Download Introduction to Parasites: Classification, General Characteristics of

Classification, General Characteristics of parasites
and Medically important Parasites
Parasites
Endoparasite
Protozoa
Metazoa
Ectoparasite
Arthropods
Sub
kingdom
Phylum
Protozoa
Sarcomastigophora
further divided into
Sub-phylum
Sarcodina-- -
Genusexamples
Speciesexamples
Entamoeba
E. histolytica
Giardia
G. lamblia
Plasmodium
P. falciparum,
P. vivax,
P. malariae,
P. ovale
Balantidium
B. coli
Enterocytozoa
E. bienusi
move by
pseudopodia
Mastigophora
move by flagella
Apicomplexa
no organelle of
locomotion
Ciliophora
move by cillia
Microspora
Spore-forming
Classification of Metazoa
Sub
kingdom
Metazoa
Phylum
Class
Genus –
examples
Ascaris (roundworm)
Trichuris (whipworm)
Ancylostoma (hookworm)
Necator (hookworm)
Enterobius (pinworm or
threadworm)
Strongyloides
Nematodes
Round worms; appear round
in cross section, they have
body cavities, a straight
alimentary canal and an
anus
Platyhelminthes
Cestodes
Flat worms; no body cavity
and, if present, the
alimentary canal is blind
ending
Adult tapeworms are found in
the intestine of their host
They have a head (scolex) with
sucking organs, a segmented
body but no alimentary canal
Each body segment is
hermaphrodite
Trematodes
Non-segmented, usually leafshaped, with two suckers but
no distinct head, they have an
alimentary canal
Schistosomes are the
exception, thread-like, and
have separate sexes
Taenia (tapeworm)
Fasciolopsis (liver fluke)
Schistosoma (not leaf
shaped!)
The most common parasitic infection
Parasite
Plasmodium
Diseases
malaria
Soil transmitted helminths:
•
Roundworm (Ascaris)
intestinal obstruction
•
Whipworm (Trichuris)
Bloody diarrhoea, rectal prolapse
•
Hookworm
(Ancylostoma and
Necator)
Coughing, wheezing, abdominal pain
and anaemia
No. cases
Deaths/yr
273 million
1.12 million
2 billion
200,000
Schistosom
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
14,000
African trypanosomes
African sleeping sickness
0.3 – 0.5 million
48,000
Leishamania
Cutaneous, mucocutaneous and
visceral leishmaniasis
12 million;
2 million new
cases/yr
50,000
• Intestinal
– Amebiasis .............................. Entamoeba histolytica
– Giardiasis ...............................Giardia lamblia
– Balantidiasis .......................... Balantidium coli
– Crytosporidosis ..................... Cryptosporidium parvum
– Cyclosporiasis …………………….. Cyclospora cayetanensis
• Genitourinary tract
– Trichomoniasis ....................... Trichomonas vaginalis
• Blood and Tissue
– Malaria ................................... Plasmodium spp
– Meningoencephalitis ............. Naegleria fowleri
– Toxoplasmosis ........................ Toxoplasma gondii……….. (Eye)
• Cardiovascular system
– African Sleeping Sickness ...... Trypanosoma brucei…….. (CNS)
– Chagas Disease ...................... Trypanosoma cruzi
• Skin and mucous membrane
– Visceral leishmaniasis( Kala-azar) ... Leishmania donovani
– Cutaneous leishmaniasis .......... Leishmania topica/braziliensis
Medically important Protozoan Diseases
• Gastrointestinal infections
– Amebiasis
 Observed ingegsted RBCs indicate pathogenic E. histolytica
– Giardiasis
 By Giardia lamblia, an intestinal flagellate
 A diarrheal disease
 + Person to person by soiled hands to mouth
– Balantidiasis
 By Balantidium coli , the only ciliated protozoan that causes human infection
– Crytosporidosis
 By Cryptosporidium parvum
 A diarrheal disease
 + Person to person + animal to person
– Cyclosporiasis
 By Cyclospora cayetanensis
 Transmission is Primarily waterborne but + ingestion of contaminated raspberries,
basil and lettuce
Medically important Protozoan Diseases
• Genitourinary tract infections
– Trichomoniasis





By Trichomonas vaginalis
A flagellate that has no cyst form
Sexually transmitted disease, STD
Symptomatic in females and Asymptomatic in males
Saline wet mount examination of vaginal or urethral discharge – motile trophozites
Medically important Protozoan Diseases
• Protozoal infections of the eyes
– Amebic Eye infection
– Toxoplasmosis




By Toxoplasma gondii , intracellular sporozoan
Ingestion of raw or undercooked meat containing the cyst
Typically diagnosed by Immuno-Diagnostic Procedures, IDPs
Stained biopsy
Medically important Protozoan Diseases
• Cardiovascular system infections
– African Sleeping Sickness (African trypanosomiasis)
 By Trypanosoma brucei, Hemoflagellates
 Transmitted by Tsetse flies
 Diagnosed by observing trypomastigotes in blood, lymph
node aspirates or CSF
– Chagas Disease (American trypanosomiasis)
 By Trypanosoma cruzi, Hemoflagellates
 Transmitted by infected reduviid bugs, or blood transfusion
 Diagnosed by observing trypomastigotes in blood, lymph
node biopsies or tissue
Medically important Protozoan Diseases
• Skin and mucous membrane
– Visceral leishmaniasis( Kala-azar)
 Leishmania donovani
– Cutaneous leishmaniasis
 Leishmania topica/braziliensis
 Leishmania spp.




Tissue flagellates
Usually transmitted by sandfly
Many animal reservoirs
Diagnosis usually by microscopic identification of non-motile amastigote form
inside macrophages
 Some diagnosis by IPDs
Medically important Protozoan Diseases
• Blood and Tissue
– Malaria
 Causing 1.5 million deaths annually
 Plasmodium spp:
•




P. vivax, P. falciparum, P. ovale, P. malariae
Intraerythrocytic sporozoan parasites
Transmitted by the bite of infected Anopheles mosquitoes
Mosquitoes are definitive hosts, and humans are intermediate hosts
Malaria is diagnosed by observing trophozoites, sporozoites, or gametocytes
in stained blood smears
Medically important Protozoan Diseases
Arthropod Involvement in Human Diseases
Type of involvement
Examples
A- Cause of the disease
Scabies, microscopic mites lives in
subcutaneous tunnels and cause intense
itching
B- Intermediate host in the life cycle of
a parasite
Mosquito in the transmission of filariasis
C- Definitive host in the life cycle of a
parasite
Female Anopheles mosquito in the life
cycle of malarial parasites
D- Vector (either mechanical/biological)
in the transmission of an infectious
disease
Tick in the transmission of Rocky
Mountain spotted fever and Lyme disease
Arthropods that serve as vectors of human
infectious diseases
Vectors
Disease(s)
Blackflies (Simulium spp.)
Onchocerciasis (River blindness) (H)
Cyclops spp.
Fish tapeworm infection (H), guinea worm infection (H)
Fleas
Dog tapeworm infection (H), endemic typhus (B), murine
typhus (B), Plague (B)
Lice
Epidemic relapsing fever (B) epidemic typhus (B), trench
fever (B)
Mites
Rickettsial pox (B), scrub typhus (B)
Mosquitoes
Dengue fever (V), filariasis (elephantiasis) (H), malaria (P),
viral encephalitis (V), yellow fever (V)
Sandflies (Phebotomus spp.)
Leishmaniasis (P)
Tsetse flies (Glossina spp.)
African Trypanosomiasis (P)
Ticks
Babesiosis (P), Lyme disease (B), tularemia (B), Colorado tick
fever (V)
laboratory Methods For Parasites In stool
• Faecal specimens may contain several stages of Parasites
• The stages of protozoa found in stools are trophozoites and
cysts
• The stages of helminthes usually found in stools are eggs,
larvae, adult’s worms or segments of worms
Intestinal protozoal infections diagnosed by
examining stool specimens
Infection
• Amebiasis
• Balantiadiasis
• Cryptosporidiosis
• Cyclosporiasis
• Giardiasis
Observation required for Diagnosis
• Trophozites (amebas) and/or cyst
• Trophozites and/or cyst
• Oocycts
• Oocycts
• Trophozites and/or cyst
Intestinal protozoal infections diagnosed by
examining stool specimens
Infection
• Amebiasis
• Balantiadiasis
• Cryptosporidiosis
• Cyclosporiasis
• Giardiasis
Observation required for Diagnosis
• Trophozites (amebas) and/or cyst
• Trophozites and/or cyst
• Oocycts
• Oocycts
• Trophozites and/or cyst
Examples of protozoal infections diagnosed by
examining stained blood smears
Infection
• African trypanosomiasis
Observation required for Diagnosis
• Extracellular trypomastigotes
• American trypanosomiasis
• Extracellular trypomastigotes
• Babesiosis
• Intraerythrocytic protozoa
• Malaria
• Intraerythrocytic protozoa
Laboratory Methods For Parasites diagnosis
• Collection of faecal specimens:
 The container should be free from antiseptics and
disinfectants
 Add some form of preservative
• Microscopic Examination of Wet Mount
• The basic types of wet mount that should be used for each
faecal examination are saline, iodine, and buffered
methylene blue
General aspects about parasite treatment and
control
• Importance of understanding parasite life cycles for effective
treatment and control
– Life cycle involves one or more species of vector
– Life cycle involves one or more intermediate hosts
– Parasite has a variety of definitive hosts
– Parasite has life cycle stages that are exposed to the
environment
– Sequence and timing of life cycle stages within a host
– Location within host
General aspects about parasite
treatment and control
Direct life cycle
– Importance in treatment/ control
• Provision of sanitation and basic hygiene practices can
prevent many gastrointestinal parasitic diseases
– Application of life cycle knowledge
• Washing fruit and vegetables in clean water can
remove protozoan cysts and helminth eggs
General aspects about parasite
treatment and control
Life cycle involves one or more species of vector
– Importance in treatment/ control
• Disease transmission can be controlled by targeting the vectors
– Application of life cycle knowledge
• Bed-nets can prevent mosquitoes transmitting malaria
General aspects about parasite
treatment and control
Life cycle involves one or more intermediate host
• Importance in treatment/ control
– Disease transmission can be controlled by targeting the
intermediate hosts
• Application of life cycle knowledge
– Drainage to remove the habitat of snail intermediate hosts
of Fasciola hepatica
General aspects about parasite
treatment and control
Parasite has a variety of definitive hosts
• Importance in treatment/ control
– Reservoir hosts are a potential source of infection
• Application of life cycle knowledge
– Schistosoma japonicum has numerous reservoir hosts
which can contaminate paddy field etc with eggs
General aspects about parasite
treatment and control
Parasite has life cycle stages that are exposed to the
environment
• Importance in treatment/ control
– Environmental conditions can promote or limit infection
• Application of life cycle knowledge
– Composting can kill the infective stages of many
gastrointestinal parasites
General aspects about parasite
treatment and control
Sequence and timing of life cycle stages within a host
• Importance in treatment/ control
– Optimal time for diagnosis
• Application of life cycle knowledge
– Mf of Wuchereria bancrofti exhibits periodicity
General aspects about parasite
treatment and control
Location within host
•
Importance in treatment/ control
– Optimal time for diagnosis
• Application of life cycle knowledge
– Cattle should be treated for warble fly infections before
the larvae reach their resting site