Abstract :
Corynebacterium pseudotuberculosis is the agent of alpaca’s lymphadenitis. The present study was to demonstrate the effect
of a primary infection with low (1.1×103), moderate (1×104), and high (1.2×105) doses of C. pseudotuberculosis against a
significant higher challenge dose of 9×108 CFU of C. pseudotuberculosis. Three groups of 4 healthy male alpacas were inoculated
subcutaneously (SC) in the left flank behind the costal arch with the above doses of bacteria. A fourth group of 4 alpacas was sham
inoculated with phosphate buffered saline as control. After 5 weeks all animals were challenged with a dose of 9×108 CFU of C.
pseudotuberculosis inoculated SC in the right flank. The alpacas were clinically inspected for local and regional abscesses, body
temperature and behavior changes. The primary infected alpacas had a febrile response, and abscesses at the inoculation point and
regional lymph nodes. However, after challenge, the primary infected animals showed no superficial lesions or febrile response.
In contrast, the immune na¨ıve alpacas from group D developed a severe disease characterized by fever, abscesses in regional
lymphnodes, and in one alpaca a subcutaneous edema and sudden death 2 weeks after exposure. In addition, primary infected
alpacas had a robust antibody response against C. pseudotuberculosis cell wall antigen with significant differences with respect
the na¨ıve challenged alpacas. At necropsy, the primary infected alpacas had abscesses only in the regional or internal renal-lymph
nodes from the left or primary inoculation side of the body, with no lesions in the right challenged side. In contrast, the primary
sham inoculated alpacas had abscesses in the regional and internal lymph nodes from the right challenged side. This work showed
that a primary infection with at least 1.1×103 viable C. pseudotuberculosis induces protection against a second high dose exposure
to this bacterium. These results will be useful for further study of prevention methods to control lymphadenitis in alpacas.
© 2006 Elsevier B.V. All rights reserved.
