829
edits
Changes
Jump to navigation
Jump to search
no edit summary
==Description==
==Description==
[[File:Borreliose.png|thumb|Map of the areas where ''Borrelia burgdorferi'' is endemic<br><small>Copyright Percherie 2006 Wikimedia Commons]]</small>
[[File:Borreliose.png|thumb|Map of the areas where ''Borrelia burgdorferi'' is endemic<br><small>Copyright Percherie 2006 Wikimedia Commons]]</small>
Lyme disease descibes the clinical syndrome caused by infection with ''[[Borrelia burgdorferi]]'' in humans, dogs, horses, cattle and sheep. The disease is named after the town of Lyme[http://townlyme.org/] in Connecticut, USA where clinical cases were first described in humans in 1975.
Lyme disease descibes the clinical syndrome caused by infection with ''[[Borrelia burgdorferi]]'' in humans, dogs, horses, cattle and sheep. The disease is named after the town of Lyme[http://townlyme.org/] in Connecticut, USA where clinical cases were first described in humans in 1975. Since its identification, it has become clear that ''B. burgdorferi'' has been present in Europe and North America since at least the start of the twentieth Century<ref>Marshall WF 3rd, Telford SR 3rd, Rys PN, Rutledge BJ, Mathiesen D, Malawista SE, Spielman A, Persing DH. '''Detection of Borrelia burgdorferi DNA in museum specimens of Peromyscus leucopus.''' ''J Infect Dis. 1994 Oct;170(4):1027-32.''</ref>. Currently, the bacterium is known to be present in Europe, Asia and North America (see image).
The bacterium is transmitted by ticks of which the most common is ''[[Ixodes spp.|Ixodes ricinus]]'' in the UK. ''I. ricinus'' is a three host tick that acquires ''B. burgdorferi'' bacteria when it obtains a blood meal from small rodents as a larva or nymph and then transmits it to large mammals as an adult. Lyme disease therefore occurs when domestic animals and humans enter areas of tick habitat.
The bacterium is transmitted by ticks of which the most common is ''[[Ixodes spp.|Ixodes ricinus]]'' in the UK. ''I. ricinus'' is a three host tick that acquires ''B. burgdorferi'' bacteria when it obtains a blood meal from small rodents as a larva or nymph and then transmits it to large mammals as an adult. Lyme disease therefore occurs when domestic animals and humans enter areas of tick habitat and ticks must be attached for at least 48 hours for the organisms to multiply and transfer to the mammalian host.
===Pathophysiology===
===Pathophysiology===
The virulence of the borreliae is associated with a change in expression of an outer membrane protein (OMP) after introduction into the mammalian host. The bacteria multiply in the blood stream of susceptible hosts and disseminate throughout the body, loaclising particularly in the joints, brain, nerves, eyes and heart. The immune response to the bacterial OMPs cross-reacts with epitopes present of host proteins and the lesions that are observed in Lyme disease may in part be caused by this immune response.
The virulence of the borreliae is associated with changes in expression of outer membrane proteins (OMP) after introduction into the mammalian host. In the majority of hosts, the bacteria remain at the site of introduction but do not cause clinical disease. Antibodies are produced in response to the bacteria but, despite this, they are not eliminated and they may persist for the life of the host. In a small proportion of infected animals, the bacteria multiply and migrate through the connective tissues and disseminate via the blood stream. The migrant bacteria localise particularly in the skin, joints, brain, nerves, eyes and heart and clinical syndromes may involve any of these organs. The immune response to the bacterial OMPs cross-reacts with epitopes present of host proteins and the lesions that are observed in Lyme disease may in part be caused by this immune response.
It is not currently known why only a small proportion of infected animals develop clinical disease.
{{unfinished}}
==Signalment==
==Signalment==
Affected animals often have a history of exposure to ticks but this may occur months before clinical disease is detected. Ticks are most abundant in particular types of habitat, as discussed [[Tick Life Cycle|here]].
==Diagnosis==
==Diagnosis==
Incubation Period.
===Clinical Signs===
===Clinical Signs===
The exact clinical signs shown depend on the species of ''Borrelia'' with which the animal is infected and on the area of the World in which infection occurs. Clinical signs are often vague, intermittent and variable between individual, reasons why the disease was not identified until late in the twentieth Century. The exact clinical manifestation also depends on the site of localisation of the organisms. In the UK, infection with ''Borrelia burgdorferi sensu lato'' may show the following signs:
*Dogs
***Disease in dogs may cause fever, lethargy, arthritis, cardiac, renal or neurological disturbance
**Fever and lethargy
**Infection of the joints may result in '''arthritis'''
**Disease in the heart may cause '''myocarditis''' with atrio-ventricular block and dysrhythmias
**Infection of the kidneys may result in '''interstitial nephritis'''
**Presence of organisms in the brain or spinal cord may cause '''neurological signs'''
*Horses may suffer similar clinical signs but also shifting '''lameness''', '''uveitis''', '''nephritis''', '''hepatitis''' and '''encephalitis'''
*Cattle and sheep may suffer from '''shifting lameness'''
===Laboratory Tests===
===Laboratory Tests===
===Other Tests===
===Other Tests===