Seroprevalence and risk factors associated with Leishmania infantum in dogs in Sardinia (Italy), an endemic island for leishmaniasis

Abstract

Leishmaniasis is a widespread, vector-borne parasitosis causing clinical manifestations in animals and in humans. In dogs, Canine Leishmaniasis has been reported in as much as 50 countries and the Mediterranean basin is known to be one of the most affected zones. Within these areas, the Island of Sardinia (Italy) has long been considered endemic for leishmaniasis and the presence of two arthropod vectors has recently been reported there. Nevertheless, to date, no epidemiological surveys regarding CanL have been carried out on the island. Hence, for the first time, the seroprevalence and the risk factors were investigated. Blood samples, as well as clinical and general information from 1.147 dogs, were collected and analyzed. Dogs consisted of two distinct populations, namely “owned dogs” and “kennel dogs.” Anti-Leishmania IgG antibodies were detected using IFAT and samples were scored as positive at a cut-off dilution of 1:80. Data was analyzed using a Chi-squared test and bivariate and multivariate analyses were performed. Overall, 15.4% of dogs were found to be infected with CanL while only 44.1% of these animals exhibited clinical signs. Owned dogs (27.2%) were found to be infected more often than kennel dogs (10.6%); male dogs were found to be more frequently infected than female dogs and the number of infected animals increases with age. The present survey confirmed the endemic nature of leishmaniasis in Sardinia with a similar seroprevalence as mainland Italy. The results obtained serve as validation for the hypothesis that, in endemic areas, clinical CanL representations constitute only a fraction of the leishmaniasis cases.

Seroprevalence and risk factors associated with exposure to Leishmania infantum in dogs, in an endemic Mediterranean region

“…A significant difference in prevalence was found between sexes, with males showing higher seroprevalence. Other authors reported a higher seroprevalence in males [ 34 , 36 ]. This result could be due to the roaming behaviour of male dogs in rural areas or the outdoor attitude of male guard dogs, as reported in a study carried out in the study area [ 21 ].…”

“…seropositivity increased with the dog age [14,17,[32][33][34][35]. This evidence could be attributed to repeated exposure to Leishmania during the years.…”

“…This difference could be explained by a selection bias because owned dogs were more frequently tested for clinical suspicion or follow up after treatment, whereas kennel dogs were mainly sampled at kennel admittance. However, recent serosurveys on CanL reported higher risk for seropositivity in owned dogs compared to kennel [34,35].…”

Early onset of clinical leishmaniosis in a litter of pups with evidence of in utero transmission

“…However, transmission in the absence of the vector has been reported, including infection due to blood transfusion [ 4 , 5 ], vertical transmission in the absence of known suitable biological vectors [ 6 – 8 ], and venereal transmission from the semen of naturally infected males to susceptible bitches [ 9 , 10 ]. The incubation period after sand fly infection can extend from 3 months to 7 years [ 11 ], and clinical cases of leishmaniosis of pups younger than 5 months of age are extremely rare [ 12 – 14 ].…”

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“…A significant difference in prevalence was found between sexes, with males showing higher seroprevalence. Other authors reported a higher seroprevalence in males [34,36]. This result could be due to the roaming behaviour of male dogs in rural areas or the outdoor attitude of male guard dogs, as reported in a study carried out in the study area [21].…”