Raccoon dogs may carry and transmit COVID-19–causing SARS-CoV-2 to humans, although critical differences in the enzyme that facilitates viral entry into the cell may make the jump unlikely, a study in PLOS Pathogens finds.

"The key to a coronavirus moving from one species to another is its spike protein's ability to bind to receptors on the cells of the new host," the authors noted.

University of Minnesota researchers probed the interaction between the spike protein of SARS-CoV-2 and angiotensin-converting enzyme 2 (ACE 2), which lets the virus enter the cell. Coronaviruses such as SARS-CoV-2 are known for their ability to jump species, the researchers said.

Raccoon dogs are small, burly, foxlike canines native to East Asia that are thought to have been a possible intermediary in the SARS-CoV-2 interspecies jump to humans, which led to the COVID-19 pandemic. The animals, along with palm civets, are also thought to have been involved in the spread of SARS-CoV-1, the virus that caused an outbreak of severe acute respiratory syndrome (SARS) in 2002-2003.

"Several species are under scrutiny as potential culprits, including bats, pangolins, and raccoon dogs," the authors wrote. "Raccoon dogs came under suspicion after their DNA was detected alongside SARS-CoV-2 genetic material in samples from the Huanan Seafood Market in Wuhan City [China], which is widely considered the pandemic's point of origin."

Could also affect other mammals

Biochemical analysis showed raccoon dog ACE 2 does allow SARS-CoV-2 to enter the cell, although not as effectively as human ACE 2. 

Structural comparisons highlighted differences in the virus-binding residues of raccoon dog ACE2 compared to human ACE2 …, explaining their varied effectiveness as receptors for SARS-CoV-2.

"Structural comparisons highlighted differences in the virus-binding residues of raccoon dog ACE2 compared to human ACE2 …, explaining their varied effectiveness as receptors for SARS-CoV-2," the researchers wrote. "These variations contribute to the species barrier that exists between raccoon dogs and humans regarding SARS-CoV-2 transmission."

The discovery sheds light on how SARS-CoV-2 may affect other mammals, as well. "Our research underscores the potential of raccoon dogs as SARS-CoV-2 carriers and identifies molecular barriers that affect the virus's ability to jump between species," they concluded.

The prevalence of polymyxin-resistant bacterial strains in India exceeds the global average, according to a review and meta-analysis published this week in the Journal of Antimicrobial Chemotherapy.

Polymyxins are considered a last-resort antibiotic class for multidrug-resistant gram-negative bacteria. While global resistance to polymyxins has emerged over the past decade due to their extensive use in healthcare and food-producing animals, the extent of polymyxin resistance in India has not been extensively studied. Colistin (polymyxin E) was widely used on Indian poultry farms prior to 2019, while Indian hospitals have become increasingly reliant on colistin because of the increasing number of patients with carbapenem-resistant infections.

The meta-analysis of 41 studies that included 24,589 gram-negative bacterial (GNB) isolates found a 15% rate of polymyxin-resistant bacteria in India. Among all Indian states that have reported polymyxin resistance, the highest resistance rates were found in Tamil Nadu (28.3%), Uttar Pradesh (16.3%), and Odisha (15.9%). The global average is 10%.

A breakdown of polymyxin-resistant isolates by their source found 89% were from clinical sources, and the remaining 11% were from environmental sources. The rate of polymyxin resistance was 13.5% among clinical isolates and 27.6% among environmental isolates.

Plasmid-borne MCR genes

The study also found that of all the polymyxin-resistant isolates, 8.4% were found to be positive for plasmid-borne mobile MCR genes, which confer resistance to colistin and can be shared among different species of bacteria. The first MCR genes were discovered in Escherichia coli and Klebsiella pneumoniae in China in 2015 and have since spread globally. 

"As the potential of rapid dissemination of plasmid-borne mcr genes is significantly high, it is pertinent to conduct periodic surveillance to monitor their distribution in the environment and clinic," the study authors wrote.

The authors say sustained measures need to be in place to contain further spread of the polymyxin-resistant phenotype and to develop better versions of polymyxins and their derivatives.

• The US Food and Drug Administration (FDA) has pushed back its review of Moderna's respiratory syncytial virus (RSV) vaccine owing to administrative issues. According to a press release from Moderna, the FDA has informed Moderna that it is working to conclude the review by the end of May 2024. Moderna said the mRNA vaccine remains on track to be reviewed at the Center for Disease Control and Prevention's Advisory Committee on Immunization Practices at the end of June. The single-dose vaccine targets RSV in adults 60 and older. "The FDA has not informed Moderna of any issues related to vaccine safety, efficacy or quality," the company said in the release.
• Pharmaceutical giants Sanofi and Novavax have announced an exclusive licensing agreement to co-commercialize COVID-19 vaccines beginning in 2025 and jointly develop novel flu-COVID-19 combination vaccines. "With flu and COVID-19 hospital admission rates now closely mirroring each other, we have an opportunity to develop non-mRNA flu-COVID-19 combination vaccines offering patients both enhanced convenience and protection against two serious respiratory viruses," said Jean-Francois Toussaint, PhD, the global head of vaccine research and development at Sanofi, in a press release from that company. The co-exclusive license will allow the partnership to commercialize Novavax's current stand-alone adjuvanted COVID-19 vaccine and include a sole license to Novavax's adjuvanted COVID-19 vaccine for use in combination with Sanofi's flu vaccines, and a non-exclusive license to use Novavax's Matrix-M adjuvant (immune-booster) in vaccine products.
• The Global Polio Eradication Initiative confirmed two new polio cases this week, both caused by circulating vaccine-derived poliovirus type 2. Angola has its first polio case since 2022. Chad reported its second of the year. In 2023, Chad reported 55 cases.