Transmission rate of Bb from bites of infected ticks:

Previous studies have shown that even in case the tick was infected with Borrelia burgdorferi the rate of transmission was usually low (<= 5%), but this work implicate that the rate of transmission from infected ticks may be much higher?

Transmission risk of Borrelia burgdorferi sensu lato from Ixodes ricinus ticks to humans in southwest Germany.
Maiwald M, Oehme R, March O, Petney TN, Kimmig P, Naser K, Zappe HA, Hassler D, von Knebel Doeberitz M. 
Epidemiol Infect 1998 Aug;121(1):103-8 PMID: 9747761
The risk of Borrelia burgdorferi infection and the value of antibiotic prophylaxis after tick bite are controversial. In this study, performed in two areas of southwestern Germany, ticks were collected from 730 patients and examined by the polymerase chain reaction (PCR) for B. burgdorferi. To assess whether transmission of B. burgdorferi occurred, the patients were clinically and serologically examined after tick removal and during follow-up examinations. Data from all tick bites gave a total transmission rate of 2.6% (19 patients). Eighty-four ticks (11.3%) were PCR positive. Transmission occurred to 16 (26.7%) of 60 patients who were initially seronegative and could be followed up after the bite of an infected tick. These results indicate that the transmission rate from infected ticks in Europe is higher than previously assumed. Examination of ticks and antibiotic prophylaxis in the case of positivity appears to be indicated. 

Transmission of Bb after short duration tickbite (<24h):

(unpublished case story reported by Marie Kroun at a staffmeeting in Kolding, Denmark, March 1996)
I had a pediatric case, a girl who had done tick check about 4 hours after a walk in the forest. A tick was found behind the ear and removed properly (in the ER). She developed a typical EM-rash at the site of the bite and became seropositive for Bb on ELISA and later she developed neurological problems (nystagmus, convulsions), but spinal fluid was normal (not positive spinal-index on two occasions) and she had no relief from 14 days IV antibiotics, so it was not proven that her neurologic problems were due to borreliosis, but it raised the concern that it might be related. We can't do culture or PCR for borrelia her in Denmark, except for scientific purposes. The only test available is the ELISA for anti-flagellin!

Disseminated Lyme disease after short-duration tick bite
Patmas MA, Remorca C.
Journal of Spirochetal and Tickborne Diseases 1994; 1:77-78 [Not listed on PubMed, have scanned to PDF]
Lyme disease, an Ixodes tick-borne spirochetal infection, has been the subject of much controversy. One problematic area has been the prophylactic treatment of deer-tick bites in endemic areas. Some have argued against routine antimicrobial prophylaxis based upon the belief that transmission of Borrelia burgdorferi is unlikely before 24-48 hours of tick attachment. Others have suggested that it is cost effective to administer prophylactic antibiotics against Lyme disease when embedded deer-tick bites occur in endemic areas. Herein, a case of disseminated Lyme disease after only 6 hours of tick attachment is presented. The current recommendation against treatment of short-duration tick bites may need reconsideration, particularly in hyperendemic areas. Color pictures.

Unusual features in the epidemiology of Lyme borreliosis.
Angelov L.
Eur J Epidemiol 1996 Feb; 12(1): 9-11 PMID: 8817171
In this study two cases of Lyme borreliosis are presented. First, the author describes how he contracted Lyme borreliosis 24 hours after he visited an endemic area. The second case described is that of a woman who developed Lyme borreliosis symptoms, when intestinal content of an infected tick came into contact with her conjunctiva. In both cases the diagnosis is based on clinical picture and positive serological tests. The first case shows the probability of contracting Lyme borreliosis when the duration of the tick's attachment to the skin is less than 24 hours. The second case, described demonstrates transmission of B. burgdorferi by contact.     

Risk of infection with Borrelia burgdorferi sensu lato for a host in relation to the duration of nymphal Ixodes ricinus feeding and the method of tick removal.
Kahl O, Janetzki Mittmann C, Gray JS, Jonas R, Stein J, de Boer R.
Zentralbl Bakteriol 1998 Jan; 287(1-2): 41-52 PMID: 9532263
The objectives of the present study were to investigate the risk of B. burgdorferi s.1. (Bb)-transmission by I. ricinus-nymphs to a host (i) after different periods of feeding, and (ii) with regard to the particular method of tick removal. On each of 72 Mongolian gerbils 3 tick nymphs taken from a highly infected batch were allowed to feed in a small capsule. Feeding ticks were removed 16.7, 28.9, 47.0, and 65.2 hrs post-attachment. In each of these 4 groups 3 sub-groups with 6 gerbils each were deticked by (a) pulling ticks out with forceps without any pretreatment, (b) pulling ticks out after 3 min of intensive squeezing, and (c) applying nail polish to ticks 1.1 hrs before removal. The infection status in each gerbil was subsequently determined by larval xenodiagnosis. All gerbils with ticks removed > or = 47 hrs post-attachment were found to be infected. After 16.7 hrs as well as after 28.9 hrs of tick feeding, approximately 50% of the gerbils had acquired a transmissible infection, thus Bb-transmission to a host may even occur in the early phases of I. ricinus feeding. There is no evidence from this study that the tick removal method used has any significant influence on a host's Bb-infection risk.

Preliminary studies on virus and spirochete accumulation in the cement plug of ixodid ticks.
Alekseev AN, Burenkova LA, Vasilieva IS, Dubinina HV, Chunikhin SP.
Exp Appl Acarol 1996 Dec; 20(12): 713-23 PMID: 9004495
We provide evidence that tick-borne encephalitis virus and Borrelia burgdorferi s.l. are accumulated in the cement plug in the host skin within the first few hours after tick attachment. Extirpation of the tick without the cement plug, even very soon after the attachment, did not prevent the transmission by Ixodes ricinus, Ixodes persulcatus or Dermacentor reticulatus to mice. This was within 1 hour in the case of the TBE virus and after 20-22 h of attachment, in the case of Borrelia and I. persulcatus. The epidemiological significance of these findings is discussed.  

Borrelia burgdorferi sensu lato in female cement plug of Ixodes persulcatus ticks (Acari, Ixodidae).
Alekseev AN, Arumova EA, Vasilieva IS.
Exp Appl Acarol 1995 Sep; 19(9): 519-22 PMID: 8575271
Borrelia burgdorferi sensu lato was detected in one out of five cement plugs of female Ixodes persulcatus ticks. The spirochetes were found by dark field microscopy as early as 18 h after attachment of the ticks to the skin of a white mouse. The relevance of this finding is discussed in relation to the epidemiology of Lyme borreliosis.   

Accelerated transmission of Lyme disease spirochetes by partially fed vector ticks.
Shih CM, Spielman A.
J Clin Microbiol 1993 Nov; 31(11): 2878-81 PMID: 8263171 PDF
To determine how rapidly Lyme disease spirochetes (Borrelia burgdorferi) can be transmitted by partially fed vector ticks (Ixodes dammini), attached nymphs were removed from their hosts at various intervals post-attachment and subsequently permitted to re-feed to repletion on noninfected mice. We confirm previous reports that ticks deposit Lyme disease spirochetes in the skin of their hosts mainly after 2 days of attachment. Those that have been removed from a host within this interval can reattach and commence feeding. Spirochete-infected nymphs that have previously been attached to a host for 1 day become infectious to other hosts within another day. Noninfected nymphs acquire infection from spirochete-infected hosts within a day of attachment and become infectious to other hosts 3 to 5 days later. Virtually all ticks transmitted infection when reattaching after first feeding for 2 days. We conclude that partially fed nymphal ticks transmit spirochetal infection more rapidly than do ticks that have never been attached to a host and that infected ticks become infectious before they molt. 

Characterization of Borrelia burgdorferi isolated from different organs of Ixodes ricinus ticks collected in nature.
Leuba Garcia S, Kramer MD, Wallich R, Gern L.
Int J Med Microbiol Virol Parasitol Infect Dis 1994 Mar; 280(4): 468-75 PMID: 8061407
Borrelia burgdorferi was isolated from 22 out of 133 adult Ixodes ricinus ticks collected from vegetation at two sites in Switzerland. From 17 ticks, spirochetes could be isolated from more than one organ. When the different isolates obtained from one tick were compared by SDS-PAGE analysis, differences in the protein profiles were observed in 8 cases. The isolates were further compared by immunological methods using mono- and polyclonal antibodies. Differences were observed in the proteins of 31-35 kDa and 18-25 kDa. Genetic divergence among isolates was evaluated by use of a B. burgdorferi specific gene probe for ospA. Correlation could be observed between immunological differences in OspA defined by monoclonal antibody LA31 and genetic variation of ospA as judged by restriction fragment length polymorphism (RFLP). Our findings indicate that systemic infection in unfed I. ricinus adults, as reflected by isolation of B. burgdorferi from multiple organs of one tick, is more frequent (8/22, 36%) than previously described (5%). Moreover, the presence of different B. burgdorferi phenotypes/genotypes in one tick is described for the first time. The findings may have bearings (i) on the time of tick attachment required for spirochete transmission since borreliae are already present in the salivary glands of systemically infected ticks at the beginning of the blood meal and (ii) perhaps also on the diversity of B. burgdorferi phenotypes inoculated by these ticks.v

[The presence of Borrelia in the intestines and salivary glands of spontaneously infected adult Ixodes persulcatus Schulze ticks during bloodsucking]
Moskvitina GG, Korenberg EI, Gorban' Lia.
Med Parazitol Mosk 1995 Jul-Sep(3): 16-20 PMID: 7476674
A direct microscopic analysis of fixed smears and live preparations was used to reveal whether spirochetes are present in the gut and salivary glands of adult Ixodes persulcatus ticks spontaneously infected with Borrelia garinii and B. afzelii. Unfed ticks collected from a vegetation, partially fed ticks removed from human bodies, and ticks deliberately fed on laboratory animals were studied. In each preparation, all spirochetes were counted in 250 microscopic fields, and their concentration per 100 microscopic fields was determined. A total of 1962 ticks were individually analysed. The methods used on the study allowed a reliable identification of Borrelia in the viscera of not only unfed, but also of partially fed ticks. The infection rate in ticks that started bloodsucking was slightly lower than in the unfed ticks. This was associated with the decreased spirochete concentration in the preparations made from the partially fed ticks. Borrelia were frequently found in the salivary glands of the unfed infected I. persulcatus. During the first two to three days of bloodsucking, neither the proportion of ticks with spirochetes in the salivary glands, nor the spirochete concentrations increase. Borrelia migration from the tick gut into the salivary glands during early bloodsucking is not a prerequisite for or even important for pathogen transmission with saliva. The transmission rate appears to depend on the baseline proportion of the unfed ticks carrying spirochetes in their salivary glands.(ABSTRACT TRUNCATED AT 250 WORDS)

[The frequency of generalized infection in adult fasting ticks of the genus Ixodes in foci of borreliosis in Russia and the USA]
Moskvitina GG, Korenberg EI, Spielman A, Shchegoleva TV.
Parazitologiia 1995 Sep-Oct; 29(5): 353-60 PMID: 8524615
A total of 740 adult Ixodes persulcatus ticks were collected from the vegetation by flagging in Russian foci where Borrelia afzelii and B. garinii circulate, and 156 I. dammini ticks were collected in northwestern USA regions in foci with B. burgdorferi s.str. circulation. Smears prepared from the internal organs of ticks were stained according to Romanovsky-Giemsa and analyzed under a microscope at a x 1125 magnification. All borreliae in 250 microscopic fields were counted, and concentration of microbial bodies per 100 microscopic fields was determined. The general level of infection by Borrelia in both vectors was similar: 26.2 x 3.2 in I. persulcatus and 26.3 +/- 7 in I. dammini. However, the proportions of ticks with generalized infections differ considerably (12.9 +/- 4.8 in I. persulcatus compared with 2.4 +/- 4.8 in I. dammini; significance of difference t = 3.1). We did not reveal any definite increase in the proportion of ticks with borreliae in the salivary glands among ticks with high concentrations of microbial bodies in the gut. In 25 I. persulcatus ticks with generalized infections, series of actual numbers of borreliae (per 100 microscopic fields) found in the gut and salivary glands did not correlate with one another (r = -0.23). These results confirm our previous conclusion (Korenberg, 1994) that frequencies of generalized infection in main vectors of different ixodid tick-borne borrelioses are also different, which is probably due to peculiarities of relationships between spirochetes of each species and corresponding tick vectors. These factors can be responsible for differences in the ways of horizontal and vertical transmission of pathogens belonging to the group under study. [the differences found here among different tick species may explain the different findings of transmission rate in US and in the 'old world' ... need to know more about Ixodes ricinus, the common vector in EU]