Genomic epidemiology of Campylobacter fetus subsp. venerealis from Germany

Abstract

Campylobacter fetus subsp. venerealis (Cfv) causes bovine genital campylobacteriosis (BGC), a World Organization for Animal Health (WOAH)-listed trade-relevant disease characterized by severe reproductive losses, such as infertility, early embryonic death and abortion in cattle. BGC has significant economic implications that have prompted several countries to adopt stringent eradication and surveillance measures to contain the disease. In Germany, there has been a low incidence of BGC cases over the past 28 years. This study aimed to illustrate the genomic diversity of German Cfv strains isolated from different federal states in Germany. This study analyzed 63 Cfv strains, collected between 1985 and 2015, by whole-genome sequencing and compared them with genome data of 91 international Cfv isolates. The phylogenetic analysis showed that the Cfv population is genetically conserved and has geographic clusters. In Germany, one phylogenetic lineage comprising all strains was identified. This German lineage was part of a subclade that probably emerged in the nineteenth century and diversified over time. The results of this study point to a non-recurrent cross-border introduction of Cfv in Germany. The BGC control interventions in Germany can be considered successful as no outbreaks were reported since 2015.

The History of Bovine Genital Campylobacteriosis in the Face of Political Turmoil and Structural Change in Cattle Farming in Germany

“…Thus, a low incidence of BGC outbreaks ( n = 68 since 1994) in nine of sixteen federal states has been guaranteed. Outbreaks are caused by an endemic, genetically conserved German Cfv lineage with two major lineages (German Lineage 1 [northern states] and German Lineage 2 [southern states]) [ 6 ]. This distribution is in line with the distribution of German cattle breeds, i.e., specialized dairy cattle (German Black Pied cattle, lowland cattle) in northern Germany and mixed-purpose cattle (Höhenvieh, highland cattle) in southern Germany [ 22 ].…”

“…This distribution is in line with the distribution of German cattle breeds, i.e., specialized dairy cattle (German Black Pied cattle, lowland cattle) in northern Germany and mixed-purpose cattle (Höhenvieh, highland cattle) in southern Germany [ 22 ]. It has to be noted that Cfv strains originating from the former GDR and FRG both belong to the German lineage, pointing to a common ancestor before 1945, and before the ‘iron curtain’ (the physical barrier between both German states made with minefields, fences, guards and concrete) was built in 1961 and trade therefore stopped [ 6 ]. It is noteworthy that no introduction of Cfv strains from endemic countries has been documented by genetic investigation until now, which shows the effectiveness of the regulations in force.…”

“…The question of interest for risk analysis is whether Cfv could have also survived in such a controlled and nearly closed system of trade and production. Indeed, some strains of Cfv isolated from 1985 to 1988 in the GDR were sent to the new German reference laboratory after re-unification from Thuringian laboratories and showed a unique genetic pattern which was not found in the re-unified FRG again [ 6 , 45 ]. This GDR specific pattern may have been eradicated with the very fast changeover from the sbmr to imported HF.…”

“…This GDR specific pattern may have been eradicated with the very fast changeover from the sbmr to imported HF. From 1993 onwards, the western FRG Cfv patterns were also found in the eastern FRG [ 6 ]. As the GDR strains were of German lineage, an introduction from import countries seems unlikely and BCG had obviously survived in the GDR.…”

“…The Cfv population was shown to be genetically conserved but has evolved in geographic clusters [ 5 ]. Cfv strains from Germany collected between 1985 and 2015 were recently assigned to a single cluster that may have emerged around 1840 [ 6 ]. This unexpected timing of the emergence of the German Cfv cluster at a time of profound changes in European history prompted us to investigate the fate of BCG in Germany reflecting the interactions of the rapid change in political systems, the development of modern infectiology, the structural change in agriculture and cattle breeding and customer demands and recent attitudes towards animal welfare.…”