Sovrin M. Shah, MD

• Assistant Professor of Urology,
• Albert Einstein College of Medicine, Bronx, New York
• Physician-in-Charge,
• Female Urology, Voiding Dysfunction, and Pelvic
• Reconstructive Surgery,
• Beth Israel Medical Center, New York, New York

Some clinically apparent tumors that "heal spontaneously" also are most likely destroyed by the immune system symptoms ketosis trusted 50mg thorazine. There is clinical evidence that some tumors may regress if treated by immunotherapy treatment 2 degree burns order cheapest thorazine and thorazine. All of these facts point to antitumor immunity as an important byproduct of the interaction between the tumor and the host medications lexapro 50mg thorazine fast delivery. Antigenic changes that occur during malignant transformation also have diagnostic value in the clinical laboratory medicine reminder app order thorazine 50 mg on line. The immune response of the host to tumor cells may be augmented for therapeutic purposes symptoms ringworm buy thorazine us. The tumor cells that are highly immunogenic are the best targets for immunotherapy medications with weight loss side effects purchase thorazine with amex. The lymph nodes draining a tumorinfiltrated area may contain granulomas and represent a cell-mediated immune response to the tumor. These skin tumors evoke a strong lymphocytic response and may even regress spontaneously. Some of the fetal tumors, such as neuroblastoma, also may heal spontaneously by transforming into ganglioneuroma, a tumor composed of mature ganglion and glial cells. This nonspecific stimulus evokes an influx of macrophages that destroy tumor cells. The important function of the immune system in controlling tumor growth is evident in the frequent occurrence of tumors in immunosuppressed hosts. Clinical Manifestations of Neoplasia Clinical manifestations of neoplasia are highly variable because cancer is not a single disease. Cancer may present in various forms; thus, it is prudent to think of cancer whenever some unusual symptoms of disease occur. A tumor in the lungs may impinge upon and irritate the bronchi and cause coughing. Persistent compression of normal tissues may cause atrophy, as is commonly seen in benign tumors adjacent to bones. Invasion of blood vessels and erosion of normal tissues by tumors often results in hemorrhage. Hemorrhage is the most common symptom of tumors in the large intestine, kidney, and urinary bladder. Tumors growing into the lumen of hollow organs, such as the intestines, may cause narrowing of the lumen or obstruction. In the large intestine, the stool passing through a narrowed segment appears pencil-like and the intestinal passage could ultimately be blocked completely. Bronchial obstruction as a result of lung cancer causes stagnation of mucus in the bronchus and coughing. Carcinoma of the pancreas may impede the entry of pancreatic juices into the intestine, which may lead to malabsorption of nutrients, minerals, and vitamins. Paraneoplastic syndromes are caused by various substances secreted by cancer cells. Paraneoplastic syndromes include various endocrine, hematologic, neuromuscular, and cardiovascular changes. Bone demineralization is a common feature of breast cancer and is typically associated with hypercalcemia. This hypercoagulability results from the entry of tumor degradation products or secretions. In pancreatic cancer, thrombosis is often described as migratory; that is, it sequentially affects different veins without apparent order or regularity. Thrombosis is often associated with inflammation of occluded veins (thrombophlebitis). Although it is most often associated with pancreatic cancer, it may be caused by other cancers as well. An understanding of clinical symptoms of cancer is most important for the diagnosis and early detection of neoplasia. The most important cancer risk factors and presenting signs are listed in Table 4-5. These symptoms include cachexia or generalized weakness, weight loss, loss of appetite (anorexia), and a variety of paraneoplastic syndromes. Cachexia is caused by wasting, secondary to the adverse effects of cancer on the body. Cancer can be considered a parasite that drains the energy from the body and also competes for nutrients. There are no symptoms specific to cancer; therefore, the best way to diagnose this disease is to consider it in almost any clinical setting. Because most cancers remain incurable if diagnosed in an advanced stage, the best hope of conquering cancer lies in its early detection and regular preventive examinations. The seven safeguards against cancer, recommended by the American Cancer Society, are listed in Box 4-1. The most important epidemiologic data relate to cancer incidence, prevalence, and mortality. Incidence Incidence of cancer is the number of new cases that have been registered over a specific period in a defined population. For example, gastric cancer is common in Japan and Iceland, but is less common in Western Europe and the United States. This discrepancy is thought to be attributable to different dietary habits and the high consumption of raw and smoked fish in the former countries. Indeed, the descendants of Japanese immigrants in the United States have less cancer of the stomach than their relatives who are still living in Japan. Cancer Epidemiology Epidemiology of neoplasia is concerned with the study of cancer in human populations. Epidemiologic studies are based on data gathered from cancer registries and clinical records, or by active inquiry. Mortality Mortality of cancer is the number of deaths attributed to cancer during a specified period in a defined population. For example, the mortality of patients with testicular cancer has decreased dramatically since the 1970s. However, the mortality from lung cancer has remained the same over the past 30 years. The study of epidemiology has provided new insights into the endogenous and exogenous causes of cancer. Because cancer occurs most often in older people, and more exist today than ever before, the increased incidence of cancer in our time is not unexpected. Gastric cancer, which was prevalent in earlier years, has become less common than colon cancer. This form of cancer was uncommon among women, but today it is as common in women as in men. These changes in the incidence of cancer reflect changes in living conditions, habits, and diet. Cancer is the second most common cause of death in the United States, eclipsed only by cardiovascular disease. Compare normal and malignant cells; taking into account their morphology, list some basic biologic functions and biochemical properties. Prevalence Prevalence of cancer is the number of all cases of cancer- new and old-within a defined population at a defined time. This is in part attributable to improved diagnostic methods and life-prolonging treatment, but it may also be the result of increased exposure to environmental carcinogens. Thus, it is no wonder that skin cancer is more prevalent in the southern United States than in the north. The increased prevalence of prostate cancer correlates with the generally increased longevity of human populations, especially in the Western world. About61,000femalecarcinoma in situ of the breast and 68,480 melanoma in situ will be newly diagnosed in 2016). Define paraneoplastic syndrome and provide specific examples of syndromes dominated by endocrine, hematologic, or neuromuscular changes. Explain teratogenesis and list the five of the most common identifiable causes of birth defects in humans. Define the structural chromosomal abnormalities, such as deletion and translocation. Explain the pathogenesis of lysosomal storage diseases, and give three specific examples of prototypic disorders. List the features of three important diseases based on multifactorial inheritance. Describe how immaturity of the lungs causes neonatal respiratory distress syndrome. This chapter deals with disturbances in development, from the time of fertilization to delivery. Major genetic and environmental factors that could influence the intrauterine development of the embryo and fetus will be briefly discussed. Early cleavage-stage embryos consist of cells whose developmental potential has not been firmly programmed. Loss of single cells at the two-, four-, and eight-cell stages can easily be compensated for without any adverse consequences. However, at the blastocyst stage, the fate of embryonic cells has been determined: cells of the inner cell mass will give rise to the embryo proper, whereas the outer layer, called the trophoblast, will give rise to the placenta. After this stage of development, any cell loss in the inner cell mass will result in embryonic defects, because such cell losses cannot be replaced. The inner cell mass gives rise to the primordial germ layers: ectoderm, mesoderm, and endoderm. A, the preimplantation stage, which extends from the first cleavage of the zygote to the formation of the blastocyst. The development of organs is tightly regulated by special master genes, called homeobox genes, which regulate and coordinate the expression of other genes in the developing tissues. As the genes are turned on and off, each organ passes through a specific organogenetic period. During the critical stages of organogenesis, which are those characterized by extensive cell division, migration, and cell-to-cell interaction, the developing organs are very sensitive to adverse external influences. Chemical, physical, and viral agents are most prone to induce developmental defects during these developmental stages. Generally speaking, the critical period for most organs is in the first trimester of pregnancy. However, some organs, such as the brain, do not complete development during intrauterine life and are therefore susceptible to adverse influences for several months after birth. In humans, the period of organogenesis that is conventionally called fetal life lasts approximately 38 to 42 weeks. During this period, various organs become anatomically recognizable; they assume specific histologic features, and become functionally active. For example, by 10 to 12 weeks of gestation, one can recognize the fetal penis or vulva and determine the sex of the fetus. It is also possible to see whether the kidneys have been formed and to examine many other organs to determine whether they are developing normally. Fetal organs have a "fetal histology and cytology," and are composed of cells that have functions different from those of normal adult organs. Fetal lungs are functionally immature because they secrete a different form of surfactant than the adult lung and therefore are incompetent for respiration. Many organs, such as testicles, acquire full functional competence only at puberty, and need special hormonal stimuli to mature. For example, female breast acini develop fully only after pregnancy and during lactation. Developmental Malformations Disturbances in development are the subject of a science called teratology. The agents that cause fetal abnormalities (malformations) are thus called teratogens. Among the identifiable causes of developmental malformations, the most prominent are genetic factors (20%). Various exogenous teratogens, such as drugs, alcohol, or x-ray exposure, account for a small number of human malformations. By avoiding exposure to potential teratogens, pregnant women can protect their unborn babies and prevent the development of some malformations. Genetic Factors Genes inherited from the parents control not only specific traits, such as height or skin color but also development in utero. The lack of certain essential genes or their mutation (lethal mutations) results in abnormal development. Such embryos and fetuses are not viable beyond a certain stage of development and are usually aborted spontaneously. Numerous studies performed on spontaneously aborted fetuses have shown that most of them had genetic defects and that many had abnormal chromosomes. The genetic basis of malformations has been documented for a number of human congenital defects. For example, the incidence of cleft lip (commonly known as harelip) is increased in some families and is inherited as a multifactorial trait. Achondroplastic dwarfism, characterized by short arms and legs, is caused by a single gene defect inherited as an autosomal dominant Mendelian trait. Physical Teratogens the best-known physical teratogens are x-rays and other forms of corpuscular radiation (alpha, beta, and gamma rays). For example, an increased incidence of malformations was noted among Japanese children born to mothers exposed during pregnancy to the atomic bomb explosions in Hiroshima and Nagasaki in 1945.

The extrapyramidal processing centers produce output to a variety of targets including: a schedule 9 medications buy cheap thorazine 100mg online. The sympathetic division of the autonomic nervous system is best characterized by the concept of: a treatment brown recluse bite discount thorazine online master card. When nociceptors are initially stimulated treatment 1st 2nd degree burns cheapest thorazine, the first response is the firing of the receptors to produce an immediate message to the central nervous system that results in the perception known as: a symptoms thyroid discount thorazine express. Pain and temperature impulses are carried to the central nervous system via the: a medications not to be crushed generic 50 mg thorazine with amex. Efferent motor impulses originating in the precentral gyrus of the left cerebral hemisphere control the: a medications kosher for passover order cheapest thorazine and thorazine. Afferent sensory impulses originating on the left side of the body are perceived by the: a. The ventral posterior portion of the ventral nuclei is the primary relay station for the transmission of: a. The main risk of the use of abortive therapies in the treatment of migraine headache includes: a. The painless neurologic phenomenon associated with migraine with aura includes: a. In contradistinction to migraine and tension-type headache, cluster headache is unique in its: a. Herpes zoster infection involving the geniculate ganglion and external auditory canal and auricle is called: a. Cervical radiculopathy is best treated with a multimodality approach including: a. Patients will commonly place the hand of the affected extremity on the top of the head in order to obtain relief when suffering from compromise of which of the following cervical nerve roots Physical examination results of the patient suffering from cervical strain may include: a. Cervicothoracic bursitis is best treated with a multimodality approach including: a. Fibromyalgia of the cervical spine is best treated with a multimodality approach including: a. Cervical facet syndrome is best treated with a multimodality approach including: a. The patient below of Scandinavian origin presents with the complaint of the gradual onset of loss of function of his little and middle fingers with this distressing cosmetic defect. Patients suffering from lumbar myelopathy or cauda equina syndrome will experience: a. Provocation of the symptoms of thoracic outlet syndrome may be elicited by a variety of maneuvers including the: a. Mechanisms implicated in the compression of the radial nerve in radial tunnel syndrome include: a. Which of the following painful conditions can be misdiagnosed as radial tunnel syndrome The pain and muscle weakness of anterior interosseous syndrome can be caused by: a. Olecranon bursitis may develop gradually due to repetitive irritation of the olecranon bursa or acutely due to trauma or infection. The olecranon bursa may exist as a single bursal sac or, in some patients, as a multisegmented series of sacs that may be loculated in nature. The patient suffering from olecranon bursitis will frequently complain of pain and swelling with any movement of the elbow but especially with extension. The pain of olecranon bursitis is localized to the olecranon area, with referred pain often noted above the elbow joint. Passive extension and resisted flexion of the shoulder will reproduce the pain, as will any pressure over the bursa. Disorders that may mimic the symptoms of diabetic truncal neuropathies include: a. Topical agents shown to be useful in the palliation of pain secondary to the pain of diabetic truncal neuropathy include: a. Herpes zoster is an infectious disease that is caused by the varicellazoster virus. The thoracic nerve roots are the most common site for the development of acute herpes zoster. Primary infection with the varicella-zoster virus in the nonimmune host manifests itself clinically as chickenpox. During the course of primary infection with varicella-zoster virus, the virus migrates to the dorsal root of the thoracic nerves where it remains dormant. The patient with acute pancreatitis will exhibit the following signs and symptoms: a. The abnormal laboratory finding that is the sine qua non of acute pancreatitis is: a. Arthritis of the hip should be treated with a multimodality approach including: a. The most common joints affected in patients suffering from rheumatoid arthritis include the: a. Disease-modifying drugs that are useful in the treatment of rheumatoid arthritis include: a. Laboratory findings commonly seen in patients suffering from rheumatoid arthritis include a(n): a. The laboratory test that is highly diagnostic for systemic lupus erythematosus is: a. Polymyalgia rheumatica is characterized by a constellation of musculoskeletal symptoms that include: a. The portion of the thalamus that is most often associated with central pain is the: a. The pathognomonic cutaneous sign associated with lightning injuries is known as the: a. The neurotransmitter(s) thought to be most involved in the phenomenon of addiction include(s): a. The paramagnetic contrast agent gadolinium should be used with caution in patients with: a. The classic finding on nerve conduction studies in patients suffering from moderately severe peripheral neuropathy is: a. The peak of greatest interest in visual evoked potential testing is called the: a. Examples of unidimensional pain assessment tools that are useful in the evaluation of adult patients in pain include the: a. Examples of multidimensional pain assessment tools that are useful in the evaluation of adult patients in pain include the: a. Examples of pain assessment tools that are useful in the evaluation of pain in children include: a. Ligamentous structures that an epidural needle will traverse prior to entering the cervical epidural space include the: a. Nerves from the brachial plexus that surround the axillary artery that can be blocked when performing brachial plexus block using the axillary approach include the: a. The preganglionic fibers of the thoracic sympathetics provide sympathetic innervation to the: a. Posterior to the sternoclavicular joint are a number of large arteries and veins including the: a. Complications associated with injection of the costosternal joints include trauma to the: a. When performing celiac plexus block, if the needle is placed in the retrocrural space: a. Incorrect needle placement during caudal epidural block can include placement of the needle: a. Side effects and complications associated with blockade of the sacral nerve roots include: a. When performing injection of the iliopectinate bursa, a paresthesia is occasionally elicited when the needle impinges on the: a. Neurologic complications associated with subarachnoid neurolytic block include: a. Side effects and complications associated with subarachnoid neurolytic block include: a. When performing hyperbaric subarachnoid neurolytic block, the patient is positioned: a. When performing hyporbaric subarachnoid neurolytic block, the patient is positioned: a. Contraindications to the use of transcutaneous electrical nerve stimulators include: a. When administered into the subarachnoid space, relative to cerebrospinal fluid, ethyl alcohol is: a. The following class of analgesics has recently been associated with a higher incidence of cardiovascular side effects compared with other classes of analgesics: a. Meprobamate dependence has been associated with the prolonged use of which of the following muscle relaxants Unique physiologic abnormalities in the newborn that may affect how narcotic analgesics are used include: a. The following analgesics are generally considered safe in the pediatric population: a. The following are considered factors that cause concern when evaluating a patient with headache: a. Fibers from each optic nerve cross the midline to exit the chiasm together at the opposite optic tract. Via the optic tract and optic radiations, visual information carried by the optic nerve is projected onto the occipital lobes. Eukaryotic Parasites Eukaryotic parasites encompass subsets of organisms within the protozoan and helminth (parasitic worm) groups. In addition, medically important arthropods have been included in discussions of eukaryotic parasites, since so many of these pathogens are transmitted to humans by arthropod vectors. From a biological perspective, a phylogenetic presentation of eukaryotic parasitic organisms would undoubtedly satisfy those specialists who strictly adhere to the zoological literature, while most medical students and practicing clinicians would have little or no use for this information. The physician is more inclined to group them according to their syndromes, if they were to classify them at all. We have settled upon a compromise, in which these organisms are encountered by the reader in a somewhat biologically correct order, together with an outline of their classification and clinical presentations. Nonetheless, it is in some sense intellectually satisfying to review parasitic organisms with a semblance of evolutionary precision, allowing each student to learn about them in a sequence that most experts in the field of parasitology have agreed upon, going from the single-cell parasites to the worms and beyond. We present protozoans first, followed by the helminths, and finally round out the synopsis with medically relevant arthropods. The last half of the twentieth century has been a remarkable one for the communitybased control of pathogenic organisms. New vaccines and antibiotics have also helped reduce the incidence of numerous pathogenic organisms. At the same time, it has also heralded the emergence and re-emergence of a wide spectrum of infectious agents: viruses. Viewed from an evolutionary perspective, humans represent a highly successful system of essential niches, of which an astonishingly wide variety of eukaryotes have been able to take advantage. The number of individuals infected with any given parasite rarely makes but little impression on even the most attentive medical student, especially when it is a very large number, as is the case for Ascaris lumbricoides, which infects hundreds of millions of people around the world. Yet, when a single child suffering from the cerebral form of this disease-causing entity is admitted into a modern hospital in critical condition, and, regardless of treatment, that young person dies, the health care community of that institution is put into collective shock. If the death occurred at a teaching hospital, a grand rounds is the usual outcome, perhaps motivated by some vague sense of guilt, in an attempt to see if anything could have been done to spare that life. Unfortunately the most lethal species of malaria, Plasmodium falciparum, is evolving more and more resistance to the medications in our arsenal. There are over 200,000 named species of single-celled organisms that fall under the category protozoa, while 2 Eukaryotic Parasites many more, no doubt, await discovery. Only some small fraction of these are parasitic for the human host, yet some can cause great harm. Protozoans are single-cell organisms inside of which usually resides one membrane-bound nucleus, with a few exceptions, such as Giardia lamblia and Dientamoeba fragilis. Metabolic pathways also vary from group to group, with both anaerobic and aerobic energy metabolisms being represented among the parasites to be discussed. There are a variety of drugs that take advantage of the dependence of parasites on host energy metabolism. The following sections are organized in such a way as to enable the student or clinician easy access to a highly distilled body of information relating to the general schemes employed when these organisms interact with the human host to produce disease. Thus, rather than being an exhaustive text, only biological information essential to the understanding of clinical aspects of a given disease-causing organism will be emphasized. All singlecell organisms have complex biochemistries, often employing unique pathways that give some of them remarkable evolutionary advantages. A plethora of unique molecular pathways have been described for this diverse group of parasites, but a comprehensive description of them is beyond the scope of this book.

In addition to all of his scientific contributions medications diabetes discount thorazine 100mg free shipping, Redi was an accomplished poet symptoms for bronchitis thorazine 50 mg sale. His life-sized statue stands proudly looking down on all who visit the world-renowned Uffizi Museum in Florence medicine lake montana order thorazine 50 mg online, Italy stroke treatment 60 minutes discount thorazine 100mg without prescription. Tapeworms of Minor Medical Importance Hymenolepis nana (Siebold 1852) Introduction Hymenolepis nana hb treatment discount 100 mg thorazine overnight delivery, in the order Cyclophyllidea medications vaginal dryness buy online thorazine, has a worldwide distribution, and infects mostly children, with prevalence in children as high as 25% in certain areas. The adult consists of 150-200 proglottids, and lives in the lumen of the small intestine, loosely attached to the epithelial cells of the villi. Like Strongyloides stercoralis, Hymenolepis nana is able to complete its entire life cycle within the human host. Autoinfection results in a high worm burden, particularly in immunosuppressed patients. Gravid segments break off from the strobila and disintegrate in the small intestine, releasing the fertilized, embryonated eggs. Autoinfection, with released eggs hatching directly within the intestine, is a possibility, but rarely occurs, as immunity to reinfection develops in most instances. In the invertebrate host, the oncospheres hatch and penetrate the gut and enter the hemocele where they differentiate into cysticercoid metacestodes. If the cysticercoid is ingested, then it attaches to the wall of the small intestine and differentiates and matures to the adult worm, usually within a two-week period. Although the lifespan of an adult worm is only 4-6 weeks, internal autoinfection can allow an infection to last for years. When whole pieces of strobila are passed, they can be identified directly, or the eggs can be expressed from gravid proglottids and then identified. Treatment Praziquantel is the drug of choice because it affects both the cysticercoid in the villus tissue and the adult. In contrast, niclosamide kills the adult, but it is not effective against the metacestode. Nitazoxanide has been investigated as a broad-spectrum antiparasitic for children with multiple intestinal protozoa and helminths, including H. The cysticercoid stage is relatively non-immunogenic, allowing for autoinfection to develop. In contrast, infection initiated by ingestion of the egg stage triggers a rapid and robust protective immune response. Antibodies of the IgE class may also play a role in protec- 366 the Cestodes to controlling H. In treating individuals, especially small children, it is sometimes difficult to achieve a cure, due to autoinfection. Rodent reservoir hosts contaminate the environment and, in many situations, controlling their populations has reduced the incidence of infection, but more often than not, rodent populations cannot be reduced. Hymenolepis diminuta (Rudolphi 1819) Introduction Hymenolepis dimunuta is found throughout the world and has many reservoir hosts, including dogs, cats, and many species of rodents. The immature worm attaches to the intestinal wall with the aid of four suckers on its scolex. Gravid proglottids detach from the strobila and disintegrate in the small intestine. When eggs were experimentally fed to Tenebrio molitor larvae, some eggs passed through their gut tract, and were incorporated within the fecal pellets. There, they remained infective for 48 hours, allowing infection to spread among the remaining insect larvae. Beetle to beetle transmission may be even more significant than cycles involving vertebrate intermediates, and may serve to free this parasite from reliance on the presence of an additional host to complete its life cycle. Usually there are no clinical symptoms attributable to this infection, although infections with more than ten worms have been associated with abdominal pain, anorexia, and irritability. Occasionally, whole segments of adult worms, which can be identified directly, are also passed in the feces. Community efforts are aimed at curtailing contamination of food, especially whole grains and processed flour, by insects that could harbor the intermediate stage of the worm. Dipylidium caninum (Linnaeus 1758) Introduction Dipylidium caninum lives in the lumen of the small intestine of the dog, cat, fox, hyena, and occasionally human. The name of the genus is of Greek origin, and means "double pore" or "double opening. Eradication of fleas in pets and treating infected animals with niclosamide greatly reduce the chances of human infection. Journal of the Medical Association of Thailand = Chotmaihet thangphaet 2000, 83 (9), 1035-8. Experimental verification of autoinfection from cysticercoids of Hymenolepis nana in the white mouse. Ross eventually succeeded in making the connection between mosquitoes and the transmission of malaria, using birds as hosts and culicine mosquitoes as the arthropod vector in his experiments. When Ross then tried to show the same was also true for the transmission of human malaria, he failed, since only anopheline mosquitoes are vectors for all of the human malarias. Grassi and colleagues in Italy, at around the same time that Ross published his original findings, carried out the seminal work on human malaria transmission. Ross was gifted in mathematics and developed epidemiological models for describing the ways malaria epidemics behave. Sheep and other herbivores serve as intermediate hosts, acquiring infection by eating embryonated eggs that contaminate grazing pastures. Humans are also susceptible to the juvenile stage of the parasite, which may develop to a large, fluid-filled cyst, often exceeding 40 cm in diameter. Although both Echinococcus granulosus and Echinococcus multilocularis cause infection in humans, 95% of the cases of human disease are due to Echinococcus granulosus. Eurasia, especially the Russian Federation and Central Asia and China (including Tibet), Mediterranean countries (especially, Turkey, Lebanon and Syria), North and East Africa (especially, Egypt, Sudan, and Kenya), and Australia have the highest prevalence. Juvenile Tapeworm Infections of Humans 375 reindeer is associated with this infection. Multiple infection is the rule, with hundreds to thousands of adult worms occupying the greater portion of the upper half of the small intestine. Each intermediate host species (sheep, cattle, pig, and horse) seems to have evolved a separate, genetically definable strain of parasite. The fluid is under pressure, and the wall, while substantial, can rupture if severely traumatized. The diameter of the mature outer cyst varies from 2 to 20 cm, and sometimes is even larger. Dogs do not seem to become ill from the effects of even heavy intestinal infections, which may exceed a million adult worms. Cellular and Molecular Pathogenesis There is minimal host reaction to a living hydatid cyst, but little is known regarding the nature of the immune responses directed at the parasite, and the antigens it secretes into the cyst fluid. Evidence suggests that the production of immunosuppressive substances by the parasite suppress host responses for the 376 the Cestodes life of the cyst. This feature might provide a mechanism by which intermediate hosts, including humans, control the number of oncospheres that ultimately develop into hydatid cysts. Hydatid disease develops as the result of rapid growth of the cyst (or cysts), and subsequent expansion of the cyst wall. Histological section of an hydatid cyst with capsules filled with protoscolices (arrows) of Echinococcus granulosus. Radiogram of upper body showing elevation in right lobe of liver due to a large hydatid cyst. Even a few cells from the germinal membrane can re-establish an entire hydatid cyst, as each cell of the germinal membrane has a stem cell-like ability to reproduce a full hydatid cyst. Avoiding host contact with hydatid cyst contents and sterilizing the germinal layer is essential as the mortality rate of 2-4% usually seen in cases of cystic echinococcus may be increased if patients are improperly treated. Patients may describe the sputum they produce as salty if it is due to a leaking hydatid cyst in the lungs. Rupture of a cyst, wherever it is lodged, may occur even after relatively minor blunt trauma, and often leads to an allergic reaction. It may be mild and limited to urticaria, or may take the form of anaphylactic shock, requiring immediate intervention. Most patients with the northern variant of echinococcosis have asymptomatic lung cysts that are usually detected on chest radiographs obtained for other reasons. Diagnosis An accurate case history is essential to the diagnosis of hydatid disease. Serodiagnosis is also useful both for primary diagnosis and following patients during and after their medical or surgical management. Efforts are underway to develop tests that detect circulating echinococcus antigens. This is usually the case in long-term infections, in which all cells within the cyst have died, and the only remaining evidence of infection are the hooklets and portions of the acellular, laminate outer membrane of the cyst wall. Treatment Treatment of hydatid disease is driven by cyst size, location, and stage. Radiogram of a liver infected with multiple hydatid cysts of Echinococcus granulosus. The organs containing hydatid cysts are occasionally fed to their dogs, thus completing the life cycle. Treatment of patients with hydatid cysts often requires both surgical and medical interventions. Historically, a variety of strategies have been devised to prevent or minimize spillage of cyst contents. This includes preoperative use of anthelminthic drugs and the use of protoscolicidal compounds such as 95% ethanol, hypertonic saline and cetrimide. Reversible liver toxicity has been reported with prolonged therapy with albendazole. Organs from sheep containing hydatid cysts are routinely fed to the numerous dogs that frequent these unsanitary, unsupervised rural establishments. More recently laproscopic surgery has emerged as a viable alternative for surgical treatment. Chemotherapy can result in cyst regression or collapse, although prolonged courses of therapy are usually required. In Iceland, mass slaughter of infected sheep and dogs led to the total eradication of the disease. This infection is prevalent among fur trappers and others whose occupations bring them in close contact with wild foxes and populations with close contact with dogs that regularly feed on infected rodents. Alveolar echinococcosis has emerged to the point where it is endemic in the northern hemisphere including western Europe, where it is considered a re-emerging disease due, in part, to the banning of fox hunting in a number of Common Market countries. In North America, human infections have been reported from Alaska and in the upper Midwest and Northern Plains along the Canadian border. The oncosphere hatches in the small intestine and invades the liver by the hematogenous route. It transforms, and then grows into an alveolar type of cyst, characterized by numerous daughter cysts, as compared to hydatid cysts, that grow as a single membrane-bounded unit. Foxes and dogs ingest infected liver containing numerous protoscolices, which leads to infection with the adult worm, thereby completing the life cycle. The initial exposure often occurs during childhood, but the disease has been recognized mainly in older adults. The membrane proliferates indefinitely and causes progressive destruction of the liver parenchyma, which can lead to hepatic failure. If untreated, the mortality of clinically apparent disease can be as high as 50-75%. Trappers and those involved in animal husbandry in the fur industry should be educated to exercise caution when handling carcasses and processing furs. The infective stage, known as a tetrathyridium, develops in the second intermediate host. Tetrathyridia are usually about 1 cm long and contain an invaginated scolex with four suckers. Humans acquire the parasite by eating the tetrathyridia, which can develop to an adult worm in the gut, or migrate to the peritoneal cavity. Cases of mesocestoides infection have been described in the United States, but the mode of acquisition is not known. Cases of sparganosis have been reported from Southeast Asia, Japan, China, especially on the island of Hainan, Africa, Italy, and the United States. Juvenile Tapeworm Infections of Humans 383 released free-swimming coracidia are eaten by copepods. The parasites then develop into the procercoid stage that is infectious for second intermediate hosts; amphibians, fish, reptiles, and birds. These animals ingest the infected copepods, releasing the procercoids that penetrate the intestinal tract and develop to the plerocercoid stage in muscle tissue. This stage is infective for definitive hosts; warm-blooded predator species that prey on these infected cold-blooded animals. This practice is very common in some areas of the world, particularly on the island of Hainan, where over 30% of the frogs harbor the juvenile stage of spirometra. As with any other therapy, the use of coldblooded vertebrate skin as a poultice can have unwanted "side effects. The plerocercoid stage can migrate out of the poultice and into the subcutaneous tissues, stimulated by the rise in temperature from the human host. If the poultice is placed over an open wound, or the eye, the immature parasite may enter the site. Larvae often migrate behind the eye, and even into the brain via the optic nerve, making easy removal of the parasite impossible. Subcutaneous lesions are often removed by surgery, as treatment with antihelminthic therapy such as with praziquantil is associated with limited success.

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