What affects the transmission of tick-borne pathogens?

Photo: RistoH/Adobe Stock

“How long does [a] tick have to feed to transmit an infection?” Susan E. Little, DVM, PhD, DACVM, Krull-Ewing professor of parasitology at the Center for Veterinary Health Sciences at Oklahoma State University in Stillwater, posed to her audience during a lecture at the 2025 American Veterinary Medical Association (AVMA) Convention in Washington, DC, this July.¹

“The true answer is, it depends,” Little answered.

The answer to how long a tick must feed to transmit a pathogen depends on several factors. These factors may include tick species, pathogen type, tick life stage, environmental conditions such as temperature and humidity, and the type of host.

As Little would go on to explain, no studies have investigated the minimum time it takes for North American ticks to transmit pathogens to dogs. To date, the available data is extrapolated from studies on mice, guinea pigs, or dogs in other parts of the world.¹ Moreover, many of these studies have been conducted using immature ticks, or nymphs, instead of adult ticks.

“Larvae feed in about 3 to 5 days...nymphs feed in about 5 to 7 days...adults feed for 7 to 14 days or longer. And so, their physiology is different. How quickly they get into that rapid feeding process that will lead to transmission varies for the different stages,” said Little.

Species that may primarily infect dogs during their adult stage, such as Rhipicephalus sanguineus (brown dog tick), Dermacentor variabilis (American dog tick), and Amblyomma americanum (lone star tick), can also influence the timing and efficiency of pathogen transmission.

When it comes to environmental factors, Little noted that most tick species in North America live in wildlife and nature and consequently spill over into dogs and people. The brown dog tick, however, is unique for living in homes and kennels, primarily infesting dogs.

Another factor that may contribute to differences in the transmission of pathogens is how the tick finds a host, according to Little. “We often think of ticks as passively questing. They crawl up vegetation, they wave that first pair of legs, they wait for something to walk by and rush against the vegetation, and then tick transfers over to the hair, coat, or the clothing of the host, right?” said Little. Although this is true for ticks in the Ixodes and Dermacentor genera, Little explained, it is not the case for brown dog ticks and ticks in the Amblyomma genus, including lone star ticks.

These ticks are “hunter ticks.”

Amblyomma are drawn to the pheromones and carbon dioxide the hosts give off, their shadow, and movement. Similarly, brown dog ticks pick up on environmental cues that signal a dog is nearby and run after these canines.

Some species, like the American dog tick and Ixodes scapularis (deer tick), can move approximately 12 to 18 inches towards a host through static electricity. “Ticks have a static charge on them, so even if you don't brush the vegetation, even if you're very careful to stay in the center of the trail, the tick will still kind of move across a little air space there to get to the host. They're not flying, but they're just being drawn by that static charge,” said Little.

Once the tick reaches the host, it will move toward its preferred feeding site. According to Little, in dogs, the majority of Ixodes are found on the face, while Dermacentor usually attach themselves along the back of a dorsal surface and Amblyomma prefer feeding in the ventral area.

“And this matters, because when you're examining a dog for ticks, you know, we can't just sort of look in the ears and down the back and be done,” emphasized Little, explaining that lone star ticks can bury themselves in inguinal or axillary areas. She noted that the brown dog tick is notorious for hiding between dog’s toes.

Once attached, ticks secrete saliva that contains vasodilators, platelet inhibitors, anesthetics, and anti-inflammatory compounds that not only help the tick feed, but also modifies the host's immune response, making it more susceptible to pathogen transmission.

Pathogen transmission time

“One of the [other] issues for understanding how quickly the pathogen is transmitted is what we consider transmission, right?” said Little.

She explained that the definition of “transmission” can vary depending on polymerase chain reaction (PCR) positivity, antibody seroconversion, or development of clinical disease.

For rickettsial agents, including Anaplasma, Ehrlichia, and Rickettsia species, transmission speed has generally been found to be faster, with some studies showing it can be as early as 4 to 12 hours as the pathogens are already in the tick’s salivary glands.¹ Clinical symptoms, however, may take longer to show up.

Meanwhile, Borrelia species take longer to transmit disease, with studies showing transmission time being between 24-48 hours or more, generally.¹ According to Little, Borrelia spirochetes are found in the tick’s midgut and need to move to the salivary glands and change their outer surface protein expression in order to be able to infect the host.

Transmission time for Babesia and Cytauxzoon is also long, with these pathogens being transmitted approximately after 48 to 72 hours or more due to a delay in the formation of infective stages.

Reference

1. Little S. Perfect Timing: Protecting Dogs From Tick-Borne Infections. Presented at: American Veterinary Medical Association Convention; Washington, DC; July 18-22, 2025.