Distribution, genetic characteristics and public health implications of Triatoma rubrofasciata, the vector of Chagas disease in Guangxi, China

Abstract

Background: Triatomines are natural vectors of Chagas disease and are mainly prevalent in the Americas. In China, previous data from decades ago showed that there were two species of triatomine bugs, Triatoma rubrofasciata and T. sinica. However, the distribution, genetic characteristics and public health implications of triatomines in China are still relatively unknown. In order to gain knowledge on the distribution, genetic characteristics and public health implications of the triatomines in Guangxi, China, an entomological-epidemiological study and genetic research was conducted.

Methods: Different methods were used to elucidate the distribution of triatomines in Guangxi including consultations with county-level Center for Disease Prevention and Control staff and village doctors, the distribution of educational material on triatomines though the internet and social media apps such as Wechat and QQ, and conducting manual inspections and light trapping to collect triatomines. The morphological characteristics of the collected triatomines were identified under light microscopy. The mitochondrial 16S rRNA, cytochrome b (cytb) genes and nuclear 28S rRNA gene were amplified, sequenced and used in phylogenetic analyses.

Results: A total of 305 triatomines were captured from 54 different sites in 13 cities in Guangxi. All collected bugs were identified as T. rubrofasciata based on morphology. Most triatomine collection sites were around or inside houses. Four triatomines bite cases were observed during the investigation indicating that triatomine bites are common, the bites can cause serious anaphylaxis and skin papules and urticaria, suggesting a systemic skin response. The 16S rRNA, 28S rRNA and cytb sequence analyses of T. rubrofasciata from Guangxi and other countries showed that T. rubrofasciata sequences from different regions exhibit a high similarity, with no geographical differences. The phylogenetic tree based on the 16S rRNA and cytb genes showed that T. rubrofasciata sequences from different regions and continents were in the same cluster, indicating no differentiation among different geographical populations.

Conclusions: Our study showed that T. rubrofasciata is widely distributed in Guangxi and that people are commonly bitten by this insect in some regions. This highlights the need to enhance surveillance for and control of T. rubrofasciata and to strengthen the monitoring of imported Trypanosoma cruzi in China. The 16S rRNA, 28S rRNA and cytb sequence analyses of T. rubrofasciata from different regions and continents suggested that T. rubrofasciata populations exhibit high similarity, and the clustering in the phylogenetic analyses indicates that T. rubrofasciata has a close ancestor originating in the Americas.

Keywords: Distribution; Genetic characteristics; Guangxi; Triatoma rubrofasciata.

Fig. 1

The distribution of Triatoma rubrofasciata in Guangxi, China. Over the two years of study, triatomines were found in 54 cities (red dots). Except for Guilin city (highlighted with blue), 13 other cities in Guangxi Zhuang Autonomous Region were positive for T. rubrofasciata

Fig. 2

The living habit of Triatoma rubrofasciata. a T. rubrofasciata tend to hide in woodpiles; b T. rubrofasciata found in a woodpile; c T. rubrofasciata tend to hide near chicken coops. d T. rubrofasciata found in a house when cleaning

Fig. 3

Morphology of Triatoma rubrofasciata. a An adult male (left) and female (right). b Morphological characteristics of T. rubrofasciata: 1, there is an orange-red margin along the outer edge of the abdomen as well as the side of the pronotum; 2, the pronotum is dark brown or black and conspicuously granulose; 3, the scutellum is wide at the base and tapers to the tip; 4, the head is uniformly dark and heavily granulose dorsally; 5, the 1st segment of antenna surpasses the head

Fig. 4

Four Triatoma rubrofasciata bite cases. a A bite by an adult T. rubrofasciata caused cutaneous symptoms including urticaria, flushing, pruritus, and angioedema. b A bite by an adult T. rubrofasciata (middle) caused palpebral oedema (left) and slight skin redness on the back (right). c A bite by a fifth-instar T. rubrofasciata (left) caused an urticarial skin reaction and slight redness on the arm (right). d A woman was bitten by an adult T. rubrofasciata on her foot, thigh and knees while sleeping

Fig. 5

The phylogenetic tree based on the 16S rRNA gene sequences for Triatoma rubrofasciata from Guangxi and other related species. The phylogenetic tree constructed by MEGA using the neighbour-joining (NJ) method with 1000 bootstrap replications. The sequences from this study were highlighted with red color. Abbreviations: GD, Guangdong Province; TW, Taiwan

Fig. 6

The phylogenetic tree based on the cytb gene sequences for Triatoma rubrofasciata from Guangxi and other related species. The phylogenetic tree constructed by MEGA using the neighbour-joining (NJ) method with 1000 bootstrap replications. The sequences from this study were highlighted with red color. Abbreviations: GD, Guangdong Province; TW, Taiwan