UC Riverside scientists have identified new hosts for a parasite that causes Chagas disease, a chronic, debilitating condition that is spread by insects called “kissing bugs.”
The research, which was published this month in the journal PeerJ, broadens the list of animals that can transmit the disease, which should help control the deadly scourge that afflicts more than 8 million people worldwide.
The new hosts include tayras, solitary weasel-like animals; new world monkeys; sloths; porcupines; and coatis — which are the South American cousins of racoons.
“There are 152 species of kissing bug, but we don’t know much about most of them, including the animals they feed on that can act as reservoirs for the parasite,” Christiane Weirauch, a professor of entomology in UCR’s College of Natural and Agricultural Sciences, said in a UCR news release. “Overall, the existing data is piecemeal, scattered, and biased toward a handful of heavily studied and well-documented species, while little data exists for insects that are found in very secluded habitats.”
The research, led by Anna Georgieva, an undergraduate majoring in biology, and Eric Gordon, a graduate student researcher in Weirauch’s lab, will support efforts to control the disease, particularly in poor, rural populations in South America, according to a UCR release.
Chagas disease is caused by the parasite Trypanosoma cruzi, which is transmitted to animals and humans by members of the assassin bug subfamily called kissing bugs that feed on blood and are named for their tendency to bite people around the mouth.
According to the Centers for Disease Control and Prevention, kissing bugs become infected with T. cruzi by biting an infected animal or person and, once infected, they pass T. cruzi parasites in their feces. When they bite a person and ingest blood, they defecate on them.
A person can become infected if bug feces enters their body through mucous membranes or skin lesions caused by the bite wound or scratching. Research also suggests that animals can become infected by eating other animals that harbor the parasite.
Although Chagas disease is common in rural areas, identifying new hosts among tree-dwelling, and sometimes nocturnal animals is a challenge, the release states. To sidestep this problem, the researchers identified new hosts by studying their blood—which they isolated straight from the guts of kissing bugs. The sample included 64 kissing bug samples collected from Central and South America between 2005 and 2015 that were preserved in ethanol.
“Our modern approach using DNA allowed us to determine this wide variety of animal hosts without a bias towards ones that are already known, unlike some older detection methods” Georgieva said in the UCR news release.
DNA analyses of the ingested blood revealed host associations for 24 of the samples. Among the newly identified hosts was the tayra, which has never before been named as a host for kissing bugs.
“Education and pesticide application around homes has helped reduce the impact of kissing bugs associated with homes and domestic animals, but now more and more cases of Chagas disease are driven by species most often associated with more rural hosts,” Gordon said in the statement. “One important consideration in controlling Chagas disease in wild animals is the possibility of bioaccumulation of the parasite in certain carnivores near the top of the food chain.
“If kissing bugs also feed on these carnivores, as has occurred for the tayra in our study, they are likely to be one of the important links in the transmission chain of the disease in the wild. If a vaccine becomes available one day in the future, they are good candidates to target for immunization to halt the natural spread of the parasite and potentially help to eradicate the pathogen.”
Do you know how long the researchers were in South America? Or are they working with researchers down there who sent them the specimens?
Gordon: “Weirauch lab members have spent months in total collecting these samples in South America (two and a half weeks in French Guiana, three weeks in Costa Rica, one month in Ecuador) but we have also received many additional specimens from other researchers, for example, those working in Mexico, Peru and Nicaragua.
Weirauch: “During these trips we also study and collect thousands of other specimens. Many are plant pests, some are beneficial insects, all belong to the true bugs.”
Why was this study done at UCR? Are other colleges in South America or researchers working on similar studies?
Gordon: “This study was conducted at UCR because the Weirauch Lab at UCR or “the True Bug Lab” is the leading group of researchers in the study of the evolutionary relationships of the Reduviidae, or assassin bugs, which are the insect family that kissing bugs belong to. In the process of gathering samples for the study of that larger group, we have amassed many samples of kissing bugs which we used to conduct this study.”
Are other colleges in South America or researchers working on similar studies?
Gordon: “Other researchers in North America and South America have been working on similar studies (see for example Gorchakov et al. 2016 and Gottdenker et al. 2012, but many others exist). In comparison to most other studies, ours is somewhat different in having worked on specimens sometimes stored for years in ethanol as well as having many specimens collected from a wild environment as opposed to in association with domestic or man-made habitats.”