Biomedical Engineering Reference
In-Depth Information
Readers should not confuse “toxocara” with the similar-sounding “toxo-
plasma” (Class Apicomplexa, Chapter 19), a problem aggravated when
insouciant clinicians use the abbreviated and ambiguous form “toxo,” which
can refer to either organism.
Nematoda
Secernentea
Ascaridida
Dioctophymatidae
*Dioctophyme
Dioctophyme renale, also known as the giant kidney worm, is a rare cause of
human disease. Humans, one of many animals serving as the primary host,
are infected by ingesting an undercooked second intermediate host (usually
fish or frogs) that had, in turn, ingested the first intermediate host (a fresh-
water earthworm). Ingested larvae penetrate the human intestine and migrate
to the liver. From the liver, they migrate to a kidney (usually unilateral,
usually the right kidney), where they become adults. Eggs laid by the adult
worm are excreted in the urine. The infestation of large adult worms typi-
cally leads to the destruction of the kidney, if left untreated. Human disease
is rare, and can occur anywhere in the world.
Nematoda
Secernentea
Spirurida
Spirurina
Filarioidea
Onchocercidae
*Brugia
*Loa
*Onchocerca
*Mansonella
*Wuchereria
Filarial nematodes are string-like worms that are sufficiently small to fit into
lymphatic vessels. About 150 million people are infected by the filarial
nematodes (genera Brugia, Loa, Onchocerca, Mansonella, and Wuchereria)
[91]. Wuchereria bancroft and Brugia malayi, together, infect about 120 mil-
lion individuals [91]. Most cases occur in Africa and Asia.
The life cycle for these organisms involves a human primary host, in
which the adult filarial worms produce juveniles (microfilaria) that migrate
through lymphatics and blood vessels, where the microfilaria are sucked out
by a secondary host (i.e., a blood-feeding mosquito or fly). In the secondary
host, they develop into larvae. The secondary host serves double duty as a
