The Polymerase Chain Reaction (PCR) has found widespread application in many areas of genetic analysis. This is a list of some of these applications:
1 Medical applications
2 Infectious disease applications
3 Forensic applications
4 Research applications
Medical applications
PCR has been applied to a large number of medical procedures:
The first application of PCR was for genetic testing, where a sample of DNA is analyzed for the presence of genetic disease mutations. Prospective parents can be tested for being genetic carriers, or their children might be tested for actually being affected by a disease. DNA samples for Prenatal testing can be obtained by amniocentesis, chorionic villus sampling, or even by the analysis of rare fetal cells circulating in the mother's bloodstream. PCR analysis is also essential to Preimplantation genetic diagnosis, where individual cells of a developing embryo are tested for mutations.
PCR can also be used as part of a sensitive test for tissue typing, vital to organ transplantation. As of 2008, there is even a proposal to replace the traditional antibody-based tests for blood type with PCR-based tests.
Many forms of cancer involve alterations to oncogenes. By using PCR-based tests to study these mutations, therapy regimens can sometimes be individually customized to a patient.
Infectious disease applications
Characterization and detection of infectious disease organisms have been revolutionized by PCR:
The Human Immunodeficiency Virus (or HIV), responsible for AIDS, is a difficult target to find and eradicate. The earliest tests for infection relied on the presence of antibodies to the virus circulating in the bloodstream. However, antibodies don't appear until many weeks after infection, maternal antibodies mask the infection of a newborn, and therapeutic agents to fight the infection don't affect the antibodies. PCR tests have been developed that can detect as little as one viral genome among the DNA of over 50,000 host cells . Infections can be detected earlier, donated blood can be screened directly for the virus, newborns can be immediately tested for infection, and the effects of antiviral treatments can be quantified.
Some disease organisms, such as that for Tuberculosis, are difficult to sample from patients and slow to be grown in the laboratory. PCR-based tests have allowed detection of small numbers of disease organisms (both live or dead), in convenient samples. Detailed genetic analysis can also be used to detect antibiotic resistance, allowing immediate and effective therapy. The effects of therapy can also be immediately evaluated.
The spread of a disease organism through populations of domestic or wild animals can be monitored by PCR testing. In many cases, the appearance of new virulent sub-types can be detected and monitored. The sub-types of an organism that were responsible for earlier epidemics can also be determined by PCR analysis.
Forensic applications
The development of PCR-based genetic (or DNA) fingerprinting protocols has seen widespread application in forensics:
In its most discriminating form, Genetic fingerprinting can uniquely discriminate any one person from the entire population of the world. Minute samples of DNA can be isolated from a crime scene, and compared to that from suspects, or from a DNA database of earlier evidence or convicts. Simpler versions of these tests are often used to rapidly rule out suspects during a criminal investigation. Evidence from decades-old crimes can be tested, confirming or exonerating the people originally convicted.
Less discriminating forms of DNA fingerprinting can help in Parental testing, where an individual is matched with their close relatives. DNA from unidentified human remains can be tested, and compared with that from possible parents, siblings, or children. Similar testing can be used to confirm the biological parents of an adopted (or kidnapped) child. The actual biological father of a newborn can also be confirmed (or ruled out).
[edit]Research applications
PCR has been applied to many areas of research in molecular genetics:
PCR allows rapid production of short pieces of DNA, even when nothing more than the sequence of the two primers is known. This ability of PCR augments many methods, such as generating hybridization probes for Southern or northern blot hybridization. PCR supplies these techniques with large amounts of pure DNA, sometimes as a single strand, enabling analysis even from very small amounts of starting material.
The task of DNA sequencing can also be assisted by PCR. Known segments of DNA can easily be produced from a patient with a genetic disease mutation. Modifications to the amplification technique can extract segments from a completely unknown genome, or can generate just a single strand of an area of interest.
PCR has numerous applications to the more traditional process of DNA cloning. It can extract segments for insertion into a vector from a larger genome, which may be only available in small quantities. Using a single set of 'vector primers', it can also analyze or extract fragments that have already been inserted into vectors. Some alterations to the PCR protocol can generate mutations (general or site-directed) of an inserted fragment.
Sequence-tagged sites is a process where PCR is used as an indicator that a particular segment of a genome is present in a particular clone. The Human Genome Project found this application vital to mapping the cosmid clones they were sequencing, and to coordinating the results from different laboratories.
An exciting application of PCR is the phylogenic analysis of DNA from ancient sources, such as that found in the recovered bones of Neanderthals, or from frozen tissues of Mammoths. In some cases the highly degraded DNA from these sources might be reassembled during the early stages of amplification.
A common application of PCR is the study of patterns of gene expression. Tissues (or even individual cells) can be analyzed at different stages to see which genes have become active, or which have been switched off. This application can also use Q-PCR to quantitate the actual levels of expression.
The ability of PCR to simultaneously amplify several loci from individual sperm has greatly enhanced the more traditional task of genetic mapping by studying chromosomal crossovers after meiosis. Rare crossover events between very close loci have been directly observed by analyzing thousands of individual sperms. Similarly, unusual deletions, insertions, translocations, or inversions can be analyzed, all without having to wait (or pay for) the long and laborious processes of fertilization, embryogenesis, etc.
Thursday, October 9, 2008
Wednesday, October 8, 2008
Tuesday, October 7, 2008
Non-invasive Prenatal Diagnosis using cell-free Fetal DNA
The holy grail of prenatal diagnosis has been the identification of chromosome and single gene abnormalities through maternal blood sampling. This would allow safe accurate prenatal diagnosis, requiring much lower operator skills, and automation is potentially possible, making it cost-effective. In contrast, standard prenatal screening involves ultrasound and biochemical risk assessment followed by invasive prenatal diagnosis by chorionic villus sampling (CVS), amniocentesis or fetal blood sampling - all requiring clinical expertise to perform and a variable risk of fetal loss.
The most common call is consistently from parents wrestling with the decision about whether to have an invasive test such as chorionic villus sampling (CVS) or amniocentesis. Because both procedures carry a one per cent risk of miscarriage, parents agonise over whether to put their pregnancy at risk in order to have conclusive information on a genetic condition. If cffDNA testing were to provide risk-free but reliable diagnoses of aneuploidies and other genetic conditions it would prove extremely popular with many parents.For most parents the earlier reassurance that cffDNA testing would bring will be welcome. However, we must avoid making assumptions that an earlier diagnosis will necessarily be easier for parents to cope with. Making painful decisions about the future of what is most often a wanted pregnancy is difficult at any gestation. Furthermore, there is no evidence that earlier terminations for fetal abnormality have substantially less emotional impact on women and couples than those carried out later in the pregnancy.
Another concern from the parental perspective is the form cffDNA testing takes, being a simple blood test. Women are very accustomed to having blood taken in pregnancy and while holding out an arm for a needle to be inserted is not always pleasant, it is something with which every pregnant woman is familiar. The 'routine' nature of the procedure could mean that some women embark on it without considering the possible implications and so are particularly distressed if test results bring unexpected news about the pregnancy. This has implications for how pre-test counselling and consent issues are handled.
In fact there is a precedent for a non-invasive diagnostic tool in routine use in antenatal care, namely ultrasound scanning. Every time an ultrasound probe is placed on the abdomen of a pregnant woman there is the possibility that an abnormality will be detected. Although information provision to women about the purpose of antenatal ultrasound is improving, we cannot underestimate the profound impact on parents when the scan shows that there is something wrong. However well-informed a woman may be, such news will always come as a shock and generate considerable anxiety and distress. This will also be the case for a diagnosis made from cffDNA testing, even if it comes earlier in pregnancy.
For decades, attempts to identify intact fetal cells in the maternal circulation have been unsuccessful - too few cells were present, and the few that were identified could remain in the circulation for years. Cell-free DNA is also present in the circulation and probably arises from apoptosis (controlled cell death) of cells. Fetal DNA arises from dying trophoblast cells and comprises 3-6 per cent of the total cell free DNA in the maternal circulation. FfDNA was first demonstrated in the maternal circulation in 1997, it consists of short fragments of DNA, not whole chromosomes. It can be first identified from the fourth week of gestation and increases throughout pregnancy. It is rapidly cleared from the maternal circulation after delivery and is undetectable by two hours. DNA is normally transcribed in to RNA and cell free RNA (ffRNA) also circulates in the maternal circulation. It is more stable than other forms of RNA. Only genes that are being transcribed will produce RNA and therefore identification of free fetal against free maternal RNA may be possible through differential expression patterns (ie. different patterns of maternal and fetal gene activity).
Identification of the ffDNA from the free maternal DNA is a major challenge. Fifty per cent of the genes in fetal DNA will be the same as in the maternal DNA, as they originate from the mother. Two clinical uses of ffDNA technologies are currently used frequently; rhesus typing and fetal sexing. Rhesus blood grouping of the fetus in rhesus negative mothers is used to try and prevent isoimmunisation of the fetus by using anti D antibodies in mothers carrying rhesus positive babies. Fetal sexing is offered to women who are either carriers of an X-linked disorder and who only need to have a CVS if they are carrying an at risk male, or women at a one in four risk of having an affected baby with congenital adrenal hyperplasia. In these pregnancies early maternal treatment with dexamethasone hopefully prevents the development of the distressing problem of clitoromegaly in affected girls.
However, the above two uses for ffDNA are only the very beginning for what is potentially possible with this technology. Screening for Down syndrome and other major trisomies (conditions caused by having three, rather than two copies of a particular chromosome) would transform prenatal diagnosis and screening. Diagnosis could be earlier and available to a much wider number of women. Single gene disorders can also be potentially identified using ffDNA. At present this is being studied in cases where the father is a carrier of an autosomal dominant disease - identification of the mutation has to be from ffDNA as the mother does not carry the mutation. If the father carries a different mutation in an autosomal recessive disease then this might also be possible to identify. Another potential use for ffDNA is where ultrasound abnormalities are identified and it may be possible to confirm a diagnosis using genetic tests and ffDNA. Examples of this include achondroplasia and thanatophoric dysplasia. In view of the limited volume of ffDNA available, it is only possible to look at specific well recognised mutations rather than screening a whole gene. FfRNA from genes that are only active in the placenta will allow wider applications of the technology, as there will be different patterns of gene activity from maternal ffRNA, and hence differentiating between the two should be easier.
Greater availability of risk free tests for prenatal diagnosis may sound ideal, but first it is necessary to confirm the reliability and accuracy of the test. Fetal sexing had an approximately four per cent error rate until recently. Fetal sexing can be confirmed using ultrasound at 16 weeks so the error can be rectified, but for tests with no ultrasound markers this will not be possible. In addition, not all women want prenatal diagnosis but all women have blood samples taken during pregnancy, so they may not realise what is being tested for and receive results that they are ill-prepared to receive. Biochemical screening has had some similar problems but as it is a screening test the woman then has a choice whether to proceed to a diagnostic test. Lastly there is the possibility of abusing the technology particularly for fetal sexing; this has happened in other modalities of prenatal diagnosis in both ultrasound and karyotyping. There is a possibility of ffDNA testing being available over the internet and therefore more difficult to control.
FfDNA technology thus has the potential to change the face of prenatal diagnosis, allowing safer and earlier diagnosis for a wide number of genetic diseases, and we look forward to these advances with anticipation and a degree of impatience.
The most common call is consistently from parents wrestling with the decision about whether to have an invasive test such as chorionic villus sampling (CVS) or amniocentesis. Because both procedures carry a one per cent risk of miscarriage, parents agonise over whether to put their pregnancy at risk in order to have conclusive information on a genetic condition. If cffDNA testing were to provide risk-free but reliable diagnoses of aneuploidies and other genetic conditions it would prove extremely popular with many parents.For most parents the earlier reassurance that cffDNA testing would bring will be welcome. However, we must avoid making assumptions that an earlier diagnosis will necessarily be easier for parents to cope with. Making painful decisions about the future of what is most often a wanted pregnancy is difficult at any gestation. Furthermore, there is no evidence that earlier terminations for fetal abnormality have substantially less emotional impact on women and couples than those carried out later in the pregnancy.
Another concern from the parental perspective is the form cffDNA testing takes, being a simple blood test. Women are very accustomed to having blood taken in pregnancy and while holding out an arm for a needle to be inserted is not always pleasant, it is something with which every pregnant woman is familiar. The 'routine' nature of the procedure could mean that some women embark on it without considering the possible implications and so are particularly distressed if test results bring unexpected news about the pregnancy. This has implications for how pre-test counselling and consent issues are handled.
In fact there is a precedent for a non-invasive diagnostic tool in routine use in antenatal care, namely ultrasound scanning. Every time an ultrasound probe is placed on the abdomen of a pregnant woman there is the possibility that an abnormality will be detected. Although information provision to women about the purpose of antenatal ultrasound is improving, we cannot underestimate the profound impact on parents when the scan shows that there is something wrong. However well-informed a woman may be, such news will always come as a shock and generate considerable anxiety and distress. This will also be the case for a diagnosis made from cffDNA testing, even if it comes earlier in pregnancy.
For decades, attempts to identify intact fetal cells in the maternal circulation have been unsuccessful - too few cells were present, and the few that were identified could remain in the circulation for years. Cell-free DNA is also present in the circulation and probably arises from apoptosis (controlled cell death) of cells. Fetal DNA arises from dying trophoblast cells and comprises 3-6 per cent of the total cell free DNA in the maternal circulation. FfDNA was first demonstrated in the maternal circulation in 1997, it consists of short fragments of DNA, not whole chromosomes. It can be first identified from the fourth week of gestation and increases throughout pregnancy. It is rapidly cleared from the maternal circulation after delivery and is undetectable by two hours. DNA is normally transcribed in to RNA and cell free RNA (ffRNA) also circulates in the maternal circulation. It is more stable than other forms of RNA. Only genes that are being transcribed will produce RNA and therefore identification of free fetal against free maternal RNA may be possible through differential expression patterns (ie. different patterns of maternal and fetal gene activity).
Identification of the ffDNA from the free maternal DNA is a major challenge. Fifty per cent of the genes in fetal DNA will be the same as in the maternal DNA, as they originate from the mother. Two clinical uses of ffDNA technologies are currently used frequently; rhesus typing and fetal sexing. Rhesus blood grouping of the fetus in rhesus negative mothers is used to try and prevent isoimmunisation of the fetus by using anti D antibodies in mothers carrying rhesus positive babies. Fetal sexing is offered to women who are either carriers of an X-linked disorder and who only need to have a CVS if they are carrying an at risk male, or women at a one in four risk of having an affected baby with congenital adrenal hyperplasia. In these pregnancies early maternal treatment with dexamethasone hopefully prevents the development of the distressing problem of clitoromegaly in affected girls.
However, the above two uses for ffDNA are only the very beginning for what is potentially possible with this technology. Screening for Down syndrome and other major trisomies (conditions caused by having three, rather than two copies of a particular chromosome) would transform prenatal diagnosis and screening. Diagnosis could be earlier and available to a much wider number of women. Single gene disorders can also be potentially identified using ffDNA. At present this is being studied in cases where the father is a carrier of an autosomal dominant disease - identification of the mutation has to be from ffDNA as the mother does not carry the mutation. If the father carries a different mutation in an autosomal recessive disease then this might also be possible to identify. Another potential use for ffDNA is where ultrasound abnormalities are identified and it may be possible to confirm a diagnosis using genetic tests and ffDNA. Examples of this include achondroplasia and thanatophoric dysplasia. In view of the limited volume of ffDNA available, it is only possible to look at specific well recognised mutations rather than screening a whole gene. FfRNA from genes that are only active in the placenta will allow wider applications of the technology, as there will be different patterns of gene activity from maternal ffRNA, and hence differentiating between the two should be easier.
Greater availability of risk free tests for prenatal diagnosis may sound ideal, but first it is necessary to confirm the reliability and accuracy of the test. Fetal sexing had an approximately four per cent error rate until recently. Fetal sexing can be confirmed using ultrasound at 16 weeks so the error can be rectified, but for tests with no ultrasound markers this will not be possible. In addition, not all women want prenatal diagnosis but all women have blood samples taken during pregnancy, so they may not realise what is being tested for and receive results that they are ill-prepared to receive. Biochemical screening has had some similar problems but as it is a screening test the woman then has a choice whether to proceed to a diagnostic test. Lastly there is the possibility of abusing the technology particularly for fetal sexing; this has happened in other modalities of prenatal diagnosis in both ultrasound and karyotyping. There is a possibility of ffDNA testing being available over the internet and therefore more difficult to control.
FfDNA technology thus has the potential to change the face of prenatal diagnosis, allowing safer and earlier diagnosis for a wide number of genetic diseases, and we look forward to these advances with anticipation and a degree of impatience.
Monday, October 6, 2008
Sunday, October 5, 2008
Saturday, October 4, 2008
Malaria Prophylaxis
Every year more than 125 million people visit over 100 countries endemic for Malaria. Each year up to 30,000 travelers are estimated to contract Malaria and late or wrong Malaria diagnosis in their home country may make things worse for them. Fever occurring in a traveler within three months of leaving a Malaria-endemic area is considered a medical emergency and should be investigated urgently. Malaria is contracted by the bite of a female anopheles mosquito. It is not contagious, and cannot be transmitted from person to person.
Malaria prophylaxis is the prevention of Malaria. Malaria is thought to be one of the oldest infectious diseases, evolving around 10,000 years ago. The development of new antimalarial drugs spurred the World Health Organization in 1955 to attempt a global Malaria eradication program. This was successful in much of Brazil, the US and Egypt but ultimately failed elsewhere. Efforts to control Malaria are still continuing.
As there is no vaccine available for protection against Malaria despite decades of research, there is a need for an alternative method that offers a fairly reliable protection against Malaria. And as Malaria can be severe in the non-immune, all visitors from non-malarious area to a malarious area should be protected. Antimalarial drugs offer protection against clinical attacks of Malaria.
The risk of contracting Malaria depends on the region visited, the length of stay, time of visit, type of activity, protection against mosquito bites, compliance with chemoprophylaxis etc.
Risk for Travelers
Risk can differ substantially even for persons who travel or reside temporarily in the same general areas within a country. For example, travelers staying in air-conditioned hotels may be at lower risk than backpackers or adventure travelers.
Basic Prevention
The ABCD of Malaria prevention are:
A. Awareness of risk;
B. Bite prevention – Travelers to Malarious areas are advised to wear long clothes that cover as much of the skin as possible. Exposed parts of the body should be treated with insect repellent. When sleeping, insecticide-impregnated bed nets should be used.
C. Chemoprophylaxis
D. Rapid Diagnosis and Treatment
Suppressive Prophylaxis
Chloroquine, Proguanil, Mefloquine and Doxycycline are suppressive prophylactics. This means that they are only effective at killing the Malaria parasite once it has entered the erythrocytic stage (blood stage) of its life cycle, and therefore have no effect until the liver stage is complete. That is why these prophylactics must be continued to be taken for four weeks after leaving the area of risk.
Causal Prophylaxis
Causal prophylactics target not only the blood stages of Malaria, but the initial liver stage as well. This means that the user can stop taking the drug seven days after leaving the area of risk. Malarone and Primaquine are the only causal prophylactics in current use.
Chemoprophylaxis
Chemoprophylaxis is the strategy that uses medications before, during, and after the exposure period to prevent the disease caused by Malaria parasites. The aims of Malaria treatment in broad terms are to alleviate symptoms, to prevent relapses and to prevent further transmission of the parasite. There are approximately 14 antimalarials that are advised for use in the prevention and treatment of uncomplicated Malaria.
Drug Regimens
The following regimens are recommended by the WHO, UK HPA and CDC:
1. Chloroquine 300 to 310 mg once weekly, and Proguanil 200 mg once daily (started one week before travel, and continued for four weeks after returning);
2. Doxycycline 100 mg once daily (started on day before travel, and continued for four weeks after returning);
3. Mefloquine 228 to 250 mg once a week (started two-and-a-half weeks before travel, and continued for four weeks after returning);
4. Malarone (Atavaquone + Proguanil) 1 tablet daily (started one day before travel, and continued for one week after returning).
Doses depend on what is available (eg in the US, Mefloquine tablets contain 228 mg base, but in the UK they contain 250 mg base). The data is constantly changing and no general advice is possible. Doses given above are appropriate for adults and children over 12 years of age.
Chloroquine, Mefloquine are safe in pregnancy, Doxycycline is not.
While chemoprophylaxis in pregnancy appears efficacious, a major question remains – which agents are safest for both the woman and the fetus? Some drugs routinely used in non-pregnant individuals should not be offered to pregnant women because of known direct effects on the fetus. Doxycycline is teratogenic, and Primaquine poses a significant of fatal intravascular hemolysis in G6PD deficient fetuses. Other drugs, such as Atovaquone / Proguanil and Artesunate, are not well studied in pregnancy, and therefore are not recommended for use unless other options are not available.
Given these reaction profiles, Chloroquine or Mefloquine are usually the best choice with their superior safety and efficacy.
*Chloroquine is widely used because it is inexpensive and well tolerated, with only pruritus, mouth ulcers and gastrointestinal upset as the most common adverse effects. Persons who experience uncomfortable side effects after taking Chloroquine may tolerate the drug better by taking it with meals.
*Mefloquine is usually well tolerated, but can cause dose-related neuropsychiatric effects; it is contraindicate in those with a history of epilepsy or psychiatric disease.
The World Health Organization (WHO) recommends Chloroquine as first-line prophylaxis in pregnancy (plus Proguanil if the region exhibits emerging Chloroquine resistance). In areas with proven Chloroquine resistance, Mefloquine is the drug of choice.
The Centers for Disease Control and Prevention (CDC) also advises use of Chloroquine (or Mefloquine in regions with Chloroquine resistance). The CDC discourages the use of Atovaquone/Proguanil, Doxycycline, and Primaquine, due to known adverse fetal effects or inadequate experience in pregnancy.
Chemoprophylaxis Regimen: Malaria chemoprophylaxis with Mefloquine or Chloroquine should begin 1-2 weeks before travel to malarious areas. Beginning the drug before travel allows the antimalarial agent to be in the blood before the traveler is exposed to malaria parasites. In addition to assuring adequate blood levels of the drug, this regimen allows for evaluation of any potential side effects. Chemoprophylaxis should continue during the stay in Malarious area and for 1-4 weeks after departure from the area. Chemoprophylaxis can be started earlier if there are particular concerns about tolerating one of the medications. Starting the medication 3-4 weeks in advance allows potential adverse events to occur before travel. If unacceptable side effects develop, there would be time to change the medication before the traveler’s departure.
Antimalarials and Pregnancy: CDC Recommendations
Travel during Pregnancy to Areas without Chloroquine-Resistant P falciparum: Pregnant women traveling to areas where chloroquine-resistant P falciparum has not been reported may take chloroquine prophylaxis. Chloroquine has not been found to have any harmful effects on the fetus when used in the recommended doses for Malaria prophylaxis; therefore, pregnancy is not a contraindication for Malaria prophylaxis with chloroquine phosphate or hydroxychloroquine sulfate.
Travel during Pregnancy to Areas with Chloroquine-Resistant P falciparum: Mefloquine is currently the only medication recommended for malaria chemoprophylaxis during pregnancy. A review of Mefloquine use in pregnancy from clinical trials and reports of inadvertent use of Mefloquine during pregnancy suggest that its use at prophylactic doses during the second and third trimesters of pregnancy is not associated with adverse fetal or pregnancy outcomes. More limited data suggest it is also safe to use during the first trimester.
Because of insufficient data regarding the use during pregnancy, atovaquone/proguanil is not currently recommended for the prevention of Malaria in pregnant women. Doxycycline is contraindicated for Malaria prophylaxis during pregnancy because of the risk of adverse effects of tetracycline, a related drug, on the fetus, which include discoloration and dysplasia of the teeth and inhibition of bone growth. Primaquine should not be used during pregnancy because the drug may be passed transplacentally to a glucose-6-phosphate dehydrogenase (G6PD)-deficient fetus and cause hemolytic anemia in utero.
How to protect yourself
Know the Facts
Persons who are traveling to malaria risk areas can almost always prevent this potentially deadly disease if they correctly take an effective antimalarial drug and follow measures to prevent mosquito bites.
Know the Symptoms
Despite these protective measures, travelers may become infected with malaria. Malaria symptoms can include:
• fever
• chills
• headache
• flu-like symptoms
• muscle aches
• fatigue
• low blood cell counts (anemia)
• yellowing of the skin and whites of the eye (jaundice)
When Symptoms Appear, Seek Immediate Medical Attention
Malaria is always a serious disease and may be a deadly illness. Travelers who become ill with a fever or flu-like illness either while traveling in a malaria-risk area or after returning home (for up to 1 year) should seek immediate medical attention and should tell the physician their travel history.
Personal Protection Measures
It must be remembered that no chemoprophylaxis regime provides 100% protection. Therefore it is essential to prevent mosquito bites as well as to comply with chemoprophylaxis. Anopheles mosquitoes bite at nights, with peak biting between 10pm and 4am and Malaria transmission occurs at these hours. Travelers must take personal protective measures against mosquito bites at nights.
• Remaining in well-screened areas after dusk, using mosquito nets, and wearing clothes that cover most of the body are some simple but effective measures.
• In addition, mosquito repellents like N,N diethylmetatoluamide (DEET) can be used. It is better to have a pyrethrum-containing space spray to use in living and sleeping areas during evening and night hours. Travelers should take a flying insect spray on their trip to help clear rooms of mosquitoes. In the United States, permethrin (Permanone) is available as a liquid or spray. Overseas, either permethrin or another insecticide, deltamethrin, is available and may be sprayed on bed nets and clothing for additional protection against mosquitoes.
• Protect infants (especially infants under 2 months of age not wearing insect repellent) by using a carrier draped with mosquito netting with an elastic edge for a tight fit.
• Clothing, shoes, and camping gear, can also be treated with permethrin. Treated clothing can be repeatedly washed and still repel insects. Some commercial products (clothing) are now available in the United States that have been pretreated with permethrin.
• It is advisable to quickly report any febrile illness and disclose your travel histories to your healthcare providers.
Know the Signs and Symptoms of Malaria
You can still get malaria despite taking an antimalarial drug and using protection against mosquito bites. Taking an antimalarial drug greatly reduces your chances of getting malaria. Symptoms are very flu-like and can include fever, shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhea may also occur.
Malaria symptoms will occur at least six to nine days after being bitten by an infected mosquito. Therefore, fever in the first week of travel in a malaria-risk area is unlikely to be malaria; however, ill travelers should still seek immediate medical care and any fever should be promptly evaluated.
Recommendations for travelers to malaria endemic areas
All travelers to malaria-endemic areas are at risk of contracting Malaria and being non-immune, P falciparum infection in these individuals can become severe. Therefore, all travelers to Malaria endemic areas are advised to use an appropriate chemoprophylaxis and personal protection measures to prevent Malaria. However, it should be remembered that, regardless of methods employed, Malaria can still be contracted. Symptoms can develop as early as 8 days after initial exposure in a Malarious area and as late as several months after departure from a Malarious area. Malaria is easily treatable early in the course of the disease but delay in treatment can lead to serious or even fatal consequences. Therefore, individuals who develop symptoms of malaria should seek prompt medical help, including blood smear (or QBC test) for malaria.
Dr Sulbha Arora MD DNB
Scientific Director
Deccan Fertility Clinic and Keyhole Surgery Center
Malaria prophylaxis is the prevention of Malaria. Malaria is thought to be one of the oldest infectious diseases, evolving around 10,000 years ago. The development of new antimalarial drugs spurred the World Health Organization in 1955 to attempt a global Malaria eradication program. This was successful in much of Brazil, the US and Egypt but ultimately failed elsewhere. Efforts to control Malaria are still continuing.
As there is no vaccine available for protection against Malaria despite decades of research, there is a need for an alternative method that offers a fairly reliable protection against Malaria. And as Malaria can be severe in the non-immune, all visitors from non-malarious area to a malarious area should be protected. Antimalarial drugs offer protection against clinical attacks of Malaria.
The risk of contracting Malaria depends on the region visited, the length of stay, time of visit, type of activity, protection against mosquito bites, compliance with chemoprophylaxis etc.
Risk for Travelers
Risk can differ substantially even for persons who travel or reside temporarily in the same general areas within a country. For example, travelers staying in air-conditioned hotels may be at lower risk than backpackers or adventure travelers.
Basic Prevention
The ABCD of Malaria prevention are:
A. Awareness of risk;
B. Bite prevention – Travelers to Malarious areas are advised to wear long clothes that cover as much of the skin as possible. Exposed parts of the body should be treated with insect repellent. When sleeping, insecticide-impregnated bed nets should be used.
C. Chemoprophylaxis
D. Rapid Diagnosis and Treatment
Suppressive Prophylaxis
Chloroquine, Proguanil, Mefloquine and Doxycycline are suppressive prophylactics. This means that they are only effective at killing the Malaria parasite once it has entered the erythrocytic stage (blood stage) of its life cycle, and therefore have no effect until the liver stage is complete. That is why these prophylactics must be continued to be taken for four weeks after leaving the area of risk.
Causal Prophylaxis
Causal prophylactics target not only the blood stages of Malaria, but the initial liver stage as well. This means that the user can stop taking the drug seven days after leaving the area of risk. Malarone and Primaquine are the only causal prophylactics in current use.
Chemoprophylaxis
Chemoprophylaxis is the strategy that uses medications before, during, and after the exposure period to prevent the disease caused by Malaria parasites. The aims of Malaria treatment in broad terms are to alleviate symptoms, to prevent relapses and to prevent further transmission of the parasite. There are approximately 14 antimalarials that are advised for use in the prevention and treatment of uncomplicated Malaria.
Drug Regimens
The following regimens are recommended by the WHO, UK HPA and CDC:
1. Chloroquine 300 to 310 mg once weekly, and Proguanil 200 mg once daily (started one week before travel, and continued for four weeks after returning);
2. Doxycycline 100 mg once daily (started on day before travel, and continued for four weeks after returning);
3. Mefloquine 228 to 250 mg once a week (started two-and-a-half weeks before travel, and continued for four weeks after returning);
4. Malarone (Atavaquone + Proguanil) 1 tablet daily (started one day before travel, and continued for one week after returning).
Doses depend on what is available (eg in the US, Mefloquine tablets contain 228 mg base, but in the UK they contain 250 mg base). The data is constantly changing and no general advice is possible. Doses given above are appropriate for adults and children over 12 years of age.
Chloroquine, Mefloquine are safe in pregnancy, Doxycycline is not.
While chemoprophylaxis in pregnancy appears efficacious, a major question remains – which agents are safest for both the woman and the fetus? Some drugs routinely used in non-pregnant individuals should not be offered to pregnant women because of known direct effects on the fetus. Doxycycline is teratogenic, and Primaquine poses a significant of fatal intravascular hemolysis in G6PD deficient fetuses. Other drugs, such as Atovaquone / Proguanil and Artesunate, are not well studied in pregnancy, and therefore are not recommended for use unless other options are not available.
Given these reaction profiles, Chloroquine or Mefloquine are usually the best choice with their superior safety and efficacy.
*Chloroquine is widely used because it is inexpensive and well tolerated, with only pruritus, mouth ulcers and gastrointestinal upset as the most common adverse effects. Persons who experience uncomfortable side effects after taking Chloroquine may tolerate the drug better by taking it with meals.
*Mefloquine is usually well tolerated, but can cause dose-related neuropsychiatric effects; it is contraindicate in those with a history of epilepsy or psychiatric disease.
The World Health Organization (WHO) recommends Chloroquine as first-line prophylaxis in pregnancy (plus Proguanil if the region exhibits emerging Chloroquine resistance). In areas with proven Chloroquine resistance, Mefloquine is the drug of choice.
The Centers for Disease Control and Prevention (CDC) also advises use of Chloroquine (or Mefloquine in regions with Chloroquine resistance). The CDC discourages the use of Atovaquone/Proguanil, Doxycycline, and Primaquine, due to known adverse fetal effects or inadequate experience in pregnancy.
Chemoprophylaxis Regimen: Malaria chemoprophylaxis with Mefloquine or Chloroquine should begin 1-2 weeks before travel to malarious areas. Beginning the drug before travel allows the antimalarial agent to be in the blood before the traveler is exposed to malaria parasites. In addition to assuring adequate blood levels of the drug, this regimen allows for evaluation of any potential side effects. Chemoprophylaxis should continue during the stay in Malarious area and for 1-4 weeks after departure from the area. Chemoprophylaxis can be started earlier if there are particular concerns about tolerating one of the medications. Starting the medication 3-4 weeks in advance allows potential adverse events to occur before travel. If unacceptable side effects develop, there would be time to change the medication before the traveler’s departure.
Antimalarials and Pregnancy: CDC Recommendations
Travel during Pregnancy to Areas without Chloroquine-Resistant P falciparum: Pregnant women traveling to areas where chloroquine-resistant P falciparum has not been reported may take chloroquine prophylaxis. Chloroquine has not been found to have any harmful effects on the fetus when used in the recommended doses for Malaria prophylaxis; therefore, pregnancy is not a contraindication for Malaria prophylaxis with chloroquine phosphate or hydroxychloroquine sulfate.
Travel during Pregnancy to Areas with Chloroquine-Resistant P falciparum: Mefloquine is currently the only medication recommended for malaria chemoprophylaxis during pregnancy. A review of Mefloquine use in pregnancy from clinical trials and reports of inadvertent use of Mefloquine during pregnancy suggest that its use at prophylactic doses during the second and third trimesters of pregnancy is not associated with adverse fetal or pregnancy outcomes. More limited data suggest it is also safe to use during the first trimester.
Because of insufficient data regarding the use during pregnancy, atovaquone/proguanil is not currently recommended for the prevention of Malaria in pregnant women. Doxycycline is contraindicated for Malaria prophylaxis during pregnancy because of the risk of adverse effects of tetracycline, a related drug, on the fetus, which include discoloration and dysplasia of the teeth and inhibition of bone growth. Primaquine should not be used during pregnancy because the drug may be passed transplacentally to a glucose-6-phosphate dehydrogenase (G6PD)-deficient fetus and cause hemolytic anemia in utero.
How to protect yourself
Know the Facts
Persons who are traveling to malaria risk areas can almost always prevent this potentially deadly disease if they correctly take an effective antimalarial drug and follow measures to prevent mosquito bites.
Know the Symptoms
Despite these protective measures, travelers may become infected with malaria. Malaria symptoms can include:
• fever
• chills
• headache
• flu-like symptoms
• muscle aches
• fatigue
• low blood cell counts (anemia)
• yellowing of the skin and whites of the eye (jaundice)
When Symptoms Appear, Seek Immediate Medical Attention
Malaria is always a serious disease and may be a deadly illness. Travelers who become ill with a fever or flu-like illness either while traveling in a malaria-risk area or after returning home (for up to 1 year) should seek immediate medical attention and should tell the physician their travel history.
Personal Protection Measures
It must be remembered that no chemoprophylaxis regime provides 100% protection. Therefore it is essential to prevent mosquito bites as well as to comply with chemoprophylaxis. Anopheles mosquitoes bite at nights, with peak biting between 10pm and 4am and Malaria transmission occurs at these hours. Travelers must take personal protective measures against mosquito bites at nights.
• Remaining in well-screened areas after dusk, using mosquito nets, and wearing clothes that cover most of the body are some simple but effective measures.
• In addition, mosquito repellents like N,N diethylmetatoluamide (DEET) can be used. It is better to have a pyrethrum-containing space spray to use in living and sleeping areas during evening and night hours. Travelers should take a flying insect spray on their trip to help clear rooms of mosquitoes. In the United States, permethrin (Permanone) is available as a liquid or spray. Overseas, either permethrin or another insecticide, deltamethrin, is available and may be sprayed on bed nets and clothing for additional protection against mosquitoes.
• Protect infants (especially infants under 2 months of age not wearing insect repellent) by using a carrier draped with mosquito netting with an elastic edge for a tight fit.
• Clothing, shoes, and camping gear, can also be treated with permethrin. Treated clothing can be repeatedly washed and still repel insects. Some commercial products (clothing) are now available in the United States that have been pretreated with permethrin.
• It is advisable to quickly report any febrile illness and disclose your travel histories to your healthcare providers.
Know the Signs and Symptoms of Malaria
You can still get malaria despite taking an antimalarial drug and using protection against mosquito bites. Taking an antimalarial drug greatly reduces your chances of getting malaria. Symptoms are very flu-like and can include fever, shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting, and diarrhea may also occur.
Malaria symptoms will occur at least six to nine days after being bitten by an infected mosquito. Therefore, fever in the first week of travel in a malaria-risk area is unlikely to be malaria; however, ill travelers should still seek immediate medical care and any fever should be promptly evaluated.
Recommendations for travelers to malaria endemic areas
All travelers to malaria-endemic areas are at risk of contracting Malaria and being non-immune, P falciparum infection in these individuals can become severe. Therefore, all travelers to Malaria endemic areas are advised to use an appropriate chemoprophylaxis and personal protection measures to prevent Malaria. However, it should be remembered that, regardless of methods employed, Malaria can still be contracted. Symptoms can develop as early as 8 days after initial exposure in a Malarious area and as late as several months after departure from a Malarious area. Malaria is easily treatable early in the course of the disease but delay in treatment can lead to serious or even fatal consequences. Therefore, individuals who develop symptoms of malaria should seek prompt medical help, including blood smear (or QBC test) for malaria.
Dr Sulbha Arora MD DNB
Scientific Director
Deccan Fertility Clinic and Keyhole Surgery Center
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