Occupational zoonoses

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Brian Cook and Jayne Farrant, Health & Safety Laboratory, UK


Introduction

Zoonoses are infections that are spread from animals to humans. This article gives a general overview of the occurrence and transmission of zoonotic diseases, with particular emphasis on zoonotic diseases in the workplace and why they present a health and safety concern for certain occupations. Common occupational zoonoses are presented and summary information is provided on the biological agent responsible for causing disease, methods of transmission, incidence and potential health effects. Occupations and work-based activities that present an increased risk of zoonotic infections are discussed, as well as key preventative measures that can be taken to reduce these risks.


Overview of zoonoses

The World Health Organization (WHO) defines zoonotic diseases as ‘any diseases or infections that are naturally transmitted between vertebrate animals and humans.’ Agents causing zoonotic diseases may be bacteria, fungi, viruses, parasites or any other communicable agents, for example prions. Currently there are over 200 recognised zoonoses, some of which have a worldwide distribution and others which are localised to specific regions. The situation is not static, and emerging zoonotic diseases are continually being recognised, both animal diseases which have spread to humans for the first time and existing zoonoses spreading to new geographical areas.

Zoonoses tend to occur when there is close contact between humans and animals. They are generally more common in developing countries, as there is often closer contact with animals in these communities and fewer measures in place to prevent infection. New zoonotic diseases or a change in the pattern of zoonoses often occur when there is a change in human activity, for example a change in agricultural practices, or when there is significant movement of an animal or human population, for example as a result of climate change. Increasing globalisation is contributing to the emergence of zoonotic diseases. Zoonoses may be occupationally-acquired, but are not exclusively occupational diseases.

Zoonoses may be transmitted in a variety of ways. This includes direct contact with infected animals, for example in a farm setting. Indirect contact can involve contact with animal secretions or products, consumption of food or drink contaminated with the zoonotic agent, or airborne spread of the agent. Some zoonoses are transmitted via insect vectors, including ticks and mosquitoes. If contact was indirect and the individual had no direct contact with animals, it can often be difficult to establish how transmission occurred.

The incidence of zoonotic infections is different for each individual disease and may change. Incidence is affected by many factors, including the prevalence of infected animals, the method of transmission of the zoonotic agent and the closeness of contact between the animal host and humans. Some zoonotic diseases tend to occur as sporadic cases whereas others occur as outbreaks. The prevalence of zoonotic diseases in Europe is recorded, although there is little data on the proportion of reported cases which are acquired occupationally[1]. There is wide variation in the incidence of zoonoses in Europe, for example human cases of anthrax are rare, whereas campylobacteriosis is the most commonly reported zoonosis, with over 200,000 reported cases in the EU in 2011[1].


Occupational zoonotic diseases

Occupational zoonotic diseases are most common where there is close contact between animals and humans at work, for example in animal husbandry and agricultural occupations, although workers in a wide range of other occupations may also be exposed to zoonotic agents, including those employed in the outdoor leisure industry or the waste water industry and laboratory workers. There are many occupational zoonotic diseases in the world, many of which occur very rarely, although some do pose a significant health risk for workers in certain occupations. While the incidence of specific zoonoses varies from country to country, there are many occupational zoonoses that occur across Europe, although not every disease is present in every country. Table 1 shows details of the most common occupational zoonoses in Europe. While some zoonoses can have severe health effects and in rare cases may even be fatal, in many cases zoonotic infections result in mild or no symptoms and therefore it is thought that many occupational zoonoses are under reported.

Table 1. List of occupational zoonoses in Europe1
Zoonosis Biological Agent Main Reservoir Transmission Risk Occupations2 Health Effects
Alveolar echnococcus Echinococcus multilocularis foxes contact with faeces hunting, outdoor leisure cysts, may be fatal
Anthrax Bacillus anthracis cattle, goats, sheep, pigs, environment direct contact, inhalation, ingestion farming, meat processing skin lesions, flu-like symptoms, pulmonary oedema, may be fatal
Avian Influenza Influenza A viruses birds contact with faeces or saliva poultry farming and processing flu-like symptoms, may be fatal
Bovine Tuberculosis Mycobacterium bovis cattle inhalation, ingestion farming, meat & dairy processing cough, fever, weight loss, may be fatal
Brucellosis Brucella species cattle, goats, sheep, pigs inhalation, ingestion farming, meat processing fluctuating fever, joint pain
Campylobacteriosis Campylobacter species poultry, farm animals ingestion poultry farming, meat processing diarrhoea, abdominal pain
Crimean-Congo haemorrhagic fever (CCHF) CCHF virus wild & domestic animals tick bite, direct contact farming, meat processing, outdoor leisure flu-like, neurological, rash, may be fatal
Crytosporidiosis Cryptosporidium parvum cattle, sheep direct contact, ingestion of water farming, meat processing, waste water processing diarrhoea
Erysipeloid Erysipelothrix rhusiopathiae pigs, fish, birds direct contact farming, meat processing, fishing skin lesions
Giardiasis Giardia species farm & domestic animals ingestion of water outdoor leisure, waste water processing diarrhoea, abdominal cramps
Hantavirus Disease Hantaviruses rodents contact with urine, faeces or saliva, inhalation farming, waste water processing flu-like, may be life threatening
Hydatid Disease Echinococcus granulosus dogs contact with dogs or faeces sheep farming, dog handling cysts
Leptospirosis Leptospira species rodents, cattle contact with contaminated water or cattle urine watersports instructors, waste water processing, cattle farmers flu-like, may be fatal
Louping Ill Louping ill virus sheep, grouse tick bite hill farming flu-like, fever, neurological
Lyme Disease Borrelia burgdorferi birds, mammals tick bite hill farming, outdoor leisure rash, flu-like, arthritis
Orf Orf virus sheep, goats direct contact sheep & goat farming skin lesions
Ovine Chlamydiosis Chlamydophila abortus sheep, goats inhalation sheep & goat farming flu-like, stillbirth, miscarriage, birth defects
Psittacosis Chlamydophila psittaci birds inhalation poultry farming and processing, bird keeping flu-like, pneumonia
Q Fever Coxiella burnetti sheep, cattle inhalation, direct contact farming, meat processing flu-like, may be chronic, birth defects
Rabies Rabies virus, European bat lyssavirus 2 dogs, bats, cats, foxes bite dog handing, bat handling neurological, death
Ringworm Dermatophytes cattle, horses, cats direct contact farming, working with animals skin rash
Salmonella Salmonella species wild & domestic animals ingestion poultry farmers diarrhoea, vomiting
Streptococcal sepsis Streptococcus suis, Streptococcus zooepidemicus pigs, cattle direct contact, ingestion farming flu-like, toxic shock syndrome
Swine Influenza Influenza A & C viruses pigs contact with faeces or saliva pig farming flu-like symptoms, may be fatal
Tickborne encephalitis (TBE) TBE virus small mammals, livestock, birds tick bite hill farming, forestry, outdoor leisure flu-like, fever, neurological
Tularemia Francisella tularensis rodents, rabbits, hares tick/mosquito bite, direct contact, contaminated water, aerosol outdoor leisure, waste water processing ulcers, sore throat, pneumonia, may be fatal
Toxoplasmosis Toxoplasmosis gondii mammals ingestion farming, gardening, vegetable picking flu-like, stillbirth, miscarriage, birth defects
Verotoxigenic E.coli VTEC (including E.coli 0157) mammals ingestion farming, vegetable picking diarrhoea, may be fatal
West Nile Virus West Nile Virus birds mosquito bite Outdoor leisure, stabling flu-like, may be fatal

1This table lists the most common occupational diseases in Europe. It is not an exhaustive list and not all diseases are present in all European countries.
2This table provides summary information. It lists the occupations at highest risk of a particular zoonosis, but does not provide an exhaustive list of all occupations where there is a risk of zoonotic infection. For example, veterinary surgeons may be at risk from any of the above diseases, depending on the animals they are caring for and laboratory scientists working with a zoonotic agent will be at risk from the disease caused by that particular agent. Certain zoonotic diseases can be spread from human to human and may therefore pose a risk to healthcare workers, although this is not zoonotic transmission.
Source: Collated by Farrant, J. 2013.

The situation is constantly changing and therefore it is necessary to monitor the emergence of zoonotic infections. A review of emerging zoonoses in Europe between 2000 and 2006 identified 15 emerging zoonotic agents[2]. Avian influenza is a currently emerging zoonosis and an outbreak in the Netherlands in 2003 affected 89 poultry workers [3]. A recent paper identified the most likely emerging zoonoses in the Netherlands, of which several are important occupational zoonotic agents, including Q fever and bovine tuberculosis[4]. There is the risk of some zoonotic agents acquiring multiple antibiotic resistance and therefore presenting increasing health risks to workers in the future, as current treatments become less effective.

The European Agency for Safety and Health at Work (EU-OSHA) analysed emerging biological risks for occupational health and safety, ranking risks in order of importance. The report concluded that occupational risks related to global epidemics represent the number one risk and - since zoonoses represent three quarters of all human emerging diseases - occupational zoonoses are a significant proportion of these emerging diseases[5].The Report of the World Health Organisation/Food and Agriculture Organisation of the United Nations/World Organisation for Animal Health (WHO/FAO/OIE) joint consultation on emerging zoonotic diseases identified zoonoses which are likely to have increasing impact in Europe and many of these are also occupational diseases[6].


Occupational risk

Zoonotic agents are dangerous substances, which have the potential to damage workers’ health. There is an increased risk of zoonotic diseases in certain occupations, particularly where there is close contact with animals or animal products. The main occupations at risk of zoonoses are those where the workers are in contact with:

  • infected animals;
  • materials or products from infected animals;
  • secretions from infected animals, including saliva, blood and faeces;
  • aerosols or dusts contaminated with secretions from infected animals;
  • land or water contaminated with materials or secretions from infected animals; or
  • infected vectors involved in the transmission of a zoonosis.

For all at risk occupations, there are specific activities that increase the likelihood of infection. It is necessary to identify both the occupations where there is a risk of zoonotic infection and the specific activities that increase the likelihood of infection.

Occupations with an increased risk of zoonotic infections are those in the agricultural industry, particularly farmers who have close contact with potentially infected animals. Workers in related occupations that carry an increased risk include veterinary surgeons, those in the meat processing industry handling potentially infected animal products and those carrying out cleaning and decontamination of premises where animals or animal products are kept. Other risk occupations with close animal contact include those involved in animal husbandry, such as workers in zoos, aviaries or pet shops and others involved with the animal trade, such as customs officers.

Certain zoonoses are particularly associated with contaminated water, for example leptospirosis, cryptosporidiosis and giardiasis. For these agents, the risk of infection is greatest in occupations that are in close contact with water, including certain outdoor leisure occupations and wastewater treatment workers. For a watersports instructor, activities with a higher risk of infection would be those for which immersion in water is likely, which would carry with it an increased risk of ingestion of contaminated water. For workers involved in the wastewater industry, infection would be more likely to occur via aerosol inhalation and therefore higher risk activities would be those processes more likely to generate aerosols.

A specialist occupation with an increased risk of zoonotic infections is that of the laboratory scientist working in facilities that handle zoonotic agents for research purposes. High risk activities include handling infected laboratory animals and culturing the zoonotic agent in the laboratory, although specific procedures are in place to mitigate this hazard. Laboratory workers may be at risk from any of the zoonotic diseases found worldwide, rather than just zoonoses endemic to the country in which they are working.

There is a risk from certain zoonotic agents for workers that are based outdoors, involved in a range of occupations including those involved in outdoor pursuits, nature conservancy, arable farming and gardening. This may be due to direct contact with infected animals, indirect contact via contaminated land or water, or infection via insect vectors. Since it is often difficult to identify the source of exposure for a zoonotic disease, it can be challenging to identify all the occupations that may be at risk from zoonoses.

For many zoonotic agents, all cases of human infection occur as a result of transmission from animal to human and there is no person to person spread. However, for certain zoonoses there can be onward transmission from an infected individual to other, generally close, contacts. For these diseases, healthcare and care workers are at risk, despite the fact that as part of their work they do not have any contact with animals or animal products. For some diseases, for example cutaneous anthrax or ringworm, infection can occur via direct contact with infected skin. For other diseases infection may occur via inhalation of aerosolised bacteria from an infected patient, for example bovine tuberculosis, or via contact with infected faeces where there is poor hygiene, such as cryptosporidiosis and campylobacter.

Controlling the risks of occupational zoonoses

The European Union (EU) Directive 2000/54/EC on the protection of workers from risks related to exposure to biological agents at work lays down minimum requirements for the health and safety of workers exposed to biological hazards at work[7]. Biological agents (of which zoonotic agents are a subset) are dangerous substances which have the potential to damage workers’ health. Within the EU, individual countries have transposed EU Directive 200/54/EC and may even have more stringent national legislation on the handling of biological substances in the workplace; and zoonotic agents are included in this. Biological agents are classified in to four groups based on risk to human health.

Employers have a duty to manage the risks posed by dangerous substances and to have appropriate risk assessments in place. They also need to inform workers of any risks associated with their work. There are currently no exposure limits set for biological agents, as there are for hazardous chemicals, making it more difficult to determine what constitiutes a safe level. The setting of any exposure limits for biological agents is made more difficult by the fact that they are living organisms and so may increase (or decrease) in number over time. For biological agents, an employer has the duty to reduce the risk of exposure to as low a level as necessary in order to protect adequately the health and safety of the workers. This is achieved by addressing the following issues based on the established hierarchy of controls:

  • Elimination – can the zoonotic agent be removed?
  • Substitution – can the zoonotic agent be replaced with a less hazardous substance? This principle is often used in the laboratory setting, where less harmful organisms are used as surrogates for research purposes.
  • Control – if it is not possible to eliminate or substitute to reduce the risk, it may be necessary to implement control procedures. These may include altering how the task is carried out for example, by keeping as low as possible the number of workers (likely) exposed; by designing work processes and engineering control measures so as to avoid or minimise exposure; collective protection measures; and/or, where exposure cannot be avoided by other means, by providing appropriate personal protective equipment (PPE). The hierarchy of control measures should be respected, with the use of PPE as a last resort[7].

With regard to the control of occupational zoonoses, there are some general control measures which reduce the risk of infection for a wide range of zoonoses. These include the following:

  • good personal hygiene practices, especially washing with soap and warm water;
  • covering cuts and scratches with waterproof dressings;
  • wearing of appropriate PPE, for example gloves, overalls, respiratory protection – this must provide relevant protection, while also being suitable for carrying out the required task;
  • good hygiene practices for animal husbandry; and
  • use of an appropriate disinfectant to clean potentially contaminated areas.

For certain zoonoses there is an effective vaccine available and it may be appropriate to administer this to individuals in high risk occupations, for example laboratory workers handling infected animals. In many cases there are effective prophylaxis and treatments available. For these to be used to maximum advantage, it is necessary for workers to be aware of any diseases they may be at risk from and to be able to recognise early symptoms of these diseases. For certain occupations it may be required for workers to inform their employer if they have a weakened immune system.

The monitoring of diseases is very important in the control of occupational zoonoses, as it enables risk occupations and activities to be identified and highlights any changes in trends. EU Directive 2003/99/EC lays down minimum requirements for all Member States for monitoring of zoonoses, zoonotic agents and related antimicrobial resistance[8]. This is in addition to the excellent monitoring and reporting systems which have been in place for may years in some Member States. Rabozzi et al., (2012) have argued the need for the ‘One Health Approach’ of close cooperation between veterinary surgeons, occupational health physicians and public health experts in order to better control the risks of emerging zoonoses[9].

Some occupational zoonoses have the potential to cause epidemics among the general population. Appropriate control of occupational zoonoses can aid in the prevention of epidemics and therefore in the protection of the public. An example of an emerging zoonosis with the potential to affect the general public is pandemic flu resulting from avian influenza. Effective controls to prevent human infection within the poultry industry will act to control the risk to the general public.


Conclusion

Occupational zoonoses represent a diverse group of diseases, some causing very mild and others life threatening symptoms. A significant proportion of the workforce in Europe is exposed to biological agents in the course of their work and therefore an understanding of the risks presented by zoonoses is essential. Certain workers, for example laboratory scientists, generally have a good understanding of the risks involved and work in conditions that reduce these risks as much as possible. However, there is a need for increased awareness of zoonoses among other occupations, for example in the agricultural industry, where individuals often have very little appreciation for the risk posed by zoonotic agents.


References

  1. 1.0 1.1 EFSA - European Food Safety Authority & ECDC - European Centre for Disease Prevention and Control, The European Union Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents and Food-borne Outbreaks in 2011, EFSA Journal, Vol. 11, No 4:3129, 2013,. Available at: [1]
  2. Vorou, R. M., Pappavassiliou, V. G. & Tsiodras, S., ‘Emerging zoonoses and vector-borne infections affecting humans in Europe’, Epidemiological Infection, Vol. 135, 2007, pp.1231-1247.
  3. Fouchier, R. A. M., Schneeberger, P. M., Rozendaal, F. W., Broekman, J. M., Kemink, V., Munster, S. G., Kuiken, T., Rimmelzwaan, G. F., Schutten, M., van Doornum, G. J. J., Koch, G., Bosman, A., Koopmans, M. & Osterhaus A. D. M. E. ‘Avian influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome’, Proceedings of the National Academy of Sciences of the United States of America, Vol. 101, No 5, 2004, pp. 1356-1361.
  4. Havelaar, A. H., van Rosse, F., Bucura, C., Toetenel, M. A., Haagsma, J. A., Kurowicka, D., Heesterbeek, J. (Hans) A. P., Speybroeck, N., Langelaar, M. F. M., van der Giessen, J. W. B., Cooke R. M. & Braks, M. A. H. ‘Prioritizing Emerging Zoonoses in The Netherlands’. PLoS One, Vol. 5, No 11, e13965, 2010. Available at: [2]
  5. EU-OSHA - European Agency for Safety and Health at Work, Expert forecast on Emerging Biological Risks related to Occupational Safety and Health, 2007. Available at: [3]
  6. FAO - Food and Agriculture Organization of the United Nations, WHO - World Health Organization & OIE - World Organisation for Animal Health,Report of the WHO/FAO/OIE joint consultation on emerging zoonotic diseases, 2004, Geneva, Switzerland. Available at: [4]
  7. 7.0 7.1 ‘Directive 2000/54/EC of the European Parliament and of the Council of 18 September 2000 on the protection of workers from risks related to exposure to biological agents at work (seventh individual directive within the meaning of Article 16(1) of Directive 89/391/EEC)’, OJ L 262. Available at: [5]
  8. ‘Directive 2003/99/EC of the European Parliament and of the Council of 17 November 2003 on the monitoring of zoonoses and zoonotic agents, amending Council Decision 90/424/EEC and repealing Council Directive 92/117/EEC’, OJ L 325. Available at: [6]
  9. Rabozzi, G., Crespi, E. Somaruga, C., Sakooti, M., Tabibi, R., Vellere, F., Brambilla, G. & Colosio, C., ‘Emerging Zoonoses: the “One Health Approach”’, Safety and Health at Work, Vol. 3, 2012, pp. 77-83.


Links for further reading

EU-OSHA - European Agency for Safety and Health at Work, European Survey of Enterprises on New and Emerging Risks (ESENER): Managing safety and health at work, European Risk Observatory Report, 2010. Available at: [7]

EU-OSHA - European Agency for Safety and Health at Work, Worker representation and consultation on health and safety: An analysis of the findings of the European Survey of Enterprises on New and Emerging Risks (ESENER), 2012. Available at: [8]

WHO – World Health Organization (2013). Zoonoses. Retrieved on 28 January 2013, from: [9]

European Centre for Disease Prevention and Control (ECDC) Annual Epidemiological Report 2011. Available at: [10]

EU-OSHA – European Agency for Health and Safety at Work (2013). Biological agents and agriculture. Retrieved on 28 January 2013, from: [11]

PHE – Public Health England. Zoonoses (2013). Retrieved on 14 May 2013, from: [12]

HSE - Health and Safety Executive. Zoonoses (2013). Retrieved 28 January 2013, from: [13]

Contributors

Taina Paakkonen