Sunday, 15 March 2015

Sexually transmitted diseases (STDs)

Sexually transmitted diseases, as we can deduce through the name, are class of infections that are transmitted most commonly through sexual contact. There are some other modes of infection through which the STD’s are transmitted, though rarely. These are infections that occur in lab workers because of their working mode, from pregnant women to their children, through unhygienic practices and through fomites. Fomites are the objects/materials that can carry infections like furniture, clothes, utensils etc.  It is not possible to totally contain STD’s. The factors that are contributing to the increase in STD’s are homosexuality, change in sexual practices, permissiveness, ignorant attitude etc.

Most of the STD can be completely cured through chemotherapy. AIDS is an exception and still remains a fatal disease. Also, there are certain strains of H.ducrei and gonococci (microorganisms) that have more resistance to the commonly used chemotherapy drugs. Still, all the strains of STD inducing microorganism still retain their sensitivity to chemotherapeutic drugs and are treatable. As more than one STD inducing microorganism can be present in an STD infected person, it is better to screen the person for all STD’s including syphilis, gonorrhea, Chlamydia and HIV.

Some of the major STD are:

    Acquired Immune Deficiency Syndrome or AIDS
    Non-Gonococcal Urethritis or GNU
    Chancroid or Soft Sore
    Granuloma Inguinale
    Lymphogranuloma Venerum (LGV)
    Veneral Warts

Acquired Immune Deficiency Syndrome or AIDS

AIDS or Acquired Immune Deficiency Syndrome is caused by a retrovirus by the name Human Immuno Deficiency Virus or the HIV.

Origin of AIDS

The first case of AIDS was reported in the USA in early 1980’s many gay men reported opportunistic infections that were not easily treatable.  Soon after, HIV was discovered.

The HIV belongs to the lenti virus group of virus. A lenti virus(slow virus) is that virus which take a long time to produce the infection symptoms in the human body. It attacks the immune system of the body. Lenti virus is part of a large group of virus called retro virus. A retro virus has RNA instead of DNA as a genetic material. A retro virus replicates itself in the host cell by a process called reverse transcription. Lenti viruses are found in number of organism including cat, cattle, horse, sheep etc. Another lenti virus, by the name Simian Immunodeficiency Virus or SIV affects monkeys and is found to be 32,000 years old.

Most scientists believe that the ancestor of HIV is SIV. This is so because investigations have revealed that the structure of SIV is similar to the HIV 1 and HIV 2 viruses. HIV 1 is the predominant virus found in humans. The HIV 2 strain has a close resemblance to the SIV that has been found in the smooth collard monkey found in Western Africa. The AIDS epidemic causing HIV 1 has been found to closely resemble the SIV found in chimpanzees. Still, there are certain differences between the 2 viruses.

Theories for HIV cross over to humans

Viruses are capable to transfer themselves from one species to another. The SIV found in apes is said to be transferred from other primates. There are many theories which suggest how the virus might have crossed over to humans. Some of these are listed below.

The hunter theory

It suggests that the killing/hunting and eating for apes led to the transfer of HIV 1 from apes to humans.

The oral polio vaccine theory

The theory suggests that HIV was transferred by medical interventions. It suggests that the virus was transferred to humans in the process of testing of polio vaccine in chimps and its subsequent transfer to humans during 1950’s.

Some of the earliest known HIV infections are-

1. A plasma sample of a native of Congo taken in the year 1959.

2. A sample of lymph node of a Congo adult takes during the year 1960.

3. Tissue ample of an American who dies in the year 1969.

It was deduced in the year 1998 that HIV 1 was introduced in humans in between 1940 and 1950. The finding was based on a plasma sample form the year 1959.

However a study in 2008 said that HIV originated between 1884 and 1924.

Most of findings suggest that the virus was transferred in humans in Africa. It spread through other continents through travelling humans and the sexual contacts they made. Other means, for example blood industry, also contributed to the spread of AIDS epidemic.

Cause of spread of AIDS infection

The most common means of spread of the AIDS causing virus HIV is sexual intercourse which can be homo or heterosexual in nature.  Contaminated needles, syringes, infected blood and blood products transfusion can also transfer HIV virus. The HIV virus can also be transferred through an infected mother to the fetus.

The HIV infection

The AIDS virus infects the brain cells, lymphocyte and other cells of the body. When the body is infected with the AIDS virus, the immune response of the body weakens. It weakens as the AIDS virus destroys the lymphocytes and replaces and replicates them with its own viral strands. The AIDS virus also impairs the functioning of other helper T cells, B cells and macrophages. The mean incubation period of AIDS virus is 4.5 years i.e. in 4.5 years a patient is fully affected by HIV. AIDS virus destroys the cellular arm of the immune system and the infected person cannot overcome and cannot recover from any opportunistic pathological condition.

The body develops antibodies for HIV in a mean time period of 6 weeks. The patients become carriers of the disease and may transfer the infected disease through the above mentioned modes. Some patients develop febrile illness. Next the patient develops Lymphadenopathy or abnormal lymph Nodes. In Lymphadenopathy, other pathological conditions such as Herpes Zoster or Oral Candidiasis may occur. In the final stage of HIV infection, the patient can suffer from some kind of opportunistic infection like pneumonia, candidiasis, tuberculosis, meningitis, neurological disorder, malignancy etc.

Life phases of HIV virus

Like other microorganism, the pathological HIV virus spreads inside the human body once it infects a person.  Inside the human body, we can divide the life phases of HIV infection in the flowing phases.

A person is affected by the HIV and the HIV virus starts to freely circulate in the blood.
The free HIV virus circulating in the blood attaches itself to a healthy T lymphocyte cell or CD4 cell through the cell’s receptors.
The HIV empties all its cellular contents in the infected cell.
The reverse transcriptase enzyme of the HIV starts building the HIV DNA inside the infected cell.
The HIV integrase enzyme inserts the HIV DNA into the chromosomes of the infected cells.
Now, when the infected cell reproduces the HIV DNA and HIV virus present in it produces raw material for the manufacture of new HIV cells.
The protease enzyme cuts the long HIV proteins into individual HIV proteins. Assembly of a new HIV virus occurs with the combination of these new short proteins with the genetic material of the virus.
The new immature HIV virus forms inside the infected cell from where it is slowly pushed into the extracellular environment by a process called budding.
The immature virus develops into a mature virus and is ready to infect a new healthy cell.
The cycle goes on and more HIV infected cells are formed in the body.

Stages of AIDS

When a person gets infected with HIV, he/she develops AIDS.  A person’s response to the HIV infection is based on certain factors like his/her genetic makeup, the HIV subtype that has infected the person, stress level, co-infection, nutrition, age etc. The spread of infection inside the human body has been divided into certain stages. The stages of AIDS have been described below.

Acute infection stage

This is the first stage of progression of AIDS. Most people who get infected with HIV develop flu like symptoms. As this point of disease progression, the lymphocyte count or the CD4 count of the body drastically reduces as more and more of the CD4 cells get replaced by the HIV viral strands.  Symptoms like swollen glands, muscle and joint aches, fever, head-ache, rash and fatigue develop in the patient. The amount of HIV virus increases to a point/quantity in the human body called as the viral set point. At this point, the amount of virus in the body is stable. When the amount of virus reaches the viral set point, the CD4 count in the body starts to increase. Still, the amount of CD4 count in body never again reaches the pre-infection levels. Start of Anti retro viral therapy or ART at this point benefits the person. At the viral set point, the fluids of the infected body contain high amounts of HIV and thus the person can transmit the disease to another person through sexual contact and by other means easily.

Clinical Latency Stage or CLS

In this stage, though the HIV virus develops into the human body, there are no HIV infection symptoms. Even if there are any symptoms, they are very mild. During the clinical latency stage, the HIV virus reproduces at a very slow stage. If a person gets ART at this point of time, he/she may live further for several decades. The CLS lasts for an average of 10 years in the persons who do not take ART.

AIDS or Acquired Immune Deficiency Syndrome

This is the last stage of HIV infection. At this point of time, the CD4 count of the body has fallen drastically. Thus the body becomes highly prone to infection related cancers and other infections that are collectively called opportunistic infections. The normal CD4 count of the body is between 500 to 1600 cells per millimeter cube of blood. At the stage of AIDS, the CD4 count has been reduced to 200 cells per cubic milliliter of blood. If a person does not take ART at this point of time, he/she lives for further 3 years. A dangerous opportunistic illness and infection can reduce life to 1 year. People who get ART early mostly do not progress to AIDS. They also enjoy a near normal life span. 

AIDS Prevention

The treatment of is still in an imbecile stage. Thus, it is more convenient to prevent occurrence of disease by taking necessary steps. The spread of AIDS can be controlled by:

Taking precautions during sexual intercourse) like use of condoms.
Not having multiple sexual partners.
Use of sterilized needles and syringes
Following good blood banking practices.
Avoidance by pregnancy of women who have HIV infection.

Factors responsible for in curability of AIDS

The HIV virus is a very potent microorganism. Drugs are not able to fully control the spread of microorganism inside the body.  Factors responsible for impotent treatment of HIV are:

HIV infects the brain cells.
HIV becomes a part of the cells that it infects.
Most of the antiviral drugs are not able to cross the blood brain barrier.
The virus becomes resistant to single drug.
HIV drugs are toxic to the human body and many other pathological conditions, for ex. Anemia develop during the course of treatment.

Anti Retroviral therapy

There is no complete of the HIV infection as the virus irreversibly damages the immune system. Also, there is no drug that can completely eliminate the HIV virus from the human body once it gets infected. The therapy of AIDS focuses on improving the quality of life of the patient so that he/she can live longer. Anti Retroviral Therapy is the use of combination of drugs for treating AIDS. Like most others serious pathological conditions, for example cancer, HIV is also treated with combination of drugs.

Drugs used in the treatment of AIDS can be classified as follows.

Nucleoside reverse transcriptase inhibitors- Azidothymidine, Didanosine, Zalcitabine,  Stavudine, and Lamivudine
Non nucleoside reverse transcriptase inhibitors-  Nevirapine, Delavirdine and Efavirene.
Nucleotide reverse transcriptase inhibitors- Adefovir
Protease reverse transcriptase inhibitor- Ritonavir, Saquinavir and Indinavir.

Mode of action of HIV curing drugs

 Different drugs have different mode of action. The drug may get incorporated in the DNA of the HIV virus. It then ends the chain synthesis of the HIV DNA. The drugs can also inhibit the functioning of HIV’s reverse transcriptase enzyme and inhibit its growth. The protease inhibitors block the infectivity of viral strands and arrest their maturation. An HIV drug can also inhibit the protease enzyme of HIV that causes its maturation.

The current way of treating HIV is through a combination of these drugs. Thus nucleosides, reverse transcriptase inhibitors and protease inhibitors are combines to fight AIDS.

Recent developments in AIDS control

The first national aids control program- NACO was launched in India in the year 1992. The global community gave due weight age for an effective program which can combat HIV spread in the United Nations Millennium Declaration in the year 2000. The first declaration by the member states of UN was done in 2001. There were also political declarations in the year 2006and 2011. The national aids control program’s goals of India are aligned with the goals of the 12th 5 year plan of the government of India. Now, the aids control programs of India aims at reversing the AIDS epidemic. The NACO program is in coordination with the UNAIDS program. A combined effort by the UN country team, NACO group, other UN agencies and other community and co-operative societies has been launched to control AIDS.

Through combined and sustained efforts. India has been able to reduce the spread of the epidemic by 50% between the years 2001 and 2012, As per the UNAIDS global report, the access of individuals to AIDS retro viral therapy has been improved. Thus, the figures of AIDS related deaths have come down. Still, India has the third largest number of AIDS patients. Some population groups and some geographical areas of India still show increase in AIDS related cases.

The new AIDS prevention efforts aim to:

Prevent dying of HIV infected mothers and providing them retroviral therapy so that there are lesser chances of the baby being infected with HIV.
Reduce the sexual transmission of the HIV virus.
Increasing access to retro viral therapy.
Prevent tuberculosis deaths that result because of HIV infection.
Providing HIV services to people in prisons and other closed areas.
Increasing awareness in drug users and abusers so that they are not infected with HIV infected syringes and needles.
Reform laws, policies and practice so as to control the spread of AIDS epidemic.
Address the issue of AIDS in all kinds of humanitarian gathering and emergencies.
Integrate HIV response with other food and nutrition programs to provide education for AIDS prevention and treatment.
To make the people more aware of the disease through awareness announcements on radio and television.
To mobilize the private sector for strengthening aids response.

2. Gonorrhea

Gonorrhea is caused by gonococci, a bacterium.  The disease is spread through sexual contact and by an infected mother to her child. Almost all the strains of gonococci are sensitive to penicillin. It is more difficult to treat gonorrhea in women than in men.

3. Syphilis

The causative microorganism of syphilis is the Spirochete bacterium Tresponema Pallidum. The microorganism can be transmitted through sexual contact or from mother to fetus during pregnancy. The most common drug and the drug preferred for treating syphilis is Penicillin. 90 percent of syphilis cases can be treated if it is diagnosed early and adequate treatment is provided.

The first four years of disease infection are termed as early syphilis. In the infectious stage of early syphilis, the patient develops surface lesions that are highly contagious. The latent phase of early syphilis characterizes a positive serological test though there are no lesions and the Cerebro Spinal Fluid of the CSF is normal. Late syphilis occurs after the early syphilis (after 4 years). Cardiovascular Syphilis, Late Neuro-syphilis and Late Latent Syphilis characterize this condition.

4. Non-Gonococcal Urethritis or GNU

Like all other STD except vaginalitis, GNU occurs in both men and women and is a sexually transmitted disease. The causative organisms of NGU include Trichomonas vaginalis, Chlamydia trachomatis, and some other urinary tract infection causative organism. In GNU, the urethra becomes inflamed.  The symptoms of NGU are frequent urination, a white discharge during urination, sensation of pain or burning during urination, itching, irritation etc. The common drugs used for treating GNU include doxycycline, erythromycin, tetracycline and azithromycin.

5. Chancroid or Soft Sore

 H.ducrei, a bacterium is the causative organism of Chancroid. The disease is characterized by painful sores in the genetalia. Lymphadnopathy can also occur in a Chancroid patient. The antibiotic preferred for treating the disease is erythromycin.

4. Granuloma Inguinale

The disease is caused by Donovania Granulomates, a bacterium. The disease is characterized by ulcerative lesions in the genital areas. Drugs used for treating GI are ampicillin, erythromycin, tetracycline and streptomycin.

5. Vaginitis

Vaginitis is caused by C.albicans (yeast), Gardenella vaginale (bacteria) and Trichomonas vaginale. The disease is characterized by pain, irritation and discharge.  Other symptoms include pain during intercourse and foul odor form the vagina. Different kinds of Vaginitis include sexual atrophic vaginitis, candida vaginitis, bacterial vaginitis and trichomonas vaginalis. Apart from sexual contact, irritant vaginitis can also be caused by allergic reaction to external substances like soaps, perfumes, condoms etc. Flucanazole, metrondiazole, clindamycin, tinidazole and clotrimazole are preferred antibiotics for treating the disease. The disease can be prevented by performing safe sexual practices, by maintain hygiene of the genital areas and by eating healthy diets.

6. Lymphogranuloma Venerum (LGV)

The disease is caused by Chlamydia and is characterized by infectious lymph nodes and lymph. Symptoms of the disease depend on the mode of entry of the Chlamydia pathogen inside the human body. When the bacterium enters through the mucous linings of the genitals then abscesses in the groin region occur. If the infection occurs through rectal mucosa then rectal syndrome arises that are characterized by inflammation of the colon and rectum. When pharyngeal tissue gets infected, then buboes in the neck region occur. In the early stages of LGV, genital ulcers occur that are painless. In the secondary stage, the infection spreads throughout the body via lymphatic drainage pathways. In this stage, different manifestations of the disease can be seen that depend on the pathway of infection. These are lymphangitis, lymphadenitis, proctisis, rectum/colonic mucosa inflammation, cervicitis, perimetrisis etc. Later the lymph nodes start enlarging and are called buboes. Tetracycline or doxycycline is preferred drugs for treatment.

7. Veneral Warts

A local virus infection can cause this disease. The wart growth is enhanced by moisture presence at the infected areas while dryness inhibits the growth. The newest drug for treating venereal warts is Imiquimoid.

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