The Future of Vector-Borne Disease Testing
Vector-borne diseases - those spread by fleas, ticks, flies, etc – are important in veterinary and human medicine. Infections like Lyme disease (caused by Borrelia burgdorferi bacteria spread by ticks) and Bartonellosis (caused by Bartonella bacteria spread by fleas and ticks) can cause fever, painful joints, kidney disease, heart disease, and more in dogs, and may even be associated with cancer. Plus, new infectious organisms are being discovered to add to the list of vector-borne diseases in dogs and people. Diagnosing these infections can be frustrating due to limitations of current testing methods. However, with funding from the AKC Canine Health Foundation (CHF), investigators at Western University of Health Sciences are studying new technologies which may greatly improve our ability to diagnose known and unknown vector-borne infections.
Current testing methods –
PCR (polymerase chain reaction) is the current gold standard test for vector-borne infections. This technique tests for specific pieces of DNA from the invading organism. A positive PCR test result indicates that the infectious organism is definitely present. This test is good for diagnosing acute infections, before the body has had time to make antibodies. However, one pitfall of this test is that the exact tissue or fluid where the organism resides must be tested. So for example, it may not detect Bartonella bacteria that are no longer circulating in the bloodstream, but hiding within organ tissues.
Serology is a relatively easy and inexpensive method that measures antibodies against various infectious organisms. This test is good for detecting organisms that like to hide because even though the organism itself is hiding, the antibodies produced to fight it are circulating throughout the bloodstream for easy collection and measurement. Measuring how antibody levels change over time (for example in blood samples collected two weeks apart) is an effective way to determine if the infection is active and monitor response to treatment. Because it takes several days for the body to make antibodies against a vector-borne pathogen, serology will not be positive immediately after infection. Serology results may also be affected by cross-reactivity, so false positives are possible.
Exploring new technologies –
CHF-funded investigators are exploring the use of next generation sequencing (NGS) to improve the accuracy and ease of diagnosing vector-borne infections in dogs. NGS detects small pieces of the genetic sequence of an organism, and it processes many sequences at the same time. While the genetic sequencing is relatively fast and inexpensive to complete, analyzing the large amount of data generated requires time and expertise in bioinformatics.
Investigators have confirmed that NGS can detect one or more infectious organisms in dog blood, including unknown organisms. It can also determine the relative amounts of infectious DNA present in a sample – which may be helpful to pinpoint the most active or important infectious organism in a dog infected by multiple organisms (a condition known as co-infection). A step-by-step bioinformatics tutorial for performing microbiome assays and analysis on vector-borne infections in veterinary medicine was recently published.1
Next generation sequencing (NGS) may revolutionize vector-borne disease testing in veterinary medicine since it can rapidly detect the relative amounts of infectious organism DNA in dog blood samples.
While NGS for vector-borne infections continues to be refined, veterinarians and dog owners must remember the strengths and weaknesses of PCR, serology, and other diagnostic testing methods to accurately assess their patients. PCR is good for diagnosing acute infections since it measures DNA of the infectious organism. Serology is beneficial as long as sufficient time has passed for the body to make antibodies. Measuring how antibody levels change over time can also be a powerful tool to understand the infection timeline. Interpreting results from PCR and serology combined provides the most accurate diagnosis in a dog with suspected vector-borne disease. The addition of NGS to the clinical setting in the near future will improve the accuracy of vector-borne disease testing in dogs and people. A more accurate diagnosis leads to more effective treatment – helping dogs live longer, healthier lives.
Learn more and support CHF-funded vector-borne disease research at www.akcchf.org/ticks.
- Vasconcelos, E. J. R., Roy, C., Geiger, J. A., Oney, K. M., Koo, M., Ren, S., Oakley, B. B., & Diniz, P. P. V. P. (2021). Data analysis workflow for the detection of canine vector-borne pathogens using 16 S rRNA Next-Generation Sequencing. BMC Veterinary Research, 17(1), 262. https://doi.org/10.1186/s12917-021-02969-9
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