Abstract
BackgroundSeveral studies addressed changes on the insect vector behavior due to parasite infection, but little is known for triatomine bugs, vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. We assessed infection rates and metacyclogenesis of T. cruzi (TcVI) in fifth-instar nymphs of Triatoma rubrovaria comparing with the primary vector Triatoma infestans. Also, biological parameters related to feeding-excretion behavior were evaluated aiming to identify which variables are most influenced by T. cruzi infection.Methodology/principal findingsFifth-instar nymphs of T. rubrovaria and T. infestans were fed on mice infected with T. cruzi (TcVI). We compared the presence and the number of parasite evolutive forms in excreta of both triatomine species at 30, 60 and 90 days post-infection (dpi) with traditional statistical analyses. Moreover, both species were analyzed through generalized linear models and multinomial logistic regression hypotheses for seven behavioral parameters related to host-seeking and feeding-excretion. Triatoma rubrovaria and T. infestans had similar overall infection and metacyclogenesis rates of T. cruzi TcVI in laboratory conditions. Regarding vector behavior, we confirmed that the triatomine’s tendency is to move away from the bite region after a blood meal, probably to avoid being noticed by the vertebrate host. Interspecific differences were observed on the volume of blood ingested and on the proportion of individuals that excreted after the blood meal, revealing the higher feeding efficiency and dejection rates of T. infestans. The amount of ingested blood and the bite behavior of T. rubrovaria seems to be influenced by TcVI infection. Infected specimens tended to ingest ~25% more blood and to bite more the head of the host. Noteworthy, in two occasions, kleptohematophagy and coprophagy behaviors were also observed in T. rubrovaria.Conclusions/significanceLaboratory infections revealed similar rate of T. cruzi TcVI trypomatigotes in excreta of T. rubrovaria and T. infestans, one of the most epidemiological important vectors of T. cruzi. Therefore, TcVI DTU was able to complete its life cycle in T. rubrovaria under laboratory conditions, and this infection changed the feeding behavior of T. rubrovaria. Considering these results, T. rubrovaria must be kept under constant entomological surveillance in Rio Grande do Sul, Brazil.
Highlights
Vector-borne diseases represent nearly 17% of all known infectious diseases and are responsible for ~700,000 deaths annually [1]
Epidemiological relevance and concluding remarks. These results based on a unique and large dataset analyzed through classical statistical methods coupled with exhaustive generalized linear model and multinomial logistic regression hypotheses indicate that laboratory T. cruzi TcVI infection changed the T. rubrovaria feeding behavior
Despite the lower percentage of T. rubrovaria defecating after the blood meal and the lower volume of ingested blood when compared with one of the main important Chagas disease vectors in South America, T. infestans, these vector species shared similar overall infection and metacyclic trypomastigote rates of T. cruzi TcVI in their excreta under laboratory conditions, and shared similar scores for most of the feeding-excretion parameters
Summary
Vector-borne diseases represent nearly 17% of all known infectious diseases and are responsible for ~700,000 deaths annually [1]. The incidence of a vector-borne disease is determined by several factors, including the density of primary vectors, efficient parasite replication and infectivity in vertebrate and invertebrate hosts, and the presence of susceptible hosts [2, 3]. Pathogens can impose a fitness cost in life-history traits of vectors, which can influence parasite transmission [5, 6]. [7, 8]), and very little is known for triatomine bugs (Hemiptera, Reduviidae), vectors of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae), the etiological agent of Chagas disease (ChD). Several studies addressed changes on the insect vector behavior due to parasite infection, but little is known for triatomine bugs, vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Biological parameters related to feeding-excretion behavior were evaluated aiming to identify which variables are most influenced by T. cruzi infection
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