An update on the risk of transmission of Ebola virus (EBOV) via the food chain

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Article
European Food Safety Authority
EFSA Journal
EFSA Journal 2014;12(11):3884 [25 pp.].
doi
10.2903/j.efsa.2014.3884
Acknowledgements

EFSA wishes to thank the members of the Working Group on risk of transmission of Ebola virus via the food chain: Arie Havelaar, Marion Koopmans, Maurice Pensaert, Moez Sanaa for the preparatory work on this scientific output; the members of the EFSA Panel on Biological Hazards for their endorsement of the scientific output; and the hearing experts: Hilde Kruse, Elisabeth Mumford (World Health Organization) and EFSA staff: Ernesto Liébana Criado, Winy Messens and Pablo Romero Barrios for the support provided to this scientific output.

Type
Scientific Report of EFSA
On request from
European Commission
Question Number
EFSA-Q-2014-00705
Approved
24 ottobre 2014
Published
4 novembre 2014
Affiliation
European Food Safety Authority (EFSA), Parma, Italy
Note
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Abstract

Several animal species were found to harbour Zaïre Ebola virus (ZEBOV), mainly non-human primates and fruit bats. The risk for persons in Europe linked to the transmission of ZEBOV via handling and preparation (by consumers or staff handling the food in kitchens immediately prior to consumption), and consumption of bushmeat illegally imported from Africa was assessed. The outcome was the probability for at least a single human case of ZEBOV in Europe due to transmission via bushmeat. This probability results from a combination of several steps: 1) the bushmeat has to be contaminated with ZEBOV; 2) the bushmeat has to be (illegally) introduced into the EU; 3) the imported bushmeat needs to contain viable virus when it reaches the person; 4) the person has to be exposed to the virus; and 5) the person needs to get infected following exposure. Due to lack of data and knowledge, which results in very high uncertainty, it is not possible to estimate this risk. Considering all these elements, and based on: (i) the limited number of outbreaks confirmed to date in Africa in spite of the routine consumption of bushmeat in that continent, (ii) the handling of bushmeat in Europe not involving high risk practices such as hunting and butchering, and (iii) the assumed low overall consumption of bushmeat in Europe, it can be assumed that the potential for introduction and transmission of ZEBOV via bushmeat in Europe is currently low. The public health consequences of such an event would be very serious given the high lethality and potential for secondary transmission. Hardly any information on ZEBOV infectivity is available on the effect of salting, smoking or drying of meat. Therefore, a conclusion cannot be reached regarding the effectiveness of these methods for virus inactivation. Thorough cooking (100 °C) will destroy the virus.

Summary

Following a request from the European Commission, EFSA was asked to provide scientific and technical assistance on the risk of transmission of Ebola virus (EBOV) via the food chain. More specifically, EFSA was asked to review the risk for persons in Europe linked to transmission of EBOV via handling and preparation (both carried out by consumers immediately before consumption) as well as consumption of bushmeat illegally imported from Africa. EFSA was also asked to assess the survival of EBOV in meat or meat products, the range of species that are able to transmit or carry the virus, and whether any data exist on physical or chemical treatments that would inactivate the EBOV in products of animal origin and especially in meat.

The outcome of the assessment is the probability for at least a single human case of Zaïre Ebola virus (ZEBOV) in Europe due to transmission via handling and preparation (carried out by consumers or staff handling the food in kitchens immediately prior to consumption) and consumption of bushmeat illegally imported from Africa. This probability is the result of a combination of several necessary steps: 1) the bushmeat has to be contaminated with ZEBOV at the point of origin; 2) the bushmeat has to be (illegally) introduced into the EU; 3) the imported bushmeat needs to contain viable virus when it reaches the person; 4) the person has to be exposed to the virus; and 5) the person needs to get infected following exposure.

Due to lack of data and knowledge, which results in very high uncertainty, it is not possible to estimate this risk. However, considering all the elements in these steps, and based on: (i) the limited number (n = 27) of outbreaks that have been reported to date in Africa in spite of the routine consumption of bushmeat in that continent, (ii) the handling of bushmeat in Europe not involving high risk practices such as hunting and butchering, and (iii) the assumed low overall consumption of bushmeat in Europe, it can be assumed that the potential for introduction and transmission of ZEBOV via bushmeat in Europe is currently low. It should be noted that the public health consequences of such an event (a single human case of ZEBOV occurring in Europe) would be very serious given the high lethality and potential for secondary transmission. In addition, it should be noted that the information considered in this report is largely based on historic Ebola outbreaks and not the current outbreak in West Africa.

Some studies on physical or chemical treatments have been performed on cell-cultured virus as starting material, in some cases diluted with serum. These studies indicate that ZEBOV can survive in liquid media for many days. Survival is better at low temperature (4 °C) than at room temperature. In addition, freezing or refrigeration will preserve infectivity of ZEBOV; ZEBOV can survive multiple freezing/thawing and a long-term storage when frozen. Inactivation of this virus occurs when heated at 75 °C for 30 minutes, after ultra violet (UV) and gamma irradiation, and with 1 % formaldehyde or β-propiolactone. ZEBOV is also susceptible to 3 % acetic acid (pH 2.5), 1 % glutaraldehyde, alcohol-based products, and dilutions (1:10-1:100 for ≥ 10 minutes) of 5.25 % household bleach (sodium hypochlorite) and calcium hypochlorite (bleach powder). Hardly any information is available on the effect of salting, smoking or drying of meat on ZEBOV infectivity. Therefore a conclusion cannot be reached regarding the effectiveness of these methods for virus inactivation. Thorough cooking (100 °C) will rapidly and efficiently destroy the virus.

Considering that ZEBOV infection in some animal species, such as non-human primates, is characterised by a haemorrhagic disease, it is reasonable to expect that an extensive viraemia occurs and that the virus is present in blood and in all organs, secretions and excretions at the height of infection or when the animal has died. The virus has also been isolated from the muscle of non-human primates. It can, therefore, be assumed that virus will be present in the meat of such animals immediately after slaughter. However, there is no information on survival of EBOV in meat or animal products, although it is expected that survival is better at low temperature (4 °C) than at room temperature. The probability of the contaminated bushmeat having viable virus on arrival into the EU would be higher in fresh or frozen meat after a short transport time, and lower in well dried or smoked meat exposed to higher temperatures during transport.

In the very limited number of studies to date, EBOV has only been detected in carcasses of gorillas (Gorilla gorilla), chimpanzees (Pan troglodytes), duikers (Cephalophus spp.) and from live individuals of some species of Old World fruit bats (Epomops franqueti, Hypsignathus monstrosus, Myonycteris torquata), small rodents (Mus setulosus, Praomysspp.) and in one species of shrew (Sylvisorex ollula). In addition, antibodies against EBOV have been reported in these and other fruit bat species (Epomophorus gambianus, Eidolon helvum, Micropterus pusillus, Mops (Mops) condylurus and Hipposideros gigas, Roussetus aegyptiacus and Rousettus (Rousettus) amplexicaudatus) and dogs (Canis lupus familiaris).

Keywords
Zaïre Ebola virus, ZEBOV, bushmeat, survival, inactivation, transmission
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Number of Pages
25