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Biodefense Reference Library
Foreign Animal and Zoonotic Disease Center
One Medicine: One Health (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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