Salmonella control programs in Denmark

Abstract

We describe Salmonella control programs of broiler chickens, layer hens, and pigs in Denmark. Major reductions in the incidence of foodborne human salmonellosis have occurred by integrated control of farms and food processing plants. Disease control has been achieved by monitoring the herds and flocks, eliminating infected animals, and diversifying animals (animals and products are processed differently depending on Salmonella status) and animal food products according to the determined risk. In 2001, the Danish society saved U.S.$25.5 million by controlling Salmonella. The total annual Salmonella control costs in year 2001 were U.S.$14.1 million (U.S.$0.075/kg of pork and U.S.$0.02/kg of broiler or egg). These costs are paid almost exclusively by the industry. The control principles described are applicable to most industrialized countries with modern intensive farming systems.

Figure 1

Salmonella in Danish broiler flocks as determined by bacteriologic testing of every flock 2–3 weeks before slaughter (N>4,000 flocks/year).

Figure 2

A) Receipt of 60 eggs per producer every 9 weeks (barcode indicating producer is shown). B) The “eggbreaker” punches a hole in 30 eggs at a time. C) Withdrawal of egg yolk from 30 eggs and transfer to microtiter tray. D) Enzyme-linked immunosorbent assay analysis, reading, and transfer of results to central database.

Figure 3

Salmonella in Danish layer flocks as determined by serologic and bacteriologic testing of each commercial flock in week 9 of production.

Figure 4

A) Receipt of pork samples from the slaughterhouse. Each tube is labeled with a barcode, indicating herd of origin. Samples are frozen overnight. B) The tube is entered in a rack with the barcode facing outward. Meat juice sieves into the tube from the container during thawing. C) Withdrawal of meat juice from tube and transfer to microtiter tray. D) Enzyme-linked immunosorbent assay analysis, reading, and transfer of results to central database.

Figure 5

Prevalence of Salmonella in Danish pig herds as determined by continuous serologic testing of all commercial pig herds (N >700,000 samples tested/year). Herds are categorized in three levels based on the proportion of seropositive meat juice samples during the last 3 months. Owners in level 2 and 3 are encouraged to seek advice on how to reduce the Salmonella problem in the herd (e.g., feeding, hygiene, and management). Furthermore, pigs from level 3 herds can only be slaughtered in special slaughterhouses under special hygienic precautions. Data from the Danish Veterinary and Food Administration.

Figure 6

Salmonella detected in pork, as determined by continuous randomized sampling of pork end-products from all major national pig slaughterhouses (N >30,000 samples/year).

Figure 7

Effects of Salmonella control programs as indicated by incidence of human infection attributable to the different major sources of human salmonellosis in Denmark; 1) Salmonella control program for broiler chickens implemented, 2) Salmonella control program implemented for pigs and pork, 3) Salmonella control program implemented for layer hens and eggs The three sources account for approximately 50% to 75% of Salmonella each year. Remaining cases are attributable to beef, imported food products, infections acquired while traveling abroad, and unknown sources. Incidence (cases/100.000 inhabitants).