Characterization of the Microanatomy and Histopathology of Placentas From Aborted, Stillborn, and Normally Delivered Alpacas (Vicugna pacos) and Llamas (Lama glama)

Abstract

From 2002 to 2007, 101 camelid abortions and stillbirths were submitted to the Veterinary Diagnostic Laboratory at Oregon State University (84 alpacas [Vicugna pacos], 13 llamas [Lama glama], 4 unknown). For most cases (n ¼ 67), a cause was not determined by routine testing. Eighty-five submissions included placenta for microscopic examination, of which 55 were from abortions to unknown causes (idiopathic). Microscopic features of placentas from abortion/stillbirth were compared with those from 19 camelids delivered normally (6 alpacas, 12 llamas, 1 unknown) and with those from 4 alpaca fetuses of known gestational age collected during the dam's necropsy. The most common microscopic findings in abortion/stillbirth placentas were mineralization (n ¼ 57) and mucinous edema (n ¼ 27) of the chorioallantoic stroma. One or more of these features were also observed in 22 of 23 placentas from normal pregnancies/deliveries and therefore interpreted as incidental findings. The comparison of alpaca placentas after matching for gestational parameters (crown-rump length, weight, days of gestation; n ¼ 41) revealed hypoplasia of placental villi in 5 of 22 idiopathic abortions and in 1 abortion due to umbilical torsion; hypoplasia was further suspected in an additional 6 abortions of unknown cause and 2 abortions of known cause. The identified villous hypoplasia is assumed to have resulted in placental insufficiency. When placental insufficiency is included as cause, idiopathic abortions are reduced from 66.2 to 47.9% of alpaca cases with histopathologic examination of placenta and from 66.3 to 52.5% of alpaca and llama abortions overall. This study also permitted the generation of a linear regression curve correlating alpaca fetal crown-rump length with fetal age.Keywords abortion, alpaca, histopathology, llama, mineralization, mucin, placenta, villous hypoplasia Annual infertility rates of alpacas (Vicugna pacos) and llamas (Lama glama) range from 30 to 50%, with abortions and stillbirths adding approximately 10% to reproductive losses. 37 In most cases, the etiopathogenesis of alpaca and llama abortions remains undetermined. 6,24,37 The large percentage of idiopathic abortions and stillbirths in New World camelids, combined with the void in the current literature on abortions and their causes in these species, presents a problem for attending veterinarians and diagnosticians 20,37,40 and precludes the development of preventative strategies. In cattle, a portion of idiopathic abortions may be due to abnormal genetic, hormonal, metabolic, or developmental factors, which are difficult to identify in routine diagnostic laboratory submissions.4 Placental abnormalities, including placental insufficiency, that may result in fetal distress syndrome and death are commonly diagnosed causes of equine abortions and stillbirths. 13,16,25,35 As in the horse, the placenta of alpacas and llamas is epitheliochorial and diffuse, and the maternofetal interface develops synchronously. 11,28,29 This raises the question to whether microa...

Macroscopic evaluation of the placenta of the alpaca (Vicugna pacos)

“…The chorionic surface should be red and velvety (Morton, ; Tibary et al, ) and have normal hypovillous areas at the tips of the horns (corresponding to the uterotubal junctions), at the cervical star (on the body or corpus, where there is contact with the cervix) and along the medial aspect of each horn (Pearson et al, , ; Schaefer et al, ; Tibary et al, ). Chorionic inflammation is easily detected as the placenta will be thick and leathery (Tibary et al, ).…”

“…In case of stillbirth, abortion or premature birth, the placenta should be visually examined, as well as sent for histopathology, since a large percentage (66.3%) of abortions and stillbirths is still classified as idiopathic. Mineralization and mucinous oedema of the chorioallantoic stroma is often found in normal and aborted placentas, but villous hypoplasia was more often seen in aborted placentas (Schaefer et al, ).…”

“…In case of pregnancy loss, abortion, stillbirth or premature birth, the placenta should be properly examined to detect any abnormalities such as incompleteness, placentitis, oedema or any other abnormalities (Pearson, Rodriguez, & Tibary, ; Schaefer et al, ; Tibary et al, ).…”

Double ovulation and occurrence of twinning in alpacas ( Vicugna pacos )

“…Factors involved in the maintenance of twin pregnancy to later stages of gestation remain speculative, but establishment of the pregnancies in different horns and the role of uterine size or capacity are plausible. As suggested by the pathologic studies on twin abortions, the starvation theory (placental insufficiency) is most likely the cause of reduction [19].…”

“…Abortion is likely due to placental insufficiency. Common placental lesions associated with twin abortion in that study included increased avillous areas and mineralization [19]. Although twin births are extremely rare in camelids, the outcome for the dam and neonates is often poor due to increased rate of dystocia, prematurity, and poor viability of the neonates [20,21].…”