Serologic confirmation of Ehrlichia equi and Borrelia burgdorferi infections in horses from the northeastern United States.
OBJECTIVE
To determine whether horses living in tick-infested areas of northeastern United States with clinical signs of borreliosis or granulocytic ehrlichiosis had detectable serum antibodies to both Borrelia burgdorferi and Ehrlichia equi.


METHODS
Prospective study.


METHODS
Serum samples from 51 clinically normal horses, 14 horses with clinical signs of borreliosis, and 17 horses with clinical signs of granulocytic ehrlichiosis.


METHODS
Serum B burgdorferi or E equi antibodies were measured by use of an ELISA, immunoblot analysis, or indirect fluorescent antibody (IFA) staining.


RESULTS
Of the 82 serum samples tested, 37 (45.1%) and 13 (15.9%) had detectable antibodies to B burgdorferi or E equi, respectively. Test results indicated that 12 horses had been exposed to both agents, 11 of these horses had granulocytic ehrlichiosis. The ELISA regularly detected antibodies to the following recombinant protein (p) antigens of B burgdorferi: p29, p37, p39, and p41-G. The use of immunoblot analysis confirmed ELISA results by indicating antibody reactivities to antigens of whole-cell B burgdorferi having molecular masses of predominantly 31, 34, 37, 39, 41, 58, and 93 kd.


CONCLUSIONS
Horses living in areas where ticks (Ixodes scapularis) abound are sometimes exposed to multiple pathogens. Analyses for specific recombinant borrelial antibodies using an ELISA can help separate horses with borreliosis from those with granulocytic ehrlichiosis, even when antibodies to both etiologic agents are detected in serum samples. Analysis using immunoblots is sensitive, and along with ELISA or IFA procedures, is suitable for confirming a clinical diagnosis of each disease.
Magnarelli
L A
LA
Department of Entomology, Connecticut Agricultural Experiment Station, New Haven 06504, USA.
Ijdo
J W
JW
Van Andel
A E
AE
Wu
C
C
Padula
S J
SJ
Fikrig
E
E
D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis; D015748:Borrelia burgdorferi Group / Q000302:isolation & purification*; D004536:Ehrlichia / Q000302:isolation & purification*; D016873:Ehrlichiosis / Q000453:epidemiology / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D006734:Horse Diseases / Q000175:diagnosis* / Q000453:epidemiology; D006736:Horses; D008193:Lyme Disease / Q000453:epidemiology / Q000662:veterinary*; D011446:Prospective Studies; D013984:Tick Infestations / Q000662:veterinary; D014481:United States / Q000453:epidemiology
D000907:Antibodies, Bacterial