Introduction lecture

Question 1

What is a parasite?

Answer 1

organism that lives on or in a host organism and gets its food from or at the expense of its host

Question 2

What is parasitism?

Answer 2

• is a form of symbiosis, in which the parasite, usually the smaller
• symbiont, is metabolically dependent on the host.

Question 3

What is the relationship between host and parasite?

Answer 3

One symbiont (host) is harmed, while the other 
symbiont (parasite) benefits.

Question 4

What are the characteristics of a parasite?

Answer 4

• Depends on the host for survival
  • Has adverse effects on the host
  • Has greater fecundity than host
  • Is usually smaller than its host
  • Doesn’t want to kill its host
  host dies-parasite dies
  • In the case of Macroparasites
  (Helminths) – Are over-dispersed among the host population

Question 5

How can a parasite harm a host?

Answer 5

• Cause clinical/sub-clinical diseases
• Trauma
• Nutrient Robbing
• Toxin production
• Inflammatory responses/ Interaction with host immune

Question 6

Why do we study parasites in veterinary medicine?

Answer 6

• Impact animal health/welfare, Economic loss
• Negatively impact the human-animal bond
• Pose a challenge in wildlife conservation
• Pose a risk to human health. Parasitic zoonoses

Question 7

What is a direct life cycle?

Answer 7

Free living —> Host, no intermediate hosts

Question 8

What is an indirect lifecycle?

Answer 8

Egg/Larvae in another host(s)–> host. Intermediate hosts present.

Question 9

What is the lifecycle shown in this picture?

Answer 9

Direct lifecycle

Question 10

What kind of lifecycle is shown in this picture?

Answer 10

Indirect

Question 11

What is a microparasite?

Answer 11

E.g. Protozoa, Viruses (Malaria, Giardia, Toxoplasma)

• Tiny, Unicellular, microscopic
• Multiply within hosts
• Short life cycles

Question 12

What are macroparasites?

Answer 12

E.g. Roundworms, Tapeworms, Ticks, Fleas

Large, Multicellular, adult macroscopic

Reproduce in definative hosts

Generally longer life cycles

Question 13

What are endoparasites?

Answer 13

• Adults inside body of host
  eg: Nematodes, tapeworms, giardia

Question 14

What are ectoparasites?

Answer 14

Parasites that live on the body of the host.

E.g. Ticks, mites, bugs, flies, mosquitos

Question 15

What are facultative parasites?

Answer 15

• Both parasitic and non parasitic lifestyles
• opportunistic parasite, can complete lifecycle without hosts.
  eg: strongyloides spp

Question 16

What is an Obligatory parasite?

Answer 16

Only parasitic stage- no free living environmental stage

eg: trichinells spp. Plasmodium spp.

Question 17

What are Spurious parasites?

Answer 17

Incidental finding. Parasite is found in unusual host. Usually resulted from predation or accidental ingestion/ contamination.

Eggs/ larvae do not develop in unusual host

Question 18

What is a pseudoparsite?

Answer 18

• object or organism that resembles or is mistaken for a parasite.

Question 19

What are the three major groups of parasites?

Answer 19

• Protozoa
• Helminths
• Arthropods

Question 20

How do protazoa reproduce and are they single celled or multicellular?

Answer 20

Single celled - microscopic • Reproduce mostly asexually -
Multiply and increase in number • Some sexually – fusion of
gametes
e.g. Giardia, Cryptosporidium Toxoplasma, E. coli

Question 21

What is some important information on Helminths?

Answer 21

Multicellular – Adults easily visible • Produce offspring • Well developed organs, systems • Prepatent period and patency is
long
e.g: Hookworm, Tapeworms, Flukes

Question 22

What is some important information about arthropods?

Answer 22

• Multicellular – Visible
• Segmented bodies, jointed limbs

• Parasites themselves or vectors
of other microbes

• Insects – 6 legs

• Arachnids 8 legs (adult)
e.g. Flies, ticks, mites

Question 23

What is definitive host?

Answer 23

Main host. Supports sexual reproduction of the parasite. Parasite reaches
sexual maturity. E.g. Dogs for Toxocara canis

Question 24

What is an intermediate host?

Answer 24

Supports the parasite’s development and asexual reproduction
(multiplication)—E.g. Slugs and snails for some lungworms.

Question 25

What is a paratenic host?

Answer 25

Development, multiplication does not occur in this host. Help in
maintaining the lifecycle but not necessary. E.g., Rodents for some nematodes

Question 26

What is a transport host?

Answer 26

Carrier of the parasite from one host to another. No development or
multiplication. E.g., Houseflies for some parasites. Aka mechanical hosts.

Question 27

What is an aberrant/ unusual host?

Answer 27

Non-natural host. The parasite may cause pathology in aberrant hosts.
E.g., Dogs are aberrant intermediate hosts for Racoon roundworms.

Question 28

What is a vector?

Answer 28

• Carrier of an infectious agent between organisms of a different species. Can be
  intermediate hosts or transport hosts. Usually used in case of human infections. E.g., mosquitoes
  for heartworm, malaria.

Question 29

What is a reservoir host?

Answer 29

Maintains the infection without being harmed—e.g., White-tailed deer for
brainworm.

Question 30

What are the routes of transmission?

Answer 30

• Fecal-oral- most intestinal parasites (Giardia, hookworms)
• Skin penetration ( per-cutaneous)- bot fly
• Vector transmission/ innoculation- heartworm via mosquitos
• Direct contact : ectoparasites
• Sexual transmission- Tritichomonas foetus
• Vertical transmission: mother to offspring
  
  • Placental/ Prenatal (toxocara canis)
  • Through milk- Transmammary/ Lactogenic transmission (eg: ancyclostoma spp.)
• Iatrogenic Transmission: Blood transfusion through contaminated surgical instruments, needles. (e.g. Blood protozoa, bacteria, virus)

Question 31

How do you diagnose parasites?

Answer 31

• Fecal test
  
  • Float, Sedimentation, Qualatative, Quantitative
• Urinalysis- ex dioctophyme
• Examination of blood
  
  • Blood protazoans, arthropods, and some helminths
  • Direct smear, stained smear, knotts test (HW disease)
• Exam of tissue
  
  • Ex: Trichinella
  • Tissue digestion/ tissue squash
• Exam of hair/ skin
  
  • Primarily ectoparasites. Ex: fleas mites, lice
  • Skinscrape, KOH digestion of scrape, direct observation.
• Necropsy
  
  • Fatal cases
  • Adult parasites/ stages, characteristic lesions formed by parasites.
  • Histopathology
• PCR/Genetic Markers
  
  • Species level ID
  • Primers/ probes used to amplify species specific genetic markers
  • can be done from extracted egg/larvae/ adult.
• Immunological Tests: Elisa, IFA, CFT, ect.
  
  • Serological tests- tests for antibodies against parasites
  • In house testing
  • Commercial tests.

Question 32

What are the important methods of parasite management or control?

Answer 32

• Kill/Neutralize the parasites in the definitive hosts – Antiparasitic drugs
• Prevent or reduce the production of offspring in the host
• Immunization - Vaccines
• Optimize host health to resist transmission
• Kill/clear free-living stages in the environment
• Prevent contact with/consumption of intermediate/paratenic hosts
• Kill/neutralize intermediate/paratenic hosts

BREAK THE LIFECYCLE

Question 33

What is a serious emerging issue in parasitology?

Answer 33

Drug resistance

• Judicial use of paraciticides is critical