Potential Application of Nanoparticles as Antipathogens - Advanced Materials for Agriculture, Food and Environmental Safety - page 333

Polyomavirus, Rhabdoviridae and Togaviridae. Viruses typically range
between 20-300 nanometers in length.
Bacterial: Although the vast majority of bacteria are harmless or ben-
ei cial, a few pathogenic bacteria can cause infectious diseases. Bacteria
can ot en be killed by antibiotics because the outside of the cell wall is
destroyed, expelling the DNA out of the body of the pathogen; therefore
the pathogen is incapable of producing proteins and dies. h ey typically
range between 1 and 5 micrometers in length.
Fungal: Fungi comprises eukaryotic kingdom of microbes that are
usually saprophytes (consume dead organisms) but can cause diseases in
humans, animals and plants. Fungi are the most common cause of diseases
in crops and other plants. h e typical fungal spore size is 1-40 micrometer
in length.
Prionic: According to the prion theory, prions are infectious pathogens
that do not contain nucleic acids. h ese abnormally folded proteins are
characteristically found in some diseases such as scrapie, bovine spon-
giform encephalopathy (mad cow disease) and Creutzfeldt-Jakob dis-
ease. Although prions fail to meet the requirements laid out by Koch's
postulates, the hypothesis of prions as a new class of pathogen led Stanley
B. Prusiner to receive the Nobel Prize in Physiology or Medicine in 1997.
Animal pathogens: Animal pathogens are disease-causing agents of
wild and domestic animal species, at times including humans.
12.1.2 Virulence
Virulence (the tendency of a pathogen to cause damage to a host's i tness)
evolves when that pathogen can spread from a diseased host, despite that
host being much debilitated. Horizontal transmission occurs between
hosts of the same species, in contrast to vertical transmission, which tends
to evolve symbiosis (at er a period of high morbidity and mortality in the
population) by linking the pathogen's evolutionary success to the evolu-
tionary success of the host organism. Evolutionary medicine has found that
under horizontal transmission, the host population might never develop
tolerance to the pathogen.
12.1.3 Transmission
Transmission of pathogens occurs through many dif erent routes, includ-
ing airborne, direct or indirect contact, sexual contact, through blood,
breast milk, or other body l uids, and through the fecal-oral route.