Pathophysiology of Parasitic Infections

Question 1

seeks to explain the functional changes that are occurring within an individual due to a disease or pathologic state. The effects caused by parasitic diseases may be so subtle as to be unrecognizable, or they may be strikingly obvious

Answer 1

Pathophysiology

Question 2

When the balance between host and parasite is tipped in favor of the parasite , a (?) results

Answer 2

disease

Question 3

On the other hand, if the balance shifts in favor of the hosts ability to inhibit the parasite, the (?) will be damaged and eliminated

Answer 3

parasite

Question 4

(?) refers to the ability of an infectious agent to gain entry to the host’s tissues and bring about a physiological or anatomical change, resulting in altered health and leading to disease.

Answer 4

Pathogenicity

Question 5

The factors that contribute to parasite pathogenicity include:

Answer 5

parasite load, tissue tropism, and pathogenesis

Question 6

The (?) (also referred to as worm burden among the helminths) refers to the number of parasites in or on the host.

Answer 6

parasite

Question 7

This determines the likelihood of the parasitic disease.

Answer 7

parasite load

Question 8

Usually, the greater the number of (?) that enter the host, the greater will be the pathological damage.

Answer 8

parasite infective stages

Question 9

However, a few parasites that have (?) within the host can also have a considerable effect on the host

Answer 9

reproductive phase

Question 10

reflects the ability of a given parasite to infect a specific organ or sets of organs

Answer 10

Tissue tropism

Question 11

After entering the host, the parasite migrates to these parts of the body where conditions are suitable for (?).

Answer 11

temporary or permanent residence

Question 12

Some pathogens are broadly (?), infecting all or most organs, while others are restricted to a giventissue or even to
certain tissue niches.

Answer 12

tropic

Question 13

refers to the manner of development of a disease.

Answer 13

Pathogenesis

Question 14

The pathogenic mechanisms of parasites are many and varied, but for the sake of convenience they can be discussed under the headings of:

Answer 14

a. Spoliative action
b. Traumatic or mechanical damage
c. Lytic necrosis
d. Toxic and allergic phenomena
e. Stimulation of host’s tissue reaction
f. Secondary invasion

Question 15

(?) with parasites robs the host of essential nutrients and substances.

Answer 15

Infection

Question 16

Depleting or denying the host of these leads to (?) and in the process causing damage to surrounding tissues.

Answer 16

malnutrition

Question 17

Malnutrition is more likely to occur in individuals with large burdens of parasites. The effects include

Answer 17

stunted growth, wasting, hunger, or more specific signs of micronutrient deficiency.

Question 18

Some parasites compete with the host by (?), others by (?), a variety of nutrients from the host.

Answer 18

absorbing
ingesting

Question 19

The tapeworm (?) can absorb vitamin B12 from the contents of the host’s gut against a concentration gradient.

Answer 19

Diphyllobothrium latum

Question 20

Since (?) is necessary for erythrocyte production and maturation, its deficiency may result in megaloblastic anemia.

Answer 20

vitamin B12

Question 21

(?) attach to the intestinal mucosa by means of teeth or cutting plates.

Answer 21

Hookworms

Question 22

Aside from the bleeding at the site of attachment, hookworms ingest human blood, which results in

Answer 22

iron-deficiency anemia.

Question 23

In other instances, parasites could contribute to malnutrition by

Answer 23

decreasing host nutrient intake, increasing nutrient excretion, and/ or decreasing nutrient utilization

Question 24

The tiny protozoan (?) robs its host in a different way.

Answer 24

Giardia lamblia

Question 25

It is concave on its ventral surface and applies this suction cup to the surface of an intestinal epithelial cell.

Answer 25

Giardia lamblia

Question 26

When many of these parasites are present, they cover so much intestinal absorptive surface that they interfere with the host’s absorption of nutrients. The unused nutrients then pass uselessly through the intestine and are wasted

Answer 26

Giardia lamblia

Question 27

A scanning electron micrograph of the surface of the small intestine of a gerbil infested with Giardia sp. protozoa. The (?) is almost entirely obscured by the attached Giardia trophozoites.

Answer 27

intestinal epithelial surface

Question 28

(?), or destruction of cells, tissues or organs brought about by parasite attachment, feeding, blockage, or migration by is common in parasite infections.

Answer 28

Physical trauma

Question 29

The attachment of hookworms into the host intestinal mucosa by their teeth or cutting plates results into traumatic destruction of the (?) and bleeding at the site of attachment.

Answer 29

villi

Question 30

Large numbers of Ascaris lumbricoides worms form tangled mass called (?) that can lead to intestinal obstruction.

Answer 30

bolus

Question 31

It is also known to migrate and enter the appendix, ciliary and pancreatic ducts, or the common bile duct, perforate the intestinal wall, or may penetrate the parenchyma of the liver and even the lungs.

Answer 31

Ascaris lumbricoides

Question 32

Another pathogenic mechanism is by interference with the vital processes of the host through

Answer 32

parasitic enzymes.

Question 33

Enzymes elaborated by many parasites do not only make it possible for them to (?) in the immediate environment and to transform this nutrient into their own protoplasm but also to (?) to promote invasion and spread of parasites.

Answer 33

digest available food degrade tissues or cells

Question 34

The dysentery amoeba, (?), trophozoites that secrete cysteine proteinases which do digest cellular materials and the mucosa of the large intestine, forming ulcers and abscessed pockets that can cause severe disease.

Answer 34

Entamoeba histolytica

Question 35

typical flaskshaped ulcer

Answer 35

intestinal amebiasis

Question 36

The normal secretions and excretions of parasites and the products liberated from dead parasites accumulate in the host tissues and become toxic to the host, behave like foreign proteins and give rise to various

Answer 36

allergic manifestations

Question 37

Lysis of the red blood cells parasitized by Plasmodium spp. in malaria unleashes large amounts of waste products and cell debris into the blood, to which the host responds with a sharp rise in (?)

Answer 37

TNF and other pro-inflammatory cytokines

Question 38

(?) and consequent eruption of TNF accounts for the periodicity of the typical paroxysms of chills and fever in malaria

Answer 38

Synchrony of red cell lysis

Question 39

Some manifestations of the immune response are responsible for much of the pathogeneses hosts suffer. Parasites provoke tissue reaction that consists of (?) at the site of the parasite and may involve increase in certain types of cells --- (?)

Answer 39

cellular proliferation and infiltration lymphocytes, neutrophils, and macrophages.

Question 40

When (?) are unable to destroy the parasites, since most are too large to be engulfed, one of the end products of an immune response is the formation of (?).

Answer 40

neutrophils and macrophages granuloma

Question 41

This basically consists of a cellular reaction to the presence of parasite which is eventually surrounded by epitheloid cells and multinucleated giant cells and as it dies off, calcium is deposited within the cell.

Answer 41

Granuloma

Question 42

the physical presence of such structure may block fluid flow and lead to necrosis of the surrounding tissues

Answer 42

granuloma

Question 43

A few parasitic infection have been shown to lead to (?).

Answer 43

malignancy

Question 44

The liver fluke, (?), may induce bile duct carcinoma

Answer 44

Clonorchis sinensis

Question 45

(?) may cause urinary bladder cancer

Answer 45

Schistosoma haematobium

Question 46

A parasite may open pathways in the skin or gastrointestinal tract for the entry of other pathogens in the tissues

Answer 46

Secondary invasion

Question 47

In some helminthic infections, the migrating larvae may carry viruses and gram-negative bacteria from the intestines to the blood and tissues, as in

Answer 47

strongyloidiasis, trichinosis, and ascariasis.

Question 48

pathogenic parasites are endowed with special properties that enable them to cause disease if given the right opportunity. Because of the possibility of recovery after a parasitic disease, there is no doubt that a host has protective mechanisms against the parasites.

Answer 48

Host Defense

Question 49

two types of host defense:

Answer 49

innate and adaptive

Question 50

parasites are well adapted to resisting

Answer 50

host innate defenses

Question 51

are critical in attempts by the host to control such infections.

Answer 51

Adaptive responses

Question 52

Distinctive host responses to parasitic infections, especially in helminth infections, are (?) - an increase in the number of eosinophils in the blood or tissues, and elevated serum IgE level.

Answer 52

eosinophilia

Question 53

Their primary function is considered to be defense against organisms that are too large to be phagocytosed, particularly parasitic helminths.

Answer 53

eosinophils

Question 54

Eosinophils and IgE play a critical role in what is known as (?), a particularly important mechanism against parasites.

Answer 54

antibody-dependent cellular cytotoxicity (ADCC)

Question 55

bind to the surface antigens of the parasite and eosinophils attach to the Fc portion of the IgE triggering eosinophil degranulation.

Answer 55

IgE antibodies

Question 56

The toxic products of the (?) can either kill, damage, or dislodge the parasite as a protective host mechanism.

Answer 56

released eosinophil granules

Question 57

(?) with parasitic infections differ significantly from that in viral and bacterial infections.

Answer 57

Acquired immunity

Question 58

(?) against parasitic infections is much less efficient and not absolute. It is apparent from the chronic course and recurrences of parasitic infections.

Answer 58

Immunological protection

Question 59

(?) provide their human host an intense antigenic challenge because they are more antigenically complex than bacteria or viruses

Answer 59

Parasites

Question 60

Several factors may contribute to this:

Answer 60

• Large size. • More complex structure. • Metabolic diversity. • Complicated life cycle. • Have evolved to be closely adapted to the host.

Question 61

This immunity, either complete or partial, may be maintained only while the parasites are present—the phenomenon is known as (?) (or concomitant immunity).

Answer 61

premunition

Question 62

The parasites remain alive, but its reproduction and other activities are restrained by the (?).

Answer 62

host response

Question 63

Once the parasitic infection is completely eliminated, the host becomes again (?) to reinfection.

Answer 63

susceptible

Question 64

Parasites could not survive in their hosts if they could not evade the host defenses mounted by immune responses. As noted earlier, parasites have evolved in relation their host. Consequently, they have developed numerous ways to overcome the host's defense mechanisms.

Answer 64

Parasite Immune Evasion Mechanism

Question 65

Many parasites inhabit body sites that are inaccessible to immune response.

Answer 65

Seclusion

Question 66

Some parasites persist in the (?) of the gastrointestinal tract, oral cavity, or urinary tract.

Answer 66

lumen

Question 67

Unless the integrity of the intestinal mucosa is breached by injury or inflammation, this barrier protects lumen-dwelling parasites, many of which are surrounded by a protective tegument, or (?), from most of the effective humoral and cellular immune mechanisms of the host allowing survival and the opportunity to reproduce.

Answer 67

cuticle

Question 68

Some parasites can avoid exposing themselves to immune response by becoming (?).

Answer 68

intracellular

Question 69

inhabit erythrocytes and are able to avoid the effect of antibodies.

Answer 69

Plasmodium spp.

Question 70

Those that parasitize (?) possess mechanisms to avoid destruction.

Answer 70

macrophages

Question 71

proliferate in macrophages in various organs because they are able to inhibit the fusion of lysosomes with the parasitecontaining phagosome.

Answer 71

Amastigotes of Trypanosoma cruzi and Leishmania spp.

Question 72

One way parasites can avoid forces of immune response is by periodically changing antigens of their surface coat, i.e., to undergo

Answer 72

antigenic variation

Question 73

It may occur with developmental changes in parasite.

Answer 73

antigenic variation

Question 74

pass through several discrete developmental stages, each with its own particular antigens.

Answer 74

Plasmodium spp.

Question 75

Immune responses directed at an early developmental stage may be totally (?) against a later stage of the same parasite.

Answer 75

ineffective

Question 76

Even more intriguing is the ability of some parasites to vary the antigenic characteristics of a

Answer 76

single developmental stage.

Question 77

have the capacity to express more than 100 different surface glycoproteins. By the time the host has mounted a response against each new antigen, the parasite antigen has changed again.

Answer 77

Trypanosoma brucei

Question 78

A number of parasites are able to coat themselves with host molecules. In this way, they are able to hide their own antigenic surface from the immune system

Answer 78

Antigenic disguise

Question 79

may immunologically hide from the host by masking themselves with host blood group antigens and immunoglobulins.

Answer 79

adult schistosomes

Question 80

Resemblance between parasite antigen and host antigen is referred to as

Answer 80

molecular mimicry

Question 81

Some parasites have the (?) to synthesize antigens identical to those of its host.

Answer 81

genetic information

Question 82

Parasites produce substances that are transported to their (?) that mimic substances naturally found within the host.

Answer 82

tegument

Question 83

In this case the antigenic determinants of the parasite are so closely related chemically to (?) that the immunological cells cannot distinguish between the two and an immune response cannot be raised.

Answer 83

host "self" components

Question 84

The larval stage of (?) in the hydatid cyst has been found to carry P blood group antigen, and the tegument of Schistosoma spp. adult can acquire antigenic molecules from the host.

Answer 84

Echinococcus granulosus

Question 85

Parasites liberate antigenic surface components and, later, regenerating them. The antigens shed are able to combine with and (?) before they reach the target parasite.

Answer 85

neutralize antibodies

Question 86

Parasites can reduce the immune function by destruction of immunologic mediators. This means that the host shows depressed immune responses to antigens in general, including those of the infecting pathogen. 

Answer 86

Immunosuppression

Question 87

Tapeworm larvae produce

Answer 87

anticomplementary chemicals

Question 88

(?) splits the Fc component of attached antibodies, rendering it incapable of activating complement.

Answer 88

Trypanosoma cruzi

Question 89

Several protozoa, most notably (?) that are responsible for African sleeping sickness, induce polyclonal B-cell activation leading to the production of nonspecific immunoglobulins and eventual exhaustion of the antibody-producing capacity of the host.

Answer 89

Trypanosoma brucei species

Question 90

often cause anemia.

Answer 90

trypanosomiasis and malaria

Question 91

can result in bowel obstruction

Answer 91

Ascariasis

Question 92

can cause diarrhea.

Answer 92

amoebiasis