[A descriptive epidemiological study on canine babesiosis in the Lake Geneva region]

A descriptive study was carried out in the district of the Lake Geneva between March 1, 2005 and August 31,2006 to assess the incidence and prevalence of canine babesiosis, to genotype the Babesia species occurring, to assess the most frequently clinical signs found and to address the potential of autochthonous transmission. This included a data assessment on the different tick-populations occurring in the area and on the prevalence of Babesia-DNA in these ticks. A total of 56 veterinary practices participated in the study. By blood smear and PCR, Babesia canis canis was found in 12 out of 21 cases with suspected babesiosis. In an additional 13th case, the parasite could only be detected by PCR. All autochthonous cases originated from the Western part of the Lake Geneva region. Clinical signs in affected dogs included inappetence, apathy, anemia, fever, hemoglobinuria and thrombocytopenia. There were no risk factors with regard to age, sex and breed. Most cases were diagnosed during the spring periods of 2005 and 2006 (11 cases) and two cases in autumn 2005, coinciding with the main activity period of Dermacentor reticulatus, the main vector of B. canis canis. A total of 495 ticks were collected on patients by the veterinarians, 473 were identified as Ixodes sp., 7 as Rhipicephalus sanguineus and 15 as Dermacentor reticulatus. While Ixodes sp. was found in the whole study area, D. reticulatus and R. sanguineus occurred only in the Western part till Lausanne. PCR and sequencing yielded B. canis canis positivity in 3 D. reticulatus specimen, these three ticks were collected from two different dogs both suffering from babesiosis. All R. sanguineus were negative by Babesia-PCR. Global warming, ecological changes in the potential habitat of ticks, increasing host- and vector-populations and increasing mobility of dog owners may be responsible for an emergence situation of infection risk for Babesia spp. by time. E.g., Dermacentor reticulatus has become autochtonously prevalent already till Lausanne in the Lake Geneva region, and further surveillance is suggested to tackle this problem.

Intrasexual competition among females and the stabilization of a conspicuous colour polymorphism in a Lake Victoria cichlid fish

The maintenance of colour polymorphisms within populations has been a long-standing interest in evolutionary ecology. African cichlid fish contain some of the most striking known cases of this phenomenon. Intrasexual selection can be negative frequency dependent when males bias aggression towards phenotypically similar rivals, stabilizing male colour polymorphisms. We propose that where females are territorial and competitive, aggression biases in females may also promote coexistence of female morphs. We studied a polymorphic population of the cichlid fish Neochromis omnicaeruleus from Lake Victoria, in which three distinct female colour morphs coexist: one plain brown and two blotched morphs. Using simulated intruder choice tests in the laboratory, we show that wild-caught females of each morph bias aggression towards females of their own morph, suggesting that females of all three morphs may have an advantage when their morph is locally the least abundant. This mechanism may contribute to the establishment and stabilization of colour polymorphisms. Next, by crossing the morphs, we generated sisters belonging to different colour morphs. We find no sign of aggression bias in these sisters, making pleiotropy unlikely to explain the association between colour and aggression bias in wild fish, which is maintained in the face of gene flow. We conclude that female-female aggression may be one important force for stabilizing colour polymorphism in cichlid fish.