Phlebotominae (Sandflies) are the only arthropods capable of transmitting Leishmania spp. infection. But, in non-endemic areas without a competent arthropod vector, including Northern European countries and the United States, vertical transmission is the most widespread route. Diagnosis of other cases of canine leishmaniosis (CanL) in these non-endemic areas demonstrates additional potential non-vector transmission pathways of increasing concern including sexual and transplacental transmission, blood transfusion, and dog-to-dog (e.g. aggression with bites). Yearly screening for leishmaniosis in Europe is important, as it can prevent or decrease the spread of CanL and allows dogs to be properly treated and monitored over time.

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Leishmaniosis Symptoms

The most common symptoms of CanL include mild non-regenerative normocytic normochromic anaemia, mild neutrophilia with lymphopenia and monocytosis (stress leukogram), thrombocytopenia, and leukopenia (although, this is less common). Abnormal serum protein electrophoresis results can be seen as a compensatory response or due to renal proteinuria. In dogs with immune-mediated glomerulonephritis, renal azotemia and proteinuria may also be present.

In the early stages of disease, clinical signs are mild and may include lethargy, progressive weight loss, exercise intolerance, lymphadenomegaly, and mild skin lesions such as alopecia and exfoliative dermatitis.

If adequate treatment is not instituted or the diseased dog has a non-protective immune response, then cutaneous manifestations can develop, such as skin ulceration over bony prominences and mucocutaneous junctions. Other signs indicating increasing severity are associated with immune complex deposits including vasculitis (e.g. nasal bleeding), glomerulonephritis (with polyuria, polydipsia), polyarthritis (erratic and sometimes intermittent limping), and eye lesions (conjunctivitis, keratouveitis, retinopathies, etc.).

Other, less common clinical signs have been described, including fever, digestive disorders (ulcerative colitis), neurological (encephalitis), and cardiorespiratory (pneumonitis, chronic rhinitis) signs.

Interpreting Results and Diagnosis

Diagnosing canine leishmaniosis with diagnostic testing is essential because there are two types of patients: clinically healthy infected dogs and sick dogs. The key to diagnosis is to properly differentiate these two patients with the help of the results obtained. After conducting a serological rapid test, determine if the dog is positive—if so, its recommended to pursue further diagnostics to uncover and stage the disease.

First, collect a detailed medical and epidemiological history. Then conduct a complete physical examination with a thorough assessment of body condition, mucous membranes, palpation of lymph nodes, and skin and mucocutaneous junctions. If the patient presents clinical signs of CanL, carry out a quantitative serology by IFAT or ELISA to quantify the humoral response and get a concrete antibody titration.

Then, run nonspecific tests—CBC, biochemistry panel with SDMA, urinalysis with UPC, and protein electrophoresis—to assess the patient's general health condition and see if the parasite has affected the patient in other ways.

There are several methods to confirm the presence of the parasite in dogs with clinical signs and serology consistent with disease. Cytology of the enlarged lymph node cells and/or bone marrow tissue can help confirm Leishmania infection. In addition, three PCR methods are available: conventional PCR, nested PCR, and quantitative PCR. PCR can be performed on DNA extracted from different tissues, blood, biological fluids, and even histological material. Bone marrow, lymph node, spleen, or skin are the most sensitive tissues for PCR diagnosis while blood, buffy coat, and urine reduce the sensitivity of this molecular diagnosis.

Leishmaniosis Staging

Once CanL has been confirmed, it's important to determine the stage of the disease, so you can properly treat the patient. Clinical staging of canine leishmaniosis (as developed by LeishVet and used most frequently) is divided into four stages based on clinical signs, quantitative serology, blood tests, and urinalysis results. This classification helps to determine an appropriate treatment protocol and establish a prognosis.

Leishmaniosis Treatment

After clinical staging has been established, discuss the specific and supplementary treatment with the pet owner following LeishVet's guidelines. Not all dogs that test positive will require treatment, and overtreating could create drug resistance over time. So, veterinarians should tailor their treatment to the specific needs and conditions of the individual patient.

Dogs under treatment with an appropriate protocol for their clinical and parasitological situation need to be routinely monitored. Start with an initial check 30 days after treatment to evaluate whether the treatment was successful. Afterward, during the first year, recheck every four months with a physical exam, blood count, hepatorenal biochemical profile, serum protein electrophoresis, quantitative serology and quantitative PCR, if applicable. From the second year onward, if the dog is stable, reduce to two checkups per year and then every 6-12 months after that as needed, depending on the clinical course. Leverage client handouts to help underscore this important information.

Diagnosing leishmaniosis is the cornerstone of the clinical management of this important disease. Following LeishVet's guidelines and continuing to monitor the patient's recovery is necessary to reduce the spread of disease and improve the pet's health.

"Information in this article was sourced from Leishvet."

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