MODULE 1 Unit 2: Host-Parasite Relationships

Question 1

is largely a study of any two organisms living in close association, commonly one, the parasite, living in or on the body of the other, the host.

Answer 1

Parasitology

Question 2

The study of parasites invariably involves, firstly, the biology of [?], and, secondly, the biology of the [?] — the parasite’s environment.

Answer 2

• parasites

- host

Question 3

Parasitology can be considered to be a specialized branch of [?].

Answer 3

ecology

Question 4

means living together in close association of two phylogenetically different organisms

Answer 4

Symbiosis

Question 5

two phylogenetically different organisms, which are called the [?]

Answer 5

symbionts

Question 6

Symbiotic relationships can be characterized by specifying the nature of the [?] between the symbionts.

Answer 6

interactions

Question 6

is a relationship in which the organisms both benefit from a relationship with each other.

Answer 6

interactionsMutualism

Question 7

The symbionts in mutualism are called [?].

Answer 7

mutualists

Question 8

Mutualism is usually [?], since in most cases physiological dependence has evolved to such a degree that one mutualist cannot survive without the other.

Answer 8

obligatory

Question 9

Termites and their intestinal flagellate, [?], are an excellent example of mutualism.

Answer 9

Trichonympha

Question 10

Termites cannot digest cellulose because they cannot synthesize and secrete the enzyme [?].

Answer 10

cellulase

Question 11

The [?] in a termite’s intestine, however, synthesize cellulase and consequently digest wood eaten by their host.

Answer 11

flagellates

Question 12

The termite uses [?] excreted as a byproduct of the flagellates’ metabolism.

Answer 12

molecules

Question 13

If we kill the flagellates by exposing termites to [?], then the termites starve to death, even though they continue to eat wood.

Answer 13

high temperature or high oxygen concentration

Question 14

In commensalism, the smaller organism – [?] – benefits from the association, but the host is neither benefitted nor harmed.

Answer 14

commensal

Question 15

The term literally means “eating at the same table”.

Answer 15

Commensalism

Question 16

An example of a commensal is [?].

Answer 16

Entamoeba coli

Question 17

This Entamoeba coli lives in the [?] of man, where it feeds on bacteria and food particles, and protected from harm, while it does not cause any damage to the tissues of its host.

Answer 17

large intestines

Question 18

is a relationship in which the parasite, the smaller of the two organisms, benefits and harms the host or in some sense lives at the expense of the host.

Answer 18

Parasitism

Question 19

The host is damaged to a certain degree because of the activities of the parasite.

Answer 19

Parasitism

Question 20

One example of a parasite is [?], which derives nutrition from the human host and causes amoebic dysentery.

Answer 20

Entamoeba histolytica

Question 21

[?] exists when the two symbionts are merely “traveling together,” and there is no physiological or biochemical dependence on the part of either participant.

Answer 21

Phoresis

Question 22

The smaller one in phoresis, the [?], is carried by the larger companion, the host.

Answer 22

phoront

Question 23

This association is mechanical for the purpose of transport from one place to another.

Answer 23

Phoresis

Question 24

An example of this is the association of a house fly that passively transfers an amoeba on its feet from contaminated feces to a plate of food.

Answer 24

Phoresis

Question 25

is defined as the route a parasite follows throughout its life — from the time of entry into the host to exit, including the [?] (outside the host) and subsequent transmission to a new host.

Answer 25

Parasite life cycle

extracorporeal

Question 26

A parasite life cycle consists of two (2) common phases:

1. phase involving the route a parasite follows when [?]
2. phase involving the route a parasite follows [?], i.e. in the outside environment or in a nonhuman host.

Answer 26

• in the human body.

- independently of the human body

Question 27

the route (and also the means) whereby a parasite gains entry into a host

Answer 27

1. Portal of entry

Question 28

the developmental form of the parasite that is capable of entering its host and continuing its development within the host

Answer 28

2. Infective stage

Question 29

predetermined site of development and maturation of the parasite in a host. It is also important to note how the parasite reached its final destination, since migration through the host can cause other symptoms

Answer 29

3. Habitat

Question 30

the route by which the parasite escapes the host

Answer 30

4. Portal of exit

Question 31

the developmental form of the parasite which leaves the host. It is routinely recognized in a biological specimen and thus is crucial in properly identifying the parasite.

Answer 31

5. Diagnostic stage

Question 32

host from which the parasite is immediately transmitted to the host.

Answer 32

6. Source of infection

Question 33

stages where helminths and protozoa pass through during their life cycles.

Answer 33

developmental stages

Question 34

The complete life cycle of helminths includes the

Answer 34

egg, larva, and adult

Question 35

Life cycles involve [?] that copulate and females produce fertile eggs.

Answer 35

sexually differentiated adult worms

Question 36

The eggs undergo [?] developing into a juvenile larva which will hatch out under suitable conditions. Larvae mature into several stages to adults.

Answer 36

embryonation

Question 37

Although the life cycles of protozoa can vary a great deal, they are basically characterized by

Answer 37

trophozoite and cyst

Question 37

are the metabolically active feeding and motile form, which are delicate and do not survive long outside the body; may encyst to become a cyst within a protective coating to tolerate harsh environments.

Answer 37

Trophozoites

Question 38

are the resting, nonmotile, resistant stage of protozoa bounded by tough cell wall to survive adverse environmental conditions, such as desiccation, low nutrient supply, and even anaerobiosis

Answer 38

Cysts

Question 39

can reemerge as a trophozoite when exposed to favorable conditions

Answer 39

Cysts

Question 40

is a major risk factor for infections with intestinal amoebae (e.g., Entamoeba histolytica) or flagellates (e.g., Giardia lamblia)

Answer 40

Ingestion of contaminated water

Question 41

Liquid or semi-formed samples may show trophozoites if the intestinal motility is [?].

Answer 41

rapid

Question 42

Cysts will form, on the other hand, if the intestinal motility is [?] and be passed in formed stool.

Answer 42

normal

Question 43

There are two life cycle patterns, namely:

Answer 43

1. Direct life cycle

2. Indirect life cycle

Question 44

when a parasite requires only single host to complete its development cycle, e.g. Trichomonas vaginalis requires only a human host to complete its life cycle.

Answer 44

1. Direct life cycle

Question 45

when a parasite requires two or more species of host to complete its development.

Answer 45

2. Indirect life cycle

Question 45

is a host that harbors the adult stage of the parasite or where the parasite undergoes a sexual method of reproduction. It is also known as the final host.

Answer 45

1. Definitive host -

Question 46

Sexual reproduction has not been clearly shown in some parasites— such as most protozoa (except the [?])—and in these cases we arbitrarily consider the definitive host the one most important to humans.

Answer 46

apicomplexans

Question 47

is a host in which the larval stage of the parasite lives or where asexual mode of reproduction takes place. In some parasites, two different intermediate hosts may be required to complete different larval stages. These are known as first and second intermediate hosts, respectively.

Answer 47

2. Intermediate host

Question 48

Example of life cycle with one (1) intermediate host.

Answer 48

Taenia species

Question 49

are often but not necessarily vertebrates; malaria parasites, Plasmodium spp., reach sexual maturity and undergo fertilization in mosquitoes, which are therefore by definition their definitive hosts, whereas humans are the intermediate hosts.

Answer 49

Definitive hosts

Question 50

is a host in which the parasite does not undergo further development
but remains viable and infective to another host.

Answer 50

3. Paratenic host

Question 51

It is not necessary for the completion of the parasites life cycle but serves as a temporary refuge and vehicle for reaching an obligatory host, usually the definitive host, thus it is also known as the transport host or phoretic host

Answer 51

3. Paratenic host

Question 52

Example: Fasciola hepatica eggs ingested by humans in contaminated animal liver, being not infective to man, will remain in the same stage of parasite without change and detected in human feces. In this case, [?] serve as a paratenic host.

Answer 52

humans

Question 53

is a host harboring parasites that are parasitic for humans and from which humans may become infected

Answer 53

4. Reservoir host -

Question 54

Example: Fasciola hepatica are primarily parasites of [?], most commonly, sheep, cattle, and goats, which serve as their reservoir hosts.

Answer 54

domestic and wild ruminants

Question 55

is a host that is naturally infected with certain species of parasite

Answer 55

5. Natural host

Question 56

Example: Dogs (also cats) are the normal hosts for [?]. The parasite is transmitted between hosts by ingesting the dog or cat flea containing the [?]

Answer 56

Dipylidium caninum

cysticercoid larvae

Question 57

is a host that is, under normal circumstances, not infected with the parasite. It is also known as incidental host

Answer 57

6. Accidental host

Question 58

Example: Humans are accidental hosts of Dipylidium caninum acquired by ingesting the infected flea, possibly due to [?] with flea-infested pets.

Answer 58

close contact

Question 59

is a host that generally does not allow transmission of the parasite to the next host, thereby preventing the parasite from completing its development.

Answer 59

7. Dead-end host

Question 60

Example of life cycle with two (2) intermediate hosts.

Answer 60

Fasciola hepatica

Question 61

Example of life cycle with natural hosts.

Answer 61

Dipylidium caninum

Question 62

Example of life cycle with accidental hosts.

Answer 62

Dipylidium caninum

Question 63

Example of life cycle with Dead-end hosts.

Answer 63

Trichinella spp.

Question 64

Trichomonas vaginalis resides in the female [?] and the male [?], where it replicates by binary fission .

Answer 64

lower genital tract

urethra and prostate

Question 65

The parasite does not appear to have a cyst form, and does not survive well in the external environment.

Answer 65

Trichomonas vaginalis

Question 66

is transmitted among humans, its only known host, primarily by sexual intercourse .

Answer 66

Trichomonas vaginalis

Question 67

Malaria parasite, [?], requires both human host and mosquito to complete its life cycle.

Answer 67

Plasmodium sp.

Question 68

Adult worms of Ascaris lumbricoides live in the small intestine of man. Therefore, man serves as its

Answer 68

definitive host

Question 69

Taeniasis is the the infection with the adult worm of [?] in the small intestine of human.

Answer 69

Taenia solium or Taenia saginata

Question 70

Humans are the only definitive hosts of these species .

Answer 70

Taenia solium or Taenia saginata

Question 71

Eggs [?] are passed in feces.

Answer 71

(orgravid proglottids)

Question 72

[?] is the intermediate host of T. solium, and cattle for T. saginata. They become infected by ingesting vegetation contaminated with eggs or gravid proglottids .

Answer 72

Pig

Question 73

In the animal’s intestine, the oncospheres hatch , invade the intestinal wall, and migrate to the striated muscles, where they develop into [?]. Humans become infected by ingesting raw or undercooked infected meat .

Answer 73

cysticercus larvae

Question 74

In the human intestine, the cysticercus develops over 2 months into an [?], which can survive for years.

Answer 74

adult tapeworm

Question 75

Trichinellosis is transmitted between animals by consuming infected meat or meat products containing

Answer 75

encysted larvae

Question 76

Humans acquire trichinellosis by consuming [?] infected with the Trichinella larvae.

Answer 76

raw or undercooked meat

Question 77

When a human or animal eats meat which is infected, the larvae are released from the [?] as it is digested and invade the small bowel where they develop into adult worms.

Answer 77

muscle

Question 78

The female worms release larvae that migrate to [?] where they encyst.

Answer 78

striated muscles

Question 79

Because humans typically do not get eaten by other animals, thus will not allow transmission to another host, humans are [?] hosts for Trichinella spp.

Answer 79

dead-end

Question 80

Aside from the taxonomic classification of parasites, parasites can also be categorized according to:

Answer 80

1. Pathogenicity
2. Necessity for host
3. Number of host(s) required
4. Habitat

Question 81

is a parasite that causes injury to the host.

Answer 81

a. Pathogenic parasite

Question 82

is a parasite that does not cause injury to the host; is also termed as commensal.

Answer 82

b. Nonpathogenic parasite

Question 83

a parasite that is absolutely dependent on the host during a segment or all of its life cycle to complete their development and propagate their species.

Answer 83

a. Obligate parasite

Question 84

have developmental forms outside the host, including some periods of time in the external environment.

Answer 84

a. Obligate parasite

Question 85

is one that is capable of independent or a parasitic existence.

Answer 85

b. Facultative parasite

Question 86

Example: Strongyloides stercoralis’ life cycle alternates between
free-living in the soil and parasitic cycles when the filariform
larvae penetrate the human skin and mature in the small
intestine.

Answer 86

b. Facultative parasite

Question 87

Example of life cycle with Facultative parasite -

Answer 87

Strongyloides stercoralis

Question 88

refers to nonparasitic stages of active existence, which live independent of the host

Answer 88

c. Free-living parasite

Question 89

Example: Naegleria fowleri are living in the environment — in fresh water, soil, thermal discharges of power plants, geothermal wells, and poorly-chlorinated recreational and tap water. They are only opportunistically parasitic.

Answer 89

c. Free-living parasite -

Question 90

a parasite that enters or attaches to the body of a species of host different from its normal one. A parasite may or may not continue full development in an accidental host. It is also known as incidental parasite

Answer 90

d. Accidental parasite

Question 91

Example: Dipylidium caninum is an accidental parasite of human following incidental ingestion of infected dog or cat fleas.

Answer 91

d. Accidental parasite

Question 92

is one that remains on or in the body of the host for its entire life.

Answer 92

e. Permanent parasite

Question 93

is one that remains on or in the body of the host for its entire life.

Answer 93

e. Permanent parasite

Question 94

is one that lives on the host only for a short period of time, such as a mosquito or bedbug, only feeds on the host and then leaves

Answer 94

f. Temporary parasite

Question 95

intermittent parasite

Answer 95

f. Temporary parasite

Question 96

is a parasite that is found in or migrates to an organ which is not its usual habitat. It is also referred to as erratic parasite or wandering parasite.

Answer 96

g. Aberrant parasite

Question 97

Example: Toxocara canis or Toxocara cati are intestinal parasites of dogs and cats, respectively. Human become accidental host by ingestion of the eggs from the animal feces. In humans, the eggs hatch and larvae penetrate the intestinal wall and are carried by the circulation to a variety of tissues (liver, heart, lungs, brain, muscle, eyes). The larvae do not undergo any further development in these sites, and cause local reactions and mechanical damage.

Answer 97

g. Aberrant parasite

Question 98

is a parasite that passes through the digestive system without infecting the host

Answer 98

h. Spurious parasite

Question 99

Example: After ingestion of poorly cooked liver from an infected animal harboring eggs of Fasciola hepatica, eggs are transiently present in the stool (spurious or false infection). True fascioliasis is acquired through the ingestion of metacercariae encysted on edible aquatic plants such as Ipomea obscura (“kangkong”) and Nasturtium officinale (watercress).

Answer 99

h. Spurious parasite

Question 100

is one that requires only one (1) host to complete the life cycle.

Answer 100

a. Monoxenous parasite

Question 101

is one that requires more than one (1) host to complete the life cycle. Some heteroxenous parasites pass their life cycles in two (2) hosts, namely a definitive host and a n intermediate host; others, in three (3) hosts, a definitive host and two (2) intermediate hosts – a first intermediate host and a second intermediate host.

Answer 101

b. Heteroxenous parasite

Question 102

is one that uses a single host as definitive host and intermediate host; the definitive host of one generation becomes the intermediate host of the next generation.

Answer 102

c. Autoheteroxenous

Question 103

Example: Trichinella spiralis whereby adult worms and encysted
larvae develop within a single vertebrate host, and an infected
animal serves as a definitive host and potential intermediate
host. A second host is required to perpetuate the life cycle
of Trichinella.

Answer 103

c. Autoheteroxenous

Question 104

is a parasite that is attached to the outer surfaces of its host.

Answer 104

a. Ectoparasite

Question 105

is a parasite that lives within the body of its host.

Answer 105

b. Endoparasite

Question 106

is a parasite that inhabits a cavity of the host’s body.

Answer 106

i. Coelozoic

Question 107

is a parasite that dwells within tissues of the host.

Answer 107

ii. Histozoic

Question 108

is one that parasitic within a cell.

Answer 108

iii. Cytozoic

Question 109

is parasite in the intestine of the host.

Answer 109

iv. Enterozoic

Question 110

is a parasite that lives in the blood.

Answer 110

v. Hematozoic

Question 111

is a parasite living in fecal matter.

Answer 111

vi. Coprozoic

Question 112

Monoxenous [Greek monos, one, unique + Greek xenos, foreign]

Question 113

Enterozoic [Greek [?] , intestine + Greek zôion, animal]

Answer 113

énteron

Question 114

Heteroxenous [Greek [?], other party, another + Greek [?], foreign]

Answer 114

heteros

xenos

Question 115

Hematozoic [Greek [?] , blood + Greek zôion, animal]

Answer 115

haima

Question 116

Coelozoic [Greek [?], hollow, concave + Greek zôion, animal]

Answer 116

koilos

Question 117

Coprozoic [Greek [?], excrement + Greek [?], animal]

Answer 117

kópros

zôion

Question 118

refers to any animate or inanimate object from which the parasite is immediately transmitted to the human host.

Answer 118

source of parasitic infection

Question 119

The most common sources of parasitic infections are

Answer 119

contaminated soil and water

Question 120

Infective stages of parasites may be ingested from contaminated soil, especially among children who play in the contaminated soil and then put their hands in their mouths without washing them (e.g., embryonated eggs of [?]) , or contaminated water (e.g., cysts of [?]); or infective larvae in soil (e.g., [?]) or in water (e.g., cercariae of [?] directly penetrate exposed skin.

Answer 120

• Ascaris lumbricoides
• Giardia lamblia
• filariform larvae of hookworm
• Schistosoma spp.

Question 121

are called geohelminths. In all of them, eggs passed in feces undergo maturation in soil. This means that the soil plays a major role in the development and transmission of the parasite.

Answer 121

Soil-transmitted helminths (STH)

Question 122

are those that are acquired from contaminated water.

Answer 122

Waterborne parasites

Question 123

Distribution of parasites in soil and water is associated with

Answer 123

poor sanitation.

Question 124

generally refers to the provision of facilities and services for the safe disposal of human urine and feces.

Answer 124

Sanitation

Question 125

Lack of access to toilets or latrines is a motivation by compulsion for people to practice the following:

Answer 125

Open defecation (OD) 
Use of night soil

Answer 126

Open defecation (OD) 
Use of night soil

Question 127

the human practice of defecating outside (in the open environment) such as in fields, bushes, forests, ditches, streets, canals or other open space. This leaves feces exposed in ways that can easily lead to other people coming into contact with fecal pathogens.

Answer 127

Open defecation (OD)

Question 128

It became a primary means of waste disposal in areas without sanitation facilities; its use is a risky practice as it may contain disease-causing pathogens. Although controlled by government regulations, it is still widespread in some developing nations.

Answer 128

Use of night soil

Question 129

used as fertilizer for food crops.

Answer 129

human excrement

Question 130

[?] nonhuman hosts containing infective stage of parasite is consumed as food by human.

Answer 130

Raw or undercooked

Question 131

Examples of these food sources and foodborne parasites are:• Kangkong, watercress: Fasciola hepatica
• Pork: 
• Beef: 
• Freshwater fish: 
• Crabs: 
• Snail (kuhol):

Answer 131

• Pork: Taenia solium (pork tapeworm)
• Beef: Taenia saginata (beef tapeworm)
• Freshwater fish: Capillaria philippinensis
• Crabs: Paragonimus westermani
• Snail (kuhol): Echinostoma ilocanum

Question 132

Humans can also acquire parasitic infections if they swallow food or vegetables that have come in contact with contaminated soil and consume them without [?] or washing them with contaminated water.

Answer 132

proper washing

Question 133

is an invertebrate, an arthropod or mollusc, that transmits an infection from one host to another.

Answer 133

vector

Question 134

is a vector which not only assists in the transfer of parasites between hosts but also in which the parasite goes through morphological or physical changes.

Question 135

A certain period has to elapse after the parasite enters the vector, undergoes a developmental process before it becomes infective.

Answer 135

Biological vector

Question 135

A certain period has to elapse after the parasite enters the vector, undergoes a developmental process before it becomes infective.

Answer 135

Biological vector

Question 136

The vector assists in the completion of the life cycle of the parasite.

Answer 136

Biological vector

Question 137

Examples of biological vectors and vector-borne parasites are:
• Mosquito: 
• Dog/cat flea: 
• Sandflies: 
• Reduviid bugs:

Answer 137

• Mosquito: Plasmodium spp.
• Dog/cat flea: Dipylidium caninum
• Sandflies: Leishmania spp.
• Reduviid bugs: Trypanosoma cruzi

Question 138

is a vector which assists in the transfer parasitic form between hosts but is not essential in the life cycle of the parasite.

Answer 138

Mechanical vector

Question 139

Example of mechanical vectors is:

• Housefly:

Answer 139

• Housefly: Amoebiasis

Question 140

is a human infection caused by an organism which occurs naturally in other animals

Answer 140

zoonosis

Question 141

Zoonotic diseases can be caused by

Answer 141

viruses, bacteria, parasites, and fungi

Question 142

For zoonotic diseases that are caused by parasites, they are from a variety of [?].

Answer 142

domestic and wild animals

Question 143

While some are foodborne zoonotic parasites, others are a group of so-called [?] whose infective form is introduced into the environment while already primed for infection and can be transmitted to humans under certain conditions.

Answer 143

“contact” parasites

Question 144

• Canids:

* Felids:

Answer 144

• Canids: Echinococcus granulosus, Toxocara canis

* Felids: Toxoplasma gondii, Toxocara cati

Question 145

People who have a parasitic disease or are carriers of parasites are sources of infection. Persons with [?] are obvious sources of infection.

Answer 145

frank symptomatic infection

Question 146

a person who is harboring a parasite but exhibiting no clinical signs or symptoms, and can transmit parasite to others, are unfortunately very difficult to discover and control.

Answer 146

carrier

Question 147

is where the infected person himself is the source of infection. It is a reinfection by parasites that are already present within the body of the host.

Answer 147

Autoinfection

Question 148

This is due to the ability of parasites to complete the life cycle within a single host, without the involvement of another host. This explains persistent infections in individuals for a long time even without additional exposure. The build-up of parasites within the host causes hyperinfection.

Answer 148

Autoinfection

Question 149

Parasites causing autoinfection are:

Answer 149

• Enterobius vermicularis
• Strongyloides stercoralis
• Capillaria philippinensis
• Cryptosporidium parvum
• Taenia solium
• Hymenolepis nana

Question 150

occurs when the parasite infective stage passes out from the host and re-enters the host. One way by which reinfection occurs is perianal-to mouth via finger transmission.

Answer 150

External autoinfection

Question 151

is when the parasite repeats the life cycle without leaving the host.

Answer 151

Internal autoinfection

Question 152

[?] migrates nocturnally outside the anus and oviposit on the perianal area. The eggs become infective in [?] under optimal conditions. Infection occurs via transferring eggs to the mouth with hands that have scratched the perianal area ([?]) or through exposure to eggs in the e n v i r o n m e n t , o r b y retroinfection,— the migration of newly hatched larvae from the anus back into the intestine ([?]).

Answer 152

Gravid female Enterobius vermicularis
4 to 6 hours
external autoinfection
internal autoinfection

Question 153

is an inanimate object that becomes contaminated with and transmits pathogens to the host.

Answer 153

fomite

Question 154

Example: Eggs from louse-infested clothing or other personal articles also may be sources of infection; body lice may be acquired from sitting on cloth-covered seats in public places, such as theaters or waiting areas.

Answer 154

Fomites

Question 155

is the site or route through which the parasite gains access into the human body.

Answer 155

portal of entry

Question 156

Parasites have a preferred portal of entry that is a prerequisite to their being able to become established within the host, and some to cause disease. The preferred portals of entry for some common parasites are:

Answer 156

1. Gastrointestinal tract
2. Skin and mucous membranes
3. Respiratory tract
4. Genitourinary tract
5. Others

Question 157

This is the most common portal of entry of the parasites.

Answer 157

1. Gastrointestinal tract

Question 158

Parasites gain access to the gastrointestinal tract by way of the

Answer 158

mouth

Question 159

Ingestion of infective stages in contaminated food, water, contaminated fingers or fomites.

Answer 159

1. Gastrointestinal tract

Question 160

1. Gastrointestinal tract: Ingestion

Answer 160

Examples: 
Entamoeba histolytica
 Giardia lamblia
 Ascaris lumbricoides
 Trichuris trichiura
 Taenia spp.

Question 161

Person-to-person orally by kissing or fomites (such as eating utensils).

Answer 161

1. Gastrointestinal tract

Question 162

1. Gastrointestinal tract: Person-to-person orally by kissing or fomites

Answer 162

Examples:
Entamoeba gingivalis
Trichomonas tenax

Question 163

The [?]usually serves as a barrier to infection. However, it is an important portal of entry of some parasites to the blood from which they can spread to other sensitive internal organs.

Answer 163

skin skin

Question 164

By penetration of the unbroken skin by larvae once they make contact with the host.

Answer 164

2. Skin and mucous membranes

Question 165

2. Skin and mucous membranes: By penetration of the unbroken skin by larvae once they make contact with the host.

Answer 165

Examples:
Filariform larvae of hookworms while walking barefoot on the soil
Cercaria of Schistosoma spp. while swimming in water

Question 166

By the aid of vector that transmits infective stage of the parasite when it feeds upon the host

Answer 166

2. Skin and mucous membranes

Question 167

2. Skin and mucous membranes: By the aid of vector

Answer 167

Examples:
Plasmodium spp. (malaria) are injected via the mouth part of female Anopheles mosquito during a blood meal
(inoculative method)

Trypanosoma cruzi (Chagas' disease), during a blood meal of a reduviid bug, are
 released in the bug's feces and enter the host through the bite wound or intact mucosal membranes, such as the conjunctiva 
(contaminative method)

Question 168

[?] eggs deposited in the perianal region of the host can easily contaminate the surrounding environment (underwear and beddings)and may become airborne and be inhaled and swallowed to initiate intestinal infection.

Answer 168

Enterobius vermicularis

Question 169

infect humans by penetrating the nasal mucosa, usually during swimming or sinus irrigation, and migrating to the brain via the olfactory nerves causing primary amebic meningoencephalitis (PAM).

Answer 169

Naegleria fowleri trophozoites

Question 170

is a portal of entry for parasites that are contracted sexually.

Answer 170

genitourinary tract

Question 171

4. Genitourinary tract spp

Answer 171

Example: Trichomonas vaginalis

Question 172

5. Others

Answer 172

• Transplacental

* Transmammary

Question 173

by which the parasite leaves its host is usually but not always the same as the portal of entry; determine how parasites spread in a population.

Answer 173

portal of exit

Question 174

refers to the manner in which transmission takes place.

Answer 174

Mode of transmission

Question 175

Parasites can be transmitted from host to host by four (4) principal modes.

Answer 175

1. Contact transmission
2. Airborne transmission
3. Vehicle transmission
4. Vectorborne transmission

Question 176

This is the spread of the parasite by direct contact, indirect contact, or droplet transmission.

Answer 176

1. Contact transmission

Question 177

also known as person-to-person transmission, is the transmission of a parasite by physical contact between an infected individual and a susceptible host; no intermediate object is involved

Answer 177

a. Direct contact transmission

Question 178

The forms of direct contact transmission are:

Answer 178

• Horizontal transmission

* Vertical transmission

Question 179

refers to the spread of a parasite through a population from infected individual to another. This includes touching, kissing, and sexual intercourse

Answer 179

• Horizontal transmission

Question 180

signifies transmission of the parasite from parent to offspring, e.g., transplacental or transmammary.

Answer 180

• Vertical transmission

Question 181

occurs when the parasite is transmitted from the infected host to the next susceptible host by means of intermediary nonliving object, fomite.

Answer 181

b. Indirect contact transmission

Question 182

is a type of transmission in which parasites are spread in droplets of saliva or mucus that are discharged into the air by coughing, sneezing, laughing, or talking.

Answer 182

c. Droplet transmission

Question 183

Though the route is through the air, this is not regarded as airborne transmission because these particles are large (greater than [?]), travel a short distance (less than [?]) from the source, and quickly settle out of air. Since droplets fall to the ground within a few feet, this type of transmission requires close proximity.

Answer 183

5 µm

1 meter

Question 184

is the transmission of a parasite that is suspended in air contained within droplet nuclei or dust

Answer 184

Airborne transmission

Question 185

are small particles (1-4 µm in diameter) that represent what is left from the evaporation of larger droplet particles. They are small enough to remain suspended in air for prolonged periods and travel 1 meter or more from the source.

Answer 185

Droplet nuclei

Question 186

is the transmission of parasite by a common inanimate reservoir where the parasite can normally be found, such as soil, water, and food, or other media including blood and other body fluids, drugs, and intravenous fluids.

Answer 186

Vehicle transmission

Question 187

are the most important group of vectors that carry parasites from one host to another.

Answer 187

Arthropods

Question 188

Arthropod vectors transmit disease by two general methods:

Answer 188

• Biological transmission

* Mechanical transmission

Question 189

is an active process and is more complex. The arthropod bites an infected person or animal and ingests some of the infected blood. The parasites then reproduce in the vector, and the increase in the number of parasites increases the possibility that they will be transmitted to another host.

Answer 189

• Biological transmission

Question 190

Some parasites reproduce in the gut of the arthropod and can be passed in feces; if the arthropod defecates while biting the host, the parasites enter the bite wound [?], e.g., Trypanosoma cruzi (Chagas’ disease) from reduviid bug.

Answer 190

(contaminative method)

Question 191

Some parasites reproduce in the vector’s gut and migrate to the salivary gland; these are directly injected into a bite [?], e.g., Plasmodium spp. (malaria) from female Anopheles mosquito.

Answer 191

(inoculative method)

Question 192

the passive transport of the pathogens on the insect’s feet or other body parts . If the insect makes contact with a host’s food, pathogens can be transferred to the food and later swallowed by the host. Houseflies, for instance, can transfer the amoebae from the feces of infected people to food.

Answer 192

• Mechanical transmission

Question 193

A knowledge of the life cycle of parasites and their methods of infecting the host is of paramount importance in determining methods of prevention and formulating effective [?]. It helps to ascertain the weakest or most vulnerable point at which the parasite can be attacked.

Answer 193

control measures

Question 194

1. A nonpathogenic parasite.

Answer 194

COMMENSAL

Question 195

2. Has a direct life cycle.

Answer 195

MONOXENOUS

Question 196

3. Passes through the GIT without infecting the host.

Answer 196

SPURIOUS

Question 197

4. Capable of independent or a parasitic existence

Answer 197

FACULTATIVE

Question 198

5. Attached to the outer surfaces of its host.

Answer 198

ECTOPARASITE

Question 199

6. Inhabits a cavity of the host’s body.

Answer 199

COELOZOIC

Question 200

7. Soil-transmitted helminth.

Answer 200

GEOHELMINTH

Question 201

8. Actively motile and feeding form of protozoa.

Answer 201

TROPHOZOITE

Question 202

9. Stage of helminth harbored by intermediate host.

Answer 202

LARVA

Question 203

10.Transmitted by blood-sucking arthropods.

Answer 203

VERTOR BORNE