Difference between revisions of "Bovine Freemartinism"
Jump to navigation
Jump to search
| (17 intermediate revisions by 4 users not shown) | |||
| Line 1: | Line 1: | ||
== Aetiology == | == Aetiology == | ||
| − | * Results from sexual modification of a '''female twin''' by the in-utero exchange of blood from a male | + | * Results from sexual modification of a '''female twin''' by the in-utero exchange of blood from a male fooetus. |
* Freemartin is XX genetic female, but becomes an XX/XY chimera. | * Freemartin is XX genetic female, but becomes an XX/XY chimera. | ||
* 90% of female calves born co-twin to a male will be freemartins. | * 90% of female calves born co-twin to a male will be freemartins. | ||
| Line 15: | Line 15: | ||
* Mesonephric (Wolffian) ducts persist in the female twin and may form rudimentary male tubular genitalia. | * Mesonephric (Wolffian) ducts persist in the female twin and may form rudimentary male tubular genitalia. | ||
| + | |||
| + | ---- | ||
== Diagnosis == | == Diagnosis == | ||
| Line 20: | Line 22: | ||
* Clinical genital abnormalities | * Clinical genital abnormalities | ||
* Presence of sex chromatin bodies in circulating leukocytes of the male co-twin | * Presence of sex chromatin bodies in circulating leukocytes of the male co-twin | ||
| − | * Chimerism (XX/XY) of [[ | + | * Chimerism (XX/XY) of [[Haematopoiesis_-_Anatomy_%26_Physiology|haematopoeitic cells]]. Blood tests can be used to demonstrate different chromosome complement in nucleated leukocytes and presence of two blood groups in each twin. |
* Rectal palpation and vaginoscopy reveal a shortened vagina | * Rectal palpation and vaginoscopy reveal a shortened vagina | ||
** In calves 1-4 weeks old, the vagina is normally 13-15cm in length compared to 5-6cm in a freemartin. | ** In calves 1-4 weeks old, the vagina is normally 13-15cm in length compared to 5-6cm in a freemartin. | ||
* Vulva and vestibule patent but vestibule or vagina is blind-ended - can be checked using speculum or probe. | * Vulva and vestibule patent but vestibule or vagina is blind-ended - can be checked using speculum or probe. | ||
| + | |||
| + | ---- | ||
== Morphology == | == Morphology == | ||
| Line 33: | Line 37: | ||
* Enlarged clitoris, long tufts of hair round vulva, skin fold from groin to umbilicus. | * Enlarged clitoris, long tufts of hair round vulva, skin fold from groin to umbilicus. | ||
* Vagina never communicates with uterus | * Vagina never communicates with uterus | ||
| − | * | + | * fibrous cords or non-patent uterine tubes. |
* Ovaries are usually small, cord-like thickenings in the ovarian ligament are semniferous tubules. | * Ovaries are usually small, cord-like thickenings in the ovarian ligament are semniferous tubules. | ||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
Revision as of 11:59, 3 July 2008
Aetiology
- Results from sexual modification of a female twin by the in-utero exchange of blood from a male fooetus.
- Freemartin is XX genetic female, but becomes an XX/XY chimera.
- 90% of female calves born co-twin to a male will be freemartins.
- There are two theories to explain this:
- Hormonal Theory
- Hormones from the male twin reach the female through vascular anastamoses between the fused placentae to cause masculinisation of the female gonad.
- Cellular theory
- Exhange of blood-forming cells and germ cells between foetuses.
- Reciprocal exchange results in identical erythrocyte antigen types and sex chromosome chimerism (60 XX/XY).
- Hormonal Theory
- Paramesonephric (Mullerian) ducts do not form or atrophy.
- Mesonephric (Wolffian) ducts persist in the female twin and may form rudimentary male tubular genitalia.
Diagnosis
- Clinical genital abnormalities
- Presence of sex chromatin bodies in circulating leukocytes of the male co-twin
- Chimerism (XX/XY) of haematopoeitic cells. Blood tests can be used to demonstrate different chromosome complement in nucleated leukocytes and presence of two blood groups in each twin.
- Rectal palpation and vaginoscopy reveal a shortened vagina
- In calves 1-4 weeks old, the vagina is normally 13-15cm in length compared to 5-6cm in a freemartin.
- Vulva and vestibule patent but vestibule or vagina is blind-ended - can be checked using speculum or probe.
Morphology
- Gonads range from modified Ovaries to structures resembling Testes which are intra-abdominal and do not descend through the inguinal canal (Cryptorchid).
- No spermatogenesis, sterile.
- Produce Testosterone as the major hormone.
- Rudimentary Uterus and Small Vagina.
- Enlarged clitoris, long tufts of hair round vulva, skin fold from groin to umbilicus.
- Vagina never communicates with uterus
- fibrous cords or non-patent uterine tubes.
- Ovaries are usually small, cord-like thickenings in the ovarian ligament are semniferous tubules.