James R. Flowers, PhD(Office hours by appointment)
http://parasitology.cvm.ncsu.edu/
VMP 920Infection & Immunity II
Veterinary Parasitology Section
Studies in Infectious Diseases
Microbiology Virology Bacteriology Mycology
Parasitology Medical & Veterinary Protozoology Helminthology Medical & Veterinary Entomology
Immunology
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.
Parasitism
Host Specificity The degree to which a parasite
species infects a single host species
High v/s Low
Dirofilaria immitisEndoparasite with relatively high host specificity for canids
Endoparasite (permanent)
Ectoparasite (intermittent)
High Host specificity Low Host specificity
Dirofilaria immitis
Culex spp.Ectoparasite with Low Host Specificity
Culex spp.
Endoparasite (permanent)
Ectoparasite (intermittent)
High Host specificity Low Host specificity
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.
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.
Parascaris equorumHorse – Definitive Host
Direct Life Cycle
Definitive Host Intermediate
Host Accidental Host Paratenic Host Reservoir Host
Direct Life Cycle Indirect Life
Cycle
Canids – Definitive Host(wolf / fox) - Reservior hostsSnail – 1st Intermediate hostFish – 2nd Intermediate hostIndirect Life Cycle
Definitive Host Intermediate
Host Accidental Host Paratenic Host Reservoir Host
Direct Life Cycle Indirect Life
Cycle
• 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
Important Parasitological Concepts
A. The dog showed no adverse symptoms to the 2 female
Dirofilaria immitis in its right ventricle.
Infection, Disease, Infectious ?
Infectio
n 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
Infection
D. After using the bathroom, she was horrified to see that she had passed several active proglottids of the beef tapeworm, Taenia saginata.
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
General Groups of Parasites