4 results
195 - Intestinal roundworms
- from Part XXIV - Specific organisms: parasites
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- By Kathryn N. Suh, University of Ottawa, Jay S. Keystone, University of Toronto
- Edited by David Schlossberg, Temple University, Philadelphia
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- Book:
- Clinical Infectious Disease
- Published online:
- 05 April 2015
- Print publication:
- 23 April 2015, pp 1250-1257
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Summary
Nematodes (roundworms) are the most common parasites infecting humans worldwide. Of almost half a million species of roundworms, approximately 60 are known to be pathogenic to humans. Among the most prevalent human infections are those due to the intestinal (lumen-dwelling) nematodes. Ascaris lumbricoides and Trichuris trichiura each infect over 1 billion people worldwide; hookworms (Ancylostoma duodenale and Necator americanus) infect almost the same number. Other important nematodes of humans include Strongyloides stercoralis and Enterobius vermicularis. Coinfection, in particular with A. lumbricoides and T. trichiura, is common.
Ascaris lumbricoides, hookworm, and T. trichiura, collectively referred to as geohelminths (or soil-transmitted helminths), share the requirement for eggs or larvae to mature in soil in order to be infective to humans. Due to this obligate soil stage of maturation, these parasites cannot be transmitted from person to person. In contrast, S. stercoralis is able to complete its entire life cycle within the human host, and like E. vermicularis, both person-to-person transmission and autoinfection can occur.
The majority of geohelminthic infections are asymptomatic and associated with low worm burdens, whereas the minority (15%–35%) of infected individuals harbor the majority of the worm burden and suffer from more intense symptoms. Geohelminthic infections are important contributors to growth retardation and cognitive delay in children, but conclusively proving the benefit of large-scale anthelminthic therapy in endemic areas is challenging for a number of reasons. Geohelminths are unaffected by host immune responses, leading to chronic infection if untreated, although the natural history of such infections (excluding hookworm) is usually one of decreasing worm burden over time; even with treatment, however, reinfection is common.
114 - Advice for Travelers
- from Part XVI - Travel and Recreation
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- By Phyllis E. Kozarsky, Emory University School of Medicine, Jay S. Keystone, University of Toronto
- Edited by David Schlossberg
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- Book:
- Clinical Infectious Disease
- Published online:
- 05 March 2013
- Print publication:
- 12 May 2008, pp 825-832
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Summary
There are more than 700 million international travelers annually and despite tragic events such as 9/11 or emerging disease epidemics such as severe acute respiratory syndrome (SARS), it appears that travel will continue to grow as one of the major “businesses” of the world. Indeed, travel is becoming more exotic and adventuresome, leaving no space on Earth untouched. However, studies continue to show that 50% to 75% of short-term travelers, particularly to the tropics or subtropics, develop some health impairment. Fortunately, most problems are minor, with only 5% requiring medical attention and fewer than 1% requiring hospitalization. Valuable sources of information for travel health advisors are found in Table 114.1.
All travelers should be encouraged to carry a travel health kit, which should always remain with the traveler and never be stowed with baggage (except for those items that can not be taken in the carry-on luggage) (Table 114.2). In addition, travelers should make sure that they are aware of a health care provider at home should they develop illness. Those with more serious chronic diseases will want to make sure they have additional health insurance to cover them in the event of illness abroad and should consider purchasing medical evacuation insurance (as well as trip cancellation insurance). All primary care providers should make it a habit of asking their patients who see them for routine examinations whether they will be traveling.
193 - Intestinal Roundworms
- from Part XXIV - Specific Organisms – Parasites
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- By Kathryn N. Suh, University of Ottawa, Jay S. Keystone, University of Toronto
- Edited by David Schlossberg
-
- Book:
- Clinical Infectious Disease
- Published online:
- 05 March 2013
- Print publication:
- 12 May 2008, pp 1335-1342
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- Chapter
- Export citation
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Summary
Nematodes (roundworms) are the most common parasites infecting humans worldwide. Of almost half a million species of roundworms, approximately 60 are known to be pathogenic to humans. Among the most prevalent human infections are those due to the intestinal (lumen-dwelling) nematodes. Ascaris lumbricoides and Trichuris trichiura each infect over 1 billion people worldwide; hookworm (Ancylostoma duodenale and Necator americanus) infects almost the same number. Other important nematodes of humans include Strongyloides stercoralis and Enterobius vermicularis. Co-infection, in particular with A. lumbricoides and T. trichiura, is common.
Ascaris lumbricoides, hookworm, and T. trichiura, collectively referred to as geohelminths (or soil-transmitted helminths), share the requirement for eggs or larvae to mature in soil in order to be infective to humans. The majority of infections caused by these species are asymptomatic and associated with low worm burdens, whereas the minority (15%–35%) of infected individuals harbor the majority of the worm burden and suffer from more intense symptoms. The natural history of geohelminthic infections is usually one of decreasing worm burden over time. Due to the obligate soil stage of maturation, these parasites cannot be transmitted from person to person. In contrast, S. strongyloides is able to complete its entire life cycle within the human host, and like E. vermicularis, both person-to-person transmission and autoinfection can occur.
198 - Malaria: Treatment and Prophylaxis
- from Part XXIV - Specific Organisms – Parasites
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- By Phyllis E. Kozarsky, Emory University School of Medicine, Deborah J. Nicolls, Emory University School of Medicine, Jay S. Keystone, University of Toronto
- Edited by David Schlossberg
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- Book:
- Clinical Infectious Disease
- Published online:
- 05 March 2013
- Print publication:
- 12 May 2008, pp 1371-1380
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Summary
Malaria is the most important parasitic infection that causes disease in humans. More than a million persons, mostly children, die each year from malaria. It is also one of the most common causes of fever in returned travelers and recent immigrants from malaria-endemic areas.
Malaria is primarily caused by infection with 1 of 4 Plasmodium species: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae. Occasionally human infection with a monkey malaria parasite, such as P. knowlesi, occurs. Treating malaria appropriately requires knowledge of the infecting species, the likely location in which the infection was acquired, and the geographic patterns of drug resistance. Figure 198.1 shows the worldwide distribution of malaria. When there is any doubt about the infecting species, the clinician should treat for the worst-case scenario, chloroquineresistant P. falciparum (CRPF) malaria. Malaria caused by P. vivax and P. ovale may leave dormant forms, hypnozoites, in the liver after the blood phase has been eradicated. Thus, treatment of these two infections requires eradication of the erythrocytic phase followed by a second drug to eradicate the liver phase (terminal prophylaxis).
CLINICAL ASPECTS
Because death from malaria can occur within several days of the onset of symptoms, it is necessary to consider a febrile illness in a patient from a malarious endemic area to be a medical emergency. This is particularly so when symptoms begin within the first 2 months of arrival because more than 90% of those with malaria caused by P. falciparum present within this time.