Studies on the transovarial transmission of Borrelia burgdorferi sensu lato in the taiga tick Ixodes persulcatus

Abstract

Abstract. The possibility of vertical transmission of Borrelia burgdorferi sensu lato in Ixodes persulcatus Schulze, 1930 ticks was studied in the progeny of 20 females collected from the vegetation in an active focus of ixodid tick-borne borrelioses (ITBB) located in the Perm oblast, Russia, where Borrelia garinii and B. afzelii are circulating. The presence of Borrelia DNA was detected by the PCR method after feeding and egg laying in 16 engorged females (80.0%), as well as in 36.5 ± 7.2% samples containing 20 eggs each and in 21.4 ± 4.2% samples containing 10 eggs each. The respective rates of individual egg infection were 0.4−8.0% and 0.5−23.0%. PCR analysis of 370 eggs (one egg per sample) and 781 unfed larvae hatched from the same egg masses (1, 10, 20, 40, and 50 larvae per sample) failed to reveal the presence of Borrelia DNA. Negative results were also obtained in experiments on inoculating the BSK II medium with the egg and larval materials. Microscopic analysis of 1,683 smear preparations of eggs and 1,416 preparations of unfed daughter larvae revealed spirochete-like cells in 7 (0.4 ± 0.3%) and 13 (0.9 ± 0.5%) preparations, respectively; typical Borrelia cells were found in seven preparations of larvae (0.5 ± 0.4%). Only 1 out of 16 infected females transmitted Borrelia vertically, through the eggs to the larval progeny. The infection rate in this progeny was about 7%, and the prevalence of Borrelia in individual larvae was 0.4−0.8 cells per 100 microscopic fields. These data do not allow the conclusion that transovarial transmission of B. burgdorferi sensu lato in the I. persulcatus tick is an established fact. However, they show that, even if such transmission is possible, its probability is very low.

Approaches for Reverse Line Blot-Based Detection of Microbial Pathogens in Ixodes ricinus Ticks Collected in Austria and Impact of the Chosen Method

“…In a previous study (7) on ticks collected from all regions of Austria in 2005, the overall prevalence was only 14.5%; however, nearly a third of those ticks were larvae. In the present study, larval ticks were excluded because transovarial transmission of B. burgdorferi sensu lato does not efficiently contribute to maintain these spirochetes in the natural cycle, and even if vertical transmission occurs, it is inefficient (37,38). By subtracting the number of larval ticks tested in the previous study by Blaschitz et al (7), the prevalence increases to 19.6% in their study and is closer to our result.…”

Species Co-Occurrence Patterns among Lyme Borreliosis Pathogens in the Tick Vector Ixodes ricinus

“…Cofeeding transmission refers to the process where hosts are not systemically infected but instead function as a temporary bridge (47) that facilitates transmission between infected and uninfected ticks feeding in close proximity to each other (48). Third, double infections may result from a combination of vertical (transovarial) and horizontal (blood meal) transmission of Borrelia genospecies, although the former is believed to be rare or nonexistent in Ixodes ticks (49)(50)(51). Fourth, larval ticks taking multiple blood meals from different hosts (interrupted blood meals) (44) could also produce double infections of rodentand bird-specific genospecies (43).…”

Coinfections Acquired from Ixodes Ticks

“…Larvae are generally not infected with B. burgdorferi, A. phagocytophilum, or B. microti upon hatching; transovarial passage of these pathogens from adult females to eggs has not been consistently demonstrated or is considered insignificant (91,136,148,154,171,228). However, transovarial transmission of B. divergens from adult I. ricinus ticks to larvae does occur (57,207) and is also believed to be important in maintaining the life cycle of other tick-borne viral and rickettsial pathogens (e.g., TBE virus, spotted fever group rickettsia) (32,162).…”