1. VMP 920 Infection & Immunity II
Veterinary Parasitology Section
James R. Flowers, PhD
(Office hours by appointment)

2. Studies in Infectious Diseases
Microbiology
Virology
Bacteriology
Mycology
Parasitology
Medical & Veterinary Protozoology
Helminthology
Medical & Veterinary Entomology
Immunology

4. Parasitology
Study of Parasitism

5. Parasitism
Intimate relationship between two heterospecific organisms, in which the parasite, usually the smaller symbiont, is metabolically dependent on the host.
One symbiont (host) is harmed, while the other symbiont (parasite) benefits.

6. Parasitism Host Specificity High v/s Low
The degree to which a parasite species infects a single host species
High v/s Low

7. Endoparasite with relatively high host specificity for canids
Dirofilaria immitis
Endoparasite (permanent)
Ectoparasite (intermittent)
High Host specificity
Low Host specificity
Dirofilaria immitis
Endoparasite with relatively high host specificity for canids

8. Ectoparasite with Low Host Specificity
Culex spp.
Endoparasite (permanent)
Ectoparasite (intermittent)
High Host specificity
Low Host specificity
Culex spp.
Ectoparasite with Low Host Specificity

9. Type of Hosts
Definitive Host Host in which parasite reaches sexual maturity
Intermediate Host (vector) Host in which the parasite is metabolically dependent to complete its life cycle
Accidental Host A host that the parasite does not normally infect, may or may not complete development. (Maybe a dead-end host)
Paratenic host A “transport” host, but the parasite does not require it to complete its life cycle.
Reservoir Host An animal host that maintains a parasite population and has the potential to transmit to a human or domestic animal.

10. Type of Life Cycles
Direct Life Cycle Parasite does Not require an intermediate host to complete its life cycle.
Indirect Life Cycle Parasite requires an intermediate host to complete its life cycle.

11. Horse – Definitive Host
Intermediate Host
Accidental Host
Paratenic Host
Reservoir Host
Direct Life Cycle
Indirect Life Cycle
Parascaris equorum
Horse – Definitive Host
Direct Life Cycle

12. Canids – Definitive Host Snail – 1st Intermediate host
Accidental Host
Paratenic Host
Reservoir Host
Direct Life Cycle
Indirect Life Cycle
Canids – Definitive Host
(wolf / fox) - Reservior hosts
Snail – 1st Intermediate host
Fish – 2nd Intermediate host
Indirect Life Cycle

13. Important Parasitological Concepts
Infection = presence of an agent that has the ability to cause disease
Disease = the occurrence of dysfunction
Infectious = capable of causing infection
Infection ≠ Infectious ≠ Disease

14. Infection, Disease, Infectious ?
A. The dog showed no adverse symptoms to the 2 female Dirofilaria immitis in its right ventricle.
Infection
B. 1,000 juvenile Haemonchus contortus were causing severe anemia in the lamb.
Infection + Disease
C. Cats suffering from large bowel diarrhea due to Tritrichomonas foetus pass active trophs in their stool.
Infection + Disease + Infectious
D. After using the bathroom, she was horrified to see that she had passed several active proglottids of the beef tapeworm, Taenia saginata.
Infection

15. General Groups of Parasites
Important concepts to associate with parasitic life cycles, infections, pathogenesis, and dz control.
Macroparasites
Large parasites (Adult Tapeworms, Adult Trematodes, most Nematodes, Acanthocephalans, Arthropods)
Individual organisms do NOT Multiply in or on the host.
Dose-dependent
Microparasites
Small parasites (Protozoa, [bacteria, viruses])
Individual organisms do Multiply in the host.
Generally not dose-dependent

16. Dose Dependent

17. & other extracellular protozoa
Giardia sp.
& other extracellular protozoa
Replication
(binary fission)