No abstract

BackgroundRhipicephalus sanguineus is a ubiquitous tick responsible for transmitting Ehrlichia canis and most likely Anaplasma platys to dogs, as either single or co-infections. The objective of this study was to assess the effects of either simultaneous or sequential experimental infections with E. canis and A. platys on hematological and serological parameters, duration of infection, and efficacy of doxycycline therapy in dogs infected with one or both organisms. Six dogs per group were either uninfected, A. platys infected, E. canis infected, A. platys and E. canis co-infected, A. platys infected and E. canis challenged or E. canis infected and A. platys challenged at day 112 post-infection (PI). Doxycycline treatment was initiated at 211 days PI, followed by dexamethasone immunosuppression beginning 410 days PI.ResultsInitially, transient decreases in hematocrit occurred in all groups infected with E. canis, but the mean hematocrit was significantly lower in the A. platys and E. canis co-infected group. All dogs except the controls developed marked thrombocytopenia after initial infection followed by gradually increased platelet counts by 112 days PI in groups with the single infections, while platelet counts remained significantly lower in the A. platys and E. canis co-infected group. Both sequential and simultaneous infections of A. platys and E. canis produced an enhanced humoral immune response to A. platys when compared to infection with A. platys alone. Likewise, co-infection with E. canis and A. platys resulted in a more persistent A. platys infection compared to dogs infected with A. platys only, but nearly all A. platys infected dogs became A. platys PCR negative prior to doxycycline treatment. E. canis infected dogs, whether single or co-infected, remained thrombocytopenic and E. canis PCR positive in blood for 420 days. When treated with doxycycline, all E. canis infected dogs became E. canis PCR negative and the thrombocytopenia resolved. Despite immunosuppression, neither A. platys nor E. canis DNA was PCR amplified from doxycycline-treated dogs.ConclusionsThe results of this study demonstrate that simultaneous or sequential infection with A. platys and E. canis can alter various pathophysiological parameters in experimentally infected dogs, and because natural exposure to multiple tick-borne pathogens occurs frequently in dogs, awareness of co-infection is important in clinical practice.

No abstract

The occurrence of Dirofilaria immitis antigen and antibodies against tick-borne pathogens in French dogs has been analysed based on 1,050 blood samples. Serum samples of 919 dogs (group A) were sent for a variety of diagnostic investigations, further 131 dogs (group B) were tested for a tentative diagnosis of heartworm disease. All samples were tested for D. immitis antigen. Samples in group A were also tested for specific antibodies against three tick-borne pathogens (Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and Ehrlichia canis). Results were plotted in geographical maps. Occurrence of D. immitis antigen in group A (0.22%; 95 % CI: 0.03-0.78%) was significantly lower (p < 0.0001) than in group B (6.87%; 95% CI: 3.19-12.64%). Heartworm infections in both groups were regionally restricted to the areas of Bouches-du-Rhône in the South of France and Corsica. In group A, the calculated seroprevalence was 2.72% (95% CI: 1.77-3.99%) for A. phagocytophilum, 1.09% (95% CI: 0.52-1.99%) for B. burgdorferi and 0.33% (95% CI: 0.07-0.95%) for E. canis with a distribution of the positive cases throughout the country. This study represents the first data of A. phagocytophilum seroprevalence in the French dog population.

The Central Upper-Rhine (Baden-Württemberg, Germany) is one of the warmest regions in Germany and also harbours abundant numbers of mosquitoes. Case reports on presumably autochthonous occurrence of Dirofilaria spp. were reported previously and were a reason for a further investigation into the occurrence of vector-borne pathogens. For this purpose, 44 hunting dogs from the Central Upper-Rhine region were tested between 4(th) and 29(th) June 2007. The blood samples were tested using the Knott's test and IDEXX SNAP 4Dx test. The Knott's test revealed unsheathed microfilaria identified as Dirofilaria repens by PCR in 3 dogs with no history of travelling (6.8%; 95% CI: 2.4-18.2%). The seroprevalence for Anaplasma phagocytophilum was 43.2% (95% CI: 29.7-57.8%), but only 4.5% (95% CI: 1.3-15.1%) for antibodies to Borrelia C6 peptide. Dirofilaria immitis antigen was not detected in any of the samples. A further 288 blood samples from non-hunting companion dogs of the Central Upper-Rhine region were tested negative for heartworm antigen between February and August 2007.