Differential Survival of Lyme Borreliosis Spirochetes in Ticks That Feed on Birds

Abstract

The abilities of the most common European genospecies of Borrelia burgdorferi sensu lato to survive blood meals taken by ticks feeding on birds were analyzed. A pattern of differential survival of the spirochetes in feeding ticks was observed. The result is consistent with the concept of selective transmission of Lyme borreliosis spirochetes.The genospecies of Borrelia burgdorferi sensu lato and, at times, their variants are maintained in nature by different sets of hosts (1, 3, 6-10, 15, 18, 20, 21, 23; K. Hanincová, S. M. Schäfer, S. Etti, H.-S. Sewell, V. Taragelová, D. Ziak, M. Labuda, and K. Kurtenbach, submitted for publication). At present, the key determinant of this host association is considered to be the interaction of B. burgdorferi sensu lato with the alternative pathway of the host's complement system (14,16,19,22,25). A recently proposed model of transmission predicts the selection of spirochetes by complement in the gut of feeding ticks (17,18). In the present study, an avian model was used to test this prediction.Two-week-old pheasants (Phasianus colchicus) were obtained from a breeder in Oxfordshire, United Kingdom. Ixodes ricinus larvae and nymphs were derived from a tick colony maintained at the NERC Centre for Ecology and Hydrology, Oxford, United Kingdom. Low-passage cultures of B. burgdorferi sensu stricto (ZS 7), Borrelia afzelii (ACA 1), Borrelia garinii (an isolate from Freiburg, Germany, with an ospA allele identical to that of the Rio2 strain [2]), and Borrelia valaisiana (strain UK) were expanded to a concentration of 10 7 cells per ml of culture medium. The cultures were used to infect questing nymphs with spirochetes by glass capillary feeding. Of those ticks which took up more than 100 spirochetes, as calculated by the volume of culture imbibed, 20 were introduced to each bird by being confined within a neoprene cell glued with latex to the shaved throat of each bird (Fig.1). Four groups composed of four birds each were challenged with ticks infected with one of the genospecies of B. burgdorferi sensu lato. Engorged nymphs were recovered, kept for 2 weeks, and then preserved in 70% ethanol.For comparison, an additional four groups of 10 nymphs each (all of whom were preinfected with one of the four genospecies) were not allowed to feed on hosts but were starved for several weeks and then preserved in ethanol. Four weeks after the challenge with infected nymphs, the pheasants were tested by xenodiagnosis for Borrelia through the introduction of Ͼ50 noninfected I. ricinus larvae per animal. These larvae were also contained in neoprene cells and glued to the back of the neck of each pheasant. Engorged larvae were allowed to molt to nymphs. After xenodiagnosis, two skin biopsy samples were taken from each bird, one from the feeding site of ticks and one from the eyelid. The 5S-23S intergenic spacer and the ospA locus of B. burgdorferi sensu lato were amplified by nested PCR from DNA extracted from Borrelia cultures, ticks, and biopsy samples (5, 15), and the PCR products were sequence...

Identification of a New Borrelia Species among Small Mammals in Areas of Northern Spain Where Lyme Disease Is Endemic

“…B. afzelii seems to be maintained in nature mainly by a tick-small mammal cycle that does not include the involvement of birds (36,40,66). The fact that small mammals are not playing a relevant role as reservoir hosts for B. burgdorferi sensu lato in the study areas may explain the low prevalence of B. afzelii found, similar to that in Ireland (32), where B. valaisiana was highly prevalent and birds seemed to play a relevant role as reservoir hosts for this genospecies (39,50). B. valaisiana was also prevalent in our region, suggesting that birds may also play a role in maintaining this genospecies in our area.…”

Tick-Borne Pathogens in Ticks Feeding on Migratory Passerines in Western Part of Estonia

“…It has been previously shown that birds do not serve as adequate reservoirs for B. afzelii, and furthermore, that the uptake of avian blood initiates the elimination of B. afzelii in the tick (Kurtenbach et al 2002). Because the B. afzelii DNA, detected in the current study, was recovered from nymphs feeding on great tits, we suggest that B. afzelii infection in these ticks was acquired at the larval stage from a rodent host.…”

Adaptation of Diverse Lyme Disease Spirochetes in a Natural Rodent Reservoir Host

“…Although B. burgdorferi sensu stricto is much less prevalent in Central Europe than is B. afzelii, these spirochetes have been isolated from a broad array of hosts, including various rodents and birds as well as their (3,5,8,15). Numerous ticks acquire spirochetes from pheasants experimentally infected by B. garinii, but only few ticks do so from B. burgdorferi sensu strictoinfected pheasants (9). Whereas B. afzelii appears to be well adapted to rodents and B. garinii seems to be adapted to birds, B. burgdorferi sensu stricto is less likely to perpetuate in either of these hosts.…”