Tick-Borne Diseases
Well, since we looked at our ticks in my last blog, we will talk about tick-borne diseases this week. So, we will talk briefly about ehrlichiosis, Rocky Mountain spotted fever, Lyme, anaplasmosis, and babesiosis. I am going to do this blog a little differently, and I will put this information in an outline form. Otherwise, I think I may bore you to tears with the details. This way you can get “Just the facts, ma’am.”
Ehrlichiosis
A. Causative organisms
1. Ehrlichia canis
2. Ehrlichia ewingii (Fun fact: this is named for
Dr. Sidney Ewing from Oklahoma State
University)
B. Tick vector
1. E. canis is carried by the brown dog tick.
2. E. ewingii is carried by the Lone Star tick.
C. Clinical Signs
1. E. canis has 3 disease stages. In the acute stage,
dogs can have inappetence, weight loss, lethargy,
bleeding abnormalities (bruises on the body,
nosebleeds, or bleeding in the eyes), ocular
abnormalities (retinal hemorrhages/detachments,
blindness), or neurological abnormalities (seizures,
ataxia/incoordination, vestibular signs, unequally
sized pupils). They may have enlarged lymph
nodes or an enlarged spleen or liver. In
the subclinical stage, dogs don’t exhibit clinical
signs, but they can have a decreased platelet
count. In the chronic stage, dogs can exhibit all of the
signs seen in the acute stage, and they can also have bone marrow suppression,
which will cause all of the cell lines on a CBC to be low.
2. E. ewingii causes fever, stiff gait/lameness, and lethargy most commonly, but it can
also cause vomiting, diarrhea, and neurological signs. Bleeding is uncommon.
D. Treatment
Doxycycline is the antibiotic of choice, and generally, a 28-day course is recommended.
Some dogs with E. canis will need imidocarb diproprionate, which is a drug used to treat
protozoal diseases (we will talk more about this later), or prednisone if their platelet counts
are low. Dogs with E. ewingii may need analgesics to control their joint pain.
E. Human Disease
At least 3 different Ehrlichia spp. organisms affect humans. The most common clinical
symptoms include fever, headache, fatigue, and muscle aches. These signs usually develop
within 1-2 weeks of a tick bite. The first choice drug for treatment is doxycycline.
Rocky Mountain spotted fever
A. Causative organism
1. Rickettsia ricketsii
B. Tick Vector
1. The American dog tick and the brown dog tick can carry this organism.
C. Clinical Signs
Clinical signs show up in 2-14 days. The common signs include fever, lethargy, inppetence,
pain, nosebleeds, cough, enlarged lymph nodes, lameness, skin sloughing, peripheral
edema/swelling, and hemorrhage/bruising. Clinical signs can be mild, or they can be severe
enough to result in death.
D. Treatment
Doxycycline is the first choice antibiotic, and quinolone antibiotics can be used as well.
Some dogs will require blood transfusions or other supportive therapies.
E. Human Disease
This is a potentially fatal disease in people, too. Typical clinical signs include fever,
headache, abdominal pain, vomiting, and muscle pain. People can develop a rash.
Doxycycline is the first choice drug, and it is most effective if started before the fifth day of
symptoms.
Lyme Disease
A. Causative Organism
1. Borrelia burgdorferi
B. Tick Vector
1. The deer tick.
C. Clinical Signs
Clinical signs in dogs often don’t show up for weeks to
months after infection. Some dogs will run a fever, and
rarely, heart disease and neurological disease can
develop. Lyme can be associated with chronic joint
disease, and the most serious problem in the dog
associated with Lyme is a form of kidney disease
(glomerulonephritis) where the dog loses protein
through the kidneys.
D. Treatment
Lyme disease can be treated with a 2-4 week course of
doxycycline or amoxicillin.
E. Human Disease
After being bitten by an infected tick, 80% of people will
develop a rash and/or flu-like symptoms. Next, they can develop joint pain, and
approximately 15% will develop neurological disease. Another 5% will develop a heart
arrhythmia known as A-V block. Weeks to months after infection, approximately 60% of
people will experience intermittent arthritis, and 5% will develop chronic neurological
problems. So, people have the potential for serious long-term illness from Lyme disease.
Most cases can be effectively treated with antibiotics.
Anaplasmosis
A. Causative Organism
1. Anaplasma phagocytophilum (granulocytic anaplasmosis)
2. Anaplasma platys (infectious cyclic thrombocytopenia)
B. Tick Vector
1. The deer tick transmits A. phagocyophilum.
2. The brown dog tick and the American dog tick are believed to transmit A. platys, but
the transmission of this organism is not fully known.
C. Clinical Signs
1. Granulocytic anaplasmosis causes an infection of white blood cells. Most dogs will
show signs within 1-2 weeks, and they can exhibit lethargy, inappetence, fever, and
joint pain. Less common signs include vomiting, diarrhea, coughing, and difficulty
breathing.
2. Infectious cyclic thrombocytopenia causes infection of platelets. Clinical signs
include lethargy, inappetence, fever, bruising, nosebleeds, and weight loss.
D. Treatment
Doxycycline is the first choice antibiotic, and some dogs will require analgesics and anti-
inflammatory drugs to control their pain.
E. Human Disease
Human granulocytic anaplasmosis (HGA) is causes by A. phagocytophilum. Typically clinical
signs of fever, headache, chills, and muscle aches develop within 1-2 weeks of tick bite.
Doxycycline is the first line treatment.
Babesiosis
A. Causative Organism – this is a protozoal disease of red blood cells
1. Babesia canis
2. Babesia gisoni (the most common of clinical disease in the USA)
B. Tick Vector
1. The brown dog tick is the primary vector for B. canis.
2. Dog-to-dog transmission (bite wounds) rather than tick transmission is believed to be
the primary route of transmission for B. gibsoni. American pit bull terriers can be at
increased risk because of fighting, but this breed, along with greyhounds, can spread
this organism through the placenta.
C. Clinical Signs
Clinical signs include lethargy, anorexia, fever, pale mucous membranes, jaundice, dark urine, enlarged spleen, and enlarged liver.
D. Treatment
Imidocarb dipropionate is used to treat B. canis. This medication is given as an
intramuscular injection, and a second injection must be given 2 weeks later. This drug will
not likely cure the disease, however. Atovaquone, another anti-protozoal drug, can be
combined with azithromycin, an antibiotic, to treat B. gibsoni, and this combination is 54-83%
effective. Some dogs will need blood transfusions or fluids as supportive therapy.
E. Human Disease
Babesia microti is the organism responsible for disease in people, and the primary tick
vector is the deer tick. Babesiosis can cause anemia, jaundice, and dark urine in people,
and the populations at greatest risk are the immunocompromised, the elderly, and people
without a spleen. People are treated with either atovaquone and azithromycin or clindamycin
and quinine. Blood transfusions and dialysis may be required during therapy.
As we wrap up tick-borne diseases, I hope you have a better understanding of the impact that these nasty little creatures can have on our pets’ health as well as our own health. Please talk to your veterinarian about an effective tick prevention program, and don’t forget to check yourself for ticks, too. Stay safe this summer!
Resource:
