1. The significance of Medical Parasitology

2. The significance of Medical Parasitology
Prevalent infections worldwide
Significant morbidity & mortality
Significant impact on economic & social development
Increased mobility of individuals & populations
Drug resistance, climate change & opportunistic infections

3. Global estimates of parasitic diseases and disease burden (Topley & Wilson, 2005)

4. Definitions of parasitism
Concept of metabolic dependence (Smyth) (nutrition, developmental stimuli, control of maturation)
Genetic complementation
Population dynamic approach (Crofton)- lethal level, overdispersion, reproductive rate

5. Parasitic adaptations
Morphological adaptations
Biochemical changes
Specialized mechanisms for entry
Complex life cycles and transmission opportunities
Mechanisms for immune evasion
Impact on host versus impact of host

6. Parasitic adaptations

7. Important parasitic groups
Microparasites (Protozoa)
Kinetoplastida
Ciliophora
Apicomplexa
Macroparasites (Helminths, Arthropods)
Platyhelminthes
Nematoda
Arthropoda

8. Important issues associated with parasites of human importance
Life cycle and transmission
Pathology and symptomatology
Epidemiology, human behaviour and at risk groups
Medical history
Diagnostic difficulties
Prevention and control

9. Approach to the patient
Full history required particularly travel history
Symptoms may be subtle and may change over time (repeated history taking)
General history also important - occupation, hobby and leisure activities, diet, drugs taken.
Clinical exam

10. Life cycle and routes of transmission
Diverse routes of transmission which relate to human behaviour and risk factors
e.g. Toxoplasma gondii
Diverse routes of transmission with implications for parasite survival and pathogenicity
e.g. Strongloides stercoralis

11. Toxoplasma Life cycle

12. Strongyloides life cycle

13. Symptomatology and pathology 1
Parasites often provoke nonspecific and diverse symptoms
e.g. Toxocariasis in children
Microparasites often provoke more acute disease compared to the chronicity of macroparasites
e.g. Plasmodium falciparum versus Strongyloides stercoralis in returned travellers

14. Symptomatology and pathology 2
Differential pathology
Immunocompromised
versus
Immunocompetent hosts
e.g. Toxoplasma gondii & Cryptosporidium parvum

15. Epidemiology Changes in human behaviour At risk groups
Migration and International travel
Exotic foods
Pet ownership (including exotic pets)
Intensification of agricultural practices
At risk groups
Age, Occupation, Immune status, Pregnancy, Organ transplantation

16. Diagnostic dilemmas
Different diagnostic tests for different patient groups
Toxoplasma gondii
Need for repeat diagnostic testing
Giardia intestinalis
Need for improved sensitivity of diagnostic methods
Strongyloides stercoralis & Taenia solium

17. Prevention and control

18. Dracunculus medinensis : guinea worm

19. Prevalence of important Microparasites
Malaria : 500 million (annual deaths 2.2 to 2.5 million)
Giardiasis : 200 million
American Trypanosomiasis : million (annual deaths 60,000)
Leishmaniasis : million
Amoebiasis : 500 million

20. Prevalence of important Macroparasites
Cestodiasis : 70 million
Schistosomiasis : 200 million (annual deaths 500,000 to 1 million)
Lymphatic filariasis : million
Onchocerciasis : 17.5 million
Ascariasis : 1.3 billion
Hookworm : 1 billion
Strongyloidiasis : million

21. The Big Three and Neglected tropical diseases (NTDC)
Three vector-borne protozoa: Leishmaniasis, African Trypanosomiasis & Chagas disease
Three bacterial infections: trachoma, leprosy and Buruli ulcer
Seven helminth infections: hookworm, ascariasis, trichuriasis, lymphatic filariasis, onchocerciasis, guinea worm & schistosomiasis
Cysticercosis, food-borne trematodiasis & some other parasitic infections could be included
From Hotez et al, 2006, PLoS Medicine

22. Implications of co-infections

23. Challenges Rare diseases
Echinococcus multilocularis : alveolar echinococcosis (AE)
Emerging diseases

24. Toxoplasmosis
Malaria
Schistosomiasis
Neurocysticercosis
Lymphatic filariasis

25. Texts
Topley and Wilson’s Microbiology and Microbial infections Parasitology (2005). Eds Cox, F.E.G., Wakelin, D., Gillespie, S.H and D.D. Despommier. 10th Edition. Hodder Arnold.
Peters, W. and Pasvol, G. (2007). Tropical Medicine and Parasitology. Mosby 6th edition.