Presentation on theme: "CBio 4500/6500 Medical Parasitology Spring Semester 2010."— Presentation transcript:
CBio 4500/6500 Medical Parasitology Spring Semester 2010
Medical Parasitology zLectures on Tuesdays & Thursdays in the second period 9:30-10:45 a.m. zPlease initial the attendance sheet each class zYou may not miss more than 3 classes without detriment to your grade zThere will be 2 exams during the semester & a final covering the entire material (30%,30%, & 40%)
Medical Parasitology zThe class web site can be viewed at zThere is a link to this site through the UGA ELC site zThe site features the syllabus & schedule, lecture notes and links to further web resources z‘Voices from the Vanguard’ lecture series (once a month Tuesdays 6 pm in the Chapel)
Some book suggestions ( for some of these titles newer editions might be available) zRoberts & Janovy, Foundations of Parasitology, McGraw-Hill, 7th Ed zMarkell, John, Krotoski, Medical Parasitology,Saunders, 8th Ed zChiodine, Moody, Manser, Atlas of Medical Helminthology and Protozoology,Churchhill Livingstone, 4th Ed zPeters & Gilles, A Colour Atlas of Tropical Medicine & Parasitology, Wolfe, 3rd Ed zBogitsh, Carter, Oeltmann, Human Parasitology, Elsevier, 3rd Ed., 2005
Some book suggestions ( for some of these titles newer editions might be available)
websites zThere are thousands of web sites providing information and images on parasites, not all of them are as trustworthy as one could wish zTwo excellent sites to look for general information and material for visual illustration are: CDC Division of Parasitic Diseases, and WHO Tropical Disease Research Program (course website provides links)
Medical Parasitology zMedical Parasitology focuses on parasites which cause disease in humans. Parasites are also of great importance in veterinary medicine. zSeveral diseases falling it this field only occur in the tropics, but many parasite disease were very common in temperate climates until the beginning to mid 20th century zOverall there is a much stronger association with the level of sanitation and general public health than climate. Parasitic diseases are in their majority the diseases of the poor around the globe
Medical Parasitology GNP per capita (1995) $0-70 $ Malaria Index
Outline of the class zBrief introduction into concepts and terminology of: parasitology, vector biology, immunology & public health (4 lectures) zHelminth diseases (flukes, tape worms & round worms) (9 lectures) zDiseases caused by unicellular eukaryotes often referred to as protozoa (e.g. sleeping sickness & malaria) (13 lectures) zLectures will combine biology of the parasites and vectors, pathogenesis of the disease, treatment and prevention of diseases, and control efforts zWhere possible we will try to include cutting edge science with a focus on new molecular concepts
Parasitism - a way of life zParasite and Parasitism are ecological terms that define a way of life rather than a coherent and evolutionary related group of organisms zSymbiosis, Commensalism, Mutualism, Parasitism
Parasitism - a way of life zParasite and Parasitism are terms that define a way of life rather than a coherent and evolutionary related group of organisms zSymbiosis: “Any two organisms living in close association, commonly one living in or on the the body of the other, are symbiotic, as contrasted with free living.” De Bary 1879 zCommensalism: Sharing the table. One partner benefits but the other is not hurt. zMutualism: Both partners benefit. zParasitism: One partner (the parasit) harms or lives on the expense of the other (host).
Is the mighty lion a despicable parasite? zThe benefit in the relationship between lion and wildebeest seems highly skewed in favor of the lion
Who is a parasite? zParasites are usually much smaller than their hosts, they also do not kill before they eat.
Is a mosquito a parasite? zThe border between parasitism and micro- predation is blurry zParasites usually live in a very intimate relationship with their host depending on more than food from it zThe host is food source and more or less permanent habitat at the same time zMany parasites show strict specificity for a single host
Parasites are found in all groups of organisms
“Parasites” a very diverse set of eukaryotic pathogens zParasitology as a scientific discipline historically covers a diverse collection of multi- and unicellular eukaryotic organisms zProtozoa: unicellular eukaryotes (this is a historic term, protozoans are not really a monophyletic group) zPlatyhelminthes: flatworms these include flukes and tape worms zNematodes: elongated worms with rigid cuticula zArthropodes: insects, ticks and mites which either are parasitic or transmit parasites as vectors z(we only have time to discuss the most important groups causing human disease, there are many additional parasites outside these groups)
Note that the phylogeny in this tree has flaws and is just used to show diversity
Ecto- & Endoparasitism zEctoparasites live on, but not in their hosts (they can nevertheless cause severe illness). Ich a protozoan ectoparasite of the skin of a fish. zEndoparasite live within the body and tissues of their hosts. Trypanosomes (which cause sleeping sickness) within the blood of an infected animal.
Infection & infestation zInfectious diseases are caused by transmittable parasitic agents including bacteria, viruses, fungi, protozoa and a variety of metazoans commonly referred to as helminths or worms zInfection usually implies replication of the agent resulting in a growing number of pathogens zInfestation are characterized by a constant number of pathogens. Severity of disease often depends on infection dose.
Obligate/facultative, and permanent/intermittent parasites zMost parasites are obligate parasites zIn some species only some life cycle stages, e.g. the larvae are parasitic, in others parasitic and free living generations can alternate depending on environmental conditions (Strongiloides stercoralis). IndirectDirect
Hosts and life cycles zThe definitive host is by definition the one in which the parasite reproduces sexually zAdditional hosts are then designated intermediate hosts zHost which actively transmit parasites to humans are often called vectors zIn paratenic or transport hosts no parasite development occurs zReservoir host are alternate animal host from which the parasite can be transmitted to humans (zoonosis) or domestic animals zAccidental host, not suitable for parasite development, but severe disease might ensue nonetheless
Disease terminology zPrepatency: infected but parasite presence can not be detected yet zPatency: established infection, parasite stages can be detected (malaria parasites in blood smears, worm eggs in feces etc.) zIncubation period: time between infection and the development of symptoms zAcute disease can lead to crisis which can resolve in spontaneous healing, chronic infection or death zConvalescence: Period after healing, absence of infectious agents, no symptoms, in certain case immunity to reinfection
Number of people infected/affected by parasitic diseases Diseases causing high mortality: Malaria (400M) Sleeping Sickness (0.5 M) Chagas (18M) Visceral Leishmaniasis (4M) Diseases causing morbidity & QL losses: Geohelminths (2B) Water & Foodborne Protozoans (1.5B) Schistosomiasis (200M) Lymphatic filariasis (120 M) Cysticercosis (?50M) Onchocerciasis (18M) Cutaneous Leishmaniasis (8M) Guinea worm (4M, now 60K)