C3: Host-Parasite Relationship Flashcards
The relationship between the parasite and the host, may be divided into what following types ?
Symbiosis, Mutualism, Commensalism
When the direction moves ______ direction, means that there is a reestablishment of the host health.
When the direction moves _____ means the infection of disease happens
upward
downward
is defined as the influence of each partner by the activities of the other.
Host Parasite relationship
- The person who is infected with the parasite without any clinical or subdisease is referred to as a carrier. He can transmit the parasites to others.
Carrier State
- The disease is the clinical manifestation of the infection, which shows the active presence, and replication of the parasite causing damage to the host. It may be mild, severe and fulminant and in some cases may even cause death of the host.
Disease State
- Occurs when the host gains the upper hand; host recovers from the infection.
Parasite Destruction
In general, the host-parasite relationship can be studied under two heads:
Effects on the Parasite
Effects on the Host
What Direct Effects of Parasite on the Host?
- Parasites compete with the host for nutrients
Deprivation of nutrients, fluids & metabolites
What Direct Effects of Parasite on the Host?
- Some parasites destroy (injure) the host’s tissue when they enter the host, and others inflict tissue damage after they have successfully entered
- Parasites also infects the host by means of pressure/blockage at it grows larger
Mechanical Injury and Tissue Damage
What Direct Effects of Parasite on the Host?
- Another possible consequences of parasitism associated with cell and tissue parasites is a change in the growth pattern of the affected tissue. Some of these are serious changes, whereas others are structural and have no serious systemic importance to the whole organism.
Abnormal Growth
In abnormal growth, such changes can be broadly divided into four main types:
a. _____(Increase in the rate of cell division):
b. ____(Increase in cell size):
c. _______ (Transformation of one type of tissue into another):
d. ______ (Cancer or tumour formation):
Hyperplasia
Hypertrophy
Metaplasia
Neoplasia
What Direct Effects of Parasite on the Host?
- Specific toxins or poisons, egested, secreted or excreted by parasites have been sited in many cases as the cause of irritation and damage to hosts.
Deleterious effect of toxic substances
What Direct Effects of Parasite on the Host?
- Some ectoparasites carries other pathogens that may cause other infection.
Transmission of Pathogen to Man
What Indirect Effects of Parasite on the Host?
- Majority of the hosts build resistance or immunity against the parasite and they show no visible effects. Immunity may be natural or acquired by previous infections.
Immunologic Reaction
if a host is easily parasitized by a certain species, it is said to be _____, whereas if it is difficult to parasitize, it is called as _____
tolerant; refractory
A host that is frequently found parasitized by a certain species in nature – ______, whereas one that does not become so parasitized is called _____.
Natural host; foreign host
If a species of parasite that habitually lives in or on a host that is very seldom infected that is spoken as an ______
accidental or casual host.
host may become infected but throw off the infection after a short time is known as provisional transitory host; or it may serve as a host for short stage in life cycle of a parasite – _____
temporary host.
_________ is the study of the immune system and is a very important branch of the medical and biological sciences.
Immunology
The _____ protects us from infection through various lines of defences.
immune system
- State of being immune or resistant to a particular infectious disease.
Immunity
- is the first line of defence and is non-specific.
- responses are the same for all potential pathogens, no matter how different they may be; includes physical barriers (e.g. skin, saliva etc) and cells (e.g. macrophages, neutrophils, basophils, mast cells etc).
Innate immunity
occurs inside infected cells and is mediated by T lymphocytes.
Cellular immunity -
-The ___________ deals with antigens from pathogens that are freely circulating, or outside the infected cells.
humoral immune system
- is the second line of defence which involves building up memory of encountered infections so can mount an enhanced response specific to the pathogen or foreign substance.
Adaptive immunity
- also called antibody-mediated immunity. With assistance from helper T cells, B cells will differentiate into plasma B cells that can produce antibodies against a specific antigen.
Humoral immunity
What Immune Evasion Mechanism?
Surface membrane antigens of the parasites bound to the antibodies undergo redistribution so that the parasite is covered by a folded membrane that later extrude as a cap containing most of the antibodies that were originally bound to the membrane
Antigenic shedding (capping):
What Immune Evasion Mechanism?
: By change of antigenic composition, the parasites can be protected from the antibodies which are formed against the original antigens
Antigenic variation
What Immune Evasion Mechanism?
The adult flukes of Schistosoma get coated with the host red cell antigens and histocompatibility antigens, so that they are not recognized as foreign and live free from host attack
Antigenic mimicry:
What Direct Effects of Parasite on the Host??
Diphyllobothrium latum (Dibothriocephalus latus) in man has been known to cause an anemia similar to pernicious anemia, because of the affinity this tapeworm has for Vitamin B12.
Deprivation of nutrients, fluids & metabolites
What Direct Effects of Parasite on the Host??
The infective larva of the nematodes such as Necator americanus & Ancylostoma duodenale do extensive damage to cells and underlying connective tissue during penetration of the host’s skin.
Mechanical injury and Tissue damage
What Direct Effects of Parasite on the Host??
Various armed helminths such as Acanthocephala, certain flukes and tapeworms, initially damage the cells lining the lumen of their host’s intestine which they are holding
Mechanical injury and Tissue damage
What Direct Effects of Parasite on the Host??
Cercarial dermatitis an severe allergic reaction causes substances releases by Schistosoma cercaria
Deleterious effect of toxic substances
Nephretic syndrome and allergy development are examples of what indirect effect of parasite to host??
Immunologic Reaction
What are the Host factors that affect the development of certain diseases in the individual;
- Genetic constitution
- Age
- Sex
- Level of immunity
- Nutrition (malnutrition or undernourished)
- Intensity & frequency of infection
- Co-existing disease or condition
- Lifestyle & occupation
What are the parasite factors that affect the development of certain diseases in the individual;
- Strain of the parasite & adaptation to human host
- Parasite load (number of parasite)
- Site/s occupied in the body
A ____ is capable of living an independent life
commensal
Enumerate the effects on parasite
Effects of Nutrition
Effects of Hormones
Effects of Age
Effects of Immunity
Effects of Host specificity
Effects of parasitic density
Effects of Host sex
