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  Discussion on Research Summary: PHF and Abortion
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DrO

Posted on Wednesday, Nov 12, 2008 - 11:56 am:

I had to go back 13 years to find another report of naturally acquired PHF induced abortion. Also found was a experiement that helps with the incidence of abortion following infection in the first 1/3rd of pregnancy. For more see the article on Potomac Horse Fever which has been recently updated.
DrO

J Vet Diagn Invest. 2008 Nov;20(6):827-30.
Abortion in a horse following Neorickettsia risticii infection.

Coffman EA, Abd-Eldaim M, Craig LE.

University of Tennessee, College of Veterinary Medicine, Department of Pathobiology, 2407 River Drive, Knoxville, TN 37996-4542. linden@utk.edu.

A pregnant 18-year-old Quarterhorse mare presented with fever, anorexia, tachycardia, tachypnea, and gastrointestinal hypermotility at day 68 of gestation. Potomac horse fever was diagnosed based on polymerase chain reaction (PCR) analysis of whole blood and a high antibody titer to Neorickettsia risticii. The mare made a rapid clinical recovery following antibiotic therapy, but aborted 98 days later. Necropsy on the aborted fetus revealed lymphohistiocytic colitis, lymphadenitis, myocarditis, and hepatitis. The placenta was grossly and histologically normal. Formalin-fixed lymph node, thymus, liver, and colon taken from the aborted fetus were positive by PCR for N. risticii DNA. Potomac horse fever is a common disease in horses that may result in delayed abortion. The microscopic lesions in the fetus are characteristic, and the diagnosis can be confirmed by PCR on formalin-fixed tissues.

J Vet Diagn Invest. 1995 Apr;7(2):201-5.
Identification of Ehrlichia risticii as the causative agent of two equine abortions following natural maternal infection.

Long MT, Goetz TE, Whiteley HE, Kakoma I, Lock TE.
Department of Veterinary Medicine, College of Veterinary Medicine, University of Illinois, Urbana 61801, USA.

Two pregnant mares diagnosed as having equine monocytic ehrlichiosis based on history, clinical signs, and high serum antibody titers to Ehrlichia risticii aborted subsequent to recovery from illness. Mare 1 and mare 2 experienced clinical illness at 120 and 143 days of gestation and aborted at 203 and 226 days of gestation, respectively. The fetuses were expelled in fresh condition, and both mares retained their placentas upon abortion. Gross findings for the fetuses included meconium staining and petechiation of external surfaces. Internally, there was increased volume of feces within the small and large intestines and liver discoloration with enlargement. Microscopic findings included lymphohistiocytic enterocolitis, hepatitis, and myocarditis. Lymphoid hyperplasia and depletion were present in spleen, thymus, and lymph nodes. Ehrlichia risticii was recovered from bone marrow, spleen, lymph node, colon, and liver of the first fetus and bone marrow and colon of the second fetus. Electron microscopic evaluation of the organism isolated in cell culture revealed morphology consistent with E. risticii. The isolated organism was inoculated into a naive pony, and this pony developed high levels of antibody against E. risticii, became ehrlichemic, and developed clinical signs of depression, anorexia, and mild diarrhea. These findings confirm that E. risticii is an abortifacient under conditions of natural infection and should be considered as a differential diagnosis of equine abortions.

Am J Vet Res. 1995 Oct;56(10):1307-16.
Evaluation of fetal infection and abortion in pregnant ponies experimentally infected with Ehrlichia risticii.
Long MT, Goetz TE, Kakoma I, Whiteley HE, Lock TE, Holland CJ, Foreman JH, Baker GJ.
Department of Veterinary Medicine, College of Veterinary Medicine, University of Illinois, Urbana 61801, USA.

Fetal infectivity of Ehrlichia risticii was investigated in 19 ponies that were E risticii negative on the basis of results of an indirect fluorescent antibody (IFA) test. Thirteen pregnant ponies were infected by IV administration of E risticii between 90 and 180 days of gestation. Six pregnant ponies served as noninfected controls. Each infected pony had clinical signs of equine monocytic ehrlichiosis, was confirmed to be ehrlichemic, and developed an IFA titer to E risticii. Two infected ponies became recumbent, were unresponsive to supportive care, and were euthanatized. After recovery from clinical illness, the remaining ponies were observed throughout gestation for reproductive abnormalities. On abortion, each fetus was necropsied and tissue specimens from the liver, bone marrow, spleen, colon, and mesenteric lymph nodes were inoculated into canine monocyte cell cultures. Six infected ponies aborted at a mean 217 days of gestation, which was between postinoculation days 65 and 111. Five fetuses were recovered for evaluation, and E risticii was isolated from 4 of them. All 5 fetuses recovered had similar histologic finding, including enterocolitis, periportal hepatitis, and lymphoid hyperplasia with necrosis of the mesenteric lymph nodes and spleen. All 5 fetuses tested negative for IgG to E risticii, although 3 had low IgM titer to E risticii. The remaining 5 infected ponies had normal parturition. Presuckle IFA titer to E risticii was measured in 4 of the term foals, and results for 3 were positive. Two foals from infected ponies were monitored for 6 months and daily gain in body weight was comparable to that of a control foal. None of the control ponies became ill or seroconverted during the clinical illness phase, and none aborted throughout gestation Two control ponies seroconverted to E risticii 6 weeks before parturition. Results of this study indicate that E ristcii is a primary abortifacient under experimental conditions.

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