SWELLING DISEASE (Swelsiekte)-The role of the Blood Proteins
By Dr Mackie Hobson BSc(Agric),BVSc

1. Diseases
2. Field Studies

The first cases of swelling disease in South African Angora goats were reported during the early 1970s.  A number of trials have been conducted to investigate the cause of this disease over the subsequent years.

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

These results were again reflected in 2015 when the South African Mohair Growers Association (SAMGA) Veterinarian (M.Hobson) sampled 3 outbreaks of ‘Swelsiekte’ on 3 different farms.

• 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.  It must be noted that when catching out swelling goats that there is likely to be a ’grey’ area of overlap.

The graph below compares the Albumin and TSP levels of goats with swelling disease compared to goats without swelling in the same flocks (n=60)

BLUE Dots: Goats with swelling

ORANGE Dots: Goats without swelling

The scatter pattern of these results clearly shows that the Swelling ‘Swelsiekte’ Angora goats have lower Albumin and lower TSP levels in the graph below compared to non-swelling goats in the same flocks.

Graphs: Values arranged in ascending order for Swelling goats and descending order for Non-swelling. 

Total Serum Proteins (TSP) and Albumin findings from these outbreaks can be summarised as follows:

 Average TOTAL SERUM PROTEINS (TSP) g/l

• SWELLING Goats (n=30) ave: 47.7g/l
• NON-SWELLING Goats (n=30) ave: 72.34g/l

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 lower albumin: globulin ratio than that of normal goats.

• Mitchel, Hattingh, and Ganhoa (1983) suggested that oedema was primarily due to Hypoprotemia and 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 parasitaemia. Where swelsiekte did occur, it developed when the goat's 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 not fully understood. It seems a number of variable causes may be involved?

The Inflammatory process leading to a capillary leak is considered the most likely cause.

SWELLING DISEASE (Swelsiekte)- Role of the inflammatory process

https://www.angoras.co.za/article/swelsiekte-possible-role-of-the-inflammatory-process

SWELLING DISEASE (Swelsiekte)- Capillary leak Syndrome

https://www.angoras.co.za/article/swelsiekte-swelling-disease-in-angora-goats

How does a protein diet effect total plasma proteins?

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 can cause low albumin levels?

Snyman and Herselman (2004) suggested that any condition/factor contributing 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:

1. 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 the metabolism of plasma proteins

2. Decreased synthesis

• include liver disease - The mechanisms responsible for the decreased albumin levels seen in most cases of the hepatocellular disease include:

(a)  Increased immunoglobulin levels;

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

(c) Direct inhibition of synthesis by toxins

3. 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), Wireworm (Haemonchus contortus), Coccidiosis, Conical fluke (Paramphistomum)-(E.Snyman 1988)
• External parasites: Ticks, Blue lice, Blood parasites

4. Any stress-inducing condition

• Weaning
• Shearing
• Dipping, castrating

5. 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.

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

SEE:  Mohair Articles:

 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 the 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. The initial decrease in albumin is associated with an increase in acute-phase proteins.
2. The subsequent global increase in hepatic protein synthesis; including albumin

The potential causes of swelling disease in Angora goats are potentially multiple and is still not fully understood although an inflammatory response leading to a capillary leak syndrome is suspected leading to a drop in oncotic pressure is suspected.

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 and Mohair Journal, 46(1): 27-37