Zoonotic risks of pathogens from sheep and their milk borne transmission

Abstract

Sheep were domesticated around 9000 BC in the Middle East, and since then milk from sheep gradually became very popular, not only for drinking but also for making cheeses and other dairy products. Nowadays, these dairy products are also important for people with an allergy to cow milk, and these products are an essential part of the local daily diet in regions of the world that are not suitable for cows and goats. Consumption of raw milk and raw milk products has a zoonotic risk, and with regard to sheep, the main pathogens associated with such dairy products are: Brucella melitensis, Campylobacter spp., Listeria spp., Salmonella spp., Shiga-toxin producing Escherichia coli, Staphylococcus aureus, tick borne encephalitis virus, and Toxoplasma gondii. Especially, young children, elderly people, pregnant women and immunocompromised (YOPI) persons, and those suffering from disease should be aware of the risk of consuming raw milk and raw milk products. This latter risk can be reduced by proper flock health management, prevention of contamination during milking, adequate milk processing, transport, and refrigerated storage. Only processes equaling pasteurization sufficiently reduce zoonotic risks from milk and milk products, but proper cooling is essential and recontamination must be prevented. Therefore, strict hygiene practices throughout the production process and supply chain especially for raw milk and raw dairy products, should be applied. Small scale production systems pose a greater risk compared to industrialized production systems because of a less protocolized and controlled production process. This manuscript describes zoonotic risks of pathogens from sheep and their milk borne transmission. Additionally, routes of contamination, possibilities for multiplication, and prevention measures thereof are described. We summarize some major human outbreaks caused by consumption of sheep milk and products made thereof, and finally discuss their implications.

Clinical Presentation and Laboratory Diagnostic Work-Up of a Horse with Tick-Borne Encephalitis in Switzerland

“…Tick-borne encephalitis (TBE) is an arboviral infection with tick-borne encephalitis virus (TBEV) causing neurological signs in humans and animals. Transmission of TBEV mostly occurs via infected ticks [ 1 ], although rare transmission by unpasteurized dairy products has been reported [ 2 ]. The incidence of the disease in humans reportedly increases in Europe owing to an expansion of endemic areas and prolongation of the tick activity season [ 3 , 4 ], which may increase the risk for clinical disease in horses.…”

Apicomplexan Protozoa Responsible for Reproductive Disorders: Occurrence of DNA in Blood and Milk of Donkeys (Equus asinus) and Minireview of the Related Literature

“…The presence of T. gondii DNA in camel milk has been reported in several studies [ 38 , 39 , 54 ], even though in another study all specimens tested negative [ 53 ]. The literature dealing with potential infection of ovine milk has been recently reviewed [ 57 ], and T. gondii DNA and viable tachyzoites occurrence has also been reported [ 38 , 39 , 48 , 53 , 54 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ]. Camossi et al [ 59 ] reported the presence of T. gondii DNA in milk from naturally infected ewes and detected T. gondii DNA twice in the milk of two sheep, suggesting a possible resurgence of tachyzoites from cysts, which can circulate again and be excreted through the milk.…”

Applied Proteomics in ‘One Health’

“…In animals, the infection can cause abortion, although it is usually subclinical. C. burnetii is excreted in vaginal secretions, aborted material, milk, faeces and urine [ 136 , 137 , 138 ]. Human infections have been recorded mainly after consumptions of milk of affected animals, as was the case in an outbreak of the infection in the Netherlands, which occurred subsequently to an outbreak in goat herds [ 139 , 140 ].…”