AIDS | Zoology Optional Notes for UPSC PDF Download

Introduction

• AIDS stands for Acquired Immunodeficiency Syndrome. It is the most advanced stage of infection with the Human Immunodeficiency Virus (HIV) which kills or damages cells of the body’s immune system. HIV most often spreads through unprotected sex with an infected person, by sharing drug needles or through contact with the blood of an infected person. Women can give it to their babies during pregnancy or childbirth.
• The first signs of HIV infection may appear as swollen glands and flu-like symptoms which may come and go a month or two after infection. Severe symptoms may not appear until months or years later. The CD4 count indicates how far the HIV disease has advanced. CD4 counts in adults range from 500 to 1,500 cells per cubic millimeter of blood. In general, the CD4 count goes down as HIV disease progresses, to below 200, regardless of whether the persons are sick or not.

Mode of Infection

Once HIV enters the human body, it attaches itself to a White Blood Cell (WBC) called CD4, also called T4 cell, which are the main disease fighters of the body. Whenever there is an infection, CD4 cells lead the infection-fighting army of the body to protect it from falling sick. Hence damage of these cells can affect a person’s disease-fighting capability and general health. After making a foothold on the CD4 cell, the virus injects its RNA into the cell. The RNA then produces its DNA by using enzyme reverse transcriptase. The viral DNA then gets attached to the DNA of the host cell and thus becomes part of the cell’s genetic material.

It is a virtual takeover of the cell. Using the cell’s division mechanism, the virus now replicates and churns out hundreds of thousands of its own copies. These cells then enter the blood stream, get attached to other CD4 cells and continue to replicate. As a result the number of virus in the blood rises and CD4 cell count declines.

There are several common ways that HIV can be passed from person to person that include:

• Having unprotected sex with someone who is infected
• Using needles or syringes that have been used by people who are infected
• Receiving infected blood products or transplanted organs.
• Transmission from mother to child – An infected mother may pass the virus to her developing fetus during pregnancy, birth or through breastfeeding.

Symptoms

Many people do not develop any symptoms when they first become infected with HIV. Some people, however, get flu-like illness within three to six weeks after exposure to the virus. This illness, called Acute HIV Syndrome may include fever, headache, tiredness, nausea, diarrhea and enlarged lymph nodes. These symptoms usually disappear within a week to a month and are often mistaken for another viral infection. During this period, virus in the body abounds and spreads to different parts, particularly to lymphoid tissue. At this stage, the infected person is more likely to pass the infection to others.

More severe symptoms may not surface for several years, even a decade or more after the first entry of the virus or within two years in children born with the virus. Some people may begin to have symptoms as soon as a few months while others may be symptom-free for more than 10 years. During the “asymptomatic” period, the virus will be actively multiplying, infecting, and killing cells of the immune system. The following symptoms may appear in the infected person:

• Lack of energy.
• Weight loss.
• Frequent fevers and sweats.
• A thick, whitish coating on the tongue or mouth that is caused by a yeast infection and sometimes accompanied by a sore throat.
• Severe or recurring vaginal yeast infections.
• Chronic pelvic inflammatory disease or severe and frequent infections like Herpes zoster.
• Periods of extreme and unexplained fatigue that may be combined with headaches, lightheadedness or dizziness.
• Rapid loss of weight that is not due to increased physical exercise or dieting.
• Bruising more easily than normal.
• Long-lasting bouts of diarrhea.
• Swelling or hardening of glands located in the throat, armpit or groin.
• Periods of continued, deep and dry coughing.
• Increasing shortness of breath.
• The appearance of discolored or purplish growths on the skin or inside the mouth.
• Unexplained bleeding from skin mucous membranes or from any opening in the body.
• Recurring and unusual skin rashes.
• Severe numbness or pain in the hands or feet, loss of muscle control and reflex and paralysis or loss of muscular strength.
• An altered state of consciousness, personality change or mental deterioration.
• Children’s growth may be slow or they may fall sick frequently. HIV positive persons are also found to be more vulnerable to cancers.

Symptoms In Females

• Although most of the symptoms of HIV infection are similar in men and women, some are more typical of females. For example: Vaginal yeast infections may be chronic, more severe and difficult to treat in women with HIV infection than in healthy women.
• Pelvic inflammatory disease, an infection of the female reproductive organs, may also be more frequent and severe in women with HIV infection. Human papillomavirus (HPV) infection, which causes genital warts may occur more frequently in HIV-infected women and can lead to pre-cancerous lesions of the cervix or cancer of the cervix.

Opportunistic Infections

The number of CD4 cells per ml of blood which ranges from 500 to 1,500 in a healthy individual falls below 200 in AIDS infected people. The Viral Load will be very high at this stage. Opportunistic infections are caused by bacteria, virus, fungi and parasites. Some of the common opportunistic infections that affect HIV positive persons are: Mycobacterium avium, Tuberculosis, Salmonellosis, Bacillary Angiomatosis, Cytomegalovirus, Viral hepatitis, Herpes, Human papillomavirus, Progressive multifocal leukoencephalopathy; Candidiasis, Cryptococcal meningitis and Pneumocystis Carinii pneumonia, Toxoplasmosis, Cryptosporidiosis. HIV positive persons are also prone to cancers like Kaposi’s sarcoma and lymphoma.

Diagnosis

• In the early stages of infection, HIV often produces no symptoms and the infection can be diagnosed only by testing a person’s blood. Two tests are available to diagnose HIV infection — one that looks for the presence of antibodies produced by the body in response to HIV and the other that looks for the virus itself. If antibodies are present, the test gives a positive result.
• A positive test has to be confirmed by another test called Western Blot or Immunoflouroscent Assay (IFA). All positive tests by ELISA need not be accurate and hence Western Blot and other tests are necessary to confirm a person’s HIV status. ELISA requires specialized equipment and blood samples need to be sent to a laboratory. To cut short this waiting period, Rapid Tests that give results in 5 to 30 minutes are increasingly being used the world over.
• The HIV antibodies generally do not reach detectable levels in the blood till about three months after infection. This period, from the time of infection till the blood is tested positive for antibodies is called the Window Period. Sometimes, the antibodies might take even six months to show up. Even if the tests are negative during the Window Period, the amount of virus may be very high in an infected person.

Prevention

• Because there is no effective vaccine and no cure for HIV, the only way to protect one is by taking preventive measures.
• People should either abstain from having sex or use latex condoms during sex. People who are allergic to latex can use polyurethane condoms.
• Although some laboratory evidence shows that spermicidal creams can kill HIV, there is no conclusive evidence if it can prevent transmission.
• The risk of HIV transmission from a pregnant woman to her baby is significantly reduced if she takes AZT during pregnancy, labour and delivery and her baby takes it for the first six weeks of life. Nevirapine is also found to be useful.
• Having a sexually transmitted disease (STD) can increase a person’s chances of getting HIV through sexual contact. Hence it is necessary to treat STD as soon as possible.
• All donated blood must be screened for HIV as well as for Hepatitis B and Syphilis.

Treatment

Three classes of drugs are available for treatment of AIDS.

1. Nucleoside analogueReverse Transcriptase Inhibitors (NRTIs). These were first antiretroviral drugs that were developed for inhibiting the replication of HIV in the early stage by inhibiting an enzyme called Reverse Transcriptase. The drugs include Zidovudine (Retrovir, AZT), Lamivudine (Epivir, 3TC), Didanosine (Videx, ddI), Zalcitabine (Hivid, ddC), Stavudine (Zerit, d4T) and Abacavir (Ziagen).

The major reported side effect of Zidovudine is bone marrow suppression, which causes a decrease in the number of red and white blood cells. The drugs ddI, ddC and d4T can damage peripheral nerves, leading to tingling and burning sensation in hands and feet. Treatment with ddI can also cause pancreatitis, and ddC may cause mouth ulcers. Approximately 5 percent of people treated with Abacavir experience hypersensitivity with rash along with fever, fatigue, nausea, vomiting, diarrhea and abdominal pain. Symptoms usually appear within the first 6 weeks of treatment and generally disappear when the drug is discontinued.

2. Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs). These drugs bind directly to the enzyme, Reverse Transcriptase. There are three NNRTIs currently approved for clinical use: Nevirapine (Viramune), Delavirdine (Rescriptor) and Efavirenz (Sustiva). A major side effect of all NNRTIS is appearance of rash. In addition, people taking Efavirenz may also have side effects such as abnormal dreams, sleeplessness, dizziness and difficulty concentrating.

3. Protease Inhibitors (PIs). They interrupt HIV replication at a later stage in its life cycle by interfering with an enzyme known as HIV protease. This causes HIV particles in the body to become structurally disorganized and noninfectious. Among these drugs are Saquinavir (Fortovase), Ritonavir (Norvir), Indinavir (Crixivan), Nelfinavir (Viracept), Amprenavir (Agenerase) and Lopinavir (Kaletra).

The triple cocktail treatment, also known as Highly Active Antiretroviral Therapy(HAART), is the closest thing that medical science has to an effective therapy, which has the ability to disrupt HIV at different stages of replication. Reverse transcriptase inhibitors, which usually make up two drugs in the HAART regimen, restrain an enzyme crucial in the early stage of HIV replication. Protease inhibitors hold back another enzyme that functions near the end of the HIV replication process.

As of now, there is no vaccine to prevent HIV infection.