at least one death every 30 seconds. Majority of the sufferers are children below 5 years. Pregnant women are also very vulnerable. Though many efforts have been made to reduce transmission & increase treatment there has been little change in the global scenario. Malaria is presently endemic in regions around equator, in areas of South America, South & South – East Asia, parts of Middle East and Oceania and much of Africa; however it is in Sub-Saharan Africa where Blue area shows the most Malaria-prone zones in 85%-90% of malaria fatalities occur. If the prevalence of
the world malaria stays on its present upwards rate, the death rate
could double in next twenty years.

More historical facts on Malaria

The protozoa were called Plasmodium by the Italian scientist Ettore Marchiafava and Angelo Celli. A Cuban doctor called Carlos Finlay, who was working in Havana, first proposed that the disease was transmitted by mosquitoes. But it was Sir Ronald Ross, a British doctor working in Kolkata, India proved that it was indeed transmitted by mosquitoes. He showed that mosquitoes are transmitting malaria to birds also isolated the protozoa from the salivary glands of mosquitoes that fed on infected birds. He received Nobel Prize for this in 1902.

History of Malaria

Malaria has infected human for over 50,000 years & may have been a human pathogen for the entire history of human being. The references of malaria were found throughout the history of human life, beginning in 2700 BC in China during Xia Dynasty. Scientific studies on malaria made their first significance in 1880 when a French Army Doctor working in Algeria (Charles Louis Alphonse Laveran) observed parasite inside red blood cell of people suffering from malaria. He then proposed that the cause of the disease is protozoa, the first time protozoa were identified as causing disease. He got Nobel Prize for Physiology or Medicine in 1907.

Female Anopheles mosquitoes

Only female mosquitoes feed on blood, thus males do not transmit the disease. The females of the Anopheles genus of mosquito prefer to feed at night. They usually start searching for a meal at dusk, and will continue throughout the night until taking a meal. Malaria parasites can also be transmitted by blood transfusions, although this is rare.

The mode of transmission of malarial parasite

Malaria parasites are transmitted to human via female Anopheles mosquito. The parasite's primary (definitive) hosts and transmission vectors are female mosquitoes of the Anopheles genus. Young mosquitoes first ingest the malaria parasite by feeding on an infected human carrier and the infected Anopheles mosquitoes carry Plasmodium sporozoites in their salivary glands.

Cause of malaria

Malaria is caused by protozoan parasite of the genus Plasmodium. The four major species involved (typically infect human) are P. falciperum, P. vivax, P. ovale, & P. malaria. Sometimes another form P. knowlesi is also found. Among them the 1st two cause the most serious forms of disease. These are collectively called malaria parasites.

Meaning of malaria

The term ‘Malaria’ derived from the Italian word “mala-aria” which means “Bad air”. Once it was thought that bad air is responsible for malaria, which off course is not true.

After the discovery of relation between human disease and bacteria, a new chapter of biological science has developed, "Medical Bacteriology". From now on my post will revolve around human disease and microbiology. Let us start with Malaria, one of the most deadliest disease in the world and in particular in India and Africa and the disease which kills around 2 to 8 million people every year. Malaria is a vector-borne infectious disease. It is one of the most common infectious diseases & is considered as an enormous public health problem in tropical & subtropical countries. Approximately 400 million people get affected each year and result in 1 to 3 million deaths annually (mostly among young children in Sub – Saharan Africa). Interestingly malaria is not considered as a disease caused by poverty but is a cause of poverty & hindrance in economic development.

Biological specificity of disease

Koch’s contribution to medical biology continues when he further established the fact of “Biological Specificity”. Now what actually Biological Specificity” means? It actually shows that a particular disease can be produced by a particular bacterium only. Other bacteria either do not produce any disease or may produce another form of disease following inoculation. He established this by trying to produce “Anthrax” disease from different types of spore forming bacillus like hay bacillus.
In the same time another interesting thing happened. J. Joubert, a person with profound medical knowledge collaborated with Pasteur and they together also started working with anthrax, a serious problem at that time. They were unaware of Koch’s advancement but the conclusions made by them were similar to that of Koch, further confirming Koch’s theory.

Koch’s postulate

Robert Koch thus has established the relationship between a specific microorganism and a specific disease. The criteria for this can be generalized as: -

1. The microorganism must be present in every case of the disease;
2. The microorganism must be isolated from the diseased host and grown in pure culture;
3. The specific disease must be reproduced when a pure culture of the microorganism and inoculated into a healthy susceptible host and
4. The microorganism must be recoverable once again from the experimentally infected host.

These criteria has been generalized as Koch’s postulate to show respect to Koch’s work.

Koch and Anthrax

After the discovery that anthrax can be transmitted from infected to healthy animal through inoculation of blood serum, Robert Koch started thinking about cultivating the causative agent of anthrax. To achieve this goal he performed a simple experiment. He took the spleen out from an infected animal and chopped it into fine particles & then dropped the particles in drops of sterile serum. He looked at it hour after hour and observed the tiny rods of bacterium forming long filaments. In between these filaments he also observed ovoid, refractive bodies somewhat different from the original bacteria (rod shaped). He mentioned that these are spores germinated from the original bacteria due to adverse environmental conditions. He was the first to isolate spores of bacteria. He eventually introduced the spores into fresh serum & again observed the formation of rods, filaments & spores. Likewise eight successive transfers of spores into fresh serum has been carried out and after that the spores were introduced in a healthy animal which rendered the animal ill. Finally the rod shaped organisms could again be isolated in culture.

Robert Koch

The proof of bacteria causing anthrax (etiology) was provided by a German country doctor Robert Koch in 1876. He was nowhere near a scientist and had no laboratory. He worked in his home with very primitive instruments and few small animals. He showed that mice cane be infected with by transferring materials (serum) from diseased animals and this he had done up-to a series of 20 mice by successive inoculation. Strikingly in every transfer the same symptoms were observed. He then performed an experiment to observe the bacterium or rather the causative agent as whether it was due to a bacterium was not clear till then.