Biomedical Engineering Reference
In-Depth Information
However, they are highly pathogenic to all nonhuman
primates and are found in both New and Old World species
(
Middleton, 1966; Moore, 1970
).
immediate hypersensitivity skin tests. The ELISA test may
prove to be valuable for evaluating efficacy of treatment
because titers declined or disappeared in most of the treated
patients in a human study (
Neva, 1986
).
Prevention
The intermediate hosts for acanthocephalans
are cockroaches (
Whitney, 1976
). They are included in this
discussion to emphasize the need for vermin control in
primate animal housing.
Prevention
Biosafety Level 2 is recommended for
housing research animals with strongyles, but special
attention to animal husbandry routines is essential. The
short life cycle of strongyles mandates daily removal of
fecal waste from animal housing to prevent increasing
infection by the rhabditiform larvae that become infective
filariform larvae within 1
e
2 days. Animals kept on dirt
floors or in bedding are likely to have massive infections
because of the ability of this parasite to multiply rapidly in
a short-term, free-living phase.
Intensive treatment in conjunction with a strict sani-
tation program is the only way to diminish infection with
Strongyloides. Even in human patients using excellent
hygienic practices, complete eradication is almost
impossible because even a few residual parasites can
maintain infection via the internal autoinfection route
(
Neva, 1986
). Protection of personnel in an animal facility
requires strict adherence to the requirements of wearing
gloves, masks, and protective clothing to prevent fecal
material from contacting skin or mucous membranes
during husbandry routines or
Nematodes
The nematodes, round or thread-like worms, include many
genera of endoparasites that are pathogens of both human
and nonhuman primates.
Strongyloidiasis
Strongyloidiasis, caused by Strongyloides stercoralis is
an important and significant human parasitic disease
because it is difficult to diagnose and has the potential to
cause serious or even lethal diseases in immunosup-
pressed individuals, especially those on steroids (
Neva,
1986
). The Strongyloides spp. of nonhuman primates are
very common and equally important parasites. An
increased incidence of Strongyloides fulleborni was noted
in immunocompetent rhesus macaques with chronic
diarrhea (
Sestak et al., 2003
). Transmission of both the
human and primate strongyle species from monkeys to
man has been demonstrated (
Whitney, 1976; Hira and
Patel, 1980
).
Two important differences exist between the life cycle
of Strongyloides and that of other intestinal nematodes that
enhance the ability of these parasites to be transmitted and
to survive: (1) larvae, rather than eggs, are passed in the
feces, and (2) they are capable of producing internal
autoinfection. The rate at which strongyles pass through
this life cycle is significant. Rhabditiform larvae appear in
the feces within 1 week after infective larvae are ingested
so the autoinfection route has also been established within
this time; those that pass in feces can mature and reproduce
sexually to produce more than 20 times their original
numbers in infective larvae in as few as 5 days (
Whitney,
1976
).
research handling of
animals.
Enterobius
Almost all primates have their own host-specific species of
pinworm, and Enterobius vermicularis, the human
pinworm, is prevalent in chimpanzees and is occasionally
seen in other captive primate animals (
Whitney, 1976
).
They are often considered unimportant commensals, but
a heavy infestation can produce intestinal obstruction in
infants, and scratching can produce considerable trauma
with subsequent local infection. Infective ova of these
parasites are deposited on the perianal skin, rather than
within the gut, where they are mixed into the feces.
Deposition of ova on the perianal and perineal skin by adult
female worms is accompanied by a pricking or itching
sensation which stimulates the host to grab or scratch the
area, thereby spreading the ova from hand to mouth for
reinfection, from hand to hand to other animals in close
proximity, or to environmental surfaces. These ova, which
are resistant to drying and remain viable for 3 weeks,
become widespread in the air and dust so transmission to
people who enter a room where there are infected animals
is possible.
Diagnosis
Demonstration of larvae in a direct fecal smear
is the most simple diagnostic method. However, larval
excretion is often sporadic and scanty so standard
concentration techniques such as the formalin
e
ether
method may fail to demonstrate suspected infections, and
the Baerman concentration method (
Neva, 1986
), which
examines 20
e
50 g of stool, may be necessary.
Several negative stool examinations may not conclu-
sively rule out low level Strongyloides infections, so sero-
diagnostic tests have been developed using larval antigens
in enzyme-linked immunosorbent assays (ELISA) and
Treatment and Control
Biosafety Level 2 is recom-
mended with special attention to husbandry. In human
patients, treatment is usually not indicated because the
