Intro
• Medical parasitology: the study and medical implications of parasites that infect humans.
• Molecular parasitology: the study of the molecular biology of parasites.
• A parasite: a living organism that acquires some of its basic nutritional requirements through its
intimate contact with another living organism. Parasites may be simple unicellular protozoa or
complex multicellular metazoa.
• Eukaryote: a cell with a well-defined chromosome in a membrane-bound nucleus. All parasitic
organisms are eukaryotes.
• Protozoa: unicellular organisms, e.g. Plasmodium (malaria), trypanosomas, Leishmania.
• Metazoa: multicellular organisms, e.g. helminths (worms) and arthropods (ticks, lice).
• An endoparasite: a parasite that lives within another living organism – e.g. malaria, Leishmania,
Giardia, Trypanosoma, helminths
• An ectoparasite: a parasite that lives on the external surface of another living organism – e.g. lice,
ticks
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• Host: the organism in, or on, which the parasite lives and causes harm (or acts as a reservoir)
• Definitive host: the organism in which the adult or sexually mature stage of the parasite lives.
• Intermediate host: the organism in which the parasite lives during a period of its development only.
• Zoonosis: a parasitic disease in which an animal is normally the host - but which also infects man.
• Vector: a living carrier (e.g.an arthropod) that transports a pathogenic organism from an infected to a
non-infected host. A typical example is the female Anopheles mosquito that transmits malaria
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• Although parasitic infections occur globally, the majority occur in tropical regions, where there is
poverty, poor sanitation and personal hygiene
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Parasite
Plasmodium
Diseases
No. people infected
malaria
Soil transmitted helminths:
•
Roundworm (Ascaris)
•
•
•
Whipworm (Trichuris)
Hookworm
(Ancylostoma and
Necator)
Deaths/yr
273 million
1.12 million
2 billion
200,000
Pnemonitis, intestinal
obstruction
Bloody diarrhoea, rectal
prolapse
Coughing, wheezing, abdominal
pain and anaemia
Schistosoma
Renal tract and intestinal
disease
200 million
15,000
Filariae
Lymphatic filariasis and
elephantiasis
120 million
Not fatal but 40
million
disfigured or
incapacitated
Trypanasoma cruzi
Chagas disease
(cardiovascular)
13 million
44,000
African trypanosomes
African sleeping sickness
0.3 – 0.5 million
68,000
Leishamania
Cutaneous, mucocutaneous
and visceral leishmaniasis
12 million; 2 million
new cases/yr
100,000
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Why do we study parasites?
• Parasites provide unique examples of biological
phenomena not found in free-living organisms.
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Why do we study parasites?
• Parasites provide unique examples of biological
phenomena not found in free-living organisms.
• Medical Importance
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Why do we study parasites?
• Parasites provide unique examples of biological
phenomena not found in free-living organisms.
• Medical Importance
• Veterinary Importance
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Why do we study parasites?
• Parasites provide unique examples of biological
phenomena not found in free-living organisms.
• Medical Importance ********
• Veterinary Importance
• Economic Importance********
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Elephantiasis
Intro
• Lymphatic filariasis, commonly known as elephantiasis, is a neglected tropical disease.
Infection occurs when filarial parasites are transmitted to humans through mosquitoes. When
a mosquito with infective stage larvae bites a person, the parasites are deposited on the
person's skin from where they enter the body. The larvae then migrate to the lymphatic
vessels where they develop into adult worms in the human lymphatic system.
• Wuchereria bancrofti, which is responsible for 90% of the cases
• Brugia malayi, which causes most of the remainder of the cases
• Adult worms lodge in the lymphatic system and disrupt the immune system. They live for 6-8
years and, during their life time, produce millions of microfilariae (small larvae) that circulate
in the blood.
• Lymphatic filariasis is transmitted by different types of mosquitoes for example by
the Culex mosquito, widespread across urban and semi-urban areas; Anopheles mainly in
rural areas, and Aedes, mainly in endemic islands in the Pacific
http://www.youtube.com/watch?v=dnWwHthkGkY&feature=related
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• African trypanosomiasis, also known as "sleeping sickness," is caused by microscopic parasites
of the species Trypanosoma brucei. It is transmitted by the tsetse fly (Glossina species), which
is found only in rural Africa.
• http://www.youtube.com/watch?v=EnsydwITLYk
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• Chagas disease is named after the Brazilian physician Carlos Chagas, who discovered the
disease in 1909. It is caused by the parasite Trypanosoma cruzi, which is transmitted to
animals and people by insect vectors (triatomines) and is found only in the Americas (mainly,
in rural areas of Latin America where poverty is widespread). Chagas disease (T. cruzi infection)
is also referred to as American trypanosomiasis.
• http://www.youtube.com/watch?v=7q9PTljtRhE
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Importation of Parasites from Tropics to the
U.S.
• Movement of persons from all areas of the
world have introduced parasitic diseases into
the U.S.
– Numerous cases of malaria are brought back by vacationers
from the tropics.
– Service personnel are often employed in areas endemic with
many parasites.
– Many immigrants have brought their parasites with
them.
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