4-8 June 2012 T. van Gool, MD, PhD A. Bart, PhD Academic Medical Center Amsterdam F. Derouin, MD, PhD Hôpital Saint Louis Paris T. Kortbeek, MD RIVM, Bilthoven
How good is training in Clinical Parasitology? Fairly unknown.. some assumptions. Basic education in Clinical Parasitology in MD training schemes in European universities is limited (10-20 hours in whole 5 year course.) Limited specific training in Clinical Parasitology for specialists (in training) in medical microbiology or medical biology (several weeks to 2-3 months in 4 year programme) Few separate courses available in CP, in English, were both lectures and practicals are provided. One country with an official scheme to become medical parasitologist/mycologist: France
Malaria an ongoing challenge to mankind Tom van Gool Rogier van Doorn
Introduction Malaria is one of the major infectious diseases worldwide Caused by a protozoan parasites living in humans and moquitoes Estimated 300 million cases with clinical malaria each year Estimated 1-2 million deaths each year Most illness and death in young children in Africa
An old disease: history 2700 BC Symptoms of malaria in humans described in China (Nei Ching) 400 BC Major impact on health in city-states in Greece 350 Description of anti-fever action of Qinghao plant in China 1700 Missionaries learned about medicine from bark in Peru: Cinchona (quinine) 1880 Discovery of malaria parasites by Laveran (French army surgeon, Algeria) 1890 Discovery of transmission route by mosquitoes by Ross 1934 (1946) Discovery of chloroquine by Andersag: best malaria medicine ever 1939 Discovery of DDT, an excellent insecticide by Muller (1874 by Zeidler)
Malaria parasites are small unicellular parasites. There are 120 different species. Present in many different animals: in i.e. primates, rodents, birds and reptiles In humans only 5 species: P. falciparum P. vivax P. ovale P. malariae P. knowlesi
Areas were malaria currently is endemic CDC and WHO 3,2 billion persons do live in areas at risk of transmission in 107 countries 250 million clinical episodes of malaria each year, 600-800.000 deaths/year 60% of theses cases and 80% of deaths in Africa South of the Sahara
Distribution of malaria species P. ovale P. knowlesi CDC and WHO P. falciparum, P. vivax and P. malariae
Imported malaria: Europa, 2008 490 cases
600 500 400 300 200 100 Imported malaria Netherlands 1979-2008 0 2000 1979 2008
Stages needed for transmission by mosquitoes (gametocytes) Sporogony: 10-18 days Optimum: 25-30 (C) First attack: sporozoites Cause of disease In humans (trophozoites/ schizonts)
Factors that determine the occurrence of malaria 1) Anopheles mosquitoes must be present, which are in contact with humans and in which the parasites can complete the invertebrate host part of their life cycle. 2) Malaria parasites must be present 3) Humans must be present who are in contact with Anopheles mosquitoes
The vector of malaria Anopheles musquitoes: 430 species known, only 40-50 important vectors of malaria (females transmit malaria only)
Life cycle of mosquitoes Total aquatic cycle: 31 C: 7 D 20 C: 20D 2-3 km of breeding sites Survival mosquito 10-14d (TR) -1 month In general 10 days needed for sporogony of P. falciparum!! During lifetime on general 4-5 a bloodmeal is taken Eggs produced every 2-3 days:
Epidemiology: some important determinants Longevity of vector one of the most important factors Sporogony (development of the sporozoite parasites in the vector) takes over a week (depending on ambient temperatures): The mosquito must survive for longer than this after feeding on a gametocyte-carrying human, if malaria is to be transmitted! Survival Anopheles in tropics 10-14 days < 20 C no P. falciparum development < 15 C no P. vivax development No X sporogony
Importance of humidity for transmission With lower as 50% humidity longevity of Anopheles is strongly reduced Malaria is usually a rainy season disease, coinciding with increased mosquito abundance Rainfall creates water collections, needed for breeding Unusual heavy rainfall with high temperatures can cause explosion of numbers of Anopheles with disastrous malaria epidemics
Detailed knowledge of species, biology and behaviour factors of mosquitoes essential for understanding transmission and control strategies of malaria! Larva of Anopheles mosquito
Pupa of Anopheles mosquito
Larval collection
Larval collection
Mosquito collection epidemiol
Mosquito collection with suction tube and torch epidemiol
Mosquito identification epidemiol
Dissecting mosquitoes epidemiol
Detailed knowledge of species, biology and behaviour factors of mosquitoes essential for understanding transmission and control strategies of malaria! Larva of Anopheles mosquito
Pupa of Anopheles mosquito
Larval collection epidemiol
Larval collection epidemiol
Mosquito collection epidemiol
Mosquito collection with suction tube and torch epidemiol
Importance of human factors on risk of (severe) malaria 1) Acquired Immunity: severity 2) Genetic factors: sickle cell trait (heterozygotes for abnormal hemoglobin gene HbS), ovalocytosis, G6PD deficiency and thalassaemia protect to some extent against malaria. Absence of Duffy blood group antigen protects against P. vivax infection: no P. vivax in West-Africa!
Importance of human factors II Pregnancy in malaria: Poverty: Lack of knowledge: No financial resources: Human activities: Nighttime exposure: War, migrations,tourism: immunity less, anaemia of mother, children with low birth weight, premature delivery no good housing, no bed nets to recognize malaria, cultural beliefs long distance to medical support produce breeding sites due to agricultural work may expose non-immune populations to malaria
Human behavior: pioneer settlement in Venezuela with many new breeding places of malaria mosquitoes epidemiol
Population movements: forest clearance, Brazil epidemiol