Why Mosquitoes Cannot Transmit AIDS
vito baraka
Watu wengi wanajiuliza hili swali bila kupata majibu,.....haya sasa habari ndio hiyo.
Please read!Why Mosquitoes Cannot Transmit AIDS
by Wayne J. Crans, Associate Research Professor in Entomology
Rutgers Cooperative Extension Fact Sheet # FS736
Media releases concerning the possibility of mosquitoes transmitting AIDS (Acquired Immune Deficiency Syndrome) were common when the disease was first recognized, and the subject is still addressed by tabloids that seek captivating headlines to increase their circulation. The topic was initiated by reports from a small community in southern Florida where preliminary evidence suggested that mosquitoes may have been responsible for the higher on average incidence of AIDS in the local population. The media was quick to publicize claims that mosquitoes were involved in AIDS transmission despite findings of scientific surveys of the National Centers for Disease Control (CDC) that clearly demonstrated that mosquito transmission of AIDS in that community appeared highly unlikely. Nevertheless, media releases perpetuated the concept that mosquitoes transmitted AIDS, and many people still feel that mosquitoes may be responsible for transmission of this infection from one individual to another.
There are three theoretical mechanisms which would allow blood-sucking insects such as mosquitoes to transmit HIV.
1. In the first mechanism, a mosquito would initiate the cycle by feeding on an HIV positive carrier and ingest virus particles with the blood meal. For the virus to be passed on, it would have to survive inside the mosquito, preferably increase in numbers, and then migrate to the mosquito's salivary glands. The infected mosquito would then seek its second blood meal from an uninfected host and transfer the HIV from its salivary glands during the course of the bite. This is the mechanism used by most mosquito-borne parasites, including malaria, yellow fever, dengue, and the encephalitis viruses.
2. In the second mechanism, a mosquito would initiate the cycle by beginning to feed on an HIV carrier and be interrupted after it had successfully drawn blood. Instead of resuming the partial blood meal on its original host, the mosquito would select an AIDS-free person to complete the meal. As it penetrated the skin of the new host, the mosquito would transfer virus particles that were adhering to the mouthparts from the previous meal. This mechanism is not common in mosquito-borne infections, but equine infectious anemia is transmitted to horses by biting flies in this manner.
3. The third theoretical mechanism also involves a mosquito that is interrupted while feeding on an HIV carrier and resumes the partial blood meal on a different individual. In this scenario, however, the AIDS-free host squashes the mosquito as it attempts to feed and smears HIV contaminated blood into the wound. In theory, any of the mosquito-borne viruses could be transmitted in this manner providing the host circulated sufficient virus particles to initiate re-infection by contamination.
Each of these mechanisms has been investigated with a variety of blood sucking insects and the results clearly show that mosquitoes cannot transmit AIDS. News reports on the findings, however, have been confusing, and media interpretation of the results has not been clear. The average person is still not convinced that mosquitoes are not involved in the transmission of a disease that appears in the blood, is passed from person to person and can be contracted by persons that share hypodermic needles. Here are just some of the reasons why the studies showed that mosquitoes cannot transmit AIDS:
Mosquitoes Digest the Virus that Causes AIDS
When a mosquito transmits a disease agent from one person to another, the infectious agent must remain alive inside the mosquito until transfer is completed. If the mosquito digests the parasite, the transmission cycle is terminated and the parasite cannot be passed on to the next host. Successful mosquito-borne parasites have a number of interesting ways to avoid being treated as food. Some are refractory to the digestive enzymes inside the mosquito's stomach; most bore their way out of the stomach as quickly as possible to avoid the powerful digestive enzymes that would quickly eliminate their existence. Malaria parasites survive inside mosquitoes for 9-12 days and actually go through a series of necessary life stages during that period. Encephalitis virus particles survive for 10-25 days inside a mosquito and replicate enormously during the incubation period. Studies with HIV clearly show that the virus responsible for the AIDS infection is regarded as food to the mosquito and is digested along with the blood meal. As a result, mosquitoes that ingest HIV-infected blood digest that blood within 1-2 days and completely destroy any virus particles that could potentially produce a new infection. Since the virus does not survive to reproduce and invade the salivary glands, the mechanism that most mosquito-borne parasites use to get from one host to the next is not possible with HIV.
Mosquitoes Do Not Ingest Enough HIV Particles to Transmit AIDS by Contamination
Insect-borne disease agents that have the ability to be transferred from one individual to the next via contaminated mouthparts must circulate at very high levels in the bloodstream of their host. Transfer by mouthpart contamination requires sufficient infectious particles to initiate a new infection. The exact number of infectious particles varies from one disease to the next. HIV circulates at very low levels in the blood--well below the levels of any of the known mosquito-borne diseases. Infected individuals rarely circulate more that 10 units of HIV, and 70 to 80% of HIV-infected persons have undetectable levels of virus particles in their blood. Calculations with mosquitoes and HIV show that a mosquito that is interrupted while feeding on an HIV carrier circulating 1000 units of HIV has a 1:10 million probability of injecting a single unit of HIV to an AIDS-free recipient. In laymen's terms, an AIDS-free individual would have to be bitten by 10 million mosquitoes that had begun feeding on an AIDS carrier to receive a single unit of HIV from contaminated mosquito mouthparts. Using the same calculations, crushing a fully engorged mosquito containing AIDS positive blood would still not begin to approach the levels needed to initiate infection. In short, mechanical transmission of AIDS by HIV-contaminated mosquitoes appears to be well beyond the limits of probability. Therefore, none of the theoretical mechanisms cited earlier appear to be possible for mosquito transmission of HIV.
Mosquitoes Are Not Flying Hypodermic Needles
Many people think of mosquitoes as tiny, flying hypodermic syringes, and if hypodermic needles can successfully transmit HIV from one individual to another then mosquitoes ought to be able to do the same. We have already seen that HIV-infected individuals do not circulate enough virus particles to result in infection by contamination. However, even if HIV-positive individuals did circulate high levels of virus, mosquitoes could not transmit the virus by the methods that are employed in used syringes. Most people have heard that mosquitoes regurgitate saliva before they feed, but are unaware that the food canal and salivary canal are separate passageways in the mosquito. The mosquito's feeding apparatus is an extremely complicated structure that is totally unlike the crude single-bore syringe. Unlike a syringe, the mosquito delivers salivary fluid through one passage and draws blood up another. As a result, the food canal is not flushed out like a used needle, and blood flow is always unidirectional. The mechanics involved in mosquito feeding are totally unlike the mechanisms employed by the drug user's needles. In short, mosquitoes are not flying hypodermic needles and a mosquito that disgorges saliva into your body is not flushing out the remnants of its last blood meal.--
Vito
......"If we make every attemp to increase our knowledge for
human good,it will make a diffence in us and in our world...."
ally mahadhy
Ahsante Vito,
Nimevutiwa zaidi na hii part "Mosquitoes Digest the Virus that Causes AIDS", Kumbe basi inawezekana ku extract gene inayohusika na huyo digestive enzyme toka kwa huyu Mosquitoe na ku engeneer kwa E.coli, tuzalishe kwa wingi, then tuna modify hiyo enzyme iweze kuwa administered intervenally ( i.v), since enzyme ni subsrate-specific, I think akiwa introduced safely kwa blood stream ya muathirika wa H.I.V basi ata digest huyu H.I.V na huenda ikawa ndo treatment ya H.I.V, who knows???
Au wana science kuna kitu nime ki overlook?
"...in the abundance of water, the fool is thirsty..." --- On Wed, 3/4/09, vito baraka <vitob...@googlemail.com> wrote: |
Deborah Sumari
From: vito baraka <vitob...@googlemail.com>
To: udsm-mbbgr...@googlegroups.com
Sent: Wednesday, March 4, 2009 5:59:29 PM
Subject: Why Mosquitoes Cannot Transmit AIDS
vito baraka
Kaka i am sidhani kama hao enzymes wa mosquitoes wataweza kuishi kwenye another host ,in this case human.Na vile vile those are digestive enzymes and therefore i think they wont be able to work at the optimum in the human blood stream na kwa watu wa immunologia watakuambia itasababisha pia mwili 'kutrigger' immune system against that enzyme ('strange protein') in the body,so i think itasababisha balaa badala ya tiba.Sijui wataalamu wa Immunology na Biochemistry wanasemaje?
The solutions i thnk is to work on vaccine solution that will make use human immune system against the virus. Attenuated virus and DNA vaccines are very promising.Hata pia ikipatikana chanjo,there is a stumbling block is the process of vaccine trial against HIV Virus....nani atakuwa wa kufanyiwa majaribio ya chanjo?????
Wasiwasi
Je itakuwaje if the virus will be able to evolve and be able to survive inside the mosquitoes without being digested and follow the same pathway that malaria parasite follow to complete their life cycle?
M.D. Seth
Hi all,
I would like to support the idea of directing all personal communication to individual (personal e-mail addresses). I believe anyone connected to this group has one. Greetings not accompanied by other useful stuff are not permissible here, I guess.
Keep it up guys and let us see where the science takes us (or where we take it)
Misago Seth, BVM MSc.Clinical Research (Student)
Tumaini University, KCM College, Moshi ...FIND YOURSELF AND BE YOURSELF,...BE THE BEST OF WHATEVER YOU ARE. |
M.D. Seth
Wazee, I think we are in the right track of thinking. Scientists across the glob are working tirelessly on HIV. See this info.
Gene therapy for HIV shows promise The largest clinical trial yet mounted to test a gene therapy against HIV has yielded modest benefits for patients and proved safe. "To our knowledge, our study was the first randomised, controlled study performed with gene therapy in HIV," says the head of the trial, Ronald Mitsuyasu of the University of California, Los Angeles. Patients temporarily stopped their usual regime of anti-retroviral treatment (ART) to see whether the gene therapy would work as effectively. Half the 74 patients received the treatment, and half a placebo. Although the gene therapy didn't work as well as ART, virus concentrations in blood were on average about a third lower in recipients of the treatment than in controls who received a placebo. Also, recipients had higher numbers of CD4+ white blood cells, the type that is attacked by the virus. "It provides proof of concept and early indications are that, with more refinement, this approach may be a viable one for controlling HIV directly in people without the need for continuous HIV medication," Mitsuyasu says. "From a scientific standpoint, it represents a new and potentially important and long-lasting way of controlling diseases," he adds. Cellular weapon Mitsuyasu and his colleagues took blood samples from patients and isolated CD34+ stem cells, which can mature into many types of white blood cell, including the CD4+ cells attacked by HIV. Then, they used a harmless virus to load the stem cells with an extra gene that makes a ribozyme - a pair of molecular "scissors" targeted at the virus. Earlier experiments in cell cultures showed that if such cells are invaded by HIV, the ribozyme is produced and cuts up tat, a gene essential for the virus to replicate itself. The hope was that when altered cells were returned to the patient, they would grow into white blood cells that survive attack by the virus and prevent it from multiplying and infecting other cells. Effectively, the immune system would become resistant to HIV, as the altered cells would be the only ones surviving. The results demonstrated that the patients with more altered cells had correspondingly lower levels of virus and marginally more CD4+ cells. Risky alternative However, the altered cells did wane in number towards the end of the 100-day "break" from ART treatment, the opposite of what was hoped. "Work is ongoing to develop better and more effective ways of performing gene insertion and allowing these genes to be better expressed in patients for longer periods of time," said Mitsuyasu. The altered stem cells might have worked better if existing stem cells from the bone marrow had all been destroyed beforehand, as in earlier mouse experiments, allowing the altered cells to take over in the empty bone marrow. This was too dangerous to be ethically justifiable in people, though, as the patients would have been minus their entire immune system in an experiment which may have failed to replace them. Journal reference: Nature Medicine (DOI: 10.1038/nm.1932) Read this also: Gene Therapy Shows Promise As Weapon Against HIV ScienceDaily (Feb. 26, 2009) — A new UCLA AIDS Institute study has found that gene therapy can be developed as a safe and active technique to combat HIV. Researchers involved in this first-of-its-kind study found that cell-delivered gene transfer has the potential to be a once-only treatment that reduces viral load, preserves the immune system and avoids lifelong antiretroviral therapy. The study appears in the current online edition of the journal Nature Medicine. Though modest, the results do show some promise that gene therapy can be developed as a potentially effective treatment for HIV, said lead investigator Dr. Ronald Mitsuyasu, professor of medicine and director of the Center for Clinical AIDS Research and Education (CARE) at the David Geffen School of Medicine at UCLA. "It is the first randomized controlled study done with gene therapy in HIV," said Mitsuyasu, who is also an associate director of the UCLA AIDS Institute. "What we were able to demonstrate was that the patients who received the gene-modified cells had a somewhat better suppression of their HIV viral replication after discontinuing their highly active antiretroviral therapy (HAART) treatment, compared with the controls." This was the first randomized, double-blind, placebo-controlled gene-transfer clinical trial and involved 74 HIV-positive adults. The patients received their own blood stem cells, either untreated or modified to carry a molecule called OZ1, which prevents viral replication by targeting a key HIV gene. OZ1 was safe, causing no adverse effects over the course of the 100-week trial. At the primary end-point, the difference in viral load between the OZ1 and placebo group at weeks seven and eight, after they had stopped HAART treatment, was not statistically significant. But other viral parameters did demonstrate better HIV suppression and improvement in the counts of CD4+ lymphocytes — the cell population that is depleted by HIV. The technique still needs to be developed further and perfected, Mitsuyasu said. "Part of the reason that we didn't see a larger effect is that the persistence of the anti-HIV gene in the patient's blood was not as long as we would have liked," he said. "We need to find better ways to get the genes into the patients and maintain them, which could include using different vectors to get the gene into the cells or conditioning the patients prior to gene transfer." Still, the results indicate that gene therapy could eventually be a useful tool in the fight against AIDS, said study co-author Dr. Thomas C. Merigan, the George and Lucy Becker Professor of Medicine emeritus at the Stanford University School of Medicine. He agrees that more needs to be done to perfect it. "But in the way we set up the trial with randomized placebo controls, we could dissect out that there was a positive effect in patients who had the gene successfully installed," Merigan said. "This could be a first step in developing a new method of controlling a chronic infectious disease." This study was funded by Johnson and Johnson Research Pty Limited. Grants from the National Institutes of Health also helped support part of the research. In addition to Mitsuyasu and Merigan, authors are Andrew Carr, Jerome A Zack, Mark A. Winters, Cassy Workman, Mark Bloch, Jacob Lalezari, Stephen Becker, Lorna Thornton, Bisher Akil, Homayoon Khanlou, Robert Finlayson, Robert McFarlane, Don E. Smith, Roger Garsia, David Ma, Matthew Law, John M. Murray, Christof von Kalle, Julie A. Ely, Sharon M. Patino, Alison E. Knop, Philip Wong, Alison V. Todd, Margaret Haughton, Caroline Fuery, Janet L. Macpherson, Geoff P. Symonds, Louise A. Evans, Susan M. Pond and David A. Cooper.
Misago Seth,BVM MSc.Clinical Research (Student) |
Tumaini University, KCM College, Moshi |
...FIND YOURSELF AND BE YOURSELF,...BE THE BEST OF WHATEVER YOU ARE. |
--- On Thu, 3/5/09, vito baraka <vitob...@googlemail.com> wrote: |
From: vito baraka <vitob...@googlemail.com> |
Date: Thursday, March 5, 2009, 2:14 AM |