Docstoc

An introduction to Medical Parasitology

Document Sample
An introduction to Medical Parasitology Powered By Docstoc
					                                               An introduction to Medical
Partners in Global Health Education
                                                      Parasitology
1.    How to use this
      module
2.    Learning
      outcomes
3.    Key definitions
4.    Epidemiology
5.    Burden of
      parasitic
      infections
6.    Classification of
      protozoa
7.    Classification of
      helminths
8.    Schistosomiasis
9.    Hookworm
10. Lymphatic
    filariasis
11. Sources of
    information




                                      For more information about the authors and reviewers of this module, click here
                                      How should you study this module?
Partners in Global Health Education



1.    How to use this
      module
                                • We suggest that start with the learning
2.    Learning                    objectives and try to keep these in mind as
      outcomes
3.    Key definitions
                                  you go through the module slide by slide, in
4.    Epidemiology                order.
5.    Burden of
      parasitic
      infections
                                • You should research any issues that you
6.    Classification of
      protozoa
                                  are unsure about. Look in your textbooks,
7.    Classification of
                                  access the on-line resources indicated at
8.
      helminths
      Schistosomiasis
                                  the end of the module and discuss with your
9.    Hookworm                    peers and teachers.
10. Lymphatic
    filariasis                  • Finally, enjoy your learning! We hope that
11. Sources of
    information                   this module will be enjoyable to study and
                                  complement your learning about TB from
                                  other sources.
                                              Learning Outcomes
Partners in Global Health Education



1.    How to use this           After completing this SDL, you should be able to:
      module
                                • Discuss how important parasites can be classified according
2.    Learning
      outcomes                     to kingdom and phylum
3.    Key definitions           • State the meaning of commonly-used terms
4.    Epidemiology              • Describe how parasitic infections affect communities in poor
5.    Burden of                    countries and that knowledge of their life cycle is necessary
      parasitic
      infections                   for effective prevention and control
6.    Classification of         • Discuss the epidemiology, basic life cycle, clinical
      protozoa
                                   presentation, management and control of some important
7.    Classification of            parasitic infections
      helminths
8.    Schistosomiasis
9.    Hookworm                  Note: This SDL will contain many unfamiliar terms. You are NOT
10. Lymphatic                      expected to remember the classifications and names of all of
    filariasis
                                   the different parasite species. The emphasis is on
11. Sources of                     understanding basic concepts and being able to illustrate
    information
                                   these with some important examples.
                                After completing this SDL, try the associated quiz to assess your
                                   learning.
                                         Key definitions: What is ….?
Partners in Global Health Education



1.    How to use this           •     Medical parasitology: “the study and medical implications of
      module
                                      parasites that infect humans”
2.    Learning
      outcomes
3.    Key definitions           •     A parasite: “a living organism that acquires some of its basic
4.    Epidemiology
                                      nutritional requirements through its intimate contact with another
5.    Burden of
                                      living organism”. Parasites may be simple unicellular protozoa or
      parasitic                       complex multicellular metazoa
      infections                •     Eukaryote: a cell with a well-defined chromosome in a membrane-
6.    Classification of               bound nucleus. All parasitic organisms are eukaryotes
      protozoa
7.    Classification of
      helminths                 •     Protozoa: unicellular organisms, e.g. Plasmodium (malaria)
8.    Schistosomiasis
9.    Hookworm                  •     Metazoa: multicellular organisms, e.g. helminths (worms) and
10. Lymphatic                         arthropods (ticks, lice)
    filariasis
11. Sources of
    information                 •     An endoparasite: “a parasite that lives within another living
                                      organism” – e.g. malaria, Giardia

                                •     An ectoparasite: “a parasite that lives on the external surface of
                                      another living organism” – e.g. lice, ticks
                                         Key definitions: What is ….?
Partners in Global Health Education



1.    How to use this           •     Host: “the organism in, or on, which the parasite lives and causes
      module
                                      harm”
2.    Learning
      outcomes
3.    Key definitions           •     Definitive host: “the organism in which the adult or sexually mature
4.    Epidemiology
                                      stage of the parasite lives”
5.    Burden of
      parasitic
      infections
                                •     Intermediate host: “the organism in which the parasite lives during
                                      a period of its development only”
6.    Classification of
      protozoa
7.    Classification of         •     Zoonosis: “a parasitic disease in which an animal is normally the
      helminths                       host - but which also infects man”
8.    Schistosomiasis
9.    Hookworm
                                •     Vector: “a living carrier (e.g.an arthropod) that transports a
10. Lymphatic                         pathogenic organism from an infected to a non-infected host”. A
    filariasis
                                      typical example is the female Anopheles mosquito that transmits
11. Sources of
    information
                                      malaria
                                                           Epidemiology
Partners in Global Health Education



1.    How to use this          •      Although parasitic infections occur
      module
                                      globally, the majority occur in tropical
2.    Learning                        regions, where there is poverty, poor
      outcomes
                                      sanitation and personal hygiene
3.    Key definitions
                               •      Often entire communities may be infected
4.    Epidemiology
                                      with multiple, different organisms which
5.    Burden of                       remain untreated because treatment is
      parasitic
      infections                      neither accessible nor affordable
6.    Classification of        •      Effective prevention and control requires
      protozoa                        "mass intervention strategies” and intense
7.    Classification of               community education. Examples include:
      helminths
                                       – General improved sanitation: pit
8.    Schistosomiasis                     latrines, fresh water wells, piped water
9.    Hookworm
                                       – Vector control: insecticide
10. Lymphatic                             impregnated bed nets, spraying of
    filariasis
                                          houses with residual insecticides,
11. Sources of
    information
                                          drainage, landfill
                                       – Mass screening and drug
                                          administration programmes which
                                          may need to be repeated at regular
                                          intervals
                                      The burden of some major parasitic
Partners in Global Health Education
                                                  infections
1.    How to use this                      Parasite                      Diseases              No. people infected        Deaths/yr
      module                    Plasmodium                    malaria                         273 million             1.12 million
2.    Learning
      outcomes                  Soil transmitted helminths:                                   2 billion               200,000
3.    Key definitions
                                •     Roundworm (Ascaris)     Pnemonitis, intestinal
4.    Epidemiology                                            obstruction
5.    Burden of                 •     Whipworm (Trichuris)
      parasitic                 •                             Bloody diarrhoea, rectal
      infections                •     Hookworm                prolapse
6.    Classification of               (Ancylostoma and
      protozoa                        Necator)                Coughing, wheezing, abdominal
                                                              pain and anaemia
7.    Classification of
      helminths                 Schistosoma                   Renal tract and intestinal      200 million             15,000
8.    Schistosomiasis                                         disease

9.    Hookworm
                                Filariae                      Lymphatic filariasis and        120 million             Not fatal but 40
10. Lymphatic
                                                              elephantiasis                                                million
    filariasis
                                                                                                                           disfigured or
11. Sources of                                                                                                             incapacitated
    information
                                Trypanasoma cruzi             Chagas disease                  13 million              14,000
                                                              (cardiovascular)
                                African trypanosomes          African sleeping sickness       0.3 – 0.5 million       48,000
                                Leishamania                   Cutaneous, mucocutaneous        12 million; 2 million   50,000
                                                              and visceral leishmaniasis          new cases/yr
                                      Taxonomic classification of parasitic organisms
Partners in Global Health Education



1.    How to use this           •     The classification of parasites is controversial - there is no
      module                          universally accepted system
2.    Learning                  •     Parasites form part of the animal kingdom which comprises some
      outcomes
                                      800,000 identified species categorised into 33 phyla (but it is
3.    Key definitions                 estimated that there may be ~10m species in total)
4.    Epidemiology
                                •     The parasitic organisms that are of importance for human health
5.    Burden of                       are eukaryotes - they have a well defined chromosome in a nuclear
      parasitic
      infections
                                      membrane (as opposed to prokaryotes which have no nuclear
6.    Classification of
                                      membrane, e.g. bacteria)
      protozoa                  •     Parasites are classified into 2 sub-kingdoms: protozoa (unicellular)
7.    Classification of               and metazoa (multicellular)
      helminths
                                •     Protozoan (unicellular) parasites are classified according to
8.    Schistosomiasis                 morphology and means of locomotion. There are 45,000 protozoa
9.    Hookworm                        species. Most species that cause human disease belong to the
10. Lymphatic                         phylums sarcomastigophora and apicomplexa
    filariasis
                                •     Metazoa (multicellular) include the worms (helminths) and
11. Sources of                        arthropoda (posses an external skeleton) e.g. ticks, lice
    information
                                •     Note that the genus starts with a capital letter and the species is
                                      always written in italics, e.g. Plasmodium falciparum, Giardia
                                      lamblia
                                                Taxonomic classification of protozoa
Partners in Global Health Education



1.    How to use this
      module                        Sub          Phylum              Sub-phylum          Genus-        Species-
2.    Learning                    kingdom                                               examples       examples
      outcomes
3.    Key definitions
                                Protozoa    Sarcomastig-           Sarcodina-- -      Entamoeba     E. histolytica
4.    Epidemiology                          ophora                 move by
                                                                   pseudopodia
5.    Burden of                             further divided into
      parasitic
      infections
6.    Classification of
                                                                   Mastigophora       Giardia       G. lamblia
      protozoa                                                     move by flagella

7.    Classification of
      helminths
                                            Apicomplexa                               Plasmodium    P. falciparum,
8.    Schistosomiasis                       no organelle of                                         P. vivax,
9.    Hookworm                              locomotion
                                                                                                    P. malariae,
10. Lymphatic
    filariasis                                                                                      P. ovale
11. Sources of
    information                             Ciliophora                                Balantidium   B. coli
                                            move by cillia



                                            Microspora                                Enterocyto-   E. bienusi
                                            Spore-forming                             zoa
                                      Examples of important intestinal protozoa
Partners in Global Health Education



1.    How to use this           Transmitted by the faecal-oral route
      module                       and cause diarrhoea
2.    Learning                  • Giardia lamblia: world-wide
      outcomes                     distribution, lives in the small intestine
3.    Key definitions              and results in malabsorption
4.    Epidemiology              • Entamoeba histolytica: may invade
5.    Burden of                    the colon and cause bloody diarrhoea
      parasitic                    – amoebic dysentery. Also causes
      infections                   ameobic liver abscess.
6.    Classification of         • Cryptosporidium parvum: more
      protozoa                     prevalent in the immunocompromised            Electron micrograph of G. lamblia
7.    Classification of         • Cyclospora cyatenensis - parasitises           trophozoites (feeding stage)
      helminths                    the small intestinal mucosa and may
8.    Schistosomiasis              cause diarrhoea for several weeks
9.    Hookworm                  • Balantidium coli: a large motile
10. Lymphatic
                                   ciliated parasite that lives in the colon
    filariasis                     of pigs, humans and rodents and can
                                   lead to colonic ulceration
11. Sources of
    information                 • Enterocytozoon bienusi: a
                                   microsporidian that parasitises the
                                   small intestine. Also more common in
                                   the immunocompromised.
                                                                                Typical flask-shaped ulcer due to E.
                                                                                histolytica in the colonic mucosa
                                            Examples of important systemic
Partners in Global Health Education
                                                      protozoa
1.    How to use this                                                    Detected in the blood
      module
2.    Learning                                                           •   Plasmodium: the cause of malaria. There
      outcomes                                                               are 4 species that infect man: P.
3.    Key definitions                                                        falciparum, P. vivax, P. ovale and P.
4.    Epidemiology
                                                                             malariae
5.    Burden of
      parasitic                                                          •   Toxoplasma gondi: transmitted by the
      infections                                                             ingestion of oocysts from cat faeces.
6.    Classification of                                                      Infection can lead to ocular problems and
      protozoa                                                               is also a cause of neonatal
7.    Classification of                                                      toxoplasmosis
                                      Typical lesion of
      helminths
                                      cutaneous leishmaniasis
8.    Schistosomiasis                                                    •   Leishmania: transmitted by sand flies,
9.    Hookworm                                                               can lead to visceral, cutaneous and
                                                                             mucocutaneous leishmaniasis
10. Lymphatic
    filariasis                                         Tsetse fly – the
11. Sources of                                         vector of African •   Trypanosoma: haemoflagellates which
    information                                        trypanosomiasis       cause
                                                       It has a painful       –   In Africa - sleeping sickness (transmitted
                                                       bite!                      by the Tsetse fly)
                                                                              –   In South America - Chagas disease
                                                                                  (transmitted by the Reduviid bug)
                                      Taxonomic classification of helminths
Partners in Global Health Education



1.    How to use this              Sub             Phylum                          Class                        Genus –
      module                     kingdom                                                                       examples
2.    Learning                  Metazoa    Nematodes                                                      Ascaris (roundworm)
      outcomes                             Round worms; appear round                                      Trichuris (whipworm)
                                           in cross section, they have                                    Ancylostoma (hookworm)
3.    Key definitions
                                           body cavities, a straight                                      Necator (hookworm)
4.    Epidemiology                         alimentary canal and an                                        Enterobius (pinworm or
                                           anus                                                           threadworm)
5.    Burden of
      parasitic                                                                                           Strongyloides
      infections
6.    Classification of                    Platyhelminthes               Cestodes                         Taenia (tapeworm)
      protozoa                             Flat worms; dorsoventrally    Adult tapeworms are found in
7.    Classification of                    flattened, no body cavity     the intestine of their host
                                           and, if present, the
      helminths                                                          They have a head (scolex) with
                                           alimentary canal is blind     sucking organs, a segmented
8.    Schistosomiasis                      ending                        body but no alimentary canal
9.    Hookworm                                                           Each body segment is
                                                                         hermaphrodite
10. Lymphatic
    filariasis
                                                                         Trematodes                       Fasciolopsis (liver fluke)
11. Sources of
                                                                                                          Schistosoma (not leaf
    information                                                          Non-segmented, usually leaf-
                                                                         shaped, with two suckers but     shaped!)
                                                                         no distinct head
                                                                         They have an alimentary canal
                                                                         and are usually hermaphrodite
                                                                         and leaf shaped
                                                                         Schistosomes are the
                                                                         exception. They are thread-
                                                                         like, and have separate sexes
                                         Examples of important metazoa –
Partners in Global Health Education
                                             intestinal nematodes
                               •      Trichuris (whipworm)
1.    How to use this                                                         •   Ascaris (roundworm)
      module                           – A soil transmitted helminth               – Found world-wide in conditions of
2.    Learning                         – prevalent in warm, humid                     poor hygiene, transmitted by the
      outcomes                             conditions                                 faecal- oral route
3.    Key definitions                  – Can cause diarrhoea, rectal               – Adult worms lives in the small
                                           prolapse and anaemia in heavily-           intestine
4.    Epidemiology                                                                 – Causes eosinophilia
                                           infected people
5.    Burden of
      parasitic
      infections               •      Ancylostoma and Necator
6.    Classification of               (hookworms)
      protozoa                         – A major cause of anaemia in the
7.    Classification of                   tropics
      helminths
8.    Schistosomiasis          •      Strongyloides
9.    Hookworm                         – inhabits the small bowel
10. Lymphatic                          – infection more severe in
    filariasis                            immunospressed people (e.g.
11. Sources of                            HIV/AIDS, malnutrition,
    information                           intercurrent disease)
                                                                                  Heavy intestinal infections may
                               •      Enterobius (pinworm or threadworm)          occur with Ascaris. Adult worms
                                                                                  can be several cms long.
                                       – prevalent in cold and temperate
                                          climates but rare in the tropics
                                       – found mainly in children
                                       Examples of important metazoa –
Partners in Global Health Education
                                            systemic nematodes
1.    How to use this
      module                      Filaria including:                  •   Toxocara
2.    Learning
      outcomes                    •   Onchocerca volvulus –               –   A world-wide infection of
3.    Key definitions                 Transmitted by the simulium             dogs and cats
4.    Epidemiology
                                      black fly, this microfilarial       –   Human infection occurs
5.    Burden of
      parasitic                       parasite can cause visual               when embryonated eggs
      infections
6.    Classification of               impairment, blindness and               are ingested from dog or
      protozoa
                                      severe itching of the skin in           cat faeces
7.    Classification of
      helminths                       those infected                      –   It is common in children
8.    Schistosomiasis
9.    Hookworm
                                  •   Wuchereria bancrofti – The              and can cause visceral
10. Lymphatic                         major causative agent of                larva migrans (VLM)
    filariasis
11. Sources of
                                      lymphatic filariasis
    information
                                  •   Brugia malayi – Another
                                      microfilarial parasite that
                                      causes lymphatic filariasis
                                      Examples of important flatworms -
Partners in Global Health Education
                                                  cestodes
1.    How to use this           1. Intestinal - (“tapeworms”)           2. Systemic
      module
                                •     Taenia saginata
2.    Learning                                                          •   Echinococcus granulosus (dog
      outcomes                         – worldwide
                                                                            tapeworm) and Echinicoccus
3.    Key definitions                  – acquired by ingestion of
                                         contaminated, uncooked             multilocularis (rodent
4.    Epidemiology
                                         beef                               tapeworm)
5.    Burden of
      parasitic                        – a common infection but
      infections                         causes minimal symptoms
6.    Classification of
                                                                             –   Hydatid disease occurs
      protozoa
                                •     Taenia solium
                                                                                 when the larval stages of
7.    Classification of                – worldwide
      helminths
                                                                                 these organisms are
                                       – acquired by ingestion of
8.    Schistosomiasis                    contaminated, uncooked                  ingested
9.    Hookworm                           pork that contains
10. Lymphatic                            cystercerci
    filariasis
                                                                             –   The larvae may develop in
                                       – Less common, but causes
11. Sources of                           cystercicosis – a systemic              the human host and cause
    information
                                         disease where cysticerci                space-occupying lesions in
                                         encyst in muscles and in the            several organs, e.g. liver,
                                         brain – may lead to                     brain
                                         epilepsy
                                       Examples of important metazoa –
Partners in Global Health Education
                                            trematodes (flukes)
1.    How to use this           Intestinal                            •   Fasciola hepatica (liver fluke)-
      module                    Fasciolopsis buski - A common             Primarily, a parasite of sheep,
2.    Learning
                                                                          humans become infected when they
                                   parasite of humans and pigs            ingest metacercariae that have
      outcomes
                                   in South- east Asia. This              encysted on watercress. The adult
3.    Key definitions              parasite is one of the largest         trematode lives in the intra-hepatic
4.    Epidemiology                 trematodes to infect man               bile ducts of the liver. “Fascioliasis”
5.    Burden of                    (8cm in length) and lives in           can lead to severe anaemia in
      parasitic                    the upper intestine. Chronic           humans
      infections
                                   infection leads to
6.    Classification of            inflammation, ulceration and       •   Clonorchis sinensis (liver fluke)-
      protozoa
                                   haemorrhage of the small               Widespread in China, Japan, Korea
7.    Classification of                                                   and Taiwan, this parasite is acquired
      helminths
                                   intestine
                                                                          by ingestion of infective
8.    Schistosomiasis                                                     metacercariae in raw or pickled fish
9.    Hookworm
10. Lymphatic                                                         •   Paragonimus westermani ( lung
    filariasis                                                            fluke)- Widespread in the Far East
11. Sources of                                                            and South east Asia, the parasite is
    information                                                           acquired by ingestion of infective
                                                                          metacercariae in raw or pickled
                                                                          crustaceans
                                 Adult Fasciolopsis buski trematode
                                © Dr. Peter Darben, Queensland        •   Schistosoma haematobium, S.
                                University of Technology                  mansoni and S. japonicum – see
                                                                          below
                                      Schistosomiasis (bilharzia)
Partners in Global Health Education



1.    How to use this
      module
2.    Learning
      outcomes
3.    Key definitions
4.    Epidemiology
5.    Burden of
      parasitic
      infections
6.    Classification of
      protozoa
7.    Classification of
      helminths
8.    Schistosomiasis
9.    Hookworm
10. Lymphatic
    filariasis
11. Sources of
    information
                                                          Schistosomiasis (1)
Partners in Global Health Education



1.    How to use this           Epidemiology
      module                    • 200m people in 74 countries
2.    Learning                     infected, 85% of whom live in
      outcomes                     sub-Saharan Africa
3.    Key definitions           • S. haematobium - Africa and
4.    Epidemiology
                                   middle east (most prevalent)
5.    Burden of
                                • S. Mansoni - Africa and Latin
      parasitic                    America
      infections                • S. japonicum – Pacific region
6.    Classification of
      protozoa
                                Life cycle                                          Bulinus globosus, the intermediate host snail for S.
7.    Classification of         •     Transmission occurs in fresh water            haematobium (source: WHO/TDR/Stammers)
      helminths
                                •     Infective cercariae released from snails of
8.    Schistosomiasis                 the genera Bulinus, Biomphalaria
9.    Hookworm
                                      Oncomelania
                                •     Cercariae penetrate the skin of people who
10. Lymphatic                         drink, swim or bathe in infected water
    filariasis
                                •     Adult worm live in the veins that drain the
11. Sources of                        urinary system (S. haematobium) or
    information                       mesentric blood vessels intestines (S.
                                      mansoni, S. japonicum) and release eggs
                                      into water in urine or faeces                  S. haematobium cercaria (differential
                                •     Eggs develop into miracidia which then         interference contrast microscopy; source:
                                      infect snails                                  WHO/TDR/Stammers)
                                                              Schistosomiasis (2)
Partners in Global Health Education



1.    How to use this
      module                          Pathology
2.    Learning                        •   Shistosoma eggs become trapped in the tissues of the urinary tract (S. haematobium)
      outcomes                            and intestines (S. mansoni, S. japonicum)
3.    Key definitions                 •   This results in inflammatory response and tissue damage
4.    Epidemiology
5.    Burden of
      parasitic
      infections
6.    Classification of
      protozoa
7.    Classification of
      helminths
8.    Schistosomiasis
9.    Hookworm
10. Lymphatic
    filariasis
11. Sources of
    information

                                                                                    S. haematobium eggs measure 140 x 50 μm
                                          Adult worms of S. haematobium are 1-2     (differential interference contrast microscopy;
                                          cm long (source: WHO/TDR/Stammers)        source: WHO/TDR/Stammers)
                                                           Schistosomiasis (3)
Partners in Global Health Education



1.    How to use this           Symptoms and signs                                  Treatment
      module                    •     Urinary Schistosomiasis:                      •    Praziquantel: effective against all
2.    Learning                         – S. hamatobium                                   species
      outcomes
                                       – Gross haematuria                           •    S. haematobium: single dose (40
3.    Key definitions                  – Dysuria                                         mg/kg)
4.    Epidemiology                     – Bladder, ureters and kidneys damaged
                                                                                    •    S. mansoni, S. japonicum: 2-3 doses of
5.    Burden of                             Cancer of the bladder is common
                                                                                         30mg/kg
      parasitic
      infections                •     Intestinal schistosomiasis
6.    Classification of                 – S. mansoni, S. japonicum
      protozoa                          – Gradual enlargement of liver and spleen
7.    Classification of                      intestines
      helminths                         – hypertension of the abdominal blood
8.    Schistosomiasis                        vessels which begin to bleed
9.    Hookworm                          – Blood in the stools
                                •     Diagnosis
10. Lymphatic
    filariasis                  •     Microscopy for eggs:
11. Sources of                          – urine sediment for S. haematobium
    information                         – concentrated stool samples for S.
                                             mansoni, S. japonicum
                                •     Serology – all species
                                •     Rectal biopsy - S. mansoni, S. japonicum          Haematuria due to S. haematobium
                                                                                        (source: WHO/TDR)
                                                            Schistosomiasis (4)
Partners in Global Health Education



1.    How to use this
      module
                                      Prevention and control
2.    Learning
      outcomes                        •   Educate people to not urinate or defecate in
3.    Key definitions
                                          fresh water supplies
4.    Epidemiology
                                      •   Eliminate snail vectors by making the water
                                          habitat unsuitable (increase water flow,
5.    Burden of
      parasitic
                                          remove vegetation)
      infections                      •   Provide piped water to avoid direct contact
6.    Classification of                   with cercariae
      protozoa                        •   Mass drug treatment of communities to
7.    Classification of                   reduce reservoir of infection
      helminths
8.    Schistosomiasis
9.    Hookworm
10. Lymphatic
    filariasis
11. Sources of
    information
                                          Concrete irrigation ditches do not allow
                                          breeding of Oncomelania snails (source:
                                          WHO/TDR/Crump)
                                                              Hookworm (1)
Partners in Global Health Education



1.    How to use this
      module                    Epidemiology
2.    Learning
      outcomes                  •     >1200m infections each year of which
3.    Key definitions                 100m are symptomatic
4.    Epidemiology
                                •     It is due to 2 parasites both of which
5.    Burden of
      parasitic                       occur worldwide:
      infections
                                       – Necator americanus - predominant
6.    Classification of
      protozoa                           species in sub-Saharan Africa,
7.    Classification of                  south Asia and the Pacific
      helminths
8.    Schistosomiasis                  – Ancylostoma duodenale –
9.    Hookworm                           predominant in S. Europe, N.
10. Lymphatic                            Africa, western Asia, northern
    filariasis
11. Sources of                           China, Japan and the west coast of
    information                          America

                                                                               Hookworm is a major cause
                                                                               of anaemia
                                                                     Hookworm (2)
Partners in Global Health Education



1.    How to use this           Life cycle
      module                    •      Adult worms live in the intestine and excrete eggs in the faeces
2.    Learning
                                •      In the absence of latrines, eggs contaminate soil and develop in warm, damp conditions
      outcomes                  •      eggs hatch and infective filariform larvae develop in about one week and remain infective in
                                       soil for many weeks
3.    Key definitions           •      filariform larvae penetrate the skin when a person walks barefoot in the soil
4.    Epidemiology              •      larva migrate from the skin to the lungs via the lymphatic and blood systems
5.    Burden of                 •      larvae penetrate the capillary wall to enter the alveolus
      parasitic                 •      Larvae are propelled up the respiratory tree to the epiglottis where they are swallowed
      infections                •      Develops to adult stage in upper intestine; adult worms are fully mature after about 5 weeks
6.    Classification of         •      Eggs are excreted in the faeces
      protozoa
7.    Classification of         •      Note: eating soil (pica) is a common practice. Ingested filariform larvae of A. duodenale can
      helminths                        pass directly to the gut mucosa
8.    Schistosomiasis
9.    Hookworm
10. Lymphatic
    filariasis
11. Sources of
    information



                                    Egg of A. duodenale in faecal smear
                                    (size 57-76 µm by 35-47 µm)                                Filariform larvae
                                    © Dr. Peter Darben, Queensland                             © Dr. Peter Darben, Queensland
                                    University of Technology                                   University of Technology
                                                                    Hookworm (3)
Partners in Global Health Education



1.    How to use this
      module                          Pathology
2.    Learning                        •   Hookworms move several times a day to
      outcomes
                                          different attachment sites in the upper
3.    Key definitions                     intestinal mucosa to ingest blood
4.    Epidemiology                    •   They secrete an anticoagulant which
5.    Burden of                           causes the old attachment sites to
      parasitic                           continue to bleed
      infections
                                      •   Heavy hookworm infection results in
6.    Classification of
      protozoa                            chronic haemorrhage from the duodenal
7.    Classification of
                                          and jejunal mucosa
      helminths                       •   The combination of constant blood loss
8.    Schistosomiasis                     due to hookworm infection and poor iron
9.    Hookworm
                                          intake in the diet results in iron deficiency
                                          anaemia
10. Lymphatic
    filariasis                        •   A. duodenale ingests 4-5 times more
11. Sources of                            blood each day than N. americanus
    information                       •    In a child, the continued daily loss of 10ml
                                          of blood can lead to severe anaemia
                                                                                          Adult male and female worms of A. duodenale
                                                                                          © Dr. Peter Darben, Queensland University of
                                                                                          Technology
                                                               Hookworm (4)
Partners in Global Health Education



1.    How to use this           Symptoms and signs                              Treatment
      module
                                Minor                                           •       Mebendazole (cheap) – 100mg, twice
2.    Learning
      outcomes                  •   Often itchy papules are found at the site           daily for 3 days
3.    Key definitions               where the larva penetrated the skin         •       Mebendazole is contraindicated in
4.    Epidemiology              •   There may be cough and wheezing as                  pregnancy – use Bephenium
                                    the larva migrates through the lungs                hydroxynaphthoate “alcopar”
5.    Burden of
      parasitic                 Major                                           •       For anaemia: ferrous sulphate 200-400
      infections                                                                        mg three times a day for 3 months
                                •   Hookworm anaemia
6.    Classification of                                                                 (adult regimen)
      protozoa                        – Tiredness, aches and pains
7.    Classification of               – Pallor
      helminths                       – Breathlessness
8.    Schistosomiasis                 – Oedema                                      Prevention and control
9.    Hookworm                  Diagnosis                                           •   Health education and improve sanitation
10. Lymphatic                                                                           facilities – install pit latrines
                                •   Microscopic examination of faecal
    filariasis
                                    smears to demonstrate significant               •   Encourage use of protective footwear
11. Sources of                      numbers of hook worm eggs                       •   Discourage soil eating (pica)
    information
                                •   Measure Hb, serum ferritin, iron                •   Mass drug treatment of communities
                                •   Exclude other causes of anaemia                 •   Iron supplementation in areas of low iron
                                                                                        intake
                                             Lymphatic filariasis (1)
Partners in Global Health Education



1.    How to use this
      module
                                Epidemiology
2.    Learning
      outcomes
                                • 120m people infected in >80
3.    Key definitions             countries in Africa, Asia, the
4.    Epidemiology
5.    Burden of
                                  Pacific islands and South and
      parasitic
      infections
                                  Central America
6.    Classification of
      protozoa
                                • 40m of those infected are
7.    Classification of           disfigured or severely
      helminths
8.    Schistosomiasis             incapacitated
9.    Hookworm
10. Lymphatic
                                • 95% cases due to
    filariasis
                                  Wuchereria bancrofti, other
11. Sources of
    information                   species include Brugia malayi
                                  and Brugia timori                A female Anopheles mosquito taking
                                                                   a blood meal
                                                    Lymphatic filariasis (2)
Partners in Global Health Education



1.    How to use this
      module                    Life cycle
2.    Learning                  •     Wuchereria bancrofti is mainly
      outcomes                        transmitted by
3.    Key definitions                   – Culex mosquitoes in India
4.    Epidemiology                      – Anopheline mosquitoes in Africa
5.    Burden of                 •     B. malayi and B. timori are transmitted
      parasitic                       mainly by Mansonia mosquitoes
      infections
                                •     Larval forms of the parasite
6.    Classification of               (microfilariae) are taken up by a female
      protozoa                        mosquito when it takes a blood meal          Microfilaria of B. malayi in thick
7.    Classification of               from a human infected with adult worms       blood film (H&E stain; source: CDC)
      helminths
                                •     The microfilariae develop inside the
8.    Schistosomiasis                 mosquito
9.    Hookworm                  •     When the mosquito takes another blood
10. Lymphatic                         meal the infective filariform larvae enter
    filariasis                        the bite wound
11. Sources of                  •     Filariform larvae migrate to the
    information                       lymphatics and lymph glands
                                •     Larvae develop into sexually mature
                                      adult worms over 3-12 months
                                      depending on the species of filarial
                                      worm                                          Adult worms of B. malayi in section in a
                                                                                    lymph node (source: Univ South
                                                                                    Carolina)
                                                 Lymphatic filariasis (3)
Partners in Global Health Education



1.    How to use this
      module
                                  Pathology
2.    Learning                    • Adult worms live in the afferent
      outcomes
                                     lymphatic vessels and cause
3.    Key definitions
                                     severe disruption to the
4.    Epidemiology
5.    Burden of
                                     lymphatic system
      parasitic
      infections
                                  • Scrotal damage and massive
6.    Classification of
                                     swelling may occur when adult
      protozoa                       Wuchereria bancrofti lodge in
7.    Classification of              the lymphatics of the spermatic
      helminths
8.    Schistosomiasis
                                     cord
9.    Hookworm                    • Late stage disease is typified
10. Lymphatic                        by elephantiasis – painful and
    filariasis
                                     disfiguring swelling of the limbs
11. Sources of
    information                   • Trauma and secondary
                                     bacterial infection of affected
                                                                         Elephantiasis of the leg
                                     tissues is common                   (source: WHO/TDR/Crump)
                                                    Lymphatic filariasis (4)
Partners in Global Health Education



1.    How to use this          Symptoms and signs – 3 stages
      module
                               1. Asymptomatic stage
2.    Learning
      outcomes                 •   There is internal damage to the lymphatics
3.    Key definitions
                                   and kidneys
4.    Epidemiology
                               2. Acute stage – Filarial lymphangitis
5.    Burden of
                               •   Characterised by bouts of fever
      parasitic                •   heat, redness, pain, swelling and
      infections                   tenderness of the lymph nodes and ducts
6.    Classification of        3. Chronic stage
      protozoa
                               •   Usually results in elephantiasis as a result
7.    Classification of
      helminths                    of chronic lymphoedema
8.    Schistosomiasis          •   There is a massive overgrowth of tissue
                                   resulting in severe deformities
9.    Hookworm
10. Lymphatic
                               •   The legs are often affected and result in
    filariasis                     inability to walk
11. Sources of                 •   The scrotum is often affected in men and
    information                    the breasts and vulva in women


                                                                                  Elderly male with massive hydrocoele, and
                                                                                  elephantiasis of the leg. Also has nodules in the groin
                                                                                  due to onchocerciasis (source: WHO/TDR/Crump)
                                                 Lymphatic filariasis (5)
Partners in Global Health Education



1.    How to use this             Diagnosis                                         Prevention and control
      module                      •   Microscopic examination of Giemsa stained     • Rapid diagnosis and treatment
2.    Learning                        thick blood films for the presence of
      outcomes                                                                         of infected individuals
                                      microfilariae
3.    Key definitions             •   W. bancrofti shows marked nocturnal           • Mass drug administration to at
4.    Epidemiology                    periodicity, so it’s best to collect blood       risk communities
5.    Burden of                       samples between 10pm and 1 am                 • Vector control: eliminate
      parasitic
                                  •   Serology                                         mosquito breeding sites
      infections
6.    Classification of
                                                                                       through improved sanitation
      protozoa                    Treatment                                            and enviromental
7.    Classification of           •   Diethylcarbamazine (DEC) rapidly kills           management
      helminths                       microfilariae and will kill adult worms if    • Personal protection against
8.    Schistosomiasis                 given in full dosage over 3 weeks                mosquito bites by insecticides,
9.    Hookworm                    •   Release of antigens from dying microfilaria      bednets and repellants
10. Lymphatic                         causes allergic-type reactions – add an
    filariasis                        antihistamine and aspirin to treatment
11. Sources of                        regimen
    information
                                  •   Other treatment options are
                                        –  ivermectin
                                        –  combination of DEC and albendazole
                                             Sources of information
Partners in Global Health Education



1.    How to use this

2.
      module
      Learning
                                  • The Special Programme for Research and
      outcomes
                                    Training in Tropical Diseases (TDR UNICEF,
3.    Key definitions
4.    Epidemiology                  UNDP, World Bank, WHO) website:
5.    Burden of
      parasitic
                                    ww.who.int/tdr/media/image.html
      infections
6.    Classification of
                                  • University of South Carolina School of Medicine:
      protozoa
7.    Classification of
                                    http://pathmicro.med.sc.edu/book/parasit-
      helminths                     sta.htm
8.    Schistosomiasis
9.    Hookworm                    • Lecture notes on Tropical Medicine, Dion R Bell,
10. Lymphatic
    filariasis                      Fourth edition, 1996, Blackwell Science.
11. Sources of
    information                   • Parasites and human disease, W. Crewe and
                                    D.R.W. Haddock, 1985, First edition, Edward
                                    Arnold.