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WOAH Biological Standards Commission decides to relaunch a global call for new tuberculin candidates after extensive international trials

Following a decade of international studies, the WOAH Biological Standards Commission, supported by an ad hoc group of experts, has concluded that the proposed replacement candidates for the International Standard for Bovine Tuberculin do not meet the required potency levels. It will now relaunch a global call for new candidates’ materials. 

What is the International Standard for Bovine Tuberculin? 

The International Standard Bovine Tuberculin (ISBT) is a biological reference material derived from Mycobacterium bovis strain AN5. Established nearly three decades ago, it defines a standardised protein concentration that serves as the global benchmark for tuberculin potency testing.  

ISBT is used worldwide in bovine tuberculosis control programmes for screening cattle. All commercial bovine tuberculin preparations must be calibrated against this standard. 

The science behind tuberculin testing 

Tuberculin testing exploits the immune system’s memory of infection. When Mycobacterium tuberculosis complex organisms infect cattle, the animal’s immune system develops a hypersensitivity response to specific bacterial proteins. The tuberculin skin test capitalises on this biological activity by injecting purified protein derivative (PPD) intradermally and measuring the resulting immune response as an increase in skin thickness. This delayed hypersensitivity reaction, measured 72 hours post-injection, indicates prior exposure to tuberculosis. 

A decade-long effort to replace the standard 

The current ISBT, established in 1986, has been in limited supply since 2015. In response, WOAH’s Biological Standards Commission, supported by an ad hoc group of mammalian tuberculosis reference laboratory experts, has coordinated experiments with multiple laboratories, research institutes and tuberculin manufacturers across continents to identify a suitable replacement. 

Key findings  

Two candidates were initially shortlisted in 2017. Following further evaluation, only one (Candidate B) progressed to international collaborative trials conducted between 2018 and 2025.  

However, the latest assays revealed persistent potency shortfalls: 

• Potency levels (18,000–19,116 IU/mg) remained well below the required minimum of 32,000 IU/mg. 

• Multiple laboratories confirmed inconsistent results despite protocol refinements. 

• High assay variability and weak dose-response relationships hindered reliable potency determination. 

Final trials in November 2025 confirmed that Candidate B does not meet the criteria to replace ISBT. 

Future directions 

The Biological Standards Commission acknowledged that PPD is a complex biological substance having many specific and non-specific proteins. They emphasised that accepting a lower potency international standard would compromise the comparability of global tuberculin standardisation across laboratories and batches.  

The Commission therefore decided to: 

• relaunch a global call for new tuberculin candidates. 

• support the development of alternative approaches for PPD-based tests such as the Molecularly Defined Tuberculins (MDTs) which use specific peptides as a long-term alternative to traditional PPD-based assays. 

While promising, MDTs require further field validation across different epidemiological settings before they can replace current methods.

More information 

The full meeting report, including detailed methodology and statistical analyses, is available on the WOAH website: 

WOAH Ad hoc Group on Replacement of the International Standard for Bovine Tuberculin. Report 2015-2025.

Ad hoc Groups – WOAH – World Organisation for Animal Health 

Biological Standards Commission – WOAH – World Organisation for Animal Health 

Contact: [email protected] 

Updated on 8 May 2024

The ongoing spread of High Pathogenicity Avian Influenza (HPAI) in different regions of the world, alongside the recent detections of cases in cattle, is raising concerns within the international community.

While HPAI primarily affects poultry and wild birds, avian influenza can occasionally be transmitted to mammals, including humans. In the last two years, an increasing number of H5N1 avian influenza cases are being reported in terrestrial and aquatic mammalians animals.

The recently reported detections of HPAI in dairy cattle in the United States of America, have raised international concerns. Infected cattle may be asymptomatic or with mild illness showing non-specific clinical signs such as decreased milk production, thicker-colostrum‐like milk, reduced appetite, lethargy, fever and dehydration. These infections in cattle could indicate an increased risk of H5N1 viruses becoming better adapted to mammals, and potentially spilling over to humans and other livestock.  

Initial investigations so far have revealed that raw milk from infected cows is a high-risk material. Thus, only milk produced by healthy cows should be commercialised. There are evidence of horizontal virus transmission from infected lactating cows to other animals including cows, cats and poultry.  No specific adaptation of the virus to either humans or mammals was identified. Several studies are being carried out to further explore the pathogenesis and transmission routes of these viruses, including among cattle and from cattle to other animals. 

In collaboration with its Reference Centres, our networks of experts and Members, the World Organisation for Animal Health (WOAH) is closely monitoring the situation to assess the risks to animals, but also to humans, which is currently considered low. Timely and transparent reporting is crucial to maintain a good understanding of the disease situation and prevent any type of misinformation or disinformation. 

WOAH reminds its 183 Members that, based on the information currently available, restrictions to the international trade of healthy cattle and their products are not recommended unless justified by an import risk analysis conducted according to the WOAH Terrestrial Animal Health Code Chapter 2.1.  

WOAH calls on its Members to: 

• Maintain enhanced avian influenza SURVEILLANCE in domestic and wild birds.  
• INCLUDE HPAI as a differential diagnosis, in non-avian species, including cattle and other livestock populations, with high risk of exposure to HPAI viruses, in particular:  
  • Animals showing clinical signs compatible with avian influenza; 
  • Sick or dead domestic animals near affected premises;   
  • Suspected, including apparently healthy animals, that have been exposed to or epidemiologically linked to suspected or confirmed HPAI in birds or cattle (i.e. situated in HPAI high-risk areas or in areas where avian influenza has been confirmed).
• REPORT cases of HPAI in all animal species, including unusual hosts, to WOAH through its World Animal Health Information System (WAHIS). Genetic sequences of avian influenza viruses should be shared in publicly available databases. 
• CONSIDER poultry vaccination as complementary avian influenza control measure;  PREVENT the introduction and spread of the disease by implementing strict biosecurity measures in livestock holdings, in particular in milking parlour and EMPLOY good production and hygiene practices when handling animal products. Raw milk or raw milk products from HPAI infected cows or exposed to those infected with HPAI should not be used to feed animals or for human consumption.
• PROTECT  humans in close contact with or handling sick cattle or other sick livestock and their products. Exposed humans should always take precautionary measures to avoid getting infected and minimize the risk to mechanically carry the virus that could infect livestock or companion animals. This should include wearing personal protective equipment, avoiding visiting other livestock premises after the exposure and implementing standard food safety measures when handling animal products from exposed livestock.  
• AVOID implementing unjustified trade restrictions. Import risk management measures should be scientifically justified and in line with the WOAH International Standards.

Technical guidelines for the adaptation of diagnostic tests for Influenza A in animals including cattle and other species as well as different types of samples such as milk and nasal swabs are available in the OFFLU website and will be regularly updated.  

WOAH is fully committed to supporting its Members to mitigate the risks associated with avian influenza. We will continue to engage with our networks of experts, OFFLU,  as well as public and private partners, notably through the One Health Quadripartite and the Global Framework for Transboundary Animal Diseases (GF-TADs) to provide technical updates as more information becomes available.

Last updated: 09July 2026

What is Lumpy skin disease (LSD)?

Lumpy skin disease is a highly host-specific and causes diseases only in cattle
(Bos taurus and Bos indicus) and water buffalo (Bubalus bubalis) and has been reported in some wild ruminants. LSD virus belongs to the family Poxviridae, subfamily Chordopoxviridae, and genus Capripoxvirus.  

The disease in cattle is characterised by fever, nodules on the skin, mucous membranes and internal organs, emaciation, enlarged lymph nodes, oedema of the skin, decreased fertility, and in some cases may result in death. The disease’s characteristic cutaneous nodules typically develop on the head, neck, udder, scrotum, vulva and perineum, within 48 hours of onset of the febrile reaction, and between
7 and 19 days after infection with the virus.  

These nodules are generally well circumscribed, firm, flat-topped papules and nodules, and involve the dermis and epidermis. They can extend to the subcutis layer of the skin and, occasionally, to adjacent muscle. The nodules range from 0.5cm and 5cm in diameter and tend to contain a tissue that is creamy-grey to white in colour on cut section, which may exude serum.

With time, the nodules can either regress or result in hard, cone-shaped, necrotic tissue called “sit-fasts” that separate from the surrounding skin. These sit-fasts typically slough and leave ulcers which eventually heal and scar. Superficial lymph nodes become swollen, and swelling can develop in the udder, on the chest and on the legs. In lactating cattle there is a marked reduction in milk yield. 

The morbidity rate of LSD varies between 10-20% and mortality rates are generally low (1-5%). However, beyond animals’ well-being concerns, farmers can suffer significant economic losses from LSD and associated loss of trade, from decreased milk production, weight loss, infertility as well as damaged hides in infected cattle. 

Further information is available in the disease card developed by our Collaborating Centre on Day-One Veterinary Competencies and Continuing Education.

How is LSD transmitted? 

Transmission of LSD virus (LSDV) is thought to be predominantly by blood-feeding arthropods (i.e. biting flies, mosquitoes and ticks). Direct contact with an infected animal is considered to play a minor role in the transmission of the virus. It is not known if transmission can occur via fomites, for example ingestion of feed and water contaminated with infected saliva, but the occurrence of newly detected recombinant field strains suggests these routes may be at play.  

Incidence of LSD infection is higher in times when vectors are more active (i.e. warmer temperatures). The movement and trade of infected livestock is the primary way LSDV spreads over long distances. However, because LSD is a vector-borne disease (a disease spread by biting insects), LSD can also be spread over long distances by wind transporting insects carrying the virus. 

Lumpy skin disease virus is quite stable and can be present in skin lesions for up to
35 days. The virus can be shed though nasal and lacrimal secretions, milk and semen – surviving up to 11 days in milk and up to 22 days in semen. However, there is no evidence of LSDV being present in the meat from infected animals.  

Historically, LSD infection has been concentrated in southern and eastern Africa, however since 2000, it has been seen in the Middle East, the Balkans, Bangladesh, China and Europe. The disease has not yet been reported in the Western Hemisphere or in Australia and New Zealand. As recently as July 2025, Italy and France reported their first ever occurrences of the disease, marking a change in the distribution of the virus and highlighting the need for heightened global disease surveillance and coordination. 

Evidence from the recent LSD epidemic in Europe and western Asia has revealed that successful control and eradication of LSD relies on biosecurity, early detection and movement control, followed by rapid and widespread vaccination with high quality vaccines. Given the transboundary character of the disease,
cross-border collaboration is essential for its control and prevention. 

The World Organisation for Animal Health (WOAH) urges its Members who use vaccinations to control LSD to use high quality vaccines that have been made in line with WOAH standards. For vaccine quality control, WOAH can facilitate contact with WOAH Reference Laboratories in South Africa and the UK as well as a collaborating Centre in Belgium (Validation, Quality Assessment and Quality Control of Diagnostic Assays and Vaccine for Vesicular Diseases in Europe). 

For more detailed information regarding safe international trade in terrestrial animals and their products, please refer to the chapter on LSD in the latest edition of the WOAH Terrestrial Animal Health Code.

Zoonotic potential: are humans at risk?

LSD is not a zoonotic disease, so, humans are not at risk of infection from the disease. This means it poses no threat to human health, whether through direct contact with infected animals or through the consumption of animal products such as milk or meat. However, people who depend on cattle for food and for their livelihoods could face significant economic losses due to the lowered milk production, weight loss and hide scarring associated with the disease.