What you need to know about Lyme disease
Lyme disease remains the most common vector-borne disease of both humans and dogs in the United States. Given the mildness of this past winter, there are concerns surrounding the anticipated increase in tick populations in areas considered to be endemic (e.g., New England and forested regions of the U.S.) but also for their potential migration to newer parts of the country never before seen. Recently, Lyme disease-carrying ticks were reported to have been newly discovered for the first time in beaches along Northern California.
The causative agent for Lyme disease is Borrelia burgdorferi sensu stricto (Bb), a spirochete which is transmitted via an infected bite from the Ixodes tick (deer tick); specifically, Ixodes scapularis among the Northeast, Mid-Atlantic, and Midwestern states, Ixodes pacificus among the Western coast, and Ixodes ricinusin Europe. A tick must attach for at least 36-48 hours before being able to transmit the disease to the host. The transmission into the host is facilitated by the spirochete’s expression of outer surface protein (osp) C.
Most seropositive dogs and cats are non-clinical, with cats thought to never truly develop detectable clinical signs related to Lyme disease. The manifestation of clinical illness in dogs generally presents in one of two, or combo of, forms:
· Lyme arthritis involves an acute onset of lameness or swelling associated with one or multiple joints. Systemic signs of lethargy and fever can also be seen. This presentation tends to be transient and self-resolving or demonstrates a rapid response to antimicrobial therapy, often within 1-2 days.
· Lyme nephritis is an immune driven protein losing nephropathy due to damage sustained by the glomerulus. Ideally all seropositive dogs should have urine screened for the presence of proteinuria. Currently, there is no established diagnostic criteria or validated medical management recommendations outside of the scope of a routine PLN workup and management of secondary complications. Immunosuppression is often utilized with these patients and mycophenolate serves as the first line immunosuppressive recommended.
From a diagnostic perspective, recommendations are for the use of serology testing such as commonly utilized in-house SNAP tests or quantitative antibody assays which are available for C6, OspA, OspC, and Osp F antibodies. Historically determining if a positive sample is due to vaccine induced antibody production versus an active natural infection has posed a challenge. Natural exposure is attributed for elevations seen in C6, VIsE, and OspF antibodies. The C6 quantitative assay elevation is not predictive of illness but has been shown to wane after treatment. Doxycycline is considered the first-choice antibiotic with a recommended treatment span of 4 weeks in patients displaying clinical signs. It should be noted that several other antibiotics have shown efficacy in treating Lyme disease and should be utilized as needed. No evidence has been demonstrated in cats and non-symptomatic seropositive dogs regarding whether antimicrobial therapy should be started. The current recommendation at the moment is to not start antimicrobials in those patient populations.
Vaccinations against Lyme disease have shown great efficacy in preventing seroconversion. By inducing anti-OspA antibodies that are ingested by the tick and attack any midgut spirochetes which stops transmission all together. Vaccine boosters are recommended every 6 months with qualitative antibody assays performed during annual wellness visit. Year-round tick preventative remains the most important aspect of management and prevention of not only Lyme disease, but other tick-borne diseases as well. Ideal preventatives are those that quickly kill or prevent feeding by the tick and are made available in topical and oral formulations.
For a more in-depth coverage of Lyme disease, the American College of Veterinary Internal Medicine (ACVIM)released a 2018 update to their 2006 consensus guidelines on the diagnosis, treatment, and prevention of Lyme borreliosis in dogs and cats.