SAA spots infectious respiratory disease

Many horses with nasal discharge do not require antimicrobial treatment, according to a recent study into infectious and non-infectious respiratory disease in horses.

Knowing whether the disease is caused by infection or is an inflammatory condition resulting from environmental factors helps guide treatment and management. Infectious diseases may require additional measures to prevent spread of the disease to other animals.

In some cases, the involvement of infection may be obvious. Disease affecting more than one horse might suggest infection but could be the result of common environmental factors. Fever would be a good indication of infection, although it may be missed if transient.

Research by Dr Molly Viner and colleagues suggests that Serum Amyloid A (SAA) is a reliable marker for infectious respiratory disease.

SAA is an acute phase protein - a group of serum proteins that are produced early in the body’s response to inflammation. Very low levels are found in healthy horses, but they rise dramatically in animals with severe inflammation.

SAA is a useful marker of inflammation as it increases rapidly in the early stages of inflammation and falls rapidly once the inflammation subsides.

The researchers found that SAA values greater than 52 μg /ml correctly differentiated infectious from non-infectious respiratory disease 98% of the time.

Although horses with bacterial disease tended to have higher SAA levels than did those with viral diseases, the difference was not as distinct as that between infectious and non-infectious disease.

They conclude: “SAA is more reliably elevated with infections of the respiratory tract rather than noninfectious airway conditions. This can facilitate early detection of respiratory infections, help track disease progression, and aid practitioners in making recommendations about proper biosecurity and isolation of potentially contagious horses.”

For more details, see:

Comparison of Serum Amyloid A in horses with infectious and noninfectious respiratory diseases

Molly Viner, Melissa Mazan, Daniela Bedenice, Samantha Mapes, Nicola Pusterla.

Journal of Equine Veterinary Science (2017) 49, Pages 11–13

DOI:https://doi.org/10.1016/j.jevs.2016.09.005

For a video of Dr Viner discussing her findings, go to:

https://www.stablelab.com/pages/the-coughing-horse

Horses can read and remember human facial expressions

Horses can remember emotional expressions that they’ve seen on human faces and adjust their subsequent behaviour accordingly, recent research has revealed.  What’s more, this memory for emotions is specific to the person concerned.

Researchers, led by Professor Karen McComb from the University of Sussex and Dr Leanne Proops from the University of Portsmouth, presented domestic horses with a photograph of a happy or angry human face. Several hours later the horse saw the person in the photograph, this time bearing a neutral expression, in real life.

Observers noted which eye the horse used to look at the individual. Previous research has shown that animals tend to view negative or threatening events with their left eye. This is because threatening stimuli are processed in the right side of the brain.  (Information from the left eye is processed in the right hemisphere).

The researchers found that short-term exposure to the photograph of a person's facial expression was enough to generate clear differences in subsequent responses upon meeting that individual in the flesh later the same day. 

Despite the humans being in a neutral state during the live meeting, the horses' gaze direction revealed that they perceived the person more negatively if they had earlier seen them a photograph of them looking angry rather than happy.

Neither of the two humans used in the study knew which of the photographs (angry or happy) had been shown to the horse earlier in the day, to avoid any risk of behaving differently themselves.

Interestingly, the differences in reaction only applied to the person the horses had actually seen in the photograph and were not given to a different person.

Professor Karen McComb commented on the findings: "What we've found is that horses can not only read human facial expressions, but they can also remember a person's previous emotional state when they meet them later that day -- and, crucially, that they adapt their behaviour accordingly. Essentially horses have a memory for emotion."

For more details, see:

Animals Remember Previous Facial Expressions that Specific Humans Have Exhibited.

Leanne Proops, Kate Grounds, Amy Victoria Smith, Karen McComb..

Current Biology, 2018;

DOI:10.1016/j.cub.2018.03.035