Chapter 4 SOURCES OF EXPOSURE, EPIDEMIOLOGY, MODE AND ROUTE OF TRANSMISSION OF PARASITIC INFECTION

Question 1

____________ refers to the invasion and multiplication of microorganisms such as bacteria, viruses, and parasites that are not normally present within the body. An ____________ may cause no symptoms and be subclinical, or it may cause symptoms and be clinically apparent.

Answer 1

infection

Question 2

SOURCES OF INFECTION

Vectors
A vector is an ____, usually an ____ that transmits an infection from man to man or from other animals to man, e.g. female Anopheles is the vector of malarial parasite.

Answer 2

agent
arthropod

Question 3

SOURCES OF INFECTION

____ refers to a vector, which not only assists in the transfer of parasites but the parasites undergo development or multiplication in their body as well.
* They are also called as true vectors.

Answer 3

Biological vectors

Question 4

SOURCES OF INFECTION

Example of true vectors are:

Answer 4

• Mosquito: Malaria, filariasis
• Sandflies: Kala-azar
• Tsetse flies: Sleeping sickness
• Reduviicl bugs: Chagas disease
• Ticks: Babesiosis.

Question 5

SOURCES OF INFECTION

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

Answer 5

Mechanical vectors

Question 6

SOURCES OF INFECTION

Example of mechanical vectors is:

Answer 6

• Housefly: Amebiasis

Question 7

SOURCES OF INFECTION

• In biological vectors, a certain period has to elapse after the parasite enters the vector, before it becomes infective.
• This is necessary because the vector can transmit the infection only after the parasite multiplies to a certain level or undergoes a developmental process in its body.
• This interval between the entry of the parasite into the vector and the time it takes to become capable of transmitting the infection is called the _____

Answer 7

extrinsic incubation period

Question 8

SOURCES OF INFECTION

• A person who is infected with parasite without any clinical or subclinical disease
• He can transmit parasite to others.

Answer 8

Carrier

Question 9

SOURCES OF INFECTION

CONTAMINATED SOIL

Answer 9

embyronated eggs roundworm, whipworm (thru ingestion)
hookworm (thru penetration)

Question 10

SOURCES OF INFECTION

CONTAMINATED WATER

Answer 10

cyst of ameba and Giardia (thru ingestion)
cyclops containing guinea worm larva (thru swallowing)
cercariae of schistosomes (thru penetration)
Naegleria (thru nasopharynx)

Question 11

SOURCES OF INFECTION

FOOD

Answer 11

• amebic cysts,
• Toxoplasma oocysts,
• Echinococcus eggs
• cysticercus cellulosae
• Taenia solium larval stage

Question 12

SOURCES OF INFECTION

ANIMAL

Answer 12

• cystic echinococcosis from dogs
• toxoplasmosis from cats

Question 13

SOURCES OF INFECTION

VECTOR

Answer 13

female Anopheles

Question 14

SOURCES OF INFECTION

CARRIER

Answer 14

• all anthroponotic infections
• vertical transmission of congenital infections

Question 15

SOURCES OF INFECTION

SELF (AUTO-INFECTION)

Answer 15

• pinworm internal re-infection
• Stronglyloides
• S. stercolaris
• E. vermicularis
• T. solium

Question 16

MODES OF INFECTION

enumerate the 7

Answer 16

1. oral/ feco-oral
2. bite of vectors
3. blood transfusion
4. vertical transmission
5. auto-infection
6. sexual contact
7. penetration of the skin and mucuous membranes

Question 17

The parasite can cause damage to humans in various ways:

give 8

Answer 17

1. mechanical trauma
2. inflammatory reactions
3. allergic manifestations
4. secondary bacterial infection
5. toxins
6. space occupying lesions
7. neoplasia
8. enzyme production and lytic necrosis