8. SYMBIOSIS

9. • Phoresis, commensalism, mutualism, and
parasitism
• If we consider the degree of the
association, then phoresis and
commensalism represent “loose”
associations, where as mutualism and
parasitism indicate “intimate” associations

10. 1 .Phoresis (Phoresy)
• Phoresis means “to carry.”
• A type of symbiotic relationship in which one
organism (the smaller phoront) is mechanically carried
on or in another species (host).

11. 2. Commensalism
• Means “eating at the same table”
• Occurs when one member of the associating
pair, usually the smaller, receives all the benefit and the
other member is neither benefited nor harmed
Branchiobdelid worm
attached to a crayfish

12. 3. Mutualism
• Occurs when each member of the association
benefits the other
• Mutuals are metabolically dependent on one
another; one cannot survive in the absence of
the other
• Often included as a special subcategory of
mutualism is cleaning symbiosis
• In this relationship, certain animals
known as cleaners, remove
ectoparasites, bacteria, diseased and
injured tissue from cooperating hosts
Honeybee bringing pollen to a desert shrub

13. 4. Parasitism
• Parasitos (para: beside; sitos: grain or food)
•Definitions of parasitism have traditionally focused
upon some ecological aspect of the parasite-host
interaction
Anterior end of a hookworm

15. Parasite -refers to organism that
lives in or on other living
organisms (Hosts), at whose
expense the parasite gain some
advantages of obtaining shelter
and food.

16. In this course we will
concentrate on 3 major groups
of parasites:
1. Protozoa-
flagellates, amebas, malarial
organisms
2. Helminths - parasitic worms
such as the flukes,
tapeworms, and
roundworms
3. Arthropods - insects and
arachnids that are ectoparasites
and carriers (vectors) of diseases

17. PARASITE AND THE TYPE OF
PARASITES

18. Human parasites are either unicellular
(protozoa)
or multicellular (helminthes and
arthropods.
 Accdg. to their habitat:
Endoparasites: Parasites that live within
(inside) the body of other organisms.
Ectoparasites: Parasites that exist on the
body surface (outside the host`s body) of
other organisms
Erraticparasites– a parasite found in an
organ which is not its usual habitat.

19.  Accdg. to their mode of development:
• OBLIGATE PARASITES – needs a host at some
stage of their life cycle to complete their development
and to propagate their species.
*Tapeworms which depend entirely upon their host for
existence.
• FACULTATIVE PARASITE – capable of free-living
existence and may become parasitic when the need
arises.

20. • ACCIDENTAL/INCIDENTAL PARASITE –
establishes a relationship to a host where it does not
normally live.
• PERMANENT PARASITE – spends most or the
rest of its adult life cycle on or in its host.
• TEMPORARY/INTERMITTENT PARASITE –
lives on or in the parasite only when the need arises.
• CUPROZOIC/SPURIOUS PARASITE – free-
living parasite which passes thru the alimentary tract
without infecting the host.

21. HOST AND TYPES OF HOST
 Hosts: The organisms that harbor the parasites and may suffer a loss such as
diseases
 caused by the harbored parasite.
 A host is determined and differentiated according to their role in the life cycle
of the parasite.

22. TYPES OF HOST
 Definitive host: The host in which the parasite survives its adult and
sexual stages.
 Intermediate host: The host in which a parasite lives a larval or asexual
stage as a
part of its life cycle.
 Paratenic/ transport host– bridges the gap between intermediate and
definitive host.
 Reservior host – hosts that allow the parasite’s life cycle to continue and
become an additional source of human infection.

24.  causes injury
 PARASITES ----- harbour in -------- HOST
 produce an immune response

25. E F F E C T S O F PARASITE T O T H E H O S T
PATHOLOGICAL EFFECTS:
 Deprives the Host of its Esential Nutrition
Hookworms Suck blood Anemia
 Mechanical Effects of the Parasite on the Host
Ascaris Perforate/Obstruction
 Toxic and Immunological Effects
Protozoa Proteolytic Enzymes Necrosis
OTHER EFFECTS:
 Causes Social “stigma” and inconvenience

26. EFFECTS OF THE HOST
TO THE PARASITE
 Immune Response Damages the Parasite
 Auto-antibodies serve as protective barriers
• Sicke-cells and Duffy Blood Groups
 Nutrition of Host Affects Parasite Growth