Left ventricular trabeculation in Hominidae: divergence of the human cardiac phenotype.

Although the gross morphology of the heart is conserved across mammals, subtle interspecific variations exist in the cardiac phenotype, which may reflect evolutionary divergence among closely-related species. Here, we compare the left ventricle (LV) across all extant members of the Hominidae taxon, using 2D echocardiography, to gain insight into the evolution of the human heart. We present compelling evidence that the human LV has diverged away from a more trabeculated phenotype present in all other great apes, towards a ventricular wall with proportionally greater compact myocardium, which was corroborated by post-mortem chimpanzee (Pan troglodytes) hearts. Speckle-tracking echocardiographic analyses identified a negative curvilinear relationship between the degree of trabeculation and LV systolic twist, revealing lower rotational mechanics in the trabeculated non-human great ape LV. This divergent evolution of the human heart may have facilitated the augmentation of cardiac output to support the metabolic and thermoregulatory demands of the human ecological niche.

A randomized clinical trial to compare ketamine-butorphanol-azaperone-medetomidine and detomidine-etorphine-acepromazine for anesthesia of captive Przewalski horses (Equus przewalskii).

OBJECTIVE: To compare ketamine-butorphanol-azaperone-medetomidine (KBAM) to detomidine-etorphine-acepromazine (DEA) for field anesthesia in captive Przewalski horses (Equus przewalskii). ANIMALS: 10 adult Przewalski horses. PROCEDURES: A prospective randomized crossover trial was conducted. Each horse was immobilized once with KBAM (200 mg ketamine, 109.2 mg butorphanol, 36.4 mg azaperone, and 43.6 mg medetomidine) and once with DEA (40 mg detomidine premedication, followed 20 minutes later by 3.9 to 4.4 mg etorphine and 16 to 18 mg acepromazine). Both protocols were administered by IM remote dart injection with a washout period of 6 months between treatments. Selected cardiorespiratory variables and quality of anesthesia were recorded. Antagonists were administered IM (KBAM, 215 mg atipamezole and 50 mg naltrexone; DEA, 4 mg RX821002 and 100 mg naltrexone). RESULTS: All horses were anesthetized and recovered uneventfully. Inductions (DEA, 6.8 min; KBAM, 11.6 min; P = 0.04) and recoveries (DEA, 3.2 min; KBAM, 19.6 min; P < 0.01) were faster with DEA compared with KBAM. Quality scores for induction and recovery did not differ between protocols, but maintenance quality was poorer for DEA (P < 0.01). Clinical concerns during DEA immobilizations included apnea, severe hypoxemia (arterial partial pressure of oxygen < 60 mm Hg), muscle rigidity, and tremors. Horses treated with KBAM were moderately hypoxemic, but arterial partial pressures of oxygen were higher compared with DEA (P < 0.01). CLINICAL RELEVANCE: Captive Przewalski horses are effectively immobilized with KBAM, and this protocol results in superior muscle relaxation and less marked hypoxemia during the maintenance phase, but slower inductions and recoveries, compared with DEA.

Pathology in Practice.

In collaboration with the American College of Veterinary Pathologists.

THE INFLUENCE OF ANESTHESIA WITH AND WITHOUT MEDETOMIDINE ON CARDIAC STRUCTURE AND FUNCTION IN SANCTUARY CAPTIVE CHIMPANZEES (PAN TROGLODYTES).

Dependent on timing of assessment, anesthetic agents and specifically medetomidine negatively affect cardiac function in great apes. The aim of this study was to determine the influence of tiletamine-zolazepam (TZ) with and without medetomidine on cardiac structure and function in healthy chimpanzees (Pan troglodytes) during a period of relative blood pressure stability. Twenty-four chimpanzees living in an African wildlife sanctuary undergoing routine health assessments were stratified by age, sex, and body mass and randomized to be anesthetized using either TZ (6 mg/kg; n = 13; seven males and six females) or a combination of TZ (2 mg/kg) and medetomidine (TZM; 0.02 mg/kg; n = 11; five males and six females). During health checks, regular heart rate and blood pressure readings were taken and a standardized echocardiogram was performed 20-30 min after induction. Data were compared between the two anesthetic groups using independent-samples t or Mann-Whitney U tests. Although heart rate (mean ± SD; TZ: 76 ± 10 bpm; TZM: 65 ± 14 bpm, P = 0.027), cardiac output (TZ: 3.0 ± 0.7 L/min; TZM: 2.4 ± 0.7 L/min, P = 0.032), and mitral A-wave velocities (TZ: 0.51 ± 0.16 cm/s; TZM: 0.36 ± 0.10 cm/s, P = 0.013) were lower in the TZM group, there were no statistically significant differences in cardiac structure or the remaining functional variables between groups. Furthermore, there were no statistical differences in systolic (TZ 114.6 ± 14.9 mmHg; TZM: 123.0 ± 28.1 mmHg; P = 0.289) or diastolic blood pressure (TZ: 81.8 ± 22.3 mmHg, TZM: 83.8 ± 20.1 mmHg; P = 0.827) between the groups during the echocardiogram. This study has shown that during a period of relative blood pressure stability, during the first 20-30 min after induction there are few differences in measures of cardiac structure and function between protocols using TZ with or without medetomidine in healthy chimpanzees.

FACTORS AFFECTING TEAR PRODUCTION AND INTRAOCULAR PRESSURE IN ANESTHETIZED CHIMPANZEES (PAN TROGLODYTES).

Measurements of intraocular pressure (IOP) and tear production are key components of ophthalmic examination. Chimpanzees (Pan troglodytes) were anesthetized using either tiletamine-zolazepam (TZ; 2 mg/kg) combined with medetomidine (TZM; 0.02 mg/kg), or, TZ alone (6mg/kg). Tear production was lower (P = 0.03) with TZM (5.63 ± 6.22 mm/min; n = 16) than with TZ (11.13 ± 4.63 mm/min; n = 8). Mean IOP, measured using rebound tonometry in an upright body position (n = 8) was 18.74 ± 3.01 mm Hg, with no differences between right and left eyes. However, positioning chimpanzees in left lateral recumbency (n = 27) resulted in higher IOP in the dependent (left) eye (24.77 ± 4.49 mm Hg) compared to the nondependent (right) eye (22.27 ± 4.65 mm Hg) of the same animal (P < 0.0001). These data indicate medetomidine anesthesia markedly lowers tear production in chimpanzees, and that body position should be taken into consideration when performing rebound tonometry.

Pharmacokinetics of imidocarb dipropionate in white-tailed deer (Odocoileus virginianus) after single intramuscular administration.

This study was designed to investigate the pharmacokinetics of imidocarb, a carbanilide derivative, in white-tailed deer (Odocoileus virginianus). The pharmacokinetic properties of a single intramuscular (IM) dose of imidocarb were determined in 10 deer. A single IM injection of 3.0 mg/kg imidocarb dipropionate was administered, and blood samples were collected prior to, and up to 48 hr after imidocarb administration. Plasma imidocarb concentrations were determined by high-performance liquid chromatography with ultraviolet detection. The disposition of plasma imidocarb was best characterized by a two-compartment open model. The mean ± SE maximal imidocarb concentration in deer was 880.78 ± 81.12 ng/ml at 38.63 ± 5.30 min postinjection. The distribution phase had a half-life (t1/2α ) of 25.90 ± 10.21 min, and plasma imidocarb concentration declined with a terminal elimination half-life (t1/2ß ) of 464.06 ± 104.08 min (7.73 ± 1.73 hr). Apparent volume of distribution based on the terminal phase (VZ /F) was 9.20 ± 2.70 L/kg, and apparent total body clearance (Cl/F) was 15.97 ± 1.28 ml min-1  kg-1 .

Babesia odocoilei and zoonotic pathogens identified from Ixodes scapularis ticks in southern Ontario, Canada.

Cervid babesiosis, caused by the protozoan hemoparasite Babesia odocoilei and transmitted by the blacklegged tick Ixodes scapularis, is an emerging disease of Canadian cervids. This pathogen has not yet been described in humans. Data are lacking on the role of migratory birds in the adventitious spread of Ba. odocoilei-infected ticks, as well as on the infection status of I. scapularis in environments used by susceptible wildlife hosts. Following a high-mortality outbreak of cervid babesiosis at the Toronto Zoo [TZ], the present study was initiated to investigate Ba. odocoilei and other tick-borne pathogens of veterinary and public health importance (Borrelia burgdorferi sensu stricto (s.s.), Anaplasma phagocytophilum, Borrelia miyamotoi, and Babesia microti) in I. scapularis at three sites in southern Ontario, Canada. Blanket dragging for questing ticks yielded I. scapularis from the three sites evaluated: TZ, Point Pelee National Park, and Long Point Bird Observatory [LPBO]. Babesia odocoilei was identified in I. scapularis collected by dragging at the TZ and at LPBO. Borrelia burgdorferi s.s. was identified in I. scapularis at all three sites. Anaplasma phagocytophilum was identified in I. scapularis collected from the TZ. During the springs of 2016 and 2017, 1102 northward-migrating birds were examined for ticks at LPBO. One or more I. scapularis were found on 3.2% of birds (n = 595) in 2016, and 6.7% (n = 507) of birds in 2017. Overall, across both years, 0.2% and 0.5% of birds carried one or more I. scapularis ticks that tested PCR-positive for Ba. odocoilei and Bo. burgdorferi s.s., respectively. These data indicate that Ba. odocoilei-positive I. scapularis are found in southern Ontario, and suggest that bird-borne ticks have the potential to contribute to range expansion of both Ba. odocoilei and Bo. burgdorferi s.s. in Canada.

MOLECULAR DETECTION OF BABESIA ODOCOILEI IN WILD, FARMED, AND ZOO CERVIDS IN ONTARIO, CANADA.

Babesia odocoilei, a tick-borne protozoan hemoparasite of white-tailed deer ( Odocoileus virginianus), is being increasingly recognized as a cause of disease in captive cervids in North America. Historically endemic in white-tailed deer, the natural wildlife reservoir in the southeastern US, B. odocoilei has been recently associated with hemolytic anemia in captive Eurasian tundra reindeer ( Rangifer tarandus tarandus), wapiti ( Cervus canadensis), and woodland caribou ( Rangifer tarandus caribou) in the northcentral and northeastern US and several Canadian provinces. The emergence of B. odocoilei is likely related to the northward expansion of the range of the tick vector, Ixodes scapularis, and possibly to cervid translocations. Following a disease outbreak in reindeer and wapiti at the Toronto Zoo in Ontario, Canada, we utilized a prospective postmortem survey to investigate the prevalence of B. odocoilei in wild, farmed, and zoo cervids in Ontario ( n=270) in 2016-18 by PCR and DNA sequencing of spleen samples. Zoo bovids have been suggested as potential hosts of B. odocoilei in zoos affected by cervid babesiosis, so we also collected postmortem samples from five species of bovids ( n=7) at the Toronto Zoo that died or were euthanized during this time. We detected B. odocoilei in 1% (2/142) of farmed red deer ( Cervus elaphus) as well as in 3% (1/29) of captive wapiti and 4% (3/68) of wild white-tailed deer. Tissues from all zoo bovids and caribou, zoo and wild moose ( Alces alces), and farmed white-tailed deer, wapiti-red deer hybrids, and fallow deer ( Dama dama), tested negative for B. odocoilei. No clinical cases of babesiosis were encountered during this study. These findings suggest that white-tailed deer are a potential natural wildlife reservoir for B. odocoilei in Ontario and that red deer and wapiti could serve as more-localized reservoirs.