Pet travel is not new, but in recent years the patterns and consequences of that movement have changed. Before the Pet Travel Scheme, only a small minority of UK pets ever left the country. The introduction of pet passports saw pet travel increase and despite post-Brexit changes, many owners still choose to take their pet abroad. At the same time, the importation of dogs from countries where vector-borne diseases (VBD) are endemic continues at scale. In 2024, 5% of dogs owned for one year or less were acquired from abroad, equating to around 82,000 dogs imported for pet ownership in a 12 month period.¹

Add to this the effects of accelerating climate change. Warmer, wetter seasons have extended vector activity across Europe and the UK, and together these trends mean we are now encountering vector-borne diseases that were once confined to more distant shores.

Whether screening an imported dog, investigating non-specific illness in a recently travelled animal or exploring unusual clinical signs, laboratory diagnostics play a central role in vector-borne disease prevention, surveillance and control. Learn more about our Histology and Cytology service here.

What are vector-borne diseases (VBDs)? VBDs are caused by infectious agents transmitted to animals via Insecta and Acari vectors.²

Understanding vector-borne disease

Vector-borne diseases are caused by a wide range of infectious agents, including viruses, bacteria, protozoa and helminths. Key vectors include ticks, mosquitoes and flies.² Globally, ticks are responsible for the majority of VBD transmission – around 95% of cases in one study – and their geographic range is continuing to expand.³ For UK travelling pets tick-borne pathogens are one of the principal concerns, alongside important non-tick-borne infections such as Dirofilaria immitis (heartworm), transmitted by mosquitos, and Leishmania infantum, transmitted by sandflies.^4,5 Emerging or less familiar vector-borne pathogens include Thelazia callipaeda, the eyeworm, transmitted by Phortica variegata (a fruit fly of the Drosophilidae family).

Imported dogs

Imported dogs add further complexity. Many arrive from southern and eastern Europe where exposure to Babesia canis, Ehrlichia canis, Anaplasma platys, Hepatozoon canis and Borrelia burgdorferi is commonplace. Some of these pathogens can establish carrier states, with animals appearing clinically normal on arrival but capable of developing clinical disease weeks or months later. This highlights the importance of a thorough travel and importation history.

Clinicians are therefore encountering pathogens once considered rare or “exotic.” Some, such as Leishmania infantum, are unlikely to establish in the UK due to the absence of sand fly vectors. Others, particularly tick- and mosquito- associated pathogens, are far more adaptable. Even without considering more exotic tick species, the UK is already home to at least 20 native tick species,6 with Ixodes ricinus (commonly known as the sheep or deer tick) being the most widespread and relevant to veterinary and public health (Table 1).

Tick species	UK presence	Pathogens transmitted
Ixodes ricinus (the sheep tick)	Endemic across the UK	Borrelia burgdorferi; Anaplasma phagocytophilum
Dermacentor reticularis (the ornate dog tick)	Established foci in Wales, Devon, Essex, London	Babesia canis
Rhipicephalus sanguineus (brown dog tick)	Imported on dogs; survives indoors	Hepatozoon canis; Ehrlichia canis; Anaplasma platys

Table 1. Key tick species in the UK and the pathogens they transmit.

Clinical signs and diagnostic screening

Tick-borne diseases are challenging to diagnose based on clinical signs alone, especially as infections may be subclinical. When clinical disease is present, signs can range from mild and non-specific – such as lethargy, pyrexia and lymphadenopathy – to severe and life-threatening.

Babesiosis, for example, may result in icterus due to intravascular haemolysis, with potential complications including prolonged bleeding, petechiae or ecchymoses and neurological signs. A thorough diagnostic work-up, including routine biochemistry and haematology (box 1), is essential to identify the underlying cause and guide treatment.

Box 1: Haematological and biochemical abnormalities in tick-borne disease

• Anaemia
• Thrombocytopaenia
• Prolonged clotting times
• Azotaemia
• Elevated liver enzymes
• Hypoalbuminaemia
• Hyperglobulinaemia

Patient-side testing

In some cases, patient-side point-of-care tests will be the next diagnostic step. In-house assays are readily available and can provide useful initial information. However, most patient-side tests for vector-borne disease detect antibodies rather than the pathogen itself. As a result, they primarily indicate prior exposure rather than active infection.

Test timing is also critical. In the early stages of infection, dogs may test negative due to the lag between exposure and seroconversion, which can extend to three weeks or more.7 Where results are equivocal, unexpected or inconsistent with the clinical picture, further investigation is warranted.

The role of PCR in diagnosis

Quantitative polymerase chain reaction (qPCR) testing is therefore an essential tool in the investigation of suspected vector-borne disease, particularly in dogs that have travelled abroad or been imported from endemic regions. Unlike serology, which reflects an immune response to exposure, PCR detects pathogen DNA and confirms active infection at the time of sampling.

qPCR assays are highly sensitive and specific, and when used early in the disease course, can detect infection before an antibody response occurs. Many veterinary laboratories offer pathogen-specific or multiple tick-borne disease (multiplex) panels, allowing simultaneous testing for Babesia, Ehrlichia, Anaplasma and Hepatozoon spp. from a single EDTA blood sample – an approach that is particularly helpful when investigating dogs with vague signs or complex travel histories.

As with all diagnostic tools, PCR results must be interpreted in context. A positive result provides strong evidence of active infection, while a negative result does not always exclude disease, particularly if sampling occurs very early, or if the pathogen is localised within tissues, rather than circulating in peripheral blood. In such cases, repeat testing, alternative sample types or further discussion with the diagnostic laboratory may be required.

Disease-specific diagnostic considerations

While diagnostic principles are broadly similar for most vector-borne infections, individual pathogens present distinct challenges, related to factors including tissue distribution and timing of diagnostic testing. Understanding these differences helps clinicians select appropriate tests and interpret results accurately.

The article continues beyond this point.

Read the full article https://www.vettimes.com/clinical/small-animal/disease-diagnostics-and-travel

Original publication: Vet Times (2026), Volume 56, Issue 10, Pages 5-9

About the author

Sandra Wells holds a BSc(Hons) in Applied Biology with Biochemistry from Coventry University and a postgraduate qualification in Molecular Biology from Lancaster University. Throughout her career, she has held senior roles including head of biochemistry, laboratory manager and group quality manager. At NationWide Laboratories, Sandra oversees operations across all sites, strengthening service quality and advancing diagnostic capability to ensure the organisation remains equipped to meet evolving veterinary challenges, from emerging vector-borne diseases to the increasing complexity of modern clinical diagnostics.