Parasite Transmission and Vector Classification Quiz

Scientific Names and Parasites

• A scientific name consists of a generic name with an initial capital letter and a specific name with an initial small letter.
• Parasites that injure the host are called pathogens, and the development of the damage is called pathogenesis.

Factors Affecting Pathogenesis

• The degree of injury depends on several factors:
  • Potential virulence of the agent (intrinsic pathogenecity)
  • Amount of inoculum and rapidity of multiplication
  • Site of inoculation
  • Exposure (single or repeated)
  • Resistance or tolerance of the host to a particular strain of agent
  • General resistance of the host
  • Type of damage caused by the agent (mechanical, lytic, toxic, or allergic)

Epidemiology

• Incidence is the rate or frequency of new infections in a designated area.
• Endemic diseases are maintained at a stable rate of prevalence within a population.
• Hyper endemic diseases have a high prevalence.
• Sporadic diseases appear irregularly in scattered individuals.
• Epidemic diseases have a high prevalence in unusual transmission.
• These terms are specific to humans, while similar terms for animals are enzootic, hyper enzootic, epizootic, and sporadic.

Biological and Mechanical Vectors

• A biological vector is essential for the parasite's life cycle, e.g., Anopheles female transmitting Plasmodium.
• A mechanical vector is not essential for the parasite's life cycle, e.g., house fly transmitting E. histolytica.

Zoonosis and Classification

• Zoonosis is a disease transmitted from animals to humans, either incidentally or commonly.
• Classification of animal parasites and vectors includes:
  • Coprozoic or spurious parasites (eggs or parasites that are not in their normal habitat)
  • Wandering or aberrant parasites (parasites that reach a place where they cannot live)
  • Pseudoparasites (objects that resemble parasites or eggs but are not parasites)

Major Groups in Medical Parasitology

• Four groups are of major importance in medical parasitology:
  • Protozoa
  • Helminths
  • Molluscs
  • Arthropods

Zoological Nomenclature

• Phylum, subphylum, and other larger divisions are used to classify organisms.
• Classes, orders, families, genus, and species are used to classify organisms in lesser divisions.
• All names must be of Greek or Latin origin.

Genus and Species

• A genus is a group of closely related species.
• A species is a population with the same genetic characters, capable of continued reproduction, and incapable of interbreeding with other species.

Types of Parasites

• Obligate parasites are entirely dependent on their hosts and cannot live outside the host.
• Facultative parasites are capable of living either free or in or on a host.
• Parasites can be classified by the duration of their association with their hosts:
  • Temporary parasites visit a host for a short period.
  • Permanent parasites lead a parasitic life all through their life.

Hosts

• The human or organism that harbors the parasite is called the host.
• Definitive host: the organism in which the adult or final stage of the parasite develops or where sexual reproduction occurs.
• Intermediate host: the organism that harbors the larval stage of the parasite.
• Paratenic host: a host in which the parasite is transported and neither gains nor loses infectivity for its definitive host.
• Reservoir host: an animal species on which the parasite depends for its survival in nature and acts as a source of infection for other hosts.
• Vector: a transmitter of parasites from host to host, or an agent of transmission.