Canine leptospirosis in Switzerland—A prospective cross-sectional study examining seroprevalence, risk factors and urinary shedding of pathogenic leptospires

Abstract

Leptospirosis is an important worldwide zoonosis. While human leptospirosis remains rare in Switzerland, the incidence of canine leptospirosis is unusually high compared to other European countries. The aims of this cross-sectional study were to determine the exposure of asymtomatic dogs to pathogenic Leptospira in Switzerland, to characterise risk factors associated with seropositivity and to determine the prevalence of urinary shedding. Sampling was stratified to cover the whole of Switzerland. Sera were tested by microscopic agglutination test for antibodies against a panel of 12 serovars. Urine was tested for pathogenic Leptospira using a LipL32 real-time PCR. Of 377 sera, 55.7% (95%CI 51.2-60.7) showed a reciprocal MAT titre of ≥1:40 and 24.9% (95%CI 20.7-29.4) of ≥1:100 to at least one serovar. Seropositivity (MAT ≥1:100) was most common to serovars Australis (14.9%; 95% CI 11.4-18.6) and Bratislava (8.8%; 95%CI 6.1-11.7), followed by Copenhageni (6.1%; 95%CI 3.7-8.5), Canicola (5%; 95%CI 2.9-7.4), Grippotyphosa (4.5%; 95%CI 2.7-6.9), Pomona (4%; 95%CI 2.1-6.1), Autumnalis (2.7%; 95%CI 1.3-4.2) and Icterohaemorrhagiae (1.6%; 95%CI 0.5-2.9). In unvaccinated dogs (n=84) the prevalence of a MAT titre ≥100 was 17.9% (95%CI 10.7-26.2), with a similar distribution of reactive serovars. Variables associated with seropositivity (≥1:40) to any serovar included age (OR 1.29/year; 95%CI: 1.1-1.5) and bioregion with higher risks in the regions Northern Alps (OR 14.5; 95%CI 2.2-292.7), Central Plateau (OR 12.3; 95%CI 2.0-244.1) and Jura (OR 11.2; 95%CI 1.7-226.7) compared to Southern Central Alps. Dogs living with horses were significantly more likely to have antibodies to serovar Bratislava (OR 4.68;95%CI 1.2-17.2). Hunting was a significant risk factor for seropositivtiy to serovar Grippotyphosa (OR 8.03; 95%CI 1.6-30.8). Urine qPCR positivity was uncommon (1/408 dogs; 0.2%; 95% CI0-0.7). These results demonstrate that dogs in Switzerland are commonly exposed to pathogenic Leptospira; however, the risk of dogs contributing to the spread of Leptospira in the environment appears low.

Leptospiral shedding and seropositivity in shelter dogs in the Cumberland Gap Region of Southeastern Appalachia

“…Several studies on renal carriage of leptospires show a wide range of prevalence among asymptomatic dogs. For example, a recent study from Switzerland reported urinary shedding in 0.2% of tested dogs [24], while a group from Brazil reported a prevalence of 19.8% [25].…”

Leptospira infection and shedding in dogs in Thailand

“…In Ireland, 7.1% (37/525) of dogs were shedding [29], 8.2% (41/500) in the USA [31], 31.1% in Iran [37], and 19.8% of the dogs in Brazil [35]. In a German study, 1.5% (3/200) of healthy dogs were shedding Leptospira [25], and in Switzerland, the shedding prevalence was 0.2% (1/408) [23]. These low European prevalences are probably due to a broader vaccine-induced immunity in the dog population.…”

“…In addition, "dog ownership" was identified as a potential risk factor for humans [17][18][19][20][21][22]. Worldwide studies showed a prevalence of urinary shedding of Leptospira in dogs between 0.2 and 31.1% by PCR [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Shedding can also occur in healthy dogs [23, 25, 31-33, 35, 37].…”

Detection of intraocular Leptospira spp. by real‐time polymerase chain reaction in horses with recurrent uveitis in Belgium

“…Two recent studies noticed a marked increase in human and dog leptospirosis in the Netherlands and in the USA . In Switzerland, it has been shown that dogs living with horses were significantly more likely to have antibodies corresponding to Leptospira interrogans serovar Bratislava . Clinicians should be aware of a possible increase in the number of leptospirosis‐affected horses and dogs in Europe.…”