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Parasitic diseases are very common on a worldwide basis. In certain cases radiological features are of importance both for primary diagnosis and for detection of complications of infestation. This review concentrates on parasitic diseases of radiological interest.
Parasitic diseases which during their course in the host switch the immune system from a T helper 1 to a T helper 2 response may be detrimental to the host, contributing to granuloma formation, eosinophilia, hyper-IgE, and increased susceptibility to bacterial and fungal infections. Patients and animals with acute schistosomiasis and hyper-IgE in their serum develop pyogenic liver abscess in the presence of bacteremia caused by Staphylococcus aureus. The Salmonella-S. mansoni association has also been well documented. The association of tropical pyomyositis (pyogenic muscle abscess) and pyogenic liver abscess with Toxocara infection has recently been described in the same context. In tropical countries that may be an interesting explanation for the great morbidity of bacterial diseases. If the association of parasitic infections and pyogenic abscesses and/or fungal diseases are confirmed, there will be a strong case in favor of universal treatment for parasitic diseases to prevent or decrease the morbidity of superinfection with bacteria and fungi.
Parasitic infections present a paradoxal immune situation: the host develops a normal immune response against the parasite but, in general, this response does not result in its elimination. An equilibrium is established which is essential to the survival of the parasite, involving a diminished state of the host, but not necessarily lethal. The mechanisms that allow the parasite to escape the immune defence are varied and include antigenic variation, mimetism, anatomical seclusion, immunomodulation, etc.
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Parasitic infestation can induce a variety of rheumatic syndromes as a result of infiltration of musculoskeletal structures by parasites or an immune mediated mechanism. Parasite-induced symptoms should be considered when arthritis, enthesitis, myositis, or vasculitis develop in patients residing in endemic areas and in certain subsets of the population of developed countries, for example, migrants, travelers, and immunocompromised individuals. Diagnosis is based on the demonstration of infection with a pathogenic parasite, lack of response to anti-inflammatory agents, and improvement following antiparasitic therapy. Treatment consists of erradication of the parasite.
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Intestinal parasites are Giardia lamblia, Cryptosporidium parvum, Entamoeba histolytica, hookworms, ascaris, tape worms and others. As to organ parasites, their life-threatening courses are pointed out: amebiasis in the intestine, liver, lung and brain, toxoplasmosis in the brain, lung and heart muscle, including the danger for the child of a pregnant woman with an acute infection, West African sleeping sickness with encephalitis, the East African form with polyserositis, South American Chagas' disease with intestinal and myocardial involvement, visceral leishmaniasis Kala Azar, the filariasis Onchocerca volvulus with threatening blindness, the dog tapeworm with cysts and Echinococcus multilocularis with carcinoma-like infiltration of the liver and other organs, cysticercosis of the brain, eye and muscle tissue; partly generalizing parasitoses in immuno-suppressed including AIDS patients, finally skin parasites as causes of disease (e.g. scabies), and as potential carriers of pathogens.
The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, there are many confounding factors that may alter the results of an electrophoretic study and may possibly allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Measured enzyme activities can also be affected significantly. Parasites, disease and pollution can affect levels of enzyme activity, and electrophoretic results can be affected both quantitatively and qualitatively. Blood serum is particularly vulnerable to variation to variation due to disease, pollution or parasites because damaged tissues may release tissue-specific enzymes into the bloodstream. Capture, handling, chemical treatments, bacteria, natural toxins and consumed food may also contribute to variation. Potential pollution impacts at specimen collection sites should be investigated, and study organisms should be inspected and/or treated for detection and elimination of parasites and disease.
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Parasitic disease is still important subject in the field of infectious diseases in Korea considering it's number and morbidity. Recently there was conspicuous reduction of parasitic disease in terms of soil-transmitted nematodiasis, but parasitism affecting organs other than intestinal tract is still a considerable problem. This survey covers the parasitic diseases cross-sectioned at a pathology laboratory of a referral hospital, trying to elucidate the significance of its relative frequency and also to describe some histopathological changes made by different parasites. Entire pathological materials of parasitic diseases, that were referred, examined and confirmed at the Department of Pathology, Seoul National University Hospital from 1968 to 1987, were used for the study. There was a total of 594 cases of tissue parasitic diseases. This number accounted for 0.33 per cent of total accessions of surgical pathology. There occurred average 30 cases of tissue parasitic disease each year at this Hospital. Protozoal diseases were constituted of 15 cases of amebiasis, 7 cases of leishmaniasis (imported) and 5 cases of Pneumocystis carinii infections. Among helminthic infections cysticercosis was the most common (425 cases), and was followed by paragonimiasis (35 cases), sparganosis (31 cases), clonorchiasis (32 cases) and ascariasis (16 cases). In addition there were 4 cases of anisakiasis, 2 cases of fascioliasis, 2 cases of echinococcosis (imported) and a case of strongyloidiasis and a case of metagonimiasis respectively. It is emphasized that imported parasitic diseases such as leishmaniasis and hydatid disease become steadily found nowadays. Schistosomiasis is another possible imported disease, but not found in this series. And certain cestodiasis particularly cysticercosis and sparganosis should be the subjects of epidemiologic re-evaluation in view of steady occurrence of their morbidity.
Clinical and laboratory studies were made in 2259 persons by using serological assays, including cultural and bacterioscopic assays in 1824 and 363 persons, respectively, in order to indicate Trichomonas infection among men, women, and 2-15-year-old children who had chronic inflammation of the urogenital system, as well as among children aged 2 months to 16 years who had a severe somatic disease. Parasitic cenoses of the urogenital tract were studied in women with trichomoniasis and reproductive dysfunction. Trichomonas invasion is an etiological factor of inflammatory small pelvic diseases, chronic prostatitis, reproductive dysfunction in males and females. Furthermore, trichomoniasis is an essential factor, that predisposes to recurrent viral infections: genital herpes and pointed condyloma, and substantially increases the risk of birth of babies with clinical manifestations of intrauterine infection. According to the studies, a laboratory diagnosis of trichomoniasis should be made by cultural assay due to the low sensitivity of bacterioscopy by sampling a biological material from females in the periovulatory period that corresponds to the hyperestrogenicity, which substantially increases the number of isolated cultures and characterizes the depth of integration of metabolic processes of a parasite and its host.
Parasitic diseases are primarily diseases of poverty. At serious risk are individuals, communities and countries least able to afford the costs of treatment or prevention. In turn, economic development projects which aim to increase income levels may lead to negative results because of increased transmission of parasitic diseases often results. In attempting to analyse the economic consequences of parasitic diseases and the economics of their control, economists have usually relied on the tools of cost-benefit analysis, cost-effectiveness analysis and financial analysis. These efforts are briefly reviewed in the paper. The results have been subject to considerable criticism because of conceptual and methodological problems. For example, most studies have not taken into account the epidemiology and natural history of the disease in estimating the associated economic losses, thereby leading to inappropriate conclusions. The UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases through its Social and Economic Research Scientific Working Group (SER-SWG) is promoting research on the economics of parasitic diseases. In an attempt to improve the usefulness and reliability of such studies, conceptual and methodological approaches have been suggested which are reported on here. To improve the research design of these projects, a conceptual framework is proposed which consists of four components: (1) baseline social, cultural and economic conditions influencing disease transmission; (2) resources already invested in the health system and investments in other related sectors such as agriculture, housing, water supply and sanitation; (3) health consequences resulting from (1) and (2); and (4) social and economic consequences resulting from (3). A key concern in relation to the framework is to determine the most useful basis for linking results from studies of one component to another so as to analyse more systematically the impacts of disease on individuals and society. Such studies are inherently interdisciplinary and close collaboration of economists with medical scientists and disease control programme staff is needed to ensure completeness and reliability of input data and results. Results from these studies could be used to inform national decision-makers about the social and economic consequences of the parasitic diseases and their control and, thus, should strengthen support for increased investment to reduce the parasitic disease burden in developing countries.
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Diagnosis of parasitic diseases requires highly sensitive and specific tests. In many cases the identification of parasites concerns their epidemiology and it is important to distinguish between species and subspecies. Conventional techniques including serology and microscopy do not always meet these requirements. The principle of nucleic acid probes is that a specific sequence of the parasite's DNA is isolated and used in a hybridisation assay to identify homologous parasite DNA from infected material. Since DNA normally remains the same during every stage of the parasite's life cycle this technique has many applications. The use of DNA diagnostics in the identification and differentiation of certain animal parasites is discussed.