Avian Influenza: global outbreak requires review of processes
27/04/2022
Colibacillosis: Dr. Terezinha Knöbl answers main issues regarding the topic (Part 2)
16/05/2022
Avian colibacillosis is a disease caused by [avian] pathogenic Escherichia coli strains (the so-called APECs), which causes increase of feed conversion and medication costs, lower weight gain, lack of flock uniformity, high mortality and morbidity in birds.
Prof. Dr. Terezinha Knöbl
That is, it is an economically devastating disease, a cause of great concern for the production of broilers — and furthermore beset by uncertainties. For example: what factors led to the recent advent (in the last 12 months) of problems with APEC in several Brazilian companies?
The answer to this question is not simple, nor to others related to this very current challenge of Brazil’s poultry industry. Precisely for this reason, we invited an expert on the subject to talk about colibacillosis on our blog.
Prof. Dr. Terezinha Knöbl, who works at the Avian Medicine Laboratory of the Pathology Department of the Faculty of Veterinary Medicine and Animal Science at the University of São Paulo (USP) and has extensive experience in avian diseases, Enterobacteriaceae infections, colibacillosis and bacterial virulence factors, answered the main issues about Escherichia coli.
In Part 1 of this content, she talks about the problems caused by APEC in birds, the possible reasons for the recent cases and evaluates the key measures to control and prevent the disease. Check them out!
Interview with Dr. Terezinha Knöbl
1. Biocamp – What are the main factors that led to the recent emergence, in the last 12 months, of problems with APEC in several Brazilian companies?
Dra. Terezinha Knöbl – It is difficult to associate the re-emergence of colibacillosis to a single cause, because the scenario is quite variable from one farm to another. However, among the main points that may be related to this epidemiological change, we can mention:
1 The emergence of pandemic strains belonging to phylogroup G, with special emphasis on ST117.
This strain caused economic losses in some European countries: it is considered quite virulent for birds and acts as a primary agent. This ST (sequence type) 117 has already been reported in Brazil. However, E. coli characterization studies by MLST (Multilocus sequence typing) or WGS (whole-genome sequencing) in Brazil – types of genome sequencing – are still scarce, either for diagnosis or monitoring of pandemic STs.
2 Restriction of the use of performance-enhancing additives.
The experience of some European countries has shown that the withdrawal of growth promoters is a critical moment for the emergence of some bacterial diseases, but the trend in a couple of years is for the situation to return to normal pattern.
3 Increase of use of therapeutic antimicrobial agents, including the use of disinfectant directly on the birds.
The use of formaldehyde, quaternary ammonium or glutaraldehyde based disinfectants on birds can cause irritation, inflammation and metaplasia of the respiratory epithelium. Extensive loss of epithelial cilia and accumulation of mucus can favor colonization of the trachea and promote the development of respiratory diseases.
4 Changes in the weather pattern of some regions, with a drier and warmer climate and an increase in thermal amplitude.
Heat stress can change the birds’ immune response capacity.
5 Greater challenge of immunosuppressive viral diseases and emergence of variant strains of respiratory viruses.
There is still no well-established correlation between cases of colibacillosis and infectious anemia and/or infectious bronchitis in chickens (variant virus). However, it is possible that these infections are related to opportunistic E. coli infection conditions.
6 Market heating during the pandemic period, with reduction of chick supply.
This lack of birds in the market favors the incubation and breeding of weak birds that serve as a source of infection. An important point in this scenario is the reduction of the sanitary vacuum period to increase productivity. Increase of productivity also increases health risks.
2. Biocamp – And what are the problems caused by APECs in birds? Do they cause enteric diseases?
Dra. Terezinha Knöbl – No. APEC is a pathogen that belongs to the extra-intestinal pathogenic Escherichia coli (ExPEC) pathotype. This means that the virulence repertoire is associated with systemic infections. The main condition is respiratory disease (aerossaculitis) with subsequent colonization of the liver and heart. It may be implicated in cases of sepsis or other extra-intestinal conditions such as omphalitis in embryos and chicks in the first week of age or as oophoritis and salpingitis in adult egg-laying birds.
Other diseases can be caused by commensal strains or strains with less virulence potential, as usually occurs in cellulite processes. In this disease, microbiota bacteria are inoculated into the subcutaneous tissue and cause a local inflammatory process. Although some cellulite isolates are toxin producers, in general they do not have the same virulence repertoire as an APEC.
The same occurs in the arthritis of broiler chickens. Bacteria with lower survival capacity to the host’s inhibitory serum factors usually migrate to joints to escape from the action of antibodies. Less virulent bacteria can also cause disease when there is a co-infection. As an example, it is possible to mention the swollen head syndrome, due to the association of E. coli and pneumovirus. Pneumovirus causes rhinitis, with increase of mucus secretion. This mucus serves as a substrate for the multiplication of E. coli strains.
Pathotypes related to diarrhea problems are grouped into a group called diarrheagenic E. coli (DAEC), which is subdivided into 6 distinct pathotypes, according to the virulence markers found, and which determine the mechanism by which diarrhea occurs. These pathotypes are most frequently identified in mammals, although there are occasional reports of EPEC (enteropathogenic Escherichia coli) and ETEC (enterotoxigenic Escherichia coli) infection in ostriches, parrots, turkeys and other species of birds. The occurrence of these diarrheagenic pathotypes in chickens is quite rare.
However, it is important to consider dysbiosis processes, in which there is a change in the proportion of different bacterial genera in the microbiota. In general, in dysbiosis processes, there is a reduction of probiotic bacteria and proliferation of enterobacteria and clostridia. This intestinal modulation can result in diarrhea, with an increase in Escherichia coli count. In this case, the problem is quantitative and not related to the pathogenicity of virulent strains.
3. Biocamp – What are the main agents that predispose complicated E. coli respiratory problems in birds?
Dra. Terezinha Knöbl – The main ones would be mycoplasmas and avian infectious bronchitis virus (coronavirus), as these agents cause ciliostasis and loss of the tracheal epithelial cilia, favoring the production of mucus and colonization of the trachea. In the same way, physical and chemical agents can also act in the predisposition of avian colibacillosis. In this category we can mention dust, ammonia and disinfectants. Chronic exposure to these agents promotes epithelial metaplasia, with loss of tracheal cilia.
4. Biocamp – Under normal conditions, there are 85% avian fecal E. coli and 15% APEC. What is the risk of this ratio getting narrower?
Dra. Terezinha Knöbl – The risk of dysbiosis in these conditions exists. There is also a risk of mobilization of mobile genetic elements between virulent and commensal strains. The APECs present in the microbiota will not be directly involved in enteric conditions if there is no dysbiosis, but they will be eliminated via the faecal route and can be transmitted horizontally. Environmental contamination can favor colonization of the respiratory tract, implying a risk of occurrence of colibacillosis. This risk will be even higher if APEC belongs to the ST117 and ST95 strains.
5. Biocamp – Is the constant use of antibiotics as growth promoters related to APECs or is there just the selection of resistant strains?
Dra. Terezinha Knöbl – Some strains can be selected and others no, as this selection depends on bacterial fitness. Some strains have evolved to accumulate mobile genetic elements that allocate resistance and virulence genes simultaneously. An important example is the ExPEC ST131 strain, capable of causing sepsis, which is usually multidrug-resistant and has an extended resistance spectrum to beta-lactam agents. The selection pressure imposed by the exacerbated use of cephalosporins, phenicols, quinolones and fosfomycin has selected hybrid virulence and resistance plasmid carrying APECs, as described by Cunha et al. (2017). Two decades ago, APECs were sensitive to antibiotics. However, most of the strains currently characterized are multidrug-resistant and ESBL (Extended Spectrum Beta-lactamases) – enzymes that confer resistance to most beta-lactam antibiotics.
6. Biocamp – Modulating the intestinal microbiota of birds through the constant use of probiotics of multiple lactic strains, from birth to end of life, can be an effective and viable alternative to the control of APEC in the poultry production chain (that is, from the grandparent chickens and broiler breeders)?
Dra. Terezinha Knöbl – Yes. The maintenance of a healthy enteric microbiota is one of the key strategies for controlling pathogens.
7. Biocamp – Does the use of autogenous vaccines in broiler breeders offer protection against production losses and/or passive protection to the progeny?
Dra. Terezinha Knöbl – Yes. The use of vaccines in broiler breeders is a strategy to reduce production losses. However, the protection is homologous and the effects are not immediate. The reduction of the circulation of a strain on a farm usually occurs after a few years of using the vaccine.
8. Biocamp – Considering the reduction of salpingitis and oophoritis in broiler breeders, the reduction of omphalitis and early mortality in one-day old chicks, the reduction of septic conditions after 21 days of age and the reduction of sacrifices due to Chronic Respiratory Disease, what is the ideal moment to use live and/or inactivated E. coli avian vaccines (including autovaccines)?
Dra. Terezinha Knöbl – The use of live and inactivated vaccines is an important strategy to control all these mentioned situations. In general, they are implemented when there is a report of excessive condemnation in slaughterhouses due to Chronic Respiratory Disease. The use must follow the manufacturers’ recommendations and the same principles of other bacterial vaccines: the use of bacterin in broiler breeders before production, aiming at the protection of the progeny, and the use of live vaccines in young birds.
However, it is important to highlight that the reduction of the economic impact occurs in the medium term and that it will only be effective if the disease is caused by a strain of the same serogroup of the disease. Therefore, it is necessary to characterize the agent or use an autovaccine. There is no protection against serogroups other than those that comprise the vaccine.
In addition, the vaccine is a strategy that does not replace good poultry production practices. The results will be unsatisfactory when the disease is the result of secondary infection, in cases of immunosuppression, management or nutritional failures, health problems and co-infection or environmental and biosecurity failures.
9. Biocamp – What are the other measures and/or indispensable tools in the production process for the control of colibacillosis?
Dra. Terezinha Knöbl – It is essential that there is an adequate sanitary empty period. The literature points out that an empty period of less than 15 days is one of the main risk factors for colibacillosis. Likewise, the management of poultry litter is a point of great importance.
Good poultry production practices must be adopted. It is necessary to have a biosecurity program, with water quality monitoring, control of immunosuppressive and respiratory diseases, especially mycoplasmosis and IBV (Avian Infectious Bronchitis Virus).
As some invertebrate hosts can act as mechanical vectors of APEC, among which we highlight the mealworms, the farm must have control of these insects.
Farms and hatcheries should also monitor the presence and frequency of high-risk strains such as ST117 and ST95 strains.
The use of antimicrobials must be rational and prudent in poultry production, in order to reduce the selection of virulent/resistant strains, and the use of probiotics and organic acids can favor the development of a healthy and competitive microbiota, excluding pathogenic strains.
10. Biocamp – Considering biosecurity, use of probiotics and antibiotics in broiler breeders and progenies, and cleaning of environments, which measures represent the greatest impact on APEC control?
Dra. Terezinha Knöbl – Each company has its particularities, but I believe that biosecurity measures and the use of probiotics in broiler breeders and progeny are the most relevant. This is if biosecurity includes an adequate sanitary empty period and the use of probiotics is associated with a reduction in the use of antimicrobial agents, to avoid the selection of resistant and virulent strains.
Now the use of antibiotics in broiler breeders and progeny should only be carried out in very specific situations and under the supervision of a veterinarian. It is necessary to know the agent’s resistance profile and consider that in vitro test results are not guarantees of in vivo success. I am not in favor of prophylactic and metaphylactic treatment in the production chain as a permanent control strategy. I understand that this approach should be limited to situations of greatest need, in specific cases.
Regarding the hygiene of environments, although it is favorable, sometimes this factor behaves inversely: the cleaner and more disinfected an environment, the greater the chance of reduction of commensals and survival of pathogens. Excessive cleaning and disinfection can result in the selection of other pathogens, such as Pseudomonas aeruginosa in hatcheries.
11. Biocamp – Which category of probiotics do you think is more effective for the control of APEC: undefined culture, defined culture or both?
Dra. Terezinha Knöbl – Both can be used successfully. But it is necessary to highlight the importance of a diverse microbiota. There are not many comparative studies using APEC strains. However, based on evidences from works with other Enterobacteriaceae, the use of an undefined culture seems to be quite promising.
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The interview with Prof. Dr. Terezinha Knöbl comes to bring further clarity about colibacillosis. Keep track of Biocamp’s blog. Shortly we will make available Part 2 of this conversation!
