University of Veterinary Medicine

Scent detection dogs helping sniff out the causes of long COVID

Trained sniffer dogs are able to detect post-COVID syndrome (long COVID) by scent. In their ‘Dogolomics’ project, a team of researchers in human and veterinary medicine is seeking to track down the causes of long COVID by finding out which substances the dogs can smell. They thus aim to pave the way for improved detection of this difficult-to-diagnose condition.

Dog — Coronavirus detection dogs able to sniff out long COVID as well.

The causes of post-COVID syndrome (long COVID) remain unknown. Given that medical sniffer dogs trained to detect coronavirus are able to distinguish between samples from subjects with and without long COVID, a team of researchers from three institutions – University of Veterinary Medicine Hannover (TiHo), Hannover Medical School (MHH) and Technische Universität Braunschweig – are looking into which substances the dogs are detecting. The team’s objective is to clarify whether it is viral residues or altered metabolic processes that are involved in the development of long COVID. A project called ‘Detecting and Deciphering post COVID with Dogs, Metabolomics and Machine Learning (COVID Dogolomics)’ is part of the current round of funding being sought under Lower Saxony’s COVID-19 research network (COFONI). As of 1 July 2023, COFONI is funding 14 interdisciplinary collaborative projects in the state to the tune of more than seven million euros, the aim being to investigate the long-term impact – both medical and societal – of the SARS-CoV-2 pandemic. These resources for the above research programmes are being provided by Lower Saxony’s Ministry of Science and Culture (MWK).

Dogs sniff out people infected with SARS-CoV-2

More than one year ago, a team from TiHo’s Department of Small Animal Medicine and Surgery published a study showing that dogs can identify samples taken from long-COVID patients. These dogs had undergone prior training using samples from individuals infected with SARS-CoV-2, and indicated these samples to a high degree of accuracy. It is likely that the animals do not smell the viruses themselves, but volatile organic compounds (VOCs) instead, formed by metabolic processes during viral infection. “Although we have not yet unravelled the mechanism of how dogs can detect coronavirus so precisely by scent, we’re sure that they will help us to explain long COVID more fully, and hence improve diagnostics going forward.”

Attempt to understand long COVID by applying a unique approach

“Dogolomics will benefit greatly from our ‘DEFEAT Corona’ project, which has already enabled us to reach and examine many people with long COVID,” says Professor Alexandra Dopfer-Jablonka of MHH’s Department of Rheumatology and Immunology. Her colleague, Professor Georg Behrens, adds: “We’re excited and proud to be part of a tremendous team from Lower Saxony in which we can all pool our experience and expertise. We want to join forces to get to the bottom of the challenging phenomenon that is long COVID, and to adopt a quite unique approach in doing so.”

Diagnosing long COVID: a complex challenge

Long COVID is complex and difficult to diagnose. More than 200 symptoms, affecting several different organ systems, have been identified under this heading. These include fatigue, muscle or joint pain, confusion, ‘brain fog’ and depression. Symptoms resemble those of chronic fatigue syndrome (CFS) and Sjögren’s syndrome. The fact that all three conditions have unspecific symptoms makes them even harder to diagnose and distinguish. A more clear-cut diagnostic method would be beneficial for sufferers. And so the research team is seeking to find out whether dogs trained to detect coronavirus by scent can distinguish between the three syndromes based on samples, and tell sufferers apart from healthy control subjects.

Thanks to other research projects already underway, the interdisciplinary team is able to draw from well-defined cohorts of patients with long COVID, Sjögren’s syndrome and CFS. The aim is to elucidate the central olfactory structure in post-COVID syndrome, as identified by dogs. To this end, the investigators will isolate and examine all relevant metabolic products (in a discipline known as metabolomics). They will subsequently allow the dogs to detect individual molecules, or combinations, as compared to real-world biological samples. If the molecules involved were known, it would be possible to identify ‘unprogrammed’ metabolic pathways in long-COVID sufferers. This could pave the way for rapid and reliable diagnosis.