How Long To Transmit?

Michael Cook reports-  "The claims that removal of ticks within 24 hours or 48 hours of attachment will effectively prevent LB are not supported by the published data, and the minimum tick attachment time for transmission of LB in humans has never been established."

Literature published by the Infectious Diseases Society of America (IDSA) and CDC continues to claim it takes over 24/48 hours (or more) for a tick to transmit the spirochetes that cause Lyme disease to human hosts.  This theory, along with much of their Lyme related literature, has been proven to be inaccurate.

A newly released study by Michael Cook, Lyme borreliosis: a review of data on transmission time after tick attachment, who reviewed scientific literature published over the past century, indicates a tick can be attached for much less than 24/48 hours and still transmit Lyme disease, something many people bitten by ticks already, unfortunately, learned from experience.  Cook's report supports what countless patients have experienced.  

Below are quotes from Cook's very interesting article; however, it is well worth reading his entire article that is linked below.

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"Studies have found systemic infection and the presence of spirochetes in the tick salivary glands prior to feeding, which could result in cases of rapid transmission.  Also, there is evidence that spirochete transmission times and virulence depend upon the tick and Borrelia species. These factors support anecdotal evidence that Borrelia infection can occur in humans within a short time after tick attachment."

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"Tick blood feeding behavior includes engagement, the adherence to the host; exploration, the search for a suitable site for attachment; and penetration, where the tick inserts the mouthparts in preparation for feeding.60 

During the process of exploration when the tick is searching for a suitable site, temperature increase will activate OspA/OspC regulation and begin the process of increased motility and infectivity [of the spirochetes]. 

Exploration time will be highly variable and depend on how quickly the tick migrates to an optimal site. This time could vary with host animal size, the presence of competing ticks, or rejection of a site as unsuitable. 

Unattached and un-engorged ticks are routinely observed by deer hunters and pet owners. Hence, exploration time must be included with attachment time to more accurately reflect “time for transmission”.

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"Although LB receives considerable attention and is the focus of this study, ticks transmit many diseases with 12 viral infections discussed by Lani et al including tick-borne encephalitis, Louping-ill, Colorado tick fever, and Alkhurma hemorrhagic fever, which has a mortality rate of 25%.11 

Hard-bodied ticks of the genus Ixodes also carry bacterial and parasitic diseases including: anaplasmosis, babesiosis, ehrlichiosis, rickettsiosis, and bartonellosis. Zhang et al investigated the microbiome of Ixodes persulcatus using rRNA sequencing and found 237 bacteria genera suspected of being pathogens to vertebrates.12

Many studies have found ticks infected with two or more of these pathogens and this increase in pathogen burden can result in more serious symptoms and post-treatment sequelae.1316 

An important emerging pathogen is Candidatus neoehrlichia mikurensis,17and in a survey of Canadian residents, 62% of respondents reported at least one coinfection and 15% reported three coinfections with Bartonella and Babesia the most common.18 

The attachment time for transmission of almost all of these pathogens is unknown; however, there are studies that indicate rapid transmission of some. Ebel and Kramer demonstrated Powassan virus infection with 15 minutes of tick attachment19 and although Saraiva et al found that transmission of Rickettsia rickettsii by unfed Amblyomma aureolatum ticks required >10 hours attachment time, they found that transmission could occur in as little as 10 minutes with fed ticks.20"

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"After transferring to the host, the tick searches for a suitable attachment site. With natural hosts, this is typically in the head area giving access to the ears and neck region or groin area.27 

Tick attachment starts by inserting the saw-like chelicerae into the epidermis to create an entrance wound. 

Then using the leverage from the chelicerae the barbed hypostome mouthpart is pulled in. This process is continued in a ratchet-like fashion until the tick is fully attached, with the process complete within 10 minutes. 

This is described by Richter et al,28 and demonstrated in a video.29 The multiple barbs of the hypostome lock the tick into the epidermis and help prevent host activities, for example, grooming, from detaching the tick, and in some species, a cement plug is created to further ensure firm attachment."

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"During attachment, ticks inject a complex mixture of bioactive chemicals into the host including histamine binders and cytokine inhibitors to mediate host response, complement inhibitors to suppress the host immune response, and anticoagulants to facilitate the blood meal. 30,31 

"This results in a painless “bite” and usually prevents an inflammatory response. 

[MY NOTE-  An inflammatory response at the tick bite site (not an EM rash) could possibly indicate the inhibitors used to suppress the host immune response were not fully functioning, or in varying species of ticks are more/less viable than others?] 

Injection of saliva occurs over a major part of the attachment time with the blood meal occurring late in the process.32 Approximately 75% of the water taken up during feeding is returned to the host.33 "

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"The potential for pathogen transmission by regurgitation was considered; however visual and microscopic observation of post feeding saliva found no evidence of this. 34"

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"This indicates that the probability of transmission within 24 hours could be as high as 20.37%. 

Similarly, the probability of infection within 48 hours has a confidence interval of ±24.63% with a probability of transmission up to 57.63%. "

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"Shih and Spielman, also using animal models reported in 1993 that infection occurred mainly after 2 days of feeding; however, they indicated that in one experiment, 100% of the mice became infected within 48 hours.

 It was also found that partially fed ticks would efficiently re-attach to a new host, and in these new hosts transmission occurred in 83% of cases within 24 hours. 36" 

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"Histological studies reported by Gern et al in 1990 found that when I. ricinus ticks acquired infection during feeding, the spirochetes multiplied in the midgut, but they noted that some spirochetes penetrated the gut wall of the ticks and caused systemic infection. 41"

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"A study by Piesman et al found infected ticks with bacteria in their salivary glands and other organs at the onset of feeding, and even before feeding began. 26 

Lebet and Gern demonstrated that 11% of field-collected unfed nymphal ticks had systemic infection,42 and Leuba-Garcia et al found that 36% of unfed adult I. ricinus ticks collected in two districts of Switzerland had systemic infection, and they commented that this could impact transmission time in humans.43 

These results suggest that in cases where the spirochetes are present in the tick salivary glands, they can be injected into the host during the preparatory transfers of antihistamines and anticoagulants prior to the commencement of feeding, ie, immediately after attachment of the tick to the host."

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"An extensive study using a total of 1962 I. persulcatus ticks infected with B. garinii and B. afzelii found that Borrelia were frequently found in the salivary glands of unfed ticks and that during the early stage of feeding, the proportion of ticks with spirochetes in the salivary glands did not increase, nor the concentration of spirochetes. The authors concluded that Borrelia migration from the tick gut to the salivary glands during feeding is not necessary for pathogen transmission. 45"

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"As a tick takes a blood meal, the body becomes engorged and the change in body length has been suggested as a method to estimate the time of attachment. Falco et al studied this in 1996 and used the scutal index, which is the ratio of the length of the hard body plate to the tick body length.24 

Their published graphical data indicate that the method cannot discriminate between attachment times <24 hours, it is poor up to 36 hours, and there is large variability thereafter. This is explained by the blood meal and engorgement taking place during the later stage of attachment. 

Meiners et al62 found that the scutal index estimate for attachment time had poor correlation with the attachment time estimated by the patients. ... This poor correlation indicates that neither the scutal index nor the coxal index is useful as a risk indicator."
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"A European study documented six cases of culture-confirmed infection where tick attachment was <6 hours and nine cases where transmission occurred in <24 hours.64 Angelov reported a case based on clinical symptoms and positive serology, where infection was transmitted in <24 hours and a second case where a patient’s conjunctiva was infected by the intestinal contents of a tick. 65"

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"The claims that removal of ticks within 24 hours or 48 hours of attachment will effectively prevent LB are not supported by the published data, and the minimum tick attachment time for transmission of LB in humans has never been established."

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"Therefore, LB infection can never be excluded after a tick bite irrespective of the estimated duration of attachment time."


Int J Gen Med. 2015; 8: 1–8. 
Published online 2014 Dec 19. doi:  10.2147/IJGM.S73791
PMCID: PMC4278789

Lyme borreliosis: a review of data on transmission time after tick attachment