Ehrlichiosis in dogs | Is Ehrlichia in dogs fatal?

Ehrlichiosis is a tick-born disease of dogs that is caused by a rickettsial agent, Ehrlichia canis. This E.canis is actually a pathogen of dogs and is only spread by the bite of an infected tick. Humans can also be susceptible to ehrlichiosis if get exposed to a tick bite.

Here one thing should be kept in mind: Ehrlichia canis only make dogs sick while other Ehrlichia species, like Ehrlichia chaffeensis, E. ewingii, and E. Muris eauclairensis, make people and dogs sick. This disease is not zoonotic and not contagious so it doesn’t spread from dogs to humans or from one infected dog to a healthy dog. If we talk about dogs then the German shepherd breed, Doberman pinscher, and Siberian Huskies are more prone to ehrlichiosis as compared to other breeds of dogs.

If this disease is left untreated then it can be fatal. So this article is going to cover in detail Ehrlichiosis in dogs, its cause, symptoms, what to do if your dog is positive for ehrlichiosis, treatment, and many more. So stay in touch with us.

Other Names: canine rickettsiosis, canine hemorrhagic fever, canine typhus, tracker dog disease(because of the death of a large number of dogs in the Vietnam War), tropical canine pancytopenia, canine granulocytic ehrlichiosis, canine monocytic ehrlichiosis.

If the causative agent is E.canis that is more pathogenic as compared to other Ehrlichia sp, then this E.canis lives in the monocytes (agranulocytes WBCs). So the disease will be called as Canine monocytic ehrlichiosis while if the causative agent is E.ewingii that lives in granulocytic WBCs then disease will be called as Canine granulocytic ehrlichiosis.

Cause of Ehrlichiosis in Dogs

The cause of ehrlichiosis in dogs is a rickettsial bacteria that belong to the genus Ehrlichia in the family Ehrlichiaceae. There are various species of the genus Ehrlichia but E.canis is the most pathogenic and is responsible for causing acute ehrlichiosis in dogs. Out of other species, E.ewingii was also reported in causing canine ehrlichiosis.

This disease spreads because of the bite of a brown dog tick (Rhipicephalus sanguineous) containing the Ehrlichia canis or ewingii.

Note: The brown dog tick is the main carrier of the Ehrlichia organism in nature. Other tick species have also been reported to transmit the disease in dogs and may carry other subspecies of Ehrlichia. Some other tick species responsible for causing canine ehrlichiosis are the lone star tick, the American dog tick, and the black-legged tick.

Transmission & Pathogenesis of Ehrlichiosis in Dogs

When a tick infected with Ehrlichia sp. bites a dog and remains attached for several hours, the bacteria enters the bloodstream of the dog and infection occurs. Dogs also contract the disease by receiving blood transfusions from affected animals.

When Ehrlichia enters a dog’s body, it invades the monocytes and, in rare cases, the platelets, which results in thrombocytopenia and other bleeding issues.

Signs & Symptoms of Ehrlichiosis in Dogs

In dogs, ehrlichiosis has three stages. Stages include acute, subclinical, and chronic. The disease’s acute stage, which most frequently manifests in the spring and summer, starts one to three weeks after infection and lasts for two to four weeks.

The subclinical phase, which might span the rest of the dog’s life and has no visible symptoms, is when the dog is still infected with the organism. During this time, the disease can be completely eradicated in some dogs. The most dangerous stage of infection is the chronic phase. The signs and symptoms of ehrlichiosis in dogs are:

Acute stage of Ehrlichiosis in Dogs

• Fever
• Petechiae
• Bleeding disorders
• Vasculitis
• Lymphadenopathy
• Discharge from the nose and eyes
• Edema of the legs and scrotum

Note: Because there are no clinical indications during the sub-clinical phase, the disease cannot be recognized, and this is why it is sometimes seen as the worst stage.

Chronic stage of Ehrlichiosis in Dogs

• Weight loss
• Pale gums due to anemia
• Bleeding due to thrombocytopenia
• Vasculitis
• Lymphadenopathy
• Dyspnea
• Coughing
• Polyuria
• Polydipsia
• Lameness
• Ophthalmic diseases such as retinal hemorrhage and anterior uveitis
• Neurological disease

Note: Clinical signs of ehrlichiosis in humans are: Fever, headache, eye pain, and gastrointestinal distress. Although it is relatively similar to Rocky Mountain spotted fever, patients do not have a rash. Get more information on Human Ehrlichiosis here.

How to Diagnose Ehrlichiosis in Dogs?

Every disease diagnosis should follow three protocols, according to the established norm.

1- History

2- Clinical signs

3- Laboratory tests

History

To diagnose ehrlichiosis in dogs, history can be a helpful tool. If a dog has been in a tick-infested area or has lived in a kennel or boarding facility, then a veterinarian should test for ehrlichiosis.

Clinical signs

A predictive diagnosis of ehrlichiosis can be made by performing a physical examination to check for fever, joint pain or swelling, enlarged lymph nodes, bleeding, and other clinical signs in the dog.

Laboratory tests

Serologic testing of the blood for antibodies is the most common method for diagnosis, however, during the acute stage of illness, the test may result in a false negative since the body won’t have had time to produce antibodies against Ehrlichia.

In the acute stage, the genetic makeup of the bacteria can be found using a PCR (polymerase chain reaction) test. During the subclinical and chronic illness phases, the PCR test is more likely to produce a negative result.

Another way to diagnose ehrlichiosis in dogs is to make a blood smear for the presence of Ehrlichia morulae, which sometimes can be seen as intracytoplasmic inclusion bodies within a white blood cell.

Besides these tests, a complete blood count may be useful in diagnosing canine ehrlichiosis. Low hemoglobin levels (anemia), and low platelet counts are the typical findings.

Note: The gold standard in diagnostic testing is blood culture. A certain diagnosis can be made by growing the germs in a lab. Receiving results can take up to 8 weeks.

Treatment of Ehrlichiosis in Dogs

Treatment for ehrlichiosis in dogs involves the use of antibiotics such as tetracycline or doxycycline for a period of at least six to eight weeks; it could take a month for the medication to take effect.

Animals with clinical symptoms require supportive care. Animals who are dehydrated are given subcutaneous or intravenous fluids, and extremely anemic dogs may need a blood transfusion.

Recommended drug dosages for the treatment of ehrlichiosis are:

• Doxycycline: 5–10 mg/kg/day, PO or IV, for 10–21 days (drug of choice)
• Tetracycline: 22 mg/kg, PO, three times a day (≥2 weeks, acute cases, 1–2 months, chronic cases)
• Imidocarb diproprionate: 2 doses, 5–7 mg/kg, IM, 2 weeks apart

How to Prevent Ehrlichiosis in Dogs?

The best way to prevent ehrlichiosis in dogs is tick control. Now to control ticks, various strategies can be adopted like

Avoid taking your dog to a tick-infested area

Use some ticks repellents

Keep looking at your dog for ticks’ presence and remove them if ticks are present. Now where ticks are normally present in a dog? The answer is, in dogs, the ticks are mostly present around the eyes, in and around ears, between the hind legs, under the collars, between the toes, and around the tail. Some studies reported that in areas where the tick population is greater, tetracycline could be administered daily for 200 days at a lower dose.

Conclusion

Ehrlichiosis in dogs is a tick-born bacterial disease caused by Ehrlichia Canis. Ticks are the mechanical vectors in the spread of rickettsial pathogens. Dog-to-dog or dog-to-human transmission is rare. Clinical findings are related to pancytopenia and bleeding issues. Diagnosis can be made on the basis of history, clinical findings, and bacterial culture. Doxycycline is the drug of choice for canine ehrlichiosis. The disease can be prevented by controlling the tick population.

References

Wikipedia. “Canine Ehrlichiosis”

Centers for Disease Control and Prevention. “Ehrlichiosis in Dogs” 

McQuiston, J. Merck Veterinary Manual, “Ehrlichiosis and Related Infections in Dogs” Merck & Co., 2020. 

PetMD. “Ehrlichiolosus in Dogs“

VCA Animal Hospitals. “Ehrlichiosis in Dogs”

(2011). Viral, Rickettsial, and Protozoal Skin Diseases. Small Animal Dermatology (Third Edition), 159-174. https://doi.org/10.1016/B978-1-4160-5663-8.00006-9