SWELSIEKTE-The role of Blood Proteins.

Thursday, 13th October 2016

SWELSIEKTE-The role of Blood Proteins.

Dr Mackie Hobson (SAMGA)

The first cases of swelling disease in South African Angora goats have been reported during the early 1970’s.  A number of trials have been conducted to investigate the cause of this disease over the subsequent years. However, no conclusive evidence had been found as far as the cause of the disease. 

 

Swelling disease, ‘swelsiekte’ in Angora goat is  the acute onset of severe subcutaneous oedema (fluid) of the lower body parts ventral neck, chest and abdomen, front and hind legs, especially over the joints and sometimes the lower jaw. However, the scrotum and udder are never affected (Bath and Vermeulen 1988)

The swelling is cold, pitted, painless and variable in intensity in different parts of the body. Fluid flows freely if the skin is cut or punctured. The fluid is clear, copious and non-clotting.

 

It is quite clear from a number of trials and studies that a low Total Plasma Protein (TSP) and Albumin (Alb) is the most consistent finding along with elevated Total white cell counts.

 

In 2015 the South African Mohair Growers Association (SAMGA) Veterinarian sampled 3 outbreaks of ‘Swelsiekte’ on 3 different farms under different conditions.

The 3 outbreaks occurred:

  • Young ewes grazing on the veld,
  • Old ewes kraaled during cold weather
  • Young ewes grazing on Lucerne lands.

10 goats with ‘Swelsiekte’ and 10 without were sampled from each group.

  (Total 60: 30 Swelling and 30 Non-swelling goats. Data arranged in ascending order Swelling goats and descending order for Non-Swelling order in graphs.)

 ALBUMIN

From these graphs it is clear that there if a definitive difference in the TSP and Albumin levels between goats that have ‘Swelsiekte’ and those that don’t.

It appears that there may be a level of oncotic pressure (TSP/Alb) at which the Angora goats compensatory mechanism are no longer able to cope and at which the Swelling occurs.

 

As any farmer will know that when catching out 60 Angora goats there is some likelihood that there may be some overlap ‘grey area’ between those goats with ‘swelsiekte’ and those without.

 

These results confirm previous findings within previous trials:

  • Bath (1983),Vermeulen (1984) ,Bath & Vermeulen (1988) and De Wet & Bath (1994)

The plasma of oedematous goats showed a lower total protein concentration, a lower colloid osmotic pressure, lower plasma albumin levels and a lower albumin: globulin ratio than that of normal goats.

  • Mitchel, Hattingh,Ganhoa (1983) suggested that oedema was primarily due to:

Hypoprotemia as well as a higher capillary permeability.

  • Vermeulen (1986) Experiments were conducted where Angora goats were infected with Ostertagia circumcincta (Brown stomach worm) larvae at varying doses.

In all trials, all goats infected with Ostertagia circumcincta had a reduced plasma protein level.             However, some stress inducing condition is necessary for the goat to develop  swelling disease. The low TPP values were most noticeable just before, during and after the swelling.

  • M.Snyman & A. Snyman (2005)‘The role of Brown stomach worm (Ostertagia circumcincta), coccidiosis and dietary protein level in the development of swelling disease in Angora goat kids’ concluded:

Goats that did develop moderate oedema had lower TPP levels throughout the experimental period.

  • Vermeulen indicated swelling to be complex as not all cases of swelsiekte had low protein levels or a high parasiteamia. Where swelsiekte did occur it developed when the goats blood protein levels were at their lowest point.

 

What is the cause of the low TSP/Albumins in the blood?

The cause of the low oncotic pressure in Swelling disease in Angora goats is unknown and seems a number of variable causes may be involved?

Research needs to be conducted as to differentiate between trans-capillary and pre-capillary membrane loss of blood proteins.

 

What can be done while the cause is unknown?

In the short term trials have indicated that feeding a high protein diet does help reduce the incidence of Swelsiekte. (M.Snyman & A.Snyman 2005)

  

  • Total plasma protein concentration (TPP) of goats on the high and normal protein diets over the experimental period

 

  • Total plasma protein concentration (TPP) of goats which developed moderate, little or no oedema during the experimental period

 

What is Albumin?

Albumin is not stored by the body and is a protein produced by the liver. Approximately 60% of it is located in the extravascular space. Albumin has a strong negative charge allowing it to be very soluble in water.

 

What does Albumin do?

One of the functions of albumin is to maintain intravascular oncotic (colloid osmotic) pressure

In addition to maintaining colloid oncotic pressure, albumin also facilitates transportation of substances. The presence of many surface-charged groups and many specific binding sites, both ionic and hydrophobic, allow albumin to bind and transport a large number of compounds. These substances include bilirubin ( goats with swelling have been found to have raised bilirubin levels), metals, ions, enzymes, amino acids, hormones, free fatty acids, drugs, and phospholipids. Albumin functions as a free-radical scavenger.

 

What role does stress play in Albumin levels?

Overall, the picture in the stress response is:

  1. Initial decrease in albumin associated with increase in acute phase proteins.
  2. Subsequent global increase in hepatic protein synthesis; including albumin

 

What can cause low albumin levels?

Snyman and Herselman (2004) suggested that any condition / factor that contributed to a lowered blood albumin level, could be a predisposing factor for swelling disease.

The following factors could all contribute to a lowered blood albumin level, and indirectly to the development of swelling disease:

 Protein deficiency – reduced production of plasma proteins

  • Low quality feed (low digestibility, low % crude protein)
  • Low feed intake (only irrigated pastures – too high moisture content of feed)
  • Low protein absorption from the intestines (intestine mucosa damaged by parasites or coccidia)
  • Interference with metabolism of plasma proteins

Other potential causes of decreased synthesis include liver disease - The mechanisms responsible for the decreased albumin levels seen in most cases of hepatocellular disease include

(a)  Increased immunoglobulin levels;

(b) third-space loss (extravasation into the extravascular space) and

(c) Direct inhibition of synthesis by toxins

 Increased protein loss

  • Physiological protein loss:  Mohair production

Loss through intestinal tract - loss of albumin does not generally cause concern   unless the loss is excessive or long lasting.

            Loss through urine

            Pregnancy

  • Increased permeability of capillary membranes:  Allergic conditions, Infectious diseases
  • Internal parasites: Brown stomach worm (Ostertagia circumcincta) Wire worm (Haemonchus contortus) Coccidiosis, Conical fluke (Paramphistomum)-(E.Snyman 1988)
  • External parasites: Ticks, Blue lice,Blood parasites

Any stress inducing condition

  • Weaning
  • Shearing
  • Dipping, castrating

Redistribution:

  • Haemodilution

For the most part, the minor decreases in albumin concentration attributable to dilution alone do not seem to result in clinical consequences.

  • Increased capillary permeability (leakage into the interstitium)
  • Decreased lymph clearance.

Inflammatory process -The most common cause of decreased plasma albumin levels is related to inflammatory processes (ie, acute-phase response and chronic inflammatory disorders). “Capillary leak syndrome”

 

The potential causes of swelling disease in Angora goats are potentially multiple and even in human medicine oedema is still not fully understood with Starling’s having now be questioned.

 

Dr Mackie Hobson

 

 

REFERENCES:

The role of Brown stomach worm (Ostertagia circumcincta), coccidiosis and dietary protein level in the development of swelling disease in Angora goat kids. M.A. Snymana * & A.E. Snyman

 

Vermeulen SO 1986    Die etiologiese rol van bruinmaagwurm (Ostertagia circumcincta) ten opsigte van swelsiekte by Angorabokke          Karoo Agric, Vol 3, No 7, 1986, 45-50

 

Snyman MA, Herselman MJ    2004    Investigation into the probable cause, predisposing factors and effective treatment of swelling disease in Angora goats  The Angora Goat an Mohair Journal, 46(1) : 27-37

 

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