ORCID Profile
0000-0003-0285-8679
Current Organisations
University of Pretoria
,
University of Pretoria Faculty of Veterinary Science
,
University of the Witwatersrand
,
Universiteit Utrecht
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Publications
Ovarian function and pregnancy outcome in pony mares following immunocontraception with native and recombinant porcine zona pellucida vaccines
Publisher: Wiley
Date: 29-02-2016
DOI: 10.1111/EVJ.12557
Abstract: Few studies have investigated ovarian function in the mare undergoing porcine zona pellucida (pZP) immunocontraception despite reported ovarian dysfunction in other species. This study aimed to describe ovarian function and oestrous cyclicity in pony mares following treatment with either the conventional pZP vaccine or a novel recombinant form of the vaccine derived from porcine ZP3 and ZP4 (reZP). In addition, the contraceptive efficacy of pZP vs. reZP was assessed. Blinded, randomised, prospective clinical trial. Mares (n = 21) were randomised into 3 groups of 7: Group I received the pZP vaccine, with a booster 5 weeks later Group II received the reZP vaccine, with a booster 5 weeks later and Group III (controls) received 2 treatments, 5 weeks apart, of saline and adjuvant alone. Mares underwent weekly monitoring via transrectal palpation and ultrasound examination of the reproductive tract, with daily monitoring during oestrus. Data were collected over a 24 week period coinciding with the physiological breeding season treatments commenced in Week 4. Serum s les were obtained for antibody titres and ovarian steroid level analyses at 7 day intervals. Cycling mares were bred via fresh semen artificial inseminations over a maximum of 2 consecutive oestrous cycles, commencing 5 weeks post booster vaccination. Control mares cycled throughout the trial. After treatment, 6 of 7 pZP mares (86%) and one reZP mare (14%) had an extended anoestrus that correlated with basal serum oestradiol and progesterone levels. All mares resumed cyclicity by 10 months post treatment. Pregnancies were diagnosed in all controls, 4 reZP- (57%) and none of the pZP-immunised mares. The current study demonstrates the reversible suppression of ovarian function in pony mares following treatment with pZP. The effect of the reZP vaccine on pregnancy outcome requires further investigation.
Ovarian dysfunction associated with zona pellucida–based immunocontraceptive vaccines
Publisher: Elsevier BV
Date: 02-2017
DOI: 10.1016/J.THERIOGENOLOGY.2016.09.018
Abstract: Despite more than 40 years of research into zona pellucida (ZP)-based vaccines, relatively little is known about their mechanism of action. Early research demonstrated precipitation of ZP glycoproteins by antiovarian antiserum, rendering oocytes resistant to sperm binding in vitro. Subsequent work showed significantly decreased fertilization rates following passive immunization, sparking interest in anti-ZP immunocontraception for human and animal use. The primary mechanism of action of ZP vaccines is generally considered to be an antibody-mediated interference with sperm-oocyte binding and/or fertilization. However, this mechanism of action excludes the potential for ovarian dysfunction associated with anti-ZP treatment in some species. A review of relevant literature in pertinent model, domestic and wildlife species reveals a variety of previous and current hypotheses for ovarian effects following ZP-based immunization. Ovarian dysfunction has been suggested to be a species-specific response. In addition, cytotoxic T-lymphocytes and the use of Freund's adjuvants have been suggested to play a role. Finally, the type and extent of glycosylation of ZP antigens have been proposed to influence ovarian effects. The validity of these hypotheses is re-examined in the light of current knowledge. Further investigation of ovarian function in species believed to be resistant to the ovarian effects of anti-ZP vaccines is warranted. To this end, anti-Müllerian hormone may provide a novel tool for the assessment of ovarian function during ZP-based immunocontraception, particularly in wildlife species not amenable to frequent clinical examination.
Non-invasive assessment of the reproductive cycle in free-ranging female African elephants (Loxodonta africana) treated with a gonadotropin-releasing hormone (GnRH) vaccine for inducing anoestrus
Publisher: Springer Science and Business Media LLC
Date: 2012
The use of a GnRH vaccine to suppress mare ovarian activity in a large group of mares under field conditions
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/WR07136
Abstract: The aim of this study was to evaluate the effect of active immunisation against GnRH on ovarian activity and serum progesterone concentrations in a large group of mares (10 control and 55 experimental) under field conditions as a model for wildlife species such as zebra and African elephants. Within the experimental group, mares were sub ided into three age categories: Category 1 (4 years and younger, n = 26), Category 2 (4–10 years old, n = 18), and Category 3 (≥11 years old, n = 11). Experimental mares were vaccinated intramuscularly with 2 mL (400 μg) of the GnRH vaccine Improvac (Pfizer Animal Health, Sandton, South Africa). Control mares received the same amount of saline solution. The vaccinations were repeated 35 days later. The ovaries and reproductive tracts of each mare were examined by means of rectal palpation and ultrasonography on Days 0, 35 and 70. Blood was collected weekly for determination of serum progesterone concentration until Day 175. On Day 35 after primary vaccination all of the control mares and 14.5% of the experimental mares showed evidence of ovarian activity on the basis of clinical examination and serum progesterone concentration. On Day 70, all control mares and none of the experimental mares showed evidence of cyclic activity. No age-related effect within treatment groups was found. The serum progesterone concentration indicated that all experimental mares remained in anoestrus until Day 175. Five of the control mares fell pregnant between Days 35 and 70. The five non-pregnant control mares continued to cycle until the end of the observation period. Having achieved such promising results in this trial we now plan to test the GnRH vaccine in Burchell’s zebra mares and African elephant cows.
Missense Mutation in the Ligand-Binding Domain of the Horse Androgen Receptor Gene in a Thoroughbred Family with Inherited 64,XY (SRY+) Disorder of Sex Development
Publisher: S. Karger AG
Date: 2016
DOI: 10.1159/000444991
Abstract: Disorders of sex development (DSD) have long been documented in domestic animal species including horses. However, there is only a single report of an androgen receptor i (AR) /i mutation causative of such a DSD syndrome in a horse pedigree. Here, we present a new familial i AR /i mutation in horses. A missense mutation (c.2042G C) at i AR /i exon 4 explains the segregation of the DSD in a Thoroughbred horse pedigree. The mutation, expected to affect the ligand-binding domain of the AR protein, led to complete androgen insensitivity of 64,XY SRY+, testicular DSD in iduals. Additionally, the design of a PCR-RFLP technique provided an accurate molecular test for the identification of horses carrying the mutation.
Laparoscopic Sterilization of the African Lioness (Panthera leo)
Publisher: Wiley
Date: 08-01-2013
Related Organisations
University Of Pretoria Faculty Of Veterinary Science
Location: South Africa
Related Funding Activities
No related grants have been discovered for Martin Schulman.