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→Clinical Signs
===Heartwater===
{{OpenPagesTop}}
{{Taxobox
|name = ''Cowdria ruminantium''
|kingdom = Bacteria
|sub-kingdom =
|phylum = Proteobacteria
|super-class =
|class = Alphaproteobacteria
|sub-class =
|super-order =
|order = [[Rickettsiales]]
|sub-order =
|super-family =
|family = Ehrlichiaceae
|sub-family =
|genus = Cowdria
|species = ''C. ruminantium''
}}
Also Known As: '''''Heartwater — Ehrlichiosis — Nintas (South Africa)'''''
Caused by: '''''Cowdria ruminantium''''' Also known as: '''''Rickettsia ruminantium'''''
==Introduction==
''C. ruminantium'' is a '''[[Bacteria | bacterial]] gram negative coccal''' pathogen causing the '''[[Tick Disease Transmission |tickborne]] disease “Heartwater”''' in ruminants in '''Subsaharan Africa'''. Animals often acquire the disease when moved on to heartwater infected grazing.
It is an '''intracellular bacteria''', residing in endothelial cells and affecting the cardiovascular, respiratory and neurological systems.
Cowdriosis has a huge economic impact in Africa, both in direct losses and as an obstruction to the improvement of breeding stock due to the susceptibility of introduced high producing breeds.<ref> Uilenberg, G. (1982) '''Disease problems associated with the introduction of European cattle in the tropics. '''''Proc 12th World Cong Diseases Cattle, The Netherlands, ''1025-1032</ref>
Cowdriosis is '''notifiable''' to the World Organisation for Animal Health [http://www.oie.int/ (OIE)].
[[Category:Rickettsiales]][[Category:Cattle]][[Category:Sheep]][[Category:Goat]]
==Distribution==
Cowdriosis occurs across the African continent, particularly in '''South Africa'''.
Cowdriosis is transmitted by '''bont [[Ticks |ticks]]''', mainly of the [[Amblyomma spp.|''Amblyomma'' genus]] (''A. variegatum'' and ''A. hebraeum'') but also [[Rhipicephalus spp.|''Rhipicephalus'']], [[Hyalomma spp.|''Hyalomma'']], and ''Glossina'' species and the ''[[Sarcoptes|Sarcoptes scabei]]'' mite. Both adults and nymphs of tick species can transmit disease.
Heartwater is therefore also a risk for countries where the ''Amblyomma'' tick is present, such as mainland America, Asia and the Caribbean, although disease may cutrently not be.
''C. ruminantium'' develops and replicates within both its mammalian and invertebrate hosts.
Although speculated to be potentially zoonotic, there is no evidence of cowdriosis affecting humans.
==Signalment==
Cowdriosis affects a wide range of domestic and wild ruminants, although not all develop clinical disease. Clinical disease is most common in '''young animals.'''
''Bos indicus'' (zebu) cattle appear more '''resistant''' than European breeds<ref> Uilenberg, G. (1983) '''Heartwater (''Cowdria ruminantium ''infection): current status.''' ''Adv Vet Sci Comp Med'', 27:427-480</ref>
==Clinical Signs==
Clinical signs are attributable to '''increased vascular permeability''' due to '''vascular endothelial cell invasion''' and consequent oedema and hypovolaemia:
'''Tachycardia, petechiae''' on mucous membranes\conjunctiva, weak pulses, muffled heart sounds.
Dull areas on percussion of the thorax, '''cough''', purulent nasal discharge, abnormal respiratory noises, '''tachypnoea'''.
'''Head tilt, tremors''', coma, circling, abnormal reflexes, '''hyperaesthesia, aggression''', head pressing, depression, nystagmus, mydriasis and blindness.
Animals display a '''high fever''' which may progress to hypothermia. They gradually stop feeding and their behaviour changes.
Cowdriosis can also cause reproductive and gastrointestinal disease.
Various factors such as species, breed, age, natural resistance, vector efficiency and immune status dictate whether clinical disease develops and its severity.
==Diagnosis==
On '''post-mortem examination''', a '''light yellow [[Transudate | transudate]]''' that '''coagulates on exposure to air''' is often found within the '''thorax, [[Pericardial - Pathology |pericardium]] and abdomen.''' Volume may vary but may be several litres in cattle.
Most fatal cases will display the '''hydropericardium''' that gives the disease its common name, although this is seen more commonly in sheep and goats than cattle. <ref> Henning, M. W. (1956) '''Heartwater'''. In: Anim Dis S Africa, ed 3. South Africa: ''Central News Agency Ltd'', 1155-1178</ref>
'''Pulmonary oedema''' and mucosal congestion are regularly seen along with '''frothy fluid''' in the airways and cut surfaces of the [[Lungs - Anatomy & Physiology |lungs]].
The [[Spleen |spleen]] may be enlarged and pulpy in consistency.
Although neurological signs are often attributed to '''cerebral oedema''', this is not always obvious macroscopically although in some cases the brain and '''gyri''' may be strikingly swollen and/or petechiated.
The organism may be visible in '''smears''' of peripheral '''blood''' or the '''buffy coat'''.
In all suspect cases, presence of ''C. ruminantium'' must be demonstrated in preparations of the '''hippocampus''' under Giemsa staining or '''histopathology''' of brain or kidney.
==Treatment==
During the '''early febrile''' stages, '''sulphonamides and tetracyclines''' appear effective.
In advanced disease, prognosis is poor due to the intensive support therapy required and degree of cell death.
==Control==
'''Tetracyclines''' can be used '''prophylactically''' when animals are introduced into an area endemic with cowdriosis.
There is also a '''blood vaccine''' available for protection from heartwater in calves, lambs and kids in South Africa. As it contains '''live''' ''C. ruminantium'' organisms, treatment may be required in some animals post vaccination.
'''Control''' of exposure to '''bont ticks''', whether total or strategic allowing a level of immunity to develop, is also vital but often difficult. It can be achieved through dipping with [[Ectoparasiticides | ectoparasiticides]].
{{Learning
|literature search = [http://www.cabdirect.org/search.html?q=title%3A+Cowdriosis Cowdriosis Publications]
|flashcards = [[Cowdriosis Flashcards]]
}}
==References==
<references/>
{{CABI source
|datasheet = [http://www.cabi.org/ahpc/?compid=3&dsid=87241&loadmodule=datasheet&page=2144&site=160 cowdriosis] and [http://www.cabi.org/ahpc/Default.aspx?site=160&page=2144&LoadModule=datasheet&CompID=3&dsID=87240 ''Cowdria ruminantium'']
|date =06 June 2011
}}
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