Biomedical Engineering Reference
In-Depth Information
stringently followed with particular attention to access
control, strict isolation, and personnel practices until
a diagnosis is confirmed.
associated cases with eight human deaths have been
reported. However, the 17D strain is in the Biosafety
Level 2 category, provided that personnel working with
this virus have been vaccinated (
Centers for Disease
Control/National Institutes of Health, 2009
). Isolation of
the virus from African green monkeys has been reported
(
Enviro-Control, 1979
), and mosquitoes capable of
transmitting the virus are common. Therefore, screening
with strict control of flying insects is essential for
facilities housing newly imported animals from Africa or
South America.
Yellow Fever
The RNA flavivirus that causes yellow fever is endemic to
tropical areas of the Americas and Africa, where it is
transmitted by Aedes spp. mosquitoes. This disease is still
a major public health problem in tropical areas where most
nonhuman primates originate. The
World Health Organi-
zation (WHO) (1990b)
reported extraordinary activity for
yellow fever in 1986
e
1988, with the largest number of
cases since 1948 in Africa and since 1952 in South America.
In urban areas of the Americas where A. aegypti
mosquitoes have not been eradicated, transmission is from
person to monkey to person, and the potential for wide-
spread epidemics persists. A sylvatic or jungle form of
yellow fever is maintained as endemic by the mon-
key
e
mosquito
e
monkey cycle in the forest canopies. The
vectors are A. africanus (
Haddow, 1969
) in Africa and
A. leucocelaenus in Central and South America (
Pinhiero
et al., 1981
). Human cases are sporadic and are usually
related to epizootics in the monkey population or to forestry
operations which bring mosquitoes from the treetops to
people on the ground. In African urban
e
rural transition
areas, both monkeys and people serve as intermediate hosts.
Yellow fever virus infection in African monkeys is
apparently acquired by young animals, inwhich the disease is
mild and immunity develops, as shown by readily demon-
strable antibody titers. In New World monkeys, epizootic
disease is characterized by fever, anorexia, vomiting, yellow-
to-green urine, albuminuria, and jaundice. Human disease is
comparable to that seen in New World monkeys.
Dengue
The four RNA-containing flavivirus serotypes that cause
dengue fever are arboviruses transmitted by the bite of
Aedes spp. mosquitoes. Human and nonhuman primates are
the natural hosts. The human disease is usually character-
ized by a “saddle-back” fever of sudden onset with head-
ache, prostration, “breakbone” muscle and joint pain, and
a maculopapular rash that appears when the body temper-
ature rises after an afebrile period. However, the dengue
viruses can also produce a hemorrhagic fever syndrome and
death.
In the USA dengue has been a public health problem
primarily in the south, where A. aegypti mosquitoes are
found. In southeast Asia, where the incidence of dengue-
related hemorrhagic fever has been increasing since 1940,
dengue is transmitted by A. albopictus. Dengue fever is
considered one of the viruses with the greatest potential for
“emergence” in the near future (
Morse and Schluederberg,
1990
)becauseA. albopictus, an aggressive mosquito species,
was introduced into the USA in 1985 and has already become
established in at least 18 states (
Francey et al., 1990
).
Prevention
Since monkeys are natural hosts of the dengue
virus and the disease is endemic in their native habitats, any
newly imported nonhuman primates could be a source of
human infection (
Vasilakis and Weaver, 2008
). Animal
housing, and quarantine areas in particular, should have
mosquito-proof screening and stringent flying insect control
measures, which may include ultraviolet light electric insect
traps in animal rooms. In the jungle, Aedes spp. develop in
water-holding holes in trees, but in populated areas they
prefer man-made containers. It is hypothesized that A.
albopictus came into the USA in used tire casings. There-
fore, part of an arthropod control program must include
maintaining the grounds surrounding animal facilities free
of cans, containers, and other refuse that could hold water
and provide breeding grounds for the Aedes spp.
Prevention
The severity of disease varies markedly
among species, but most nonhuman primates are suscep-
tible to yellow fever. Therefore, animals coming from areas
in which the virus is endemic could be infected without
showing overt symptoms. For this reason, imported
monkeys should have certification that they come from an
area free of yellow fever, have been held in a double-
screened, mosquito-proof enclosure, or have been vacci-
nated against yellow fever.
All imported nonhuman primates that die within 10
days of arrival should be necropsied with special attention
to lesions that may indicate yellow fever. Necrotic,
hemorrhagic, and bile-stained organs are seen grossly, and
the characteristic histopathological finding is massive mid-
zonal liver necrosis with eosinophilic intracytoplasmic
inclusions known as “Councilman bodies,” derived from
necrotic hepatocytes (
Fox et al., 1984
).
Animal Biosafety Level 3 is recommended for yellow
fever. Thirty-eight
West Nile Virus
An epidemic of West Nile Virus, an arbovirus spread via
mosquito, swept the USA in 2002
e
2003. Many people
laboratory or
laboratory-animal-
