Genetic Welfare Problems of Companion Animals

An information resource for prospective pet owners

Dachsund

Dachshund

Immune-Mediated Thrombocytopenia

Related terms: thrombocytopenia, autoimmune thrombocytopenia, AITP, idiopathic thrombocytopenic purpura, ITP

Outline: Long-haired dachshunds are predisposed to a disease in which the concentration of platelets in the blood is abnormally low as a result of attack, for unknown reasons, by the dog's own antibodies (whose normal role is to help guard against infections). Platelets are cells that play an essential part in the clotting system of blood and when they become scarce, the clotting system is affected leading to spontaneous bleeding into tissues (which may be apparent as blood spots in hairless and unpigmented parts of the skin) or externally (eg as nose bleeds, or blood in urine or faeces). The disease can cause chronic malaise and can cause severe pain due to pressure when bleeding is into confined spaces such as eyes, the skull or joints.


Summary of Information

(for more information click on the links below)

1. Brief description

Thrombocytes, or platelets, are cellular fragments that circulate in the blood and which are vital for blood clotting (haemostasis). Functioning platelets are necessary to prevent leakage of blood from blood vessels. The platelets plug any gaps that may occur in the inner surface of blood vessels and release substances that encourage further plug formation and its stabilization through the actions of coagulation factors (Lewis 2000a).

Thrombocytopenia is the condition in which there is a lower than normal concentration of platelets in the blood. This can happen for various reasons but most commonly in dogs, it is because of their insufficient production in the bone marrow or because the platelets are being destroyed more rapidly than usual. Destruction of platelets can be due to various infectious diseases, but the commonest cause in dogs in the UK is primary immune-mediated thrombocytopenia (IMT) (Lewis 2000b).

In immune-mediate thrombocytopenia, the dog’s own antibodies bind to the surface of the platelets triggering an immune response from the body that results in the removal of these platelet-antibody complexes from the circulation by the normal mechanisms in the liver and spleen. The reason why the antibodies bind to the platelets and cause this disease is unknown. Dogs can tolerate quite low platelet concentrations but once these drop below a critical level, they are likely to show the clinical signs of this condition.

Thrombocytopenia, regardless of its cause, results in the same problems: bleeding from small blood vessels without there having been an injury. This shows as spots of bleeding visible in the skin (only readily apparent in hairless and unpigmented areas) or in the tissues of the mouth. The blood spots in the tissues are called petechiae, when small, and purpura or ecchymoses when larger. There may also be external bleeding from the skin or, more commonly, a nosebleed or blood-tinged vomit, urine or faeces (Lewis 2000b).

Affected dogs may feel malaise and show inappetance, lethargy, and reduced strength, and they may have a fever.

Around 20% of dogs with IMT also have similar immune-mediated destruction of their red blood cells (RBCs). Further, approximately 22% of dogs with this immune mediated haemolytic anaemia (IMHA) have a severe thrombocytopenia (Carr et al 2002).

2. Intensity of welfare impact    

Affected dogs are likely to feel unwell. Around 30% of dogs with IMT die from the condition either directly from the illness or are euthanased because of it (Wilkins et al 1973, Williams & Maggio-Price 1984, Jackson & Kruth 1985, Jans et al 1990).

Some animals that respond poorly to medical treatments may respond to removal of the spleen. However, this is a major operation with significant welfare implications associated with hospitalisation and the stress and pain of the procedure itself.

3. Duration of welfare impact

Malaise and discomfort due to ITM is likely to last for days to weeks, treatment then usually lasts for weeks to months. Some animals require life-long treatment and around 40% of affected animals are likely to have recurrent bouts (Lewis 2000b).

4. Number of animals affected

We are not aware of data on the prevalence of IMT in long-haired dachshunds but it is believed that they have a particular predisposition to the disease and that certain families are especially affected (Lewis 2000b).

5. Diagnosis

Typical clinical signs raise suspicions of a platelet disease. Detection of an abnormally low blood platelet concentration is usually straightforward but determining that this is due to IMT is difficult. There is no definitive test for IMT, so the diagnosis is usually based on finding no other cause. Response to treatment can assist in confirming the diagnosis (Lewis 2000b).

6. Genetics

It is suspected that long-haired dachshunds are predisposed to IMT but, as far as we are aware, there have been no studies on the pattern of inheritance or to determine the genes involved.

7. How do you know if an animal is a carrier or likely to become affected?

It is not known if animals can pass on the disease to offspring without having developed it themselves. There are no tests to detect animals at risk or which might be carriers. Avoiding the purchase of a puppy with close relatives (parents, grandparents and the siblings of parents and grandparents) that have been affected with IMT is advisable.

8. Methods and prospects for elimination of the problem

As far as we are aware, there are currently no organised schemes aimed at reducing the prevalence of IMT in long-haired dachshunds. Although the genes involved have not been determined, selective breeding using animals with relatives that have histories of no, or of a lower than average, incidence of the condition is likely to be effective in reducing the number of affected dogs (Indrebo 2006, Bell 2010).

 

For further details about this condition, please click on the following:
(these link to items down this page)


1. Clinical and pathological effects

Thrombocytes, or platelets, are cellular fragments that circulate in the blood and which are vital for the first stage of blood clotting (haemostasis). Functioning platelets are necessary to prevent the leakage of blood from blood vessels. The platelets plug any gaps which occur in the inner surface of blood vessels and release into the blood stream substances that encourage further plug formation and its stabilization through the actions of the coagulation factors. They also release substances that encourage the ultimate healing of the wound (Lewis 2000a).

Thrombocytopenia is the condition in which there is a lower than normal concentration of platelets in the blood. This can happen for a number of reasons but most commonly in dogs, it is due to their insufficient production in the bone marrow or to platelets being destroyed. Destruction of platelets can occur in various infectious diseases but the most common cause in dogs in the UK is primary immune-mediated thrombocytopenia (Lewis 2000b). This is an idiopathic condition, ie its cause is unknown. In other parts of the world, certain infectious diseases such as ehrlichiosis and Rocky Mountain spotted fever are also important causes of thrombocytopenia (Cockburn & Troy 1986, Grindem et al 1991).

In immune-mediate thrombocytopenia the dog’s own antibodies bind to the surface of the platelets triggering an immune response from the body that results in the removal of these platelet-antibody complexes from the circulation by the normal mechanisms in the liver and spleen. Antibodies are proteins produced by the immune system which target specific disease-causing organisms or foreign material for destruction by other parts of the immune system. In IMT, the immune system malfunctions leading to abnormally high platelet destruction. The reason why the antibodies bind to the platelets and cause this disease is unknown. Dogs are able to tolerate quite low concentrations of platelets but, once they fall below a critical level, affected animals will be likely to develop clinical signs of this condition.

Thrombocytopenia, regardless of its cause, results in the same problems: bleeding from small blood vessels without there having been an injury. This shows as spots of bleeding visible in skin (only readily apparent in areas that are hairless and unpigmented) or inside the tissues of the mouth. These blood spots within the tissues are called petechiae, when small, and purpura or ecchymoses when larger. There may also be external bleeding from the skin or, more commonly, from nosebleeds or blood-tinged vomit, urine or faeces. Bleeding can occur anywhere and other sites quite commonly affected are inside the eyes and into the brain, leading to blindness or neurological signs (signs of abnormal brain function) (Lewis 2000b). Bleeding into these or other confined body cavities, such as joints, can be very painful because of the increased pressure. 

In addition to these signs, affected dogs may show signs of malaise including inappetance, lethargy and reduced strength, and they may have a fever. There may be anaemia due to the blood loss (although it is unusual for the blood loss to be severe). However, around 20% of dogs with IMT also have similar immune-mediated destruction of their red blood cells. These cells contain haemoglobin and function to carry oxygen throughout the body. When both IMT and immune mediated haemolytic anaemia are present, the condition is termed Evan’s syndrome (Wilkins et al 1973, Williams & Maggio-Price 1984, Jackson & Kruth 1985). About 22% of dogs with immune mediated haemolytic anaemia have severe thrombocytopenia (Carr et al 2002).

One serious consequence of IMT can be total disruption of the blood clotting process. This can lead to disseminated intravascular coagulation; a syndrome in which multiple small blood clots develop throughout the circulatory system that both obstruct blood vessels and use up the normal supplies of clotting factors such that spontaneous bleeding occurs. Disseminated intravascular coagulation is a serious disease and affected animals have a poor outlook (Scott-Moncrieff et al 2001, Carr et al 2002).

Whether or not an individual dog develops clinical signs does not seem directly related to its platelet concentration but the reason for this is unclear. It may reflect that some animals have circulating platelets that are immature and not fully functional or whose function has been compromised by attack by antibodies (Mackin 2010). It has been suggested that some environmental factors may trigger clinical signs and that these may include: stresses such as surgery, kennelling, high or low environmental temperatures, vaccination, being in-season, and giving birth (Dodds 1983, Jackson & Kruth 1985). The disease is more common in females and, although it can occur at any stage of life, it usually affects dogs in middle age (Wilkins et al 1973, Williams & Maggio-Price 1984, Jackson & Kruth 1985, Lewis et al 1995, Putsche & Kohn 2008). The mean age of onset is about six years (Mackin 2010).

Return to top

2. Intensity of welfare impact

The severity of the welfare impact of IMT depends on the severity of the thrombocytopenia. Affected dogs are likely to feel unwell. Around 70% of affected dogs get better with medical treatment, which involves the administration of drugs to suppress the immune system: usually corticosteroids but sometimes chemotherapeutic agents (cancer-treating drugs). Some of these dogs require long-term treatment. Around 30% of dogs with IMT die from the condition or are euthanased as a result of it (Wilkins et al 1973, Williams & Maggio-Price 1984, Jackson & Kruth 1985, Jans et al 1990). Bleeding into confined body cavities, such as within the eyeball, the skull and joints can cause severe pain due to the increased pressure within them as a result.

The welfare consequences are more likely to be severe in those dogs that are also suffering from immune-mediated haemolytic anaemia (Jackson & Kruth 1985, Carr et al 2002, Goggs et al 2008).

Side effects of drugs used to treat IMT may also have adverse effects on welfare. Corticosteroid treatment is most commonly used and higher doses are usually necessary. The side-effects of this can include gastrointestinal ulceration leading to indigestion-type pain or ulceration and peritonitis – inflammation of the membranes of the abdomen, with other painful knock-on consequences (Ramsey 2011).

Some animals that respond poorly to medical treatments may respond to removal of the spleen. However, this is a major operation with significant welfare implications that are associated with their hospitalisation and the stress and pain of the procedure itself.

Return to top

3. Duration of welfare impact

The adverse welfare effects of IMT are likely to last for days to weeks and treatment can last for weeks to months. Some animals require life-long treatment and around 40% of affected animals are likely to have recurrent bouts of IMT (Lewis 2000b).

Return to top

4. Number of animals affected

We are not aware of data on the prevalence of IMT in long-haired dachshunds but it is believed that they, and certain family lines in particular, are predisposed to the disease (Lewis 2000b).

Return to top

5. Diagnosis

Petechial haemorrhages or ecchymoses are suggestive of low platelet concentration or abnormal platelet function. Detection of low platelet concentration is usually straightforward but determining that this is due to IMT is difficult. There is no definitive test for IMT (although attempts to detect abnormal platelets with attached antibodies have been tried they have been found to be difficult to perform and to have unreliable results and they tend to not be available in practice). Diagnosis of IMT is therefore usually based on the finding of a low platelet concentration with no other obvious cause. Response to treatment may help confirm the diagnosis (Lewis 2000b).

Return to top

6. Genetics

It is suspected that long-haired dachshunds are predisposed to IMT but, as far as we are aware, there have been no studies on the pattern of inheritance or to determine the genes involved.

Return to top

7. How do you know if an animal is a carrier or likely to become affected?

It is not known if animals can pass on the disease to offspring without having developed it themselves. There are no tests to detect animals at risk or which might be carriers. Avoiding the purchase of a puppy with close relatives (parents, grandparents and the siblings of parents and grandparents) that have been affected with IMT is advisable.

Return to top

8. Methods and prospects for elimination of the problem

As far as we are aware, there are currently no organised schemes aimed at reducing the prevalence of IMT in long-haired dachshunds. Although the genes involved have not been determined, selective breeding using animals with relatives that have histories of no, or of a lower than average, incidence of the condition is likely to be effective in reducing the number of affected dogs (Indrebo 2006, Bell 2010).

Return to top

9. Acknowledgements

UFAW is grateful to Rosie Godfrey BVetMed MRCVS and David Godfrey BVetMed FRCVS for their work in compiling this section

Return to top

10. References

Bell JS (2010) Genetic Testing and Genetic Counseling in Pet and Breeding Dogs. 35th World Small Animal Veterinary Association World Congress Proceedings. 2-5th June 2010, Geneva, Switzerland. http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=wsava2010&PID=pr56159&O=VIN accessed 14.7.2011

Carr AP, Panciera DL and Kidd L (2002) Prognostic Factors for Mortality and Thromboembolism in Canine Immune-Mediated Hemolytic Anemia: A Retrospective Study of 72 Dogs. Journal of Veterinary Internal Medicine 16: 504-9

Cockburn C and Troy GC (1986) A retrospective study of 62 cases of thrombocytopenia in the dog. Southwestern Veterinarian 37: 133-141

Dodds WJ (1983) Immune-mediated diseases of the blood. Advances in Veterinary Science and Comparative Medicine 27: 163-96

Goggs R, Boag AK and Chan DL (2008) Concurrent immune-mediated haemolytic anaemia and severe thrombocytopenia in 21 dogs. Veterinary Record 163:323-327

Grindem CB, Breitschwerdt EB, Corbett WT and Jans HE (1991) Epidemiological survey of thrombocytopenia in dogs: a report on 987 cases. Veterinary Clinical Pathology 20: 38

Indrebo A (2006) Healthy Dog Breeding -The Value of Breeding Programmes. World Small Animal Veterinary Association Proceedings http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=wsava2006&PID=pr15830&O=VIN accessed 14.10.2011

Jackson ML and Kruth SA (1985) Immune-mediate haemolytic anaemia and thrombocytopenia in the dog: a retrospective study of 55 cases diagnosed from 1969 through 1983 at the Western College of Veterinary Medicine. Canadian Veterinary Journal 26: 245-250

Jans HE, Armstrong PJ and Price GS (1990) Therapy of immune-mediated thrombocytopenia. A retrospective study of 15 dogs. Journal of Veterinary Internal Medicine 4: 4-7

Lewis DC (2000a) Disorders of platelet number. In Day M, Mackin A and Littlewood J. Eds. Manual of Canine and Feline haematology and transfusion medicine British Small Animal Veterinary Association, Cheltenham UK. pp 185

Lewis DC (2000b) Immune-mediated thrombocytopenia. In Day M, Mackin A and Littlewood J. Eds. Manual of Canine and Feline haematology and transfusion medicine. British Small Animal Veterinary Association, Cheltenham, UK pp 219

Lewis DC, Meyers KM, Callan MB, Bucheler J and Giger U (1995) Detection of platelet-bound and serum platelet-bindable antibodies in the diagnosis of canine ITP. Journal of the American Veterinary Medical Association 206: 47-52

Mackin A (2010) Immune-Mediated Thrombocytopenia: Pathophysiology and Diagnosis. Atlantic Coast Veterinary Conference http://www.vin.com/Members/Proceedings/Proceedings.plx?CID=acvc2010&PID=pr57210&O=VIN accessed 14.7.2011

Putsche JC and Kohn B (2008) Primary Immune-mediated Thrombocytopenia in 30 Dogs (1997–2003). Journal of the American Animal Hospital Association 44: 250-257

Ramsey I (2011) Prednisolone. In: BSAVA Small Animal Formulary 7th edition, British Small Animal Veterinary Association, Cheltenham UK pp 295

Scott-Moncrieff JC, Treadwell NG, McCullough SM and Brooks MB (2001) Hemostatic abnormalities in dogs with primary immune-mediated hemolytic anemia. Journal of the American Animal Hospital Association 37: 220-227

Wilkins RJ, Hurvitz AL and Dodds WJ (1973) Immunologically mediated thrombocytopenia in the dog. Journal of the American Veterinary Medical Association 163: 277-82

Williams DA and Maggio-Price (1984) Canine idiopathic thrombocytopenia: clinical observations and long-term follow-up in 54 cases. Journal of the American Veterinary Medical Association 185: 660

© UFAW 2011


Credit for main photo above:

http://depositphotos.com/19209111/stock-photo-portrait-of-standard-smooth-haired-dachshund.html ©Depositphotos.com/CaptureLight