Toxoplasmosis Health Dictionary

Acquired Immune De?ciency Syndrome (AIDS) is the clinical manifestation of infection with Human Immunode?ciency Virus (HIV). HIV belongs to the retroviruses, which in turn belong to the lentiviruses (characterised by slow onset of disease). There are two main HIV strains: HIV-1, by far the commonest; and HIV-2, which is prevalent in Western Africa (including Ivory Coast, Gambia, Mali, Nigeria and Sierra Leone). HIV attacks the human immune system (see IMMUNITY) so that the infected person becomes susceptible to opportunistic infections, such as TUBERCULOSIS, PNEUMONIA, DIARRHOEA, MENINGITIS and tumours such as KAPOSI’S SARCOMA. AIDS is thus the disease syndrome associated with advanced HIV infection.

Both HIV-1 and HIV-2 are predominantly sexually transmitted and both are associated with secondary opportunistic infections. However, HIV-2 seems to result in slower damage to the immune system. HIV-1 is known to mutate rapidly and has given rise to other subtypes.

HIV is thought to have occurred in humans in the 1950s, but whether or not it infected humans from another primate species is uncertain. It became widespread in the 1970s but its latency in causing symptoms meant that the epidemic was not noticed until the following decade. Although it is a sexually transmitted disease, it can also be transmitted by intravenous drug use (through sharing an infected needle), blood transfusions with infected blood (hence the importance of e?ective national blood-screening programmes), organ donation, and occupationally (see health-care workers, below). Babies born of HIV-positive mothers can be infected before or during birth, or through breast feeding.

Although HIV is most likely to occur in blood, semen or vaginal ?uid, it has been found in saliva and tears (but not sweat); however, there is no evidence that the virus can be transmitted from these two body ?uids. There is also no evidence that HIV can be transmitted by biting insects (such as mosquitoes). HIV does not survive well in the environment and is rapidly destroyed through drying.

Prevalence At the end of 2003 an estimated 42 million people globally were infected with HIV – up from 40 million two years earlier. About one-third of those with HIV/AIDS are aged 15–24 and most are unaware that they are carrying the virus. During 2003 it is estimated that 5 million adults and children worldwide were newly infected with HIV, and that 3 million adults and children died. In Africa in 2003,

3.4 million people were newly infected and 2.3 million died, with more than 28 million carrying the virus. HIV/AIDS was the leading cause of death in sub-Saharan Africa where over half of the infections were in women and 90 per cent of cases resulted from heterosexual sex. In some southern African countries, one in three pregnant women had HIV.

In Asia and the Paci?c there were 1.2 million new infections and 435,000 deaths. The area with the fastest-growing epidemic is Eastern Europe, especially the Russian Federation where in 2002 around a million people had HIV and there were an estimated 250,000 new infections, with intravenous drug use a key contributor to this ?gure. Seventy-?ve per cent of cases occurred in men, with male-to-male sexual transmission an important cause of infection, though heterosexual activity is a rising cause of infection.

At the end of 2002 the UK had an estimated 55,900 HIV-infected adults aged between 15 and 59. More than 3,600 individuals were newly diagnosed with the infection in 2000, the highest annual ?gure since the epidemic started

– in 1998 the ?gure was 2,817 and in 1999 just over 3,000 (Department of Health and Communicable Disease Surveillance Centre). The incidence of AIDS in the UK has declined sharply since the introduction of highly active antiretroviral therapy (HAART) and HIV-related deaths have also fallen: in 2002 there were 777 reported new AIDS cases and 395 deaths, compared with 1,769 and 1,719 respectively in 1995. (Sources: UNAIDS and WHO, AIDS Epidemic Update, December 2001; Public Health Laboratory Services AIDS and STD Centre Communicable Disease Surveillance and Scottish Centre for Infection and Environmental Health, Quarterly Surveillance Tables.)

Poverty is strongly linked to the spread of AIDS, for various reasons including lack of health education; lack of e?ective public-health awareness; women having little control over sexual behaviour and contraception; and, by comparison with the developed world, little or no access to antiretroviral drugs.

Pathogenesis The cellular target of HIV infection is a subset of white blood cells called T-lymphocytes (see LYMPHOCYTE) which carry the CD4 surface receptor. These so-called ‘helper T-cells’ are vital to the function of cell-mediated immunity. Infection of these cells leads to their destruction (HIV replicates at an enormous rate – 109) and over the course of several years the body is unable to generate suf?cient new cells to keep pace. This leads to progressive destruction of the body’s immune capabilities, evidenced clinically by the development of opportunistic infection and unusual tumours.

Monitoring of clinical progression It is possible to measure the number of viral particles present in the plasma. This gives an accurate guide to the likely progression rate, which will be slow in those individuals with fewer than 10,000 particles per ml of plasma but progressively more rapid above this ?gure. The main clinical monitoring of the immune system is through the numbers of CD4 lymphocytes in the blood. The normal count is around 850 cells per ml and, without treatment, eventual progression to AIDS is likely in those individuals whose CD4 count falls below 500 per ml. Opportunistic infections occur most frequently when the count falls below 200 per ml: most such infections are treatable, and death is only likely when the CD4 count falls below 50 cells per ml when infection is developed with organisms that are di?cult to treat because of their low intrinsic virulence.

Simple, cheap and highly accurate tests are available to detect HIV antibodies in the serum. These normally occur within three months of infection and remain the cornerstone of the diagnosis.

Clinical features Most infected individuals have a viral illness some three weeks after contact with HIV. The clinical features are often non-speci?c and remain undiagnosed but include a ?ne red rash, large lymph nodes, an in?uenza-like illness, cerebral involvement and sometimes the development of opportunistic infections. The antibody test may be negative at this stage but there are usually high levels of virus particles in the blood. The antibody test is virtually always positive within three months of infection. HIV infection is often subsequently asymptomatic for a period of ten years or more, although in most patients progressive immune destruction is occurring during this time and a variety of minor opportunistic infections such as HERPES ZOSTER or oral thrush (see CANDIDA) do occur. In addition, generalised LYMPHADENOPATHY is present in a third of patients and some suffer from severe malaise, weight loss, night sweats, mild fever, ANAEMIA or easy bruising due to THROMBOCYTOPENIA.

The presentation of opportunistic infection is highly variable but usually involves either the CENTRAL NERVOUS SYSTEM, the gastrointestinal tract or the LUNGS. Patients may present with a sudden onset of a neurological de?cit or EPILEPSY due to a sudden onset of a STROKE-like syndrome, or epilepsy due to a space-occupying lesion in the brain – most commonly TOXOPLASMOSIS. In late disease, HIV infection of the central nervous system itself may produce progressive memory loss, impaired concentration and mental slowness called AIDS DEMENTIA. A wide variety of opportunistic PROTOZOA or viruses produces DYSPHAGIA, DIARRHOEA and wasting. In the respiratory system the commonest opportunistic infection associated with AIDS, pneumonia, produces severe shortness of breath and sometimes CYANOSIS, usually with a striking lack of clinical signs in the chest.

In very late HIV infection, when the CD4 count has fallen below 50 cells per ml, infection with CYTOMEGALOVIRUS may produce progressive retinal necrosis (see EYE, DISORDERS OF) which will lead to blindness if untreated, as well as a variety of gastrointestinal symptoms. At this stage, infection with atypical mycobacteria is also common, producing severe anaemia, wasting and fevers. The commonest tumour associated with HIV is Kaposi’s sarcoma which produces purplish skin lesions. This and nonHodgkin’s lymphoma (see LYMPHOMA), which is a hundred times more frequent among HIV-positive individuals than in the general population, are likely to be associated with or caused by opportunistic viral infections.

Prevention There is, as yet, no vaccine to prevent HIV infection. Vaccine development has been hampered

by the large number of new HIV strains generated through frequent mutation and recombination.

because HIV can be transmitted as free virus and in infected cells.

because HIV infects helper T-cells – the very cells involved in the immune response. There are, however, numerous research pro

grammes underway to develop vaccines that are either prophylactic or therapeutic. Vaccine-development strategies have included: recombinant-vector vaccines, in which a live bacterium or virus is genetically modi?ed to carry one or more of the HIV genes; subunit vaccines, consisting of small regions of the HIV genome designed to induce an immune response without infection; modi?ed live HIV, which has had its disease-promoting genes removed; and DNA vaccines – small loops of DNA (plasmids) containing viral genes – that make the host cells produce non-infectious viral proteins which, in turn, trigger an immune response and prime the immune system against future infection with real virus.

In the absence of an e?ective vaccine, preventing exposure remains the chief strategy in reducing the spread of HIV. Used properly, condoms are an extremely e?ective method of preventing exposure to HIV during sexual intercourse and remain the most important public-health approach to countering the further acceleration of the AIDS epidemic. The spermicide nonoxynol-9, which is often included with condoms, is known to kill HIV in vitro; however, its e?ectiveness in preventing HIV infection during intercourse is not known.

Public-health strategies must be focused on avoiding high-risk behaviour and, particularly in developing countries, empowering women to have more control over their lives, both economically and socially. In many of the poorer regions of the world, women are economically dependent on men and refusing sex, or insisting on condom use, even when they know their partners are HIV positive, is not a straightforward option. Poverty also forces many women into the sex industry where they are at greater risk of infection.

Cultural problems in gaining acceptance for universal condom-use by men in some developing countries suggests that other preventive strategies should also be considered. Microbicides used as vaginal sprays or ‘chemical condoms’ have the potential to give women more direct control over their exposure risk, and research is underway to develop suitable products.

Epidemiological studies suggest that male circumcision may o?er some protection against HIV infection, although more research is needed before this can be an established public-health strategy. Globally, about 70 per cent of infected men have acquired the virus through unprotected vaginal sex; in these men, infection is likely to have occurred through the penis with the mucosal epithelia of the inner surface of the foreskin and the frenulum considered the most likely sites for infection. It is suggested that in circumcised men, the glans may become keratinised and thus less likely to facilitate infection. Circumcision may also reduce the risk of lesions caused by other sexually transmitted disease.

Treatment AIDS/HIV treatment can be categorised as speci?c therapies for the individual opportunistic infections – which ultimately cause death – and highly active antiretroviral therapy (HAART) designed to reduce viral load and replication. HAART is also the most e?ective way of preventing opportunistic infections, and has had a signi?cant impact in delaying the onset of AIDS in HIV-positive individuals in developed countries.

Four classes of drugs are currently in use. Nucleoside analogues, including ZIDOVUDINE and DIDANOSINE, interfere with the activity of the unique enzyme of the retrovirus reverse transcriptase which is essential for replication. Nucleotide analogues, such as tenofovir, act in the same way but require no intracellular activation. Non-nucleoside reverse transcriptase inhibitors, such as nevirapine and EFAVIRENZ, act by a di?erent mechanism on the same enzyme. The most potent single agents against HIV are the protease inhibitors, such as lopinavir, which render a unique viral enzyme ineffective. These drugs are used in a variety of combinations in an attempt to reduce the plasma HIV viral load to below detectable limits, which is achieved in approximately 90 per cent of patients who have not previously received therapy. This usually also produces a profound rise in CD4 count. It is likely, however, that such treatments need to be lifelong – and since they are associated with toxicities, long-term adherence is di?cult. Thus the optimum time for treatment intervention remains controversial, with some clinicians believing that this should be governed by the viral load rising above 10,000 copies, and others that it should primarily be designed to prevent the development of opportunistic infections – thus, that initiation of therapy should be guided more by the CD4 count.

It should be noted that the drug regimens have been devised for infection with HIV-1; it is not known how e?ective they are at treating infection with HIV-2.

HIV and pregnancy An HIV-positive woman can transmit the virus to her fetus, with the risk of infection being particularly high during parturition; however, the risk of perinatal HIV transmission can be reduced by antiviral drug therapy. In the UK, HIV testing is available to all women as part of antenatal care. The bene?ts of antenatal HIV testing in countries where antiviral drugs are not available are questionable. An HIV-positive woman might be advised not to breast feed because of the risks of transmitting HIV via breastmilk, but there may be a greater risk associated with not breast feeding at all. Babies in many poor communities are thought to be at high risk of infectious diseases and malnutrition if they are not breast fed and may thus be at greater overall risk of death during infancy.

Counselling Con?dential counselling is an essential part of AIDS management, both in terms of supporting the psychological wellbeing of the individual and in dealing with issues such as family relations, sexual partners and implications for employment (e.g. for health-care workers). Counsellors must be particularly sensitive to culture and lifestyle issues. Counselling is essential both before an HIV test is taken and when the results are revealed.

Health-care workers Health-care workers may be at risk of occupational exposure to HIV, either through undertaking invasive procedures or through accidental exposure to infected blood from a contaminated needle (needlestick injury). Needlestick injuries are frequent in health care – as many as 600,000 to 800,000 are thought to occur annually in the United States. Transmission is much more likely where the worker has been exposed to HIV through a needlestick injury or deep cut with a contaminated instrument than through exposure of mucous membranes to contaminated blood or body ?uids. However, even where exposure occurs through a needlestick injury, the risk of seroconversion is much lower than with a similar exposure to hepatitis C or hepatitis B. A percutaneous exposure to HIV-infected blood in a health-care setting is thought to carry a risk of about one infection per 300 injuries (one in 1,000 for mucous-membrane exposure), compared with one in 30 for hepatitis C, and one in three for hepatitis B (when the source patient is e-antigen positive).

In the event of an injury, health-care workers are advised to report the incident immediately where, depending on a risk assessment, they may be o?ered post-exposure prophylaxis (PEP). They should also wash the contaminated area with soap and water (but without scrubbing) and, if appropriate, encourage bleeding at the site of injury. PEP, using a combination of antiretroviral drugs (in a similar regimen to HAART – see above), is thought to greatly reduce the chances of seroconversion; it should be commenced as soon as possible, preferably within one or two hours of the injury. Although PEP is available, safe systems of work are considered to o?er the greatest protection. Double-gloving (latex gloves remove much of the blood from the surface of the needle during a needlestick), correct use of sharps containers (for used needles and instruments), avoiding the resheathing of used needles, reduction in the number of blood samples taken from a patient, safer-needle devices (such as needles that self-blunt after use) and needleless drug administration are all thought to reduce the risk of exposure to HIV and other blood-borne viruses. Although there have been numerous cases of health-care workers developing HIV through occupational exposure, there is little evidence of health-care workers passing HIV to their patients through normal medical procedures.... aids/hiv

Nutritional Profile Energy value (calories per serving): Moderate Protein: High Fat: Moderate Saturated fat: High Cholesterol: Moderate Carbohydrates: None Fiber: None Sodium: Low Major vitamin contribution: B vitamins Major mineral contribution: Iron, phosphorus, zinc

About the Nutrients in This Food Like fish, pork, poultry, milk, and eggs, beef has high-quality proteins, with sufficient amounts of all the essential amino acids. Beef fat is slightly more highly saturated than pork fat, but less saturated than lamb fat. All have about the same amount of cholesterol per serving. Beef is an excellent source of B vitamins, including niacin, vitamin B6, and vitamin B12, which is found only in animal foods. Lean beef pro- vides heme iron, the organic iron that is about five times more useful to the body than nonheme iron, the inorganic form of iron found in plant foods. Beef is also an excellent source of zinc. One four-ounce serving of lean broiled sirloin steak has nine grams fat (3.5 g saturated fat), 101 mg cholesterol, 34 g protein, and 3.81 mg iron (21 percent of the R DA for a woman, 46 percent of the R DA for a man). One four-ounce serving of lean roast beef has 16 g fat (6.6 g saturated fat), 92 mg cholesterol, and 2.96 mg iron (16 percent of the R DA for a woman, 37 percent of the R DA for a man).

The Most Nutritious Way to Serve This Food With a food rich in vitamin C. Ascorbic acid increases the absorption of iron from meat. * These values apply to lean cooked beef.

Diets That May Restrict or Exclude This Food Controlled-fat, low-cholesterol diet Low-protein diet (for some forms of kidney disease)

Buying This Food Look for: Fresh, red beef. The fat should be white, not yellow. Choose lean cuts of beef with as little internal marbling (streaks of fat) as possible. The leanest cuts are flank steak and round steak; rib steaks, brisket, and chuck have the most fat. USDA grading, which is determined by the maturity of the animal and marbling in meat, is also a guide to fat content. U.S. prime has more marbling than U.S. choice, which has more marbling than U.S. good. All are equally nutritious; the difference is how tender they are, which depends on how much fat is present. Choose the cut of meat that is right for your recipe. Generally, the cuts from the cen- ter of the animal’s back—the rib, the T-Bone, the porterhouse steaks—are the most tender. They can be cooked by dry heat—broiling, roasting, pan-frying. Cuts from around the legs, the underbelly, and the neck—the shank, the brisket, the round—contain muscles used for movement. They must be tenderized by stewing or boiling, the long, moist cooking methods that break down the connective tissue that makes meat tough.

Storing This Food Refrigerate raw beef immediately, carefully wrapped to prevent its drippings from contami- nating other foods. Refrigeration prolongs the freshness of beef by slowing the natural multi- plication of bacteria on the meat surface. Unchecked, these bacteria will convert proteins and other substances on the surface of the meat to a slimy film and change meat’s sulfur-contain- ing amino acids methionine and cystine into smelly chemicals called mercaptans. When the mercaptans combine with myoglobin, they produce the greenish pigment that gives spoiled meat its characteristic unpleasant appearance. Fresh ground beef, with many surfaces where bacteria can live, should be used within 24 to 48 hours. Other cuts of beef may stay fresh in the refrigerator for three to five days.

Preparing This Food Trim the beef carefully. By judiciously cutting away all visible fat you can significantly reduce the amount of fat and cholesterol in each serving. When you are done, clean all utensils thoroughly with soap and hot water. Wash your cutting board, wood or plastic, with hot water, soap, and a bleach-and-water solution. For ultimate safety in preventing the transfer of microorganisms from the raw meat to other foods, keep one cutting board exclusively for raw meats, fish, and poultry, and a second one for everything else. Finally, don’t forget to wash your hands.

What Happens When You Cook This Food Cooking changes the appearance and flavor of beef, alters nutritional value, makes it safer, and extends its shelf life. Browning meat after you cook it does not “seal in the juices,” but it does change the fla- vor by caramelizing sugars on the surface. Because beef’s only sugars are the small amounts of glycogen in the muscles, we add sugars in marinades or basting liquids that may also con- tain acids (vinegar, lemon juice, wine) to break down muscle fibers and tenderize the meat. (Browning has one minor nutritional drawback. It breaks amino acids on the surface of the meat into smaller compounds that are no longer useful proteins.) When beef is cooked, it loses water and shrinks. Its pigments, which combine with oxygen, are denatured (broken into fragments) by the heat and turn brown, the natural color of well-done meat. At the same time, the fats in the beef are oxidized. Oxidized fats, whether formed in cooking or when the cooked meat is stored in the refrigerator, give cooked meat a character- istic warmed-over flavor. Cooking and storing meat under a blanket of antioxidants—catsup or a gravy made of tomatoes, peppers, and other vitamin C-rich vegetables—reduces the oxidation of fats and the intensity of warmed-over flavor. Meat reheated in a microwave oven also has less warmed-over flavor. An obvious nutritional benefit of cooking is the fact that heat lowers the fat content of beef by liquif ying the fat so it can run off the meat. One concrete example of how well this works comes from a comparison of the fat content in regular and extra-lean ground beef. According to research at the University of Missouri in 1985, both kinds of beef lose mass when cooked, but the lean beef loses water and the regular beef loses fat and cholesterol. Thus, while regular raw ground beef has about three times as much fat (by weight) as raw ground extra-lean beef, their fat varies by only 5 percent after broiling. To reduce the amount of fat in ground beef, heat the beef in a pan until it browns. Then put the beef in a colander, and pour one cup of warm water over the beef. Repeat with a second cup of warm water to rinse away fat melted by heating the beef. Use the ground beef in sauce and other dishes that do not require it to hold together. Finally, cooking makes beef safer by killing Salmonella and other organisms in the meat. As a result, cooking also serves as a natural preservative. According to the USDA, large pieces of fresh beef can be refrigerated for two or three days, then cooked and held safely for another day or two because the heat of cooking has reduced the number of bacteria on the surface of the meat and temporarily interrupted the natural cycle of deterioration.

How Other Kinds of Processing Affect This Food Aging. Hanging fresh meat exposed to the air, in a refrigerated room, reduces the moisture content and shrinks the meat slightly. As the meat ages enzymes break down muscle pro- teins, “tenderizing” the beef. Canning. Canned beef does not develop a warmed-over flavor because the high tempera- tures in canning food and the long cooking process alter proteins in the meat so that they act as antioxidants. Once the can is open, however, the meat should be protected from oxygen that will change the flavor of the beef. Curing. Salt-curing preserves meat through osmosis, the physical reaction in which liquids flow across a membrane, such as the wall of a cell, from a less dense to a more dense solution. The salt or sugar used in curing dissolves in the liquid on the surface of the meat to make a solution that is more dense than the liquid inside the cells of the meat. Water flows out of the meat and out of the cells of any microorganisms living on the meat, killing the microor- ganisms and protecting the meat from bacterial damage. Salt-cured meat is much higher in sodium than fresh meat. Freezing. When you freeze beef, the water inside its cells freezes into sharp ice crystals that can puncture cell membranes. When the beef thaws, moisture (and some of the B vitamins) will leak out through these torn cell walls. The loss of moisture is irreversible, but some of the vitamins can be saved by using the drippings when the meat is cooked. Freezing may also cause freezer burn—dry spots left when moisture evaporates from the surface of the meat. Waxed freezer paper is designed specifically to hold the moisture in meat; plastic wrap and aluminum foil are less effective. NOTE : Commercially prepared beef, which is frozen very quickly at very low temperatures, is less likely to show changes in texture. Irradiation. Irradiation makes meat safer by exposing it to gamma rays, the kind of high- energy ionizing radiation that kills living cells, including bacteria. Irradiation does not change the way meat looks, feels or tastes, or make the food radioactive, but it does alter the structure of some naturally occurring chemicals in beef, breaking molecules apart to form new com- pounds called radiolytic products (R P). About 90 percent of R Ps are also found in nonirradiated foods. The rest, called unique radiolytic products (UR P), are found only in irradiated foods. There is currently no evidence to suggest that UR Ps are harmful; irradiation is an approved technique in more than 37 countries around the world, including the United States. Smoking. Hanging cured or salted meat over an open fire slowly dries the meat, kills micro- organisms on its surface, and gives the meat a rich, “smoky” flavor that varies with the wood used in the fire. Meats smoked over an open fire are exposed to carcinogenic chemicals in the smoke, including a-benzopyrene. Meats treated with “artificial smoke flavoring” are not, since the flavoring is commercially treated to remove tar and a-benzopyrene.

Medical Uses and/or Benefits Treating and/or preventing iron deficiency. Without meat in the diet, it is virtually impossible for an adult woman to meet her iron requirement without supplements. One cooked 3.5- ounce hamburger provides about 2.9 mg iron, 16 percent of the R DA for an adult woman of childbearing age. Possible anti-diabetes activity. CLA may also prevent type 2 diabetes, also called adult-onset diabetes, a non-insulin-dependent form of the disease. At Purdue University, rats bred to develop diabetes spontaneously between eight and 10 weeks of age stayed healthy when given CLA supplements.

Adverse Effects Associated with This Food Increased risk of heart disease. Like other foods from animals, beef contains cholesterol and saturated fats that increase the amount of cholesterol circulating in your blood, raising your risk of heart disease. To reduce the risk of heart disease, the National Cholesterol Education Project recommends following the Step I and Step II diets. The Step I diet provides no more than 30 percent of total daily calories from fat, no more than 10 percent of total daily calories from saturated fat, and no more than 300 mg of cholesterol per day. It is designed for healthy people whose cholesterol is in the range of 200 –239 mg/dL. The Step II diet provides 25– 35 percent of total calories from fat, less than 7 percent of total calories from saturated fat, up to 10 percent of total calories from polyunsaturated fat, up to 20 percent of total calories from monounsaturated fat, and less than 300 mg cho- lesterol per day. This stricter regimen is designed for people who have one or more of the following conditions: •  Existing cardiovascular disease •  High levels of low-density lipoproteins (LDLs, or “bad” cholesterol) or low levels of high-density lipoproteins (HDLs, or “good” cholesterol) •  Obesity •  Type 1 diabetes (insulin-dependent diabetes, or diabetes mellitus) •  Metabolic syndrome, a.k.a. insulin resistance syndrome, a cluster of risk fac- tors that includes type 2 diabetes (non-insulin-dependent diabetes) Increased risk of some cancers. According the American Institute for Cancer Research, a diet high in red meat (beef, lamb, pork) increases the risk of developing colorectal cancer by 15 percent for every 1.5 ounces over 18 ounces consumed per week. In 2007, the National Can- cer Institute released data from a survey of 500,000 people, ages 50 to 71, who participated in an eight-year A AR P diet and health study identif ying a higher risk of developing cancer of the esophagus, liver, lung, and pancreas among people eating large amounts of red meats and processed meats. Food-borne illness. Improperly cooked meat contaminated with E. coli O157:H7 has been linked to a number of fatalities in several parts of the United States. In addition, meats con- taminated with other bacteria, viruses, or parasites pose special problems for people with a weakened immune system: the very young, the very old, cancer chemotherapy patients, and people with HIV. Cooking meat to an internal temperature of 140°F should destroy Salmo- nella and Campylobacter jejuni; 165°F, the E. coli organism; and 212°F, Listeria monocytogenes. Antibiotic sensitivity. Cattle in the United States are routinely given antibiotics to protect them from infection. By law, the antibiotic treatment must stop three days to several weeks before the animal is slaughtered. Theoretically, the beef should then be free of antibiotic residues, but some people who are sensitive to penicillin or tetracycline may have an allergic reaction to the meat, although this is rare. Antibiotic-resistant Salmonella and toxoplasmosis. Cattle treated with antibiotics may pro- duce meat contaminated with antibiotic-resistant strains of Salmonella, and all raw beef may harbor ordinary Salmonella as well as T. gondii, the parasite that causes toxoplasmosis. Toxoplasmosis is particularly hazardous for pregnant women. It can be passed on to the fetus and may trigger a series of birth defects including blindness and mental retardation. Both Salmonella and the T. gondii can be eliminated by cooking meat thoroughly and washing all utensils, cutting boards, and counters as well as your hands with hot soapy water before touching any other food. Decline in kidney function. Proteins are nitrogen compounds. When metabolized, they yield ammonia, which is excreted through the kidneys. In laborator y animals, a sustained high-protein diet increases the flow of blood through the kidneys, accelerating the natural age-related decline in kidney function. Some experts suggest that this may also occur in human beings.

Food/Drug Interactions Tetracycline antibiotics (demeclocycline [Declomycin], doxycycline [ Vibtamycin], methacycline [Rondomycin], minocycline [Minocin], oxytetracycline [Terramycin], tetracycline [Achromycin V, Panmycin, Sumycin]). Because meat contains iron, which binds tetracyclines into com- pounds the body cannot absorb, it is best to avoid meat for two hours before and after taking one of these antibiotics. Monoamine oxidase (MAO) inhibitors. Meat “tenderized” with papaya or a papain powder can interact with the class of antidepressant drugs known as monoamine oxidase inhibi- tors. Papain meat tenderizers work by breaking up the long chains of protein molecules. One by-product of this process is tyramine, a substance that constructs blood vessels and raises blood pressure. M AO inhibitors inactivate naturally occurring enzymes in your body that metabolize tyramine. If you eat a food such as papain-tenderized meat, which is high in tyramine, while you are taking a M AO inhibitor, you cannot effectively eliminate the tyramine from your body. The result may be a hypertensive crisis. Theophylline. Charcoal-broiled beef appears to reduce the effectiveness of theophylline because the aromatic chemicals produced by burning fat speed up the metabolism of the- ophylline in the liver.... beef

See also MYALGIC ENCEPHALOMYELITIS (ME). A condition characterised by severe, disabling mental and physical fatigue brought on by mental or physical activity and associated with a range of symptoms including muscle pain, headaches, poor sleep, disturbed moods and impaired concentration. The prevalence of the condition is between 0.2 and 2.6 per cent of the population (depending on how investigators de?ne CFS/ME). Despite the stereotype of ‘yuppie ?u’, epidemiological research has shown that the condition occurs in all socioeconomic and ethnic groups. It is commoner in women and can also occur in children.

In the 19th century CFS was called neurasthenia. In the UK, myalgic encephalomyelitis (ME) is often used, a term originally introduced to describe a speci?c outbreak such as the one at the Royal Free Hospital, London in 1955. The term is inaccurate as there is no evidence of in?ammation of the brain and spinal cord (the meaning of encephalomyelitis). Doctors prefer the term CFS, but many patients see this as derogatory, perceiving it to imply that they are merely ‘tired all the time’ rather than having a disabling illness.

The cause (or causes) are unknown, so the condition is classi?ed alongside other ‘medically unexplained syndromes’ such as IRRITABLE BOWEL SYNDROME (IBS) and multiple chemical sensitivity – all of which overlap with CFS. In many patients the illness seems to start immediately after a documented infection, such as that caused by EPSTEIN BARR VIRUS, or after viral MENINGITIS, Q FEVER and TOXOPLASMOSIS. These infections seem to be a trigger rather than a cause: mild immune activation is found in patients, but it is not known if this is cause or e?ect. The body’s endocrine system is disturbed, particularly the hypothalamopituitary-adrenal axis, and levels of cortisol are often a little lower than normal – the opposite of what is found in severe depression. Psychiatric disorder, usually depression and/or anxiety, is associated with CFS, with rates too high to be explained solely as a reaction to the disability experienced.

Because we do not know the cause, the underlying problem cannot be dealt with e?ectively and treatments are directed at the factors leading to symptoms persisting. For example, a slow increase in physical activity can help many, as can COGNITIVE BEHAVIOUR THERAPY. Too much rest can be harmful, as muscles are rapidly weakened, but aggressive attempts at coercing patients into exercising can be counter-productive as their symptoms may worsen. Outcome is in?uenced by the presence of any pre-existing psychiatric disorder and the sufferer’s beliefs about its causes and treatment. Research continues.... chronic fatigue syndrome (cfs)

A group of ANTIBIOTICS. The original macrolide, ERYTHROMYCIN, was discovered in the early 1950s and used successfully as an alternative to PENICILLIN. The name ‘macrolide’ derives from the molecular structure of this group, three others of which are clarithromycin, azithromycin and spiramycin. Macrolides check PROTEIN synthesis in BACTERIA and the latest ones are, like erythromycin, active against several bacterial species including gram-positive COCCI and rods. In addition, they act against Haemophilus in?uenzae. Clarithromycin is potent against Helicobacter pylori; azithromycin is e?ective against infections caused by Legionella spp. (see LEGIONNAIRE’S DISEASE) and GONOCOCCI. Spiramycin is a restricted-use macrolide prescribed for pregnant patients with TOXOPLASMOSIS.... macrolides

A variety of diseases which occur in some individuals who do not have healthy immune systems. These are microorganisms which do not usually cause diseases in a healthy individual. They are seen in AIDS patients and include Pneumocystis carinii pneumonia, massive or overwhelming herpes infections, atypical mycobacteria, toxoplasmosis or chronic or overwhelming candidiasis.... opportunistic infections

One of the MACROLIDES isolated from Streptomyces ambofaciens which is used under strict conditions for the treatment of TOXOPLASMOSIS.... spiramycin

Animal diseases which can be transmitted to humans. There are more than 150 infections of domestic and wild vertebrates which can be transmitted in this way, including BOVINE SPONGIFORM ENCEPHALOPATHY (BSE), bovine tuberculosis, BRUCELLOSIS, HYDATID cysts, RINGWORM, TOXOCARIASIS, TOXOPLASMOSIS, LEPTOSPIROSIS, LISTERIOSIS, and RABIES.... zoonoses

Inflammation of the choroid. It is often caused by infections such as toxocariasis or toxoplasmosis, more rarely by sarcoidosis, syphilis, and histoplasmosis. It sometimes has no obvious cause. Treatment includes corticosteroid drugs for the inflammation, and antibiotic drugs for any causative infection.... choroiditis

The simplest, most primitive type of animal, consisting of a single cell. All protozoa are bigger than bacteria but are still microscopic. About 30 types of protozoa

are human parasites, including those that are responsible for

Endoplasmic malaria, amoebiasis, reticulum giardiasis, sleeping sickness, trichomoniasis, toxoplasmosis, and leishmaniasis.... protozoa

n. an antibacterial drug consisting of sulfamethoxazole (a *sulphonamide) and *trimethoprim, each of which potentiates (increases) the action of the other. Because of the severity of its side-effects, which are those of the sulphonamides, co-trimoxazole is now usually limited to treating *Pneumocystis pneumonia, toxoplasmosis, and nocardiasis.... co-trimoxazole

n. a drug administered in combination with the *sulphonamide sulfadoxine for the treatment of malignant (falciparum) *malaria. It is also used, in combination with *sulfadiazine, in the treatment of toxoplasmosis. Possible side-effects include loss of appetite and vomiting, and prolonged use may interfere with red blood cell production (pyrimethamine is a *dihydrofolate reductase inhibitor).... pyrimethamine

ACUTE LIVER DISEASE The hepatitis viruses (A– F) are of paramount importance. Hepatitis E (HEV) often produces acute hepatic failure in pregnant women; extensive epidemics – transmitted by contaminated drinking-water supplies – have been documented. HBV, especially in association with HDV, also causes acute liver failure in infected patients in several tropical countries: however, the major importance of HBV is that the infection leads to chronic liver disease (see below). Other hepatotoxic viruses include the EPSTEIN BARR VIRUS, CYTOMEGALOVIRUS (CMV), the ?avivirus causing YELLOW FEVER, Marburg/Ebola viruses, etc. Acute liver disease also occurs in the presence of several acute bacterial infections, including Salmonella typhi, brucellosis, leptospirosis, syphilis, etc. The complex type of jaundice associated with acute systemic bacterial infection – especially pneumococcal PNEUMONIA and pyomiositis – assumes a major importance in many tropical countries, especially those in Africa and in Papua New Guinea. Of protozoan infections, plasmodium falciparum malaria, LEISHMANIASIS, and TOXOPLASMOSIS should be considered. Ascaris lumbricoides (the roundworm) can produce obstruction to the biliary system. CHRONIC LIVER DISEASE Long-term disease is dominated by sequelae of HBV and HCV infections (often acquired during the neonatal period), both of which can cause chronic active hepatitis, cirrhosis, and hepatocellular carcinoma (‘hepatoma’) – one of the world’s most common malignancies. Chronic liver disease is also caused by SCHISTOSOMIASIS (usually Schistosoma mansoni and S. japonicum), and acute and chronic alcohol ingestion. Furthermore, many local herbal remedies and also orthodox chemotherapeutic compounds (e.g. those used in tuberculosis and leprosy) can result in chronic liver disease. HAEMOSIDEROSIS is a major problem in southern Africa. Hepatocytes contain excessive iron – derived primarily from an excessive intake, often present in locally brewed beer; however, a genetic predisposition seems likely. Indian childhood cirrhosis – associated with an excess of copper – is a major problem in India and surrounding countries. Epidemiological evidence shows that much of the copper is derived from copper vessels used to store milk after weaning. Veno-occlusive disease was ?rst described in Jamaica and is caused by pyrrolyzidine alkaloids (present in bush-tea). Several HIV-associated ‘opportunistic’ infections can give rise to hepatic disease (see AIDS/HIV).

A localised (focal) form of liver disease in all tropical/subtropical countries results from invasive Entamoeba histolytica infection (amoebic liver ‘abscess’); serology and imaging techniques assist in diagnosis. Hydatidosis also causes localised liver disease; one or more cysts usually involve the right lobe of the liver. Serological tests and imaging techniques are of value in diagnosis. Whilst surgery formerly constituted the sole method of management, prolonged courses of albendazole and/or praziquantel have now been shown to be e?ective; however, surgical intervention is still required in some cases.

Hepato-biliary disease is also a problem in many tropical/subtropical countries. In southeast Asia, Clonorchis sinensis and Opisthorchis viverini infections cause chronic biliary-tract infection, complicated by adenocarcinoma of the biliary system. Praziquantel is e?ective chemotherapy before advanced disease ensues. Fasciola hepatica (the liver ?uke) is a further hepato-biliary helminthic infection; treatment is with bithionol or triclabendazole, praziquantel being relatively ine?ective.... liver disease in the tropics

Abnormalities that are obvious at birth or detectable early in infancy. Also called congenital defects, they encompass both minor abnormalities, such as birthmarks, and serious disorders such as spina bifida.

Causes include chromosomal abnormalities, genetic defects, drugs taken during pregnancy, exposure to radiation, and infections. In some cases, the cause of a defect is unknown. Defects that are due to chromosomal abnormalities include Down’s syndrome. Some defects, such as achondroplasia and albinism, are usually inherited from 1 or both parents (see gene; genetic disorders). Certain drugs and chemicals (called teratogens) can damage the fetus if the mother takes or is exposed to them during early pregnancy. Teratogenic drugs include thalidomide (now rarely prescribed) and isotretinoin, which is used in the treatment of severe acne. Alcohol can affect the development of the brain and face (see fetal alcohol syndrome).

Irradiation of the embryo in early pregnancy can cause abnormalities. Very small doses of radiation increase the child’s risk of developing leukaemia later in life (see radiation hazards).

Certain illnesses, such as rubella (German measles) and toxoplasmosis, can cause birth defects if they are contracted during pregnancy.

Brain and spinal cord abnormalities, such as spina bifida and hydrocephalus, and congenital heart disorders (see heart disease, congenital) result from interference with the development of particular groups of cells. Other common defects include cleft lip and palate.

Ultrasound scanning and blood tests during pregnancy can identify women at high risk of having a baby with a birth defect. Further tests such as chorionic villus sampling, amniocentesis, or fetoscopy may then be carried out.... birth defects

(sulphadiazine) n. a drug of the *sulphonamide group that is used to prevent the recurrence of rheumatic fever and (in combination with *pyrimethamine) to treat toxoplasmosis. In the form of silver sulfadiazine, it is applied to treat infected burns, leg ulcers, and pressure sores.... sulfadiazine

n. a genus of crescent-shaped sporozoans that live as parasites within the cells of various tissues and organs of vertebrate animals, especially birds and mammals, and complete their life cycle in a single host, the cat. T. gondii infects sheep, cattle, dogs, and humans, sometimes provoking an acute illness (see toxoplasmosis).... toxoplasma

n. an infectious disease of animals that can be transmitted to humans. See anthrax; avian influenza; brucellosis; cat-scratch disease; cowpox; glanders; Q fever; Rift Valley fever; rabies; rat-bite fever; toxoplasmosis; tularaemia; typhus.... zoonosis

Acquired immune deficiency syndrome, a deficiency of the immune system due to infection with HIV (human immunodeficiency virus). In most countries, illness and death from is a growing health problem, and there is, as yet, no cure or vaccine.

does not develop in all people infected with. The interval between infection and the development of is highly variable. Without treatment, around half of those people infected will develop within 8–9 years.

is transmitted in body fluids, including semen, blood, vaginal secretions, and breast milk. The major methods of transmission are sexual contact (vaginal, anal, or oral), blood to blood (via transfusions or needle-sharing in drug users), and mother to fetus. has also been transmitted through blood products given to treat haemophilia, artificial insemination by donated semen, and kidney transplants; but improved screening has greatly reduced these risks. is not spread by everyday contact, such as hugging or sharing crockery. The virus enters the bloodstream and infects cells that have a particular receptor, known as the CD4 receptor, on their surface. These cells include a type of white blood cell (a CD4 lymphocyte) responsible for fighting infection and cells in other tissues such as the brain. The virus reproduces within the infected cells, which then die, releasing more virus particles into the blood. If the infection is left untreated, the number of CD4 lymphocytes falls, resulting in greater susceptibility to certain infections and some types of cancer.

Some people experience a short-lived illness similar to infectious mononucleosis when they are first infected with. Many individuals have no obvious symptoms; some have only vague complaints, such as weight loss, fevers, sweats, or unexplained diarrhoea, described as -related complex.

Minor features of infection include skin disorders such as seborrhoeic dermatitis. More severe features include persistent herpes simplex infections, oral candidiasis (thrush), shingles, tuberculosis, and shigellosis. may also affect the brain, causing a variety of neurological disorders, including dementia.

Certain conditions, known as AIDSdefining illnesses, are characteristic of full-blown. These include cancers (Kaposi’s sarcoma and lymphoma of the brain), and various infections (pneumocystis pneumonia, cytomegalovirus infection, toxoplasmosis, diarrhoea due to CRYPTOSPORIDIUM or ISOSPORA, candidiasis, disseminated strongyloidiasis, and cryptococcosis), many of which are described as opportunistic infections.

Confirmation of infection involves testing a blood sample for the presence of antibodies to. Diagnosis of fullblown is based on a positive test along with the presence of an AIDSdefining illness.

The risk of infection with can be reduced by practising safer sex. Intravenous drug users should not share needles. There is a small risk to health workers handling infected blood products or needles, but this risk can be minimized by safe practices.

Treatment of infection with a combination of antiviral drugs can slow the disease’s progress, and may prevent the development of full-blown. The 2 main types of antiviral drug used are protease inhibitors, such as indinavir, and reverse transcriptase inhibitors such as zidovudine. Treatment is also available for -defining illnesses.... aids

Various parasites and infectious organisms can spread from cats to humans. The most serious disease is rabies. Cat-scratch fever is an uncommon illness caused by infection with the bacterium ROCHALIMAEA HENDELAE following a cat scratch or bite. Cats commonly carry the protozoan TOXOPLASMA GONDII, which causes toxoplasmosis.

Infection, usually from contact with cat’s faeces, is not generally serious but has serious consequences if a woman is infected during pregnancy.

Cat faeces may also carry eggs of the cat roundworm, a possible cause of toxocariasis.

Rarely, a larva from an ingested roundworm egg migrates to and lodges in an eye, causing deterioration of vision or even blindness.

Children who have been playing in sand or soil contaminated by cat faeces are most commonly affected.

Other cat-related disorders in humans include tinea (ringworm), fungal infections of the skin, bites from cat fleas, and allergic reactions to dander that may cause asthma or urticaria.

Diseases from cats can be avoided by good hygiene, veterinary care for animals that are ill, and regular worming and flea treatment of cats.... cats, diseases from

A method of diagnosing genetic abnormalities in a fetus using a small sample of tissue taken from the chorionic villi at edge of the placenta. Because the cells have the same chromosome makeup as those in the fetus, they can be used to detect genetic abnormalities. Chorionic villus sampling (CVS) is usually performed in the first 3 months of pregnancy in women who are at a higher-than-normal risk of having a child with a chromosomal disorder, such as Down’s syndrome, or a genetic disease, such as thalassaemia. Chromosome analysis of the villi cells takes place in the laboratory. CVS slightly increases the risk of miscarriage. choroid A layer of tissue at the back of the eye, behind the retina. The choroid contains many blood vessels that supply nutrients and oxygen to the retinal cells and to surrounding tissues in the eye. choroiditis Inflammation of the choroid. It is often caused by infections such as toxocariasis or toxoplasmosis, more rarely by sarcoidosis, syphilis, and histoplasmosis. It sometimes has no obvious cause. Treatment includes corticosteroid drugs for the inflammation, and antibiotic drugs for any causative infection.... chorionic villus sampling

Infection acquired in the uterus or during birth. Many microorganisms can pass from the mother, by way of the placenta, into the circulation of the growing fetus. Particularly serious infections acquired in the uterus are rubella, syphilis, toxoplasmosis, and cytomegalovirus; all these infections may cause intrauterine growth retardation. Rubella that occurs in early pregnancy may cause deafness, congenital heart disease, and eye disorders. Some infections in later pregnancy, particularly with a herpes virus, may also damage the fetus severely. A woman infected with HIV risks passing on the virus to her baby during pregnancy, but the risk can be reduced by use of antiretroviral drugs during the pregnancy.

Infections acquired during birth are almost always the result of microorganisms in the mother’s vaginal secretions or uterine fluid. Premature rupture of the membranes is associated with increased risk of infection, particularly streptococcal. Conditions that can be acquired during delivery include herpes, chlamydial infections, and gonorrhoea.

Treatment of the baby depends on the type of infection. Some birth defects caused by infection (such as certain types of heart defect) can be treated; others (such as congenital deafness) are usually not treatable.... infection, congenital