Evidence of Borrelia theileri in Wild and Domestic Animals in the Kafue Ecosystem of Zambia

Members of the genus Borrelia are arthropod-borne spirochetes that are human and animal pathogens. Vertebrate hosts, including wild animals, are pivotal to the circulation and maintenance of Borrelia spirochetes. However, information on Borrelia spirochetes in vertebrate hosts in Zambia is limited. Thus, we aimed to investigate the presence of Borrelia spirochetes in wild animals and cattle in Zambia. A total of 140 wild animals of four species and 488 cattle DNA samples from /near the Kafue National Park were collected for real-time PCR screening, followed by characterization using three different genes with positive samples. Five impalas and 20 cattle tested positive using real-time PCR, and sequence analysis revealed that the detected Borrelia were identified to be Borrelia theileri, a causative agent of bovine borreliosis. This is the first evidence of Borrelia theileri in African wildlife and cattle in Zambia. Our results suggest that clinical differentiation between bovine borreliosis and other bovine diseases endemic in Zambia is required for better treatment and control measures. As this study only included wild and domestic animals in the Kafue ecosystem, further investigations in other areas and with more wildlife and livestock species are needed to clarify a comprehensive epidemiological status of Borrelia theileri in Zambia

Spatially Discordant Alternans and Arrhythmias in Tachypacing-Induced Cardiac Myopathy in Transgenic LQT1 Rabbits: The Importance of I_Ks and Ca²⁺ Cycling

<div><p>Background</p><p>Remodeling of cardiac repolarizing currents, such as the downregulation of slowly activating K⁺ channels (I_Ks), could underlie ventricular fibrillation (VF) in heart failure (HF). We evaluated the role of <i>I</i>_ks remodeling in VF susceptibility using a tachypacing HF model of transgenic rabbits with Long QT Type 1 (LQT1) syndrome.</p><p>Methods and Results</p><p>LQT1 and littermate control (LMC) rabbits underwent three weeks of tachypacing to induce cardiac myopathy (TICM). <i>In vivo</i> telemetry demonstrated steepening of the QT/RR slope in LQT1 with TICM (LQT1-TICM; pre: 0.26±0.04, post: 0.52±0.01, P<0.05). <i>In vivo</i> electrophysiology showed that LQT1-TICM had higher incidence of VF than LMC-TICM (6 of 11 vs. 3 of 11, respectively). Optical mapping revealed larger APD dispersion (16±4 vs. 38±6 ms, p<0.05) and steep APD restitution in LQT1-TICM compared to LQT1-sham (0.53±0.12 vs. 1.17±0.13, p<0.05). LQT1-TICM developed spatially discordant alternans (DA), which caused conduction block and higher-frequency VF (15±1 Hz in LQT1-TICM vs. 13±1 Hz in LMC-TICM, p<0.05). Ca²⁺ DA was highly dynamic and preceded voltage DA in LQT1-TICM. Ryanodine abolished DA in 5 out of 8 LQT1-TICM rabbits, demonstrating the importance of Ca²⁺ in complex DA formation. Computer simulations suggested that HF remodeling caused Ca²⁺-driven alternans, which was further potentiated in LQT1-TICM due to the lack of I_Ks.</p><p>Conclusions</p><p>Compared with LMC-TICM, LQT1-TICM rabbits exhibit steepened APD restitution and complex DA modulated by Ca²⁺. Our results strongly support the contention that the downregulation of I_Ks in HF increases Ca²⁺ dependent alternans and thereby the risk of VF.</p></div

<i>In vivo</i> VF Inducibility using Pen protocol (S1S2S3S4).

<p>P<0.05 LQT1-TICM vs. LQT1-SH-P; all other comparisons, P = NS.</p><p><i>In vivo</i> VF Inducibility using Pen protocol (S1S2S3S4).</p

Computer simulations of APD and Ca2+ alternans under different conditions.

<p><b>(A</b>) V_m (upper) and whole-cell Ca²⁺ concentration (lower) versus time for the control condition at CL = 280 ms. (<b>B</b>) V_m and whole-cell Ca²⁺ concentration versus time for the HF condition. (<b>C</b>) V_m and whole-cell Ca²⁺ concentration versus time for the same condition as in B but with zero I_Ks. (<b>D</b>) Peak whole-cell Ca²⁺ concentrations of two consecutive beats versus CL for the three conditions. (<b>E</b>) APD of the same two consecutive beats as in D versus CL for the three conditions.</p

Prevalent discordant alternans in LQT1-TICM.

<p>(<b>A</b>) Sample traces of DA from three locations. (<b>B</b>) Space-time plot of DA along the line a-c in panel A. (<b>C</b>) APD (black) and Ca²⁺ duration (red) along the line a-c. Alternation between odd and even beats was larger in Ca²⁺. (<b>D</b>) Maps of activation and nodal lines of DA. Note that activation in odd beats shows markedly slowing conduction toward the apex region. However, the nodal lines were not associated with the alternating activation pattern.</p

Free-Moving Telemetry: QT-RR Ratios.

<p>(<b>A-D</b>): QT/RR relationship in awake, free-moving rabbits, recorded approximately every 20 minutes for 24 hours in each group. Lines indicate linear regression derived from the mean of all individual regression lines per genotype. Note that LQT1-TICM demonstrates steeper QT/RR slope post-pacing compared to pre-pacing. (<b>E</b>): VERP at BCL = 240 ms in LMC-TICM, LQT1-TICM, and sham animals. No significant difference was found among the four groups (<b>F</b>): VERP (BCL = 240 ms) vs. VF frequency in 5 LMC-TICM and LQT1-TICM animals. Unlike LMC-TICM, LQT1-TICM did not show a correlation between VERP and VF frequency.</p