CBio 4500/6500 Medical Parasitology Spring Semester 2012
Medical Parasitology • Lectures on Tuesdays & Thursdays in the second period 9:30-10:45 a.m. • Please initial the attendance sheet each class • You may not miss more than 3 classes without detriment to your grade • There will be 2 exams during the semester & a final covering the entire material (30%,30%, & 40%) • firstname.lastname@example.org, email@example.com
Medical Parasitology • The class web site can be viewed at http://www.striepen.uga.edu/medpara/schedule.html • There is a link to this site through the UGA ELC site • The site features the syllabus & schedule, lecture notes and links to further web resources • ‘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) • Roberts & Janovy, Foundations of Parasitology, McGraw-Hill, 7th Ed. 2004 • Markell, John, Krotoski, Medical Parasitology,Saunders, 8th Ed. 1999 • Chiodine, Moody, Manser, Atlas of Medical Helminthology and Protozoology,Churchhill Livingstone, 4th Ed. 2001 • Peters & Gilles, A Colour Atlas of Tropical Medicine & Parasitology, Wolfe, 3rd Ed. 1989 • Bogitsh, Carter, Oeltmann, Human Parasitology, Elsevier, 3rd Ed., 2005
Some book suggestions(for some of these titles newer editions might be available)
Summer job for highly skilled and very hard-working undergrad Google: Biology of Parasitism and MBL
websites • There are thousands of web sites providing information and images on parasites, not all of them are as trustworthy as one could wish • Two 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 • Medical Parasitology focuses on parasites which cause disease in humans. Parasites are also of great importance in veterinary medicine. • Several diseases falling it this field only occur in the tropics, but many parasite disease are/were very common in temperate climates • Overall there is a much stronger association with the level of housing, nutrition, sanitation and general public health than climate. Parasitic diseases are in their majority the diseases of the poor around the globe. Poverty is a major risk factor for disease – but disease is also a major contributor to poverty.
GNP per capita (1995) $0-70 $0-70 $1941-2580 $1941-2580 Malaria Index 0 0 3 3 Medical Parasitology
Outline of the class • Brief introduction into concepts and terminology of: parasitology, vector biology, immunology & public health (4 lectures) • Helminth diseases (flukes, tape worms & round worms) (9 lectures) • Diseases caused by unicellular eukaryotes often referred to as protozoa (e.g. sleeping sickness & malaria) (13 lectures) • Lectures will combine biology of the parasites and vectors, pathogenesis of the disease, treatment and prevention of diseases, and control efforts • Where possible we will try to include cutting edge science with a focus on new molecular concepts
Parasitism - a way of life • Parasite and Parasitism are ecological terms that define a way of life rather than a coherent and evolutionary related group of organisms • Symbiosis, Commensalism, Mutualism, Parasitism
Parasitism - a way of life • Parasite and Parasitism are terms that define a way of life rather than a coherent and evolutionary related group of organisms • Symbiosis: “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 • Commensalism: Sharing the table. One partner benefits but the other is not hurt. • Mutualism: Both partners benefit. • Parasitism: One partner (the parasit) harms or lives on the expense of the other (host).
Is the mighty lion a despicable parasite? • The benefit in the relationship between lion and wildebeest seems highly skewed in favor of the lion
Who is a parasite? • Parasites are usually much smaller than their hosts, they also do not kill before they eat.
Is a mosquito a parasite? • The border between parasitism and micro-predation is blurry • Parasites usually live in a very intimate relationship with their host depending on more than food from it • The host is food source and more or less permanent habitat at the same time • Many parasites show strict specificity for a single host
“Parasites” a very diverse set of eukaryotic pathogens • Parasitology as a scientific discipline historically covers a diverse collection of multi- and unicellular eukaryotic organisms • Protozoa: unicellular eukaryotes (this is a historic term, protozoans are not really a monophyletic group) • Platyhelminthes: flatworms these include flukes and tape worms • Nematodes: elongated worms with rigid cuticula • Arthropodes: insects, ticks and mites which either are parasitic or transmit parasites as vectors • (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 • Ectoparasites live on, but not in their hosts (they can nevertheless cause severe illness). Ich a protozoan ectoparasite of the skin of a fish. • Endoparasite live within the body and tissues of their hosts. Trypanosomes (which cause sleeping sickness) within the blood of an infected animal.
Infection & infestation • Infectious diseases are caused by transmittable parasitic agents including bacteria, viruses, fungi, protozoa and a variety of metazoans commonly referred to as helminths or worms • Infection usually implies replication of the agent resulting in a growing number of pathogens • Infestation are characterized by a constant number of pathogens. Severity of disease often depends on infection dose.
Obligate/facultative, and permanent/intermittent parasites • Most parasites are obligate parasites • In 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) . Indirect Direct
Hosts and life cycles • The definitive host is by definition the one in which the parasite reproduces sexually • Additional hosts are then designated intermediate hosts • Host which actively transmit parasites to humans are often called vectors • In paratenic or transport hosts no parasite development occurs • Reservoir host are alternate animal host from which the parasite can be transmitted to humans (zoonosis) or domestic animals • Accidental host, not suitable for parasite development, but severe disease might ensue nonetheless
Disease terminology • Patency, Incubation period, Acute & Chronic, Convalescence
Disease terminology • Prepatency: infected but parasite presence can not be detected yet • Patency: established infection, parasite stages can be detected (malaria parasites in blood smears, worm eggs in feces etc.) • Incubation period: time between infection and the development of symptoms • Acute disease can lead to crisis which can resolve in spontaneous healing, chronic infection or death • Convalescence: Period after healing, absence of infectious agents, no symptoms, in certain case immunity to reinfection
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) Number of people infected/affected by parasitic diseases