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Pathogenesis of Retained Placenta
• In 80% animals placenta is expelled within 2-3 h after delivery
– Get septic if retained for 12 h
• Incidences in non-infected cattle (7%)
• Retention of placenta is a clinical symptom of
– Premature parturition
– Nutritional deficiency
– Metabolic diseases
– Infections• Abortions; IBR
• Brucellosis carrier (20-50%)
– Post obstetrical handling
• Duration of pregnancy and Placental retention
– Earlier abortion placenta come along
– Late abortion placenta retained
– Premature birth placenta retained
Loosening process in Placentomes
• Preparatory changes in the last month of gestation
• Placental connective tissues collagenized • Flattening of the maternal crypts • Appearance of binuclear giant cells
– Resorptive phagocytic activities
• At onset of parturition the placentome tissues become loose
• Microscopic Structure of the Ruminant Placenta
• A prominent feature of the ruminant placenta is the presence of large numbers of binucleate cells.
• These cells arise early as part of the foetal trophoblast from cells that fail to undergo cytokinesis following nuclear division.
• They invade and fuse with caruncular epithelial cells to form small syncytia.
• Binucleate cells secrete the hormone placental lactogen.
• Ruminants basically have an epitheliochorial placenta, but because the uterine epithelium is modified by invasion and fusion of binucleate cells, its structure is generally referred to as synepitheliochorial.
• Prior to detailed study of these structures, it was thought that the maternal epithelium was eroded away, leaving trophoblast in contact with maternal connective tissue.
• Constantly changing uterine pressure leading – Alternating ischemic & hyperemic conditions– Changes in the surface area of the fetal
chorionic villi.• Caruncles are pressed against the fetus (uterine
contractions)
– After fetal expulsion; • Umblical cord ruptures
– Surface area of chorionic villi reduces bec. of ischemia of the fetal villi
• Postpartum uterine contractions completes the detachment process
Factors affecting loosening Process of placentomes
• Biochemical factors (Selinium or PGF2 in placentomes)
• Histological factors– Infectious (placentitis)
– Noninfectious
» Immature placentomes Advanced involution
» Uterine atony Edema of the chrionic villi
» Necrosis of the villi hyperemia of the placentomes
Disturbance of the loosening process
• Immature placentome– Fetal expulsion
• Days before 120 no placental retention
• Days 121-150 placenta retained in 15%
• Days 240 – 265 placenta retained in 50%
Cont…
• Inadequate estrogen – No swelling of the collagen tissue fiber and
maternal crypts – Maturity of placento-uterine junctions occur
2-5 days before parturition– Weaker uterine contractions
• Noninflamatory edema of Chorionic villi
• Necrotic area in placentomes
Cont…
• Advanced involution of the placentome
• Hyperemia of placentome bec. of early closure of umblical blood vessels
• Placentitis and cotyledonitis
• Uterine atony
• Symptoms:– Digestive: Anorexia, constipation, low milk prod.
Rapid wt. Loss, inability to rise
– Nervous: depression, trembling, nervousness
• Treatment:– Gentl try to pull without breaking placenta – Milk animal or let calf suckle as early as possible– Oxytocin 10 IU 4 times after every 4 hours (during 24 h
after calving) – Glucose 25% (iv) or sodium propionate or propylene
glycol – Antibiotics for 5 to 7 days – Protease or collagenase enzyme (umbilical vains) 1 U / 3
gm tissue