Research from USA scientists suggests ticks may transmit leprosy to people

Natthida Tongluan, a graduate research assistant in the Department of Microbiology and Immunology, conducts research in the Laboratory of Infectious Diseases. 

For most of a century, researchers have explored the potential role that arthropods – such as ticks – play in the transmission of leprosy to humans and other animals, with little luck. Conclusive evidence hasn’t emerged on the topic in more than 80 years.

With that in mind, researchers from the USA College of Medicine, in collaboration with the U.S. Department of Health and Human Services, have taken up the hunt.

The results of a recently published study from that collaboration suggests that ticks themselves might serve as the point of transmission for leprosy and that tick cells are suitable for maintaining a viable form of the disease for an extended period of time.

Perhaps best known from biblical references, leprosy, also known as Hansen’s disease, is an infection caused by Mycobacterium leprae, a bacteria found in the southern United States and elsewhere that spreads to animals, namely armadillos, and people. The majority of patients diagnosed with leprosy spend extensive time outdoors but only rarely report any direct contact with wild armadillos, said Natthida Tongluan, a graduate research assistant in the Department of Microbiology and Immunology and lead author of a research paper published in Frontiers in Microbiology on the topic.

Whether leprosy is transmitted to new vertebrate hosts through the environment independently or with the help of other organisms, like ticks, remains a fundamental question in leprosy transmission.

The study aimed to assess the potential for ticks to transmit leprosy and to test if the disease could be maintained in tick-derived cells. To do that, ticks in the nymph stage were injected with leprosy. Testing later found that ticks infected as nymphs harbored the disease through some stages of their life. Transmission of leprosy to a lab model also was observed as DNA was detected in multiple tick life cycle stages.

What the collaborators found through the research was that tick-derived cells were able to maintain viable disease during a 49-day course of infection, and the leprosy remained infectious within tick cells for at least 300 days.

Kevin Macaluso, Ph.D., chair of microbiology and immunology, said the new research advances the field by establishing a model transmission system to help reveal the ecology of leprosy in the Americas.

In the near future, Macaluso hopes to be able to pinpoint the transmission details of leprosy by ticks.