Are ticks a potential vector for Borna disease virus?

Background
Borna disease virus (BDV) has a broad host range including cats and dogs. In cats BDV causes a non-suppurative
meningoencephalomyelitis called “staggering disease”. The mode of transmission is not known but it does not
appear to be readily transmitted between cats. Vectors such as ticks may play a role in transmission and access to
forested areas was reported as an important risk factor for staggering disease, so access to vectors such as ticks may be involved in transmission. Ticks have not yet been evaluated as a potential vector for BDV. We have access to nucleic acid extracts prepared from ticks collected directly from cats as hosts as well as directly from vegetation. This offers us the unique and timely opportunity to evaluate ticks for the presence of BDV RNA by reverse-transcriptase polymerase chain reaction (RT-PCR) assays. Evaluation of ticks for BDV will provide insight into their possible role in the transmission of BDV to cats. Such findings would likely be transferable to other hosts for BDV too.

Aims
To determine if ticks are likely to be play a role in the transmission of BDV, especially in cats

Objectives
To determine if BDV RNA is present in fed identified tick species collected from cats in the UK and in Switzerland
using BDV RT-PCR
To determine if BDV RNA is present in unfed identified tick species collected from vegetation in the UK and in
Switzerland using BDV RT-PCR
Prevalence rates will be determined if positive results are generated for BDV in ticks from cats &/or vegetation

Methods
Nucleic acid extracts are available from 71 ticks (Ixodes ricinus) collected from 39 cats from Northern Switzerland and from 541 ticks (I. ricinus, Ixodes hexagonus and Ixodes trianguliceps) collected from 541 cats from all over the UK. Extracts from 1,950 I. ricinus ticks (of which a random 1000 will be selected; all are in pools of 10) collected from vegetation in northern Switzerland are also available. Extracts will be subjected to BDV RT-PCR assays that target phosphoprotein p24and nucleoprotein p40, known to be sensitive and specific for BDV. 96-well plates and robots will be used to maximise efficiency. Appropriate positive and negative controls for PCR will be used throughout. A selection of positive results will be subjected to sequencing to confirm the presence of BDV. Pending the results of these PCRs, additional tick extracts are available from ticks collected from vegetation elsewhere in the world as well as from dogs and horses and could be tested if time and funds allow.

Anticipated outcomes
The presence of BDV in fed ticks collected from cats, and particularly in unfed ticks collected from vegetation, would support the role of ticks as vectors for BDV, highlighting the importance of tick control for prevention of infection.