I would not be so sure.
Infectious agents found in or transmitted through tick saliva:
Detected somewhere in a tick is not equivalent to demonstrated in tick saliva. Yet it seems that for most biologically transmitted tick-borne pathogens, the salivary glands and saliva are central to transmission.
Below are agents for which there is evidence of salivary gland involvement, saliva-assisted transmission (SAT), or transmission during tick feeding. But as always, my bias is not on the side of hopeful wishing, betting on sloth, or the creed that “all is jolly and safe if under 24-48 hours of tick attachment.”
Borrelia
1. Borrelia burgdorferi sensu lato (Lyme borreliosis)
During feeding, Lyme borreliae migrate from the tick midgut, disseminate through the hemocoel, enter the salivary glands, and are transmitted to the vertebrate through saliva. Tick saliva also alters the local immune environment and can enhance Borrelia establishment and dissemination.
Full references
Horká H, Černá-Kýčková K, Skallová A, Kopecký J. Tick saliva affects both proliferation and distribution of Borrelia burgdorferi spirochetes in mouse organs and increases transmission of spirochetes to ticks. International Journal of Medical Microbiology. 2009;299(5):373-380. doi:10.1016/j.ijmm.2008.10.009.
Šimo L, Kazimírová M, Richardson J, Bonnet SI. The essential role of tick salivary glands and saliva in tick feeding and pathogen transmission. Frontiers in Cellular and Infection Microbiology. 2017;7:281. doi:10.3389/fcimb.2017.00281.
2. Borrelia afzelii
B. afzelii is a major European Lyme borreliosis agent transmitted primarily by Ixodes ricinus. As with other Lyme-group borreliae, transmission involves migration to and passage through the salivary glands during feeding.
Full reference
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281. doi:10.3389/fcimb.2017.00281.
3. Borrelia garinii
Another important Lyme borreliosis organism transmitted by Ixodes ticks, particularly in Europe and Asia. The salivary environment facilitates transmission and establishment of Lyme-group borreliae.
Full reference
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281. doi:10.3389/fcimb.2017.00281.
4. Borrelia bavariensis
B. bavariensis is another member of the B. burgdorferi sensu lato complex transmitted by Ixodes ticks and associated particularly with neurologic Lyme disease in Eurasia.
Full reference
Nuttall PA. Tick saliva and its role in pathogen transmission. Wiener Klinische Wochenschrift. 2019;131:233-243.
5. Borrelia spielmanii
A recognized European Lyme borreliosis species transmitted by Ixodes ricinus.
Full reference
Nuttall PA. Tick saliva and its role in pathogen transmission. Wiener Klinische Wochenschrift. 2019;131:233-243.
6. Borrelia miyamotoi (Hard-tick relapsing fever)
B. miyamotoi is biologically different from Lyme-group borreliae. It can occupy tick salivary glands before feeding, which helps explain why experimental transmission kinetics may differ from those of B. burgdorferi.
Full reference
Nuttall PA. Tick saliva and its role in pathogen transmission. Wiener Klinische Wochenschrift. 2019;131:233-243.
Anaplasma
7. Anaplasma phagocytophilum
This intracellular bacterium causes human granulocytic anaplasmosis. Ixodes ticks acquire the organism during feeding; the pathogen subsequently colonizes tick tissues, including the salivary glands, from which it is transmitted during subsequent feeding.
CDC identifies Ixodes scapularis and Ixodes pacificus as the principal U.S. vectors.
Full reference
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281. doi:10.3389/fcimb.2017.00281.
8. Anaplasma marginale
An important veterinary pathogen of cattle. Colonization of tick salivary glands is a critical component of biological transmission.
Full reference
Kocan KM, de la Fuente J, Blouin EF, Garcia-Garcia JC. Anaplasma marginale (Rickettsiales: Anaplasmataceae): recent advances in defining host-pathogen adaptations of a tick-borne rickettsia. Parasitology. 2004;129(S1):S285-S300.
Ehrlichia
9. Ehrlichia chaffeensis
The cause of human monocytic ehrlichiosis, transmitted predominantly by Amblyomma americanum in the United States. Transmission occurs during infected tick feeding.
Full reference
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281.
10. Ehrlichia ewingii
Another Amblyomma americanum-transmitted human ehrlichiosis agent.
Full reference
Ismail N, McBride JW. Tick-borne emerging infections: Ehrlichiosis and anaplasmosis. Clinics in Laboratory Medicine. 2017;37(2):317-340.
11. Ehrlichia canis
Important particularly in canine monocytic ehrlichiosis and transmitted primarily by Rhipicephalus sanguineus sensu lato.
Full reference
Ismail N, McBride JW. Tick-borne emerging infections: Ehrlichiosis and anaplasmosis. Clinics in Laboratory Medicine. 2017;37(2):317-340.
Rickettsia
12. Rickettsia rickettsii
The agent of Rocky Mountain spotted fever infects tick tissues, including the salivary glands, and is inoculated during feeding.
Full reference
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281.
13. Rickettsia conorii
The cause of Mediterranean spotted fever provides particularly good evidence for saliva-assisted transmission. Tick saliva can enhance infection of vertebrate hosts.
Full references
Milhano N, de Carvalho IL, Alves AS, et al. Coinoculation of Rickettsia conorii and tick salivary gland extract exacerbates the course of infection in a murine model. Vector-Borne and Zoonotic Diseases. 2015.
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281.
14. Rickettsia parkeri
R. parkeri is a spotted fever group rickettsia transmitted principally by Amblyomma ticks.
Full reference
Paddock CD, Goddard J. The evolving medical and veterinary importance of the Gulf Coast tick (Acari: Ixodidae). Journal of Medical Entomology. 2015;52(2):230-252.
15. Rickettsia africae
Cause of African tick-bite fever and transmitted principally by Amblyomma species.
Full reference
Parola P, Paddock CD, Socolovschi C, et al. Update on tick-borne rickettsioses around the world: a geographic approach. Clinical Microbiology Reviews. 2013;26(4):657-702.
Francisella
16. Francisella tularensis
The tularemia organism is particularly important because experimental evidence demonstrates that tick saliva enhances F. tularensis infection.
Full references
Krocová Z, Macela A, Hernychová L, Kroča M, Pechová J, Kopecký J. Tick salivary gland extract accelerates proliferation of Francisella tularensis in the host. Journal of Parasitology. 2003.
Šimo L, Kazimírová M, Richardson J, Bonnet SI. Frontiers in Cellular and Infection Microbiology. 2017;7:281.
Babesia
17. Babesia microti
The major cause of human babesiosis in the northeastern and upper midwestern United States is transmitted by Ixodes scapularis. CDC notes that the same tick can transmit B. burgdorferi, A. phagocytophilum, and B. microti.
Babesia biology is especially relevant to the saliva question: infective sporozoites develop in the tick salivary glands and are inoculated during feeding.
Full reference
Homer MJ, Aguilar-Delfin I, Telford SR III, Krause PJ, Persing DH. Babesiosis. Clinical Microbiology Reviews. 2000;13(3):451-469.
18. Babesia divergens
A major cause of severe human babesiosis in Europe. Infective sporozoites develop within tick salivary glands before inoculation into the vertebrate.
Full reference
Hildebrandt A, Gray JS, Hunfeld KP. Human babesiosis in Europe: what clinicians need to know. Infection. 2013;41:1057-1072.
19. Babesia venatorum
An emerging zoonotic Babesia transmitted by Ixodes ticks in Europe and Asia.
Full reference
Hildebrandt A, Gray JS, Hunfeld KP. Infection. 2013;41:1057-1072.
20. Babesia duncani
A human babesiosis agent recognized in North America. Tick-vector biology is less firmly established than for B. microti, so it should not be given the same salivary-transmission evidence grade.
Full reference
Vannier E, Krause PJ. Human babesiosis. New England Journal of Medicine. 2012;366(25):2397-2407.
Theileria
21. Theileria parva
The agent of East Coast fever in cattle undergoes essential development within tick salivary glands. Mature sporozoites are released in saliva during feeding.
Full reference
Shaw MK. Cell invasion by Theileria sporozoites. Trends in Parasitology. 2003;19(1):2-6.
22. Theileria annulata
Likewise develops infectious sporozoites within tick salivary glands before inoculation into mammalian hosts.
Full reference
Schnittger L, Rodriguez AE, Florin-Christensen M, Morrison DA. Babesia: a world emerging. Infection, Genetics and Evolution. 2012;12(8):1788-1809.
Tick-Borne Viruses
Viruses provide some of the clearest examples of pathogens delivered in tick saliva because many replicate within salivary glands and can be transmitted rapidly during feeding. Tick saliva can also markedly enhance viral infectivity.
23. Tick-borne encephalitis virus (TBEV)
TBEV replicates within tick salivary glands and is transmitted through saliva. It is also a classic example of saliva-assisted and non-viremic transmission between co-feeding ticks.
Full reference
Labuda M, Nuttall PA, Kožuch O, et al. Non-viraemic transmission of tick-borne encephalitis virus: a mechanism for arbovirus survival in nature. Experientia. 1993;49:802-805.
24. Powassan virus
Powassan virus is particularly important in North America because transmission from tick to mammalian host can occur much more rapidly than is typical for Lyme borreliae.
Tick saliva also enhances Powassan virus infection.
Full reference
Hermance ME, Thangamani S. Tick saliva enhances Powassan virus transmission to the host, influencing its dissemination and the course of disease. Journal of Virology. 2015;89:7852-7860.
25. Thogoto virus
THOV was historically crucial because experiments with this virus led to development of the concept of saliva-assisted transmission.
Full reference
Jones LD, Hodgson E, Nuttall PA. Enhancement of virus transmission by tick salivary glands. Journal of General Virology. 1989.
26. Crimean-Congo hemorrhagic fever virus
CCHFV is transmitted principally by Hyalomma ticks. Infection of tick salivary tissues and inoculation during feeding are central to vector transmission.
Full reference
Bente DA, Forrester NL, Watts DM, McAuley AJ, Whitehouse CA, Bray M. Crimean-Congo hemorrhagic fever: history, epidemiology, pathogenesis, clinical syndrome and genetic diversity. Antiviral Research. 2013;100(1):159-189.
27. Severe fever with thrombocytopenia syndrome virus
SFTSV is a tick-borne phlebovirus transmitted principally by Haemaphysalis longicornis. Salivary gland infection and saliva-mediated transmission form part of its vector cycle.
Full reference
Yu XJ, Liang MF, Zhang SY, et al. Fever with thrombocytopenia associated with a novel bunyavirus in China. New England Journal of Medicine. 2011;364:1523-1532.
28. Heartland virus
Heartland virus is another tick-borne phlebovirus associated principally with Amblyomma americanum.
Full reference
Savage HM, Godsey MS Jr, Lambert A, et al. First detection of Heartland virus (Bunyaviridae: Phlebovirus) from field-collected arthropods. American Journal of Tropical Medicine and Hygiene. 2013;89(3):445-452.
29. Bourbon virus
Bourbon virus is a tick-associated thogotovirus associated particularly with the lone star tick.
Full reference
Kosoy OI, Lambert AJ, Hawkinson DJ, Pastula DM, Goldsmith CS, Hunt DC, Staples JE. Novel thogotovirus associated with febrile illness and death, United States, 2014. Emerging Infectious Diseases. 2015;21(5):760-764.
30. Colorado tick fever virus
A coltivirus transmitted predominantly by Dermacentor andersoni.
Full reference
Goodpasture HC, Poland JD, Francy DB, Bowen GS, Horn KA.