Canine Visceral Leishmaniasis: Dermatological Aspects and Associated Dermatoses

Background: Visceral leishmaniasis (VL) is a zoonotic disease caused by Leishmania chagasi (syn. L. infantum). The dog is the main reservoir for this infectious agent in the urban environment. Among the various systemic signs of viscerotropic infection by L. chagasi, cutaneous lesions, including exfoliative dermatitis, cutaneous ulcers and nodules, alopecia, papular or pustular dermatitis, and onychogryphosis, are the most common in dogs. This study aimed to describe the major cutaneous lesions, evaluate the skin parasite L. chagasi by PCR, and investigate the main dermatoses associated with this zoonosis. Materials, Methods & Results: This study evaluated 50 seropositive dogs of various breeds and sizes for VL by ELISA and IFA and for the dermatological signs associated with VL. Moreover, molecular analysis of skin fragments was performed with primers 150 and 152 for the genus Leishmania, and the species was verified as L. chagasi with RV1 and RV2 primers. Deep skin scraping for mites and fungal culture analysis were performed in all dogs. Of the 50 dogs, 15 (30%) were free of systemic or cutaneous signs; however, changes in skin and annexes were observed in 35 (70%) dogs. Thirty-one dogs (62%) presented infection with dermatophytes, 26 (83.9%) with Microsporum sp., and 5 (16.1%) with Trichophyton sp.; only one dog showed parasitism by Sarcoptes scabiei. A statistically significant association was observed between skin alterations and dermatological infection by dermatophytes (P = 0.61). Of the 29 dogs from which skin fragments were used to perform PCR with specific primers, 19 (65.5%) showed L. chagasi DNA amplification. Discussion: Symptomatic dogs are more common than asymptomatic ones; therefore, sampling was set up in the hospital for reagents dogs with clinical suspicion of this zoonosis. Dermatological signs accounted for 70% of the clinical symptoms presented by the dogs, which were evaluated as described by other authors. Exfoliative dermatitis was the most common skin lesion followed by onychogryphosis and alopecia. This is because of granulomatous or pyogranulomatous inflammation, inflammation in different structures of the skin, or deposition of immune complexes. Only few studies have described the co-existence of VL and dermatophytosis in dogs. We found dermatophyte fungal infection in more than half of the dogs (70%), most frequently Microsporum sp. followed by infection with Trichophyton sp. Regarding the clinical signs, no statistical difference was observed between the dogs with and without dermatophyte infection, which reinforces the lack of specificity in clinical signs that may hinder the diagnosis of both diseases when present as co-morbidities or in isolation. The high frequency of dermatophytosis in dogs with VL may result from a compromised immune system. L. chagasi DNA detected in 65.5% of samples tested by conventional PCR can be related to the host's immune response, as well as to the uneven distribution of the parasite in different tissues. These results support the high frequency of skin changes and concomitant skin diseases like ringworm observed in dogs with LV, highlighting the importance of researching other differential diagnoses in endemic areas.