Changes

==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 spp'' are 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.  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).

Lyme disease descibes the clinical syndrome caused by infection with ''[[Borrelia burgdorferi]]'' sensu lato in humans, dogs, horses, cattle and sheep.  The disease is named after the town of Lyme[http://townlyme.org/ Lyme] in Connecticut, USA where clinical cases were first described in humans in 1975.  Since its identification, analysis of historical samples of ticks has shown 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><ref>Hubbard MJ, Baker AS, Cann KJ. '''Distribution of Borrelia burgdorferi s.l. spirochaete DNA in British ticks (Argasidae and Ixodidae) since the 19th century, assessed by PCR.''' ''Med Vet Entomol. 1998 Jan;12(1):89-97.''</ref>.  Currently, the bacterium is known to be present in Europe, Asia and North America (see image) and the prevalence of antibodies to ''B. burgdorferi'' sensu lato in French dogs was 1.09% when this was investigated in 2009<ref>Pantchev N, Schaper R, Limousin S, Norden N, Weise M, Lorentzen L. '''Occurrence of Dirofilaria immitis and tick-borne infections caused by Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato and Ehrlichia canis in domestic dogs in France: results of a countrywide serologic survey.''' ''Parasitol Res. 2009 Aug;105 Suppl 1:S101-14.''</ref>.

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.

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 and then transmits it to large mammals as a nymph or 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===

==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]].

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]].  For unknown reasons, a sample of Bernese Mountain dogs in Switzerland was found to have a much higher seroprevalence for ''B. burgdorferi'' sensu lato than a control population but it is not known if this is true in other regions<ref>Gerber B, Eichenberger S, Wittenbrink MM, Reusch CE. '''Increased prevalence of Borrelia burgdorferi infections in Bernese Mountain Dogs: a possible breed predisposition.''' ''BMC Vet Res. 2007 Jul 12;3:15.''</ref>.

==Diagnosis==

==Diagnosis==

**Infection of the joints may result in non-erosive '''arthritis''', causing intermittent bouts of shifting lameness.

**Infection of the joints may result in non-erosive '''arthritis''', causing intermittent bouts of shifting lameness.

**Disease in the heart may cause '''myocarditis''' with atrio-ventricular block and dysrhythmias

**Disease in the heart may cause '''myocarditis''' with atrio-ventricular block and dysrhythmias

**Infection of the kidneys may result in '''glomerulonephritis''' and [[Kidney Renal Failure - Pathology|renal failure]].  This may occur chronically but cases of acute renal failure have been described.

**'''Lyme Nephritis''' is a form of '''glomerulonephritis''' that may result in acute [[Kidney Renal Failure - Pathology|renal failure]].  This form of renal failure has been described in dogs that were seropositive for ''B. burgdorferi'' sensu stricto in the USA but extensive molecular searches failed to reveal the presence of actual bacteria in the kidneys of affected dogs<ref>Hutton TA, Goldstein RE, Njaa BL, Atwater DZ, Chang YF, Simpson KW. '''Search for Borrelia burgdorferi in kidneys of dogs with suspected "Lyme nephritis".''' ''J Vet Intern Med. 2008 Jul-Aug;22(4):860-5.''</ref>.  This form of disease has never been replicated in experimental infections.  Associations have been suggested between proteinuria and ''Borrelia'' seroprevalnce, particularly in the Bernese Mountain dog breed.

**Presence of organisms in the brain or spinal cord may cause '''neurological signs''' due to meningitis or encephalitis.

**Presence of organisms in the brain or spinal cord may cause '''neurological signs''' due to meningitis or encephalitis.

*Horses may suffer similar clinical signs of shifting '''lameness''', '''uveitis''', '''nephritis''', '''hepatitis''' and '''encephalitis'''.

*Horses may suffer similar clinical signs of shifting '''lameness''', '''uveitis''', '''nephritis''', '''hepatitis''' and '''encephalitis'''.

===Laboratory Tests===

===Laboratory Tests===

===Other Tests===

*Laboratory confirmation difficult due to low numbers of organisms and fastidious growth requirements

====Serology====

*History of exposure to ticks in an endemic region and clinical signs

Care should be taken not to overdiagnose infection based on seroprevalence as the majority of infected animals will never develop clinical signs.  Paired serology samples are not useful as antibody persists at high levels for a long period after infection. 

*Rising antibody titre to ''Borrelia burgdorferi'' detected by ELISA

 

False negative test results are unlikely and, in experimental infections, antibody titres rise shortly before clinical signs are observed. 

*Culture in Barbour-Stoenner-Kelly medium for 6 weeks under microaerophilic conditions  

 

The method of measurement of antibody titres is important as traditional methods (ELISA and immunofluorescence) may detect antibodies induced by other bacteria.  The modern C6 ELISA test has the highest specificity and sensitivity of the tests currently available as it detects antibodies to one invariant region of a protein molecule that is conserved among strains of the ''B. burgdorferi'' sensu lato complex.  The C6 ELISA also correlates well with infectious load of bacteria, falling rapidly after antibiotic therapy is instituted.

 

 

PCR has a high specificity for the detection of ''Borrelia'' organisms but it is best performed on skin samples taken from near to the site of tick attachment or on synovial fluid or cerebro-spinal fluid from animals suspected of having Lyme arthritis or meningitis.  Although the sensitivity of a PCR test is good, infection may still be present in another part of the body than that sampled.  Blood is not usually used for detection as the bacteria do not disseminate by the haematogenous route. 

 

 

====Culture====

Bacteria may be cultured in Barbour-Stoenner-Kelly medium for 6 weeks under microaerophilic conditions.  The best samples for culture are skin samples from near to the site of tick attachment (as the bacteria remain within the local connective tissues) but the test is not sensitive as the bacteria will be present in low numbers.

==Treatment==

==Treatment==

***Amoxycillin and oxytetracycline in the acute phase; prolonged treatment in the chronic phase

Both [[Penicillins|amoxycillin]] and [[Tetracyclines|oxytetracycline]] may be used for treatment in the acute phase but prolonged treatment may be needed and the organisms may never be eradicated.

***Tick control and removal

 

***Vaccines including whole cell bacterins and recombinant subunit vaccines available for dogs

Tick control and removal are vital in the prevention of new infections.  In areas with high numbers of ticks, owners should check their animals every day in areas of likely attachment (such as at the front of the body) and remove any ticks with the whole head intact.  Repellents such as the permethrins can be used when animals travel abroad.

 

Vaccines including whole cell bacterins and recombinant subunit vaccines are available for dogs in the USA.

 

==Prognosis==

==Prognosis==

==References==

==References==