North Carolina may be a good distance from Connecticut, the birthplace of Lyme disease in the United States, but our state is still a hotbed for this tick-borne disease. As of April this year, 1 of every 43 dogs tested was positive for Lyme disease, which is a significant percentage compared with the western part of the country.
Which ticks transmit Lyme disease?
Of the 90 tick species in the United States, only one transmits Lyme disease. The black-legged tick is the sole carrier of Borrelia burgdorferi, the spirochete that causes the disease. On the eastern coast, we see Ixodes scapularis, the deer tick, while Ixodes pacificus plagues the Pacific Coast. The black-legged tick, which takes two years to complete its life cycle, is considered a three-host tick, where three of the four life stages feed on a different animal. Which stage causes you and your pet the most concern?
- Stage 1 — The egg stage usually lasts only from late spring to early summer. A well-fed female deposits her eggs on the ground, typically near where she left her last host.
- Stage 2 — Black-legged ticks hatch as six-legged larvae weeks after the eggs are laid in the spring. At this life stage, they feed on small mammals or birds during the summer and then drop off and winter on the ground. Larvae rarely carry tick-borne pathogens, but may pick up the Lyme spirochete during feeding and transmit it during the nymphal and adult stages.
- Stage 3 — Black-legged tick larvae that survive the winter molt into eight-legged nymphs in the spring. They emerge hungry and feed on a wide variety of mammals, including pets and people. Peak feeding season is usually May through July, but can vary according to weather patterns. Ticks in the nymphal stage are most likely to transmit pathogens, including Lyme disease. These “seed ticks” are about the size of a poppy seed and have a painless bite, making detection difficult and prolonging their opportunity to infect a host.
- Stage 4 — After a prosperous spring and summer feeding on smaller mammals, nymphs molt into adults during the fall. Adult black-legged ticks live up to their nickname, the deer tick, and seek large mammals like white-tailed deer for their final meal. A large mammalian host is crucial for an adult female tick to feed, mate, and lay her eggs, dying after completing this life cycle. If no large mammal is nearby, she will lie in wait throughout the winter, lingering until temperatures rise above freezing before resuming her search.
Adult ticks are less likely to transmit Lyme disease than nymphs, since transmission of the Lyme spirochete requires at least 24 to 48 hours. Nymphs are smaller than adult ticks, allowing them to evade detection and remain attached to the host longer.
What are the signs of Lyme disease in dogs?
If your dog has been bitten by a black-legged tick, signs rarely appear immediately. Distinguishing between tick-borne diseases is challenging, since most show similar signs, such as:
- Lameness that shifts from leg to leg
- Painful, swollen joints
- Decreased appetite
- Swollen lymph nodes
Pets infected with the Lyme spirochete don’t display the stereotypical bulls-eye rash seen in people. However, they may have a local reaction, indicated by swelling and scabbing.
How is Lyme disease diagnosed and treated?
Lyme disease is challenging to diagnose, since infected pets may show no signs of illness. We diagnose Lyme disease based on factors, such as:
- Clinical signs
- Tick exposure
- Positive antibody test
- Protein level in the urine
- Blood work
A dog bitten by an infected tick will not develop antibodies to the Lyme spirochete for at least two to five months, so an early test may show a false-negative result. In addition, Lyme disease antibodies can linger in the body, even after antibiotic therapy, so determining new exposure can be difficult.
If your pet is showing signs of illness and we diagnose Lyme disease, we will prescribe a lengthy course of antibiotics to clear the bacteria. Your pet may also require pain medication if she has lameness that is causing discomfort.
Lyme disease is a serious threat to both people and pets. To prevent infection, we recommend using quality tick prevention and vaccinating your dog for Lyme disease. Stop by our hospital for help in choosing the appropriate tick preventive to ensure this debilitating disease does not harm your furry friend.