On occurrence of some avian bacterial diseases and biosafety provision

INTRODUCTION

Commercial poultry farming is known to remain the leading branch of agricultural production, providing the population with valuable dietary food. Despite the fact that veterinary specialists pay special attention to the prevention and control of zooanthroponous avian diseases, as well as ensuring veterinary and sanitary safety of poultry products, infectious diseases are still detected in poultry farms of the Russian Federation. Researchers agree that avian infectious diseases pose a potential risk of mass distribution in the population all over the country’s territory and result in decreased weight gains and egg yield, livestock reduction, increased microbial contamination and deterioration of poultry product quality. According to some authors, infectious diseases such as Newcastle disease, avian influenza, Marek’s disease, Gumboro disease, avian infectious bronchitis, avian infectious laryngotracheitis, colibacillosis, salmonellosis, pasteurellosis and others take a significant place in the formation of the nosological profile of avian infectious pathology and deteriorate the animal health situation in commercial poultry industry. Many foodborne pathogens are widespread in nature, may persist in the environment for a long time and remain facultative parasites for warm-blooded, including food-producing animals. According to veterinary reports, bacterial diseases (colibacillosis, salmonellosis, pasteurellosis, etc.) play a significant role in poultry disease occurrence and incidence and develop when maintenance and feeding conditions are incompliant and the overall animal body resistance is decreased; they can also be secondary infections or a result of the virus latently circulating in poultry body, which exacerbates the development of infectious process. Such pathogenic bacteria as Salmonella, Listeria, pathogenic Escherichia coli strains and other microorganisms occupying a specific place among pathogens common to animals (including birds) and humans and being risk factors for occurrence of foodborne toxicoinfections, still present the greatest danger to poultry farms and poultry processing establishments [1][2][3][4][5][6][7][8][9][10].

According to the statistics of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing (Rospotrebnadzor), salmonellosis is one of the most common zoonotic bacterial infections transmitted through food (predominantly through poultry products for most pathogens) and the main cause of group morbidity among the population. For instance, in 2022 the Rospotrebnadzor registered 27 outbreaks of foodborne salmonellosis in 22 Subjects of the Russian Federation, whereas 1,204 people were affected, and 36 major salmonellosis outbreaks were recorded within 11 months of 2023. Level of infection in people due to consumption of substandard products (meat, eggs) varies within significant limits.

Colibacillosis (escherichiosis, colisepticemia, dysentery) detected in birds is an acute infectious disease caused by enteropathogenic Escherichia coli, which occurs in the form of septicemia and is characterized by diarrhea. Escherichia coli originally called Bacterium coli was first identified in 1885 by the Austrian scientist Theodor Escherich after whom it received its name. Escherichia coli are small, polymorphic, gram-negative rod-shaped bacteria with rounded ends, they have no spores, are well cultivated on conventional nutrient media and belong to facultative anaerobes. Diseased and convalescent birds are the source of infection, and the pathogen can also be transmitted by wild birds and rodents. The routes of infection can be aerogenic, alimentary and transovarial. According to the researchers, chickens, turkeys, ducklings and goslings up to 90 days of age are most susceptible to the infection, adult birds rarely get diseased, humans may be susceptible. The pathogen persists in the environment for up to 4 months, dies within 1–2 minutes when heated to 100 °C, it is sensitive to conventional disinfectants. Clear 2% active chlorine solution, 5% chloraminum B solution, 3% caustic soda hot (45–50 °C) solution, 2% formaldehyde solution, 20% suspension of freshly slaked lime (by double whitewashing with an interval of one hour) are used. The ante-mortem diagnostic examination of young birds reveals depression, cyanosis of the head skin, dyspnea, wheezing, diarrhea, fever, intoxication signs. During post-mortem examination cyanosis of muscle tissue is observed, the liver is enlarged, there are fibrin films on the liver surface, multiple small spot hemorrhages are found on the serous membranes of internal organs, and the lungs are hyperemic. Peritonitis and enteritis are recorded in adult birds [1][11][12][13][14][15][16]. It should be noted that the final diagnosis is confirmed by laboratory tests conducted in accordance with regulatory documents.

Young poultry and wild birds are most susceptible to Salmonella infection, resulting in salmonellosis (paratyphoid) – an infectious disease that occurs mainly in the gastrointestinal form and, less often, may be systemic. Salmonella agents belong to the Enterobacteriaceae family of intestinal bacteria, the Salmonella genus. Salmonellas are morphologically rod-shaped bacilli with rounded ends that do not form spores and capsules, are well stained with aniline dyes, gram-negative, cultured on conventional nutrient media, classified as aerobic or facultative anaerobes. The pathogen is quite resistant to environmental factors and sensitive to conventional disinfectants. Thus, bacteria can survive in soil within 1–9 months, in frozen meat – within 6–13 months, in eggs – within up to 13 months, in egg powder – within up to 9 months; S. enteritidis, S. typhimurium, S. gallinarum, S. pullorum, S. infantis are the major species in the etiological structure of avian salmonellosis. Diseased and convalescent birds can be a reservoir of the pathogen, that is, they can be Salmonella carriers for a long time, which is especially dangerous as this is a latent source of infection. The disease can be acute, subacute, chronic and sometimes asymptomatic (in adult chickens, ducks and geese). Diseased birds demonstrate lethargy, inappetite, weight loss, conjunctivitis, rhinitis, diarrhea, arthritis, dyspnea, comb and wattle cyanosis; ducks and geese demonstrate swelling of the head. During post-mortem examination enlarged liver, small necrotic foci in the spleen and kidneys are found in adult birds, inflammations of ovaries, oviduct, and cloaca are frequently observed as well. In chicks the serous membrane of the intestine is red, the mucous membranes of the digestive tract are catarrhally inflamed, there are streaky hemorrhages in places, the liver is enlarged, with fibrinous depositions on the capsule and multiple small necrotic foci. Liver degeneration is noted in goslings, whereas in ducklings the liver is enlarged and has many small necrotic foci [2][5][13][17][18][19]. Salmonella bacteria cause food toxicoinfections in humans; poultry meat, edible eggs and other poultry products are the pathogen transmission factors.

The Department of Microbiology of the All-Russia Scientific Research Veterinary Institute of Poultry Science (A. N. Borisenkova, T. N. Rozhdestvenskaya, O. B. Novikova) has developed a control system for prevention of bacterial diseases in commercial poultry farming, which establishes the main technological links and includes 11 main aspects: diagnostic monitoring (serological tests, microbiological tests of faeces samples, cloaca smears); microbiological monitoring during chicken hatching and rearing; epizootological monitoring of the production technological cycle; antibiotic therapy; probiotic-based prevention, disinsection, desacarization; deratization; specific prevention; HACCP-based analysis of critical control points and risk management (microbiological control of feed, technological facilities, product yield) [2][20][21].

Thus, colibacillosis and salmonellosis are the most common avian bacterial diseases currently posing a risk to poultry farming and, in particular, to food product consumers. Therefore, the analysis of colibacillosis and salmonellosis occurrence in poultry farms in the country, as well as the results of poultry meat and poultry product laboratory tests are essential for development of the veterinary and sanitary service activities to ensure poultry disease freedom and biosafety, and that determined the direction of our research.

MATERIALS AND METHODS

Based on statistical data of the Ministry of Agriculture of the Russian Federation, a retrospective analysis of the colibacillosis and salmonellosis occurrence in poultry farms in the country in 2018–2022 was carried out, taking into account the detected outbreaks and the number of infected birds for each disease. The results of laboratory tests of Salmonella contamination of poultry meat and poultry products in 2018–2020 are analyzed.

RESULTS AND DISCUSSION

It was established that in 2018–2022, 827,442 poultry in 190 outbreak areas got infected with colibacillosis in the Russian Federation, 176 poultry in 18 outbreak areas got infected with salmonellosis.

In 2018 colibacillosis was registered in 87 outbreak areas, salmonellosis – in 7 outbreak areas, while the number of chicks and young birds infected with colibacillosis amounted to 547,561 birds, with salmonellosis – 33 birds, the percentage of the total number of diseased birds for each disease was 66.18 and 18.75%, respectively.

In 2019 the number of poultry infected with colibacillosis amounted to 242,410 birds in 103 outbreak areas (29.30% of the total number of colibacillosis-infected poultry), salmonellosis – 116 birds in 6 outbreak areas (65.91% of the total number of salmonellosis-infected poultry). In 2020, 2021 and 2022 no new colibacillosis-infected areas were identified in the Russian Federation, while the number of diseased birds was 33,560 (4,06%), 1,204 (0,15%) and 2,707 (0.33%) respectively.

In 2020 the number of salmonellosis-infected areas decreased to 4 and the number of diseased birds amounted to 22 (12.50% of the total number of diseased birds with salmonellosis). In 2021 no new salmonellosis-infected areas were identified in the Russian Federation, while there was one diseased bird accounting for 0.57% of the total number of diseased birds. In 2022 salmonellosis was registered in one outbreak area, where the number of diseased poultry was 4 birds (2.27% of the total number of salmonellosis-infected poultry).

Thus, the data provided indicate that these nosological units are registered annually in the Russian Federation, but as a result of veterinary and sanitary measures, the number of colibacillosis-infected poultry in the RF Subjects decreased from 66.18% in 2018 to 0.33% in 2022, and the number of salmonellosis-infected poultry decreased from 65.91% in 2019 to 2.27% in 2022 (Fig.). At the same time, the data obtained suggest that bacterial diseases still occupy a specific place in the nosological profile of poultry infectious pathology and may pose a danger to poultry establishments. Therefore, in order to ensure the animal disease freedom of poultry population and timely implement a complex of preventive, veterinary and sanitary measures, it is necessary to constantly monitor and analyze the data on colibacillosis and salmonellosis occurrence in poultry.

At the next stage of the study, a retrospective analysis of data on Salmonella contamination of poultry meat and poultry products obtained during laboratory tests in 2018–2020 was carried out. Results of tests of poultry products for Salmonella contamination are presented in Table 1.

According to the data obtained, 219,020 samples of poultry meat and poultry products were collected for testing, which included 120,923 samples of poultry meat, 87,259 samples of chicken eggs, 10,838 samples of melange and egg powder. It was established that Salmonella bacteria were detected in 1,716 ± 15 poultry meat samples, which is 1.42% of the total number of meat samples collected for testing. Salmonella was detected in chicken eggs in 0.02% of cases, the proportion of egg product samples (melange and egg powder) containing bacteria was 0.18%. Based on analysis of data on Salmonella contamination in 2018–2020, the following Salmonella serovars were most often found in poultry products: S. enteritidis, S. typhimurium, S. infantis.

The data from the automated VESTA system (laboratory testing of regulated product samples) in 2018–2020 were used for the retrospective analysis of the level of contamination with mesophilic aerobic and facultatively anaerobic microorganisms and coliforms (total viable count) and Escherichia coli bacteria (coliforms) in poultry meat and poultry products. It should be noted that these microbiological safety parameters are specified in the Technical Regulations of the Customs Union “On Food Safety” (TR CU 021/2011) and the Eurasian Economic Union “On Safety of Poultry Meat and Processed Products Thereof” (TR EAEU 051/2021): the total viable count in fresh meat shall not exceed 10 CFU/g (cm³), in chicken and quail eggs – not more than 100 CFU/g (cm³); no coliforms are allowed in 1.0 g (cm³) of fresh meat and 0.1 g (cm³) of chicken and quail eggs.

During the specified period 2,340 samples were tested. As the data in Table 2 show, a significant number of samples do not meet the requirements of regulatory documents according to the VESTA automated system.

CONCLUSION

According to the Ministry of Agriculture of the Russian Federation, the retrospective analysis of colibacillosis and salmonellosis occurrence in poultry farms in the country in 2018–2022 showed that 827,442 birds got infected with colibacillosis in 190 outbreak areas, salmonellosis was registered in 176 birds in 18 outbreak areas during the entire study period. In 2018–2020 219,020 samples of poultry meat and poultry products were subjected to bacteriological testing for the presence of Salmonella. It was found that Salmonella bacteria were detected in 1.42% of poultry meat samples of the total number of meat samples collected for testing, in 0.02% of chicken egg samples, in 0.18% of egg product (melange and egg powder) samples. Despite the seemingly small percentage of bacterial detections, it should be remembered that Salmonella is a pathogenic microorganism and its presence is not allowed in 25 g of meat products, therefore, the aspects of bacterial avian disease prevention have not lost their relevance to date.

Based on the results of our own research and literature data, we came to the conclusion that deterioration of the animal health situation in poultry farms may affect the public health due to consuming unsafe Salmonella-contaminated poultry products. Therefore, it is necessary to ensure assessment of the animal health situation in poultry farms, epizootic monitoring in regions with developed poultry farming, improvement of measures for the prevention and control of poultry infectious diseases and compliance with veterinary and sanitary requirements at each production stage to achieve the biological safety of poultry meat and poultry products.

Contribution: Kurmakaeva T. V. – literature search and analysis, research concept, methodology, data analysis and interpretation, graphic data preparation, final conclusions; Kozak S. S. – literature search and analysis, research concept, data analysis and interpretation; Baranovich E. S. – literature search and analysis, research concept, data analysis and interpretation, graphic data preparation, text preparation and editing.

Вклад авторов: Курмакаева Т. В. – поиск и анализ научной литературы, концепция исследования, развитие методологии, анализ и интерпретация данных, подготовка графического материала, итоговые выводы; Козак С. С. – поиск и анализ научной литературы, концепция исследования, анализ и интерпретация данных; Баранович Е. С. – поиск и анализ научной литературы, концепция исследования, анализ и интерпретация данных, подготовка графического материала, подготовка и редактирование текста.