C4: Sources of Exposure, Epidemiology, Mode and Route of Transmission of Parasitic Infection

Question 1

Name the SOURCES OF INFECTION

Answer 1

Contaminated soil and water
Food
Animal
Vectors

Question 2

The infection which is transmitted from infected animals to humans is called as
.

Answer 2

zoonoses

Question 3

A ________is an agent, usually an arthropod 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 3

vector

Question 4

The term ______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 ______.

Answer 4

biological vector ; true vectors

Question 5

The term ________ 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 vector

Question 6

This interval between the entry of the parasite into the vector and the lime it takes to become
capable of transmitting the infection is called the

Answer 6

extrinsic incubation period.

Question 7

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

Answer 7

carrier

Question 7

• It is the most common mode of transmission of the parasites. Infection is transmitted
  orally by ingestion of food, water or vegetables contaminated with feces containing the
  infective stages of the parasite. (e.g., cysts of E. histolytica, and ova of Ascaris
  lumbricoides).

Answer 7

Oral or feco-oral route:

Question 8

:
- Infection is transmitted by the penetration of the larval forms of the parasite through
unbroken skin (e.g., filariform larva of Strongyloides stercoralis and hookworm can
penetrate through the skin of an individual walking barefooted over fecally
contaminated soil), or by introduction of the parasites through bloodsucking insect
vectors. (e.g., Plasmodium species, Leishmania species and Wuchereria bancrofti)

Answer 8

Penetration of the skin and mucous membranes

Question 9

• Finger-to-mouth transmission

Answer 9

Self(autoinfection):

Question 10

is the most frequent parasite to be transmitted by sexual contact.

Answer 10

Trichomonas vaginalis

Question 11

• Mother to fetus transmission is important for few parasitic infections like Toxoplasma
  gondii , Plasmodium spp. and Trypanosoma cruzi.

Answer 11

Vertical transmission:

Question 11

Many parasitic diseases are transmitted by insect bite such as: malaria (female
anopheles mosquito), filariasis (Culex), leishmaniasis (sandfly), Chagas’ disease
(reduviid bug) and African sleeping sickness (tsetse fly)

Answer 11

Bite of vectors

Question 11

• Certain parasites like Plasmodium species, Babesia species, Toxoplasma species,
  Leishmania species and Trypanosoma species can be transmitted through transfusion
  of blood or blood products

Answer 11

Blood transfusion:

Question 12

Example of true vectors are:
* Mosquito: ______, ______
* Sandflies: _____
* Tsetse flies: _______
* Reduviicl bugs: ______
* Ticks: ______.

Answer 12

Example of true vectors are:
* Mosquito: Malaria, filariasis
* Sandflies: Kala-azar
* Tsetse flies: Sleeping sickness
* Reduviicl bugs: Chagas disease
* Ticks: Babesiosis.

Question 13

Example of mechanical vectors is:
* Housefly:

Answer 13

Amebiasis

Question 14

Enumerate how the parasites can cause damage to humans in various ways.

Answer 14

Mechanical trauma
Space occupying lesions
Inflammatory reactions
Enzyme production and lytic necrosis
Toxins
Allergic manifestations
Neoplasia
Secondary bacterial infections

Question 15

• Certain parasites produce characteristic cystic lesion that may compress the surrounding tissues or organs, e.g., hydatid cysts and neurocysticercosis

Answer 15

Space occupying lesions:

Question 16

• Most of the parasites induce cellular proliferation and infiltration at the site of their multiplication, e.g., _______provokes inflammation of the large intestine leading to the formation of ____. Adult worm of W. bancrofti causes mechanical blockage and chronic inflammation of the lymphatics and lymph vessels. Trematode eggs can induce inflammatory changes (granuloma formation) surrounding the area of egg deposition

Answer 16

Inflammatory reactions; E. histolytica; amoebic granuloma

Question 17

• Obligate intracellular parasites of man (Plasmodium, Leishmania and Trypanosoma), produce several enzymes, which cause digestion and necrosis of host cells. E. histolytica produces various enzymes like cysteine proteinases, hydrolytic enzymes and amoebic pore forming protein that lead to destruction of the target tissue

Answer 17

Enzyme production and lytic necrosis:

Question 18

:
- Some of the parasites produce toxins, which may be responsible for pathogenesis of the disease, e.g., E. histolytica. However, in contrast to bacterial toxin, parasitic toxins have minimal role in pathogenesis

Answer 18

Toxins

Question 19

• Many metabolic and excretory products of the parasites get absorbed in the circulation and produce a variety of allergic manifestations in the sensitized hosts

Answer 19

Allergic manifestations:

Question 20

Examples include schistosomes causing cercarial dermatitis, rupture of hydatid cyst producing anaphy lactic reactions and occult filariasis (tropical pulmonary eosinophilia)

Answer 20

Allergic manifestations:

Question 21

• Some of the parasitic infections can contribute to the development of ____(e.g., S. haematobium causes bladder carcinoma, Clonorchis and Opisthorchis cause cholangiocarcinoma)

Answer 21

neoplasia

Question 22

• Seen in some helminthic diseases (schistosomiasis and strongyloidiasis).

Answer 22

Secondary bacterial infections:

Question 23

Ingestion of raw or undercooked meat harboring infeclive larvae (measly pork containing ________, the larval stage of Taenia solium)

Answer 23

cysticercus cellulosae

Question 24

______ causing cercarial dermatitis, rupture of hydatid cyst producing _________ and occult fi lariasis (tropical pulmonary eosinophilia)

Answer 24

schistosomes; anaphylactic reactions