Prevalence and risk factors for selected canine vector-borne diseases in Greece

Abstract

Background Canine vector-borne diseases (CVBDs) represent a wide group of diseases of major significance for canine health. In addition to their veterinary importance, many of these diseases are of great zoonotic concern, posing a risk of potential transmission to humans. To date, there has been scant knowledge regarding the prevalence, distribution and risk factors of CVBDs in Greece. Therefore, the objectives of the present study were to update the current knowledge on the seroprevalence of Dirofilaria immitis , Anaplasma spp., Ehrlichia spp. and Borrelia burgdorferi ( sensu lato ) in dogs in Greece and, furthermore, to assess possible environmental and any other risk factors associated with these infections. A total of 1000 apparently healthy and randomly selected dogs, presented in veterinary clinics, were involved at the national level ( n = 66 municipalities). Serum samples were obtained from each individual dog and were tested using the SNAP ® 4Dx ® Plus kit from IDEXX Laboratories. Possible risk factors were assessed using binary regression models, including dogs’ lifestyle, climatological parameters and the altitude of the region. Results Overall, 21.8% (95% CI: 19.4–24.5%) of the sampled dogs were found to be seropositive to at least one of the four pathogens examined. The most prevalent pathogen was Ehrlichia spp. (12.5%, 95% CI: 10.6–14.7) followed by D. immitis (9.0%, 95% CI: 7.8–11.5) and Anaplasma spp. (6.2%, 95% CI: 4.9–7.9). The lowest prevalence (0.1%) was recorded for B. burgdorferi ( s.l. ) where only one dog was found to be positive. Among the examined risk factors, low mean temperature was found to increase the prevalence of Ehrlichia spp. ( P ≤ 0.001) and Anaplasma spp. ( P ≤ 0.001), while low minimum temperature increased the prevalence of D. immitis ( P ≤ 0.001). In addition, low total annual rainfall had an effect of the prevalence of Ehrlichia spp. ( P ≤ 0.01). Altitude also had a significant effect on the prevalence of D. immitis ( P ≤ 0.05) and Anaplasma spp. ( P ≤ 0.01). Conclusions To our knowledge, this is the first large-scale seroepidemiological study of CVBDs in Greece. It has been evidenced that environmental factors such as temperature, rainfall and altitude can influence the prevalence and distribution of CVBDs.

Mapping the canine vector-borne disease risk in a Mediterranean area

“…None of the dogs examined were seropositive for Borrelia spp., which is in agreement with the very low prevalences recorded in whole of Greece [14,15]. Within a given area, the risk of animal/human infection with B. burgdorferi (s.l.)…”

“…Moreover, Ehrlichia seropositive dogs were not identified on the Ionian Sea islands. In the present study, the overall seroprevalence recorded was lower than that found in studies recently conducted in the whole of Greece (a prevalence of approximately 12.5%) with similar sample size and methods applied [14,15]. In these studies, however, the majority, if not all, of samples originated from mainland Greece.…”

“…The failure to detect Anaplasma DNA by PCR could be due to chronic infections, in which parasites are not always present in the blood, or to cross-reactions leading to false positive results in serological testing [31]. Similar to the results for Ehrlichia, the overall seroprevalence recorded in the present study was lower than that in a recent study where samples originated mainly from mainland Greece [14]. Likewise, in the study including samples from Aegean islands, Anaplasma spp.…”

“…A cross-sectional study was conducted in canine populations from different Greek Islands in order to evaluate the seroprevalence of CVBPs. In total, 4 islands were selected based on their geographical location [(i) situated in both Ionian and Aegean seas; (ii) covering areas West to East of the country; (iii) having different landscapes and climatic conditions], the size of their native dog population (traditionally islands like Leros and Paxoi despite their size are known for the high hunting dog population), and previous records (published or personal communication) of CVBD presence [11,12,[14][15][16][17]. Altogether, 1154 dogs with different lifestyles (indoors/outdoors), irrespective of age and breed were randomly sampled and examined for the presence of clinical signs suggestive of CVBDs.…”

“…19.8 million international airport arrivals from January to October 2018, with 4.5 million arrivals on Crete alone [10]), many of whom travel with their pets. Overall, located in the Mediterranean basin with a suitable environment for pathogen transmission and poorly managed stray dog populations, Greece has been repeatedly reported as an area highly endemic for various CVBDs [11][12][13][14][15][16][17]. However, landscape and microclimate conditions are not identical throughout the country and this stresses the need for comprehensive knowledge on the distribution and abundance of various CVBPs within native dog populations and across different islands, which currently is missing.…”