Working in veterinary practice puts both veterinary surgeons and veterinary nurses in contact with potentially zoonotic parasites. These pathogens may be transmitted through direct contact with pets, indirect surface transmission, aerosols or via vectors. Examples of pathogens transmitted through direct and indirect contact are dermatophytes (ringworm), mites (Sarcoptes, Cheyletiella), Bartonella spp. (via flea faeces) and Brucella canis. Bacteria such as Brucella spp., Bartonella spp. and Bordetella spp. may also be transmitted via the aerosol route. Fleas can easily become established in practices leading to flea-borne pathogen transmission, such as Rickettsia felis. Ticks are unlikely to become established indoors in the UK, but detached unfed Ixodes ticks can bite staff leading to potential transmission of Borrelia spp, Anaplasma phagocytophilum and tick-borne encephalitis virus.
The risk of zoonotic parasite transmission, however, can be minimised in the workplace with a few simple practice-wide precautions.
Bite and scratch prevention from cats and dogs
Bites and scratches leading to compromise of the skin barrier can in turn, lead to the introduction of bacteria and ringworm. Cat bites and scratches are a particular risk for Bartonella henselae (the cause of cat scratch disease) transmission via flea faeces trapped under nails or in saliva (Bouhsira et al, 2013). Planning and use of adequate restraint is vital before procedures are carried out on pets. Recording history of previous biting or scratching behaviour and history taking from owners regarding temperament are all important in the planning stage but cannot be wholly relied on. A risk assessment should be made as to whether muzzling, wrapping, sedation or anaesthesia are required. Some patients are more easily handled and less aggressive away from their owners and this may be established from the patient's history or through discussion with the owner. Safe and effective animal handling requires reading the pet's body language and a few moments should be taken to visually assess the patient before handling is initiated.
Signs of anxiety in dogs include the ears being flat against the head, the tail being between the legs, hackles being raised, growling or whining. It should not be assumed that an animal that is demonstrating submissive signs will not be aggressive. Apparent submissive gestures can be attempts at appeasement to reduce threat, which if ignored, can lead to aggression. Typical appeasement gestures include yawning, gaze aversion, lip licking, slow tail wagging and lifting of a paw. If dogs are frightened or concerned, they may shake, stretch, or cling to their owner. If these signs are ignored or greater levels of anxiety reached the prelude signs to aggression include a high chin with throat exposed, hard staring, freezing, and growling (Lloyd, 2017).
Signs of stress and anxiety in cats include flattening ears, wide open eyes with pupils dilated and hypervigilance. Signs that anxiety is progressing to potential aggression include the eyes being fixed on potential threat, growling, hissing and striking out with the front feet (Lloyd, 2017).
If cats and dogs are exhibiting these signs, they should be approached with confidence but caution. Before starting to handle patients, any equipment required should be readily available and the reason for the visit established. If the patient is in pain, then this may increase the chance of aggressive behaviour, especially if the affected area is handled. A moment should be taken to allow the animal to become comfortable with people in the room and the environment. It should be spoken to in a calm, quiet voice and if known, their name should be used to increase familiarity. Eye contact should be avoided, and movement should be slow but confident. Sudden movements may provoke aggression, particularly sudden vertical movements across the retina. Food can be a useful tool in relationship building and as a distraction. If being placed in kennels, potentially aggressive patients should not be placed in kennels at face height and should have a warning sign placed on the kennel door.
Having assessed the patient's body language, history, and after discussions with carers or owners, it may be decided that further restraint or protection is required. Muzzles are essential with many aggressive dogs and must be the correct size. It should be placed from behind and fastened behind the dog's head. Towels are also useful to restrain cats and small dogs, especially brachycephalic breeds where muzzles can be difficult to keep in place. The towel can either be rolled up and placed around the animal's neck or wrapped around cats, allowing access to the head or individual limbs as required. Muzzles designed specifically for use in brachycephalic dogs are now available, making muzzling these breeds more of a viable option. For particularly fractious or aggressive cats and dogs chemical restraint may be required. Crush cages are useful for injecting cats with sedatives, if the risk of other forms of handling is deemed too great.
Handwashing
Consistent, thorough handwashing is the single most important measure to reduce the risk of pathogen transmission. Handwashing is superior to the use of alcohol-based lotions and handwipes as these have difficulty penetrating organic material such as blood and faeces. Injuries should always be immediately and thoroughly washed to minimise contamination. Even short delays can allow pathogens, such as ringworm and Bartonella spp., to establish. Liquid or foam soap is preferable to bar soap to prevent cross contamination. The use of moisturising soaps or moisturising after washing helps to maintain a healthy skin barrier.
Personal protective equipment
Gloves should be worn when handling any animal with evidence of skin disease, open wounds or ectoparasite infestation (especially fleas because of Bartonella spp. transmission risk via flea faeces). Gloves should always be worn when contact with faeces, blood, urine or other body fluids is likely. Gloves should be changed between examinations of individual animals or litters of puppies or kittens. Contact between the skin and the outer glove surface should be avoided during removal. Hands should be washed as soon as the gloves are removed to eliminate any potential contamination. Facial protection should be worn whenever exposure to splashing fluid or sprays is likely, such as when flushing wounds and during post-mortem examinations. This may take the form of a face mask and goggles or a full facial shield. Protective outerwear, such as gowns or if unavailable, aprons, are vital when caring for, or examining patients with suspected or confirmed zoonotic infections. Contaminated clothes should be promptly changed if soiled.
Concerns have arisen around the increasing numbers of imported dogs being found to be carrying Brucella canis, a Gram-negative zoonotic bacteria (Middlemiss, 2021). Infection in domestic dogs is typically associated with reproductive abnormalities including infertility, abortion, endometritis, epididymitis and orchitis and scrotal oedema. A wide range of non-reproductive conditions can also occur though including chronic uveitis, endophthalmitis, and discospondylitis. Lymphadenitis is common along with non-specific clinical signs, such as lethargy, exercise intolerance, decreased appetite and weight loss. The consequences of zoonotic exposure, however, can be significant, especially in the immune suppressed. Serious complications in humans include septic arthritis, osteomyelitis and endocarditis. Vigilance for the infection in imported dogs is therefore vital both to reduce zoonotic risk for veterinary staff and pet owners, as well as minimising the risk of endemic foci developing in the UK.
Transmission occurs via reproductive fluids but B. canis is also shed in urine, blood, and saliva and imported dogs with relevant clinical signs should therefore be handled with appropriate personal protective equipment (PPE).
Disinfection of surfaces
After carrying out procedures resulting in aerosol contamination or after surface contact with bodily fluid, flea dirt (Figure 1) or potentially contaminated shed or clipped fur, surfaces should be disinfected. Gloves should be worn while disinfecting potentially contaminated surfaces with zoonotic agents. Disinfectants licensed for use in veterinary practices often contain a combination of active ingredients for antiviral and antibacterial efficacy. The use of quaternary ammonium compounds will be required for efficacy against Giardia cysts.
Vector control
Tick and flea bites are an underestimated source of pathogen transmission in veterinary practice. Although Ixodes spp. ticks are unlikely to become established in veterinary practices, many wildlife casualties as well as cats and dogs exposed to large numbers of ticks are likely to have unfed adults and nymphs in their coats. These may easily be brushed off into the environment or onto veterinary staff. Once attached, if not removed quickly, then ticks may transmit a number of zoonotic UK tick-borne pathogens including Borrelia spp, tick-borne encephaltitis virus, small Babesia spp. and Anaplasma phagoctophylum.
Veterinary staff should check themselves for ticks after handling heavily infested pets or wildlife casualties such as hedgehogs, which may have many unattached nymphs on their bodies which are only a few millimetres long (Figure 2). Checking should ideally be performed as soon as possible but if ticks are found and removed within 24 hours this will significantly reduce the risk of pathogen transmission.
Any ticks removed or found in veterinary premises should be identified. This is important as it will indicate which tick-borne pathogens the tick was potentially able to transmit and whether infestation of the practice is likely. In the case of Ixodes spp. and Dermacentor reticulatus this is not a concern, but in the case of Rhipicephalus sanguineus, then this is a significant possibility. R. sanguineus may be present on travelled pets with subsequent transfer into the practice environment. If this is suspected then treatment of the environment with pyrethroids will be required and in the case of established infestations, professional pest control.
Ticks may be identified using the tick University of Bristol tick identification site http://www.bristoluniversi-tytickid.uk
Public Health England are also happy to receive ticks for identification. Ticks should be placed in a container with a secure lid and sent in an envelope marked ‘biological sample’ and sent to:
- Tick surveillance scheme
- Public Health England
- Porton Down
- Wiltshire
- Salisbury
- SP4 0JG.
Tick surveillance forms and further information can be obtained from The Gov.UK website under ‘tick surveillance’.
Ticks can be analysed for tick-borne pathogens by polymerase chain reaction (PCR), but this is of limited value as false negative results can occur, and even if positive, does not give information about the individual tick's transmission status. It should be assumed that any tick found attached, may have transmitted any of the tick-borne pathogens transmitted by that tick species which are endemic in the country of origin.
Cat fleas (Ctenocephalides felis) are a source of human irritation, bite reaction and can transmit zoonotic pathogens such as B. henselae and R. felis. C. felis is the most common flea found on domestic cats and dogs (Bond et al, 2007; Abdullah et al, 2019) because of its adaptation to the environmental conditions in human households and ability to live on a wide range of mammals including cats, dogs, humans, rabbits and ferrets. This means infested pets and wildlife casualties are likely to be regular visitors to veterinary practices with the potential for cat flea infestations to establish. Discovery of fleas away from animals and flea bites (Figure 3) indicate possible infestation. Flea infestations in practice can be treated using insecticide/growth regulating sprays. It is important to examine any flea found in the practice under the microscope to distinguish them from fleas of wildlife. This can be achieved by examining the head of the flea. The head of adult fleas may bear a posterior (pronotal) or ventral (genal) row of dark spines known as combs (ctenidia, Figure 4) and it is the presence, absence, shape and position of these combs that is the primary means of differentiating fleas to genus, and sometimes species level. Cat fleas have both genal and pronotal combs and a characteristic elongated head, with the head being twice as long as it is tall. In bird fleas (Figure 5) and fleas of rodents and badgers (Figure 6), the pronotal combs are present but genal combs are absent. Bird and rodent fleas may come from nests in or adjoining the practice and require the source of the infestation to be identified and treated or removed.
Conclusion
While not receiving as much attention as zoonotic infection in the workplace from viruses, MRSA and food-borne bacterial pathogens, parasites and vector-borne pathogens pose as significant risk. General principals of hygiene, protective clothing, safe animal handling and pest control will keep veterinary nurses and the wider veterinary practice team safe.
KEY POINTS
- The veterinary workplace puts veterinary professionals in contact with potentially zoonotic parasites.
- Parasites may be transmitted through direct contact with pets, indirect surface transmission, aerosols or via vectors.
- The introduction of pathogens via scratches and bites can be minimised by pre planning interactions with animals, reading body language, and using adequate restraint where necessary.
- Excellent hand hygiene, appropriate use of personal protective equipment and disinfectants will reduce the transmission risk of many pathogens in practice.
- The risk of vector-borne transmission in practice should not be under estimated and the risk of tick and flea exposure minimised.