History
A male Holstein fetus that had been aborted at a gestational age of 7 months and placenta were submitted for necropsy. The fetus weighed 5.8 kg (12.8 lb). The dam resided on a dairy farm (herd size, 30 bovids). The cow aborted the fetus on December 5, 2007, approximately 7 months after artificial insemination. The vaccination history of the herd was unknown.
Clinical and Gross Findings
On gross examination, autolysis of the fetus was moderate, and the crown to rump length was 49 cm. There were multiple to coalescing gray, slightly raised, cutaneous plaques on the skin at the base of the tail, dorsum, and the top of the head around the ears and eyes (Figure 1). Petechiae were present on the skin in the area of the gluteal muscles. The rumen and abomasum were severely distended by clear gelatinous material consistent with amniotic fluid. The lungs were diffusely atelectatic, indicating that the fetus had not taken a breath of air. On the placenta, there were focally extensive, dry, thick, yellow plaques covering the intercotyledonary area and most cotyledons. Some cotyledons were red, decreased in height, and irregular. Results of nitrate testing of a sample of the aqueous humor of an eye were negative.
Photographs of the head and neck of an aborted Holstein fetus (gestational age, approx 7 months; A) and the associated placenta (B). Multiple to coalescing gray cutaneous plaques are present over the head of the fetus, and multiple to coalescing dry, thick, yellow plaques cover the intercotyledonary area and most cotyledons of the placenta. One cotyledon is red and irregular.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Photographs of the head and neck of an aborted Holstein fetus (gestational age, approx 7 months; A) and the associated placenta (B). Multiple to coalescing gray cutaneous plaques are present over the head of the fetus, and multiple to coalescing dry, thick, yellow plaques cover the intercotyledonary area and most cotyledons of the placenta. One cotyledon is red and irregular.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Photographs of the head and neck of an aborted Holstein fetus (gestational age, approx 7 months; A) and the associated placenta (B). Multiple to coalescing gray cutaneous plaques are present over the head of the fetus, and multiple to coalescing dry, thick, yellow plaques cover the intercotyledonary area and most cotyledons of the placenta. One cotyledon is red and irregular.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page →
Histopathologic Findings
Various tissue samples, including placenta, skin, brain, thyroid gland, thymus, and kidneys, were processed for histologic examination. Histologically, multiple areas of the fetal epidermis had orthokeratotic hyperkeratosis (Figure 2). Among the hyperkeratotic layers, multiple clusters of degenerate neutrophils were observed. Multifocally, the underlying dermis was infiltrated by small to moderate numbers of neutrophils and macrophages.
Photomicrograph of a section of some cutaneous plaques in the fetus in Figure 1. Notice the orthokeratotic hyperkeratosis of the epidermis with multiple intracorneal pustules. The dermis is infiltrated by low numbers of neutrophils and macrophages. H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Photomicrograph of a section of some cutaneous plaques in the fetus in Figure 1. Notice the orthokeratotic hyperkeratosis of the epidermis with multiple intracorneal pustules. The dermis is infiltrated by low numbers of neutrophils and macrophages. H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Photomicrograph of a section of some cutaneous plaques in the fetus in Figure 1. Notice the orthokeratotic hyperkeratosis of the epidermis with multiple intracorneal pustules. The dermis is infiltrated by low numbers of neutrophils and macrophages. H&E stain; bar = 100 μm.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
The chorioallantoic membrane was thickened by edema and diffusely congested. There were focally extensive areas of necrosis, loss of epithelium, and remnants of eosinophilic debris around the chorionic villi. At the base of the villi, a few vessels had necrotic walls with mural or perivascular neutrophils. Unstained profiles of nonpigmented fungal hyphae were seen on the surface of the chorioallantoic villi.
Following Gomori methenamine silver staining of sections of skin and placenta, numerous hyphae were detected in the hyperkeratotic layer of the skin; other hyphae were admixed with necrotic debris on the surface of chorioallantoic villi (Figure 3). The hyphae were approximately 3 to 5 μm in width and septate with parallel walls. Sections of skin underwent immunohistochemical staining for Aspergillus spp, and staining was localized to the walls of the hyphae.
Photomicrograph of a section of a plaque in the placenta in Figure 1. In the focally extensive areas of necrosis, numerous longitudinal and transverse sections of hyphae are visible. The hyphae are approximately 3 to 5 μm in diameter and septate with parallel walls and have dichotomous branching. Gomori methenamine silver stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Photomicrograph of a section of a plaque in the placenta in Figure 1. In the focally extensive areas of necrosis, numerous longitudinal and transverse sections of hyphae are visible. The hyphae are approximately 3 to 5 μm in diameter and septate with parallel walls and have dichotomous branching. Gomori methenamine silver stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
Photomicrograph of a section of a plaque in the placenta in Figure 1. In the focally extensive areas of necrosis, numerous longitudinal and transverse sections of hyphae are visible. The hyphae are approximately 3 to 5 μm in diameter and septate with parallel walls and have dichotomous branching. Gomori methenamine silver stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 239, 3; 10.2460/javma.239.3.319
The lungs of the fetus were not inflated (normal fetal atelectasis). Moderate numbers of squamous epithelial cells (squames) admixed with amniotic fluid were seen in the alveolar lumens. Multiple clusters of neutrophils were present in the alveoli. Diffuse congestion of the brain, thyroid glands, thymus, and kidneys was detected.
Morphologic Diagnosis
Multifocal moderate neutrophilic and histiocytic dermatitis with hyperkeratosis, intracorneal pustules, and hyphae and multifocal severe necrotizing placentitis with multifocal chorionic vasculitis and intralesional hyphae.
Comments
Mycotic abortion was the diagnosis for the third-term abortion of the male Holstein of this report. In cattle, mycotic abortions occur sporadically, affecting only a few members of a herd. The abortions are associated with placentitis, necrosis of fetal membranes, and retained fetal membranes in the dams.1,2 Many agents can induce bovine mycotic abortion in cattle including Aspergillus, Absidia, Mucor, Rhizopus, Candida, and Mortierella spp, but infections with Aspergillus spp are the cause of most mycotic abortions.3 Infection with Aspergillus fumigatus is the cause of approximately 75% of mycotic abortions in cattle, and most of the remaining 25% of mycotic abortions have been caused by species of fungi in the class Phycomycetes and by Candida spp.4 In the case described in this report, the morphologic characteristics of the detected organisms and the positive results of immunohistochemical staining for Aspergillus spp suggested that aspergillosis was the most likely cause of the abortion. Abortion of the fetus occurred in December, which is consistent with the finding that the incidence of mycotic abortion is highest in November through April, the period during which gravid cows are typically fed hay and silage and are housed indoors.1
Following infection of a dam, A fumigatus is thought to spread hematogenously to the placenta where it colonizes and contaminates the amniotic fluid and secondarily infects the fetus.5 From the bases of the placentomes, inflammation spreads via maternal crypts to the arcade zone, the potential space between the chorioallantoic membrane and the surface of the caruncles. From the arcade zone, the organism is able to directly access the interplacentomal area and spread between the endometrium and the chorioallantoic membrane throughout the entire placenta.4,6 As a result, inflammation and necrosis of most placentomes of the placenta develop,4 negatively interfering with transplacental transfer of oxygen and resulting in fetal hypoxia.5 The pharynx and surface of the fetus, the umbilical cord, and the alimentary fluid are exposed to the organism, and the fetus becomes systemically infected when the contaminated amniotic fluid is swallowed. Vasoconstriction and decreased oxygenation of nonvital organs induce hyperperistalsis, intestinal sphincter relaxation, and passing of meconium.5 During this period of fetal distress as a result of peripheral hypoxia, active inhalation of amniotic fluid occurs and fetal bronchopneumonia may develop.5 Mixed inflammatory cell exudates containing meconium and epithelial squames are commonly identified in sections of the airways of hypoxic aborted bovine fetuses.5,6 In the case described in this report, squames and clusters of neutrophils were found in the lungs of the aborted fetus suggesting that fetal hypoxia had caused respiratory movements and aspiration of contaminated amniotic fluid. The presence of gelatinous material in the rumen and abomasum indicated that the fetus had swallowed amniotic fluid while distressed in utero.
In addition to mycotic infection, other microbial causes of late-term abortion in cattle include infections with bovine herpesvirus 1, Leptospira interrogans var harjdo-bovis, Leptospira interrogans var pomona, Listeria monocytogenes, Brucella abortus, and Neospora caninum. Bacterial infections are the most frequent cause of infectious abortions in cattle, and it appears that their involvement is dependent on the development of bacteremia.6,7 Bovine herpesvirus-1 induces acute necrotizing endometritis; the resultant histopathologic changes range from lymphocytic endometritis to severe diffuse necrotizing metritis.8 Leptospirosis causes septicemia in the dam; weeks after the septicemic phase, placentitis develops and abortion occurs during the last third of gestation. During the eighth through the ninth month of gestation, infection with L monocytogenes is known to cause abortion and placentitis. Placental lesions associated with L monocytogenes infection include severe necrotizing and suppurative inflammation of the cotyledons and the intercotyledonary areas; hepatomegaly and multifocal necrotizing hepatitis are present in the fetus.2,8 Brucellosis as a cause of abortion in cattle can be ruled out on the basis of evidence of pneumonia and granulomas in the lungs, liver, spleen, and lymph nodes of the fetus.2,8 Lastly, N caninum infection can cause abortion when the gestational age of the fetus is 3 to 9 months; in such cases, mononuclear inflammatory cells are detectable in the placenta and multiple necrotic foci are present in the liver, heart, and brain of the fetus.2,8
Abortions in cattle are associated with considerable monetary loss. Abortions that occur later in pregnancy will be more costly because of the dam's prolonged recovery and concomitant medical problems. Rebreeding may not be advisable after a late-term abortion because of the likelihood of decreased production during the subsequent lactation and the possibility that the dam may serve as a disease carrier to other animals in the herd.9 Although bovine mycotic abortion occurs infrequently, A fumigatus is implicated in most cases; if the infective organism is not identified and infection of more than 1 animal in a herd occurs, the potential for financial losses increases.9 Control of mycotic abortion is aided by removal of prominent sources of conidia and mycelia elements, such as moldy hay and bedding.9
References
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Dailey RA. Abortion in dairy cows and heifers. Dairy integrated reproductive management. West Virginia University. Available at: www.wvu.edu/∼Agexten/forglvst/Dairy/dirm24.pdf. Accessed Apr 10, 2010.
