Papular dermatitis due to Leishmania infantum infection in seventeen dogs: diagnostic features, extent of the infection and treatment outcome

Abstract

BackgroundThis study describes immunological responses, diagnostic features, follow up and treatment outcomes from seventeen dogs with papular dermatitis due to Leishmania infection diagnosed by cytology or real time-PCR.MethodsSpecific Leishmania humoral and cellular immune responses were evaluated by means of an immunofluorescence antibody test in all cases and a delayed-type hypersensitivity (DTH) reaction to leishmanin in eight cases. The extent of infection was studied in several tissues including blood, lymph node, conjunctival and oral swabs, by means of PCR, at the time of diagnosis and during follow-up. Culture was performed on nine dogs from cutaneous lesions and lymph node aspirates and molecular typing was carried out on isolates based on ITS-1, ITS-2 and Haspb gene sequencing analysis.ResultsCytological and molecular results from fine needle aspirates of papules were diagnostic in 8 out of 13 (61.5%) cases and in 14 out of 15 dogs (93.3%), respectively. In all dogs, specific anti-Leishmania antibody levels were low or absent. Blood and lymph node PCRs and lymph node culture were negative in all dogs. Three out of the nine dogs (33%) were positive by culture from cutaneous lesions. The three isolates were identified as ITS type A, however, polymorphism was observed in the Haspb gene (PCR products of 626 bp, 962 bp and 371 bp). DTH response was positive in all tested dogs at the time of diagnosis. The majority of dogs were successfully treated with only N-methylglucamine antimoniate, after which cutaneous lesions disappeared or were reduced to depigmented, flattened scars. All dogs remained seronegative and the majority of dogs were negative by PCR in several tissues during follow-up.ConclusionsThis study points out that papular dermatitis due to L. infantum is probably an underestimated benign cutaneous problem, associated with a parasite specific cell mediated immunity and a poor humoral immune response. Papular dermatitis is seen in young dogs, and appears to be a mild disease with restricted parasite dissemination and a good prognosis. PCR can be used as a non-invasive method to routinely evaluate papules if Leishmania infection is suspected in cases in which parasites are not visualized by cytology.

Histological and parasitological distinctive findings in clinically-lesioned and normal-looking skin of dogs with different clinical stages of leishmaniosis

“…Moreover, it has been demonstrated that dissemination to the skin varies between dogs, being greater in sick and infectious dogs [20]. Therefore, lack of these changes in the majority of dogs with normal-looking skin with stage I-mild disease would further suggest a protective immune response in these dogs able to control parasite dissemination at the site of parasite inoculation and multiplication as previously proposed [11, 18]. …”

Quantitative PCR for the diagnosis of cutaneous leishmaniasis from formalin-fixed and paraffin-embedded skin sections

“…Accordingly, it is not surprising that the sensitive PCR 61 technology has gained increasing importance as an alternative method to substantiate the histological 62 diagnosis of cutaneous leishmaniasis. However, PCR performed on histological slides is often 63 complicated by the fact that DNA extracted from formalin-fixed and paraffin-embedded tissue may be 64 partially degraded and/or contains components that inhibit PCR[10]. In this context, the quality of the DNA extracted from such fixed material and the robustness of a particular amplification procedure 66 determine the diagnostic operating characteristics of a PCR for histological samples.…”

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“…Clinical signs have been observed as early as six months of age (Tarantino et al, 2001;Lombardo et al, 2014), but often it takes more than a year for a susceptible dog to develop the first clinical signs or clinicopathological abnormalities following natural exposure to sandflies bites in an endemic setting .…”