Parasite Basics

Question 1

Why are parasites important

Answer 1

• largest financial impact on farm productivity of all endemic diseases
• Biodiversity - balance of nature

Question 2

5 Unexpected ways parasites can be beneficial

Answer 2

• Magot therapy instead of amputation
• allergy control
• immune system stimulation/ regulation
• DNA profiling
• Research inc. population study

Question 3

Define Endoparasite

Answer 3

lives inside the internal organs of the host

Question 4

Define Ectoparasite

Answer 4

lives on the external parts of the host

Question 5

Define obligatory

Answer 5

• traditional parasite definition
• remove host and the parasite dies

Question 6

Define facultative

Answer 6

• can live free in the environment
• survive outside of host and can cause diseases when ingested or in contact with host
• can skin parasitic stage for several generations

Question 7

Define definitive host

Answer 7

• harbors the adult parasite and where the parasite produces sexually (reaches mature form)

Question 8

Define intermediate host

Answer 8

• harbors the larval stage or asexual forms of the parasite
• growing and development / sexual maturity not yet reached

Question 9

Define Paratenic host

Answer 9

• not needed for the development of the parasite but serves to maintain the lifecycle
• serves until appropriate definitive host is reached

Question 10

Define Direct Lifecycle

Answer 10

• parasite is transmitted directly from one host to the next
• involve single host where parasite spends most of its life and where it reproduces
• complex parasites
• less virulent
• no intermediate host

Question 11

Define indirect lifecycle

Answer 11

• parasite require numerous host organisms to complete their lifecycle
• complex parasites
• great virulent potential

Question 12

Define migratory lifecycle

Answer 12

Migration from one tissue to another once inside the host organism

Question 13

Define non-migratory lifecycle

Answer 13

Remains in same body tissue/ system once inside host

Question 14

6 routes of infection

Answer 14

1. Oral ingestion
2. Respiratory inhalation
3. Skin (bites)
4. Sexually
5. Transplacental
6. Trans-mammary

Question 15

Define infective stage

Answer 15

parasite is capable of entering its host and continue its development

Question 16

Define free living stage

Answer 16

progeny transmitted from one host to anither

Question 17

Define prepatent period

Answer 17

time elapsing between parasitic infection and the demonstration of the parasite in the host
- determined by the recovery of an infective form (oocysts or eggs) from blood or feces

Question 18

Define asexual reproduction

Answer 18

• offspring produced by a single parent through spitting or budding of a single cell or an entire organism
• new individuals = genetically and physically identical
• no fusion of 2 haploid gametes

Question 19

Define schyzogony (2 stages)

Answer 19

• replicative process in 2 stages
  1. parasite undergoes multiple rounds of nuclear division but no cytoplasmic division
  2. budding or segmentation to form progeny

Question 20

Define merozoites

Answer 20

• product/ progeny of schyzogony
• released into circulatory system following the rupture of the host hepatocyte

Question 21

Define hermaphroditism

Answer 21

male and female gonads in single individual

Question 22

3 things required for disease

Answer 22

1. Susceptible host
2. Pathogen
3. Conductive environment

Question 23

7 Host factors affecting parasitism

Answer 23

1. Age
2. exposure
3. quantum of infection
4. genetics (resistance & resilience)
5. periods of stress
6. pregnancy/ lactation (can relax immunity)
7. management factors (e.g. stocking rate)

Question 24

7 parasite factors affecting parasitism

Answer 24

1. Lifecycle
2. climate (ideal = warm and moist)
3. Survival of free-living stages (warm to hatch, cool to last)
4. parasite fecundity (greater egg production = faster build up)
5. Virulence
6. availability of IH or rectors
7. impacts on host behavior

Question 25

13 problems caused by parasites

Answer 25

1. Necrosis
2. produce toxins
3. dodge and damage immune system
4. Mechanical blockage
5. Hemorrhage
6. Space occupying
7. thrombus forming
8. Prevent nutrient absorption
9. fluid leakage
10. digest tissue
11. irritation
12. tissue invasion and perforation
13. allergy and inflammation

Question 26

5 reasons right diagnostic is so important

Answer 26

1. Right treatment
2. Epidemiological studies
3. control
4. prevention
5. drug resistance

Question 27

2 aims of a diagnostic test

Answer 27

1. detect cute infection
2. Analyse the hosts immune status

Question 28

Sensitivity equation

Answer 28

TP / TP + FN

Question 29

specificity equation

Answer 29

TN / TN + FP

Question 30

sensitivity define

Answer 30

ability of a test to correctly identify infected hosts

Question 31

specificity

Answer 31

ability of a test to correctly identify uninfected hosts

Question 32

prevalence

Answer 32

percentage of animals in a population with the parasite

Question 33

5 considerations of diagnostic technique choice

Answer 33

1. sensitivity
2. specificity
3. cost
4. reproducibility
5. time

Question 34

Extracellular host-parasite interaction

Answer 34

• Live external to cells
• Antigen masking
• e.g. intestinal tract and blood

Question 35

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