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Biodefense
Reference Library
Foreign
Animal and Zoonotic Disease Center
Zoonotic
Disease Online Course
Presented
by
Stephen M.
Apatow, Director
of Research and Development
Humanitarian
Resource Institute
Biodefense Reference Library
Foreign
Animal and Zoonotic Disease Center
[Vitae][Email]
ZOONOTIC
DISEASES
CESTODE
DIPHYLLOBOTHRIASIS
Centers
for Disease Control and Prevention: Division of Parasitic Diseases
Diphyllobothrium
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
(Fish
tapeworm infection) A benign tapeworm infection of the small intestines
caused by eating raw fish. The causative agents are Diphyllobothrium
latum
and D. pacificum (Cestoda). There is no vaccine. D. latum is common in
northern temperate regions where the fish are eaten raw (e.g., in the
Baltic
countries, Finland and Canada/Alaska). D. pacificum is common in
coastal
South America, especially Peru.
RESERVOIR
AND MODE OF
TRANSMISSION:
The definitive
hosts of D. latum include humans, dogs and cats. For D. pacificum the
natural
reservoir is seals. Two intermediate hosts include a plankton
crustacean
and a freshwater fish. Gravid proglottids pass in the feces of the
definitive
host. The eggs hatch in lakes and waterways and then infect the
crustacean.
Freshwater fish consume these and the larvae encyst in the musculature.
The fish, in their turn, may be eaten by larger fish which can still
transmit
the infection. Humans acquire the parasite by eating raw infected
fish.
INCUBATION
PERIOD:
Humans.
3-6 weeks from ingestion to adult tapeworm. Animals. Unknown but
presumably
as for humans, in dogs and cats.
CLINICAL
FEATURES:
Humans.
The condition is usually asymptomatic. Some patients develop vitamin
B12
deficiency anemia. Massive infection may cause diarrhoea and intestinal
obstruction. Animals. No clinical signs are seen in dogs and cats.
Heavy
infection with larvae can kill the fish intermediate host.
PATHOLOGY:
Humans.
The presence of the large tapeworm, 3 to 10 meters long, in the
intestine
can cause mechanical obstruction. Megaloblastic anemia occurs owing to
vitamin B12 deficiency. Animals. Subclinical. In fish, myositis and
possibly
even death occur in heavy infestation.
DIAGNOSIS:
Humans
and animals. Identify characteristic eggs in feces.
PROGNOSIS:
Humans.
Usually benign. Animals. Usually benign, but heavy infection may be
fatal
to fish.
PREVENTION:
Humans
and animals. Dispose of feces hygienically. Educate for proper cooking
of fish. Freeze fish or salt cure before marketing.
TREATMENT:
Humans
and animals. Anthelmintics, especially niclosamide and
praziquantel.
LEGISLATION:
Humans
and animals. None.
SPARGANOSIS
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
SYNONYM:
Larval
diphyllobothriasis.
ETIOLOGY:
The second
larval stage (plerocercoid or sparganum) of the pseudophyllidean
cestode
of the genus Spirometra (Diphyllobothrium, Lueheela). Several species
of
medical interest have been described: Spirometra mansoni, S.
mansonoides,
S. erinacei-europaei, S. theileri, and S. proliferum. These are the
most
commonly accepted species at the present time, but it should be noted
that
they are difficult to differentiate and that the taxonomy remains in
doubt.
The definitive hosts are mainly domestic and wild canids and felids.
The
development cycle requires two intermediate hosts. The first is a
copepod
(planktonic crustacean) of the genus Cyclops. which ingests coracidia
(free,
ciliated embryos) that develop from Spirometra eggs when they reach the
water with the feces of dogs or cats (definitive hosts). In the tissues
of the copepod, the coracidium turns into the first larva, or
procercoid.
When a second intermediate host ingests an infected copepod, the
procercoid
develops into a second larval form, the plerocercoid or sparganum. The
plerocercoid larva can be harbored by many vertebrates, including
amphibians,
reptiles, birds, small mammals (rodents and insectivores), man,
nonhuman
primates, and swine. Fish do not become infected. Some researchers
believe
that the second intermediate host is usually an amphibian, but can vary
according to region. Numerous species of vertebrates become infected
with
plerocercoids by feeding on amphibians, but they may also develop
plerocercoids
after ingesting water containing copepods infected by procercoids
(first
larva). Several animal species that are not definitive hosts function
as
paratenic or transport hosts, since the larvae they acquire by feeding
on animals infected with plerocercoids encyst again after passing
through
the intestinal wall and migrating to other tissues. This transfer
process
is undoubtedly important in the life cycle; but the fact that many
species
of secondary hosts can be infected directly by ingestion of copepods
containing
procercoids is probably no less important. When the sparganum reaches
the
intestine of the definitive host, it attaches to the mucosa; in 10 to
30
days, it matures into an adult cestode, completing the cycle. The adult
S. mansonoides reaches about 25 cm in length in the intestine of the
definitive
hosts (cat, dog). The sparganum found in the tissues of the secondary
intermediate
hosts and paratenic hosts, including man, varies from 4 to 10 cm in
length.
GEOGRAPHIC
DISTRIBUTION
AND OCCURRENCE:
Sparganosis
is found throughout the world, but human infection is not common. Just
over 450 cases are known, mostly from Japan, China, Korea, and
Southeast
Asia. In the United States, about 60 cases have been described# in
Latin
America and the Caribbean, the disease has been recorded in Uruguay,
Ecuador,
Colombia, Venezuela, Guyana, Belize, and Puerto Rico; about 30 cases
have
been diagnosed in Africa. Infections in the Far East are attributed to
plerocercoid larvae of Spirometra mansoni: in the United States, to S.
mansonoides; in Europe, to S. erinacei-europaei; and in Africa, to S.
theileri.
However, as has already been mentioned, species identification can be
difficult
and therefore uncertain.
THE
DISEASE IN MAN:
The incubation
period, determined in a study of 10 patients who ate raw frog meat,
lasts
from 20 days to 14 months. The most common localizations of the
sparganum
are subcutaneous connective tissue and superficial muscles. The lesion
is nodular, develops slowly, and can be found on any part of the body.
The main symptom is pruritus, sometimes accompanied by urticaria. The
lesion
is painful when there is inflammation. The patient may feel discomfort
when the larva migrates from one location to another. The subcutaneous
lesion resembles a lipoma, fibroma, or sebaceous cyst. Ocular
sparganosis
occurs mainly in Vietnam, Thailand, and parts of China. Its main
symptoms
consist of a painful edema of the eyelids, with lacrimation and
pruritus.
A nodule measuring I to 3 cm forms after 3 to 5 months, usually on the
upper eyelid. Migration of the sparganum to internal organs can give
rise
to the visceral form of the disease. The preferred localizations are
the
intestinal wall, perirenal fat, and mesentery; vital organs are rarely
affected. When the plerocercoid invades the lymphatic system, it
produces
a clinical picture similar to that of Eosinophils are abundant in the
was
near the parasite; examination of blood samples reveals mild
leukocytosis
and increased eosinophilia. An infrequent but serious form is
proliferative
sparganosis caused by Spirometra proliferum. The sparganum of S.
proliferum
is pleomorphic, with irregular branches and proliferative buds that
detach
from the larva and migrate to different tissues in the host, where they
repeat the process and invade other organs. The life cycle of S.
proliferum
is not known.
THE
DISEASE IN ANIMALS:
The adult
cestode, which lodges in the intestine of the definitive host,
generally
does not affect the health of the animal. In cats, however, it may
produce
weight loss, irritability, and emaciation, together with an abnormal or
exaggerated appetite. Infection by the larvae or spargana can be
clinically
apparent when their number is large and especially when they invade
vital
organs. In the intermediate host, the disease is almost always
asymptomatic
if the number of parasites is relatively small.
SOURCE
OF INFECTION
AND MODE OF TRANSMISSION:
Sparganosis
is maintained in nature primarily by contamination of natural or
artificial
bodies of water (lagoons, marshes, lakes, and others) with feces from
felids
and canids infected with Spirometra spp. Contamination of water with
eggs
of Spirometra spp. leads to the infection of copepods and,
consequently,
of the second intermediate hosts that ingest these crustaceans. An
important
means of infection is the transfer of the second larva (sparganum,
plerocercoid)
from one secondary host to another, which increases the number of
animal
species and individuals infected. The common route of infection is
ingestion;
various mammal and bird species become infected by feeding on
parasitized
frogs or snakes. The high rate of infection in wild pigs in Australia
may
be due to this mechanism, although it may also stem from ingestion of
copepods
with drinking-water from lagoons. In any case, contamination of the
water
by wild canids (definitive hosts) that share the habitat assures that
the
cycle is perpetuated. The infection rate in man is low, compared to the
rate in other animals. Man acquires sparganosis mainly by ingesting
larvae
contained in raw or undercooked meat of animals infected with spargana,
such as amphibians, reptiles, birds, and wild mammals. Another mode of
infection, also by larval transfer, is by contact. In Vietnam and
Thailand,
frogs are popularly believe to have an antiphlogistic effect, and their
muscles are applied as poultices. This custom is responsible for ocular
sparganosis. It is also probable that man can acquire sparganosis via
drinking-water
by ingesting copepods infected with procercoids (first larvae). Man is
an accidental host and does not usually play any role in the life cycle
of the parasite. However, under ecologic conditions in some regions of
central Africa, it is suspected that man acts as an intermediate host.
In this region, hyenas are the definitive hosts of Spirometra, and man
is apparently the only host infected with spargana. In these
circumstances,
the infection cycle is maintained as a result of tribal custom of
letting
hyenas devour human corpses.
DIAGNOSIS:
Specific
diagnosis can be made only by removing the nodular lesion and
confirming
the presence of the plerocercoid. Attempts have been made to identify
the
species of Spirometra larvae by infecting dogs and cats via the
digestive
route. For reasons already mentioned, differentiation of species has
proven
difficult. Diagnosis in definitive hosts infected with adult cestodes
can
be made by coprologic examination or autopsy.
CONTROL:
Human
sparganosis can be prevented by avoiding ingestion of contaminated
water
that has not been treated, and by making sure that meat that might
contain
spargana is sufficiently cooked. In the Far East, public health
education
should emphasize the danger of using the tissue of frogs or other
cold-blooded
animals for medicinal purposes.
BERTIELLIASIS
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
AGENT:
Bertiella
studeri and mucronanta, anoplocephalid tapeworms. o 260-300mm length
tapeworm
with 10mm width. o Gravid segments shed off in groups of about 20.
RESERVOIRS
AND INCIDENCE:
NHP's.
TRANSMISSION:
NHP's
acquire the parasitosis by ingesting mites infected with cysticercoid
larvae.
Man can become infected accidentally by ingesting food containing the
mites.
DISEASE
IN NHP'S:
Asymptomatic.
DISEASE
IN HUMANS:
The infection
is usually asymptomatic, but cases with recurrent abdominal pain,
vomiting,
anorexia, constipation, and intermittent diarrhea have been
observed.
DIAGNOSIS:
Diagnosis
is based on microscopic observation of the proglottids eliminated in
the
feces. The egg possesses a characteristic pyriform apparatus.
TREATMENT:
Dichlorophen
PREVENTION/CONTROL:
Control
mites.
DIPYLIDIASIS
Centers
for Disease Control and Prevention: Division of Parasitic Diseases
Dipylidium
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
AGENT:
Dipylidium
caninum - common intestinal cestode of dogs. Gravid proglottids are
"pumpkinseed"
shaped.
RESERVOIRS
AND INCIDENCE:
Dogs,
cats, and their wild counterparts. Arthropods serve as intermediate
hosts.
These include the dog flea (Ctenocephalides canis), the cat flea (C.
felis),
and dog louse (Trichodectes canis). Cosmopolitan including the
U.S.
TRANSMISSION:
Humans,
dogs, and cats are infected by ingestion of arthropod intermediate
hosts
which harbor the cysticercoid larvae.
DISEASE
IN ANIMALS:
Usually
no severe pathology. Possibly mild digestive problems or perianal
pruritus.
DISEASE
IN MAN:
Slight
symptoms, if any. Mild weight loss, perianal itching, diarrhea, vague
abdominal
pain.
DIAGNOSIS:
Recovery
of gravid proglottids that are passed in the feces or that crawl out of
the anus.
TREATMENT:
Niclosamide
or praziquantel.
PREVENTION/CONTROL:
Screen
animals. Treat infected animals. Eliminate ectoparasites. Teach proper
handling of pets to children.
ECHINOCOCCOSIS
Centers
for Disease Control and Prevention: Division of Parasitic Diseases
Alveolar
Hydatid Disease
Office
International des Epizooties
Echinococcosis:
Manual of standards Diagnostic Tests and Vaccines 2000
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
(Hydatidosis,
Hydatid Disease)
AGENT:
Echinococcus
granulosis - causes "cystic" disease. Echinococcus multilocularis -
causes
"alveolar" disease. E. vogeli - causes polycystic disease.
RESERVOIR
AND INCIDENCE
The definitive
host for E. granulosis is a carnivore (all of which, except for the
lion,
are Canidae) that harbors the adult tapeworm in the small intestine.
Human
infection with E. granulosus occurs principally where dogs are used to
herd grazing animals, particularly sheep. The disease is common
throughout
southern S. America, the Mediterranean and Middle East, central Asia,
and
East Africa. Foci of endemicity are in eastern Europe, Russia,
Australasia,
India, and the UK. In North America, endemic foci have been reported
from
the western USA, the lower Mississippi Valley, Alaska, and northwestern
Canada. The life cycle for E. multilocularis involves foxes as
definitive
host and microtine (e.g., voles and meadow mice) rodents as
intermediate
host. Domestic dogs and cats can also become infected with the adult
tapeworm
when they eat infected wild rodents. The disease in humans has been
reported
in parts of central Europe, much of Siberia, northwestern Canada, and
western
Alaska. One case has been reported in Minnesota. The principle
definitive
host for E. vogeli is the bush dog; the main intermediate hosts are the
paca and spiny rat. Domestic hunting dogs are also definitive hosts,
and
serve as an important source of human infection. Cases have been
reported
in South America.
TRANSMISSION:
E. granulosis:
Human infection occurs when eggs passed in dog feces are accidentally
swallowed.
E. multilocularis: Human infection is by accidental ingestion of
tapeworm
eggs passed in fox or dog feces.
DISEASE
IN ANIMALS:
Usually
no clinical signs except for enteritis in heavy infestations. In sheep,
hydatid cysts cause considerable condemnation of meat and loss of
production.
DISEASE
IN MAN:
E. granulosis
- Cystic hydatid disease A liver cyst may remain silent for 10-20 years
or more until it becomes large enough to be palpable, to be visible as
an abdominal swelling, to produce pressure effects, or to produce
symptoms
due to leakage or rupture. There may be right upper quadrant pain,
nausea,
and vomiting. The effects of pressure may result in biliary
obstruction.
If a cyst ruptures, anaphylaxis and death may result. If fluid and
hydatid
particles escape slowly, allergic manifestations may result. Rupture
can
occur into the pleural, pericardial, or peritoneal space or into the
duodenum,
colon, or renal pelvis. Dissemination of germinal elements may be
followed
by the development of multiple secondary cysts. Pulmonary cysts cause
no
symptoms until they leak; become large enough to obstruct a bronchus,
or
erode a bronchus and rupture. Brain cysts produce symptoms earlier and
may cause seizures. Cysts in the bone marrow may present as pain or
spontaneous
fracture. The bones most often affected are the vertebrae and
paraplegia
may develop due to compression of the spinal cord. 20% of patients have
multiple cysts. 15% of untreated patients eventually die. E.
multilocularis
- Alveolar disease The primary localization of alveolar cysts is in the
liver, where they may extend locally or metastasize to other tissues.
The
larval mass has poorly defined borders and behaves like a neoplasm; it
infiltrates and proliferates indefinitely by exogenous budding of the
germinative
membrane, producing an alveolus-like pattern of microvesicles. 90% of
untreated
cases die within 10 years. E. vogeli - Polycystic form of human hydatid
disease. Symptoms are variable according to cyst size and location. The
polycystic hydatid is unique in that the germinal membrane proliferates
externally to form new cysts and internally to form septi that divide
the
cavity into numerous microcysts. Brood capsules containing many
protoscolices
develop in the microcysts.
DIAGNOSIS:
Immunoblot
assay.
TREATMENT:
Currently
the definitive treatment is surgical removal of cysts. Newly available
chemotherapy (albendazole or mebendazole) may alter this position.
PREVENTION/CONTROL:
In endemic
areas, prevention is by prophylactic treatment of pet dogs with
praziquantel
and prevention of feeding dogs offal.
HYMENOLEPIS
DIMINUTA
Centers
for Disease Control and Prevention: Division of Parasitic Diseases
Hymenolepis
Infection
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
(Rat
Tapeworm Infection)
AGENT:
Hymenolepis
diminuta is the common tapeworm of rodents. Size varies from 100-600
mm.
RESERVOIR
AND INCIDENCE
Rodents,
many arthropods (fleas, beetles, and cockroaches) serve as intermediate
hosts.
TRANSMISSION:
Rodents
and humans are infected by accidentally swallowing the infected
arthropods,
usually in cereals or stored products.
DISEASE
IN ANIMALS:
Mild catarrhal
enteritis with diarrhea occurs if the infection is heavy.
DISEASE
IN MAN:
Light
infections are generally asymptomatic. Heavy infections may cause
diarrhea,
abdominal pain, anorexia, vomiting, weight loss, and irritability,
particularly
in young children.
DIAGNOSIS:
Infections
are diagnosed by finding characteristic eggs in feces; proglottids are
usually not seen.
TREATMENT:
Niclosamide
or praziquantel.
PREVENTION/CONTROL:
Eliminate
rodents and insects in facilities.
HYMENOLEPIS
NANA
Disease
Overview:
Institutional
Animal Care and Use Committee, University of California, Santa
Barbara.
AGENT:
Dwarf
tapeworm, Hymenolepis nana - measures 5-90 mm long.
RESERVOIRS
AND INCIDENCE:
The animal
reservoir is the house mouse, but humans can be both definitive and
intermediate
hosts. Worldwide occurrence in warm climates.
TRANSMISSION:
Gravid
proglottids disintegrate and eggs pass in the feces and may be ingested
by another human. Larvae then develop in the intestinal villi and pass
to the lumen of the gut to become the adult forms. Dogs, cats and their
fleas can be infected as well as grain beetles which can serve as
intermediate
hosts.
DISEASE
IN ANIMALS:
Same as
H. diminuta.
DISEASE
IN MAN:
Same as
H. diminuta.
DIAGNOSIS:
Same as
H. diminuta.
TREATMENT:
Same as
H. diminuta.
PREVENTION/CONTROL:
Personal
hygiene, protective clothing and gloves Vermin control. Protect stored
grains and feeds from grain beetles.
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