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[[Category:To Do - Steph]]
[[Category:To Do - Steph]]
[[File:Anasmosis.jpg|thumb|200px|right|Rickettsia sp inside tick haemolymph cells (sourced from Wikimedia Commons)]]
[[File:Anasmosis.jpg|thumb|200px|right|Rickettsia sp inside tick haemolymph cells (sourced from Wikimedia Commons)]]
Also Known As – '''''[[Anaplasma marginale]]''''' – '''''Anaplasma ovis''''' - '''''Gall sickness''''' – '''''Gallsickness''''' – '''''Tick fever''''' (Australia) – '''''Tristeza''''' (Portugal)
=Introduction=
Anaplasmosis is a ruminant disease caused by the '''rickettsial''' pathogens ''[[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. central'' 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 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 and is exacerbated by stress.
=Distribution=
Anaplasmosis occurs 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.
=Transmission and Lifecycle=
Anaplasmosis is '''not directly contagious''' and most transmission occurs via [[ticks]].
Any stage of the tick’s lifecycle can become infected with Anaplasma organisms.
After development within the tick, the final infective stage is within the '''salivary glands''' and is injected into the bloodstream of the host when the parasite bloodfeeds. Male ticks are more mobile and longer lived therefore may play a bigger role.
See [[Tick Disease Transmission]] for more information on ticks as disease vectors.
Infected [[erythrocytes]] are disrupted and release bodies which can invade other erythrocytes. These bodies form vacuoles within the cytoplasmic membranes of the [[erythrocytes | red blood cells]] and then undergo binary fission to form inclusion bodies. This amplifies infection within the host and increases the likelihood of transmission when insects bloodfeed.
Other insects can be important vectors depending upon location, such as dipteran flies in the USA.
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.
===Gastrointestinal=== Anorexia and mucoid diarrhoea, Rumenal atony, Excess salivation.
===Urinary=== Red, brown or pink urine
===Other=== Swelling of the head, face and ears, General paresis/paralysis, Rough hair coat
===Neurological signs=== Shivering, fasciculations, ataxia, seizures, syncope
===Reproductive=== Abortion, infertility, agalactia
Signs are often severely exacerbated by '''exercise'''.
=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]].
=Treatment=
'''Oxytetracycline''' and '''Imidocarb''' are both highly effective and prompt treatment usually ensures survival for all but the most severely affected. 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 eliminate the carrier state.
=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.
Care when performing veterinary and husbandry procedures to prevent iatrogenic transmission with contaminated instruments.
Control of the '''[[Ticks | tick]] vector is viable but expensive.
=References=
<references/>
Animal Health & Production Compendium, Anaplasmosis datasheet, accessed online 02/06/2011 @ http://www.ahpc.org/