Correlation between presence of Trypanosoma cruzi DNA in heart tissue of baboons and cynomolgus monkeys, and lymphocytic myocarditis

Exclusion of Horizontal and Vertical Transmission as Major Sources of Trypanosoma Cruzi Infections in a Breeding Colony of Rhesus Macaques (Macaca Mulatta)

The vector-borne protozoal parasite Trypanosoma cruzi causes Chagas disease in humans and animals. This parasite is endemic to the southern United States where outdoor-housed NHP at biomedical facilities are at risk of infection. In addi- tion to the direct morbidity caused by T. cruzi, infected animals are of limited biomedical research use because infections can produce confounding pathophysiologic changes even in animals with no clinical disease. In part due to concerns for direct T. cruzi transmission between animals, infected NHP at some institutions have been culled, removed, or otherwise isolated from uninfected animal populations. However, data that document horizontal or vertical transmission in captive NHP in the United States are not available. To evaluate the potential for inter-animal transmission and to identify environmental factors that affect the distribution of new infections in NHPs, we conducted a retrospective epidemiologic study of a rhesus macaque ( Macaca mulatta ) breeding colony in south Texas. We used archived biologic samples and husbandry records to identify the time and location of macaque seroconversion. These data were used to perform a spatial analysis of how geographic location and animal associations affected the spread of disease and to infer the importance of horizontal or vertical routes of transmission. The majority of T. cruzi infections were spatially clustered, suggesting that environmental factors promoted vector exposure in various areas of the facility. Although we cannot not rule out horizontal transmission, our data suggest that horizontal transmission was not a critical route for spread for the disease. Vertical transmission was not a contributing factor in this colony. In conclusion, our findings suggest that local triatome vectors were the major source of T. cruzi infections in captive macaques in our colony. Therefore, limiting contact with vectors, rather than segregation of infected macaques, is a key strategy for disease prevention at institutions that house macaques outdoors in the southern United States.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Non-proliferative and Proliferative Lesions of the Non-human Primate (M. fascicularis)

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the nonhuman primate used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Locally Transmitted Trypanosoma cruzi in a Domestic Llama (Lama glama) in a Rural Area of Greater New Orleans, Louisiana, USA

Trypanosoma cruzi-associated megaesophagus was diagnosed in a domestic Louisiana-born llama with no significant travel history. The llama resided in the same rural area of greater New Orleans, Louisiana, where the first human autochthonous case of Chagas disease was identified in the state. Venous blood from the llama tested positive for T. cruzi kinetoplastid DNA by conventional PCR. The cardiac evaluation was unremarkable, while thoracic radiographs revealed generalized megaesophagus. The llama received supportive care, but was ultimately humanely euthanized. The esophagus was severely distended throughout its length on necropsy, and histologic evaluation showed no microscopic changes in esophageal tissue and minimal to mild lymphoplasmacytic inflammation in cardiac tissue. T. cruzi DNA was detected by conventional PCR in the esophagus, small intestine, and blood despite no protozoan organisms being observed in multiple tissue sections examined. This report contributes to the growing body of evidence of local transmission of T. cruzi in the southern United States, and Chagas disease should be considered a differential diagnosis when evaluating llamas and other large animal species for esophageal dysfunction. There is little research describing megaesophagus or Chagas disease in llamas, and this report aims to increase awareness about this zoonotic disease that is becoming more frequently reported in the southern United States.

Emerging agents for the treatment of Chagas disease: what is in the preclinical and clinical development pipeline?

INTRODUCTION

Chagas disease treatment relies on the lengthy administration of benznidazole and/or nifurtimox, which have frequent toxicity associated. The disease, caused by the parasite Trypanosoma cruzi, is mostly diagnosed at its chronic phase when life-threatening symptomatology manifest in approximately 30% of those infected. Considering that both available drugs have variable efficacy by then, and there are over 6 million people infected, there is a pressing need to find safer, more efficacious drugs.

AREAS COVERED

We provide an updated view of the path to achieve the aforementioned goal. From state-of-the-art in vitro and in vivo assays based on genetically engineered parasites that have allowed high throughput screenings of large chemical collections, to the unfulfilled requirement of having treatment-response biomarkers for the clinical evaluation of drugs. In between, we describe the most promising pre-clinical hits and the landscape of clinical trials with new drugs or new regimens of existing ones. Moreover, the use of monkey models to reduce the pre-clinical to clinical attrition rate is discussed.

EXPERT OPINION

In addition to the necessary research on new drugs and much awaited biomarkers of treatment efficacy, a key step will be to generalize access to diagnosis and treatment and maximize efforts to impede transmission.

Reproductive Outcomes in Rhesus Macaques (Macaca mulatta) with Naturally-acquired Trypanosoma cruzi Infection

Chagas disease is a zoonotic vector-borne disease caused by infection with the protozoan parasite Trypanosoma cruzi. T. cruzi is found in Latin America and the Southern United States, where it infects many species, including humans and nonhuman primates (NHPs). NHPs are susceptible to natural infection and can develop clinical symptoms consistent with human disease, including Chagasic cardiomyopathy, gastrointestinal disease and transplacental transmission, leading to congenital infection. Due to evidence of Chagas transmission in Texas, this study hypothesized T. cruzi infection was present in a closed, outdoor-housed breeding colony of rhesus macaques (Macaca mulatta) located at a biomedical research facility in Central Texas. In addition, we questioned whether seropositive female rhesus macaques might experience reproductive complications consistent with maternal-fetal Chagas disease. The seroprevalence of T. cruzi infection in the colony was assessed using an Enzyme Linked Immunosorbant Assay (ELISA) to detect antibodies against Tc24 antigen as a screening assay, and a commercially available immunochromatographic test (Chagas Stat Pak) as a confirmatory assay. Retrospective serologic analysis was performed to confirm the status of all T. cruzi-infected animals between the years 2012 to 2016. The medical history of all seropositive and seronegative breeding females within the colony from 2012 to 2016 was reviewed to determine each animals' level of reproductive fitness. The percentage of T. cruzi-seropositive animals ranged from 6.7% to 9.7% in adult animals and 0% to 0.44% in juveniles or weanling animals, depending on the year. An overall 3.9% seroprevalence of T. cruzi infection was found in the total population. No significant differences in any measure of reproductive outcomes were identified between seropositive and seronegative females from 2012 to 2016. The lack of significant adverse reproductive outcomes reported here may help inform future management decisions regarding seropositive female rhesus macaques within breeding colonies.

In situ hybridization assay for the diagnosis of chagas myocarditis and orchitis in a rhesus macaque (Macaca mulatta): A case report

We present the first documented case of Trypanosoma cruzi-induced orchitis in a rhesus macaque. Additionally, we describe an in situ hybridization-based assay to confirm T. cruzi infection in formalin-fixed tissues.

The Prevalence of Trypanosoma cruzi, the Causal Agent of Chagas Disease, in Texas Rodent Populations

Rodent species were assessed as potential hosts of Trypanosoma cruzi, the etiologic agent of Chagas disease, from five sites throughout Texas in sylvan and disturbed habitats. A total of 592 rodents were captured, resulting in a wide taxonomic representation of 11 genera and 15 species. Heart samples of 543 individuals were successfully analyzed by SybrGreen-based quantitative PCR (qPCR) targeting a 166 bp fragment of satellite DNA of T. cruzi. Eight rodents representing six species from six genera and two families were infected with T. cruzi. This is the first report of T. cruzi in the pygmy mouse (Baiomys taylori) and the white-footed mouse (Peromyscus leucopus) for the USA. All infected rodents were from the southernmost site (Las Palomas Wildlife Management Area). No differences in pathogen prevalence existed between disturbed habitats (5 of 131 tested; 3.8%) and sylvan habitats (3 of 40 tested; 7.5%). Most positives (n = 6, 16% prevalence) were detected in late winter with single positives in both spring (3% prevalence) and fall (1% prevalence). Additionally, 30 Triatoma insects were collected opportunistically from sites in central Texas. Fifty percent of these insects, i.e., 13 T. gerstaeckeri (68%), and two T. lecticularia (100%) were positive for T. cruzi. Comparative sequence analyses of 18S rRNA of samples provided identical results with respect to detection of the presence or absence of T. cruzi and assigned T. cruzi from rodents collected in late winter to lineage TcI. T. cruzi from Triatoma sp. and rodents from subsequent collections in spring and fall were different, however, and could not be assigned to other lineages with certainty.

RETROSPECTIVE ANALYSIS OF ADULT-ONSET CARDIAC DISEASE IN FRANÇOIS' LANGURS (TRACHYPITHECUS FRANCOISI) HOUSED IN U.S. ZOOS

Cardiac disease is a common condition in captive primates, and multiple cases in François' langurs ( Trachypithecus francoisi ) were noted on review of the Species Survival Plan studbook. To determine the prevalence of cardiac disease in this species, surveys were distributed to current and previous holding institutions (n = 23) for the U.S. studbook population (n = 216). After exclusion of stillbirths (n = 48), animals less than 1 yr of age (n = 8), and animals housed internationally (n = 2), a study group (n = 158) was identified for this analysis. Robust data was received for 98.7% (n = 156) of the study group and antemortem and postmortem cardiac abnormalities were reported for 25.3% (n = 40) of these animals. Eight animals were reported as medically managed for clinical cardiac disease, and three of these were alive at the time of survey. Six of 11 animals with radiographic cardiac silhouette enlargement antemortem were noted with cardiomegaly on postmortem examination. Of 102 deceased animals in the study group, four were identified with dilated cardiomyopathy, and varying degrees of myocardial fibrosis was observed in 18 animals. Langurs with cardiac fibrosis were found to be significantly older than langurs without cardiac fibrosis (P = 0.003) and more commonly were male (P = 0.036). Screening tests for cardiac disease, such as thoracic radiographs and echocardiography, are recommended to diagnose affected animals earlier, to monitor progression of disease, and to guide treatment, although they should be interpreted with caution because of apparent insensitivity when compared with pathologic results.

Lack of Trypanosoma cruzi Infection in Urban Roof Rats (Rattus rattus) at a Texas Facility Housing Naturally Infected Nonhuman Primates

The protozoan parasite Trypanosoma cruzi causes Chagas disease, uses kissing bugs as a vector, and is maintained in nature by a variety of wildlife reservoirs. Many natural cases of Chagas disease have been reported in NHP at facilities across the southern United States, where infected vectors and wildlife occur. Infection of NHP with T. cruzi can diminish their value as research models and lead to health problems and death. Identifying the modes of transmission and role of wildlife reservoirs in these facilities is therefore critical to guide interventions to reduce transmission. Here we investigated the role of roof rats (Rattus rattus), the most abundant nuisance species at a primate facility in San Antonio, in the maintenance and transmission of T. cruzi. The hearts and blood from the carcasses of the 145 rats collected underwent 2 independent PCR assays for detection of T. cruzi and other trypanosomes. The 145 hearts and 61 blood samples were all negative for T. cruzi. This population sample of 145 subjects would allow the detection of disease prevalence of 0.020 with a confidence level of 95%. The limited active vector surveillance efforts by our team combined with passive surveillance by facility personnel yielded no kissing bugs during the study period. Our results suggest that roof rats are unlikely to be important local reservoirs of T. cruzi at this facility. Further investigation of transmission dynamics across multiple years and more comprehensive vector surveillance is warranted.

Sylvatic Transmission of Trypanosoma cruzi Among Domestic and Wildlife Reservoirs in Texas, USA: A Review of the Historical Literature

Chagas disease (Trypanosoma cruzi infection) is one of the most important neglected tropical diseases affecting the Americas. The transmission dynamic of this parasite is a complicated process that involves three genera of Triatominae subfamily and over 100 known mammalian reservoirs composed of domestic, peridomestic and wildlife species. Understanding the complex relationship between vector species and mammalian hosts is important for preventing transmission to humans. We performed a historical literature review to assess the disease burden in the Texas wildlife and domestic animal population. Reports of sylvatic transmission in Texas date back to the 1940s. We found that up to 23 species can serve as reservoirs for T. cruzi in the state with wood rats, raccoons, and wild and domestic canine species most frequently reported as positive for the parasite. We finish with a discussion of the current research gaps, implications for high-risk populations and future directions for research.

Kissing bugs in the United States: risk for vector-borne disease in humans

Eleven species of kissing bugs are found in the United States. Their home ranges may be expanding northward, perhaps as a consequence of climate change. At least eight of the species, perhaps all, are reported to harbor Trypanosoma cruzi, the parasite that causes Chagas disease. Because humans are encroaching on kissing bug habitat, there is concern for vector-transmitted Chagas disease in the United States. To date, documented autochthonous cases of Chagas in humans in the United States are rare. Kissing bugs are capable of adapting to new habitats such as human domiciles; however, they do not colonize homes in the United States as in Central and South America. We review the biology, behavior, and medical importance of kissing bugs and the risk they pose for transmission of Chagas disease in the United States. Where possible, descriptions of US species are compared to the epidemiologically important Latin American species.