TurkeyPoult
Enteritis
The turkey industry in Indiana
ranks seventh in the US
with 15 million turkeys (5.1% of US turkeys) in production
yearly and a market value of $140.4 million. Turkeypoult
enteritis (also referred to as "spiking mortality of
turkey poults") has contributed to significant economic
losses encountered by a large number of turkey producers
in Indiana
for the last several years. As an example of the magnitude
of losses due to this disease, the estimated cost (mortality,
stunting, and medication) in DuBois
County alone
in 1994 was $19.26 million. A similar disease has also been
identified in western and eastern North
Carolina, South
Carolina, Georgia,
Virginia,
New York and
other states. Outbreaks of this disease have resulted
in major economic hardships for turkey farmers in North
Carolina in 1995 and 1996.
The clinical signs of turkey poult enteritis usually appear
at 7 to 28 days of age and have diarrhea, chirping, litter
eating, decreased feed efficiency, decreased weight gain,
and uneven flock growth. The morbidity is usually high
and mortality may be low; however, mortality over 40 to
50% occasionally occurred in Indiana
flocks in 1993. Diagnosticians at ADDL and SIPAC have shown
that turkey poult enteritis can be experimentally induced
by gavaging turkey poults with intestinal contents from
affected poults. Electron microscopic examination of intestinal
contents from affected turkey poults often revealed coronavirus.
In addition, intestines were often positive for coronavirus
by fluorescent antibody testing. However, attempts to
isolate turkey coronavirus using various cell lines have
not been successful. Turkey
embryos have been used for the isolation, propagation and
characterization of turkey coronavirus. Turkeycoronavirus
from affected intestinal contents filtered at 0.22 microns
has been successfully passaged and propagated in turkey
embryos. This is the only in vivo system available
in propagating turkey coronavirus.
Fluorescent antibody testing and electron microscopic examination
of the intestines from the passaged turkey embryos have
revealed the presence of turkey coronavirus. The infected
intestines were often dilated and contained gas and greenish-brown
fluid. By the fifth passage, the intestines had slight villous
blunting, increased villous epithilialvacuolation, and multifocaldilation
of crypts histologically. Turkeycoronavirus
has also been purified from the intestines of infected turkey
embryos in the fifth passage by sucrose density
gradient ultracentrifugation. The virions banded at a
buoyant density of 1.18 to 1.20 g/ml and that of 1.14 g/ml
in sucrose gradients, similar to reports for the other turkey
coronaviruses isolated at Minnesota
and Canada
previously. In addition, sucrose density gradient purified
material has been demonstrated to contain turkey coronavirus
by electron microscopy and immunoelectronmicroscopy.
The purified turkey coronavirus also proved to be infectious
to turkey embryos.
Diagnosticians at ADD1 and SIPAC conducted a study in an
attempt to experimentally reproduce turkey poult enteritis
in seven-day-old turkey poults using sucrose density gradient
purified embryo intestinal material from serially passaged
turkey embryos. Clinically, the infected turkey poults
showed ruffled feathers, acute enteritis, and decreased
weight gain. Microscopically, the villi, particularly in
the jejunum and ileum, revealed marked villous atrophy.
It appears that turkey poult enteritis can be caused by
turkey coronavirus.
Although there is no effective treatment for turkey poult
enteritis, strict biosecurity and use of crumble feed are
helpful in reducing the severity of the disease. In order
to effectively diagnose and control turkey poult enteritis,
continuous monitoring of turkey poult intestines and sera
from the field by fluorescent antibody testing, further
characterization of turkey coronaviral protein, production
of monoclonal antibody to turkey coronavirus development
of eruyme-linked immunosorbent assay (ELISA) for turkey
coronaviral antibody or turkey coronavirus, genomic sequence
comparison of turkey coronavirus isolate from Indiana
with that from Minnesota, Canada, North Carolina, and other
states and application of polymerase chain reaction (PCR)
for the detection of turkey coronavirus are under way.
- prepared by Tsang Long Lin,DVM,PhD
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