Research Results - (PDF, 101 mb) - USAID

Problem Statement and Approach
Analyses of serum antibody levels to
enterotoxin are currently underway. Following
modified vaccination procedures, the serum
samples collected from dams and neonates must
be analyzed for anti-enterotoxin content in order
to optimize immunoprotection. Following
optimization, large-scale vaccination programs
can be established. Generally, the procedures
for evaluation of the enterotoxin toxoid as a
vaccine will be those described in a previous
workplan. Adult alpaca!, and ewes will be
vaccinated with enterotoxin toxoid and serum
samples will be collected from all vaccinated
and control dams and neonates. These sera will
be assayed by ELISA for anti-enterotoxin antibodies.
Then morbidity/ mortality data for
vaccinates and controls will be compared.
The research to date has been directed at
identifying colonization antigens on the alpaca
E.coli. Antisera developed have been used to
identify at least two new colonization antigens.
The new isolates will be tested to determine
whether these same, or different, colonization
antigens are produced. Control of colibacillosis
in calves, pigs, and lambs has been successful
using colonization antigen-based vaccines.
When we are confident that we have identified
the most common colonization antigens in
alpaca E. coli, a bacterin could be produced that
would stimulate protection against E.coli.
For objective 2, to identify and characterize
fimbriae of alpaca E.coli, agglutination
experiments will be performed using rabbit
antisera to alpaca E.coli colonization antigens
one and two (developed at Colorado State U.).
Then monoclonal antibodies reactive with
alpaca E. coli colonization antigens will be
prepared. Thirdly, all 140 alpaca E. coli isolates
will be examined for expression of colonization
antigens using monoclonal antibodies. Finally,
if results indicate two or three antigens are
predominant, an E.coli bacterin for prevention
of colibacillosis in alpacas will be developed,
Justification
Enteritis is the major cause of death of
young alpacas and lambs. Clostridium
perfringens type A enterotoxemia has been
established as the main cause of enteritis. The
development and use of a toxoid vaccine has
been purported as the best means for preventing
enterotoxemia. In addition to C. perfringens,E.
coli has been established as a cause of neonatal
enteritis. Sixty-five isolates are currently in the
culture collection at Colorado State University.
An additional 80 isolates were obtained in 1989.
Project Progress
1.1 Evaluation of protection of neonatal alpacas
and lambs against entero-toxemia by
vaccination of their dams with C. perfringens
enterotoxin.
Both the sporulated C. perfringenstype A
(CPA) vaccine and crude ET toxoid have been
demonstrated to possess antigenic properties
which induce the production of IgG in rabbit.
Fifteen pregnant alpacas were immunized in an
alpaca herd in Cuzco, but we could not carry
out the sampling of the offspring due to administrative
interference in the project. However,
we have on hand the vaccines in order to conduct
the vaccination trial in preg,nant alpacas of
the South American Unit in the Veterinary
School, University of San Marcos. On the other
hand, we have been analyzed the detection of
the anti-enterotoxin antibodies from the previous
vaccination study. The results from this
study will be published under the title "C.
perfringens enterotoxin toxoid induces humoral
immunity in alpaca."
1.2 Immunological evidence for intestinal
absorption of C. perfringensenterotoxin in
enterotoxemic llamas.
The presence of C. perfringenstype A
(CPA) enterotoxin in serum and peritoneal fluid
as well as intestinal contents from 15 presumptive
enterotoxemic cadavers of neonatal llamas
(4 to 29 days old) was demonstrated by a monoclonal
antibody-mediated immunoperoxidase
dot assay. Nine (100%) peritoneal fluids exam­
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