Abundant triatomines in Texas dog kennel environments: Triatomine collections, infection with Trypanosoma cruzi, and blood feeding hosts

Triatomine insects are vectors of the protozoan parasite Trypanosoma cruzi- the causative agent of Chagas disease. Chagas disease is endemic to Latin America and the southern United States and can cause severe cardiac damage in infected mammals, ranging from chronic disease to sudden death. Identifying interactions among triatomines, T. cruzi discrete typing units (DTUs), and blood feeding hosts is necessary to understand parasite transmission dynamics and effectively protect animal and human health. Through manual insect trapping efforts, kennel staff collections, and with the help of a trained scent detection dog, we collected triatomines from 10 multi-dog kennels across central and south Texas over a one-year period (2018-2019) and tested a subset to determine their T. cruzi infection status and identify the primary bloodmeal hosts. We collected 550 triatomines, including Triatoma gerstaeckeri (n = 515), Triatoma lecticularia (n = 15), Triatoma sanguisuga (n = 6), and Triatoma indictiva (n = 2), with an additional 10 nymphs and 2 adults unable to be identified to species. The trained dog collected 42 triatomines, including nymphs, from areas not previously considered vector habitat by the kennel owners. Using qPCR, we found a T. cruzi infection prevalence of 47 % (74/157), with T. lecticularia individuals more likely to be infected with T. cruzi than other species. Infected insects harbored two T. cruzi discrete typing units: TcI (64 %), TcIV (23 %), and mixed TcI/TcIV infections (13 %). Bloodmeal host identification was successful in 50/149 triatomines, revealing the majority (74 %) fed on a dog (Canis lupus), with other host species including humans (Homo sapiens), raccoons (Procyon lotor), chickens (Gallus gallus), wild pig (Sus scrofa), black vulture (Coragyps atratus), cat (Felis catus), and curve-billed thrasher (Toxostoma curviostre). Given the frequency of interactions between dogs and infected triatomines in these kennel environments, dogs may be an apt target for future vector control and T. cruzi intervention efforts.

Trypanosoma cruzi Genotype I and Toxoplasma gondii Co-infection in a Red-Necked Wallaby

While the health effects of trypanosomes in Australian mammals in their native range are not fully understood, there is evidence of an impact in those species introduced to other geographical regions. Here we report the pathological and molecular features of concurrent fatal trypanosomiasis and toxoplasmosis in an adult female captive red-necked wallaby (syn. Bennett's wallaby; Macropus rufogriseus) from Bee County, Texas, USA. The animal exhibited no clinical signs prior to sudden death. On necropsy, the main findings were generalized organ congestion and bilateral renal petechiation. Microscopically, the main finding was lymphohistiocytic and necrotizing pancarditis with intrasarcoplasmic protozoal pseudocysts containing amastigotes and occasional intrahistiocytic amastigotes, morphologically compatible with Trypanosoma cruzi, as well as rare intrasarcoplasmic protozoal tissue cysts with zoites morphologically compatible with Toxoplasma gondii. Other lesions included acute centrilobular to panlobular necrotizing hepatitis with intrahepatocellular T. gondii cysts, necrotizing splenitis, pulmonary oedema with fibrin, histiocytosis and rare fibrin microthrombi, and acute renal tubular degeneration with proteinosis and pigmented casts suggestive of haemoglobinuria or myoglobinuria. Immunohistochemical labelling confirmed intralesional T. gondii cysts and molecular analyses identified T. cruzi genotype I and T. gondii. This is a unique case that, to the best of our knowledge, represents the first description of T. cruzi and T. gondii co-infection, as well as the first record of naturally occurring infection T. cruzi genotype I infection in macropodids. This case adds to the epidemiological knowledge on Chagas disease in the USA, particularly in Texas where there is a high prevalence of human and canine trypanosomiasis.

Trypanosoma cruzi discrete typing unit TcIV implicated in a case of acute disseminated canine Chagas disease

In 2006, Nabity et al. reported on an atypical presentation of Trypanosoma cruzi (T. cruzi) infection in an 8-month old English Mastiff from central Texas. Clinical signs and laboratory findings included lymphadenopathy, weight loss, amastigotes in lymph node aspirates, and initial serological results suggestive of either T. cruzi or Leishmania infection. Given the poor prognosis, the dog was euthanized and subsequent testing and culture of parasites from a lymph node revealed T. cruzi infection. Because different parasite discrete typing units (DTUs) are potentially associated with different disease outcomes in a variety of mammalian hosts, an understanding of these relationships in naturally infected dogs may be useful for informing canine prognosis and may also have human health implications. Here, we compared strains using culture versus culture-independent methods. We subjected archived cultured parasites harvested from the lymph node in the infected Mastiff to two independent approaches for determining parasite DTU, including sequencing of the TcSC5D gene and use of DTU-specific qPCR probes to hybridize the nuclear spliced leader intergenic region (SL-IR). Both approaches revealed T. cruzi discrete typing unit TcIV. Testing of multiple other tissues directly without culturing, including heart/tongue, intestine, trachea/lymph nodes, and uterus/ovary, provided further evidence of disseminated TcIV infection in this dog. We report T. cruzi DTU TcIV as the cause of a severe disseminated infection in a dog from an area with triatomine vectors in central Texas, adding to the limited body of clinicopathologic data that links specific parasite strains to disease outcomes in dogs in the US. Future studies to type parasites from asymptomatic dogs and those with diverse disease manifestations will be useful in informing the degree to which parasite genetics is associated with disease presentation and severity. If applied to antemortem samples, diagnostic typing of parasites from infected dogs may assist in determining prognosis.

Simulation of climate-tick-host-landscape interactions: Effects of shifts in the seasonality of host population fluctuations on tick densities

Tick vector systems are comprised of complex climate-tick-host-landscape interactions that are difficult to identify and estimate from empirical observations alone. We developed a spatially-explicit, individual-based model, parameterized to represent ecological conditions typical of the south-central United States, to examine effects of shifts in the seasonal occurrence of fluctuations of host densities on tick densities. Simulated shifts in the seasonal occurrence of periods of high and low host densities affected both the magnitude of unfed tick densities and the seasonality of tick development. When shifting the seasonal densities of all size classes of hosts (small, medium, and large) synchronously, densities of nymphs were affected more by smaller shifts away from the baseline host seasonality than were densities of larval and adult life stages. When shifting the seasonal densities of only a single size-class of hosts while holding other size classes at their baseline levels, densities of larval, nymph, and adult life stages responded differently. Shifting seasonal densities of any single host-class earlier resulted in a greater increase in adult tick density than when seasonal densities of all host classes were shifted earlier simultaneously. The mean densities of tick life stages associated with shifts in host densities resulted from system-level interactions of host availability with tick phenology. For example, shifting the seasonality of all hosts ten weeks earlier resulted in an approximately 30% increase in the relative degree of temporal co-occurrence of actively host-seeking ticks and hosts compared to baseline, whereas shifting the seasonality of all hosts ten weeks later resulted in an approximately 70% decrease compared to baseline. Differences among scenarios in the overall presence of active host-seeking ticks in the system were due primarily to the degree of co-occurrence of periods of high densities of unfed ticks and periods of high densities of hosts.

Borrelia burgdorferi not detected in widespread Ixodes scapularis (Acari: Ixodidae) collected from white-tailed deer in Tennessee

Lyme disease (LD), caused by the bacterium Borrelia burgdorferi and transmitted in the eastern United States by blacklegged ticks, Ixodes scapularis Say, is classified as nonendemic in Tennessee and surrounding states in the Southeast. Low incidence of LD in these states has been attributed, in part, to vector ticks being scarce or absent; however, tick survey data for many counties are incomplete or out of date. To improve our knowledge of the distribution, abundance, and Borrelia spp. prevalence of I. scapularis, we collected ticks from 1,018 hunter-harvested white-tailed deer (Odocoileus virginianus (Zimmerman)) from 71 of 95 Tennessee counties in fall 2007 and 2008. In total, 160 deer (15.7%) from 35 counties were infested with adult I. scapularis; 30 of these counties were new distributional records for this tick. The mean number of I. scapularis collected per infested deer was 5.4 +/- 0.6 SE. Of the 883 I. scapularis we removed from deer, none were positive for B. burgdorferi and one tested positive for B. miyamotoi. Deer are not reservoir hosts for B. burgdorferi; nevertheless, past surveys in northern LD-endemic states have readily detected B. burgdoreferi in ticks collected from deer. We conclude that I. scapularis is far more widespread in Tennessee than previously reported. The absence of detectable B. burgdorferi infection among these ticks suggests that the LD risk posed by I. scapularis in the surveyed areas of Tennessee is much lower than in LD-endemic areas of the Northeast and upper Midwest.

High-prevalence Borrelia miyamotoi infection among [corrected] wild turkeys (Meleagris gallopavo) in Tennessee

During spring and fall 2009, 60 wild turkeys (Meleagris gallopavo) harvested by Tennessee hunters were surveyed for Borrelia spp. by sampling their blood, tissue, and attached ticks. In both seasons, 70% of turkeys were infested with juvenile Amblyomma americanum; one spring turkey hosted an adult female Ixodes brunneus. Polymerase chain reaction assays followed by DNA sequencing indicated that 58% of the turkeys were positive for the spirochete Borrelia miyamotoi, with tissue testing positive more frequently than blood (P = 0.015). Sequencing of the 16S-23S rRNA intergenic spacer indicated > or = 99% similarity to previously published sequences of the North American strain of this spirochete. Positive turkeys were present in both seasons and from all seven middle Tennessee counties sampled. No ticks from the turkeys tested positive for any Borrelia spp. This is the first report of B. miyamotoi in birds; the transmission pathways and epidemiological significance of this high-prevalence spirochetal infection remain uncertain.

Development of computerized storage facilities for twin data: a relational database system for a twin register

Many twin registers hold information on flat file systems such as those provided by statistical packages or spreadsheets. Demographic details may be maintained separately from data collected in multiple different studies, leading to considerable problems with data consistency, redundancy, and integration. Ad hoc requests may be difficult. Implementation of a relational database system permits storage and maintenance of all records, simple data entry and validation procedures, linking of information from different projects with security of access, and the flexibility to provide rapid answers to ad hoc enquiries using standard Structured Query Language (SQL). Twin data provide a challenge for relational database design which rests on the technique of normalization and the use of unique identifiers to access associated groups of variables; for twins, "uniqueness" must preserve identification of both the pair and the individual twin subjects in the data structure to enable flexible access to and analysis of the data. An application on the Institute of Psychiatry Volunteer Twin Register (IOPVTR) database is described, through reference to one study of a sample of the twins, with simulated data. We show how a balance of adherence to database design principles and attention to ongoing clerical and research procedures has been used to produce an integrated, flexible, and open-ended system.