Page 338 - Review of Medical Microbiology and Immunology ( PDFDrive )

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mebooksfree.com mebooksfree.com mebooksfree.com humans: preexposure and postexposure immunization. 327 mebooksfree.com
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CHAPTER 39 RNA Enveloped Viruses
There are two approaches to prevention of rabies in
sensation at the bite site called paresthesias. After the pro-
drome, rabies manifests as either of two forms: “furious”
Preexposure immunization with rabies vaccine should be
(encephalitic) or “dumb” (paralytic). The furious form
occurs in about 80% of cases. In the furious form, agitation,
given to individuals in high-risk groups, such as veterinarians,
zookeepers, and travelers to areas of hyperendemic infection
delirium, seizures, and hydrophobia occur. Hydrophobia is
an aversion to swallowing water because of painful spasm
of the pharyngeal muscles. In contrast, in the dumb form,
sists of three doses given on days 0, 7, and 21 or 28. Booster
these symptoms do not occur. Rather, the spinal cord is
doses are given as needed to maintain an antibody titer of 1:5.
The rabies vaccine is also used routinely postexposure
primarily involved, and an ascending paralysis occurs. (e.g., Peace Corps members). Preexposure immunization con-
Death almost invariably occurs following both forms, but
(i.e., after the person has been exposed to the virus via ani-
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mal bite). The long incubation period of the disease allows
with the advent of life support systems, a few individuals
the virus in the vaccine sufficient time to induce protective
have survived.
Laboratory Diagnosis
Postexposure immunization involves the use of both the
vaccine and human rabies immune globulin (RIG, obtained
Rapid diagnosis of rabies infection in the animal is usually
from hyperimmunized persons) plus immediate cleaning of
made by examination of brain tissue by using either PCR
the wound. This is an example of passive–active immuniza-
assay, fluorescent antibody to rabies virus, or histologic
tion. Tetanus immunization should also be considered.
staining of Negri bodies in the cytoplasm of hippocampal
The decision to give postexposure immunization depends
neurons (see Figure 39–6). The virus can be isolated from
the animal brain by growth in cell culture, but this takes too
animal attacks demand immunization); (2) whether an attack
long to be useful in the decision of whether to give the
by a domestic animal was provoked, whether the animal was
vaccine. on a variety of factors, such as (1) the type of animal (all wild
immunized adequately, and whether the animal is available to
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Rabies in humans can be diagnosed by PCR assay; by
be observed; and (3) whether rabies is endemic in the area.
fluorescent antibody staining of a biopsy specimen, usually
The advice of local public health officials should be sought.
taken from the skin of the neck at the hairline; by isolation
of the virus from sources such as saliva, spinal fluid, and
be immunized unless a significant exposure has occurred
brain tissue; or by a rise in titer of antibody to the virus.
(e.g., a traumatic wound to the health care worker).
Negri bodies can be demonstrated in corneal scrapings and
If the decision is to immunize, both HDCV and RIG are
in autopsy specimens of the brain.
recommended. Five doses of HDCV are given (on days 0, 3, 7,
14, and 28), but RIG is given only once with the first dose of
Treatment
HDCV (at a different site). HDCV and RIG are given at differ-
There is no antiviral therapy for a patient with rabies. Only
supportive treatment is available.
the antibody in the RIG. As much as possible of the RIG is
given into the bite site, and the remainder is given intramus-
Prevention ent sites to prevent neutralization of the virus in the vaccine by
cularly. If the animal has been captured, it should be observed
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In the United States, the rabies vaccine contains inactivated
for 10 days and euthanized if symptoms develop. The brain of
the animal should be examined by immunofluorescence.
virus grown in human diploid cells. (Vaccine grown in
monkey lung cells or chick embryo cells is also available.) In
The vaccine for immunization of dogs and cats consists
other countries, the duck embryo vaccine or various nerve
tissue vaccines are available as well. Duck embryo vaccine
ally given at 3 months of age, with booster doses given
has low immunogenicity, and the nerve tissue vaccines can
either annually or at 3-year intervals. In the United States,
an alternative vaccine used in dogs and cats contains live
cause an allergic encephalomyelitis as a result of a cross-
canarypox virus genetically engineered to contain the gene
reaction with human myelin. For these reasons, the human
diploid cell vaccine (HDCV) is preferred.
for the envelope protein of rabies virus.
RETROVIRUSES
HUMAN T-CELL LYMPHOTROPIC
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VIRUS
Human T-cell lymphotropic virus-1 (HTLV-1) causes two
distinctly different diseases: a cancer called adult T-cell
There are two important human retroviruses: human T-cell
leukemia/lymphoma and a neurologic disease called
lymphotropic virus, which is described here, and human
HTLV-associated myelopathy (also known as tropical spas-
immunodeficiency virus (HIV), which is described in
tic paraparesis or chronic progressive myelopathy). HTLV-2
Chapter 45.
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