Biomedical Engineering Reference
In-Depth Information
virus, Wuchereria bancrofti , and Brugia malayi . Obversely, one disease organism can
be spread by more than one vector. For example, orbiviruses are spread by mosquitoes,
midges, gnats, sandflies, and ticks.
Virulence factor These are molecules that enhance the ability of an infectious organism
to survive in its host. Many of the best-studied virulence factors are produced by bac-
teria, and because virulence factors always work to the detriment of the host, the terms
“virulence factor” and “bacterial toxin” are mistakenly used interchangeably. You will
find it useful to separate these two concepts because virulence factors and bacterial
toxins have very different functions. Toxins work by damaging or killing host cells.
Virulence factors work by making it easier for organisms to invade, grow, and persist
within the host. Virulence is attained by helping the infectious organism obtain nutri-
tion from host cells, by evading or suppressing the host immune response, by enhanc-
ing the ability of the organism to adhere to host cells, or by enabling the organisms to
enter host cells or to invade through host tissues. See Toxin.
Zoonosis An infectious disease of humans that is acquired from a non-human animal res-
ervoir. The method of infection (e.g. vector) does not determine whether a disease is
considered to be zoonotic. Most fungal diseases are non-zoonotic, because fungi typi-
cally grow in soil or water, and are delivered to humans as airborne spores. For exam-
ple, malaria, passed by a mosquito vector, is not a zoonosis, because the reservoir for
organism that causes human malaria is usually another human. If there were no human
carriers of malaria, the incidence of malaria would drop to insignificance. The same is
true for schistosomiasis, river blindness, and elephantiasis. Though these diseases are
transmitted by non-human vectors, their typical reservoir is human. Examples of zoo-
notic diseases are:
Anthrax
Babesiosis
Balantidiasis
Barmah Forest virus disease
Bartonellosis
Bilharzia
Bolivian hemorrhagic fever
Borna virus infection
Borreliosis (Lyme disease and others)
Bovine tuberculosis
Brucellosis
Campylobacteriosis
Cat scratch disease
Chagas disease
Cholera
Cowpox
Creutzfeldt
Jakob disease (vCJD)
Crimean
Congo hemorrhagic fever
Cryptosporidiosis
Cutaneous larva migrans
Dengue fever
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