Current Primary Literature

            It is well known that triatomine insects are the main vectors of the parasite T. cruzi, the pathogenic agent of Chagas disease.  Because these vectors are found primarily in tropical climates, the prevalence of Chagas disease is restricted mostly to Central and South America.  However, if another insect were able to serve as a vector for the parasites, the prevalence of the disease may extend beyond the tropical areas.  With the continuing rise of bedbugs as a public heath problem, Salazar et al. (2015) wanted to investigate if common bedbugs could serve as a vector for T. cruzi and facilitate the spread of Chagas disease, questions that could have grave implications.

            To do this, experimenters set up four experiments.  In the first, experimenters sought to determine if infected mammalian hosts could transfer T. cruzi to bed bugs.  They infected ten female mice with the parasites and allowed bedbugs to feed on the mice.  After 21 days, researchers extracted feces from the bedbugs and analyzed it microscopically for the presence of T. cruzi.  They found that a majority of the bedbugs contracted the parasites and released them through their feces.

From Salazar et al. (2015)

            In the second experiment, researchers sought to determine if bedbugs could transmit T. cruzi to a mammalian host.  To do this, researchers infected a group of mice with the parasites, allowed bedbugs to feed on those mice, allowing them to become infected, and then allowed those infected bugs to cohabitate with uninfected mice for 30 days.  Blood samples were taken from the mice every 6 days and examined for parasites.  Researchers found by the end of the 30-day period that 58% of mice exhibited parasitemia.

            In the third experiment, researchers attempted to determine the ease at which the parasites could be transmitted transcutaneously.  To do this, researcher shaved a portion to the fur from a group of mice, caused microtrauma to some via pricks with a tuberculin needle, and caused microtrauma to other via application of uninfected bedbugs, which would produce bite bounds.  Finally, researchers applied a solution containing infected feces to the trauma areas.  Blood analysis determined that 60% of the mice the received needle pricks developed parasitemia, and 20% of those with bite wounds developed parasitemia.

            In the fourth experiment, researchers analyzed the defecation patterns of bedbugs after a blood meal.   By developing an apparatus that simulated human skin and recording the bugs with a video camera, researchers were able to determine that 83% of the bugs that fed on the blood also defecated near the feeding site, suggesting a high probability of infected feces coming in contact with bite wounds, causing infection.

            Although the results found here seem conclusive, this experiment needs to be replicated many more times.  The number of mice used in each experiment was very low (at most 12) and results with so few trials lacks statistical power.  Additionally, many other factors should be controlled for, or analyzed separately.  Temperature, for example, may play a large role in the tendency, or ability of the bed bugs to bite the mice.  If temperature is a significant variable, experimental results may help narrow the geographical area where bed bugs could potentially become a significant epidemiological problem.

Reference:

Salazar, R., Castillo-Neyra, R., Tustin, A., Borrini-Mayori, K., Naquira, C., & Levy, M. (2015). Bed Bugs (Cimex lectularius) as Vectors of Trypanosoma cruzi. American Journal of Tropical Medicine and Hygiene, 331-335. doi:10.4269/ajtmh.14-0483