Canine leishmaniasis is a chronic parasitic disease caused by the protozoan Leishmania infantum, transmitted through the bite of the female sandfly (Phlebotomus perniciosus). In Spain it is endemic virtually throughout the territory, with particular prevalence in the Mediterranean basin and Andalusia. The province of Seville, with its long hot summers and the humid microclimate along the Guadalquivir river, creates ideal breeding conditions for the sandfly vector, making it one of the highest-risk areas in the country. It is estimated that between 20 and 40% of dogs in endemic areas are infected, although many remain asymptomatic for years.
How It Is Transmitted and Who Is at Risk
The sandfly is a tiny insect, barely 2-3 mm, with twilight and nocturnal activity mainly between May and October. Only the female bites to obtain blood and transmit the parasite. Dogs that live or sleep outdoors are at greater risk of exposure, as are those living in rural or peri-urban areas with dense vegetation.
Leishmaniasis also has zoonotic implications: the dog is the main reservoir for human infection, especially in immunocompromised individuals. For this reason, its control is important both from a veterinary and a public health perspective.
Symptoms: A Disease with Many Faces
The clinical presentation is highly variable. Some infected dogs never develop the disease due to an effective cellular immune response; others progress to severe forms within months. The most frequent signs include:
- Skin lesions: periocular alopecia (giving a "spectacles" appearance), scaling, ulcers on bony prominences (elbows, knees, muzzle), skin thickening and depigmentation.
- Onychogryphosis: exaggerated growth and deformity of the nails, very characteristic of the disease.
- Progressive weight loss despite maintaining appetite.
- Epistaxis: nosebleeds due to involvement of the nasal mucosa.
- Generalized lymphadenopathy: enlarged lymph nodes easily palpable.
- Renal lesions: glomerulonephritis that can progress to chronic kidney disease, the leading cause of death in dogs with advanced leishmaniasis.
- Uveitis and conjunctivitis in some cases.
Diagnosis
Diagnosis is based on the combination of serology, PCR and cytology or histology. Serology detects antibodies against Leishmania; high titers are highly suggestive in symptomatic dogs. PCR on blood or bone marrow offers greater sensitivity and can confirm infection even in seronegative animals with compatible symptoms.
Before starting treatment, it is essential to evaluate kidney function through blood and urine tests: creatinine, urea, proteinuria and the urinary protein/creatinine ratio (UPC) will determine the disease stage according to the LeishVet classification, which guides prognosis and treatment.
Treatment and Follow-up
First-line treatment combines miltefosine (oral, 2 mg/kg/day for 28 days) with allopurinol (oral, 10 mg/kg/12h for an extended period, months or years). Allopurinol inhibits parasite metabolism and maintains clinical remission. An alternative is meglumine antimoniate (injectable), although the emergence of resistance has reduced its use.
Treatment response is monitored through clinical, serological and biochemical checks every 3-6 months. Leishmaniasis has no definitive cure: the goal is to achieve clinical remission and control the parasite burden to preserve quality of life and kidney function.
Prevention: The Key Is Sandfly Protection
Prevention combines several strategies:
- Sandfly repellents: collars with deltamethrin (Scalibor) or spot-on treatments with permethrin offer effective protection. They should be applied from May to October, with renewals according to the product data sheet.
- Vaccination: the CaniLeish (Virbac) and Letifend (Laboratorios Leti) vaccines are available in Spain. They are recommended for seronegative dogs living in endemic areas. They do not cure or provide 100% protection, but significantly reduce the risk of clinical disease.
- Avoiding nocturnal exposure: keeping dogs indoors during twilight hours in summer reduces exposure to bites.
