News Bulletin March 2025: Bird Flu, Antimicrobial usage, Methane and Dung beetles

Bird Flu in the USA

Further to a number of our recent reports on the worldwide bird flu epidemic, and in particular the impact on the dairy industry in the USA [1], it seems pertinent to provide a further update on a problem that is certainly not going away. The H5N1 strain of highly pathogenic avian influenza has devastated bird populations throughout the world with another recent outbreak being reported in Northern Ireland [2]. 

But it is the situation in the USA dairy industry which continues to give cause for concern, for several reasons.

The most recent report from CDC (US Disease Control Center), the national surveillance organisation, indicates that 972 herds are affected in 17 different states, with the highest incidence now centered in California [3]. A total of 69 human cases have been reported nationally with the first human death linked to H5N1 infection occurring in Louisiana in January. Critically, no human to human transmission has occurred but the virus isolated from that first mortality had shown a worrying mutation [4]. While the risk to the general public remains low, cases are being detected in individuals with close contact with poultry and dairy cattle [5]. The major concern remains that every human infection presents an opportunity for a critical mutation which could introduce human to human transmission, the required precursor for the genesis of a national epidemic. 

A further concern must also be the change of political environment in the USA. At a time when increased vigilance and investment in surveillance are critical, science budgets appear to be seriously challenged by the new President’s regime.

Dung Beetles and anthelmintic use in west Wales

VetSalus consultant Anuschka Marsden has been pursuing an interesting project on anthelmintic usage and dung beetle prevalence on a group of farms in west Wales. We provided an interim report on this in September 2024 [6]. Anushchka is currently analysing the final results, but has provided a further update on what promises to be a fascinating study. She reports that an early conclusion is that every surveyed farm shows a different pattern of infection, and a place definitely exists for bespoke veterinary designed worm and fluke plans.

It also appears that the project was a win: win: win in that it provided savings to the farmers involved via reduced usage of anthelmintics, generated fees for the vet clinic and had a positive environmental impact. Anuschka plans to roll out the project for the entire practice next year and a number of possible packages are being developed based on faecal egg count monitoring, blood samples and dung beetle assessments. The final report will be summarised here in due course.

Methane mitigation

A number of trials have recently been reported outlining the steady progress of additives which can significantly reduce methane generation and also be conveniently administered to cattle. Further details of these will be coming in future articles. The social media storm generated in the United Kingdom by revelations of a trial involving ARLA, a major dairy producer, and several supermarkets, indicate that the communication of such developments to the general public is complex. The reduction of methane output resulting from the inclusion of a carefully researched methane inhibitor in the diet of cows, might be expected to generate a positive message of methane mitigation. But many people are highly suspicious of science these days and the ease with which social media can generate complex conspiracy theories, with no scientific validity, is concerning.

Dry cow therapy protocols in New Zealand 

The dairy special interest branch of New Zealand Veterinary Association, in conjunction with the Veterinary Council of New Zealand and Dairy NZ, have been running a number of well attended roadshows throughout the country in recent weeks. The meetings have addressed the complex issues around dry cow therapy for dairy cows and included discussions on both science and professional ethics.

For most dairy farms in New Zealand, ‘drying off’ is an annual event. The country’s grass based, seasonal dairy industry means that this occurs mainly in May. Historically, this has sometimes created pressure on the supply of products and a tendency by some farmers to view dry cow therapy as a commodity, rather than a carefully controlled, prescribed product. The increasing use of teat sealants, rather than antibiotics, at drying off has increased the complexity of the situation. The correct treatment choice involves a number of key decisions which impact upon antimicrobial usage, milk quality and animal welfare. The balance between whole herd therapy or selective treatment with an antibiotic is particularly important.

The meetings have introduced a new protocol, based on some sound science, which will assist vets in advising their clients. This establishes a number of clear criteria when whole herd therapy might be indicated, while advocating the use of teat sealants in other situations. The need for the careful control of the latter, including the necessity to ensure staff applying the product are suitably skilled, was also covered. The detailed technical advice, which will be of interest to veterinarians in other countries, is publicly available from Dairy NZ [7].