Fecal PCR test for canine schistosomiasis
The sensitivity of the assay is 1-2 eggs per 1 g of feces. The
PCR will amplify DNA that is directly extracted from fecal
For this test we will require up to 1 gram of fresh feces. The
sample should be taken from the abnormal loose stool.
For storage and shipping, please collect the sample and store in
the refrigerator for up to one week before shipping. Fresh samples
are ideal. Please ship samples cooled overnight with a gel ice
Turnaround: 1-2 business days after receipt of
General information about Heterobilharzia
Recently, there have been several reports of canine
schistosomiasis along the Gulf Coast. The causative agent,
Heterobilharzia americana (Figure 1), is
a trematode that is closely related to Schistosoma
spp., which is known to infect humans in emerging countries.
Transmission is via penetration of the skin by cercariae in water
sources containing the snail intermediate host. The natural
reservoirs for H. americana are raccoons and other
Figure 1: Heterobilharzia americana miracidum. This
is the infective stage for the snail intermediate host (photograph
courtesy of Dr. Thomas Craig, Texas A&M University).
Clinical signs of infected dogs are poorly described, but
include weight loss, diarrhea, hematochezia, and other clinical
signs related to the GI tract. Additionally, in severe infections,
hepatic disease can be seen. Diagnosis can be difficult, primarily
due to the lack of consistent clinical signs and the lack of
suspicion by the veterinarian in endemic areas. A complete blood
count and a serum chemistry profile are often normal. However, many
dogs present with hypercalcemia with decreased serum parathyroid
hormone concentrations and/or an increased serum parathyroid
hormone-related protein (PTHrP) concentrations. Some dogs are
erroneously diagnosed with neoplasia and hypercalcemia of
malignancy when in fact these dogs have hypercalcemia due to the
granulomatous disease caused by Heterobilharzia.
Schistosomiasis should be on the differential list for dogs with
the aforementioned clinical signs, living in endemic areas, and
access to standing water.
The clinical diagnosis is generally made by demonstration of the
egg in feces (Figures 2 ) or by histopathology of intestinal or
hepatic biopsies. However, the trematode egg can only be identified
by sodium chloride sedimentation. As fecal sedimentations are not
routinely performed in clinical practice, the GI Lab has developed
a PCR-based assay for the detection of DNA from the eggs in feces.
The PCR is highly sensitive and reliably detects 1-2 eggs per gram
of feces. This PCR can also be used to demonstrate the organism in
hepatic and intestinal biopsies.
For sample submission, at least one gram of fresh frozen feces
should be shipped overnight. It may be of benefit to consider
sending feces from 2 or 3 different days as shedding may be
intermittent. There are no special sample handling requirements for
this new assay.
Treatment is usually with high doses of praziquantel (25 mg/kg
PO q8h for 2 days) or prolonged treatment with fenbendazole (40
mg/kg PO SID for 10 days, repeat in 3 weeks).
Figure 2: Heterobilharzia americana egg as
visualized using sodium chloride precipitation (photograph courtesy
of Dr. Thomas Craig, Texas A&M University).
- Flowers JR, Hammerberg B, et al. Heterobilharzia
Americana infection in a dog. J Am Vet Med Assoc 2002 Vol 220 (22)
- Fradkin JM, Braniecki AM, et al. Elevated parathyroid
hormone-related protein and hypercalcemia in two dogs with
Schistosomiasis. J Am Anim Hosp Assoc 2001 Vol 37 pp.349-55
- Slaughter II JB, Billups LH, et al. Canine heterobilharziasis.
Comp Cont Educ Pract Vet 1998 Vol 10 pp. 606-612
"This service is performed pursuant to an agreement with
Roche Molecular Systems, Inc."
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