Perinatal Complications in Cetaceans and Manatees, Diagnostic and Treatment Considerations
Michael T. Walsh1; Diedriech Beusse1; Todd R.
Robeck2; Les Dalton2; Forrest I. Townsend3
Reproductively active cetaceans experience gestational and perinatal complications similar to terrestrial species. These may include "false pregnancy", embryonic death, spontaneous abortion, fetal death and retention, dystocia, and maternal death. The most common complication requiring clinical intervention in marine mammals such as cetaceans and manatees is dystocia or abnormal labor or delivery. Fetal causes of dystocia may include large calves, malposition of the fetus, and multiple pregnancies. Maternal causes involving the uterus may include uterine inertia, uterine anomalies, and uterine scarring and adhesions.
Dystocias in wild manatees are more complicated because the time of intervention is usually uncontrolled and the beginning of the problem is undocumented. Animals may be rescued for non-responsiveness, abnormal flotation, injury, or observed abnormal fetal presentation. Of six cases of dystocia in wild manatees one female with a very large fetus died on the way back to the SeaWorld hospital. Three females had various stages of fetal exposure, two with tail presentation and one headfirst. In these three cases the fetus was undergoing necrosis and the females were depressed and obviously toxic. Physical restraint was not applicable so the manatees were sedated with midazolam or masked with isoflurane. Tail first presentations were extracted by incising the paddle for rope placement or by encircling the paddle with a cord. The calf was then extracted after placing lubricant in the uterus and providing a slow steady pulling motion. Two of these three females had severe necrosis of the uterus, were severely toxic and died. The third female survived and was released 1 year after the initial presentation. Two other females who had difficult labor and eventual uterine inertia were transported to the University of Florida for possible Cesarean section. One individual was anesthetized, ultra sounded and the fetus surgically removed. The other was anesthetized, ultra sounded and the fetus removed vaginally. Both individuals were eventually released. One female manatee at SeaWorld experienced a difficult labor that resulted in excessive hemorrhage secondary to a tear of the cervix. This individual developed secondary kidney failure and expired.
Management of cetacean dystocia is similar to other species. Initial evaluation of the mother is based on the knowledge of normal time elements starting with active labor. Observed behavior has included arching, stretching, vulvar protrusion, milk expulsion and eventual protrusion of the head or tail. The time from fetal protrusion to expulsion has varied from one to five hours with complications more likely if it goes beyond five hours. Additional information may be gained through close observation as to the viability of the calf as evidenced by voluntary movement of the exposed portion of the fetus. After 6 hours, if there is no progress, or if there is evidence of fetal death, the clinician may need to consider intervention. Where fetal viability is unknown ultrasound may be used to decide the next step in intervention. If the fetus is alive the clinician may chose between stimulation with oxytocin and calcium, calcium and more time, or attempting to physically aid expulsion. If the fetus is dead the clinician may choose between support with calcium and stimulation with oxytocin, manual removal of the fetus, or stimulation with prostaglandins. Each choice must be weighed as to the pros and cons with the main goal to insure the survival of the mother.
Complications associated with manual removal of a fetus may include excessive stress on the female, laceration or rupture of the reproductive tract, excessive hemorrhage, and secondary septicemia and abscess formation. There are a number of do "nots" that should be considered when pulling a calf. The uterine environment may be excessively dry so it is important to freely lubricate the uterus before any traction is applied. In some cases the vulvar opening is still too small to allow access to the fetus. It has been enlarged in two dolphins by inserting a fluid pressure bag that is slowly distended to a point where an arm may be inserted to grasp the tail or head of the fetus. The role of oxytocin to expel a fetus has also been reexamined even though it is often considered a standard procedure. It was apparent that it was influencing uterine contraction, though often in the presence of a dry environment surrounding the fetus. It was usually more difficult to place lubricant in the tract once the oxytocin was given. In addition, lacerations of the reproductive tract were becoming common secondary complications. In a beluga whale and a manatee, both with a devitalized fetus, oxytocin was not given and the insertion of lubricant and subsequent fetal removal was much smoother with no lacerations.
Other factors that require great care and patience are the amount of pressure applied to the fetus and how quickly it is applied. The common tendency when extracting a fetus is to pull too hard and too fast. This does not allow the reproductive tract time to stretch increasing the likelihood of tears in the tract. The clinician must maintain control of the rate of tension and not allow the progress of fetal movement to rush the fetal removal. Two other techniques can be utilized. Some lacerations may be secondary to the pectoral flippers being out of position. Placement of these should be checked during the extraction if possible. With large dead calves that may result in laceration, a modified fetotomy can be performed to decrease the likelihood of tears. Once the abdomen is exteriorized, it is incised and the abdominal and thoracic organs are removed. This allows the pectoral flippers to collapse inward avoiding additional laceration. Lacerations secondary to calf extraction may occur in the uterus (two dolphins), cervix (killer whale), or vagina (beluga whale)1, or a combination of these sites (one dolphin).
Sedation may also help to facilitate fetal extraction by relaxing the female, increasing cooperation, and prolonging the time available to complete the procedure with out rushing. Midazolam has been used in dolphins, a beluga whale, a killer whale and manatees. Post extraction techniques should include culturing (aerobic and anaerobic) the uterus and the fetus, flushing the uterus and the use of antibiotics. If oxytocin was not originally used then it should be administered after flushing the uterus. Bacterial sensitivity should guide the final choice of antibiotics. The reproductive system should be monitored for drainage and with ultrasound to determine the onset of complications. If possible the animal should be housed away from any males for an extended period of time before considering another pregnancy.
1. Dalton, L.M, T.R. Robeck,and J. McBain, 1994. Dystocias in two beluga whales. IAAAM Annual Conference, CD Rom Archive.