Chagas disease in Trinidad and Tobago – a call to action

Abstract

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a vector-borne disease that can lead to serious cardiac alterations. The Caribbean nation of Trinidad and Tobago (TT) is not considered Chagas endemic by major public health organizations, but Trinidad is home to six T. cruzi vector species as well as T. cruzi–infected vertebrate hosts, including humans. Here we present the most comprehensive assessment to date of Chagas disease in TT based on information from published literature, museum specimens, hospital and veterinary records and archival documents. Panstrongylus geniculatus is the most abundant and well-studied T. cruzi vector species in TT, where it is found in and around human homes with human blood meals and with T. cruzi infection prevalences >83%. Wildlife reservoirs of T. cruzi in TT include commonly hunted species, which may pose a risk of T. cruzi transmission during preparation or consumption of infected carcasses. Blood bank data from 2020 showed a 0.5% seropositivity rate for T. cruzi, which is higher than that reported for 13 Chagas-endemic countries. By presenting the entomological, ecological, epidemiological and clinical evidence in a single report, we aim to present what is known about Chagas disease on the island, identify knowledge gaps and pinpoint areas of future research and public health focus, with the goal of sending a call to action for increased attention to Chagas disease in TT.

Introduction

Chagas disease is a zoonotic vector-borne infection caused by the kinetoplastid protozoan Trypanosoma cruzi.¹ The parasite is spread by triatomine bugs (‘kissing bugs’), which are obligate, blood-feeding arthropods.² Chagas disease is vector-borne throughout most of the Americas, where it is estimated that 6–7 million people are infected with T. cruzi and 70 million more at risk.³

The Chagas disease course in humans consists of a short acute phase followed by a lifelong chronic phase. The acute phase lasts 6–8 weeks and is characterized by flu-like symptoms and T. cruzi parasites that are detectable on visual examination of a blood smear.^4,5 Patients in the acute phase experience the best outcomes (80–100% efficacy) when treated with antitrypanosomal drugs,⁶ although it is estimated that only a small percentage of acute cases are diagnosed.⁷ If left untreated, approximately 99.5% of patients in the acute phase will enter the chronic indeterminate phase of Chagas disease, which is generally not cured with antitrypanosomal drug treatment, but treatment can slow disease progression.⁸ In the chronic indeterminate phase, the patient is asymptomatic, but antibodies against T. cruzi antigens are detectable.⁶ An estimated 30–40% of those in the indeterminate chronic phase will eventually progress into the symptomatic phase of Chagas disease, which is characterized by chronic cardiomyopathy but can also include gastrointestinal disease and/or neurological alterations.⁷ An estimated 10 000 people per year die of Chagas-related causes,⁷ but as a chronic infection, its true impact is demonstrated in the disability-adjusted life years (DALYs) associated with the disease, which are the highest of any parasitic infection in the Americas.^9,10

T. cruzi is a parasite of mammals that is transmitted stercorally via the excrement of triatomine bugs.¹¹ During this form of transmission, T. cruzi enters the vertebrate host through mucous membranes or other openings in the skin that come into contact with the T. cruzi–infected triatomine excrement.⁶ Other T. cruzi transmission routes include T. cruzi–contaminated blood transfusion or organ transplants, ingestion of contaminated food or drink products and transplacental transmission from mother to foetus.⁶  T. cruzi transmission is also possible through the consumption of food contaminated by urine or secretions from marsupial scent glands that contain T. cruzi metacyclic trypomastigotes,¹² and possibly from consumption of raw or undercooked meat from T. cruzi–infected animals.^13–15

There are 159 extant known species of triatomine bugs, most of which are endemic to the Americas and the Caribbean,^16–19 including one genus (Nesotriatoma) and three species that are found only in Cuba (Nesotriatoma flavida, Nesotriatoma obscura and Bolbodera scabrosa) and Jamaica (N. obscura).^20–22 Triatomine bugs become infected with T. cruzi by feeding on the blood of infected mammals or by feeding on a T. cruzi- infected triatomine bug (kleptohematophagy) or infected triatomine faeces (coprophagy).^2,23 Vector-borne T. cruzi transmission occurs in sylvatic environments without human participation and also in domestic and peridomestic environments with human hosts.¹² Triatomine species of the greatest epidemiological interest are those that are able to infest and breed within human homes as well as species that can move between different types of environments. These species serve as links between sylvatic and domestic transmission cycles resulting in transmission scenarios in which disease elimination is difficult. Vector control has proven to be the most useful method to prevent Chagas disease transmission in Latin America, as the disease often goes undiagnosed and treatment efficacy is limited.⁶ The World Health Organization (WHO) estimates that the costs associated with Chagas disease treatment are at least 80% higher than vector control costs,²⁴ highlighting the importance of vector control in public health efforts to combat Chagas disease.

At least 8 of the estimated 37 Caribbean island nations and territories have endemic triatomine bug species, T. cruzi–infected animals and/or T. cruzi–positive human serology,^25–28 but the US Centers for Disease Control and Prevention states that vector-borne T. cruzi transmission has not been documented in the Caribbean islands.²⁹ There is little Chagas disease surveillance in the Caribbean, so it is difficult to assess the accuracy of this statement given the limited monitoring for the disease.^28,30,31 There is however at least one Caribbean island for which strong evidence of vector-borne Chagas disease exists: the island of Trinidad, in the dual island nation of Trinidad and Tobago (TT).³² The closest Chagas-endemic country to TT is Venezuela, which is home to 23 triatomine species.³³ Venezuela contains several different enzootic T. cruzi transmission cycles due to its heterogenous landscape, which spans the Andes Mountains, the plains region and the Amazon basin, among others. Chagas disease transmission in Venezuela was greatly reduced at the turn of the last century due to a successful vector control campaign,³⁴ but these gains have been lost in recent years and active T. cruzi transmission to children is being documented in both rural and urban areas of the country.³⁵

The island of Trinidad sits just 11 km off the northeastern tip of Venezuela and is home to six described triatomine bug species. T. cruzi–positive human serology has been reported several times in Trinidad, and T. cruzi–infected triatomine bugs and infected wild animals continue to be reported. Additionally, TT is also the only Caribbean island nation that screens its blood bank samples for T. cruzi markers, where it consistently reports a higher T. cruzi prevalence than countries considered endemic for Chagas disease.^36,37 Nonetheless, TT is not considered by the WHO or the Pan American Health Organization (PAHO) as a Chagas-endemic country. As a result, the nation does not receive the resources and support that accompany the designation as endemic, namely organizational support, training, inclusion in international initiatives and treatment donations.^38–40 Moreover, a non-endemic status can lead to misperceptions that the parasite and vectors are not there, which perpetuates a widespread lack of awareness of the disease.

Here we review the evidence for Chagas disease transmission in TT, collating information found in the published literature, government and institutional reports, epidemiological archives and museum specimens dating back to 1918. Due to a dearth of information on Chagas disease in Tobago, we focus primarily on Trinidad, although we include Tobago whenever possible. By presenting the entomological, ecological, epidemiological and clinical evidence in a single report, we aim to present what is known about Chagas disease on the island, identify knowledge gaps and pinpoint areas of future research and public health focus, with the goal of sending a call to action for increased attention to Chagas disease in TT.

Methodology

Our search methodology consisted of web searches on Google, PubMed, CAB Direct, Web of Science and Scopus using the search terms ‘Chagas disease’ and ‘triatomine bugs’ in combination with ‘The Caribbean’, ‘Trinidad and Tobago’, ‘humans’ and ‘dogs’ to retrieve published literature on Chagas disease in TT. We retrieved government and institutional records from the Main Library of the St. Augustine campus of the University of the West Indies. We examined museum specimens from the Smithsonian Museum of Natural History Department of Entomology collections (Washington, DC, USA), the American Museum of Natural History Hemiptera collection (New York, NY, USA) and the Entomology Museum of the University of the West Indies Department of Life Sciences (St. Augustine, Trinidad and Tobago). Lastly, we searched digital archives from the Rockefeller Foundation (dimes.rockarch.org) for historical records of Chagas disease in TT, including reports and diaries from employees of the now defunct Trinidad Regional Virus Laboratory. Documents were reviewed and all data related to any component of Chagas disease were collated and then organized into thematic categories: vectors, animal hosts, human hosts and epidemiology. Data from each theme were then synthesized and converted to the present form.

Our review is structured as follows: we begin with a brief overview of the ecological and geological features of TT that are relevant to understanding Chagas disease in the region. Next, we review what is known about the natural history (i.e. vectors and non-human hosts) of Chagas disease in TT, followed by a review of Chagas disease epidemiology in Trinidad. In the final section, we end with a call to action for One Health research and public health interventions to prevent Chagas disease transmission in TT.

Natural history

The republic of TT is a twin island nation in the southeastern Caribbean that is situated off the northeast coast of Venezuela. Both islands are bordered by the Atlantic Ocean to the east and the Caribbean Sea to the northwest. Trinidad is located nearest to Venezuela (approximately 11 km, as mentioned above) and Tobago sits approximately 30 km off Trinidad's northeastern coast (Figure 1). The two islands have similar maritime tropical climates characterized by a dry season and a rainy season, warm temperatures and high humidity.^41–43 The two islands differ greatly in size; Trinidad, with an area of 5000 km² (slightly smaller than the US state of Delaware) is >10 times larger than Tobago, which covers 298 km². Trinidad is the fifth largest island in the Caribbean and is home to the majority of the TT population. As a result, most of the Chagas research in TT has been carried out on the island of Trinidad, which is reflected in this review.

Figure 1.

Map of Trinidad and Tobago. © Blue Green Atlas, licensed under CC BY 4.0.

The geological history of Trinidad differs from its nearest island neighbours, including Tobago, in that it is not volcanic in origin, but rather sits on the edge of the South American continental shelf. The separation of Trinidad from the South American mainland occurred during the Pliocene era (5.3–2.6 million years ago), when the three mountain ranges currently found in Trinidad (the Northern Range, Central Range and Southern Range) were connected to what is today the Venezuelan coastal mountain range.⁴¹ This relatively recent separation of the island of Trinidad from the continent likely resulted in the diverse array of terrestrial ecosystems found in Trinidad, comprising evergreen and deciduous forests, rainforests, forested wetlands (including mangroves), marshes and savannahs. The ecosystems of Trinidad contain a high species diversity:surface area ratio that closely resembles that of the equatorial South American mainland,^42,44 including approximately 420 species of birds, 100 mammal species, 25 amphibian species and 85 reptile species.⁴⁵ The ecological diversity found in Trinidad as well as its resemblance to the South American continent is important for understanding Chagas disease in Trinidad, as it may explain why Trinidad is home to six triatomine bug species (the highest number of triatomine species of any Caribbean island; Figure 1), all of which are also found in Venezuela. Trinidad is also home to the parasite T. cruzi and several T. cruzi reservoir species including Dasypus novemcinctus (nine-banded armadillo), Dasyprocta leporina (red-rumped agouti) and Didelphis marsupialis (common opossum).^46–48

Chagas disease vectors

There are six triatomine bug species in Trinidad—Panstrongulis geniculatus (Latreille, 1811), Microtriatoma trinidadensis (Lent, 1951), Triatoma rubrofasciata (De Geer, 1773), Rhodnius pictipes (Stål, 1872), Eratyrus mucronatus (Stål, 1859) and Panstrongylus rufotuberculatus (Champion, 1899)—and two species in Tobago—P. geniculatus and R. pictipes. All species are native except T. rubrofasciata. Although collecting entomological specimens from the tropics was a popular pastime among field naturalists worldwide (Table 1 lists the nationalities of each collector, highlighting the colonial nature of early 20th century tropical entomological exploration), published records and studies of triatomines in TT are sparse. The following is a short local history of each triatomine bug species beginning with the earliest mention of the species in Trinidad, based on available data, reports and collections.

Table 1.

Overview of triatomine species history in Trinidad.

Species	Earliest local record	City	Collector (nationality, profession)	Epidemiological importance
Panstrongylus geniculatus	19181	San Fernando	C. B. Williams (English entomologist)	Highest
Microtriatoma trinidadensis	192154	Arima	Friederick William Urich (Trinidadian professor and naturalist)	Low
Triatoma rubrofasciata	<195160	Unknown	Unknown	Low
Eratyrus mucronatus	196622	Northern Trinidad	Boris Fistein (British cardiologist)	Mid-low
Rhodnius pictipes	196622	Northern Trinidad	Boris Fistein (British cardiologist)	Mid-low
Panstrongylus rufotuberculatus	198472	Blanchisseuse	Indira Omah-Maharaj (Trinidadian professor and ecologist)	Low

Panstrongylus geniculatus

The earliest scientific record of Triatominae in Trinidad pertains to the species P. geniculatus, a medium-sized species (adults measure 20–30 mm in length) that is characterized by an overall light orange-brown coloration and yellow-brown on its coxae, trochantera and lower femur (i.e. the leg joints; Figures 2 and 3). The P. geniculatus specimen was collected in July 1918 in San Fernando, Trinidad, a municipality on the western coast of the island. The specimen was collected in a light trap in a sugar cane field by English entomologist C. B. Williams (Table 1).⁴⁹ The record was not published and exists only in a database of specimens in the University of the West Indies Land Arthropod Collection (https://www.gbif.org/occurrence/4132965146).

Figure 2.

P. geniculatus specimen from the University of the West Indies Zoological Museum. Specimen was collected at a light in Trinidad in 1997. ID: UWIZM.2022.4.992. Photo: R. Suepaul.

Figure 3.

Dorsal (left) and ventral (right) views of a P. geniculatus male captured in Diego Martin, Trinidad in 2022. Photos: Dr Akilah Stewart (https://www.inaturalist.org/observations/118564356).

Later records indicate that P. geniculatus has been a frequently encountered triatomine species in Trinidad for at least the past 100 y. In the first publication mentioning P. geniculatus in Trinidad, Brazilian scientist Adolpho Lutz (later nominated for a Nobel Prize in Medicine) visited Trinidad and collected four specimens of ‘Triatoma geniculatus’. The year was 1925, and Dr Lutz described the species to be ‘frequent’ on the island.⁵⁰ Still, little attention was paid to the species in Trinidad by entomologists outside of Brazil, as indicated by Trinidad Regional Virus Laboratory (TRVL) entomologist Thomas H. G. Aitken.⁵¹ In a diary entry dated Monday, 25 October 1954, Aitken writes:

‘The Tabique boys came in…this morning. One of them brought me a Triatoma (kissing bug) which he got out of an armadillo's burrow. This may be an interesting find as we aren't aware of kissing bugs being reported in Trinidad. Wil has never found them in houses here and has questioned local people carefully on the matter. It is strange, as Triatomas [sic] are common on the mainland and, of course, involved in Chagas disease transmission’.

P. geniculatus has one of the largest geographical ranges of all triatomine species, from Costa Rica through much of South America,^52,53 and it exhibits tremendous variation in size and markings throughout its range. In their seminal 1979 revision of the Triatominae, Lent and Wygodinsky comment that the high variability in the markings on P. geniculatus specimens from Trinidad suggests the ‘possible existence of geographic races’ of the species.² Later phylogenetic analyses of P. geniculatus from Colombia revealed the existence of four geographically associated clades just in one portion of its range.⁵⁴ The genetic diversification of P. geniculatus is of high epidemiological interest because the species has exhibited a dramatic shift in the types of landscapes that it inhabits. While the species was once considered primarily a sylvatic species associated with armadillos and their burrows, P. geniculatus is now emerging as a cosmopolitan species that infests human homes and feeds on humans. P. geniculatus has been found in domestic settings in both rural and urban areas of Colombia, Venezuela, Bolivia and Brazil, including much of the Amazon.^55–64  P. geniculatus is also commonly implicated in oral Chagas disease transmission, with several cases involving the species in Colombia and Venezuela.^65–67 Oral Chagas cases tend to be far more severe than vector-borne cases, with much higher case fatality rates, and the risk of oral Chagas transmission in TT merits assessment.⁶⁸

Currently, P. geniculatus is encountered in human homes and yards in Trinidad and displays T. cruzi infection prevalences upwards of 50% (Table 2). Blood meals from 53 P. geniculatus specimens collected in residential areas of Trinidad in 2016 revealed that 30 (57%) of the 53 bugs had fed on humans (one blood meal species was detected per bug).⁶⁹ Of the 30 bugs with human blood meals, 26 (87%) were infected with T. cruzi (Table 3). In addition to humans, nine mammalian wildlife blood meals were detected along with blood meals from domestic chickens and three wild bird species (Table 3). These results suggested that P. geniculatus in Trinidad move between forest patches and residential areas, readily feeding on a variety of taxa. Most importantly, the results provided the first definitive evidence of contact between T. cruzi–infected triatomines and humans in Trinidad. Further epidemiological research and surveillance of P. geniculatus species in Trinidad is urgently needed

Table 2.

T. cruzi infection prevalence in the six triatomine species found in Trinidad from highest to lowest prevalence. Prevalence calculated using totals from studies cited next to species name.

Species	Bugs examined, n	Bugs infected, n	T. cruzi prevalence, %
Panstrongylus geniculatus 22,66,82	324	169	52.1%
Rhodnius pictipes 22,66,82	23	6	26.1%
Eratyrus mucronatus 22,66	14	0	0
Panstrongylus rufotuberculatus 66	2	0	0
Triatoma rubrofasciata	0	NA	NA
Microtriatoma trinidadensis	0	NA	NA

Table 3.

Blood meal hosts identified in blood meal analysis of 53 P. geniculatus specimens collected in Trinidad in 2016.⁸²

Species	Blood meals, n (% total bugs)	Bugs infected with T. cruzi, n (%)
Mammals
Human (Homo sapiens)	30 (57)	26 (87)
Howler monkey (Alouatta seniculus)	2 (4)	2 (100)
Agouti (Dasyprocta leporina)	2 (4)	2 (100)
Porcupine (Coendou prehensilis)	1 (2)	1 (100)
Mongoose (Herpestes javanicus)	1 (2)	1 (100)
Opossum (Metachirus nudicaudatus)	1 (2)	0
Water rat (Nectomys)	1 (2)	1 (100)
Spiny rat (Proechimys trinitatis)	1 (2)	0
Subtotal	39	33
Birds
Chicken (Gallus gallus)	10 (19)	9 (90)
Parrot (Pionus menstruus)	2 (4)	1 (50)
Woodpecker (Dryocopus lineatus)	1 (2)	1 (100)
Owl (Pulsatrix perspicillata)	1 (2)	1 (100)
Subtotal	14 (26.4)	12 (86)
Total (avian+mammalian)	53	44 (83)

1921: M. trinidadensis

The second Triatominae species observed in Trinidad, M. trinidadensis, was found in 1921. A single adult female M. trinidadensis was captured in Arima, a municipality situated in the central foothills of the Northern Range.⁷⁰ However, no record of the specimen was published and it was not identified down to the species level. Thirty years later, Brazilian entomologist Herman Lent reviewed the specimen and discovered it was a new triatomine species, the record for which was published in 1951. Lent named the species in honour of where it was first discovered: Bolbodera trinidadensis.⁷¹ The specimen was later determined to be the same species as Microtriatoma mansosotoi, so the two species were combined into a new species, M. trinidadensis.^2,70 The 1921 specimen from Trinidad is the type specimen for M. trinidadensis and is housed in the entomological collection of Herman Lent within the Triatominae Collection at the Oswaldo Cruz Institute in Rio de Janeiro, Brazil (Figure 4).^70,72

Figure 4.

Type specimen of M. trinidadensis. The specimen was collected in Trinidad in 1921. Photo from dos Santos Souza et al.⁷²

There are no published studies of M. trinidadensis in Trinidad, and little is known of its local ecology. Generally, the species is small (adults are 7–9 mm), relatively flat and widely distributed—its geographical range spans from Costa Rica to Brazil.²  M. trinidadensis is thought to be tightly associated with palm foliage, tree hollows and opossum nests,^73,74 and it is considered as sylvatic, although one report exists of M. trinidadensis in peridomestic environments in Bolivia.⁷³  M. trinidadensis is considered to be of low epidemiological importance in Trinidad, but a formal assessment is needed.

1951: T. rubrofasciata

T. rubrofasciata is the only introduced triatomine species in Trinidad. It is hypothesized that the species hitchhiked onto merchant ships with ship rats in the 17th century, after which it was introduced to port cities along maritime trade routes.⁷⁵ From where it dispersed is a topic of debate; some argue a New World origin (Brazil) and other argue an Old World origin (India).⁷⁶ Regardless, T. rubrofasciata is the only triatomine species found in both the Old and New Worlds. Indeed, it was the first named Triatominae species, based on specimens in current-day Indonesia in 1773.⁷⁵

T. rubrofasciata is medium sized (19–25 mm in length) with an overall dark brown to black colouring and yellowish and/or orange-red markings on its dorsal side (Figure 4).² The species has never been studied in Trinidad and nothing is known of its local ecology. The earliest available record of T. rubrofasciata in Trinidad was published in 1951, but it is not a primary observation,⁷⁷ suggesting that the first observation was prior to 1951. A search of entomological collections yielded an adult male T. rubrofasciata from Trinidad in the Carl J. Drake collection held by the Smithsonian National Museum of Natural History (Figure 5). The specimen was collected in 1962, confirming that the species was once in Trinidad.

Figure 5.

T. rubrofasciata specimen from Trinidad. Specimen is housed in the Smithsonian Museum of Natural History Entomological Collection. Photo: J. K. Peterson.

The epidemiological importance of T. rubrofasciata in Trinidad is presumed to be low, as it is unclear if the species is still present on the island; the most recent specimen we found was collected in 1972. In general, T. rubrofasciata is of low epidemiological importance for T. cruzi transmission, although a few specimens have been infected with T. cruzi in northeastern Brazil.⁷⁸ There is no record of T. rubrofasciata infected with T. cruzi outside of the Americas, although it has been found infected with the rat trypanosome species T. conorhini.⁷⁹ Additionally, T. rubrofasciata is a nuisance species in part of Southeast Asia and China, with painful, allergenic bites and the ability to infest houses in some regions.^79,80

1966: E. mucronatus and R. pictipes

The earliest record of R. pictipes and E. mucronatus in Trinidad was published in 1966, when the species were found in and around the homes of cardiac patients who tested seropositive for T. cruzi antibodies. The two species have overlapping distributions, spanning from Trinidad through the Amazon basin.^81,82 Little is known of either species in Trinidad. In general they are considered to be sylvatic species that come to artificial lights on the exterior of human homes, with R. pictipes being more frequently observed than E. mucronatus.^32,83

E. mucronatus is distinguished by its dark brown or black coloration with two orange-red spots on their dorsal side, adjacent to where their wings cross when folded (Figure 6, bottom photo). The species has a narrow body and measures 23–29 mm in length. Little is known of E. mucronatus in Trinidad; in other regions, the species is associated with animal nests, tree hollows and caves.⁸⁴ Although categorized as sylvatic, E. mucronatus specimens have been found inside human homes in Peru⁸⁵ and domiciliated populations have been reported in Bolivia.⁸⁶ In Trinidad, the species is rarely encountered and is currently of low epidemiological interest.

Figure 6.

Adult Rhodnius pictipes collected in Tanager Ridge, Tobago in 2023. Photo: Amy Deacon (https://www.inaturalist.org/observations/154022355).

R. pictipes is a small to medium-sized triatomine species (15–22 mm long) with a light brown body and a distinctive striped pattern around the bottom of the dorsal side (i.e. connexivum; Figure 7). In the Brazilian Amazon, R. pictipes is closely associated with palm trees, including the palm species Attalea maripa.^87,88  A. maripa is also common in Trinidad, where its edible fruits are commonly consumed. Ricardo-Silva et al.⁸⁷ found R. pictipes and its congeneric R. robustus in A. maripa palm trees throughout the Pará state of Brazil, where acute Chagas cases appear to be increasing, some of which are suspected to be oral transmission cases.⁸⁹ While many oral Chagas cases in this region are linked with consumption of juice from the fruit of the acai palm,⁸⁹ Ricardo-Silva et al.⁸⁷ suggested that the palm fruits of A. maripa may also be of interest due to the way in which the fruits are harvested. Considering that the same vector species, palm species and palm fruit consumption habits are found in Trinidad, we believe that R. pictipes and A. maripa in Trinidad merit further investigation.

Figure 7.

E. mucronatus. (Top) Only existing image of specimens from Trinidad. Shown are two adults and a nymph. Photo from Omaj-Maharaj.⁹⁵ (Bottom) Colour photo of an adult male from the Amazonas state in Brazil. Photo from Souza et al.⁸²

In Trinidad, R. pictipes is the second most common species found in and around human homes, after P. geniculatus, and it is the only other triatomine species found infected with T. cruzi in Trinidad^30,69,83 (although this is likely due to sampling bias, detailed below). Studies of R. pictipes feeding profiles outside of Trinidad revealed that it feeds on opossums, birds, rodents, horses, haemolymph and humans.^87,90 The breeding habitat of R. pictipes in Trinidad is unclear; searches of palm trees in Trinidad have not yet yielded specimens.^69,83 Studies of the ecology and feeding behaviour of R. pictipes in Trinidad are needed to clarify its epidemiological importance.

1981: P. rufotuberculatus

The sixth triatomine species to be described in Trinidad was P. rufotuberculatus. Two specimens were discovered on the walls of a radio transmission station in Blanchisseuse, Trinidad in 1981 by Indira Omah-Maharaj,⁹¹ then a doctoral student at the University of the West Indies. P. rufotuberculatus has a large geographic range, spanning from Mexico to Argentina, although a recent study has discovered that specimens in Bolivia that were initially thought to be P. rufotuberculatus were actually a unique species.⁹²  P. rufotuberculatus is a medium-sized species, measuring 24–28 mm in length. Its coloration is mostly brown tones and it has a distinct pattern on its connexival segments (i.e. the edge of the lower two-thirds of its body) consisting of dark, angular hourglass shapes surrounded by a dark transverse stripe on either side (Figure 8). Similar to R. pictipes and E. mucronatus, P. rufotuberculatus is primarily sylvatic with a tendency to invade human households in some parts of its range.^60,93 No other specimens of P. rufotuberculatus have been found in Trinidad since the initial collection, and its epidemiological importance is considered low.

Figure 8.

One of the two P. rufotuberculatus specimens collected in Trinidad. Specimen is an adult male. Photo from Omaj-Maharaj.⁹⁵

Triatomine vectors in Tobago

There are no published scientific records of triatomines on the island of Tobago. However, members of our research group have collected two of the six species found in Trinidad (P. geniculatus and R. pictipes) in Tobago. In addition, citizen science reports of the same two species on Tobago exist, but a full entomological survey of triatomine species on Tobago is needed.

T. cruzi infection in triatomine bugs

All six triatomine species in Trinidad are competent hosts of T. cruzi. Infected specimens have been recorded as close as Venezuela,³³ but in Trinidad T. cruzi has been found only in P. geniculatus and R. pictipes. The lack of T. cruzi infection in the other four species is likely due to sampling bias and the years in which the studies were conducted (Table 2). T. rubrofasciata and M. trinidadensis specimens from Trinidad have never been examined for T. cruzi, and as mentioned above, only two specimens of P. rufotuberculatus were ever collected on the island.^{30,32,69,83,91} In contrast, hundreds of P. geniculatus specimens have been collected and examined for T. cruzi in Trinidad. Additionally, all studies of triatomine bugs in Trinidad except Hylton et al.⁶⁹ were conducted prior to the advent of DNA-based T. cruzi detection methods, namely polymerase chain reaction (PCR), which are more sensitive for detecting T. cruzi infection in starved field-caught bugs with low parasite loads. Vector specimens from Tobago have not yet been tested for T. cruzi infection.

Colony-reared triatomines

Colonies of P. geniculatus, R. pictipes and possibly E. mucronatus were reared at the TRVL in the 1970s (which became the Caribbean Epidemiological Center in 1975) and maintained for 16 y.^94–97 The colonies were used to study the life cycle and development of the three species at different temperatures and humidities. Unfortunately, we could not locate any peer-reviewed publications reporting the results from these studies. Some results from the P. geniculatus colonies are reported in the doctoral thesis of Omah-Maharaj,⁹⁵ where she reported the lifespan in the colony ranging from 35–149 d and females laying between 8 to 395 eggs. The reported lifespan is short relative to other studies of P. geniculatus, possibly an effect of rearing conditions.⁹⁸

Collection methods for triatomine bugs

Collecting triatomine bugs is labour intensive, as the bugs inhabit a wide range of habitats, are often well-camouflaged, can flatten their bodies to hide in the smallest of crevices and in many cases are not abundant in any single location. Many sampling methods have been employed to capture triatomines throughout their range, none of which are perfect, although animal-baited traps are known to be relatively effective if the exact habitat (e.g. vegetation identified down to species, such as Attalea butyracea and Rhodnius pallescens⁹⁹) is known. When the exact microhabitat location within a site is not known, different methods must be trialled, which is what was done in the three projects collecting triatomines in Trinidad.^30,69,83 In these studies, Omah-Maharaj^83,91 used light traps and intensive manual searching in microhabitats such as caves, burrows, nests and trees, which yielded a total of 148 bugs over 3 y of sporadic collecting (the number of collection days is not given). Hylton et al.⁶⁹ was the only study to use mouse-baited traps, which were placed in or near potential vector microhabitats (e.g. palm trees, animal nests etc.) and also placed near artificial lights in rural residential areas. These traps, all placed near artificial lights, yielded five specimens over the course of 2 weeks of sampling.

Observations on triatomine bug phenology in Trinidad based mostly on P. geniculatus collection suggest that triatomines are most abundant (and presumably active) under conditions of low humidity, reduced rainfall and during the new moon.³² Omah-Maharaj^83,95 also noted the greatest collection success in the dry season, from January to May, and during 20:00–23:00 h. Hylton et al.⁶⁹ sampled during the rainy season, which may have contributed to the absence of bugs captured using mouse-baited traps placed in palm trees and animal nests.

Both Fistein and Hylton et al. employed citizen science approaches where community members were provided with instructions and materials for safely capturing bugs seen in their homes and asked to submit any bugs captured.^30,32,69,100 Although Fistein offered a monetary reward for community-captured specimens while Hylton et al. did not, both approaches yielded several contributions. Regardless of the methodological differences, as well as substantial lengths of time (i.e. decades) between the three studies of triatomines in Trinidad, all studies yielded similar results. The predominant triatomine species collected was P. geniculatus, with small numbers of R. pictipes and few, if any, of the other four species. Additionally, most bugs collected were adults, with nymphs found mainly in caves and within armadillo nests.

Animal hosts of T. cruzi

The first discovery of T. cruzi in Trinidad occurred in a wild animal. Researchers at the TRVL stumbled upon the parasite in 1958 while examining in the serum of a Norway rat (Rattus rattus) during arbovirus surveillance activities.¹⁰¹ Thirty years later, in 1981, Omah-Maharaj⁸³ conducted the first investigation of T. cruzi in Trinidad as part of a larger study on Chagas disease ecology in the island. Omah-Maharaj identified opossum species, Didelphis marsupialis and the nine-banded armadillo (Dasypus novemcinctus) as T. cruzi reservoir hosts in Trinidad. Hylton et al.⁶⁹ identified 10 wildlife species in a blood meal analysis of 53 P. geniculatus collected in Trinidad in 2016 but did not find armadillo or Didelphis opossum (Table 3). The lack of these species in the analysis may be an effect of the small number of bugs in the study and/or the types of collection locations, which were all in or around human homes, whereas Omah-Maharaj collected in forests. In addition, armadillo populations are declining in Trinidad due to overhunting,^44,102 which could also explain this result. Researchers from the Basic Veterinary Sciences Department at the University of the West Indies recently detected trypanosomes in the blood of two armadillos caught by hunters in the Charuma Forest of Trinidad, and two P. geniculatus nymphs were found in the armadillos’ nest. One of the nymphs had T. cruzi in its excrement, confirming that armadillos do still play a role in the vector-borne T. cruzi transmission cycle in Trinidad (R. Suepaul 2022, personal observation). However, the extent of the armadillo's role as a primary T. cruzi reservoir in Trinidad needs to be formally studied.

Although formal studies of T. cruzi in domestic animals in Trinidad are scarce, we know that T. cruzi infects canines, as we have records documenting at least 14 cases of T. cruzi–infected canines in the pathology unit within the University of the West Indies School of Veterinary Medicine since 2008 (described in detail in Suepaul et al. 2025, submitted manuscript). Cases seem to be common in dogs used for hunting or housed in outdoor kennels near forested areas. Dogs are used as sentinels for T. cruzi transmission in other Chagas-endemic regions,^103,104 which could be a useful surveillance approach in TT. Additionally, Hylton et al.⁶⁹ found the domestic chicken to be a common food source for P. geniculatus in Trinidad. While avian hosts are refractory to T. cruzi infection (although, some challenge this notion¹⁰⁵), they do serve as food sources that maintain vector populations in peridomestic environments and potentially attract vectors to residential areas.

Chagas disease epidemiology

Evidence of T. cruzi infection in humans in Trinidad dates back to the early 1960s, when, shortly after the discovery of T. cruzi in a Norway rat captured on the island, cardiologist Boris Fistein began to investigate locally acquired Chagas disease. Fistein serologically tested four of his patients for T. cruzi antibodies who had congestive heart failure of unknown aetiology.¹⁰⁶ Three of the four patients were seropositive, prompting Fistein to carry out a larger serosurvey on 100 heart failure patients who were consecutively admitted to the Port of Spain General Hospital.³² Of these 100 patients, 6 were seropositive. Fistein subsequently discovered hundreds of T. cruzi–infected triatomine bugs in the homes of the seropositive patients from both studies (Table 4).^30,32 In an attempt to estimate national prevalence, Fistein tested 1323 blood samples submitted to a venereal disease clinic and found a seroprevalence of 0.45%.³² Three other small serosurveys on different populations were undertaken nearly 30 y later, with variable prevalences ranging from 0 to 37%. Many of the studies were carried out in cardiac patients or patients considered ‘at risk’ due to their hobbies or occupation, so there are few estimates of what the national prevalence may be (Table 4).^31,107,108 The last T. cruzi serosurvey carried out in Trinidad was in 1996.¹⁰⁸

Table 4.

Serological survey results for T. cruzi in Trinidad and Tobago.

Year	Population	N	Screened positive n (%)	Confirmed positive, n (%)	Diagnostic method	Notes
196389	Patients with congestive heart failure with obscure aetiology	4	NA	3 (75)	CFT	Most patients lived in isolated houses in small rural villages in the bush, some distance from the paved road
196589	Patients who were consecutively admitted to the Port of Spain General Hospital for heart failure	100	NA	6 (6)	CFT	79 triatomine bugs (51% infected with T. cruzi) collected from houses of positive patients and their neighbours; CFT tests on 51 relatives and neighbours of the serologically positive patients, yielded one weakly positive result
196524	Sera samples obtained from the Venereal Disease Diagnostic Service	1323		6 (0.45)	CFT	Aim was to estimate national prevalence
1978–8023	Filariasis survey of Blanchisseuse residents	452	NA	0	IFA, IHA
1980s23	Blood bank samples from individuals exhibiting cardiac symptoms conforming to Chagas disease (n=40) and hunters (n=5)	45	NA	0	IFA
1980s23	Samples submitted to the Caribbean Epidemiology Center specifically for Chagas disease screening	15	NA	1 (6.7)	IFA
199390	Cardiac patients seen at the San Fernando General Hospital	192	72 (37.5)	49 (25.5)	ELISA, blood smear examination of seropositive samples	The authors report that T. cruzi trypomastigotes were detected in the peripheral blood of 49 of the 72 patients who were serologically positive. Parasitaemia is not usually detectable visually in the blood of patients in the chronic stage, so these results have drawn scepticism
199491	Oil field workers (n=32), hunters (n=28), unspecified ‘at-risk’ patients (n=20)	80	3 (3.7)	1 (1.3)	Screening: IHA Confirmation: ELISA	Two of three screened positive from oil field workers group; confirmed positive was from the ‘at-risk’ patients group
199491	Cardiac clinic patients in San Fernando	247	16 (6.5)	5 (2.0)	Screening: IHA Confirmation: ELISA
1994–199691	Blood bank donors	397	5 (1.3)	0	Screening: IHA Confirmation: ELISA	Samples collected from six blood collection sites throughout Trinidad and Tobago; data reported as if two IHAs were performed, but this is not specified
1994–199691	Cardiologist routine samples taken from same patients in 1994, 1995 and 1996	1994: 47	1994: 3 (6.4)	1994: 2 (4.3)	ELISA	Data suggest that samples positive in two ELISAs considered positive, but this is not stated
		1995: 39	1995: 2 (5.1)	1995: 2 (5.1)
		1996: 20	1996: 6 (30)	1996: 5 (25)

CFT: complement fixation test; IFA: indirect immunofluorescence assay; IHA: indirect haemagglutination assay; ELISA: enzyme-linked immunosorbent assay.

The Fistein studies from the 1960s are still the most comprehensive human Chagas disease studies conducted in Trinidad. The only current human T. cruzi infection data for TT come from blood banks that screen their blood samples for T. cruzi markers, although there is no system in place to notify people whose samples are identified as T. cruzi positive. As part of their annual member state blood transfusion report, the PAHO publishes the annual percentage of blood bank samples per country that tested positive for blood-borne pathogens, including T. cruzi. In the years 2016–2020 (T. cruzi data for TT were not included in the earlier reports we reviewed), the average reported T. cruzi blood bank prevalence for TT was 0.275%, with the rate steadily increasing each year (Table 5). In 2020, TT reported that 0.5% of blood bank samples were seropositive for T. cruzi, which was higher than in 13 of the 19 countries that have ‘Chagas-endemic’ status (Table 6). In other words, since 2016, the proportion of T. cruzi seropositive blood bank samples in TT has been consistently equal to or greater than more than half of the countries that are considered as Chagas endemic by the PAHO (Table 6).^36,37 If the average TT blood bank prevalence for the years 2016–2020 (0.275%) is applied to the population size of 1.4 million people, we would expect around 38 500 people in TT to be infected with T. cruzi. However, blood bank prevalence is not an accurate indicator of true prevalence, and a national Chagas disease serosurvey is needed in Trinidad and Tobago to determine if active transmission of T. cruzi is occurring and to provide strong evidence that the country should be given a Chagas-endemic designation from global public health agencies such as the PAHO and the WHO.

Table 5.

T. cruzi blood bank prevalence in Trinidad and Tobago since 2016.^25,26 Data for 2018 were not available.

Year	T. cruzi positive, %
2016	0.06
2017	0.24
2019	0.30
2020	0.50
Average	0.275

Table 6.

Average T. cruzi blood bank seroprevalence from 2016 to 2020 for all countries considered to be Chagas endemic, except for TT, which is not considered endemic.^25,26

Country	Average blood bank prevalence (%), 2016–2020
El Salvador	2.24
Bolivia	1.79
Paraguay	1.66
Argentina	1.63
Guyana	0.84
Honduras	0.69
Guatemala	0.63
Peru	0.34
Mexico	0.33
Ecuador	0.32
Venezuela	0.30
Trinidad and Tobago	0.275
Nicaragua	0.25
Belize	0.20
Panama	0.19
Brazil	0.19
Colombia	0.18
Costa Rica	0.14
Uruguay	0.14
Chile	0.07

Additionally, in 2019, the TT Ministry of Health initiated blood smear examinations for individuals who reported being bitten by a triatomine bug (time of bite not specified), although this is not yet an official activity. In this process, blood is obtained by the Ministry of Health and sent to the University of the West Indies School of Veterinary Medicine for examination by parasitologists and pathologists for T. cruzi and Plasmodium parasites. Eleven blood smears were examined between 2019 and 2022, with no T. cruzi forms observed (R. Suepaul 2022, personal observation). This was a step in the right direction, although blood parasitaemia would be effective only for examining people recently infected and complementary serological testing is necessary to detect chronic Chagas disease cases.

Chagas disease risk: vulnerable populations

Chagas disease has historically been connected to rural poverty, poor housing conditions, subsistence economies and underserved communities.^109,110 In Trinidad, despite its relatively high level of industrialization among other Caribbean islands, thousands of people are unable to afford suitable housing. According to the Land Settlement Agency of the government of TT, there are an estimated 250 squatter settlements on state lands comprising 23 000 households, and other estimates are much higher.¹¹¹ These populations often reside in rural and forested areas, living in substandard housing constructed with cheaper materials. During the time in which Omah-Maharaj⁸³ conducted her study (1982–85), wooden houses with galvanized iron roofs were common in rural Trinidad, and these structures may not have been conducive to triatomine bug infestation.¹¹² Recently however, there has been a shift toward rural house construction using materials that may provide suitable habitat for triatomine bugs, such as plywood and unrendered clay blocks. In continental Latin America, typical domestic habitats for triatomine bugs are houses with thatched roofs, mud walls, junk piles and other materials with crevices suitable for small invertebrate shelters.^12,113 In Trinidad, the combination of poor infrastructure and forested areas may increase the likelihood of domiciliary triatomine bug invasion or infestation.

Hunting is a cultural practice in TT that puts participants at higher risk of T. cruzi transmission. Hunters and their dogs sleep in the forest for days at a time, providing an opportunity for interaction with T. cruzi–infected bugs. Hunters also handle carcasses of competent T. cruzi hosts, such as armadillo, opossum and agouti, potentially exposing themselves to T. cruzi in animal blood.^13,15

Better conservation and management of natural resources in Trinidad could lower this risk, including more stringent hunting regulations and enforcement; currently, 10 000 hunters register annually for permits in TT, and there are an estimated 30 000 hunting dogs in Trinidad.⁴⁴

Hunting, deforestation and other environmental degradation in TT is altering the balance of mammalian host species, likely resulting in shifts in both T. cruzi and triatomine bug geographic distributions. Combined with climate change, these factors could contribute to vector range expansion and possibly increased disease transmission.^114–117 Baseline knowledge on triatomine vector species in TT, including vector distribution, biotic and abiotic factors, determinants of vector presence (e.g. temperature, seasonality, annual precipitation, vegetation etc.¹¹⁸) and T. cruzi prevalence in host species, is needed to better predict and prepare for the effects of climate change and other human drivers of disease on T. cruzi distribution in TT.

The way forward

Chagas disease sits at the human–animal–environment interface, necessitating a One Health approach for detection, control and prevention of disease spread. The One Health approach to disease control acknowledges the interconnectedness of disease transmission among host types (animals, humans, vectors) and the environment.¹¹⁹ For this reason, the One Health approach is increasingly applied to the management, control and even elimination of zoonotic and vector-borne diseases due to their multihost transmission dynamics across multiple landscape types.¹²⁰ TT, through the University of the West Indies–implemented ‘One Health One Caribbean One Love’ project, has promoted the use of a One Health approach to address complex health issues at the interface between human, animal and environmental health, such as Chagas disease.¹²¹

Practically, a One Health approach resembles ecological approaches to reduce Chagas disease that have been successfully implemented in Costa Rica,¹²² Guatemala¹²³ and Argentina.¹¹⁰ Regardless of the nomenclature, the basis of these approaches are community engagement in the development of control measures that target human, animal, vector and environmental aspects of disease transmission. These measures are geared towards health promotion and community mobilization in close cooperation with community leaders from affected areas.^110,122,123

In TT, a One Health approach to Chagas disease will require synergistic efforts from professionals in public health, forestry, ecology and veterinary studies and community leaders to develop and implement sustainable strategies to combat Chagas disease transmission. Research should prioritize P. geniculatus and clarify the epidemiological importance of R. pictipes and E. mucronatus. A systematic entomological survey of triatomine bugs, domestic animals and wildlife is needed not only in Trinidad, but also on the island of Tobago to understand the extent to which the vector is making contact with humans and their animals, both domestic and synanthropic. Nationwide, a human serosurvey to estimate the true national prevalence of T. cruzi infection would help to draw attention to the disease on the island, especially from public health agencies that can assist in obtaining donations of diagnostic and treatment resources. Finally, a public health campaign to raise awareness of the disease in TT, particularly among medical and veterinary health professionals, would be a critical next step to address Chagas disease in Trinidad.

Conclusions

Although investigations of Chagas disease in Trinidad are sparse, they collectively send a clear message: the components of vector-borne Chagas disease are in place on the island. T. cruzi has been found numerous times infecting humans and animals, and T. cruzi–infected vectors continue to be found in areas of human activity, including the homes where individuals with T. cruzi–positive serology reside. A comprehensive, One Health study of Chagas disease in TT is urgently needed in combination with community-based public health interventions promoting awareness of and education on Chagas disease in TT. This strategy will empower community members with information to protect themselves from Chagas disease and its vectors and, in turn, increase public health preparedness in TT.

Authors’ contributions

RS, AM and JKP designed the study and developed the study protocol. RS and JKP reviewed all materials consulted for this manuscript and wrote the first draft of the manuscript. AM, NLG, CO, AR, VT and RK critically reviewed and edited the manuscript. All authors read and approved the final manuscript.

Funding

None.

Competing interests

None declared.

Ethical approval

Not required.

Data availability

No new data were generated in this study.