By Jason Johnson, DVM, MS, DACT

Ticks can spread a variety of diseases. As their range expands throughout the country, it becomes more difficult to avoid encountering these adaptable parasites. With forecast maps from the Companion Animal Parasite Council (CAPC) showing alarming changes in the regional distribution of vector-borne disease (VBD), the increased risk also poses new challenges for
veterinary professionals.¹

While a single tick can transmit several infectious agents that can cause serious illnesses, pet owners often need help seeing the value of VBD screening and deciding to have annual testing for their pets.² Not only are these diseases notoriously silent and difficult to diagnose in the early stages based on signs alone, leaving them undiagnosed can also lead to serious harm.³

Prevention and early detection are both vital to protecting pets against VBD. To help veterinarians stay ahead of the curve and provide the best care to their patients, the following explores why comprehensive screening is critical to pet health with key insights into a lesser-known tick-borne disease that has become more frequently detected than Lyme.

Advances in testing put Anaplasma on the radar

With the ability to screen for tick-transmitted pathogens in a single blood sample, comprehensive VBD testing helps track the spread and development of the most common pathogens.³ For example, while most canine anaplasmosis cases previously went undetected, advances in screening resulted in the ability to track the recent increase in positive rates in 2022. Detected rates of anaplasmosis have more than doubled in 2022 alone, rising from 2.54 percent in January to 5.36 percent in October.⁴

Canine granulocytic anaplasmosis is caused by the bacterium Anaplasma phagocytophilum, which is transmitted by the black-legged tick or deer tick, the same tick that transmits Lyme disease.

Despite being linked to the same tick, Lyme positivity rates have decreased over the last several years. This is likely due to more effective products in the isoxazoline class that kills ticks before they can transmit the disease.⁵

While Anaplasma can be transmitted before the tick is killed, Lyme takes longer—often 48 to 72 hours—enabling most tick products to kill the parasite before Lyme disease transmission.6 This likely contributes to more positive Anaplasma cases among pets nationally.

"What I have been hearing from practitioners is Anaplasma is becoming the most common vector-borne infection they're seeing dogs are exposed to," said Adam Birkenheuer, DVM, PhD, DACVIM, assistant professor of small animal internal medicine at North Carolina State University, College of Veterinary Medicine, an internationally recognized expert on vector-borne infections of dogs and cats. "Having a keen awareness if it's there, understanding it can cause disease, and understanding it is something that should be screened for becomes important," Dr. Birkenheuer adds.

Preventives are not guaranteed

Given an infection's harmful impact on a pet's health can sometimes be challenging to confirm, particularly in those not exhibiting visible symptoms, protection begins with regularly screening pets to identify their potential exposure.

Unfortunately, prescribing preventives alone is not always sufficient in guarding against VBD. While parasite preventives can effectively minimize vector-borne disease transmission, lapses in dosing, intentionally or inadvertently, could cause gaps in protection.

For example, in the United States, the number of active patients receiving flea and tick, or heartworm preventive products is only 28.5 percent and 27.1 percent, respectively.⁷ While these products require 12 doses to be protected annually, the average patient falls short with clients giving an estimated six doses for flea and tick, and eight doses for heartworm.⁷ Also, unlike Lyme disease, there are no vaccines available for Anaplasma.

To help combat this uncertainty, CAPC guidelines recommend annual comprehensive screening for pathogens transmitted by ticks.⁸ Veterinary professionals may find incorporating this yearly testing cycle adds value to their practice, including determining if new infections are threatening the pets in a community, assessing a pet's risk of having more than one infection, and providing crucial metrics to understand how prevention protocols are working.^8,9

Veterinarians have the opportunity to remind pet owners as parasites become more active and the risk for VBD increases, the most robust defense for their pet's longevity is a combination of preventive care and routine screening.

Understanding the potential risk to humans

Dogs often function as sentinels for the presence of tick-borne disease in a community. Although those who spend more time outdoors are at higher risk of contracting VBD, no pet is completely safe. Since many of these diseases are transmissible to humans, it is important to understand the risks in your community to best protect your patients and their families.

Due to the fact Lyme disease and anaplasmosis are caused by organisms that also infect people, canine VBD screening can empower veterinary professionals and clients with data to inform their understanding of the risk these diseases pose to humans.

In addition to helping us protect the health of pets and their owners, comprehensive VBD screening can be a valuable tool for monitoring what is happening in our communities and with each other. We must stay alert to these risks to protect pets and people, and the best way to do so is by using the most accurate testing available for VBD screening. Look for options that offer clinical support to help you make fast and effective clinical decisions and determine the most appropriate next steps for the pets in your care.

Jason Johnson, DVM, MS, DACT, is vice president and global chief medical officer at IDEXX with more than 19 years of experience within the veterinary industry. Dr. Johnson was the co-founder/vice president and dean of LMU-College of Veterinary Medicine and founder of the Center for Animal and Human Health in Appalachia. Johnson has conducted international veterinary work across seven countries and believes it is both a privilege and a responsibility to elevate animal health around the globe.

References

1. Parasite prevalence maps: Lyme disease [dog]. Companion Animal Parasite Council. Accessed January 4, 2023. https://capcvet.org/maps/#/2022/all-year/lyme-disease/dog/united-states
2. Lashnits E. Vector-borne disease testing and effective client communication. Vetiverse. Published August 5, 2021. Accessed January 4, 2023. https://www.thevetiverse.com/en/latest/vector-borne-disease-testing-and-effective-clien
3. The Value of Vector-borne Disease Screening. IDEXX; 2022. Accessed January 4, 2023. https://www.idexx.com/media/filer_public/fc/eb/fcebb3ef-c5e8-4fd4-b68d-2ecafb7a0296/4dx-plus-clinical-reference-guide.pdf
4. Parasite prevalence maps: Anaplasmosis [dog]. Companion Animal Parasite Council. Accessed January 18, 2023. https://capcvet.org/maps/#/2022/all-year/anaplasmosis/dog/united-states
5. Baker CF, McCall JW, McCall SD, et al. Ability of an oral formulation of afoxolaner to protect dogs from Borrelia burgdorferi infection transmitted by wild Ixodes scapularis ticks. Comp Immunol Microbiol Infect Dis. 2016;49:65–69. doi:10.1016/j.cimid.2016.09.004. https://pubmed.ncbi.nlm.nih.gov/27865266/
6. des Vignes F, Piesman J, Heffernan R, Schulze TL, Stafford KC 3rd, Fish D. Effect of tick removal on transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by Ixodes scapularis nymphs. J Infect Dis. 2001;183(5):773–778. doi:10.1086/318818. https://academic.oup.com/jid/article/183/5/773/892071
7. IDEXX Practice Intelligence data. Sample of approximately 7,000 practices representing six different practice information management systems, weighted to represent the country based on practice size and region. Data on file at IDEXX Laboratories, Inc. Westbrook, Maine USA.
8. General guidelines for dogs and cats: parasite testing and protection guided by veterinarians. Companion Animal Parasite Council. Updated September 16, 2022. Accessed January 4, 2023. https://capcvet.org/guidelines/general-guidelines/
9. Regions where ticks live [maps]. Centers for Disease Control and Prevention. Reviewed December 5, 2022. Accessed January 4, 2023. https://www.cdc.gov/ticks/geographic_distribution.html