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[[Category:To Do - CABI]]
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Also Known As: '''''Gall sickness''''' — '''''Gallsickness''''' — '''''Tick fever''''' (Australia) — '''''Tristeza''''' (Portugal)
Caused by: '''''[[Anaplasmas|Anaplasma marginale — A. ovis — A. mesaeterum]] — Ehrlichia bovis
==Introduction==
[[File:Anaplasmosis.jpg|thumb|200px|right|''Rickettsia'' sp. inside tick haemolymph cells (sourced from Wikimedia Commons)]]
Anaplasmosis is a ruminant disease caused by the [[:Category:Rickettsiales|'''rickettsial''']] pathogens [[Anaplasmas|''Anaplasma marginale'', ''A. ovis'', ''A. mesaeterum'']] and ''Ehrlichia bovis''.
These rickettsial parasites reside exclusively within the '''[[erythrocytes| red blood cells]]''' of their hosts.
Cattle, sheep, deer, antelope and wild ruminants can all be affected.
''A. marginale'' is usually the causative agent in cattle and wild ruminants, while ''A. ovis'' is most commonly isolated in sheep and goats.
''A. centrale'' caused mild disease in cattle and is now the foundation for some vaccines.
''A. mesaeterum'' is similar to ''A. ovis'' but has a lower pathogenicity.
This disease is notifiable to the World Organisation of Animal Health ([http://www.oie.int/ OIE])
==Signalment==
The resistance of ''Bos indicus'' cattle to [[:Category:Ticks|ticks]] may reduce the rate of transmission in this breed.
No other breed predilection is evident.
'''Maternal derived immunity''' in calves is followed by '''age related immunity''', and thus animals do not appear susceptible to anaplasmosis until '''9-12 months old'''.
Exposure before this age often results in lifelong, protective immunity providing endemic stability even in the presence of disease and vectors.
No marked age vulnerability appears to exist in sheep and all ages appear to acquire disease equally although it is usually mild but is exacerbated by stress.
==Distribution==
Anaplasmosis occurs most commonly in '''tropical''' and subtropical regions, particularly South and Central America, USA, Africa, Australia and Southern Europe. This climate supports the insect and mechanical vectors required for transmission of the parasite.
Its use of other insect vectors such as the [[Ceratopogonidae | Culicoides midge]] and biting flies mean that distribution of Anaplasmosis is inceasing all the time.
==Transmission==
Anaplasmosis is '''not directly contagious''' and most transmission occurs via '''[[Ticks | ticks]]'''.
Cattle that recover become persistent '''carriers''' and although clinical signs do not recrudesce, sequential ricketssial lifecycles are ongoing and therefore reinfection of insect vectors and transmission to other vulnerable animals continues.
'''Transplacental''' transmission from infected dams can also occur.
Anaplasmosis is not considered zoonotic.
==Clinical Signs==
'''Cardiovascular'''
:Profound anaemia resulting in tachycardia and dyspnoea. Congestion of mucous membranes which may be jaundiced.
'''Gastrointestinal'''
:Anorexia and mucoid diarrhoea, rumenal atony, excess salivation.
'''Urinary'''
:Haemoglobinuria does '''not''' occur
'''Neurological signs'''
:Shivering, fasciculations, ataxia, seizures, syncope
'''Reproductive'''
:Abortion, infertility, agalactia
'''Other'''
:General paresis/paralysis, rough hair coat, weight loss
Signs are often severely exacerbated by '''exercise''' with caution needed not to overly stress animals during clinical examination which can lead to collapse and death.
==Diagnosis==
Identification of the organism within the erythrocytes on a thin '''blood smear''' with Giemsa staining is both uncomplicated and definitive.
A positive result is deemed as '''>5% red blood cells infected''' or accompanying anaemic signs. The number of infected cells doubles every 24 - 48h and may reach 90%.
The degree of parasitaemia is much lower in sheep and goats.
'''Complement fixation''' is the current international test but it lacks sensitivity.
On post mortem, carcasses are emaciated and blood is thin and watery. [[Icterus | Jaundice]] is often evident and the spleen may be engorged as a consequence of profound anaemia.
Serous effusions may be present in any body cavity. The spleen may be engorged and the kidneys congested.
Urine is dark yellow/brown due to the presence of [[Bilirubin | bilirubin]]. The absence of haemoglobinuria/haematuria is a useful sign to distinguish the condition from other differential diagnoses that present in a similar way.
==Treatment==
'''Oxytetracycline''' and '''Imidocarb''' are both highly effective and prompt treatment usually ensures survival for all but the most severely affected individuals. Note that imidocarb is not approved for use in some countries.
Supportive treatment such as '''blood transfusions''' and appetite stimulants in severe cases may be required.
A long combined course of imidocarb and oxytetracycline can also be used to try and eliminate the carrier state. However, a trial into using oxytetracycline for this purpose showed it to be ineffective for this purpose <ref>Coetzee ''et al'' (2005) '''Comparison of three oxytetracycline regimes for the treatment of persistent Anaplasma marginale infections in beef cattle. '''''Veterinary Parasitology'' 127:61-73.</ref>.
==Control==
'''[[Vaccines]]''' against anaplasmosis are available, all are derived from the blood of infected cattle. Both live and killed forms are available.
'''Detection''' and '''culling''' or '''treatment''' of '''carrier animals''' is essential.
Take care when performing veterinary and husbandry procedures to prevent iatrogenic transmission with contaminated instruments.
[[Tick Control|Control of the tick vector]] is viable but expensive.
{{Learning
|literature search = [http://www.cabdirect.org/search.html?q=title%3A+Anaplasmosis/ Anaplasmosis Publications]
|flashcards = [[Anaplasmosis Flashcards]]
}}
==References==
<references/>
{{CABI source
|datasheet = [http://www.cabi.org/ahpc/?compid=3&dsid=94682&loadmodule=datasheet&page=2144&site=160 Anaplasmosis]]
|date = June 2, 2011
}}
<br><br><br>
{{Nick Lyons
|date = October 16, 2011}}
{{OpenPages}}
[[Category:Lymphoreticular and Haematopoietic Diseases - Cattle]]
[[Category:CABI Expert Review Completed]][[Category:CABI AHPC Pages]]
[[Category:Anaemia|3]]
[[Category:Nick Lyons reviewed]]