How Lyme Disease (Borreliosis) Affects Dogs
Most dogs with Lyme disease never show signs of illness. When symptoms do occur, they usually involve limping and lameness, which are caused by pain around the dog’s joints. These signs may wax and wane, but they often come back and, if left untreated, progressively worsen with time.
Symptoms of Lyme Disease (Borreliosis)
Most owners never know that their dogs have been infected by Borrelia burgdorferi. In fact, only about 5% of infected dogs become noticeably ill. Dogs that do develop clinical Lyme disease usually show signs between 1 and 5 months after being bitten by an infected tick. Normally, symptoms show up in the spring, summer and fall, when the weather is warmer. The height of tick season in most parts of the United States is March through late September, tending to peak in July. However, deer ticks can survive and be active anywhere and any time that the temperature is above freezing.
Dogs with symptomatic Lyme disease may show one or more of the following symptoms:
- Acute onset of lameness (the most common and characteristic observable symptom; polyarthritis; usually lasts only a few days but frequently recurs; may come and go; may be persistent; can become chronic)
- Shifting leg lameness (limping changes from leg to leg)
- Swollen joints (especially the hocks of the hind legs and the “wrists” [carpi] of the front legs)
- Warmness around joints
- Painful joints (especially when palpated/moved or manipulated manually)
- Reluctance to rise
- Reluctance to walk
- Exercise intolerance
- Stiff, stilted gait
- Arched back (when standing or walking)
- Fever (variable; usually low-grade but can be elevated)
- Enlarged lymph nodes (lymphadenopathy)
- Lack of appetite (inappetence; anorexia)
- Weight loss
- Kidney disease. Severe renal disease has been widely reported in dogs with Lyme disease; when this unique form of kidney damage occurs, it usually presents with progressive vomiting, diarrhea, anorexia, weight loss, increased water intake (polydipsia), increased urine output (polyuria), swelling of the extremities (peripheral edema) and, unfortunately, death
- Cardiac (heart) abnormalities (uncommon; severe when present; usually sudden in onset; can be fatal)
- Neurological abnormalities (central nervous system consequences of Lyme disease are rare; seizures, facial paralysis and behavioral changes such as aggression have been attributed to Lyme disease in dogs)
Dogs at Increased
Puppies and young dogs are more susceptible to Lyme disease than older animals, although dogs of any age can be affected. Dogs that are allowed to roam freely and primarily live outside, as well as those that are routinely involved in outdoor activities like hunting, have a heightened risk of developing Lyme disease, simply because their chances of coming into contact with infected ticks are greater than those of other dogs. This is especially true if they live in or travel to endemic areas, which are the mid-Atlantic to northeastern coastal states, the upper Midwest and the coastal areas of the Pacific Northwest. Infection is even more likely if the dog moves through dense, undisturbed vegetation in those areas. The risk of infection is especially high when the nymph and adult ticks are actively seeking animal hosts to feed on, which is most common in the hot months of late spring, summer and early fall.
Certain breeds, including the Labrador Retriever, Golden Retriever, Shetland Sheepdog and Bernese Mountain Dog, develop a severe and frequently fatal form of Lyme disease that involves progressive damage to their kidneys. These breed associations suggest that there may be a genetic component to the cause of Lyme disease. However, the reason for these associations is unclear.