The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) today confirmed 62 more avian flu outbreaks in dairy cattle, all involving California herds. The latest detections lift the state’s total since the end of August to 398 and the national total to 612.

California is the nation’s largest dairy producer, and outbreaks in the Central Valley have now affected nearly one-third of the state’s estimated 1,300 herds.

Poultry outbreaks include California commercial farms, Midwest states

In poultry outbreaks developments, APHIS today also confirmed more poultry outbreaks from four states, including two more reappearances in Midwestern states.

The largest of the latest outbreaks includes a large layer farm in California’s Kern County that has more than 1 million birds, as well as a duck meat producer in the state’s Marin County.

Over the past several weeks, most the outbreaks in poultry have occurred in western states along with Pacific flyway, affecting several large commercial farms in California and reaching all the way to backyard birds in Hawaii. However, over the past few days, detections have been confirmed in a few Midwestern states.

Today’s confirmations include a commercial farm in Illinois, which involves a facility in Henry County that has 5,600 birds. Henry County is in northwestern Illinois. The latest outbreak marks the state’s first since February 2023. Also, APHIS confirmed the virus in a backyard flock of 20 birds in South Dakota, its first since March. The location is Lake County, which is the southwestern part of the state. 

Elsewhere, APHIS confirmed the virus in a backyard flock in Alaska located in Matanuska Susitna Borough, which is part of the Anchorage metro area. The outbreak is the first involving Alaskan poultry since November 2023, though the virus was recently reported in a few samples from raptors and waterfowl.

An analysis of US long-term care (LTC) pharmacy dispensing data shows overall antibiotic prescribing rates in nursing homes fell from 2013 to 2021, researchers reported today in Antimicrobial Stewardship & Healthcare Epidemiology.

For the study, researchers from the US Centers for Disease Control and Prevention analyzed data on antibiotics dispensed in 1,900 unique US LTC facilities from 2013 to 2021. Overall antibiotic use was reported as the percent of LTC residents receiving an antibiotic per year, antibiotic courses per 1,000 resident-days, and antibiotic days of therapy (DOT) per 1,000 resident-days overall. The researchers also looked at median antibiotic duration and antibiotic class.

Antibiotic duration remains an issue

Over the study period, the percentage of LTC residents receiving an antibiotic decreased from 51% to 44%, total use rates in antibiotic courses/1,000 resident-days fell by 8%, and total use rates in antibiotic DOT/1,000 resident days fell by 8%. The steepest declines occurred from 2019 to 2021, likely because of changes in antibiotic prescribing practices during the COVID-19 pandemic.

Prescribing rates decreased across several antibiotic classes, most notably fluoroquinolones (49%) and macrolides (30%). Concurrently, prescribing rates of tetracyclines and cephalosporins increased by 56% and 22%, respectively. The median antibiotic course duration was 7 days.

The study authors note that the decline in LTC antibiotic prescribing rates coincides with the 2017 Centers for Medicare & Medicaid Services rule requiring that LTCs have a system for tracking antibiotic use. They also say the findings highlight potential opportunities to improve antibiotic treatment duration, which did not change over the study period. 

"Increasing evidence supports shorter duration of treatment for most infections, and every day of additional antibiotic therapy is associated with increased risk of adverse events," they wrote. "Also, prolonged antibiotic durations contribute 18% of total DOT and provide another opportunity for evaluation of appropriateness of potential prophylaxis or suppressive therapy."

The World Health Organization (WHO) said yesterday that three more countries have reported cholera outbreaks since its last update in October: Iraq, Lebanon, and South Sudan.

Iraq has reported 571 cases, including 1 death. Lebanon has one case, and South Sudan has 49 cases, 1 of them fatal. So far 33 countries have reported cholera outbreaks this year.

Cases in October were 42% lower than the same period in 2023, the WHO said. However, deaths rose 54%, a sign of severe outbreak response settings. Multiple factors include conflict, population displacement, natural disasters, impacts from climate change, and rural locations and flooding in areas with poor infrastructure and lack of healthcare access.

 “These cross-border dynamics have made cholera outbreaks increasingly complex and harder to control,” the WHO noted.

Progress with vaccine production, but shortage persists

This month oral cholera vaccine production reached record numbers, the highest since 2013; however, despite the progress, the global emergency stockpile in October had less than 600,000 doses, well below the 5 million needed for effective outbreak response, the report said. 

“This persistent shortage continues to hinder efforts to control cholera outbreaks and respond promptly to the spread of the disease.”

A new study in The Lancet Global Health highlights the potential impact that vaccines for diarrhea could have on antibiotic use in young children.

Using data from a previously published study that explored enteric infections and diarrheal illness in children in low- and middle-income countries, a team of US and Chinese researchers analyzed a cohort of children enrolled from 2009 through 2012 in Bangladesh, India, Nepal, Pakistan, and Tanzania who had antibiotic-treated diarrheal episodes in the first 2 years of life. They then used Monte Carlo simulations to estimate the hypothetical impact of nine vaccine scenarios (including six single-pathogen vaccines and three combination vaccines) on antibiotic-treated diarrhea, overall antibiotic courses, and antibiotic exposures to bystander pathogens.

Among 1,119 children, there were 3,029 (135.3 courses per 100 child-years) antibiotic-treated diarrhea episodes, of which 546 were caused by bacteria, 763 by viruses or parasites, and the rest were of unknown origin. Under the assumption of 100% vaccination coverage, the researchers estimated a Shigella vaccine would cause the greatest reductions compared with the other single-pathogen vaccines in antibiotic courses for all-cause diarrhea (a 6.1% relative reduction; –8.2 courses per 100 child-years), antibiotic courses overall (1.0% relative reduction; –8.2 courses per 100 child-years), and antibiotic exposures to bystander pathogens (1.2% relative reduction; –15.9 courses per 100 child-years). An adenovirus-norovirus-rotavirus vaccine would cause the greatest reductions in antibiotic use (12.2 courses per 100 child-years) compared with the other combination vaccines. 

Ancillary benefits

The percentage reduction in antibiotic courses for diarrhea of any cause ranged from 2.0% to 9.7% across sites for the Shigella vaccine, and from 3.0% to 15.9% across sites for the adenovirus-norovirus-rotavirus vaccine. 

The study authors say that given the high burden of diarrhea in low-resource settings, antibiotic overuse in young children is likely contributing to antimicrobial resistance.

"Children in low-resource settings are frequently treated with antibiotics for diarrhoea and vaccines for diarrhoea could have the ancillary benefit of preventing antibiotic use with implications for antimicrobial resistance," they wrote. "Prioritisation of development of vaccines for diarrhoea should consider potential impacts on antibiotic use, and combination vaccines would best achieve goals for limiting antibiotic resistance."