Paratyphoid Salmonella are organisms with a wide distribution in the environment and are difficult to control. Reducing infection levels requires the active participation of all links in the poultry production chain.
Lecture by Miguel Ruano, University of Delaware, USA at the XXIV Latin American Congress of Poultry, Guayaquil, Ecuador, September 2015.
Infections of birds with germs of the genus Salmonella cover a wide variety of diseases, both acute and chronic, which can be divided into two main groups:
1. Infections of a specific type, originated by immobile bacteria, highly pathogenic for birds but without major zoonotic implications.
– S. gallinarum, which causes avian typhois
– S. pullorum, which causes pulorosis
2. Non-specific infections, caused by a large number of mobile or paratyphoid Salmonella that are widely distributed in nature. In general, flocks of birds infected with paratyphoid Salmonella remain asymptomatic, but they can become permanent sources of infection with serious public health implications.
Most common paratyphoid salmonella in birds
The paratyphoid Salmonella are microorganisms of wide occurrence in farm and wild animals, so it is very difficult, if not impossible, to maintain commercial batches of poultry for the production of meat and eggs free of this type of infection.
In the United States, S. gallinarum and S. pullorum (group D) were eradicated from commercial bird flocks in the mid-1960s, but gradually the emergence of S. enteritidis (group D) began to be experienced, which initially was associated as a primary rodent pathogen.
It has been suggested that as the immunological status against S. gallinarum and S. pullorum began to decline in flocks free of these infections, S. enteritidis began to establish its ecological niche in new commercial flocks since S. gallinarum exerts a competitive exclusion against S. enteritidis.
By the mid-1980s, S. enteritidis had spread worldwide at pandemic levels to become a very significant problem of foodborne infections in humans, and in the United States, the National Poultry Improvement Plan (NPIP) began to take action to work with industry and decrease infection levels in commercial poultry flocks.
But while a significant reduction in the levels of infection by S. enteritidis has been achieved, due to a combined program of vaccination, biosafety, and continuous laboratory evaluation, which may be associated with an increase in the levels of immunity against S. enteritidis, Due to exposure or vaccination of birds, infection rates with S. Typhimurium, S. Heidelberg (group B) and S. Kentucky (group C) have started to increase significantly.
In Latin America, we really do not have more documented information that speaks of the epidemiological status of each country. However, through personal communications, we know that S. gallinarum still remains endemic in different Latin American countries from north to south. There are also sporadic reports of S. enteritidis, S. Typhimurium, and other paratyphoid Salmonella.
Public health implications
According to statistics from the United States Center for Disease Control (CDC), 1.2 million cases of paratyphoid Salmonella infections occur annually in humans, with approximately 450 deaths, which represents the highest percentage compared to other poisonings. food of bacterial origin (E. coli, Campylobacter, Listeria, Clostridium, etc).
More than 70% of paratyphoid Salmonella infections in humans have been attributed to the consumption of contaminated chickens, turkeys or eggs, or by direct contact with infected birds or their contaminated products. S. Typhimurium and S. enteritidis are the serotypes that have been most frequently recovered from sick people.
In recent years, both in Europe and the United States, there is concern about the discovery of new isolates of S. Typhimurium with multiple resistance to antibiotics, such as the phage types S. Typhimurium DT104, which in Europe has caused epidemics in different species of domestic animals for food production; S. Typhimurium DT193 and monophasic variants of S. Typhimurium.
Since the implementation of the Harmful Substance Analysis and Critical Point Control (HACCP) program at the processing plant level in 1996, the number of cases of bacterial food poisoning attributed to Campylobacter, E. coli O157: H7 and L. monocytogenes has decreased.
Unfortunately, the incidence of salmonellosis in humans has increased, despite the progress made by the poultry industry to reduce the incidence of salmonella in processed birds from 20% in 1995 to 7.5% in 2009.
Following recent incidents of food poisoning associated with S. enteritidis-contaminated eggs in multiple states in the United States, there is a renewed urgency on the part of official regulatory and control agencies to persuade the poultry industry to redouble efforts to reduce salmonella levels in poultry products.
In 2009, the Food and Drug Administration (FDA) implemented a regulation to reduce the prevalence of S. Typhimurium and S. enteritidis in commercial layer flocks. Likewise, the Department of Agriculture (USDA-FSIS) proposed stricter standards for the reduction of Salmonella and Campylobacter in poultry processed at the slaughterhouse level.
Salmonella control strategies during production
Control measures have focused on contemplating a comprehensive plan that covers from farm to fork.
The first step begins with the production of “clean” breeders, which do not actively transmit S. enteritidis, S. Typhimurium, S. Heidelberg, etc., through the fertile egg. The use of live and/or inactivated vaccines, accompanied by practical biosafety procedures and evaluation of the infection levels of the flocks during rearing, have resulted in significant reductions in infection.
Unfortunately, paratyphoid Salmonella vaccines, whether live-attenuated or inactivated, do not prevent infection at high levels of challenge, nor do they provide satisfactory cross-protection against all serotypes.
Then, at the incubator level, good sanitary and biosafety practices should be established to avoid amplifying any possible initial contamination. The intervention with disinfectants in hatchers has given favorable results.
At the farm level, whether for breeders, commercial layers, or broilers, a comprehensive program with the best production practices (BMPs) must be established, executed, and constantly evaluated, among which we can mention:
- Cleaning and disinfection of the sheds or rearing houses
- Sanitization of drinking water
- Permanent rodent control
- Important biosecurity measures
- Contamination-free food
- Bedding quality (wet beds tend to generate increased levels of ammonia and pathogens)
- Currently, the use of prebiotics and probiotics has attracted better attention
- Documentation of program successes and failures under scrutiny
Salmonella control strategies in the processing plant
The first step to optimize the sanitary processing of the birds is the establishment of an adequate and consistent program for the withdrawal of feed and emptying of the intestinal tract, for the collection and transport of the animals, and appropriate waiting accommodation in the processing plants, without causing a stressful effect on animals.
Cleaning and disinfection of cages and transport equipment should not be neglected either.
Interventions during the process include:
1. Minimize cross-contamination in scalding tank and plucking
2. Minimize fecal contamination during evisceration
3. Establish appropriate strategies for microbiological control in chiller tanks.
Salmonella control strategies during the marketing
1. Proper handling of the final product without breaking the cold chain or causing cross-contamination with other food products in the warehouses for storage and sale.
2. Sale of products within the expiration dates
Advising the consumer to practice basic hygiene measures when handling unprocessed poultry products, with the same precautions established for handling other unprocessed meat products, could become the most effective tool to reduce infection rates.
Recommendations that should be included in a consumer education program include more frequent handwashing with soap and water, the use of disposable gloves, cleaning and disinfecting the utensils and preparation tables of the meat, avoid contact of uncooked meat products with other foods, and above all, ensure that cooking these foods reaches the time and temperature required to destroy all kinds of potential pathogens.
Summary of Salmonella in Birds
Since part typical salmonellae are organisms with a wide distribution in the environment and are difficult to control. It is very difficult to achieve a prevalence of zero (“zero tolerance”) in commercial flocks of birds, despite the best efforts and advances made by the industry.
To reduce the levels of infection in the final consumer, the active participation of all the links in the chain will always be required, through a global understanding of the complicated system of production, marketing, preparation, and proper use of food.
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