Changes

{{review}}

{{OpenPagesTop}}

 

Also known as: '''''Equine SCID — ESCID

Also known as: '''''Equine SCID — ESCID

SCID occurs due to a mutation in the allele encoding for DNA-dependent protein kinase (DNA-PK) that is involved in V(D)J lymphocyte recombination. V(D)J recombination is required for antigenic receptor expression on B and T lymphocytes. Without these receptors, differentiation of B and T lymphocytes does not occur and lymphoid tissue fails to develop. The result of this mutation is a severe immunodeficiency.  

SCID occurs due to a mutation in the allele encoding for DNA-dependent protein kinase (DNA-PK) that is involved in V(D)J lymphocyte recombination. V(D)J recombination is required for antigenic receptor expression on B and T lymphocytes. Without these receptors, differentiation of B and T lymphocytes does not occur and lymphoid tissue fails to develop. The result of this mutation is a severe immunodeficiency.  

==Clinical signs==

==Clinical Signs==

Affected foals are clinically normal at birth and usually develop infections at around two to three months of age due to declining maternal antibodies in the colostrum. The most common clinical signs relate to infections of the respiratory tract such as nasal discharge, cough, dyspnoea or increased respiratory sounds. Other clinical signs may reflect further sites of infection including intermittent fever, pneumonia, colic, weight loss and diarrhoea. Infection of the pancreas may result in loss of functional endocrine tissue leading to stunted growth and weight loss.  

Affected foals are clinically normal at birth and usually develop infections at around two to three months of age due to declining maternal antibodies in the colostrum. The most common clinical signs relate to infections of the respiratory tract such as nasal discharge, cough, dyspnoea or increased respiratory sounds. Other clinical signs may reflect further sites of infection including intermittent fever, pneumonia, colic, weight loss and diarrhoea. Infection of the pancreas may result in loss of functional endocrine tissue leading to stunted growth and weight loss.  

==Diagnosis==

==Diagnosis==

Diagnosis may not be straightforward as the clinical signs may resemble those of many other infections occurring in foals. The antemortem diagnosis of SCID is usually based on three criteria; a) a persistent lymphopaenia (occurring over 1-2 weeks) with less than 1000 lymphocytes per ml, b) a lack of serum IgM in foals over four weeks of age and c) lymphoid hypoplasia. Affected foals may also develop [[Anaemia - Introduction|anaemia]] late in the course of the disease.  

Diagnosis may not be straightforward as the clinical signs may resemble those of many other infections occurring in foals. The antemortem diagnosis of SCID is usually based on three criteria; a) a persistent lymphopaenia (occurring over 1-2 weeks) with less than 1000 lymphocytes per microlitre, b) a lack of serum IgM in foals over four weeks of age and c) lymphoid hypoplasia. Affected foals may also develop [[Regenerative and Non-Regenerative Anaemias|anaemia]] late in the course of the disease.  

The '''intradermal phytohemagglutinin (PHA) test''' may be used as a test for immunocompetence and assesses T lymphocyte function. It can be performed in foals of all ages as the test is not affected by maternal antibodies. Intradermal PHA causes a [[Type IV Hypersensitivity|delayed hypersensitivity]] reaction, resulting in a skin swelling. A foal suffering from SCID fails to respond to intradermal PHA.  

The '''intradermal phytohemagglutinin (PHA) test''' may be used as a test for immunocompetence and assesses T lymphocyte function. It can be performed in foals of all ages as the test is not affected by maternal antibodies. Intradermal PHA causes a [[Type IV Hypersensitivity|delayed hypersensitivity]] reaction, resulting in a skin swelling. A foal suffering from SCID fails to respond to intradermal PHA.  

SCID may be prevented in foals by DNA testing of the mare and stallion and only breeding non-carrier animals.  

SCID may be prevented in foals by DNA testing of the mare and stallion and only breeding non-carrier animals.  

==Literature Search==

[[File:CABI logo.jpg|left|90px]]

|flashcards = [[Equine Internal Medicine Q&A 16]]

 

|literature search =[http://www.cabdirect.org/search.html?start=0&q=title:(%22Equine+Severe+Combined+Immune+Deficiency%22)+OR+((title:(%22Severe+Combined+Immune+Deficiency%22)++OR+title:(SCID))+AND+od:(horses))+OR+title:(ESCID) Equine Severe Combined Immune Deficiency publications]

 

[http://www.cabdirect.org/search.html?start=0&q=title:(%22Equine+Severe+Combined+Immune+Deficiency%22)+OR+((title:(%22Severe+Combined+Immune+Deficiency%22)++OR+title:(SCID))+AND+od:(horses))+OR+title:(ESCID) Equine Severe Combined Immune Deficiency publications]

==References==

==References==

*McClure, J. T. (1997) '''New Developments in Severe Combined Immunodeficiency Disease''' ''Proceedings of the Annual Convention of the AAEP (43) pp61-64''

*McClure, J. T. (1997) '''New Developments in Severe Combined Immunodeficiency Disease''' ''Proceedings of the Annual Convention of the AAEP (43) pp61-64''

*Swinburne, J., Lockhart, L., Scott, M., Binns, M. M. (1999) '''Estimation of the prevalence of Severe Combined Immunodeficiency Disease in UK Arab horses as determined by a DNA-based test''' ''The Veterinary Record 145 22-23''

*Swinburne, J., Lockhart, L., Scott, M., Binns, M. M. (1999) '''Estimation of the prevalence of Severe Combined Immunodeficiency Disease in UK Arab horses as determined by a DNA-based test''' ''The Veterinary Record 145 22-23''

[[Category:Primary Adaptive Immunity Deficiencies]]

[[Category:Primary Adaptive Immunity Deficiencies]]

 

[[Category:Expert Review - Horse]]

[[Category:Expert Review]]

[[Category:Immunological Diseases - Horse]]

[[Category:Horse]]