Salmonellosis is a disease caused by bacteria of the genus Salmonella that can affect humans and animals. Its importance lies in 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 faeces. Zoonosis by Salmonella is usually caused by S. enterica serotypes Typhimurium and Enteritidis, as well as Infants 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 into septicaemia or focal infection, especially in immunosuppressed people.
Prevalence of Salmonellosis in Pakistan:
Salmonellosis is a food-borne bacterial disease having zoonotic importance from a global perspective. A huge range of foodstuffs have been involved in salmonellosis, yet animal-originated foods typically from poultry products including eggs have been consistently involved in outbreaks of disease. To study the prevalence of Salmonella species a total of 384 samples were collected including hen eggs (252) and egg storing trays (132) from various poultry farms and marketing outlets of Faisalabad. A sterile cotton swab was used for sampling the surface of eggs and egg storing trays.
Egg yolk and albumin was also checked for the presence of Salmonella spp. Hekaton enteric agar was used as selective media for isolation of Salmonella species and to identify Salmonella serovars polyvalent antisera were used. Prevalence was observed at 29.36 and 38.88% in eggshells, 10.31 and 15.07% in egg contents and 28.78 and 43.93% in egg storing trays from poultry farms and marketing outlets, respectively. The occurrence of Salmonella spp. was lower in eggs collected from poultry farms and in egg storing paper trays as compared to that of eggs collected from market outlets and in egg storing plastic trays.
Vaccination as a Salmonella Control Strategy
In egg production systems, vaccination has become an important part of controlling Salmonella prevalence. Experimental results have demonstrated that bacteria in the faeces, tissues, and eggs of chickens after vaccination was significantly reduced. The existing Salmonella vaccines primarily include inactivated, live attenuated, and subunit vaccines. In poultry production, vaccines are often used in conjunction with strict biosecurity measures to achieve the best results.
Salmonella Typhimurium Vaccines
Salmonella is an intracellular pathogen which, after invading the epithelium of the gastrointestinal tract, enters the gut-associated lymphoid tissue and replicates in macrophages and dendritic cells. There are several commercially available inactivated and live attenuated Salmonella Typhimurium vaccines. The use of live attenuated vaccines is favoured because they elicit both cell-mediated and humoral immune responses.
References
– Jia, S., McWhorter, A. R., Andrews, D. M., Underwood, G. J., & Chousalkar, K. K. (2020). Challenges in vaccinating layer hens against Salmonella typhimurium. Vaccines, 8(4), 696.
– Shahzad, A., Mahmood, M. S., Hussain, I., Siddique, F., & Abbas, R. Z. (2012). Prevalence of salmonella species in hen eggs and egg storing-trays collected from poultry farms and marketing outlets of Faisalabad, Pakistan. Pak J Agri Sci, 49(4), 565-568.