Equine Internal Medicine Q&A 16

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A nine-week-old Arabian foal is presented with a history of recurrent respiratory infections characterized by nasal discharge, cough, dyspnoea and pyrexia. The foal was normal at birth, but suffered its first bout of respiratory disease at six weeks of age. Over the previous week it had also developed widespread scaling and alopecic skin lesions, from which Dermatophilus congolensis had been cultured. The foal has also had intermittent diarrhoea. Haematological evaluation revealed a severe lymphopenia (lymphocyte count 0.2x109/l).

Question	Answer		Article
What is the most likely diagnosis?	Combined immunodeficiency syndrome (CID).		Link to Article
How could you confirm this?	Serum IgM will be extremely low or undetectable. The lymphopenia will be persistent. Lymphoid hypoplasia, including the thymus, spleen and lymph nodes, will be evident at post-mortem examination.		Link to Article
What is the aetiology of this disease?	CID is a genetic disorder of foals of Arabian breeding that results in failure to produce functional B and T lymphocytes. The disease is inherited as an autosomal recessive trait, and heterozygous individuals show no signs. Affected foals are usually normal at birth, and signs of infection (especially respiratory infections and pneumonia) become evident at any time between two days and two months depending on the level of passively acquired colostral immunity.
What are the usual causes of the respiratory infections in this disease?	Pneumonia caused by adenovirus, Pneumocystis carinii and a variety of bacteria are commonly involved.		Link to Article
How would you treat this foal?	There is no recommended treatment for CID. Bone marrow transplantation has been performed successfully in one affected foal.		Link to Article