Equine grass sickness (EGS) presents a
diagnostic challenge. The best way to confirm the diagnosis is by finding
characteristic signs in biopsies of the small intestine.
However this entails general anaesthesia and abdominal surgery, making it expensive. Other tests have been used to try to throw light on the diagnosis, such as the response to phenylephrine eye drops.
However this entails general anaesthesia and abdominal surgery, making it expensive. Other tests have been used to try to throw light on the diagnosis, such as the response to phenylephrine eye drops.
Blood samples are easy to collect and
blood tests may help narrow down the diagnosis in some cases of suspected grass
sickness.
Horses with equine grass sickness may show signs of systemic inflammation. One way of identifying this is to look for acute phase proteins (APPs) in the blood. As their name suggests these are proteins that increase in concentration in the blood in the early stages of an inflammatory response.
For example, previous research has shown that α-2 macroglobulin levels are higher in acute EGS compared with normal horses or those with colic or with chronic grass sickness. Higher concentrations of ceruloplasmin were found in cases of acute EGS or colic, compared with chronic EGS cases and normal horses.* However, these APPs are not usually tested routinely in equine practice.
On the other hand, fibrinogen and SAA are widely used in equine practice as inflammatory markers, and recent research has looked at whether measuring them could aid the diagnosis of grass sickness.
Researchers at Liphook Equine Hospital and the Royal (Dick) Vet College tested serum samples from 40 horses with EGS and compared them with 20 healthy horses, including those grazing the same pasture, and eight horses with colic due to causes other than EGS.
They found a marked increase in serum amyloid A (SAA) and fibrinogen in horses with EGS, and in horses with inflammatory colic, such as peritonitis, enteritis or colitis, compared with healthy horses, co-grazers and horses with colic due to non-inflammatory causes, such as intestinal obstruction.
There was no significant difference in SAA levels between horses with EGS and those with an inflammatory colic.
Interestingly they also found concentrations of another APP, Activin A, were significantly increased in both EGS cases and co-grazing horses. They suggest that this might indicate the presence of sub-clinical disease in the co-grazers.
In a report of the work which was published in the Veterinary Record, Victoria Copas and co-workers suggest that a marked increase in fibrinogen and SAA concentrations may help differentiate cases of EGS from other causes of abdominal pain (such as simple colon obstructions or intestinal strangulations) when considered in conjunction with signalment, historical data, clinical findings and results of other ancillary diagnostic tests.
However, they emphasise that doing so would not help differentiate between EGS and other inflammatory abdominal conditions – such as peritonitis or enteritis.
*Acute phase proteins in grass sickness (equine dysautonomia).
Milne EM, Doxey DL, Kent JE, Pemberton A.
Res Vet Sci. 1991 May;50(3):273-8.
Horses with equine grass sickness may show signs of systemic inflammation. One way of identifying this is to look for acute phase proteins (APPs) in the blood. As their name suggests these are proteins that increase in concentration in the blood in the early stages of an inflammatory response.
For example, previous research has shown that α-2 macroglobulin levels are higher in acute EGS compared with normal horses or those with colic or with chronic grass sickness. Higher concentrations of ceruloplasmin were found in cases of acute EGS or colic, compared with chronic EGS cases and normal horses.* However, these APPs are not usually tested routinely in equine practice.
On the other hand, fibrinogen and SAA are widely used in equine practice as inflammatory markers, and recent research has looked at whether measuring them could aid the diagnosis of grass sickness.
Researchers at Liphook Equine Hospital and the Royal (Dick) Vet College tested serum samples from 40 horses with EGS and compared them with 20 healthy horses, including those grazing the same pasture, and eight horses with colic due to causes other than EGS.
They found a marked increase in serum amyloid A (SAA) and fibrinogen in horses with EGS, and in horses with inflammatory colic, such as peritonitis, enteritis or colitis, compared with healthy horses, co-grazers and horses with colic due to non-inflammatory causes, such as intestinal obstruction.
There was no significant difference in SAA levels between horses with EGS and those with an inflammatory colic.
Interestingly they also found concentrations of another APP, Activin A, were significantly increased in both EGS cases and co-grazing horses. They suggest that this might indicate the presence of sub-clinical disease in the co-grazers.
In a report of the work which was published in the Veterinary Record, Victoria Copas and co-workers suggest that a marked increase in fibrinogen and SAA concentrations may help differentiate cases of EGS from other causes of abdominal pain (such as simple colon obstructions or intestinal strangulations) when considered in conjunction with signalment, historical data, clinical findings and results of other ancillary diagnostic tests.
However, they emphasise that doing so would not help differentiate between EGS and other inflammatory abdominal conditions – such as peritonitis or enteritis.
*Acute phase proteins in grass sickness (equine dysautonomia).
Milne EM, Doxey DL, Kent JE, Pemberton A.
Res Vet Sci. 1991 May;50(3):273-8.