Detection of bovine viral diarrhea virus (BVDV) in aborted fetus samples is often difficult due to tissue autolysis and inappropriate sampling. Studies assessing different methods for BVDV identification in fetal specimens are scarce. The present study evaluated the agreement between different diagnostic techniques to detect BVDV infections in specimens from a large number of bovine aborted fetuses and neonatal deaths over a period of 22 years. Additionally, genetic, serological, and pathological analyses were conducted in order to characterize BVDV strains of fetal origin. Samples from 95 selected cases from 1997 to 2018 were analyzed by antigen-capture ELISA (AgELISA), nested RT-PCR (RT-nPCR), and real-time RT-PCR (RT-qPCR). In addition, amplification and sequencing of the 5′UTR region were performed for phylogenetic purposes. Virus neutralization tests against the BVDV-1a, BVDV-1b, and BVDV-2b subtypes were conducted on 60 fetal fluids of the selected cases. Furthermore, the frequency and severity of histopathological lesions were evaluated in BVDV-positive cases. This study demonstrated that RT-nPCR and RT-qPCR were more suitable than AgELISA for BVDV detection in fetal specimens. However, the agreement between the two RT-PCR methods was moderate. The BVDV-1b subtype was more frequently detected than the BVDV-1a and BVDV-2b subtypes. Neutralizing antibodies to any of the three subtypes evaluated were present in 94% of the fetal fluids. Microscopically, half of the BVDV-positive cases showed a mild non-suppurative inflammatory response. These results emphasize the need to consider different methods for a diagnostic approach of BVDV associated to reproductive losses.

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The aim of this work was to identify causes of abortion through laboratory investigations in sheep flocks in Uruguay. One hundred cases of abortion, comprising 58 fetuses, 36 fetuses with their placentas, and 6 placentas were investigated in 2015–2021. Cases were subjected to gross and microscopic pathologic examinations, and microbiological and serological testing for the identification of causes of abortion, including protozoal, bacterial, and viral pathogens. An etiologic diagnosis was determined in 46 (46%) cases, including 33 (33%) cases caused by infectious pathogens, as determined by the detection of a pathogen along with the identification of fetoplacental lesions attributable to the detected pathogen. Twenty-seven cases (27%) were caused by Toxoplasma gondii, 5 (5%) by Campylobacter fetus subspecies fetus, and 1 (1%) by an unidentified species of Campylobacter. Fourteen cases (14%) had inflammatory and/or necrotizing fetoplacental lesions compatible with an infectious etiology. Although the cause for these lesions was not clearly identified, T. gondii was detected in 4 of these cases, opportunistic bacteria (Bacillus licheniformis, Streptococcus sp.) were isolated in 2 cases, and bovine viral diarrhea virus 1 subtype i (BVDV-1i) was detected in another. Campylobacter jejuni was identified in 1 (1%) severely autolyzed, mummified fetus. BVDV-2b was identified incidentally in one fetus with an etiologic diagnosis of toxoplasmosis. Microscopic agglutination test revealed antibodies against ≥1 Leptospira serovars in 15/63 (23.8%) fetuses; however, Leptospira was not identified by a combination of qPCR, culture, fluorescent antibody testing nor immunohistochemistry. Neospora caninum, Chlamydia abortus, Chlamydia pecorum, Coxiella burnetii and border disease virus were not detected in any of the analyzed cases. Death was attributed to dystocia in 13 (13%) fetuses delivered by 8 sheep, mostly from one highly prolific flock. Congenital malformations including inferior prognathism, a focal hepatic cyst, and enterohepatic agenesis were identified in one fetus each, the latter being the only one considered incompatible with postnatal life. Toxoplasmosis, campylobacteriosis and dystocia were the main identified causes of fetal losses. Despite the relatively low overall success rate in establishing an etiologic diagnosis, a systematic laboratory workup in cases of abortion is of value to identify their causes and enables zoonotic pathogens surveillance.

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