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Animal Reproduction Science 60–61 2000 131–143 www.elsevier.comrlocateranireprosci
Embryonic mortality and embryo–pathogen interactions
G. Vanroose , A. de Kruif
1
, A. Van Soom
2 Department of Obstetrics, Reproduction and Herd Health, Faculty of Veterinary Medicine, UniÕersity of Gent,
Salisburylaan 133, 9820 Merelbeke, Belgium
Abstract
Ž .
Embryonic mortality EM has a substantial impact on the fertility of domestic animals. Most of the embryonic losses occur during the first days after fertilization and during the process of
implantation. Causes of EM can be divided into infectious and non-infectious categories. Primary attention has often been given to infectious agents but non-infectious causes probably account for
70 or more of the cases of embryonic death.
Infection of the embryonic environment can be caused by specific and non-specific uterine pathogens. Specific uterine infections are caused by a number of viruses, bacteria and protozoa
that enter the uterus by the haematogenous route or via the vagina. Non-specific pathogens are mainly bacteria that enter the uterus by ascending infection. Uterine pathogens may cause EM by
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changing the uterine environment endometritis or by a direct cytolytic effect on the embryo. Ž
Non-infectious causes of EM such as chromosomal aberrations, external factors e.g., high .
Ž ambient temperature and nutritional factors and maternal factors e.g., hormonal imbalances and
. age are multifactorial and difficult to diagnose. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Embryonic mortality; Infection; Embryo–pathogen interaction
1. Introduction
Ž Ž
. .
Prenatal losses embryonic mortality EM and fetal death are the most important causes of reproductive losses in animals and have a substantial impact on the profitabil-
ity of the animal production.
Corresponding author. Tel.: q32-9-264-75-61; fax: q32-9-264-75-63. Ž
. Ž
. E-mail addresses: geert.vanrooserug.ac.be
G. Vanroose , aart.dekruifrug.ac.be A. de Kruif ,
Ž .
ann.vansoomrug.ac.be A. Van Soom .
1
Tel.: q32-9-264-75-63
2
Fax: q32-9-264-77-97 0378-4320r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved.
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PII: S 0 3 7 8 - 4 3 2 0 0 0 0 0 0 9 8 - 1
Most of these losses occur during the embryonic period of gestation. This period Ž
extends from fertilization to the completion of the differentiation stage an embryo is .
considered a fetus when mineralization begins . Furthermore, most of the embryonic losses occur during the first days after fertilization and during the process of implanta-
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tion Wathes, 1992 . The adhesion stage of the implantation process in domestic animals starts at day 14 in sows, days 15–16 in ewes, day 16 in bitches, days 18–20 in goats,
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days 21–22 in cows, and days 36–40 in mares Gandolfi et al., 1992; Guillomot, 1995 . Ž
EM has been estimated to be about 20–40 in cows Lopez-Gatius et al., 1996; Hanzen
´
. Ž
. et al., 1999 ; 10–40 in sows Lambert et al., 1991; Gordon, 1997 , 10–30 in goats
Ž .
and 15–60 in mares Allen, 1992; Bergfelt and Ginther, 1992 . Fetal death has been Ž
. Ž
estimated to be about 5 Lambert et al., 1991 , but may exceed 10 Lopez-Gatius et
´
. al., 1996 .
Prenatal losses can be caused by infections and by non-infectious factors. Primary attention has often been directed to infections but non-infectious causes probably
Ž .
account for 70 or more of the cases Christianson, 1992 . Non-infectious causes are often multifactorial and are difficult to diagnose.
This paper aims to give a review of the causes of EM in domestic animals, and to focus upon some species-specific causes. Particular focus is concentrated on embryo–
pathogen interactions in the discussion.
2. Infectious causes
