How Common Is Rabies?

Hello, Summarians!

This newsletter aims to help us navigate the deluge of information we face every day. It feels as if that increasing flow is also becoming more complex. We provide a solution—summaries of current periodicals to keep you up to date.

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Rabies Incidence

Animal rabies in the United States persists in distinct reservoir species that maintain specific rabies virus variants (RVVs) within defined geographic areas, including Arctic foxes, Arizona gray foxes, California skunks, Eastern raccoons, North and South Central skunks, Puerto Rico mongooses, and various bat species. Although these RVVs have characteristic distributions, rabies can infect any mammal, and translocation or spillover events occasionally occur outside known enzootic areas. Rabies surveillance in the US is managed through the CDC’s National Rabies Surveillance System (NRSS) and supported by the USDA Wildlife Services, while Canada and Mexico operate their own national surveillance programs. These systems track rabies prevalence, monitor geographic shifts in RVV territories, detect host-shift events, and guide wildlife rabies control measures. 

In 2023, 89,530 animals were submitted for rabies testing in the US, with 87,058 samples processed and 3,760 testing positive, representing a 5.1% increase in positive cases compared to 2022. Most samples were submitted due to potential human exposure. Wildlife accounted for the majority of positive detections (3,451 cases), while domestic animals comprised 309 cases, with cats being the most frequently reported rabid domestic species. Bats were the leading rabid wildlife species, followed by raccoons and skunks. Virus variant characterization was performed on 35.6% of positive cases, confirming circulation of multiple RVVs. 

Bat-related RVVs accounted for 1,311 positive cases and remain geographically widespread, although detections have been declining since 2013. Arctic Fox RVV was responsible for 46 cases, including a rare rabid moose. Arizona Gray Fox RVV accounted for 12 cases, all confirmed by typing, while California Skunk RVV produced 18 cases, reflecting stable detection levels. Eastern Raccoon RVV caused 2,001 cases and continues to decline from historical peaks, although a rabid kitten with this variant was discovered outside its known range in Nebraska, prompting a multiagency containment response. North Central Skunk RVV caused 60 cases, including a pet skunk infected within an enzootic area. Puerto Rico Mongoose RVV accounted for 25 cases, continuing its long-term decline, and South Central Skunk RVV was associated with 287 cases, also trending downward. Wildlife rabies control relied heavily on oral rabies vaccination (ORV), with over 7.8 million vaccine baits distributed across strategic regions, including an intensive effort in Nebraska to prevent the establishment of Eastern Raccoon RVV. 

In Canada, 2,372 animal samples were tested, yielding 113 positive cases (4.8% positivity). Most cases were in wildlife, primarily bats, with smaller numbers in foxes, skunks, and raccoons, alongside a few domestic animals. Eastern Raccoon RVV persisted at low levels following past outbreaks in Ontario and New Brunswick, while Arctic Fox RVV cases declined and North Central Skunk RVV was limited to Manitoba. Mexico reported 418 positive cases, primarily in cattle, along with horses, goats, sheep, and several bat species, reflecting endemic circulation of vampire bat-associated rabies. 

Remarkably, 2023 was the first year since at least 2000 with no reported human rabies cases in the US, Canada, or Mexico, highlighting the success of rabies vaccination programs, public health outreach, and postexposure prophylaxis access. Nevertheless, the risk of rabies exposure persists, especially through wildlife reservoirs and translocation events. Surveillance systems in all three countries remain critical for detecting and responding to rabies incursions and maintaining freedom from dog-maintained RVVs. Enhanced collaboration, One Health approaches, and regional data sharing are emphasized as essential for sustaining rabies control and preventing future epidemiologic shifts. 

Boutelle, C., Bonaparte, S., Orciari, L. A., Kirby, J. D., Chipman, R. B., Fehlner-Gardiner, C., Thang, C., Julien, D., Hirose, J. A. M., García, B. C., Wallace, R. M., & Blanton, J. D. (2025). Rabies surveillance in the United States during 2023. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.25.05.0344 

Bottom line — Slight increase from the previous year.

Mitotherapy in Horses

Osteoarthritis (OA) is a multifactorial disease influenced by genetic, mechanical, and environmental factors and is a leading cause of pain, disability, and economic loss in humans and horses. Up to 60% of equine lameness is attributed to OA, making it a significant issue for equine athletic performance. Horses are also used as a naturally occurring model to evaluate novel therapeutics that could benefit both human and veterinary medicine, given that no current treatments can halt or reverse OA progression. The lipopolysaccharide (LPS)-induced synovitis model is commonly used to study early inflammatory mechanisms and potential treatments, including mitochondrial therapy (mitotherapy), which seeks to restore cell function by transplanting exogenous mitochondria. Prior studies showed exogenous mitochondria could influence equine synoviocytes in vitro, and injection of autologous mitochondria was well tolerated in vivo, prompting investigation of its effect on LPS-induced synovitis. 

This study aimed to evaluate whether injecting mitochondria purified from autologous equine platelets into joints affected by LPS-induced synovitis could modulate inflammation, as measured by synovial fluid cytology, protein cytokine expression, and leukocyte gene expression, and to further characterize the inflammatory response of this model. The hypothesis was that mitotherapy would reduce inflammatory responses locally without inducing systemic inflammation. While LPS injection produced moderate local inflammation, with increases in synovial leukocytes, proinflammatory cytokines, and inflammatory gene expression, systemic inflammation remained mild and largely within reference ranges. 

Mitotherapy did not produce detectable differences compared to vehicle controls in cytology, cytokine profiles, or gene expression. Potential reasons include limitations in the mitochondrial preparation, which lacked assessment of functional viability, uncertainty regarding effective dosing, and the anti-inflammatory effects of the platelet-poor plasma vehicle, which may have masked treatment effects. The study was also limited to synovial fluid analysis rather than direct synovial tissue sampling, which might have provided more sensitive indicators of treatment efficacy. 

The bilateral model of LPS-induced synovitis allowed for internal controls, reduced animal use, and confirmed known dynamics of early inflammation, including neutrophil influx followed by mononuclear cells, upregulation of proinflammatory cytokines such as IL-1β, IL-6, TNF-α, and IL-8, and changes in mitochondrial-related genes OPA1 and PINK1. These findings support the model’s value in assessing synovitis therapies and highlight novel mitochondrial gene responses in equine joint inflammation. Although mitotherapy was safe and well tolerated, it did not reduce synovial inflammation under the conditions tested, suggesting that future efforts should refine mitochondrial preparation and dosing and consider additional outcome measures, such as histology or noninvasive biomarkers, to better detect potential therapeutic effects. 

Khaliji, E., Marycz, K., Horna, M., Morgan, J. M., Galuppo, L. D., Vapniarsky, N., & Cassano, J. M. (2025). Platelet-derived mitochondrial preparation did not alter early inflammatory markers in a bilateral lipopolysaccharide-induced model of equine synovitis. American Journal of Veterinary Research https://doi.org/10.2460/ajvr.25.05.0187 

Bottom line — Not effective in this study.

Chlorhexidine and Contact Time

Surgical site infections (SSIs) are a common complication in veterinary surgery, affecting 3% to 18% of canine and feline patients and leading to increased morbidity, mortality, hospitalization time, and costs. Risk factors include patient weight, anesthetic risk score, wound contamination, antimicrobial use, and inadequate surgical site disinfection (SSD). Chlorhexidine is widely used for SSD due to its broad antimicrobial activity and residual effect, yet adherence to recommended contact times is often poor. Human medicine has shown that chlorhexidine reduces SSI rates compared to iodine-based protocols, but veterinary studies reveal limited knowledge among technicians about proper concentrations and required contact times. 

This study measured chlorhexidine contact times in five Australian veterinary hospitals and found that 29.85% of SSD episodes failed to meet the required three-minute contact time. One hospital had a particularly high rate of noncompliance (64.62%), likely influenced by workflow pressures, limited supervision, and a belief that a final alcohol-chlorhexidine application eliminated the need for initial contact time adherence. Variability in practices and knowledge aligns with prior studies showing many technicians are unaware of correct solution concentrations and often determine scrub duration by visual cleanliness rather than standardized timing. 

Noncompliance with SSD protocols has important implications, as insufficient contact time may increase SSI risk, while excessive contact time can prolong anesthesia, contribute to hypothermia, and negatively affect outcomes. Hospitals with high compliance sometimes showed extended contact times due to patient transfer delays, further highlighting workflow issues that may impact patient safety. Strategies such as using timers, improving staff training, incorporating supervision, and implementing surgical checklists may improve adherence. 

The study had limitations, including the absence of SSI outcome data, limited geographic scope, and a lack of detailed investigation into reasons for noncompliance. It also focused solely on chlorhexidine, leaving adherence to other antiseptic agents unexamined. Future research should explore the underlying causes of poor compliance and evaluate targeted interventions to improve SSD protocol adherence. 

Overall, the findings reveal significant variability and deficiencies in chlorhexidine SSD practices, emphasizing the need for improved education, standardized procedures, and practical tools to enhance compliance and reduce the risk of SSIs in veterinary surgery. 

Burrows, C. S., & Uquillas, E. (2025). Observation of surgical site disinfection with chlorhexidine reveals a failure to meet minimum contact time requirements in almost 30% of cases. Journal of the American Veterinary Medical Association https://doi.org/10.2460/javma.25.04.0226 

Bottom line — Following protocols is essential.

Just putting things in perspective …