Diagnosis and treatment of Leishmania in dogs

This article details the diagnosis and treatment of canine leishmaniosis in dogs. It covers key aspects such as clinical signs, diagnostic tests (serology, PCR), clinical staging, and comprehensive treatment protocols. Learn about drug options, side effects, and essential monitoring for effective Leishmania management.

Canine leishmaniosis (CanL) is a vector-borne disease caused by Leishmania infantum. The disease is endemic in several countries across the world, including Spain, Portugal, Italy, and Greece. It is also an important concern in non-endemic countries, where movement of dogs between endemic and non-endemic countries (imported animals, re-homing, owner´s holidays) may occur. 

Infection is transmitted to the dermis of the host by the sand fly, whereby progeny is disseminated by the lymphatic system. Other routes of infection include transfusion of blood products from infected dogs, vertical and venereal transmission. There is a long incubation period of months to years.

Clinical signs of Leishmania in dogs

Figure 1. Prevalence of particular clinical signs of leishmaniasis in dogs. See reference list for data sources.

Diagnostic tests for  leishmaniasis in dogs

1. 1. Complete blood count:
      1. Non-regenerative anaemia 
      2. Thrombocytopenia
   2. Biochemistry: 
      1. Hyperglobulinaemia (polyclonal beta/gammaglobulinaemia)
      2. Hypoalbuminaemia
      3. Decreased albumin/globulin ratio
      4. Renal azotaemia 
      5. Increased liver enzymes
   3. Urinalysis:
      1. Proteinuria
   4. Blood pressure: 
      1. Hypertension (30-62% of dogs)

Specific testing for leishmaniasis

1. 1. Serology:
      1. Qualitative 
         1. Good specificity but low sensitivity (high risk of false negative results) (especially those dogs with low antibody titers or infected dogs without clinical signs). 
         2. If there is strong clinical suspicion of leishmaniasis, run a quantitative test. 
      2. Quantitative (IFAT and ELISA)
         1. High antibody titre: confirms the diagnosis in a dog with clinical or clinicopathological signs compatible with leishmaniasis
         2. Low antibody titre: does not exclude leishmaniasis and needs further investigation. 
      3. What happens if an animal has been vaccinated? Types of vaccines available:
         1. Letifend® (Leti): 
            • Rapid test or quantitative IFAT or ELISA do not detect vaccinal antibodies.
         2. CaniLeish® (Virbac), Leish-Tec® (Hertape Calier): 
            • Rapid test may detect vaccinal antibodies.
            • Quantitative IFAT or ELISA will detect vaccinal antibodies.
   2. Cytology or histology (see photo): 
      1. Detects Leishmania spp amastigotes
      2. Samples needed: lymph node, spleen, liver, skin lesions
      3. Negative result: may or may not have leishmaniasis
      4. Positive result: confirms leishmaniasis
         
         
   3. Polymerase chain reaction (PCR): 
      1. Detects Leishmania spp DNA
      2. Samples needed: bone marrow, spleen, liver, lymph nodes, skin lesions
      3. Negative result: may or may not have leishmaniasis
      4. Positive result: The dog harbours the infection, although it may never develop clinical disease.

It is not recommended to treat the dogs just on the basis of a PCR result. 

Putting all the pieces together

(From Paltrinieri et al., 2016)

Clinical Staging based on Leishvet

Consider clinical staging in all patients after a diagnosis of leishmaniasis has been made. The clinical staging system will guide you in making therapeutic decisions and in determining the prognosis. Clinical staging is a dynamic process and the same patient can move from one grade to the other during their life.

Table 1 - Clinical Staging in Dogs with CanL. Modified from https://www.leishvet.org/fact-sheet/clinical-staging

Treatment of Leishmania in dogs

The most common drugs used for treating canine leishmaniosis (CanL) are a combination of meglumine antimoniate and allopurinol or miltefosine and allopurinol. Type of treatment will depend on the clinical stage. How intensive this treatment is should also depend on the geographic region where the patient lives (endemic vs not-endemic) and other concurrent conditions, such chronic kidney disease or glomerular disease.

It is unlikely that treatment for CanL will completely eradicate the parasite, even if the dog has recovered clinically. Therefore, regular monitoring of clinical signs and serology is highly recommended. In endemic regions, reinfection might also account for relapse of CanL.

The vast majority of the dogs will show clinical improvement over the first month of treatment, although some others will require a longer period of time.

Table 2 - Treatment will depend on clinical grade. Meglumine and allopurinol seems to be the most effective treatment in controlling active CanL.

Doses for treatment protocols:

1. 1. Allopurinol alone:
      1. Dose: 10 mg/kg/12h PO for at least 12 months. 
      2. Allopurinol can be stopped whenever there is resolution of physical and clinicopathological signs and there is a marked decrease in the antibody levels (e.g. 4-fold decrease or a very low titre, for example, 1-2 fold higher than the threshold of the laboratory). Minimum recommended treatment 6-12 months
      3. If allopurinol-related side effects develop, these are the options:
         • Start a low-purine diet; we recommend this for all dogs on allopurinol
         • Reduce allopurinol to SID, OR
         • Start dietary nucleotides and active hexose correlated compounds (Impromune®) for at least 6 months. Impromune dosing is <10kg 0.5 tablet daily, 10-25kg 1 tablet daily and >26kg 2 tablets daily  OR
         • Start domperidone at 0.5mg/kg/PO/SID for 30 days every 4 months with or without dietary nucleotides and active hexose correlated compounds (Impromune®)
   2. Meglumine antimoniate + allopurinol +/- Impromune®:
      1. Meglumine antimoniate: 100mgmg/kg SC SID for 4 weeks.
      2. Allopurinol: 10mg/kg/q12h PO for at least 6-12 months.
      3. Impromune®: dogs <10kg 0.5 tablet daily, 10-25kg 1 tablet daily and >26kg 2 tablets daily  OR
   3. Miltefosine + allopurinol +/- Impromune®:
      1. Miltefosine: 2mg/kg/q24h PO for 28 days.
      2. Allopurinol: 10mg/kg/q12h PO for at least 6-12 months.
      3. Impromune®: dogs <10kg 0.5 tablet daily, 10-25kg 1 tablet daily and >26kg 2 tablets daily  OR symptomatic treatment may be needed alongside leishmania treatment.

To access the leishcidal drugs will require SIC/STA from VMD, importers include:

• Milteforan: Merlin vet, Virbac
• Meglumine; Merlin vet, Virbac

There is a study suggesting concurrent use of Impromune with Allopurinol for 2 years improved parasitic load and renal parameters so if funds permit consider using both drugs.

In dogs experiencing relapse, Artemisia is being used, it increases free radical production that damages the parasites.

Domperidone is also used for some patients at the dose above every 4 mths in low-seropositive dogs and they were shown to be significantly less likely to develop  disease. In medium to high positive dogs no difference was found with its use.

Monitoring during treatment of CanL

1. In dogs receiving treatment for CanL
2. In dogs that have fully recovered from CanL to ensure that any relapse is detected and treated promptly. 

1. During treatment: 1 month after initiation of therapy and then every 3-4 months.
2. After clinical recovery and off treatment: at least every 6 months.
3. It is recommended reevaluating the renal parameters 3-7 days after initiation of meglumine antimoniate to identify possible nephrotoxicity at an early stage 
4. If gastrointestinal signs develop while using meglumine, treatment should be stopped and the possibility of pancreatitis should be investigated 
5.  

1. Clinical history and physical examination, weight check
2. Complete haematology, biochemistry, urinalysis (including UPCr) Stage the renal disease after finishing the leishmanicide treatment
3. Quantitative serology/antibody titres
   1. If on treatment, only after 6 months after initiation of treatment (not before, due to long half-life of the antibodies)
4. Serum protein electrophoresis

References

Segarra et al. Randomized, allopurinol-controlled trial of the effects of dietary nucleotides and active hexose correlated compound in the treatment of canine leishmaniosis. Veterinary Parasitology (2017); 239 50–56 

Roura et al. Canine leishmaniosis and kidney disease: Q&A for an overall management in clinical practice. JSAP (2020); 1–19

Solano-Gallego, L. et al. (2011), ‘LeishVet guidelines for the practical management of canine leishmaniosis’, Parasit. Vectors 4, 86.

Solano-Gallego L, Cardoso L, Pennisi MG, Petersen C, Bourdeau P, Oliva G, Miró G, Ferrer L, Baneth G. (2017), ‘Diagnostic Challenges in the Era of Canine Leishmania infantum Vaccines’, Trends Parasitol, Sep;33(9), pp. 706-717. 

Paltrinieri S, Gradoni L, Roura X, Zatelli A, Zini E. Laboratory tests for diagnosing and monitoring canine leishmaniasis. Vet Clin Pathol. 2016 Dec;45(4):552-578.