Importance of salmonellosis as a zoonosis
Prevalence and representative serovars in Central America and Ecuador.
Índice de Contenidos
Introduction: What is salmonellosis?
Salmonellosis is a disease caused by bacteria of the genus Salmonella that can affect humans and animals. Its importance lies on the ability of some serovars to cause zoonosis and the fact that it is one of the most frequent food-borne diseases in the world. More than 21 million cases of human salmonellosis are reported globally in one year. It can also be transmitted by contact with animals or their feces.
Etiology and symptomatology in humans
Zoonosis by Salmonella is usually caused by S. enterica serotypes Typhimurium and Enteritidis. Also, by Infantis in several parts of the world. Other serotypes are species-specific and cannot cause zoonosis.
It usually causes diarrhoea, nausea, and vomiting, which lead to dehydration. Fever occurs very often, too. It can evolve to septicaemia or focal infection, especially in immunosuppressed people.
The disease in humans does not use to cause death, although, in most cases, the costs derived from the disease are remarkably high. It can cause death in people at risk, which are children until 5 years of age, and old or immunosuppressed people.
Epidemiological situation in the world
The spread of the disease has increased in the 20th century due to a greater consumption of animal products that, together with the resistance against antibiotics, increased the concern towards this disease prevention.
Moreover, the intensification of poultry production, which includes the exports and imports of breeder birds, is of great importance for the dissemination of the disease.
Nowadays, the cases have decreased. Despite this, there are resistant and multi-resistant strains that have a great clinical importance.
Epidemiological situation in Central America
The incidence of food-borne diseases in Guatemala in 2019 was of 827,398 cases, more than the last years. Among these, there are the ones caused by Salmonella. Due to the lack of resources for laboratory analyses, the registration of cases is based on the symptoms. Most of the cases were observed in the San Marcos, Huahuetenango and Quiche departments.
The last important outbreak was reported in 2018 where 115 people got infected from eating bread with chicken.
A study in 2015 pointed out that the mains serotypes in humans in Guatemala are Typhi (41%) and Enteritidis (11%). In chicken meat, the serotypes that are more prevalent in chicken meat are Paratyphi and Heidelberg.
Another study about the prevalence of Salmonella in chicken carcasses in Guatemala mentions that less than 21.8% of the integrated production systems have Salmonella and that 16.9% of the refrigerated meat samples are contaminated (Jarquin et al., 2015).
The improvements of the notification and identification system of food-borne diseases in Costa Rica in the last years together with an increase of animal products have caused an increase of the number of cases of salmonellosis associated with the ingestion of contaminated food.
Enteritidis and S. typhimurium var. Copenhagen were the most frequently isolated serovars in humans that came from animals. Infections affected all ages (fig. 2). The most frequent serovars in animals were Enteritidis (poultry) and Enteritidis and Typhimurium (pigs).
Multi-resistant strains have been reported in the country, which complicates the treatments. These resistances have also been observed in Salmonella of animal origin (Gallinarum and Paratyphi B), for it is important to integrate the surveillance systems of human medicine, veterinary and food manipulation.
Other countries: Panama, El Salvador, Honduras
The last important outbreak in Panama caused by the ingestion of animal products contaminated with Salmonella was reported in 2018. 200 million eggs were withdrawn from the market.
In El Salvador, 117 cases were reported in San Salvador, San Miguel, La Libertad and Chalatenango between January and February of 2019, which represents a 58% increase compared to the same period of the past year. Differently from other countries, most of the salmonellosis cases in El Salvador are related to the lack of hygiene or to water contaminated with dejections, instead of the ingestion of animal products.
In Honduras, in 2019, more than 3000 layers were sacrificed due to a typhoid fever outbreak caused by Salmonella Gallinarum.
Salmonellosis is, therefore, a prevalent disease in these countries. The increase, each year, of zoonotic outbreaks shows that there is a need to implement effective measures in the farms, slaughterhouses, and product manipulation areas in order to prevent the disease.
Epidemiological situation in Ecuador
In Ecuador, in 2019, 956 cases of human salmonellosis were reported. Guayas and Morona de Santiago were the most affected areas (Gobierno de Ecuador, Ministerio de Salud Pública, Subsecretaria de vifitancia de la salud pública, 2019).
It is one of the most common pathologies among the food-borne diseases, despite cases decreased from 3331 Salmonella infections in 2015 to 956 in 2019 thanks to the awareness campaign and analyses conducted by the Public Health Ministry.
Regarding the specific analyses of animals and animal products, in Pichincha 2015, 8.5% of the chicken carcasses were contaminated with Salmonella, and 3.6% of the chicks had zoonotic Salmonella serovars (Enteritidis, Typhimurium and Infantis) (Melo, 2015).
The most prevalent serotype in Salmonella in contaminated meat is Infantis, capable of causing zoonosis (Fig. 3).
Foods of higher risk
Epidemiologically, salmonellosis outbreaks are usually associated to contaminated poultry meat or subproducts, particularly food with raw eggs, such as mayonnaise. This is because Salmonella can colonize the ovaries of infected layers, and the bacteria ends up contaminating the eggs. Eggs can also get Salmonella when the eggshell contacts contaminated feces.
Usually, initial contamination in the egg is not sufficient to cause disease in humans, but, if eggs are kept for a long period in warm temperatures, Salmonella can start to replicate and reach infective doses.
Products from other species can also be a source of infection (pig, beef), since meat can be contaminated during manipulation.
The measures to prevent zoonosis by Salmonella include a good surface and hand hygiene in any step of the meat and animal product manipulation chain, from the farm until the consumers’ homes.
Cross-contamination should be avoided in the slaughter plant and consumers should cook meat properly and store animal products under refrigeration.
Prevention in the farms should focus on:
- The reduction of the pathogen prevalence through continuous control of its presence in animals. Locate animals that show signs of disease and eliminate them (or separate them from the healthy ones), particularly breeders.
- In farms with breeder hens, eliminate the ones with small crest and green feces because they can transmit Salmonella to the eggs and their productive performance is below the standard.
Infected one-day-old chicks show a triad of lesions: enlarged green yolk, green gaseous ceca, and green liver. Green content and lesions in the corneal layer of the gizzard may be observed, too.
- The administration of natural biocides that eliminate the bacteria from the digestive tract and feces, such as Alquermold natural
Alquermold Natural as a preventive tool
It is a natural product that combines the synergistic action of the cimenol ring, from plant extracts, and the citric acid. It has broad-spectrum bactericidal and fungicidal activities and its addition to the feed and/or the drinking water can reduce the presence of bacteria, such as Salmonella, in the gut, so that it decreases the risk of zoonosis.
Because it is a natural product, it does not leave residues in the meat nor in other animal products and does not require a withdrawal period. In addition, differently from antibiotics, it does not cause the development of resistances and is available for conventional and organic production.
Apart from eliminating Salmonella, Alquermold Natural is effective against other microorganisms such as E. coli or Clostridium perfringens and has several advantages against other products with the same objective:
- Non-corrosive, safe for animals and humans.
- Long-lasting efficacy (at least 6 months).
- Versatile administration: in the feed, to eliminate bacteria present in the substratum and control pathogenic flora in the gut; and in drinking water for a faster effect in case animals show signs of infection.
Salmonellosis is a disease of importance in animals and humans. In the latter, the zoonotic capacity of some serotypes of this bacterium are concerning and determines the importance of hygiene and control measures to decrease the presence of this pathogen in farms, slaughter plants and houses.
Food-born cases of salmonellosis in Central America markedly increased in 2019 compared to the past year. This shows the need to implement measures to reduce the prevalence of this pathogen.
In Ecuador, the most important zoonotic serotypes are Infantis and Typhimurium, and the most frequent source of infection, apart from the direct contact with animals, is the ingestion of contaminated poultry meat or related products, such as eggs.
Despite cases in the country have decreased in the last 5 years, it is important to apply measures to reduce the prevalence of this pathogen in the farm, to prevent carcass contamination.
Among such measures is the use of Alquermold Natural, a biocide that is highly effective against Salmonella and can eliminate it from feed and reduce its presence in the digestive tract.
Alquermold Natural is a product patented by Biovet, S.A. that is available in premix and liquid formulations, to be added in the feed, the drinking water, or sprayed on grain. It preserved feed and raw materials up to six months and controls the balance of the digestive microbiota.
Gobierno de Ecuador, Ministerio de Salud Pública, Subsecretaria de vifitancia de la salud pública, dirección nacional de vigilancia epidemilógica. (2019). ENFERMEDADESTRANSMITIDAS POR AGUA Y ALIMENTOS. INFECCIONES DEBIDAS ASalmonella.
Jarquin, C., Alvarez, D., Morales, O., Morales, A. J., López, B., Donado, P., … Alali, W. Q. (2015). Salmonella on raw poultry in retail markets in Guatemala: Levels, antibiotic susceptibility, and serovar distribution. Journal of Food Protection, 78(9), 1642–1650. https://doi.org/10.4315/0362-028X.JFP-15-117
Mejia, L., Vela, G., & Zapata, S. (2020). High Occurrence of Multiresistant Salmonella, (August). https://doi.org/10.1089/fpd.2020.2808
Melo, D. (2015). Identificación de Salmonella enterica de interés zoonósico serotipos Enteritidis, Typhimurium e Infantis en un pollo bebé de un día de edad en sistema productivo de pollo de engorde en la provincia de Pichincha. Titulación – Medicina Veterinaria y Zootecnia, 10. Retrieved from http://www.dspace.uce.edu.ec/handle/25000/6912
MV. Júlia Pié Orpí
Veterinary Technical support to the area of Latin America at Biovet S.A. Laboratories Official Veterinary Services (SVO) in poultry slaughterhouse