1 Sept 2026
Ian Wright BVMS, BSc, MSc, MRCVS covers some of “the usual suspects” that are of risk to pets and owners, and some preventive measures vets can recommend to clients who are planning to go abroad.
Ian Wright
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Since the UK Government’s Pet Travel Scheme (PETS) was relaxed in 2012, travelling with cats and dogs abroad on recreational trips has increased and, barring COVID-19 restrictions, remained consistently popular.
This trend has occurred at a time of increased human and pet migration alongside changes in climate and land management, all contributing to increased distributions of many parasites and their vectors. This means an increased risk of pets and their owners encountering exotic parasites while abroad.
Official veterinarians (OVs) are in a privileged position of providing the documentation for clients to be able to travel with their pets abroad, providing an opportunity to ensure that appropriate parasite prevention advice is given. This is based on lifestyle while abroad and the parasites likely to be encountered.
Some of these parasites are “the usual suspects” forming the core of pet travel advice and will be familiar to UK vets and nurses involved with pet travel clinics.
Echinococcus multilocularis, Dirofilaria immitis (heartworm), Leishmania infantum and tick-borne pathogens form the basis of this advice due to their pathogenicity or zoonotic risk.
Echinococcus multilocularis, the cause of cystic echinococcosis, is a severe zoonosis and is widespread throughout Europe.
The adult tapeworm is carried by both foxes and domestic canids, with foxes and other wild canids acting as a reservoir of infection. Rodents such as microtine voles are intermediate host reservoirs, although a wide range of mammals including humans may act as intermediate hosts. Canids become infected by predation of intermediate hosts, with infection in dogs bringing the parasite into close proximity to people.
Cats can act as definitive hosts for E multilocularis, but have a lower worm burden with lower fecundity than canids.
In the 1980s, human alveolar echinococcosis was vanishing from Europe due to improved food hygiene, decreased occupational risk of exposure and a decimated fox population following a number of rabies epidemics.
The control of rabies in western and central Europe, however, reversed this trend, as the fox population rapidly increased and expanded into urban areas (Deplazes et al, 2003). The parasite is now widespread across Europe. It has established endemic foci in Denmark, Sweden and the north-western coast of France.
Only the UK, Ireland, Malta, Finland and Norway have official endemic-free status in Europe.
E multilocularis infections in felids and canids are almost always subclinical, even when heavy worm burdens are present, and is of no clinical significance in infected pets.
Zoonotic infection occurs through ingestion of eggs passed in the faeces of dogs and foxes. This can occur though association with infected dogs, through contamination of public spaces through dog fouling or though eating contaminated fruit and vegetables intended for raw consumption.
Zoonotic infection results in local and metastatic spread of cysts, leading to hepatopathy and potential multiple organ involvement. Despite significant advances in treatment, infected individuals can still expect a significant reduction in life expectancy.
Although E multilocularis is not currently endemic in the UK, the increase in pet travel across UK borders and relocation of dogs from endemic countries increases the risk of establishment.
If E multilocularis enters the UK via infected animals then the large fox and vole populations will make the prevention of E multilocularis becoming endemic difficult if not impossible to achieve (Deplazes et al, 2003). It is, therefore, vital that the opportunity for the parasite to gain entry to the UK is kept to a minimum.
Treatment with praziquantel is still a legal requirement between one and five days before entry to the UK. This simple treatment has so far prevented endemic foci from developing and remains vital.
The current one to five-day treatment window, however, does allow opportunity for infection before return to the UK. All travelled dogs should, therefore, receive an additional praziquantel treatment within 30 days after arrival in the UK. Cases of infection in cats are uncommon, but have been reported so should also be treated.
The prepatent period of E multilocularis is at least 30 days, so dogs travelling abroad for more than 30 days should also be treated monthly with praziquantel to help keep pet owners safe from infection while abroad. Preventing pets from roaming off lead where they may predate rodents or other intermediate hosts will also reduce the risk of infection.
Dirofilaria immitis is a filarial heartworm primarily of canids, but also can infect ferrets and felines.
Transmission occurs through feeding by infected mosquitoes.
D immitis is endemic throughout southern and most of eastern Europe. Although the mosquito vector is endemic in most European countries, including the UK, a colder climate in northern Europe has prevented heartworm from becoming endemic.
Climate change, however, means this is likely to change and allow further expansion of the parasite’s range northwards in Europe over time.
D immitis is a significant cause of heart disease.
Infections may remain subclinical for months or years before potentially severe signs develop associated with chronic heart changes, adult worm death, thromboembolism, and inflammatory responses associated with larval worm migration.
Although aberrant migration of larvae can occur in human hosts, zoonotic exposure is through the feeding of infected mosquitoes, and infected pets are of no direct risk to humans.
Cats, dogs and ferrets travelling to endemic countries should be treated monthly with a licensed macrocyclic lactone product (moxidectin in ferrets; milbemycin, moxidectin or selamectin in cats and dogs; eprinomectin in cats). These are highly effective as preventive treatments.
Use of a licensed pyrethroid fly repellent in dogs and avoiding walking at peak mosquito feeding times will also act as a useful second line of defence, but should not be used as a substitute for macrocyclic lactone prevention.
Leishmaniosis is caused by intracellular protozoan parasites of the genus Leishmania, with L infantum being the predominant species in European cats and dogs. Transmission occurs primarily through bites from infected phlebotomine sandflies.
Although small foci of Leishmania can be maintained by non-vectorial routes such as blood transfusion, congenital and venereal transmission, the distribution of L infantum is largely dependent on its sandfly vector.
This currently limits the European distribution of the parasite to the south of France, southern and parts of eastern Europe, although this distribution is expanding.
Transmission occurs seasonally and in geographic foci in many countries, making local knowledge invaluable as to where transmission is taking place.
The signs associated with Leishmania infection are immune mediated and in dogs commonly include lymphadenopathy, anorexia, weight loss, dermatological signs (alopecia, dermatitis, hyperkeratosis or dermal ulcers), ocular signs (conjunctivitis or uveitis) and epistaxis without thrombocytopenia. Thrombocytopenia and anaemia, polyarthritis and splenomegaly can also occur. Immune complexes in the kidneys lead to glomerular nephritis. The time period between initial infection to development of clinical leishmaniosis is highly variable, ranging from months to several years.
Human cases of leishmaniosis occur in endemic countries due to infected sandfly bites and, to the author’s knowledge, human infection by L infantum in an immunocompetent patient by direct dog content has never been confirmed.
Direct transmission via open sores or wounds is theoretically possible, though, and good hygiene around infected pets should be advised.
Preventive measures are essential for pets travelling to endemic countries. Sandflies feed at night with the greatest activity at dawn and dusk, so avoiding outdoor activity at these times helps to prevent exposure. They are also poor flyers, so if camping outdoors, then choosing breezy locations is also advantageous.
Some exposure to bites is likely, however, even if these precautions are taken, and so the use of licensed pyrethroid products with “knock-down” capabilities to minimise fly bites flies are required. A range of spot-on preparations are licensed for fly repellency, as well as one collar (Scalibor; MSD Animal Health). Good evidence also exists to suggest that flumethrin (available in a collar) has some efficacy. Although the flumethrin collar is not licensed for this purpose in cats, it is the only safe product available for felines, where products containing other pyrethroids are not an option.
Treatment should be applied one week before travel, as pyrethroids take time to reach full distribution and activity.
Although canine vaccines are available to reduce disease from Leishmania infection in some European countries, no vaccine is available in the UK. Owners spending many weeks or months each year in endemic countries with their pets should consider arranging vaccination while abroad.
Pets travelling abroad may be exposed to a range of tick-borne pathogens not endemic in the UK.
Babesia canis has spread both northwards and southwards across Europe, and is now endemic on most of the continent. Tick-borne encephalitis virus transmitted by Ixodes species ticks has also spread rapidly throughout most of Europe this century.
The tick Rhipicephalus sanguineus, which can transmit a range of tick-borne pathogens including Ehrlichia canis and Hepatozoon canis, has been restricted to warmer climates in southern and eastern Europe. In recent years, however, a warming climate and pet movement have encouraged its spread throughout eastern Europe, and it is gradually moving northwards. Although it is unlikely that R sanguineus would currently establish outdoor endemic populations in the UK, it can complete its life cycle quickly feeding on a variety of hosts. This allows it to infest centrally heated UK homes in a similar way to fleas (Hansford et al, 2015; Hansford et al, 2017).
Tick-borne infections commonly present acutely with lymphadenopathy and pyrexia. A range of tick-borne pathogens can also lead to neurological signs, immune-mediated haemolytic anaemia and thrombocytopenia.
Tick-borne pathogens should be considered as differentials in pets presenting with any of these signs and a history of foreign travel. Chronic ehrlichiosis in dogs may occur months or years after travel.
Pets infected with tick-borne pathogens do not pose a direct risk to owners, but they may also be exposed to ticks and zoonotic disease. These include pathogens such as Rickettsia conorii carried by R sanguineus, and tick-borne encephalitis transmitted by Ixodes species ticks.
Pets should be treated with an effective tick product before and during travel, as well as on entry to the UK.
If travelling to L infantum or R sanguineus endemic countries, this product should be a licensed pyrethroid repellent. Isoxazolines are also highly effective treatments (as well as tigolaner for cats) for ticks.
While these products are highly efficacious, they are not 100 per cent effective, so monitoring for ticks after outdoor activity and careful removal with a tick removal device should also be advised. Staying on paths where possible and avoiding tall vegetation will also reduce the risk of exposure.
While “the big four” (heartworm, tick-borne pathogens, Leishmania and Echinococcus) are the most important parasites to ensure protection is in place against, a wide range of other parasites may be encountered.
Examples include the following.
Dirofilaria repens. This parasite is closely related to D immitis, with adult worms living in skin nodules and subcutaneous tissues rather than the cardiovascular system. The mosquito vectors for D repens are already endemic in the UK, and D repens appears to have less stringent temperature requirements for development than D immitis. This means that it is more likely to establish in the UK (Morgan, 2016). Definitive hosts are carnivores including dogs and cats. Humans can also be infected through being exposed to mosquito bites. Infection can be subclinical or lead to dermatitis and skin nodules. Less commonly, adult worms migrate to the eyes of the host, where they may be visible and cause ocular signs. Prevalence of dirofilariosis in cats tends to be only one-tenth of that in dogs and typically occurs in areas of high canine infection rates. Its distribution across Europe is widespread. Moxidectin/imidacloprid spot-on preparations are licensed preventive treatments and should be considered when dogs are travelling to endemic countries where D immitis is not present and a routine macrocyclic lactone preventive would not ordinarily be used.
Thelazia callipaeda. Also known as the “oriental eye worm” this is a zoonotic vector-borne nematode that resides in the conjunctival sac of definitive hosts including domestic and wild carnivores, rabbits and humans. The parasite is found widely in Asia and has been spreading through Europe in recent years. This has been driven largely with pet movements coinciding with a widening distribution of its Phortica species fruit fly vector. The parasite is transmitted when fruit flies feed on lacrimal secretions. Although often subclinical, ocular thelaziosis can commonly cause conjunctivitis, keratitis, epiphora, eyelid oedema, corneal ulceration and, in serious cases, blindness. Although, in domestic pets, it is predominantly a parasite of dogs, clinical cases of ocular thelaziosis in cats have also been reported in many endemic countries (Mihalca et al, 2015). The Phortica variegata intermediate host has been reported in the south of England, presenting the possibility for establishment of the parasite in these vector populations (Morgan, 2016). No product is licensed for prevention, but milbemycin oxime/praziquantel tablets and moxidectin/imidacloprid spot-on preparations have treatment licences and, therefore, may have some efficacy in prevention of infection.
Parasites transmitted via food and predation. Tapeworms, flukes and the nasal pentastomid Linguatula serrata may all be transmitted by the consumption of raw or undercooked meat, fish and offal. Where possible, feeding these items to pets while abroad should be avoided. Similarly, these parasites may be transmitted via scavenging food items or predation. No recognised preventative treatment for L serrata exists, but macrocyclic lactones may be effective if exposure is suspected. Praziquantel, which will be administered before return home, will be effective against most tapeworms and flukes.
A consistent strategy is required to keep travelling pets and their owners safe form exotic parasitic disease. The following should always be considered.
Countries being visited. The parasites present in countries being visited need to be considered and preventive measures put in place. This includes countries being travelled through, as well as the destination of travel. Prevalence maps are available for E multilocularis, D immitis, D repens, Leishmania species and R sanguineus on the European Scientific Counsel Companion Animal Parasites website (www.esccap.org/guidelines-maps). Case reports are useful in untravelled pets, and local knowledge from veterinary practices and charities in destination countries can be invaluable in understanding local foci and seasonality.
Lifestyle and owner preference. Frequent swimming and shampoo will affect the duration of efficacy of some products, so datasheets need to be checked where this is a consideration. Owner preference and ability to apply different types of products, such as tablets and spot-on preparations, should also be considered.
Use of products that protect against multiple parasites. This reduces the number of products that clients have to apply while on holiday. Fly-repellent products will also be efficacious against ticks. Products are available for combing heartworm and tapeworm prevention or heartworm and tick prevention where this is relevant, and fits in with owner compliance and overall requirements.
Increased movement of pets and fluid vector and parasite distributions in Europe make protecting UK pets and owners from exotic disease increasingly challenging.
OVs and their teams are on the front line of maintaining biosecurity and keeping pets safe while abroad. It is important, therefore, for veterinary professionals to be prepared to give accurate travel advice to clients and remain up to date with latest parasite distributions in Europe.
In doing so, pet and human health will benefit, and the risk of entry of novel parasites into the UK can be reduced.
Ian Wright is a practising vet and co-owner of The Mount Veterinary Practice in Fleetwood, Lancashire. He has a master’s degree in veterinary parasitology and is chairman and director of the European Scientific Counsel Companion Animal Parasites (ESCCAP), as well as guidelines director for ESCCAP Europe.