Clinically healthy infected cats are antibody-positive (and/or PCR-positive) cats with no clinical signs and clinicopathological abnormalities compatible with FeL. These cats may have coinfections or other diseases, and it is recommended to follow up L. infantum infection considering their risk to develop FeL (Figure 11).

High levels of antibody positivity (i.e. in case of IFAT > 3 dilutions over the validated cut-off value) detected by quantitative serology (IFAT, ELISA or DAT) confirm diagnosis in cats with a risk of exposure to L. infantum infection and suggestive clinical signs and/or clinicopathological abnormalities (Table 1). However, cytological evaluation of any skin, mucosal, or mucocutaneous lesions, enlarged lymph nodes or spleen, or any other lesion evidenced by imaging and endoscopy should be performed. Compatible cytological findings (such as lymphoid hyperplasia in lymphoid organs; and neutrophilic and/or macrophagic as well as lymphoplasmocellular inflammation) and/or visualization of amastigotes is suggestive or confirmatory of L. infantum infection, respectively (Figures 11-14). Cytology also permits to detect comorbidities. Histopathological evaluation and/or Leishmania immunohistochemistry may be required based on each patient’s list of problems.

In antibody-negative or low-positive cats with no evidenced tissue lesions, Leishmania amastigotes (cytology evaluation) or parasite DNA (PCR) can be detected in bone marrow, lymph nodes or spleen. However, as comorbidities are possible, they also must be investigated based on the individual list of problems, to confirm a causative role of L. infantum infection in the clinical presentation (i.e. differentiation of infection from disease).

Point-of-care tests validated to detect anti-L. infantum antibodies in cats are currently not available.

The screening of clinically healthy cats by means of quantitative serology and PCR techniques is recommended in endemic areas in case of the following conditions: blood donors, cats requiring chronic immunosuppressive therapies, and before relocating cats to non-endemic areas. Imported/relocated cats must be tested at arrival, but seroconversion can take months and retesting should be considered six months later, in case of presenting compatible clinical signs, before any immunosuppressive therapy or becoming a blood donor. In case of healthy individuals, generally minimally invasive tissue sampling is preferred (blood, lymph nodes and conjunctival swabs) for PCR, however their sensitivity is low and it should be increased by performing multiple tissue PCR testing.

Most FeL case reports are from European and Mediterranean endemic areas where the number of pet cats is high. However, FeL remains rare, as a disease, even in areas where leishmaniosis is common in dogs and feline infection is frequent. It is postulated that cats are therefore less susceptible than dogs to L. infantum infection. However, it cannot be excluded that the disease is still underdiagnosed because it is neglected – or even ignored – by many practitioners, and clinical suspicion is challenging when suggestive signs are lacking, or the clinical presentation is overlooked by signs of a concurrent disease. Moreover, in some endemic areas, the level of cat medical care is generally lower compared to dogs.

About 140 clinical cases have been reported in Europe during the last 3 decades (Italy, France, Spain and Portugal) with some cases diagnosed in Germany, Switzerland and the UK in cats imported from endemic regions.

Host factors predisposing to susceptibility probably exist, as roughly half of the reported clinical cases have been observed in cats that could have had an impaired immune system secondary to FIV or feline leukemia virus (FeLV) or dual FIV and FeLV coinfections, long-term immune-suppressive therapies, malignant neoplasia, or debilitating diseases. However, the level of evidence of this observation is low as it is not supported by controlled studies.

The disease has been diagnosed in adult cats (2-21 years) with a median age of 9 years.

The incubation period can last years as suggested by clinical manifestations observed in non-endemic areas several years after the relocation of cats from endemic areas.

The course of disease is mostly chronic and progressive.

Similar to canine leishmaniosis, cutaneous and mucocutaneous lesions and lymphadenomegaly are the most frequently reported manifestations (Table 1). Ulcers and nodules are the most common cutaneous and mucocutaneous lesions observed, mainly distributed on the head or on distal limbs (Figures 2-8). Hemorrhagic nodules are atypical skin lesions (Figure 9).

Uveitis is a frequent ocular lesion (Figure 10) in FeL. Oral lesions consist of nodules (tongue and gingival mucosa).

In recent years, atypical presentations have been reported including upper respiratory tract disease manifested with chronic nasal discharge and severe obstructive syndrome in case of granulomatous inflammation with nodular or infiltrative masses. Other single cases with atypical presentations where the causative role of L. infantum has been documented with presentations of chronic diarrhea, mastitis and cutaneous panniculitis.

The clinicopathological evaluation of cats with leishmaniosis shows hyperglobulinemia with hypergammaglobulinemia frequently (Figure 10), mild normocytic normochromic non-regenerative anemia, and proteinuria.

Most information regarding feline L. infantum infection has come from investigations performed in the Mediterranean Basin and the Middle East.

The prevalence of L. infantum infection in cats, as evaluated in studies performed in many countries of the Mediterranean Basin and the Middle East (Albania, Algeria, Cyprus, Egypt, France, Germany, Greece, Iran, Israel, Italy, Portugal, Qatar, Spain, Turkey) from the 1980’s is variable. Both antibody and blood molecular prevalences have been investigated with diverse serological and PCR techniques in populations of cats with different characteristics and in countries with different socio-economical situations, and this can contribute to the wide range of positivity observed (seropositivity: 0-75.0%; blood PCR positivity: 0-60.7%). However, prevalence of Leishmania infection in cats is commonly lower than the prevalence in dogs in the same area.

Some studies have found that coinfections with other pathogens are detected in Leishmania-infected cats. However, this finding can be accidental and mostly due to a high prevalence of the co-infecting microorganisms in cats (e.g.: Bartonella, Toxoplasma). Conversely, there is evidence that feline immunodeficiency virus (FIV) seropositive cats have a higher risk of being affected by L. infantum infection.

Cats are potentially infected by the same Leishmania spp. that infect dogs and humans in endemic areas all over the world (Figure 1). Leishmania infantum is the most frequently reported species infecting cats, and this fact sheet is based on published data on L. infantum infection and the associated feline disease, mostly reported in the Mediterranean Basin and Middle East region. However, this species is largely described in cats also in Central and South America.

Leishmania infantum is transmitted to cats by sand flies, as they have been shown to feed on cats and to be infected after feeding on naturally infected cats. Moreover, sand flies infected from cats transmitted the infection to dogs. Considering that infected cats are a source of infection to sand flies and generally suffer from chronic infection, LeishVet postulates that, based on new insights in the epidemiology of leishmaniosis, infected cats can represent an additional domestic reservoir for L. infantum to humans, dogs, and other susceptible hosts, including cats themselves. However, there is some evidence that cats are likely less infectious to sand flies than dogs.

Non-vectorial transmission of L. infantum (blood transfusion, vertical transmission, mating, aggressive interactions) is documented in dogs but not yet in cats. However, Leishmania DNA has been detected by PCR in the blood of some healthy cats (see “Diagnosis” and “Prevention” sections).