Objective—To determine the usefulness of retina samples for detection of disease-associated prion protein by use of a commercially available enzyme immunoassay (EIA) intended for rapid identification of sheep and cattle with transmissible spongiform encephalopathies (TSEs).
Samples—Retina, brainstem at the level of the obex, and retropharyngeal lymph node samples obtained from 15 TSE-inoculated sheep (scrapie [n = 13] or transmissible mink encephalopathy passaged through a bovid ); retina and brainstem samples obtained from 11 TSE-inoculated cattle (transmissible mink encephalopathy passaged through a bovid  or classical BSE ); and negative control tissue samples obtained from 2 sheep and 2 cattle that were not inoculated with TSEs.
Procedures—Tissue samples were homogenized and analyzed for detection of abnormally folded disease-associated prion protein with a commercially available EIA and 2 confirmatory assays (western blot analysis or immunohistochemical analysis).
Results—Retina sample EIA results were in agreement with results of brainstem sample EIA or confirmatory assay results for negative control animals and TSE-inoculated animals with clinical signs of disease. However, TSE-inoculated animals with positive confirmatory assay results that did not have clinical signs of disease had negative retina sample EIA results. Retina sample EIA results were in agreement with brainstem sample immunohistochemical results for 4 TSE-inoculated sheep with negative retropharyngeal lymph node EIA results.
Conclusions and Clinical Relevance—Results of this study suggested that retina samples may be useful for rapid EIA screening of animals with neurologic signs to detect TSEs.
In sheep, scrapie is a fatal neurologic disease that is caused by a misfolded protein called a prion (designated PrPSc). The normal cellular prion protein (PrPC) is encoded by an endogenous gene, PRNP, that is present in high concentrations within the CNS. Although a broad range of functions has been described for PrPC, its entire range of functions has yet to be fully elucidated. Accumulation of PrPSc results in neurodegeneration. The PRNP gene has several naturally occurring polymorphisms, and there is a strong correlation between scrapie susceptibility and PRNP genotype. The cornerstone of scrapie eradication programs is the selection of scrapie-resistant genotypes to eliminate classical scrapie. Transmission of classical scrapie in sheep occurs during the prenatal and periparturient periods when lambs are highly susceptible. Initially, the scrapie agent is disseminated throughout the lymphoid system and into the CNS. Shedding of the scrapie agent occurs before the onset of clinical signs. In contrast to classical scrapie, atypical scrapie is believed to be a spontaneous disease that occurs in isolated instances in older animals within a flock. The agent that causes atypical scrapie is not considered to be naturally transmissible. Transmission of the scrapie agent to species other than sheep, including deer, has been experimentally demonstrated as has the transmission of nonscrapie prion agents to sheep. The purpose of this review is to outline the current methods for diagnosing scrapie in sheep and the techniques used for studying the pathogenesis and host range of the scrapie agent. Also discussed is the US scrapie eradication program including recent updates.
Objective—To evaluate gross, histopathologic, and
serum biochemical findings caused by Leptospira
interrogans serovars pomona and bratislava inoculated
Animals—Twenty-seven 8-week-old female Beagles.
Procedure—Dogs were randomly assigned to challenge
or control groups. Challenge groups were conjunctivally
inoculated on 3 successive days with
5 ×107L interrogans serovar pomona (n = 12) or
serovar bratislava (11). Clinical signs were recorded
throughout the experiment, and clinical pathology
assays, bacteriologic culture, and necropsies (6 or 7
dogs necropsied at each time point) were done on
postinoculation day (PID) 7, 10, 14, and 20.
Results—Infection could not be confirmed in any
serovar bratislava–inoculated dog, and control dogs
remained healthy throughout the experiment.
Positive culture and fluorescent antibody test results
were confirmed in 11 of 12 serovar pomona–inoculated
dogs. Fever and lethargy starting at PID 7 were
the most common clinical signs in serovar
pomona–infected dogs. On day 10, gross lesions
included multifocal renal and pulmonary hemorrhage
and perirenal edema. Serovar pomona–inoculated
dogs had histopathologic lesions including hepatitis,
interstitial nephritis, and pneumonia at PID 7, 10, 14,
and 20. Increases in BUN, anion gap, and bilirubin
concentration occurred on PID 10, 14, and 20.
Platelet counts in dogs with positive results of bacteriologic
culture were decreased from baseline values
on PID 10, 12, and 14.
Conclusions and Clinical Relevance—
Conjunctival inoculation with L interrogans serovar
pomona resulted in a high rate of infection with concomitant
hemorrhagic and inflammatory lesions of
the kidneys, liver, and lungs. (Am J Vet Res
Objective—To develop a method for inducing acute
leptospirosis in dogs.
Animals—31 nine-week-old female Beagles.
Procedure—Beagles were randomly assigned to 2
inoculation groups or a control group. Dogs were
inoculated on 3 successive days by conjunctival instillation
of 5 X 107 cells of Leptospira kirschneri serovar
grippotyphosa strain 82 (12 dogs) or strain RM 52 (14
dogs). Control dogs (n = 5) were similarly inoculated
with sterile leptospiral culture media. Clinical signs,
clinicopathologic variables, anti-leptospiral antibody
titers, and evidence of leptospires in tissues and body
fluids were evaluated. Dogs were euthanatized and
necropsied on days 7, 14, 22, or 28 after inoculation or
as required because of severe illness.
Results—Clinical signs in infected dogs included conjunctivitis,
lethargy, diarrhea, dehydration, vomiting,
and icterus. Consistent clinicopathologic alterations
included azotemia, hyperphosphatemia, increased
anion gap, hyperbilirubinemia, and an increase in alkaline
phosphatase activity. Leptospires were cultured
from the kidneys (11/12), urine (6/9), aqueous humor
(9/12), blood (12/12), and liver (12/12) of dogs inoculated
with strain 82. Only 3 of 14 dogs became infected
after inoculation with strain RM 52.
Histopathologic lesions in infected dogs included
interstitial nephritis, renal tubular degeneration and
necrosis, pulmonary hemorrhage, and hepatic edema
Conclusions and Clinical Relevance—Conjunctival
exposure to L kirschneri serovar grippotyphosa strain
82 resulted in acute leptospirosis in all inoculated
dogs, but only 3 of 14 dogs inoculated with strain RM
52 became infected. This method of infection by
serovar grippotyphosa can be used to study the
pathogenesis and prevention of leptospirosis in dogs.
(Am J Vet Res 2004;65:1100–1107)