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environmental, wildlife and zoo assay data sheet
Cryptosporidium
Test codes:
P0008
- Ultrasensitive qualitative screen for
Cryptosporidium by
real time polymerase chain reaction. This screen
detects but does not
differentiate many
Cryptosporidium
species.
Test P0008 is
included in
P0041
- waterborne pathogens screening panel
and in P0047 - ruminant fecal
screening panel
X0033
- Ultrasensitive qualitative detection of
Cryptosporidium serpentis
by real time polymerase chain reaction.
X0034
- Ultrasensitive qualitative detection of
Cryptosporidium varanii (formerly
Cryptosporidium saurophilum) by real time polymerase chain reaction.
Tests X0033
and X0034 are
included in P0052
- snake and lizard quarantine PCR panel
Cryptosporidium
species are parasitic protozoans that are transmitted by
multiple routes; the animal host range is diverse.
All
Cryptosporidium species have tiny (typically measuring only 4-8 um in diameter), thick-walled oocysts which are passed in the
host’s feces and can remain
infective in the environment for months. These oocysts are
extremely resistant to temperature extremes and disinfectants.
As with most protozoan infections, this parasite can be acquired
by exposure to sporulated oocysts in contaminated food, water,
or unhygienic enclosures.
Several of
the 13+ species in the
Cryptosporidium genus have been confirmed as
causative agents of human disease. The following
Cryptosporidium
species are currently accepted, on the basis of host
specificity, pathogenesis, morphology and genotyping:
Infecting
mammals: Cryptosporidium
hominis,
C. parvum, C. wrairi, C. felis, C. canis, C. andersoni,
C. muris and C.
ubiquitum
Infecting
birds: C. baileyi, C.
meleagridis and
C. galli
Infecting
reptiles: C. serpentis
and C.
varanii (formerly C. saurophilum)
Infecting
fish: C. molnari
Phylogenetic
analyses have been largely based on sequencing of the small
subunit rRNA gene (18S rRNA), the hsp 70 gene, or other
housekeeping or structural genes. These analyses reveal that the
various Cryptosporidium
species interact in complex ways with hosts. For example, the
specific host of C. felis
is cats, but this species has also been isolated from a cow,
while C. andersoni
is morphologically close to C. muris but infects cattle rather than mice. And
C. parvum includes a
complex of subspecies that specifically infect cattle, pigs,
kangaroos, ferrets or monkeys.
With the
advance of molecular techniques, knowledge of the epidemiology
of human cryptosporidiosis has significantly improved. It has
been shown that the vast majority of human cases are caused by
C. hominis
(synonymous with C. parvum
genotype 1) and C. parvum
(synonymous with C. parvum
genotype 2). Other species, including
C. meleagridis,
C. felis, C. canis
and C. muris can
also infect humans and are linked to clinical disease, not only
in immunocompromised patients but also in immunocompetent
people.
Cryptosporidium in reptiles:
Cryptosporidiosis is a well-known gastrointestinal disease of
snakes and lizards. Two cryptosporidian species,
Cryptosporidium serpentis
and Cryptosporidium
varanii (known until recently as
Cryptosporidium
saurophilum), are
associated with disease of the gastrointestinal tract in snakes
and lizards.
Other cryptosporidium species, such as
C. parvum and
C. tyzerri, have been
described in snakes and lizards but they are thought to be
associated with ingested prey and are not considered to be
disease-causing for snakes and lizards. These species are
sometimes referred to as “pass-through Crypto” in reptiles.
Cryptosporidium serpentis
C. serpentis is a
gastric parasite found mainly in snakes, and is frequently
associated with prominent clinical signs like anorexia,
postprandial regurgitation, lethargy, midbody swelling, and
weight loss, while C.
serpentis infections in lizards are usually asymptomatic.
Infection by
C. serpentis is one of the most important
health concerns in snakes. The infection is characterized by
chronic clinical or subclinical symptoms. The presence of
hypertrophic gastritis, food regurgitation, progressive weight
loss, mortality, and intermittent or continuous shedding of
oocysts in the feces are some of the possible outcomes of
infection. There is no evidence that C.
serpentis is transmissible to humans or other mammals.
Although the life cycle of C. serpentis is not completely
understood, it is known that there are two infective stages of
the parasite. The first is a thick-walled oocyst which contains
four sporozoites that are released when the oocyst is ingested
by a snake. It is believed that the ingested oocysts invade a
small number of endothelial cells lining the stomach wall.
In these endothelial cells, the parasites undergo asexual
multiplication (schizogony or merogony) and then sexual
multiplication (gametogony), producing microgamonts and
macrogamonts. Upon fertilization of the macrogamonts by the
microgametes, oocysts develop and sporulate in the infected
host. Two different types of oocysts are produced: the
thick-walled, which is commonly excreted by the host after
sporogony, and the thin-walled oocyst, which is primarily
involved in autoinfection.
Cryptosporidium varanii
C.
varanii is an intestinal parasite found mainly in lizards
and sometimes in snakes. It can cause anorexia, progressive weight loss, abdominal swelling
and high mortality, particularly in juvenile lizards. There is no evidence that
C. varanii is transmissible to humans or other mammals, but
the potential for human infection by C.
varanii, especially in immune-compromised patients, cannot
be excluded at this time.
Recent genetic analysis of
C. varanii at the 18S rRNA and actin loci shows
that it is genetically identical to
C. saurophilum. Since C.
varanii was described prior to
C. saurophilum, its
name takes precedence over
C. saurophilum and therefore
C. saurophilum is now considered a junior synonym of
C. varanii.
Similar to other cryptosporidia,
C. varanii is
transmitted mainly through fecal-oral route. Infected reptiles
can be subclinical so it is hard to identify and isolate
potential carriers based on symptoms. The excretion of oocysts
in feces is intermittent so that testing may need to be repeated
several times in order to detect the oocysts. A systematic screening program to
identify infected reptiles, and surveillance of enclosures, can
contribute to ensuring a pathogen-free colony of reptiles, and
to the safety of pet owners.
Because of their small size, it is very hard to detect
Cryptosporidium oocysts by microscopic examination, so diagnosis
of cryptosporidial infection by fecal examination has low
sensitivity and is not suitable to differentiate cryptosporidial
species. Immunofluorescence detection of
Cryptosporidium lacks
the specificity to identify the species. However, molecular
detection by polymerase chain reaction is a highly sensitive,
specific and rapid method to identify the cryptosporidial
species present (Pedraza-Diaz et al., 2009;
da Silva et al., 2014).
Since oocysts are
only intermittently shed, multiple samples taken at
intervals can increase the likelihood of detection.
Utilities:
-
Help confirm the disease causing agent
-
Shorten the time required to confirm a clinical
diagnosis of
Cryptosporidium infection.
-
Help ensure that animal groups and facilities are free of
Cryptosporidium species
-
Early prevention of spread of these protozoa
-
Minimize human exposure to these protozoa
References:
Thomas, A.L. and Chalmers, R.M. (2003) Investigation of the
range of Cryptosporidium
species detected by commercially available antibody-based tests.
Proceedings of the Health Protection Agency Inaugural
Conference, Warwick, September.
Pedraza-Díaz, S., Ortega-Mora, L.M., Carrión, B.A., Navarro, V.
and Gómez-Bautista, M. (2009) Molecular characterisation of
Cryptosporidium isolates from pet reptiles. Vet. Parasitol.
160:204-210.
da Silva, D.C., Paiva, P.R., Nakamura, A.A., Homem, C.G., de Souza, M.S.,
Grego, K.F. and Meireles,
M.V. (2014) The detection of Cryptosporidium serpentis in snake
fecal samples by real-time PCR. Vet. Parasitol. 204:134-138.
Specimen requirements: 0.2 ml feces, or rectal swab,
or 0.2 ml cloacal wash,
or 0.2 ml gastric lavage, or swab of mucous adhered to
regurgitated prey items; or 0.2 ml fresh, frozen or fixed
gastric or intestinal tissue.
Contact Zoologix
if advice is needed to determine an appropriate specimen type
for a specific diagnostic application. For specimen
types not listed here, please contact Zoologix to confirm
specimen acceptability and shipping instructions.
For all
specimen types, if there will be a delay in shipping, or during
very warm weather, refrigerate specimens until shipped and ship
with a cold pack unless more stringent shipping requirements are
specified. Frozen specimens should be shipped so as to remain
frozen in transit. See shipping
instructions for more information
Turnaround time:
2 business days
Methodology:
Qualitative real time PCR
Normal range:
Nondetected
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