MVCAC 2018 Annual Conference
Vector Ecologist Tara Roth’s presentation on Tularemia

On January 29, Vector Ecologist Dr. Tara Roth gave a presentation at the annual conference of the Mosquito and Vector Control Association of California in Monterey, CA. Tara received her PhD in August of 2016 from University of California, Davis, where she researched the vector-borne disease tularemia. Surveillance for tularemia in San Mateo County will be beginning soon through cooperation with the California Department of Public Health.

People may know the disease tularemia by its other names, “fly bite fever” or “rabbit fever,” but few may know the life history of this disease or where it can be found in the state of California. In the 1930’s and 1940’s thousands of cases of tularemia were reported every year but in recent years, infections are very rare – often less than 20 for the entire state. Symptoms usually include high fever, aches and pains, swollen and painful lymph nodes, swollen liver and spleen, and sometimes an ulcer at the site of the infection. Serious cases that are untreated can have a fatality rate of 40% so the disease is considered dangerous by the Center for Disease Control and Prevention.

Tularemia is caused by a bacterium called Francisella tularensis and in the United States it is usually carried by hard ticks such as the dog tick or the west coast tick. However, most vectors, such as biting flies and fleas, are capable of transmitting it to other animals if they come in contact with an infected host. The disease is called rabbit fever because it is particularly deadly to rabbits and can wipe out entire populations in fields in a matter of weeks. Over 300 different hosts, anything from house mice to rhesus macaques, have been found to be infected, making tularemia one of the most adaptable diseases in existence. Humans typically come in contact with the disease through hunting rabbits or from being bit by a tick that is infected.

From January 2013 to December 2014, Vector Ecologist Tara Roth attempted to uncover where the disease could be found in the California Central Valley by looking at an area that had repeated outbreaks of the disease over many years. She collected mosquitoes, ticks, biting flies and a variety of rodents and mesocarnivores such as raccoons, skunks and opossums, in order to find the source of the disease. Ultimately, she found that the disease seemed to be centered around bodies of water such as ponds and streams and likely traveled quietly until infecting a susceptible animal like a rabbit or ground squirrel. The rapid explosion of the disease in these animals likely led to the outbreaks seen in the public health records.