Short Communication
Transplacental Transmission of Trypanosoma evansi From Experimentally Infected Donkey Mare to Neonatal Foal

https://doi.org/10.1016/j.jevs.2015.02.004Get rights and content

Highlights

  • The present study confirmed transplacental transmission of Trypanosoma evansi in a neonatal foal in an experimentally infected donkey.

  • Transfer of antitrypanosomal immunoglobulin G antibodies in a neonatal foal born to a T. evansi experimentally infected mother donkey could not be demonstrated.

  • Trypanosoma evansi was demonstrated in neonatal foal blood with pathological lesions in the vital organs.

Abstract

The present study is an observation of transplacental transmission of Trypanosoma evansi in a donkey neonatal foal. One experimentally infected pregnant donkey mare gave a normal birth to a foal after 3 months of experimental infection. No trypanosome was seen in wet blood film (WBF) on microscopic examination in the experimentally infected donkey mare at the time of foal birth; however, in serum, a significant level of antitrypanosmal immunoglobulin G (IgG) antibodies on enzyme-linked immunosorbent assay (ELISA) and many immunodominant polypeptide bands on immunoblotting were observed. In the neonatal foal, live moving trypanosomes were observed in WBF just after birth before colostrum feeding. The foal serum sample (collected before colostrum feeding) was found negative on ELISA and immunoblotting indicating that IgG antibodies has not crossed placental barrier in the mother donkey. After 24 hours of birth, the clinical symptoms appeared in the foal showing recumbency, unable to stand and suckle, and poor reflexes. The foal was administered fluid therapy, but could survive only up to 36 hours after birth. The study indicated transplacental transmission of T. evansi in the donkey, but the mechanism responsible for crossing the placental barrier needs to be further elucidated.

Introduction

Trypanosomosis, caused by Trypanosoma evansi, is an important disease of equines causing high morbidity and mortality. Trypanosoma evansi has the widest geographic range of all the pathogenic trypanosome species and is a major constraint to livestock productivity on the three continents Asia, Africa, and South America. Trypanosoma evansi infects a wide range of domestic animals particularly camels, horses, cattle, buffaloes, and pigs [1]. Abortions associated with trypanosomosis have been reported in buffaloes, cattle, pigs, and camels [2], [3], [4], [5], [6].

The equine placenta is diffused epitheliochorial type, and the molecules have to cross maternal endothelium, uterine epithelium, trophoblast, and fetal endothelium to reach fetal bloodstream. The maternal antibodies do not cross the equine epitheliochorial placenta, and newborn foals receive maternal antibodies through colostrum [7]. Trypanosoma evansi is not a strict blood parasite and is capable of invading extravascular tissues of infected animals including brain [8], [9], [10], [11]. Several mechanisms have been proposed by earlier workers to penetrate blood-brain barrier including entrance through incomplete sites such as sensory ganglia and circumventricular organs, deposition of immune complexes in the choroid plexus, increase in vascular permeability, and releasing toxic substances by trypanosomes [12], [13]. An interaction between the trypanosomes and the host may cause placental tissue damage and facilitate parasitic crossing of placental barrier. The present study is an observation of transplacental transmission of T. evansi in a donkey neonatal foal.

Section snippets

Experimental Infection of the Donkey Mare

Trypanosoma evansi isolate was collected from a naturally infected camel and cryopreserved in liquid nitrogen in Parasitology Laboratory, National Research Centre on Equines, Hisar, India. In our earlier experiment, one group of donkey mares was infected experimentally with 2 × 106 trypanosomes per animal subcutaneously. In this experimentally infected group, one donkey mare delivered a normal foal after 3 months of experimental infection. The status of gestation was unknown for this mare at

Clinical and Parasitological Findings

The donkey mare gave a normal birth to a foal after 3 months of experimental infection. Blood samples of the foal (before colostrum feeding) and the experimentally infected donkey mare were collected and tested microscopically by WBF examination. Live moving trypanosomes were observed in foal's blood; however, no parasite was seen in blood of the donkey mare on WBF examination. The microscopic examination of Giemsa-stained blood smear prepared before colostrum feeding shown T. evansi infection

Discussion

The present study is an observation of transplacental transmission of T. evansi infection in a neonatal foal, confirmed by the presence of trypanosomes on microscopic examination of WBF, born to an experimentally infected donkey mare after 3 months of experimental infection. In earlier studies, the presence of T. evansi had been demonstrated in aborted fetuses in naturally infected buffaloes and camels [2], [6]. In one study, transplacental transmission of T. evansi had also been confirmed by

Conclusions

The study indicated the transplacental transmission of T. evansi in a neonatal foal born to an experimentally infected donkey mare. The stage of gestation at which the dam acquires T. evansi infection is important to determine the pathogenesis of reproductive disturbance in equines. To explain the mechanism responsible for crossing the placental barrier by T. evansi in pregnant animals, further detailed study is required.

Acknowledgments

The authors are thankful to the Director, ICAR-National Research Centre on Equines, Hisar, India, for providing necessary research facilities to carry out the present study.

Ethics: All authors certified that in the present work, the animal experimentation was carried out after the approval of Institute Animal Ethic Committee and as per guidelines of the Committee for the Purpose of Control and Supervision of Experiments on Animals, Animal Welfare Division, Government of India.

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