Tick-Borne Diseases in Dogs: Symptoms, Testing, Treatment, and Prevention

A tick is a small problem right up until it isn't. Morris Animal Foundation's white paper on tick-borne diseases, written with active outdoor dogs in mind, opens with a point worth sitting with: the geography of these illnesses is shifting. The paper attributes that shift to a changing climate, altered wildlife migration patterns and deforestation, all of which are pushing tick species into parts of the country where they were not previously much of a concern. The practical upshot is that advice which was correct for your region ten years ago may not be correct now.

Before the scary-sounding names start, here is the reassuring structural fact. Tick-borne diseases are a subset of vector-borne diseases, and a vector is simply an intermediate carrier, usually a bug, that ferries an organism from one host to another. For most of these illnesses the tick is not optional. No bite, no transmission. As the paper puts it, many vector-borne diseases cannot pass from dog to dog, or dog to human, or the other way around. Your dog is not a Lyme disease hazard to your family. The tick in your hedgerow is.

Roughly 850 tick species, and only a handful matter

The white paper counts nearly 850 tick species worldwide and around 90 in the United States, of which only a few are associated with disease. Different species also carry different pathogens, which is why the useful question is not "are there ticks here?" but "which ticks live where I walk, and where I'm travelling to?" For scale, the paper notes that owners spent about $1.3 billion on tick, flea and heartworm control in 2018. This is not a fringe worry. It is also not a mysterious one.

The seven that matter most in the US

Morris Animal Foundation groups the important canine tick-borne diseases into seven. You do not need to memorise them, but recognising the names when your vet says one out loud is genuinely helpful.

• Lyme disease. Caused by the bacterium Borrelia burgdorferi and spread by blacklegged ticks, better known as deer ticks. Once largely a Northeast problem, it has since been reported in the mid-Atlantic, Midwest, Great Lakes states, southern Appalachia, the West Coast and southern Canada.
• Anaplasmosis. A bacterial infection with a wide distribution across the continental US. Blacklegged ticks carry it in the Northeast and Midwest; the brown dog tick is the main carrier in the south-central states.
• Ehrlichiosis. Also bacterial, also widely distributed. Several Ehrlichia species can cause it and several tick species can spread it, but the paper notes they all produce similar signs and are treated with the same medications.
• Rocky Mountain spotted fever. The paper singles this one out as among the most serious, because of its rapid onset and high fatality rate. The name is a misnomer; cases occur widely across the country.
• Babesiosis. Caused by one of two protozoal species. One is tick-spread and most common in the southern US; the other spreads mainly through blood contamination when dogs fight, which is an unusual route for a "tick" disease.
• Hepatozoonosis. Another protozoal disease, and another the paper describes as often fatal despite treatment. Its transmission route is the odd one: a dog is infected by eating an infected tick while grooming, or by eating game that has swallowed infected ticks.
• Bartonellosis. Better known in people as cat scratch disease. Whether ticks can transmit it to dogs remains, in the paper's own framing, controversial and actively under study.

Why these infections are so slippery to diagnose

If your vet seems cautious about giving you a firm answer quickly, this is why. The white paper lists three reasons these diseases resist tidy diagnosis: the organisms hide inside a dog's own cells, which makes them invisible to both the immune system and to many diagnostic tests; the symptoms overlap heavily with other illnesses; and signs may not appear until months after the bite that caused them. That last one is the reason your vet may ask about a camping trip you had almost forgotten.

The signs common to nearly all of these infections are, frustratingly, also the signs of nearly everything else: fever, lethargy, poor appetite, and lameness that can shift from one limb to another. That shifting lameness is the one owners tend to notice and dismiss. A dog limping on a front leg on Tuesday and a back leg on Thursday is worth mentioning.

Blood tests remain the backbone of diagnosis, the paper says, combining a routine blood panel with more specific tests. Treatment generally means antibiotics, sometimes for many months and in some cases for life, alongside supportive care and anti-inflammatory medication to manage the symptoms. Your veterinarian will choose the specific drug and the length of the course; that is not a decision to make from a website.

Prevention is where you actually have leverage

This is the genuinely good news, and the paper leans on it hard. For most of these diseases a tick has to stay attached for around 24 hours before it can pass anything on, which means a daily habit does most of the work.

• Check your dog every day, and especially after hunting, hiking or camping. Ticks can be very small, so run a fine-toothed comb through the coat rather than relying on eyes and fingertips alone.
• If you find one, remove it carefully and drop it into rubbing alcohol for disposal.
• Talk to your vet about preventive products. A range of medications exists, and vaccination is available for some diseases. The right combination depends on where you live, where you travel, and whether your dog hunts, hikes or swims.
• Check regional risk before you travel. The US Centers for Disease Control and Prevention publishes detailed maps showing which diseases are prevalent where, which the white paper recommends as a starting point.

What research is still chasing

Morris Animal Foundation has funded tick-borne disease research since 1963, and reports investing more than $400,000 across 22 studies, with a focus on improved diagnostics for hepatozoonosis, babesiosis and ehrlichiosis. Its Golden Retriever Lifetime Study, which follows a cohort of 3,044 dogs, offers an unusual real-world window: as of June 2021, 178 of those dogs had at least one tick-borne condition noted by their own vet. The paper is careful to say that some of those are positive screening tests rather than confirmed illness, which is a useful reminder that a positive result and a sick dog are not the same thing.

None of this needs to end your walks in long grass. It means a comb, a habit, and a conversation with your vet about what actually lives in your postcode. This article is general information and does not replace diagnosis or treatment advice from a licensed veterinarian.