5 dangerous zoonotic diseases in ruminants: protect your herds and your health

Zoonotic diseases are infectious illnesses that can be transmitted between animals and humans, posing a dual risk. These diseases spread through various pathways, including aerosols, vectors (e.g., insects), ingestion of contaminated food or feed, indirect contact via fomites (contaminated objects), and direct contact. Individuals working closely with animals, such as farmers and veterinarians, are particularly at risk [1].

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The European Union One Health 2023 Zoonoses Report highlights significant trends in zoonotic diseases impacting humans, animals, food, and feed. Notably, the absolute number of cases of campylobacteriosis and salmonellosis, the first and second most reported zoonosis in humans, has increased in comparison with previous year, while hospitalizations and fatalities have surged to unprecedented levels [2].

For ruminant practitioners, direct contact with infected cattle increases the likelihood of exposure to zoonotic pathogens. Protecting yourself not only preserves your health but also serves as a critical public health measure [3].

Here are five zoonotic diseases in ruminants you should watch out for, along with strategies to safeguard your herds and yourself [4].

1. Bovine tuberculosis

Bovine tuberculosis is caused by Mycobacterium bovis and Mycobacterium caprae and is transmitted through direct contact with body tissues, fluids, or aerosols [5].

In cattle, it has a prolonged incubation period lasting months to years. Symptoms include weight loss, chronic cough, difficulty breathing, reproductive issues, mastitis, and metritis, though some cattle remain asymptomatic.

In humans, the disease also has a long incubation period. Symptoms such as fever, cough, and weight loss may develop, with severe cases leading to meningitis, which can be fatal if untreated. Treatment requires long-term antibiotics. Regular testing, protective handling practices, and proper equipment use are key preventive measures.

In 2023, here were 138 confirmed cases of human tuberculosis due to M.bovis or M. caprae, a  6.1% decrease in notification in the European Union compared with 2022.

In the European Union, tuberculosis rates in humans (including zoonotic tuberculosis) are among the lowest in the world. Most of the European Member States have the disease-free status from infection with Mycobacterium tuberculosis complex (M. bovis, M. caprae and M. tuberculosis), with a very low overall prevalence of infected bovine herds, thanks to the eradication programmes for bovine tuberculosis in force (Table 1).

2. Q Fever

Q fever, caused by C. burnetii, affects humans and animals. Due to its microbial characteristics that include high virulence, environmental resistance and aerosol dissemination, it is classified as a potential biological weapon. Humans mainly acquire the infection through environmental contamination arising from bacterial shedding in infected animals, but also possibly through tick-borne transmission. [6]. Outside of occupational exposure, human infection may be influenced by environmental and meteorological conditions. Wind speed direction and geographical dispersion are important risk factors to consider.

The disease is highly prevalent, with half of cattle farms and one third of small ruminant farms testing positive for Q Fever. In ruminants, Q Fever symptoms usually appear after an incubation period of 1–3 weeks and include reproductive disorders  such as abortion, weak calves, stillbirths and infertility, though some animals remain asymptomatic.

In humans, the incubation period is 2–3 weeks, with flu-like symptoms being the most common. Nevertheless, 4% of patients require hospitalization due to hepatitis, lung infection, meningitis or encephalitis. This acute form of the disease mainly concerns immunodepressed people. 2% of Q fever infection will progress to a chronic form, which manifests itself as cardiovascular disease (endocarditis or vascular infection), chronic fatigue or for pregnant women abortion or premature delivery. Chronic cases are more challenging to treat, but antibiotics are effective for acute infections.

A good knowledge of the risk factors and a proper management of the farm regarding the disease by biosecurity measures and animal vaccination is crucial to avoid people contamination, especially when immunodepressed people or pregnant women work on the farm. This risk must also be considered when the farm receives visitors.

In 2023, the number of human Q fever cases (805) increased compared to 2022, with 90% of cases occurring in Bulgaria, France, Germany, Hungary, Romania and Spain (Table 1).

A key challenge will be reducing human exposure to this zoonosis through a preventive ‘One Health’ approach. In Spain, where Q fever cases have been notably high, a surveillance programme for ruminant herds was updated in 2023. As a result, new control measures have been introduced to mitigate human outbreaks, with plans to harmonise these actions at the national level in the near future. 

3. Salmonellosis

Salmonellosis, caused by non-typhoidal Salmonella serovars, spreads through contaminated feed or water, direct contact with infected animals, fomites, and flies[7].

In cattle, the incubation period can vary but symptoms may appear within 1–2 days in severe cases. Signs include diarrhea, abortion, reduced milk production, septicemia, and neurological symptoms, especially in calves.

In humans, symptoms like acute diarrhea, abdominal pain, and vomiting typically appear 6–72 hours after exposure. Severe cases can lead to septicemia. Treatment involves rehydration and antibiotics, although antibiotic resistance is a growing concern. Prevention relies on good hygiene practices, proper feed storage, and close health monitoring of herds.

In 2023, there were 77,486 confirmed cases of human salmonellosis (Table 1), corresponding to a European Union notification rate of 18.0 cases per 100,000 population. This was an increase of 16.9% compared with the rate in 2022. 

4. Cryptosporidiosis

Cryptosporidiosis is caused by Cryptosporidium parvum and transmitted through ingestion of contaminated food, feed, or water, as well as fomites and environmental contamination [8].

In cattle, the incubation period is 3–5 days, with symptoms such as diarrhea and loss of appetite. However, some animals remain asymptomatic.

In humans, symptoms may appear 2 days to 2 weeks post-infection and include watery diarrhea, abdominal pain, and appetite loss, potentially leading to dehydration. Most cases resolve without treatment, but antiparasitic medications are available. Prevention includes providing clean water and feed, avoiding contaminated areas, and practicing good hygiene.

5. Leptospirosis

Leptospirosis is caused by spirochete bacteria that reside in the kidneys of infected hosts. It is transmitted through contact with infected urine, contaminated feed or water, aborted tissues, or aerosols [9].

In cattle, symptoms appear 7–12 days after infection and include abortion, decreased fertility, conjunctivitis, jaundice, and severe cases in calves.

In humans, the acute phase includes fever, muscle pain, nausea, headaches, and eye redness. The immune phase can escalate to severe symptoms such as jaundice, meningitis, kidney failure, pulmonary hemorrhage, and death. Preventive measures involve reducing exposure to rodent carriers, using protective gear, and maintaining sanitation.

 Table 1 – Overview of tuberculosis, Q fever, salmonellosis, cryptosporidiosis and leptospirosis, related to EU data (2023 and comparison with 2022) on human infections, hospitalizations, deaths and number of infected animals (adapted from the European Union One Health 2023 Zoonoses Report).
*This increase in human infections is related to a decreased on the number of state member that report cryptosporidiosis in 2022.
**Only available data from 2022. The number of infections is compared to 2021, 

Take home messages

• Conduct regular testing and collaborate with veterinarians and public health authorities.
• Prioritize hygiene, including protective equipment and handwashing.
• Clean equipment and environments thoroughly, avoiding practices that produce aerosols.

Monitoring your own health is a priority, not only for yourself but for your herd and the people around. The fact that an animal or a human can be asymptomatic represents a silent disseminator of disease.

Although all these diseases are treated, an early diagnostic is key to mitigate more serious repercussions.

Finally, it is essential that you refer to your doctors, especially if you present any general symptom, your activity, the species you work with, as well as the environment around you, feed and water storage.

References

[1]    The Center for Food Security & Public Health, Zoonotic Diseases of Cattle, 2021. http://www.cfsph.iastate.edu/DiseaseInfo/.

[2]    European Food Safety Authority (EFSA), European Centre for Disease Prevention and Control (ECDC), The European Union One Health 2023 Zoonoses Report, EFSA Journal 21 (2024). https://doi.org/10.2903/j.efsa.2024.9106

[3]    C.J. McDaniel, D.M. Cardwell, R.B. Moeller, G.C. Gray, Humans and cattle: A review of bovine zoonoses, Vector-Borne and Zoonotic Diseases 14 (2014) 1–19. https://doi.org/10.1089/vbz.2012.1164.

[4]    Public Health - England, Guidance - List of zoonotic diseases, 2019. https://www.gov.uk/government/publications/list-of-zoonotic-.

[5]    European Health and Digital Executive Agency (HaDEA), Bovine tuberculosis, Https://Hadea.Ec.Europa.Eu/Programmes/Single-Market-Programme-Food/Veterinary-Programmes/Bovine-Tuberculosis_en (n.d.).

[6]    European Centre for Disease Prevention and Control, Facts about Q fever, Https://Www.Ecdc.Europa.Eu/En/q-Fever/Facts (n.d.).

[7]    European Centre for Disease Prevention, Salmonellosis Annual Epidemiological Report for 2022 Key facts, n.d.

[8]    European Centre for Disease Prevention and Control, Cryptosporidiosis – Annual Epidemiological Report 2022, n.d.

[9]    European Centre for Disease Prevention and Control, Leptospirosis Annual Epidemiological Report for 2022 Key facts, n.d.