Difference between revisions of "Canine Distemper Virus"

Revision as of 14:57, 12 August 2010

Description

Canine distemper is a contagious, febrile disease of canids and other carnivores caused by Canine Distemper Virus. Canine distemper virus is a member of the Paramyxoviridae family and the morbillivirus genus. The Paramyxoviridae have a helical nucleocapsid surrounded by an envelope which possesses spiked glycoproteins responsible for haemagglutinin, neuraminidase and haemolytic activities. The genome of the Paramyxoviridae is single-stranded, negative-sense RNA which is used as a template for the production of messenger (positive-sense) RNA and further genomic material. Paramyxoviridae are sensitive to heat, dessication and most disinfectants, and so are not resistant in the environment. The Paramyxovididae family is divided to two sub-families, the Paramyxovirinae and the Pneumovirinae. It is within the Paramyxovirinae sub-family that morbilliviruses fall, along with respiroviruses, henipaviruses, rubulaviruses and avulaviruses. As well as canine distemper virus (CDV), the morbilliviruses include rinderpest, peste de petits ruminants, measles, phocine distemper and dolphin distemper.

Aerosol infection

Infects alveolar macrophages or oropharynx
Multiplies in the bronchial and other lymph nodes, infects monocytes and dendritic cells
Viraemia
Spreads via monocytes to a variety of epithelium depending upon the strain of virus
Respiratory and alimentary tracts, skin and later (1-5 wk. post infection) to the brain
Clinical signs:
- Mucopurulent oculonasal discharge
- Keratitis
- Interstitial pneumonia
- Severe clinical pneumonia follows secondary infection with Bordetella bronchiseptica
- Smelly sometimes bloody diarrhoea
- Eruptions on the skin including hyperkeratosis of the nose and pads (hardpad)
- Demyelination (especially in cerebellum) -> incoordination or muscle tremors -> paralysis and coma or convulsions -> death
- Encephalitis
- Secondary pyogenic infections associated with immunosuppression and damage to epithelia
- Recovered animals may have persistent or spasmodic chorea
- The severity of the disease may vary; if enough neutralising antibody develops in the early stages, the virus maybe kept restricted largely to the lymph nodes
Variable mortality depending on virulence
May occur subclinically
Involvement of central nervous system generally results in death

Can contribute to Infectious Canine Tracheitis
May be involved in chronic interstitial pancreatitis
May cause growth retardation lattice
May also trigger latent Toxoplasmosis due to suppressing effect on lymphoid tissue

Signalment

Dogs, ferrets, seals, lions, mink
Has been a major pathogen of dogs prior to vaccination

Diagnosis

May present as series of infections
Immunocytochemistry of inclusion bodies
- Intracytoplasmic inclusions may be found in most affected tissues
- Inclusions persist longest in the brain (may be intranuclear) and the alveolar macrophages
- Sections of fixed bronchial tissue, lung, macrophages, bladder may be used or nasal or conjunctival epithelium from live animals
Giant cells may be seen in the alveol

Clinical Signs

Laboratory Tests

Diagnostic Imaging

Pathology

Rhinitis
Although many organs can be affected by CDV, a relatively constant feature is the respiratory signs which occur in varying severity
A syndrome of catharral oculonasal discharge, pharyngitis and bronchitis is relatively common in the initial stages
Since one of the primary sites of action of this virus is lymphoid tissue, the resultant immunosuppression -> predisposition to secondary bacterial infection
May cause interstitial pneumonia where inclusions are found within alveolar macrophages
Gross pathology:
- Oedematous lungs, diffuse interstitial pneumonia
Micro pathology:
- Necrosis of pneumocytes, necrotising bronchiolitis, alveolar oedema, thickening of alveolar walls and type II pneumocyte hyperplasia

Treatment

Live attenuated virus vaccines given at 10 and 12 weeks of age
- Some now given at 7 and 10 weeks to allow socialisation
Homeopathic vaccines do not work
Live attenuated vaccines may kill some wildlife therefore Iscom vaccine is used in seal sanctuaries

Prognosis

Links

References

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-{{OpenPagesTop}}
+{{unfinished}}
-Also known as: '''''Canine Distemper — CDV'''''
 ==Description==
-Canine distemper is a contagious, febrile disease of canids and other carnivores caused by Canine Distemper Virus. Canine distemper virus is a member of the [[:Category:Paramyxoviridae|Paramyxoviridae]] family and the [[:Category:Morbilliviruses|morbillivirus]] genus.
+Canine distemper is a contagious, febrile disease of canids and other carnivores caused by Canine Distemper Virus. Canine distemper virus is a member of the Paramyxoviridae family and the morbillivirus genus. The Paramyxoviridae have a helical nucleocapsid surrounded by an envelope which possesses spiked glycoproteins responsible for haemagglutinin, neuraminidase and haemolytic activities. The genome of the Paramyxoviridae is single-stranded, negative-sense RNA which is used as a template for the production of messenger (positive-sense) RNA and further genomic material. Paramyxoviridae are sensitive to heat, dessication and most disinfectants, and so are not resistant in the environment. The Paramyxovididae family is divided to two sub-families, the Paramyxovirinae and the Pneumovirinae. It is within the Paramyxovirinae sub-family that morbilliviruses fall, along with respiroviruses, henipaviruses, rubulaviruses and avulaviruses. As well as canine distemper virus (CDV), the morbilliviruses include rinderpest, peste de petits ruminants, measles, phocine distemper and dolphin distemper.
-Canine distemper virus is shed in all excretions and secretions, and is spread by direct and indirect contact via ingestion or inhalation of aerosolised droplets. Initial infection of the nasal cavity, pharynx and lungs is followed by a macrophage-associated viraemia to local lymph nodes where the virus replicates. Within one week, all lymphoid tissue is infected, causing [[lymphopenia]]. A second viraemic stage then distributes the virus to the surface epithelium of the respiratory, gastrointestinal and urogenital tracts, endocrine tissue and the grey and white matter of the CNS.  A biphasic pyrexia is typical of distemper infection: the first fever occurs 3-6 days post-infection and is associated with lymphopenia, and the second peak coincides with widespread viraemia. Further signs depend on both the virus strain and the immune response mounted. In the event of a strong humoral and cellular response, disease may remain subclinical, and if a weak immune response is mounted infection is generally subacute. If the immune response fails, acute disease and potentially death ensues. When clinical disease manifests, this is initially characterised by lethargy, dehydration, anorexia, and weight loss followed by more specific signs depending on the principally affected organ.
-==Signalment==
-Although canine distemper virus is found worldwide, outbreaks in dogs are sporadic due to effective vaccination protocols. However, many other wildlife species may be affected by the virus, and some examples are listed in the table below. Large cats in Tanzania and in some US zoos have also been found to have CDV.
-Although young animals are more susceptible than adults and, clearly, unvaccinated animals are at a higher risk of infection, there are no breeed or sex predilections for canine distemper.
-{|cellpadding="10" cellspacing="0" border="1" width="{{{width|33%}}}" align="center"
+Aerosol infection
-| <center><u>'''Canidae'''</u> </center>
+*Infects alveolar [[Macrophages|macrophages]] or [[Oropharynx - Pathology|oropharynx]]
-| <center><u>'''Procyonidae'''</u> </center>
+*Multiplies in the bronchial and other lymph nodes, infects [[Monocytes|monocytes]] and dendritic cells
-| <center><u>'''Mustelidae'''</u> </center>
+*Viraemia
-|-
+*Spreads via [[Monocytes|monocytes]] to a variety of epithelium depending upon the strain of virus
-| <center> Coyote <BR> Dingo <BR> Fox <BR> Jackal <BR> Wolf </center>
+*Respiratory and alimentary tracts, skin and later (1-5 wk. post infection) to the brain
-| <center> Lesser panda <BR> Racoon <BR> Coati <BR> Bassariscus </center>
+*'''Clinical signs''':
-| <center> Ferret <BR> Marten <BR> Mink <BR> Otter <BR> Sable <BR> Wolverine <BR> Badger <BR> Skunk </center>
+**Mucopurulent oculonasal discharge
-|}
+**Keratitis
+**[[Lungs Inflammatory - Pathology#Interstitial pneumonia|Interstitial pneumonia]]
+**Severe clinical pneumonia follows secondary infection with [[Bordetella bronchiseptica|''Bordetella bronchiseptica'']]
+**Smelly sometimes bloody diarrhoea
+**Eruptions on the skin including hyperkeratosis of the nose and pads (hardpad)
+**[[PNS Repsonses to Injury - Pathology#Segmental Demyelination|Demyelination]] (especially in cerebellum) -> incoordination or muscle tremors -> paralysis and coma or convulsions -> death
+**Encephalitis
+**Secondary pyogenic infections associated with immunosuppression and damage to epithelia
+**Recovered animals may have persistent or spasmodic chorea
+**The severity of the disease may vary; if enough neutralising antibody develops in the early stages, the virus maybe kept restricted largely to the lymph nodes
+*Variable mortality depending on virulence
+*May occur '''subclinically'''
+*Involvement of central nervous system generally results in death
+*Can contribute to [[Canine Infectious Tracheobronchitis|Infectious Canine Tracheitis]]
+*May be involved in [[Pancreatitis, Chronic Interstitial|chronic interstitial pancreatitis]]
+*May cause [[Bones Developmental - Pathology#Retention of elongated primary trabeculae|growth retardation lattice]]
+*May also trigger latent [[Toxoplasma|Toxoplasmosis]] due to suppressing effect on lymphoid tissue
+==Signalment==
+*Dogs, ferrets, seals, lions, mink
+*Has been a major pathogen of dogs prior to vaccination
 ==Diagnosis==
+*May present as series of infections
-Although a presumptive diagnosis is frequently made on the basis of clinical signs in a young unvaccinated dog, there are several methods of investigating and confirming canine distemper.
+*'''Immunocytochemistry''' of inclusion bodies
+**Intracytoplasmic inclusions may be found in most affected tissues
+**Inclusions persist longest in the brain (may be intranuclear) and the alveolar macrophages
+**Sections of fixed bronchial tissue, lung, macrophages, bladder may be used or nasal or conjunctival epithelium from live animals
+*Giant cells may be seen in the alveol
 ===Clinical Signs===
-Canine distemper is characterised by a biphasic fever, with the first peak 3-6 days post-infection and the second peak several days later and intermittently thereafter. The second peak of pyrexia is usually associated with the onset of other clinical signs. These initially include congested conjunctiva and nasal mucosa leading to serous ocular and nasal discharges that become mucopurulent. The animal is depressed and anorexic, and vomiting, diarrhoea and pneumonia commonly follow. These gastrointestinal and respiratory signs are often complicated by secondary bacterial infections, as CDV is highly immunosuppressive. Lesions may occur on the retina and optic neuritis can develop. Some strains of CDV cause hyperkeratosis of the footpads and the nose, and retinal lesions and optic neuritis can occur. In neonates, hypoplasia of the unerupted tooth enamel is common following infection, causing "distemper rings". Pustular dermatitis may also be seen on the abdomen of infected puppies. In pregnant animals, transplacental infection can result in abortions, stillbirths, or the birth of persistent excretors of virus, depending on the stage of gestation.
-Many infected dogs develop CNS signs after the initial systemic disease, but this is dependent on the strain of the virus. Either the white matter or the grey matter may be affected. Grey matter disease affects the cerebral cortex, brainstem and spinal cord, and may give a non-suppurative meningitis, seizures, stupor, hysteria or ataxia. Dogs with grey matter disease may die within 2-3 weeks, recover, or progress to white matter disease. In this, multifocal lesions mean that the signs are variable: cerebellovestibular signs are common, as well as paresis, ataxia and myoclonus. Once white matter disease has developed, some dogs die with a non-inflammatory, demyelinating disease 4-5 weeks after initial systemic infection. Other animals may recover with minimal injury to the CNS but may suffer neuromuscular tics or "chewing gum" seizures for life.
-Canine distemper is often fatal, but an increased production of virus-neutralising antibodies can promote the recovery of the animal. However, CDV can persist in the uvea, CNS, lymphoid organs and footpads despite elimination from most organs and the blood. This can result in "old dog encephalitis" in dogs that recovered from acute canine distemper years previously. In this, several neurological episodes occur over weeks to months, and usually culminate in the death of the dog.
 ===Laboratory Tests===
-With the exception of lymphopenia during early infection, routine haematology and biochemistry do not show any typical changes. Serology is also of limited value for several reasons. Firstly, a patient may die before an antibody response is mounted; secondly, a positive antibody titre does not discriminate between infected and vaccinated animals; and thirdly, IgM may remain high for up to three weeks following vaccination and for three months after infection. Detection of canine distemper virus antibody in the cerebrospinal fluid is, however, indicative of distemper encephalitis.
-There are a number of tests available to confirm the diagnosis of canine distemper. Immunohistochemistry can be used to detect viral antigen in samples of skin, nasal mucosa or footpad epithelium, and viral antigen or inclusions may be demonstrated in buffy coat cells, urine sediment and conjunctival or vaginal imprints. However, negative results do not rule out a diagnosis of distemper. RT-PCR can also be performed on buffy coat, urine sediment, conjuncival swabs or cerebrospinal fluid. A retrospective diagnosis can be made post-mortem on the basis of histopathology, immunofluorescence or immunohistochemistry, virus isolation or RT-PCR. The preferred tissues for these techniques are lung, stomach, urinary bladder, lymph nodes and brain.
 ===Diagnostic Imaging===
-Thoracic radiographs may be taken to determine the extent of pneumonia for use in planning treatment and determining prognosis. CT or MRI may disclose lesions in the CNS.
 ===Pathology===
+*[[Nasal Cavity Inflammatory - Pathology#Infectious causes of rhinitis|Rhinitis]]
-On post-mortem examination, the thymus is often found to be greatly reduced in size and gelatinous in young dogs. There is patchy consolidation of the lungs due to interstitial pneumonia, and signs of catarrhal enteritis may be present. Mucopurlent discharges are commonly seen from the eyes and nose and bronchopneumonia is sometimes present. Skin pustules and hyperkeratosis of the footpads and nose are seen occasionally.
+*Although many organs can be affected by CDV, a relatively constant feature is the respiratory signs which occur in varying severity
+*A syndrome of catharral oculonasal discharge, [[Nasopharynx Inflammatory - Pathology#Infectious causes of pharyngitis|pharyngitis]] and [[Bronchi and Bronchioles Inflammatory - Pathology#Infectious causes of bronchitis or bronchiolitis|bronchitis]] is relatively common in the initial stages
-Microscopically, eosinophilic intra-cytoplasmic inclusion bodies are often found in the bronchial, gastric and urinary epithelium. They may also be seen in leukocytes and lymphoid tissue. In the CNS, inclusion bodies are frequently intra-nuclear in both neurons and glial cells. Demyelination may also be seen. When inclusion bodies are not evident, immunofluorescence or immunohistochemistry may be used to detect canine distemper virus antigen. Virus isolation or RT-PCR can also be carried out post-mortem using lung, stomach, urinary bladder, lymph nodes or brain sample.
+*Since one of the primary sites of action of this virus is lymphoid tissue, the resultant immunosuppression -> predisposition to secondary bacterial infection
+*May cause [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]] where [[Degenerations and Infiltrations - Pathology#Cellular Inclusions|inclusions]] are found within alveolar macrophages
+*Gross pathology:
+**Oedematous lungs, diffuse interstitial pneumonia
+*Micro pathology:
+**Necrosis of pneumocytes, necrotising bronchiolitis, alveolar oedema, thickening of alveolar walls and type II pneumocyte hyperplasia
 ==Treatment==
-Dogs suffering distemper should be treated in isolation with barrier nursing to prevent spread to other dogs. Treatment is supportive, including intravenous fluid therapy to correct the deficit cause by vomiting and diarrhoea and antiobitics to reduce secondary infections. Anticonvulsants such as phenobarbital and potassium bromide may be necessary to control seizures. Although corticosteroids may alleviate clinical signs in the short term, they should be used with caution as they augment the immunosuppression caused by CDV and may enhance viral dissemination. Animals should be rested and fed a diet appropriate to the severity of their gastrointestinal signs.
+*Live attenuated virus vaccines given at 10 and 12 weeks of age
+**Some now given at 7 and 10 weeks to allow socialisation
-[[Vaccines|Vaccination]] is key to controlling canine distemper. Modified live vaccines are available, and are considered a "core" vaccination for dogs. Puppies can receive their first vaccination between 6 and 8 weeks of age, and must be given at least two doses of CDV vaccine with the final does being administered after 12 weeks of age. This multiple dose regimen is necessary because the maternal antibody in puppies greatly hampers the efficacy of vaccination by neutralising viral antigen. Modified live vaccines should not be used in pregnant bitches, and may cause fatal disease in certain wildlife species. Therefore a killed vaccine is available for use in, for example, red pandas.
+*Homeopathic vaccines do not work
+*Live attenuated vaccines may kill some wildlife therefore '''Iscom vaccine''' is used in seal sanctuaries
 ==Prognosis==
-The prognosis for CDV infection is dependent on the strain of the virus and the host immune response, as infection may be subclinical, subacute or acute. Overall, the mortality rate is around 50%, with death occuring 2 weeks to 3 months post-infection. Animals that appear to recover from early systemic signs may go on to develop CNS involvement which can vary in severity. Euthanasia may be considered with the onset of neurological signs, and is indicated when seizuring is uncontrollable. Dogs that fully recover do not shed the virus.
-{{Learning
-|literature search = [http://www.cabdirect.org/search.html?q=%28%28title%3A%28distemper%29+AND+%28diagnosis%29%29%29+AND+%28%28title%3A%28distemper%29+AND+%28treatment%29%29%29 Distemper diagnosis and treatment]
-}}
 ==Links==
-*[http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/56700.htm The Merck Veterinary Manual - Canine Distemper]
-*[http://www.avma.org/animal_health/brochures/canine_distemper/distemper_brochure.asp AVMA Brochure - Canine Distemper]
 ==References==
-#Tilley, L.P. and Smith, F.W.K.(2004)'''The 5-minute Veterinary Consult (Fourth Edition)''' ''Blackwell Publishing''.
-#Merck & Co (2008) '''The Merck Veterinary Manual (Eighth Edition)''' ''Merial''.
-#Carter, GR and Wise, DJ (2005) '''A Concise Review of Veterinary Virology''', ''International Veterinary Information Service''.
-#Vandevelde, M and Zurbriggen, A (1995) The neurobiology of canine distemper virus infection. ''Veterinary Microbiology'' '''44''', 271-280.
-#Chappuis, G (1995) Control of canine distemper. ''Veterinary Microbiology'', '''44''', 351-358.
-#Beineke, A, Puff, C, Seehusen, F, Baumgartner, W (2009) Pathogenesis and immunopathology of systemic and nervous canine distemper. ''Veterinary Immunology and Immunopathology'', '''127''', 1-18.
-{{review}}
-{{OpenPages}}
-[[Category:Morbilliviruses]][[Category:Respiratory Diseases - Dog]][[Category:Dog Viruses]]
+[[Category:Morbilliviruses]][[Category:Dog]]
-[[Category:Expert Review]]
+[[Category:To_Do_- Lizzie]]
 [[Category:Respiratory Viral Infections]]