Lawsonia intracellularis

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Shedding of lawsonia intracellularis by fattening pigs in two production systems in Yucatan, Mexico.

Introduction

Porcine proliferative enteropathy (PPE) is a disease caused by Lawsonia intracellularis, characterized by anorexia, diarrhea, listlessness and visible lesions at necropsy patonogmónicas [13].This disease affects farms with or without modern production systems, pigs from weaningto market and replacement females.This infection is distributed worldwide, with prevalence of farm 15 to 35% in animals from 15 to 20% [5]. EPP causes economic losses to the swine industry due to mortality, increased feed intake and increased days to market [24].

To establish control programs for this disease, information is needed on the mechanisms of transmission and survival ofbacteria inthe environment, the effectiveness (in-vitro and in vivo)of antibiotics available, and patterns of elimination of bacteria[12]. In Mexico, few published studies on this subject are of across-section, which have certain limitations for the distribution of the infection. Buenfil Rodriguez et al. [18] reported in Yucatan,Mexico, the presence of L. intracellularis, using the test of the chainreaction of polymerase.
The objective of this study was to determine the prevalence and incidence of L intracellularis in fattening pigs in two production systems in Yucatan, Mexico.

Materials and methods

The research was conducted in October 2000 to March 2001, two farms in the state of Yucatan, Mexico. The climate is humidtropical region with 70% of the rainfall occurring in summer. One of thefarms was multiple sites and the other from a site (continuous flow). Both farms had a history of EPP.
The farm site was located in an area of ​​high pig density in the municipality of Conkal, Yucatan, Mexico, with a number of 300 sows and continuous flow production. The stages of lactation (1-3 weeks), grower (4-10 weeks) and end (11-22 weeks) were performed on the same farm. Therefore, thecleaning and disinfection of cages and kennels on this farm was done partially. The animals received pelleted feed (without antibiotics or growth promoters) provided manually.

The multi-site farm consisted of three geographically separate sites all in all out system; located in an area of ​​low pig density (0.5 farms per km2) Site 1 included the breeding herd with three modules located in threegeographical areas, each with an average of 3,000 sows and an average of 132.6 births per week. Weaning was performed at 14 days old. At site 2 were weaned pigs and comprised 9 modules (always a vacuum for cleaning and disinfection), with an average population of approximately 19,000 pigs. 3 The site included the area of ​​fattening with 13geographically separated modules, with an average of 2365 pigsper week. The pigs were fed pelleted feed with automatic feeders.

We performed a longitudinal study, using 59 pigs on each farm for the presence of L. intracellularis using the test chain reaction (PCR). The number of animals per farm was obtained considering an incidence of non-exposed pigs 10% confidence level of 95% test power of 85% and a relative risk of 3.3, using the formula providedby Trusfield [21]. At each farm, 12 sows were selected negative, choosing 5 pigs of the first 11 pigs and 4of the latter. The piglets were identified individually and were selected using a random numbers table. All piglets were negative PCR test, except for a pig farm site, which was excluded from the study. The piglets were mixed with their peers and were housed in cages at weaning with capacity of16 animals per cage.

The pigs were monitored every 14 days, from week 1 to 21 of age. During each sampling, 1 g of stool was collected directly from the rectum of pigs using sterile swabs. Stool samples were stored in polyethylene bags, were identified and stored at 4 ° C. The samples were frozen at -20 ° C until used for detecting the presence of L. intracellularis. The bacterium was...
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