Biomedical Engineering Reference
In-Depth Information
Secondary host Synonymous with intermediate host. See Intermediate host.
Serotype Subtypes of a species of bacteria or virus that differ in their surface antigens.
Serovar Same as serotype. See Serotype.
Taxonomic order In traditional taxonomy, the hierarchical lineage of organisms is
divided into a descending list of named orders: Kingdom, Phylum (Division), Class,
Order, Family, Genus, Species. In recent times, taxonomists have deemed it necessary
to add many more formal categories (e.g. supraphylum, subphylum, suborder, infra-
class, etc.). In some cases, where no named subdivision exists, a new class is created
and given an “unranked” order. In many cases, the reason for these additional divisions
relates to the need to impose monophyly on classes. A good example is the unranked
class, Discoba. Molecular phylogenetic evidence has come to light suggesting that
Class Jakobid is closely related to Class Percolozoa and Class Euglenozoa. Because
these classes (Jakobid, Percolozoa, Euglenozoa) seem to have a common direct ances-
tor, they need to be assigned a common superclass. In this particular case, a superclass
for these three sister classes was invented: Class Discoba. Because no named subdivi-
sion (i.e. rank) was available for Class Discoba, it is considered an “unranked” class.
Aside from being an undue burden upon students who are trying to understand the
practical aspects of biological taxonomy, it seems somewhat absurd to have a system
larded with orders given an official label of “unranked.” In this topic, all classes are
simply referred to as order “Class,” followed by the name of the class. Each class has
one named parent class. When you know the name of the parent for each class, you
can determine the complete ancestral lineage for every class and species within the
classification.
Taxonomy The science of classification, derived from the ancient Greek taxis, “arrange-
ment,” and nomia, “method.” Naturalists use the word “taxonomy” to include the
hierarchy of ancestral organisms and their descendants, and the names assigned to the
classes and species of organisms. The product of the taxonomic effort is a classifica-
tion, and the nomenclature for the species and classes is collectively called “the
taxonomy.” When used to describe the general field of classification, “taxonomy” is
synonymous with “systematics.”
Tick Ticks are members of Class Chelicerata (Chapter 29) and should not be confused
with insects (Chapter 30). The hierarchy for the tick, Ixodes, is: Ixodes: Ixodinae:
Ixodidae: Ixodoidea: Ixodida: Parasitiformes: Acari: Arachnida: Chelicerata:
Arthropoda. Species
Ixodes scapularis
transmits
Babesia microti
(babesiosis),
Borrelia
burgdorferi
(Lyme disease), and
Anaplasma phagocytophilum
(human granulocytic
anaplasmosis) [78]. Tick-borne viruses include: Crimean-Congo hemorrhagic fever,
tick-borne encephalitis, Powassan encephalitis, deer tick virus encephalitis, Omsk hem-
orrhagic fever, Kyasanur Forest disease (Alkhurma virus), Langat virus, and Colorado
tick fever.
Vector An organism that moves a disease-causing organism from one host to another.
Diseases spread by vectors include: malaria, plague, leishmaniasis, African trypanoso-
miasis, relapsing fever, yellow fever, dengue fever and dengue hemorrhagic fever,
hantavirus disease, West Nile encephalitis, Japanese encephalitis, Rift Valley fever,
Venezuelan equine encephalitis, and chikungunya. All arboviruses have arthropod
vectors, and there are about 100 known arboviruses that cause human disease [76].
One vector can carry more than one type of infectious organism. For example, a single
species of Anopheles mosquito can transmit
Dirofilaria immitis
, O'nyong'nyong fever
