RaDiCal: Rapid diagnosis of Calf Pneumonia

We shall develop a rapid, sensitive, cost-effective on-farm diagnostic test capable of detecting the organisms responsible for calf pneumonia to inform herd management and reduce the unnecessary use of antibiotics. Early diagnosis of pneumonia will allow the farmer to administer treatment in a proportionate and timely way.

Calf pneumonia is a complex disease caused by a variety of infectious agents. Typically, the clinical disease is caused by certain species of bacteria that may normally cause no adverse effects to the lungs but do so when the animal is compromised in some way, such as a specific viral infection in combination with other stress factors, such as weaning, changes of feed, variation in ambient temperature and humidity. The estimated lifetime economic cost of a case of pneumonia in a dairy heifer is £772, highlighting the potential returns from investing in reducing the impact of this disease. Despite the substantial cost that calf pneumonia causes the UK cattle industry, most farmers prefer to reduce the likelihood of the disease occurring or rely on detecting pneumonia through non-specific means. That is not to say that diagnostic tests are not available, but the high cost of tests and the fact that the results are delayed and therefore cannot inform treatment decisions are likely reasons why these are not used routinely. We intend to understand the impediments to livestock diagnostic test use in more detail in this project through engagement with farmers, vets, and calf rearers.

Recent developments in rapid molecular diagnostics (many by the project team) offer the possibility of delivering a test that is considerably cheaper, quicker and more sensitive than existing commercial tests, opening up the opportunity to use such a test for routine surveillance on-farm. This would enable early intervention and the development of specific treatment protocols, thus reducing antimicrobial resistance and improving calf welfare. Our project sits at the intersections between policy change, economic opportunity, changing practice, public perception of the industry, and even antibiotic stewardship.

We are a new and focused partnership that combines working knowledge of dairy farming, expertise in veterinary infectious disease, diagnostic test development and stakeholder engagement methods. The test will be based on simultaneous detection of any of the six most common infections associated with calf pneumonia using a simple swab of the nasal passages, not unlike the current lateral flow tests for COVID-19. The swab will be placed in a novel device developed by the project partners that gives a simple final readout of the test result using a lateral flow device. Proof of principle has been demonstrated for the technology we intend to adopt for the detection of at least some of the pathogens associated with calf pneumonia, and three of the partners have experience of the development of rapid tests using this technology for pathogens of veterinary importance, and respiratory infectious disease testing in humans (incl. COVID-19).

However, developing a test is only half the story, and we must ensure the test is co-developed with those who will ultimately use it. One of the partners is a dairy farmer, another a livestock veterinarian, and two others have worked with calf rearers for the last five years on pneumonia management and antibiotic resistance. Using methods, such as interviews/workshops with calf rearers and vets, we shall ask questions such as, how do you currently control pneumonia, how quick does the test need to be from start to result, how much should it cost, which sales channel is most attractive, and what will you do differently in response to the test result? This will be vital information to ensure the test we develop has the best chance of being used on farm to the benefit of animal health and welfare, the GB cattle industry, and beyond.

We shall develop a rapid, sensitive, cost-effective on-farm test to diagnose pneumonia, to 1) inform herd management; 2) mitigate the economic cost caused by the long-term of damage of pneumonia on productivity; and 3) reduce the unnecessary use of antibiotics through better, evidence-based prescribing.

Calf pneumonia is a 'disease complex', caused by co-infection with a variety of pathogens, together with other environmental/stress factors, such as weaning, variation in temperature and humidity. The estimated lifetime economic cost of a case of pneumonia in a dairy heifer is £772, highlighting the potential returns from investing in reducing the impact of this disease. Despite the substantial cost that calf pneumonia causes the UK cattle industry, most farmers prefer to reduce the likelihood of the disease occurring or rely on detecting pneumonia through non-specific means. That is not to say that specific diagnostic tests are not available, but there are reasons why farmers are not using them routinely. We intend to understand the impediments to diagnostic test use in more detail through engagement with farmers and calf rearers.

Recent developments in rapid molecular diagnostics, including loop-mediated isothermal amplification (LAMP), have opened the possibility of rapid, on-farm diagnosis of calf pneumonia using nasal swabs. Drawing on the complementary skills of our new partnership, the test will be co-developed through stakeholder engagement in a virtuous circle and technically, will combine novel sample preparation/DNA extraction in a disposable cartridge with readout on a lateral flow device (LFD) with preliminary validation data, and be the first to combine simultaneous detection of bacteria and DNA viruses from clinical samples to aid diagnosis. Coupling the LFD readout to smartphone AI-based, on-farm decision support will allow for early intervention and the application of specific, better informed treatment protocols.