Changes

==Description==

==Description==

[[Platelet|Platelets]] (or thrombocytes) are responsible for primary haemostasis, the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall.  Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia''').  Thrombocytopaenia may be a '''primary disease''', relating to a failure to produce platelets in the bone marrow, or it may occur '''secondary''' to another insult.  '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.

[[Platelet|Platelets]] (or thrombocytes) are responsible for primary haemostasis, the formation of a temporary platelet plug that initially seals any breach to a blood vessel wall.  Bleeding disorders may occur if platelets are deficient ('''thrombocytopaenia''') or if the platelets are unable to function adequately ('''thrombocytopathia''').  [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] (ITP) is one common cause of thrombocytopaenia and this may be a primary or secondary disease.  '''Thrombocytosis''' refers to an increase in the blood platelet concentration above the normal level.

 

==Thrombocytopaenia==

==Thrombocytopaenia==

Thrombocytopaenia is the most common haematological abnormality as platelet numbers are subject to fluctation in a large number of different diseases however care should be taken to ensure that this finding is not caused by an artefact of sampling.  The normal blood platelet concentration of the dog is 175-500x10^9 but clinical disease is not usually observed until this level falls below 50x10^9 and spontaneous haemorrhage is observed only when the level falls below 20x10^9.  Reductions in the number of platelets may be caused by failure to produce adequate numbers in the bone marrow in the process of megakaryopoiesis, increased destruction of existing platelets or sequestration of platelets outside of the circulation. 

The aetiology of primary thrombocytopenic disease is often uncertain and it is therefore also known as '''idiopathic''' thrombocytopaenia.  Some cases of primary thrombocytopaenia may occur due to autoimmune responses directed at platelets and, although the [[Bone Marrow - Anatomy & Physiology|bone marrow]] may contain adequate numbers of normal megakaryocytes, this disease results in a reduced peripheral blood thrombocyte count.  [[Immune Mediated Thrombocytopaenia|Immune-mediated thrombocytopaenia]] occurs most commonly in young animals.

 

Secondary thrombocyopaenic disease is fairly common in adult domestic animals and it may be associated with diseases that depress the production of platelets or increase their consumption or sequestration:

*Diseases that cause '''[[Bone Marrow - Anatomy & Physiology|bone marrow]] suppression'''

*Diseases that cause '''[[Bone Marrow - Anatomy & Physiology|bone marrow]] suppression'''

**'''Aplastic anaemia''' caused by ingestion of bracken, administration of oestrogens or of [[Chloramphenicol|chloramphenicol]] or [[Sulphonamides|sulphonamide]] antibiotics.  Prolonged use of phenylbutazone or salicylate may cause the same disease.

**'''Aplastic anaemia''' caused by ingestion of bracken, administration of oestrogens or of [[Chloramphenicol|chloramphenicol]] or [[Sulphonamides|sulphonamide]] antibiotics.  Prolonged use of phenylbutazone or salicylate may cause the same disease.

**'''Radiotherapy''' or myelosuppressive '''chemotherapy''' may cause reversible bone marrow suppression.

**'''Radiotherapy''' or myelosuppressive '''chemotherapy''' may cause reversible bone marrow suppression.

*Diseases that cause '''increased destruction of platelets'''

*Diseases that cause '''increased destruction of platelets'''

**'''Infectious diseases''' that cause destruction of platelets include [[Bovine Viral Diarrhoea Virus|bovine viral diarrhoea]], [[Classical Swine Fever|classical swine fever]] and [[Infectious Canine Hepatitis|infectious canine hepatitis]].  The parasites ''[[Ehrlichia platys]]'', ''[[Anaplasma phagocytophilum]]'' and ''[[Ehrlichia canis]]'' may also cause infectious thrombocytopaenia.  Any severe bacterial infection, including those caused by [[:Category:Staphylococcus species|''Staphylococci'']] and the Gram negative bacteria that produce endotoxin (e.g. [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas spp.'']] or [[Salmonella|''Salmonella spp.'']]) may also result in the destruction of platelets.

**'''Infectious diseases''' that cause destruction of platelets include [[Bovine Viral Diarrhoea Virus|bovine viral diarrhoea]], [[Classical Swine Fever|classical swine fever]] and [[Infectious Canine Hepatitis|infectious canine hepatitis]].  The parasites ''[[Ehrlichia platys]]'', ''[[Anaplasma phagocytophilum]]'' and ''[[Ehrlichia canis]]'' may also cause infectious thrombocytopaenia.  Any severe bacterial infection, including those caused by [[:Category:Staphylococcus species|''Staphylococci'']] and the Gram negative bacteria that produce endotoxin (e.g. [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas spp.'']] or [[Salmonella|''Salmonella spp.'']]) may also result in the destruction of platelets.

*Diseases that cause '''sequestration of platelets''' usually involve some enlargement of the spleen as this is the major organ where platelets are stored outside of the circulation.  Examples include:

*Diseases that cause '''sequestration of platelets''' usually involve some enlargement of the spleen as this is the major organ where platelets are stored outside of the circulation.  Examples include:

==Thrombocytopathia==

==Thrombocytopathia==

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Von Willebrands, Angiostrongylus, colloids, Pelger Huet anomaly?.

Von Willebrands, Angiostrongylus, colloids, familial

* A rare inherited condition.

* A rare inherited condition.

* Recorded in the dog.   

* Recorded in the dog.