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Are We Cuddling up to Kissing Bugs?

Published:December 30, 2013DOI:https://doi.org/10.1016/j.amjmed.2013.11.021
      SEE RELATED ARTICLE p. 421
      Kissing bugs are well known as the carriers of the deadly Chagas parasite, which causes the most serious parasitic disease in Latin America. Seven to 8 million people are currently infected with the Chagas parasite, and 30%-40% of these are headed for life-threatening heart disease. But are we encountering the kissing bug vectors in the US?
      Indeed, only 23 autochthonous Chagas cases have been described in the US, 16 of which were found after screening nearly 30 million blood units.
      • Cantey P.T.
      • Stramer S.L.
      • Townsend R.L.
      • et al.
      The United States Trypanosoma cruzi Infection Study: evidence for vector-borne transmission of the parasite that causes Chagas disease among United States blood donors.
      Most of us live in houses with screened windows and air conditioning, excluding the bugs. And all 12 of the US species of bugs are thought to live in wild areas, and prefer wild animals for blood sources. However, recent studies challenge the dogma that people and kissing bugs don’t meet in the US.
      Surprisingly, nearly all (91% of 11) kissing bugs collected in a sylvan environment in Arizona had fed on human, as we report in the accompanying article. This confirms a previous study in which we found that 38% of kissing bugs collected in Arizona and California had fed on human blood.
      • Stevens L.
      • Dorn P.L.
      • Hobson J.
      • et al.
      Vector blood meals and Chagas disease transmission potential, United States.
      In addition, in our current study, 27% of the bugs that also had fed on human harbored the Chagas parasite, pointing to an epidemiological risk. Thus, even in sylvan areas, humans are encountering Chagas-infected kissing bugs. However, in a third study, only one of 96 bugs in which a blood meal was found had fed on humans.
      • Kjos S.A.
      • Marcet P.L.
      • Yabsley M.J.
      • et al.
      Identification of bloodmeal sources and Trypanosoma cruzi infection in triatomine bugs (Hemiptera: Reduviidae) from residential settings in Texas, the United States.
      Among immigrants, there are an estimated 300,000 in the US that unknowingly are infected with the Chagas parasite, resulting in an estimated 30,000-45,000 cases of cardiomyopathy annually. Moreover, a robust sylvan cycle exists. At least 8 of the US species of kissing bugs carry the Chagas parasite, and kissing bugs are distributed across the lower two thirds of the country. A very high prevalence of the parasite in particular kissing bug species (>50% infected) is found in several localities. The high genetic diversity of the parasite suggests it is a long-term, native inhabitant, making it unsurprising that the parasite has been found naturally infecting 24 mammals in the US.
      Why so few human cases? Kissing bug species in the US display late defecation following a blood meal (the parasite is transmitted in the feces), so they are perhaps inefficient vectors.
      • Klotz S.A.
      • Dorn P.L.
      • Klotz J.H.
      • et al.
      Feeding behavior of triatomines from the southwestern United States: an update on potential risk for transmission of Chagas disease.
      However, blood donors are not a representative sample of the population, and those at greatest risk (living in rural areas in substandard housing or homeless) are less likely to donate. And spikes in severe allergic reactions attributed to kissing bug bites during the summer months provide additional evidence of human/vector contact. Indeed, in some localities there are more anaphylactic reactions from kissing bug bites than from hymenopterans, including bee, wasp, and ant stings.
      We are very likely missing cases, and a systematic survey of the high-risk population in the US is urgently needed. In the meantime, we recommend that physicians consider testing their at-risk patients, especially pregnant women who can pass the parasite congenitally, and consider both Chagas, as a differential diagnosis for idiopathic heart disease, and kissing bug bites when patients present with severe allergic reactions. New data tell us that we are, in fact, cuddling up to kissing bugs in the southern US.

      References

        • Cantey P.T.
        • Stramer S.L.
        • Townsend R.L.
        • et al.
        The United States Trypanosoma cruzi Infection Study: evidence for vector-borne transmission of the parasite that causes Chagas disease among United States blood donors.
        Transfusion. 2012; 52: 1922-1930
        • Stevens L.
        • Dorn P.L.
        • Hobson J.
        • et al.
        Vector blood meals and Chagas disease transmission potential, United States.
        Emerg Infect Dis. 2012; 18: 646-649
        • Kjos S.A.
        • Marcet P.L.
        • Yabsley M.J.
        • et al.
        Identification of bloodmeal sources and Trypanosoma cruzi infection in triatomine bugs (Hemiptera: Reduviidae) from residential settings in Texas, the United States.
        J Med Entomol. 2013; 50: 1126-1139
        • Klotz S.A.
        • Dorn P.L.
        • Klotz J.H.
        • et al.
        Feeding behavior of triatomines from the southwestern United States: an update on potential risk for transmission of Chagas disease.
        Acta Trop. 2009; 111: 114-118

      Linked Article

      • Free-roaming Kissing Bugs, Vectors of Chagas Disease, Feed Often on Humans in the Southwest
        The American Journal of MedicineVol. 127Issue 5
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          Kissing bugs, vectors of Trypanosoma cruzi, the parasite that causes Chagas disease, are common in the desert Southwest. After a dispersal flight in summer, adult kissing bugs occasionally gain access to houses where they remain feeding on humans and pets. How often wild, free-roaming kissing bugs feed on humans outside their homes has not been studied. This is important because contact of kissing bugs with humans is one means of gauging the risk for acquisition of Chagas disease.
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