Association of Histophilus somni with spontaneous abortions in dairy cattle herds from Brazil

Abstract

This study investigated the participation of infectious agents in spontaneous abortions and reproductive problems at eight dairy cattle herds from three geographical regions of Brazil. Fourteen aborted fetuses and the organ sections of one cow with history of repeated abortions were received for pathological evaluations and molecular diagnostics. PCR/RT-PCR assays targeted specific genes of abortifacient agents of cattle: bovine viral diarrhea virus (BVDV), bovine herpesvirus 1 (BoHV-1), Listeria monocytogenes, Neospora caninum, Leptospira spp., Brucella abortus, and Histophilus somni. Six fetuses were adequate for pathological investigations; one of these did not demonstrate remarkable pathological alterations. Significant histopathological findings included vasculitis, hemorrhage, and fibrinous thrombosis of the cerebrum (n = 4); necrotizing myocarditis (n = 3); and hemorrhagic enteritis (n = 3). The placenta and uterus of the cow as well as the kidney, pancreas, and liver of her aborted fetus contained H. somni DNA and demonstrated histopathological evidence of histophilosis. All fetuses contained H. somni DNA in multiple organs. Coinfections of H. somni with B. abortus (n = 2), N. caninum (n = 2), BVDV (n = 1), and BoHV-1 (n = 1) were identified; two fetuses demonstrated three pathogens. These findings suggest that H. somni was associated with the spontaneous abortions and reproductive problems of these herds. However, the exact cause of fetal death might not be attributed only to H. somni in all aborted fetuses, since some of these were infected with other abortifacient agents.

Bovine respiratory disease associated with Histophilus somni and bovine respiratory syncytial virus in a beef cattle feedlot from Southeastern Brazil

“…Nevertheless, changes in weather conditions have been identified as one of the probable factors that might have contributed to an increase in BRD (LONERAGAN et al, 2001) and we have observed a significant increase of BRD in feedlot cattle during the dry relative to wet season (Baptista et al manuscript in preparation). However, the direct effects of climatic conditions per se as predisposing factors to the development of BRD has been questioned due to the absence of solid scientific data to support this theory (TAYLOR et al, 2010).…”

“…Further, single and mixed infections of H. somni and H. somni with BRSV and other infectious agents have been identified in dairy calves from Southern Brazil with BRD, where predominant agents of BRD were BRSV (38.1%), BVDV (28.6%), BCoV (33.3%), P. multocida (42.85%), M. bovis (33.3%), and H. somni (19%) (OLIVEIRA, 2014). In addition, since H. somni has been increasingly diagnosed in BRD in beef cattle feedlots as well as in the development of fatal systemic (HEADLEY et al, 2013), neurological (HEADLEY et al, 2015a, and reproductive (HEADLEY et al, 2015b) disease in beef and dairy cattle herds from this country, strategic prophylactic and control measures are necessary to prevent the economic effects of widespread dissemination of this pathogen within the local cattle industry. Collectively, these findings confirmed the theory that H. somni is indeed a potential threat to the cattle industry of Brazil (HEADLEY et al, 2014), where immunization against this important pathogen of ruminants is almost nonexistent.…”

“…Data relative to the occurrence of BRD in Brazil is sparse. We have theorized that H. somni might be a threat to beef cattle feedlots due to the continual diagnosis of this pathogen in respiratory (HEADLEY et al, 2014), reproductive (HEADLEY et al, 2015b), systemic (HEADLEY et al, 2013), and neurological (HEADLEY et al, 2015a) disease syndromes in cattle from different geographical regions of Brazil. Further, BRSV was associated with BRD in several herds from the state of Rio Grande do Sul, Southern Brazil (DRIEMEIER et al, 1997;BRASIL et al, 2013), while a retrospective study identified antigens of BRSV in cattle with bronchointerstitial pneumonia from Southern and Southeastern Brazil (FLORES et al, 2000).…”

Histophilus somni is a potential threat to beef cattle feedlots in Brazil

“…Since we have identified H. somni associated with several clinical manifestations in cattle (Headley and others 2013, Headley and others 2014b), it is likely that this pathogen might have been present in cattle herds from Brazil but probably underdiagnosed. The identification of BoHV-1 in one of these steers during this study is not surprising, since this virus is endemic in most cattle herds of Paraná State (Dias and others 2013), and might have been one of the stressors responsible for the development of the respiratory disease at this feedlot.…”

“…However, the importance of these results lies in the consequences of histophilosis being transformed into a major pathogen of cattle in Brazil, considering that we have characterised the systemic disease (Headley and others 2013, Headley and others 2014a), reproductive manifestations (Headley and others 2014b) and TME (manuscript in preparation) associated with H. somni . Moreover, the consulting veterinarian responsible for a feedlot at which histophilosis was diagnosed in 10% (11/110) of the affected calves that had poor feed conversion ratios and died acutely (Headley and others 2013) has medicated all affected cattle with oxytetracycline and instituted routine vaccination against H. somni which has reportedly resolved the undiagnosed mortality at that holding.…”