Topic 1.4 Zoonoses, Anthropozoonoses and One Health

Occupational Therapists (OTs) working with assistance animals must understand the principles of zoonotic disease transmission to support safe, evidence-informed practice. While healthy assistance animals pose a very low risk of transmitting infectious diseases, all animals have the potential to carry microorganisms that may occasionally be transmitted to humans. An understanding of zoonoses enables practitioners to implement appropriate infection prevention measures without unnecessarily restricting the important role assistance animals play in supporting health, wellbeing and occupational participation.

Historically, infectious diseases transmitted between animals and humans have significantly influenced both human and veterinary medicine. More than 60% of known human infectious diseases are considered zoonotic, and approximately 75% of emerging infectious diseases affecting humans originate from animals. However, infectious disease transmission is not always one-directional. Humans may also transmit diseases to animals, and some diseases can circulate between both populations or arise from shared environmental reservoirs. Understanding these different pathways enables Occupational Therapists to adopt a balanced, evidence-based approach to infection prevention that protects both members of the assistance animal partnership.

Effective prevention of zoonotic diseases relies upon a collaborative, multidisciplinary approach involving Occupational Therapists, veterinarians, medical practitioners, assistance animal trainers, handlers and public health agencies. This reflects the principles of One Health, recognising that human health, animal health and environmental health are interconnected. By working collaboratively and applying evidence-informed infection prevention strategies, practitioners can protect clients and assistance animals while promoting inclusive access to occupational therapy services.

This topic explores the different patterns of disease transmission between humans, animals and the environment, common infectious diseases relevant to assistance animal practice, risk factors for transmission, prevention strategies, and the role of Occupational Therapists in promoting safe, ethical and inclusive practice.

Understanding Zoonoses and Related Disease Transmission

The term zoonosis (plural: zoonoses) refers broadly to infectious diseases that are naturally transmissible between vertebrate animals and humans. However, modern infectious disease science recognises that transmission between humans and animals occurs in several different ways. Understanding these distinctions is important because effective infection prevention must protect both human and animal health.

Within the One Health framework, four categories of disease transmission are commonly recognised:

• anthropozoonoses (animal to human)
• zooanthroponoses (human to animal)
• amphixenoses (bidirectional transmission)
• sapronoses (environmental transmission).

Recognising these different transmission pathways helps Occupational Therapists move beyond the misconception that animals are always the source of infection and instead undertake comprehensive, evidence-informed risk assessments.

Anthropozoonoses (Animal-to-Human Transmission)

Anthropozoonoses are infectious diseases naturally transmitted from animals to humans. These are the diseases most commonly referred to as zoonotic diseases and have traditionally been the primary focus of public health and veterinary medicine.

Transmission may occur through:

• direct contact with infected animals
• saliva
• urine
• faeces
• blood
• contaminated environments
• food
• water
• vectors such as fleas, ticks or mosquitoes.

Examples include:

• leptospirosis
• salmonellosis
• campylobacteriosis
• toxoplasmosis
• ringworm (dermatophytosis)
• Q fever
• rabies (outside Australia).

Although anthropozoonotic diseases receive considerable public attention, healthy assistance animals receiving routine veterinary care, vaccinations, parasite prevention, appropriate grooming and regular health monitoring present a very low risk of transmitting infectious diseases. Occupational Therapists should therefore base infection prevention decisions on individual risk assessments rather than assumptions about animals.

Zooanthroponoses (Human-to-Animal Transmission)

Zooanthroponoses, also known as reverse zoonoses, are diseases naturally transmitted from humans to animals.

Increasingly, research demonstrates that humans can transmit a range of infectious diseases to companion animals, including assistance dogs and cats. Because assistance animals often spend prolonged periods in close physical contact with their handlers, protecting animals from human illness is an important component of animal welfare and infection prevention.

Examples include:

• COVID-19 (SARS-CoV-2)
• influenza
• methicillin-resistant Staphylococcus aureus (MRSA)
• tuberculosis (rare)
• certain fungal infections.

Occupational Therapists should encourage clients who are experiencing infectious illnesses to practise appropriate hygiene, minimise unnecessary close contact where appropriate, and seek veterinary advice if an assistance animal becomes unwell following exposure.

Protecting assistance animals from infectious disease supports both animal welfare and the long-term effectiveness of the assistance animal partnership.

Amphixenoses (Bidirectional Transmission)

Amphixenoses are infectious diseases that may be transmitted in either direction, with humans and animals acting as reservoirs capable of infecting one another depending on the circumstances.

The direction of transmission depends on factors including:

• the infectious agent
• host susceptibility
• environmental conditions
• frequency of contact
• immune status
• hygiene practices.

Although amphixenotic diseases are less commonly discussed in everyday clinical practice, they reinforce the importance of viewing disease transmission as a dynamic interaction between humans, animals and the environment rather than assuming that infection always originates from animals.

Understanding bidirectional disease transmission supports more balanced clinical reasoning and encourages collaborative approaches to infection prevention.

Sapronoses (Environment-to-Human or Environment-to-Animal Transmission)

Not all infectious diseases originate from humans or animals. Sapronoses are diseases acquired from environmental reservoirs where microorganisms survive or multiply outside a living host.

Environmental reservoirs may include:

• soil
• water
• decaying vegetation
• organic matter
• contaminated environmental surfaces.

Examples include:

• Legionella species
• certain fungal infections such as aspergillosis.

Although sapronoses are not transmitted directly between humans and animals, they remain highly relevant to Occupational Therapy because both clients and assistance animals regularly interact with shared environments. Maintaining clean, well-managed therapy environments is therefore an important component of infection prevention.

Common Infectious Diseases Relevant to Assistance Animal Practice

Although the likelihood of disease transmission from healthy assistance animals is low, Occupational Therapists should be familiar with several infectious diseases that may occasionally be encountered.

Ringworm (Dermatophytosis)

Ringworm is a fungal infection affecting the skin, hair and nails. Despite its name, it is not caused by a worm.

Transmission occurs through:

• direct contact
• contaminated grooming equipment
• bedding
• environmental surfaces.

Prompt veterinary treatment and environmental cleaning substantially reduce transmission.

Salmonellosis

Salmonella bacteria are commonly associated with contaminated food and faecal contamination.

Transmission may occur through:

• inadequate hand hygiene
• contaminated food
• contact with infected faeces.

Routine hygiene practices effectively minimise transmission risk.

Campylobacteriosis

Campylobacter bacteria may be carried by healthy animals and transmitted through the faecal–oral route.

Good hand hygiene following contact with animal waste is highly effective in preventing transmission.

Giardiasis

Giardia is a microscopic parasite affecting both humans and animals.

Transmission generally occurs through contaminated water or faecal contamination.

Routine parasite prevention and prompt treatment reduce risks.

Toxoplasmosis

Toxoplasma gondii is a parasite commonly associated with cats.

Human infection most frequently occurs through:

• consuming undercooked meat
• handling contaminated soil
• cleaning cat litter.

Contrary to common misconceptions, living with a healthy indoor cat presents a very low infection risk when appropriate hygiene practices are followed.

Leptospirosis

Leptospirosis is a bacterial disease transmitted through contact with infected urine or contaminated water.

Vaccination is available for dogs in Australia and forms part of preventive veterinary healthcare where appropriate.

Rabies

Australia remains free of terrestrial rabies, making the disease extremely unlikely within Australian assistance animal practice.

However, Occupational Therapists should understand rabies because it remains globally significant and may be relevant when working internationally or with imported animals.

Who Is Most at Risk?

Susceptibility to infectious disease varies considerably.

People at increased risk include:

• infants and young children
• older adults
• pregnant individuals
• people receiving chemotherapy
• transplant recipients
• individuals with immunodeficiency
• people taking immunosuppressive medications
• individuals with poorly controlled chronic disease.

Similarly, assistance animals that are:

• very young
• elderly
• pregnant
• immunocompromised
• recovering from illness

may also have increased susceptibility to infection.

Occupational Therapists should consider the health of both the client and the assistance animal during infection risk assessments.

Preventing Disease Transmission in Assistance Animal Practice

Disease transmission can be greatly reduced through routine preventive healthcare and evidence-informed infection prevention strategies.

Maintaining Animal Health

• routine veterinary examinations
• vaccinations
• parasite prevention
• dental care
• grooming
• prompt treatment of illness
• maintaining appropriate body condition.

Maintaining Human Hygiene

• effective hand hygiene
• respiratory hygiene
• safe waste disposal
• wound care
• avoiding unnecessary exposure to bodily fluids
• appropriate use of personal protective equipment where indicated.

Environmental Hygiene

• cleaning shared equipment
• disinfecting contaminated surfaces
• laundering bedding
• maintaining clean therapy environments
• safe food storage
• appropriate waste management.

Education

Occupational Therapists play an important role in educating:

• clients
• carers
• support workers
• schools
• workplaces
• healthcare providers

about realistic infection risks and appropriate prevention strategies.

Education should emphasise evidence rather than fear and reinforce that healthy assistance animals receiving appropriate veterinary care present a very low infection risk.

The Occupational Therapist’s Role

Occupational Therapists are not responsible for diagnosing infectious diseases in either humans or animals. However, they play an important role in recognising potential biological hazards, implementing appropriate infection prevention measures and facilitating referral when concerns arise.

This includes:

• recognising signs of potential infectious illness
• undertaking evidence-informed infection risk assessments
• modifying service delivery where appropriate
• referring clients to medical practitioners
• encouraging veterinary assessment for unwell assistance animals
• educating clients regarding infection prevention
• supporting occupational participation through reasonable adjustments
• advocating against discriminatory restrictions unsupported by scientific evidence.

Occupational Therapists should always practise within their professional scope while collaborating with veterinary and medical professionals.

Applying One Health Principles

Understanding the different patterns of disease transmission reinforces that infection prevention should focus equally on protecting human health, animal health and environmental health.

Occupational Therapists should consider:

• the health status of the client
• the health status of the assistance animal
• environmental conditions
• the characteristics of the infectious agent
• current public health advice
• veterinary recommendations
• available scientific evidence.

This balanced approach supports evidence-informed decision-making while promoting safe, inclusive and ethical occupational therapy practice.

Key Practice Principle

Occupational Therapists working with assistance animals should understand that infectious diseases may be transmitted from animals to humans, from humans to animals, between both populations, or through shared environmental reservoirs. Applying a One Health perspective enables practitioners to undertake comprehensive, evidence-informed risk assessments that protect the health and welfare of clients, assistance animals and the wider community while supporting safe, inclusive and meaningful occupational participation.