Introduction lecture Flashcards
What is a parasite?
organism that lives on or in a host organism and gets its food from or at the expense of its host
What is parasitism?
- is a form of symbiosis, in which the parasite, usually the smaller
- symbiont, is metabolically dependent on the host.
What is the relationship between host and parasite?
One symbiont (host) is harmed, while the other symbiont (parasite) benefits.
What are the characteristics of a parasite?
- 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
How can a parasite harm a host?
- Cause clinical/sub-clinical diseases
- Trauma
- Nutrient Robbing
- Toxin production
- Inflammatory responses/ Interaction with host immune
Why do we study parasites in veterinary medicine?
- 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
What is a direct life cycle?
Free living —> Host, no intermediate hosts
What is an indirect lifecycle?
Egg/Larvae in another host(s)–> host. Intermediate hosts present.
What is the lifecycle shown in this picture?
Direct lifecycle
What kind of lifecycle is shown in this picture?
Indirect
What is a microparasite?
E.g. Protozoa, Viruses (Malaria, Giardia, Toxoplasma)
- Tiny, Unicellular, microscopic
- Multiply within hosts
- Short life cycles
What are macroparasites?
E.g. Roundworms, Tapeworms, Ticks, Fleas
Large, Multicellular, adult macroscopic
Reproduce in definative hosts
Generally longer life cycles
What are endoparasites?
- Adults inside body of host
eg: Nematodes, tapeworms, giardia
What are ectoparasites?
Parasites that live on the body of the host.
E.g. Ticks, mites, bugs, flies, mosquitos
What are facultative parasites?
- Both parasitic and non parasitic lifestyles
- opportunistic parasite, can complete lifecycle without hosts.
eg: strongyloides spp
What is an Obligatory parasite?
Only parasitic stage- no free living environmental stage
eg: trichinells spp. Plasmodium spp.
What are Spurious parasites?
Incidental finding. Parasite is found in unusual host. Usually resulted from predation or accidental ingestion/ contamination.
Eggs/ larvae do not develop in unusual host
What is a pseudoparsite?
- object or organism that resembles or is mistaken for a parasite.
What are the three major groups of parasites?
- Protozoa
- Helminths
- Arthropods
How do protazoa reproduce and are they single celled or multicellular?
Single celled - microscopic • Reproduce mostly asexually -
Multiply and increase in number • Some sexually – fusion of
gametes
e.g. Giardia, Cryptosporidium Toxoplasma, E. coli
What is some important information on Helminths?
Multicellular – Adults easily visible • Produce offspring • Well developed organs, systems • Prepatent period and patency is
long
e.g: Hookworm, Tapeworms, Flukes
What is some important information about arthropods?
- 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
What is definitive host?
Main host. Supports sexual reproduction of the parasite. Parasite reaches
sexual maturity. E.g. Dogs for Toxocara canis
What is an intermediate host?
Supports the parasite’s development and asexual reproduction
(multiplication)—E.g. Slugs and snails for some lungworms.
What is a paratenic host?
Development, multiplication does not occur in this host. Help in
maintaining the lifecycle but not necessary. E.g., Rodents for some nematodes
What is a transport host?
Carrier of the parasite from one host to another. No development or
multiplication. E.g., Houseflies for some parasites. Aka mechanical hosts.
What is an aberrant/ unusual host?
Non-natural host. The parasite may cause pathology in aberrant hosts.
E.g., Dogs are aberrant intermediate hosts for Racoon roundworms.
What is a vector?
- 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.
What is a reservoir host?
Maintains the infection without being harmed—e.g., White-tailed deer for
brainworm.
What are the routes of transmission?
- 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)
How do you diagnose parasites?
- 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.
What are the important methods of parasite management or control?
- 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
What is a serious emerging issue in parasitology?
Drug resistance
- Judicial use of paraciticides is critical
