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Antibody detection can be useful to indicate schistosome infection in people who have traveled to areas where schistosomiasis is common and in whom eggs cannot be demonstrated in fecal or urine specimens. Test sensitivity and specificity vary widely among the many tests reported for the serologic diagnosis of schistosomiasis and are dependent on both the type of antigen preparations used (crude, purified, adult worm, egg, cercarial) and the test procedure.
At CDC, a combination of tests with purified adult worm antigens is used for antibody detection. All serum specimens are tested by FAST-ELISA using "S. mansoni" adult microsomal antigen (MAMA). A positive reaction (greater than 9 units/µl serum) indicates infection with "Schistosoma" species. Sensitivity for "S. mansoni" infection is 99 percent, 95 percent for "S. haematobium" infection, and less than 50 percent for "S. japonicum" infection. Specificity of this assay for detecting schistosome infection is 99 percent. Because test sensitivity with the FAST-ELISA is reduced for species other than "S. mansoni", immunoblots of the species appropriate to the patient's travel history are also tested to ensure detection of "S. haematobium" and "S. japonicum" infections. Immunoblots with adult worm microsomal antigens are species-specific and so a positive reaction indicates the infecting species. The presence of antibody is indicative only of schistosome infection at some time and cannot be correlated with clinical status, worm burden, egg production, or prognosis. Where a person has traveled can help determine what "Schistosoma" species to test for by immunoblot.
In 2005, a field evaluation of a novel handheld microscope was undertaken in Uganda for the diagnosis of intestinal schistosomiasis by a team led by Russell Stothard from the Natural History Museum of London, working with the Schistosomiasis Control Initiative, London.
Diagnosis of infection is confirmed by the identification of eggs in stools. Eggs of "S. mansoni" are approximately 140 by 60 µm in size, and have a lateral spine. The diagnosis is improved by the use of the Kato-Katz technique (a semi-quantitative stool examination technique). Other methods that can be used are enzyme-linked immunosorbent assay (ELISA), circumoval precipitation test, and alkaline phosphatase immunoassay.
Microscopic identification of eggs in stool or urine is the most practical method for diagnosis. Stool examination should be performed when infection with "S. mansoni" or "S. japonicum" is suspected, and urine examination should be performed if "S. haematobium" is suspected. Eggs can be present in the stool in infections with all "Schistosoma" species. The examination can be performed on a simple smear (1 to 2 mg of fecal material). Since eggs may be passed intermittently or in small amounts, their detection will be enhanced by repeated examinations and/or concentration procedures. In addition, for field surveys and investigational purposes, the egg output can be quantified by using the Kato-Katz technique (20 to 50 mg of fecal material) or the Ritchie technique. Eggs can be found in the urine in infections with "S. haematobium" (recommended time for collection: between noon and 3 PM) and with "S. japonicum". Quantification is possible by using filtration through a nucleopore filter membrane of a standard volume of urine followed by egg counts on the membrane. Tissue biopsy (rectal biopsy for all species and biopsy of the bladder for "S. haematobium") may demonstrate eggs when stool or urine examinations are negative.
For medical purposes, the exact number of helminth eggs is less important and therefore most diagnoses are made simply by identifying the appearance of the worm or eggs in feces. Due to the large quantity of eggs laid, physicians can diagnose using only one or two fecal smears. The Kato technique (also called the Kato-Katz technique) is a laboratory method for preparing human stool samples prior to searching for parasite eggs. Eggs per gram is a laboratory test that determines the number of eggs per gram of feces in patients suspected of having a parasitological infection, such as schistosomiasis.
For the purpose of setting treatment standards and reuse legislation, it is important to be able to determine the amount of helminth eggs in an environmental sample with some accuracy. The detection of viable helminth eggs in samples of wastewater, sludge or fresh feces (as a diagnostic tool for the infection helminthiasis) is not straight forward. In fact, many laboratories in developing countries lack the right equipment or skilled staff required to do so. An important step in the analytical methods is usually the concentration of the eggs in the sample, especially in the case of wastewater samples. A concentration step may not be required in samples of dried feces, e.g. samples collected from urine-diverting dry toilets.
Specific helminths can be identified through microscopic examination of their eggs (ova) found in faecal samples. The number of eggs is measured in units of eggs per gram. However, it does not quantify mixed infections, and in practice, is inaccurate for quantifying the eggs of schistosomes and soil-transmitted helmiths. Sophisticated tests such as serological assays, antigen tests, and molecular diagnosis are also available; however, they are time-consuming, expensive and not always reliable.
Microscopic demonstration of the large typically shaped oocysts is the basis for diagnosis. Because the oocysts may be passed in small amounts and intermittently, repeated stool examinations and concentration procedures are recommended. If stool examinations are negative, examination of duodenal specimens by biopsy or string test (Enterotest) may be needed. The oocysts can be visualized on wet mounts by microscopy with bright-field, differential interference contrast (DIC), and epifluorescence. They can also be stained by modified acid-fast stain.
Typical laboratory analyses include:
- Microscopy
- Morphologic comparison with other intestinal parasites
- Bench aids for "Isospora"
Major groups of parasites include protozoans (organisms having only one cell) and parasitic worms (helminths). Of these, protozoans, including cryptosporidium, microsporidia, and isospora, are most common in HIV-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.
Due to the wide variety of intestinal parasites, a description of the symptoms rarely is sufficient for diagnosis. Instead, medical personnel use one of two common tests: they search stool samples for the parasites, or apply an adhesive the anus to search for eggs.
In regions where helminthiasis is common, mass deworming treatments may be performed, particularly among school-age children, who are a high-risk group. Most of these initiatives are undertaken by the World Health Organization (WHO) with positive outcomes in many regions. Deworming programs can improve school attendance by 25 percent. Although deworming improves the health of an individual, outcomes from mass deworming campaigns, such as reduced deaths or increases in cognitive ability, nutritional benefits, physical growth, and performance, are uncertain or not apparent.
Avoiding food or water that may be contaminated with stool can help prevent the infection of "Cystoisospora" (Isosporiasis). Good hand-washing, and personal-hygiene practices should be used as well. One should wash their hands with soap and warm water after using the toilet, changing diapers, and before handling food (CDC.gov). It is also important to teach children the importance of washing their hands, and how to properly wash their hands.
Biotechnology companies in the developing world have targeted neglected tropical diseases due to need to improve global health.
Mass drug administration is considered a possible method for eradication, especially for lymphatic filariasis, onchocerciasis, and trachoma, although drug resistance is a potential problem. According to Fenwick, Pfizer donated 70 million doses of drugs in 2011 to eliminate trachoma through the International Trachoma Initiative. Merck has helped The African Programme for the Control of Onchocerciasis (APOC) and Oncho Elimination Programme for the Americas to greatly diminished the effect of Onchocerciasis by donating ivermectin. Merck KGaA pledged to give 200 million tablets of praziquantel over 10 years, the only cure for schistosomiasis. GlaxoSmithKline has donated two billion tablets of medicine for lymphatic filariasis and pledged 400 million deworming tablets per year for five years in 2010. Johnson & Johnson has pledged 200 million deworming tablets per year. Novartis has pledged leprosy treatment, EISAI pledged two billion tablets to help treat lymphatic filariasis.
The medical diagnosis is established by finding eggs of "Opisthorchis viverrini" in feces using the Kato technique.
An antigen 89 kDa of "Opisthorchis viverrini" can be detected by ELISA test.
A PCR test capable of amplifying a segment of the internal transcribed spacer region of ribosomal DNA for the opisthorchiid and heterophyid flukes eggs taken directly from faeces was developed and evaluated in a rural community in central Thailand. The lowest quantity of DNA that could be amplified from individual adults of "Opisthorchis viverrini" was estimated to 0.6 pg.
Inclusion of NTDs into initiatives for malaria, HIV/AIDS, and tuberculosis, as well as integration of NTD treatment programs, may have advantages given the strong link between these diseases and NTDs. Some neglected tropical diseases share common vectors (sandflies, black flies, and mosquitos). Both medicinal and vector control efforts may be combined.
A four-drug rapid-impact package has been proposed for widespread proliferation. Administration may be made more efficient by targeting multiple diseases at once, rather than separating treatment and adding work to community workers. This package is estimated to cost US$0.40 per patient. When compared to stand-alone treatment, the savings are estimated to be 26–47%. While more research must be done in order to understand how NTDs and other diseases interact in both the vector and the human stages, safety assessments have so far produced positive results.
Many neglected tropical diseases and other prevalent diseases share common vectors, creating another opportunity for treatment and control integration. One such example of this is malaria and lymphatic filariasis. Both diseases are transmitted by the same or related mosquito vectors. Vector control, through the distribution of insecticide treated nets, reduces the human contact with a wide variety of disease vectors. Integrated vector control may also alleviate pressure on mass drug administration, especially with respect to rapidly evolving drug resistance. Combining vector control and mass drug administration deemphasizes both, making each less susceptible to resistance evolution.
Effective prevention could be readily achieved by persuading people to consume cooked fish (via education programs), but the ancient cultural custom to consume raw, undercooked or freshly pickled fish persists in endemic areas. One community health program, known as the "Lawa" model, has achieved success in the Lawa Lakes region south of Khon Kaen. Currently, there is no effective chemotherapy to combat cholangiocarcinoma, such that intervention strategies need to rely on the prevention or treatment of liver fluke infection/disease.
Cooking or deep-freezing (-20 °C for 7 days) of food made of fish is sure method of prevention. Methods for prevention of "Opisthorchis viverrini" in aquaculture fish ponds were proposed by Khamboonruang et al. (1997).
Some of the strategies for controlling tropical diseases include:
- Draining wetlands to reduce populations of insects and other vectors, or introducing natural predators of the vectors.
- The application of insecticides and/or insect repellents) to strategic surfaces such as clothing, skin, buildings, insect habitats, and bed nets.
- The use of a mosquito net over a bed (also known as a "bed net") to reduce nighttime transmission, since certain species of tropical mosquitoes feed mainly at night.
- Use of water wells, and/or water filtration, water filters, or water treatment with water tablets to produce drinking water free of parasites.
- Sanitation to prevent transmission through human waste.
- In situations where vectors (such as mosquitoes) have become more numerous as a result of human activity, a careful investigation can provide clues: for example, open dumps can contain stagnant water that encourage disease vectors to breed. Eliminating these dumps can address the problem. An education campaign can yield significant benefits at low cost.
- Development and use of vaccines to promote disease immunity.
- Pharmacologic pre-exposure prophylaxis (to prevent disease before exposure to the environment and/or vector).
- Pharmacologic post-exposure prophylaxis (to prevent disease after exposure to the environment and/or vector).
- Pharmacologic treatment (to treat disease after infection or infestation).
- Assisting with economic development in endemic regions. For example, by providing microloans to enable investments in more efficient and productive agriculture. This in turn can help subsistence farming to become more profitable, and these profits can be used by local populations for disease prevention and treatment, with the added benefit of reducing the poverty rate.
- Hospital for Tropical Diseases
- Tropical medicine
- Infectious disease
- Neglected diseases
- List of epidemics
- Waterborne diseases
- Globalization and disease
Waterborne diseases can have a significant impact on the economy, locally as well as internationally. People who are infected by a waterborne disease are usually confronted with related costs and not seldom with a huge financial burden. This is especially the case in less developed countries. The financial losses are mostly caused by e.g. costs for medical treatment and medication, costs for transport, special food, and by the loss of manpower. Many families must even sell their land to pay for treatment in a proper hospital. On average, a family spends about 10% of the monthly households income per person infected.
Waterborne diseases are conditions caused by pathogenic micro-organisms that are transmitted in water. Disease can be spread while bathing, washing or drinking water, or by eating food exposed to infected water. Various forms of waterborne diarrheal disease are the most prominent examples, and affect children in developing countries most dramatically.
According to the World Health Organization, waterborne diseases account for an estimated 3.6% of the total DALY (disability- adjusted life year) global burden of disease, and cause about 1.5 million human deaths annually. The World Health Organization estimates that 58% of that burden, or 842,000 deaths per year, is attributable to a lack of safe drinking water supply, sanitation and hygiene (summarized as WASH).
Cultures of stool samples are examined to identify the organism causing dysentery. Usually, several samples must be obtained due to the number of amoebae, which changes daily. Blood tests can be used to measure abnormalities in the levels of essential minerals and salts.
Providing basic sanitation and safe drinking water and food is the key for controlling the disease. In developed countries, enteric fever rates decreased in the past when treatment of municipal water was introduced, human feces were excluded from food production, and pasteurization of dairy products began. In addition, children and adults should be carefully educated about personal hygiene. This would include careful handwashing after defecation and sexual contact, before preparing or eating food, and especially the sanitary disposal of feces. Food handlers should be educated in personal hygiene prior to handling food or utensils and equipment. Infected individuals should be advised to avoid food preparation. Sexually active people should be educated about the risks of sexual practices that permit fecal-oral contact.
Those who travel to countries with poor sanitation should receive a live attenuated typhoid vaccine—Ty21a (Vivotif), which, in addition to the protection against typhoid fever, and may provide some protection against paratyphoid fever caused by the "S. enterica" serotypes A and B. In particular, a reanalysis of data from a trial conducted in Chile showed the Ty21a vaccine was 49% effective (95% CI: 8–73%) in preventing paratyphoid fever caused by the serotype B. Evidence from a study of international travelers in Israel also indicates the vaccine may prevent a fraction of infections by the serotype A, although no trial confirms this. This cross-protection by a typhoid vaccine is most likely due to O antigens shared between different "S. enterica" serotypes.
Exclusion from work and social activities should be considered for symptomatic, and asymptomatic, people who are food handlers, healthcare/daycare staff who are involved in patient care and/or child care, children attending unsanitary daycare centers, and older children who are unable to implement good standards of personal hygiene. The exclusion applies until two consecutive stool specimens are taken from the infected patient and are reported negative.
The mouth, skin, and lips may appear dry due to dehydration. Lower abdominal tenderness may also be present.
Additional neglected tropical diseases include:
Some tropical diseases are very rare, but may occur in sudden epidemics, such as the Ebola hemorrhagic fever, Lassa fever and the Marburg virus. There are hundreds of different tropical diseases which are less known or rarer, but that, nonetheless, have importance for public health.
More than 300 million people worldwide have asthma. The rate of asthma increases as countries become more urbanized and in many parts of the world those who develop asthma do not have access to medication and medical care. Within the United States, African Americans and Latinos are four times more likely to suffer from severe asthma than whites. The disease is closely tied to poverty and poor living conditions. Asthma is also prevalent in children in low income countries. Homes with roaches and mice, as well as mold and mildew put children at risk for developing asthma as well as exposure to cigarette smoke.
Unlike many other Western countries, the mortality rate for asthma has steadily risen in the United States over the last two decades. Mortality rates for African American children due to asthma are also far higher than that of other racial groups. For African Americans, the rate of visits to the emergency room is 330 percent higher than their white counterparts. The hospitalization rate is 220 percent higher and the death rate is 190 percent higher. Among Hispanics, Puerto Ricans are disporpotionatly affected by asthma with a disease rate that is 113 percent higher than non-Hispanic Whites and 50 percent higher than non-Hispanic Blacks. Studies have shown that asthma morbidity and mortality are concentrated in inner city neighborhoods characterized by poverty and large minority populations and this affects both genders at all ages. Asthma continues to have an adverse effects on the health of the poor and school attendance rates among poor children. 10.5 million days of school are missed each year due to asthma.
Those diagnosed with Type A of the bacterial strain rarely die from it except in rare cases of severe intestinal complications. With proper testing and diagnosis, the mortality rate falls to less than 1%. Antibiotics such as azithromycin are particularly effective in treating the bacteria.
AIDS is a disease of the human immune system caused by the human immunodeficiency virus (HIV). Primary modes of HIV transmission in sub-Saharan Africa are sexual intercourse, mother-to-child transmission (vertical transmission), and through HIV-infected blood. Since rate of HIV transmission via heterosexual intercourse is so low, it is insufficient to cause AIDS disparities between countries. Critics of AIDS policies promoting safe sexual behaviors believe that these policies miss the biological mechanisms and social risk factors that contribute to the high HIV rates in poorer countries. In these developing countries, especially those in sub-Saharan Africa, certain health factors predispose the population to HIV infections.
Many of the countries in Sub-Saharan Africa are ravaged with poverty and many people live on less than one United States dollar a day. The poverty in these countries gives rise to many other factors that explain the high prevalence of AIDS. The poorest people in most African countries suffer from malnutrition, lack of access to clean water, and have improper sanitation. Because of a lack of clean water many people are plagued by intestinal parasites that significantly increase their chances of contracting HIV due to compromised immune system. Malaria, a disease still rampant in Africa also increases the risk of contracting HIV. These parasitic diseases, affect the body’s immune response to HIV, making people more susceptible to contracting the disease once exposed. Genital schistosomiasis, also prevalent in the topical areas of Sub-Saharan Africa and many countries worldwide, produces genital lesions and attract CD4 cells to the genital region which promotes HIV infection. All these factors contribute to the high rate of HIV in Sub-Saharan Africa. Many of the factors seen in Africa are also present in Latin America and the Caribbean and contribute to the high rates of infections seen in those regions. In the United States, poverty is a contributing factor to HIV infections. There is also a large racial disparity, with African Americans having a significantly higher rate of infection than their white counterparts.
Various strategies targeting the mollusc and avian hosts of schistosomes, have been used by lakeside residents in recreational areas of North America to deal with outbreaks of swimmer's itch. In Michigan, for decades, authorities used copper sulfate as a molluscicide to reduce snail host populations and thereby the incidence of swimmer's itch. The results with this agent have been inconclusive, possibly because:
- Snails become tolerant
- Local water chemistry reduces the molluscicide's efficacy
- Local currents diffuse it
- Adjacent snail populations repopulate a treated area
More importantly, perhaps, copper sulfate is toxic to more than just molluscs, and the effects of its use on aquatic ecosystems are not well understood.
Another method targeting the snail host, mechanical disturbance of snail habitat, has been also tried in some areas of North America and Lake Annecy in France, with promising results. Some work in Michigan suggests that administering praziquantel to hatchling waterfowl can reduce local swimmer's itch rates in humans. Work on schistosomiasis showed that water-resistant topical applications of the common insect repellent DEET prevented schistosomes from penetrating the skin of mice. Public education of risk factors, a good alternative to the aforementioned interventionist strategies, can also reduce human exposure to cercariae.