Leishmaniasis in Dogs
Leishmaniasis, a medical condition caused by the protozoan parasite Leishmania, manifests in two forms in dogs: cutaneous (skin) reaction and visceral (abdominal organ) reaction, commonly referred to as black fever, the most severe form of leishmaniasis.
The infection occurs when sandflies transmit the flagellated parasites into the host’s skin. The time from infection to symptoms typically ranges from one month to several years. In dogs, the parasite spreads throughout the body, affecting most organs. Renal (kidney) failure is the leading cause of death, with almost all infected dogs developing visceral or systemic disease. Skin involvement occurs in up to 90 percent of cases. Leishmaniasis does not show age, gender, or breed preferences, but males are more likely to experience a visceral reaction.
The disease affects various organ systems, including the skin, kidneys, spleen, liver, eyes, and joints. Dogs commonly experience skin lesions, hair loss, and a tendency to hemorrhage.
In the United States, infected dogs often contract Leishmania in other countries, particularly in the Mediterranean basin, Portugal, and Spain. Sporadic cases have been reported in Switzerland, northern France, the Netherlands, and endemic areas in South and Central America, as well as southern Mexico. Additionally, endemic cases have been identified in Oklahoma and Ohio among dog populations.
It’s crucial to recognize that leishmaniasis is a zoonotic infection, meaning the organisms present in the lesions can be transmitted to human.
Symptoms
Leishmaniasis in dogs presents in two distinct types: visceral and cutaneous, each affecting different areas of the dog’s body.
Visceral — impacts organs within the abdominal cavity
- Severe weight loss
- Loss of appetite (anorexia)
- Diarrhea
- Tarry feces (less common)
- Vomiting
- Nosebleeds
- Exercise intolerance
Cutaneous — affects the skin
- Hyperkeratosis — the most prominent feature, characterized by excessive epidermal scaling with thickening, depigmentation (loss of skin color), and chapping of the muzzle and footpads
- Alopecia — a dry, brittle hair coat with symmetrical hair loss
- Nodules typically form on the skin’s surface
- Intradermal nodules and ulcers may be observed
- Abnormally long or brittle nails may be present in some cases
Additional signs and symptoms associated with leishmaniasis include:
- Lymphadenopathy — lymph node disease with skin lesions present in 90 percent of cases
- Emaciation
- Signs of renal failure — including excessive urination, excessive thirst, and possible vomiting
- Neuralgia — a painful disorder of the nerves
- Joint pain
- Muscle inflammation
- Osteolytic lesions — characterized by a “punched-out” area with severe bone loss
- Inflammation of bone coverings, though rare
- Fever with an enlarged spleen (seen in approximately one-third of patients)
Causes
The primary method of contracting the infection is by traveling to endemic regions, typically in the Mediterranean, where dogs can be exposed to sandflies, known hosts of Leishmania. Additionally, receiving a transfusion from another infected animal can also result in leishmaniasis.
Diagnosis
Your veterinarian will conduct a comprehensive physical examination of your dog, considering the history of symptoms and any potential incidents that may have contributed to the condition. A thorough blood profile, including a chemical blood profile, complete blood count, and urinalysis, will be performed. The veterinarian will search for indications of diseases such as lupus, cancer, and distemper, among other potential causes of the symptoms. Tissue samples from the skin, spleen, bone marrow, or lymph nodes will be obtained for laboratory culturing, along with fluid aspirates. Given the presence of lesions on the skin’s surface, a skin biopsy will also be necessary.
Dogs with leishmaniasis typically exhibit elevated levels of protein and gammaglobulin, as well as increased liver enzyme activity. Nonetheless, the veterinarian will need to rule out tick fever as a potential cause of the symptoms and may conduct specific tests for lupus to either confirm or exclude it as a contributing factor.
Treatment
Unless your dog is severely ill, outpatient treatment will be provided. In cases where the dog is emaciated and suffering from chronic infection, euthanasia may need to be considered due to the poor prognosis. For dogs not severely infected, the veterinarian will prescribe a high-quality protein diet, especially designed for renal insufficiency if necessary.
As this is a zoonotic infection, the organisms present in the lesions can be transmitted to humans. Complete elimination of these organisms is unlikely, and relapse requiring treatment is probable. Medications are available to help alleviate symptoms and address the disease. Your veterinarian will guide you on the most appropriate course of action.
Recovery and Management
Your veterinarian will monitor your dog for clinical improvement and will conduct repeat biopsies to identify any organisms. Expect the possibility of a relapse within a few months to a year after the initial therapy. Your veterinarian will recommend rechecking your dog’s condition at least every two months following the completion of the initial treatment. The prognosis for a successful cure is very uncertain.