RUMINANTS

Nutritional chondrodystrophy in beef calves

Josepha DeLay, Kent Charlton, Ann Godkin, Felipe Reggeti

A 200-cow Simmental herd in SW Ontario experienced a cluster of births in which calves had prominent congenital defects. Of the 12 calves born during the early calving season, 10 had noticeably shortened legs and either died immediately (2 calves), or within 12 h after birth (1 calf), or survived but could not stand (7 calves). Herd genetics were stable and were similar to those of several other herds, none of which had identified similar congenital lesions.

Two of the calves that died shortly after delivery were submitted to the AHL for postmortem. Both calves were fully haired and crown-rump length was compatible with full-term gestation. All limbs were short compared to body length (disproportionate dwarfism, Fig.1). There was no evidence of arthrogryposis or spinal deviation. Thyroid gland was markedly enlarged in one fetus, and mildly enlarged in the second fetus, consistent with goiter. BVDV nucleic acid was not detected in thoracic fluid of either fetus by PCR.

Histologically, lesions were limited to thyroid glands and physes of long bones, including distal femur, proximal tibia, distal humerus, and proximal and distal radius. Physes were irregularly thin, and there was evidence of chondrodysplasia and premature closure, with a thin discontinuous band of bone oriented parallel to the epiphyseal aspect of the physes. Cartilage was poorly organized, most prominently in the zone of chondrocyte hypertrophy. Lesions in thyroid gland confirmed colloid goiter. Liver manganese levels in both calves were in the deficient range (0.72 and 0.79 µg/g, RI 2-6 µg/g).

Lesions involving physes of long bones in both calves were responsible for the decreased length of these bones and resulting short stature of the calves. In combination with low liver manganese levels, these results support a diagnosis of congenital nutritional chondrodystrophy associated with maternal micronutrient (manganese) deficiency during gestation. Concurrent iodine deficiency is suggested by the presence of goiter in both calves.

Disproportionate dwarfism has previously been associated with manganese deficiency in calves in Canada, New Zealand, and elsewhere. Joint laxity and swelling is also described in affected animals. Low manganese levels in feed have been linked to drought conditions during the previous growing season, as well as to diets inherently low in manganese, including unsupplemented corn silage, as was fed in this herd. Manganese contributes to pathways of glycosaminoglycan synthesis, and deficiency of this essential micronutrient disrupts normal endochondral ossification and bone development. Zinc deficiency is suspected to contribute to similar congenital lesions, although adequate tissue zinc levels were identified in these calves.

Figure 1. Disproportionate dwarfism in a neonatal Simmental calf.	Figure 2. Distal femoral physis – normal (control) calf. Cartilage has an orderly arrangement and maturation sequence, with chondrocytes oriented in discrete parallel columns.	Figure 3. Distal femoral (A) and humeral (B) physes in calf with congenital nutritional chondrodystrophy. Physeal cartilage has a disorganized appearance, with lack of orderly columnar arrangement of chondrocytes and distinct zones of hypertrophy and maturation.

Abortion caused by Candida spp. yeast in a Holstein cow and a Warmblood mare  

Margaret Stalker, Beverly McEwen, Durda Slavic

A 30-cm crown-rump length, 4-mo Holstein aborted fetus and placenta were received at the AHL for postmortem examination in late February 2017, from a herd with a history of multiple abortions 4-6 mo into pregnancy. On histology, there was locally extensive necrotizing placentitis with yeast organisms visible within placental trophoblasts. The fetus had pneumonia with scattered multinucleate cells in airway lumens, as well as conjunctivitis, and colitis with numerous yeast organisms visible within the lumen of the colon. The yeast organism grown in large numbers from the placenta and abomasal content was identified as Candida parapsilosis by MALDI-TOF mass spectrometry.

In early March 2017, an aborted 7-mo gestation Warmblood equine fetus and placenta were received for postmortem. Histologic examination of the chorion revealed necrosis and yeast organisms within trophoblasts, particularly evident in sections from the cervical star area, and the amnion. There was fetal pneumonia with large numbers of budding yeast organisms in alveoli, with rare multinucleate cells. Large numbers of Candida tropicalis were identified in placenta, fetal lung and stomach content fluid.

Candida spp. are dimorphic fungi with both a yeast and a mycelial phase. Although typically considered commensal inhabitants of the digestive and genital tract, these fungi are opportunistic pathogens. Alterations in host mucosal environment or defense mechanisms can result in overgrowth and systemic invasion. Placental localization is assumed to be associated with hematogenous spread following a breach in normal mucosal barriers, although contamination of the uterus during artificial insemination has also been suggested in some cases.

Candida spp. have been implicated as an uncommon cause of sporadic infertility and reproductive problems in cattle, including abortion. A search of the AHL database (2007 to 2017) revealed 6 cases of abortion, all in Holsteins, associated with yeast infections, including C. parapsilosis (2 cases), C. krusei (1 case), Candida spp. (2 cases) and Rhodotorula sp. (1 case).

Candida spp. have also been recognized as causing endometritis and early embryonic death and infertility in mares; Candida abortion in mares is considered to be very rare. There is a single case report of abortion caused by Candida parapsilopsis, and a single case report of C. guilliermondii. Presumably this was an opportunistic ascending infection, and the same risk factors for fungal endometritis (poor uterine contractility, anatomical malformations, and inefficient uterine defense mechanisms) may play a role in allowing establishment of infection.