The Rational for Auto Vaccines in Poultry Colibacillosis
* Luís Martins Department Of Veterinary Medicine, School Of Sciences And Technology, University Of Évora, Núcleo Da Mitra, 7000-093 Évora, Portugal
*Corresponding Author: Luís Martins
Department Of Veterinary Medicine, School Of Sciences And Technology, University Of Évora, Núcleo Da Mitra, 7000-093 Évora, Portugal Email:email@example.com
Published on: 2018-10-24
Colibacillosis is a rather important economic problem for poultry production, associated to Avian Pathogenic Escherichia coli (APEC) strains, which may cause several extraintestinal pathologies, such as airsacculitis and cellulitis in broiler chickens, and salpingitis and peritonitis in broiler breeders, leading to septicemic mortality. Control of morbidity and mortality in colibacillosis outbreakes may be performed with antibiotics and/or by vaccination. The use of antibiotics is frequently ineffective as Escherichia coli (E. coli) is considered the largest reservoir of antimicrobial resistance, characteristic that may even transmit to other bacteria, turning the situation into a serious problem of public health. Vaccination may be the alternative solution but as many different strains arise, flock-specific autovaccines seem to be needed under several possible protocols, with live attenuated and/or inactivated vaccines from different strains that should be identified and characterized according to their virulence factors, within different flocks.
Biosecurity of poultry farms stands as fundamental domain in order to allow the control of major infectious agents, which is fundamental for farm profitability and public health. Despite all the involved technological advances and extraordinary improvements at the good hygiene practices level, occurrence of infections, especially colibacillosis, is still a real problem. The infection is caused by APEC strains, responsible for considerable economic losses in the poultry industry [1, 2]. Recent studies even indicate an increase in the incidence of new cases in Europe . Physiologically, E. coli colonizes the digestive tract of several animal species, including birds, establishing a commensal relationship with the host. In this situation E. coli strains are denominated Avian Faecal Escherichia coli (AFEC). However, APEC strains hold different genetic profile from AFEC, allowing them to cause disease in infected individuals, resisting the host immune system through several mechanisms. Escherichia coli contain a high number of antigens: i) somatic (O); ii) flagellar (H); iii) capsular (K); iv) fimbrial (F) and v) toxins . Between the 180 O antigens many serotypes have been associated with avian colibacillosis, but in the field, serotypes isolated from affected birds were significantly different from those isolated from healthy ones. Intestinal infection from healthy birds with strains from sick birds has shown to be frequent, but in asymptomatic chickens, 10-15% of intestinal coliforms may belong to potentially pathogenic serotypes. In the environment, the bacteria may persist for long periods, particularly in dry and dusty surfaces, and environmental isolates consist of a different population from pathogenic isolates. Contaminated food may be a mean of transportation of new E. coli serotypes from a flock to another and contaminated water is also a possible source of fecal-oral transmission .