Bovine respiratory disease (BRD) is the costliest disease affecting the cattle industry globally. Orthomyxoviruses, influenza C virus (ICV) and influenza D virus (IDV) have recently been implicated to play a role in BRD. However, there are contradicting reports about the association of IDV and ICV to BRD. Using the largest cohort study (cattle, n = 599) to date we investigated the association of influenza viruses in cattle with BRD. Cattle were scored for respiratory symptoms and pooled nasal and pharyngeal swabs were tested for bovine viral diarrhea virus, bovine herpesvirus 1, bovine respiratory syncytial virus, bovine coronavirus, ICV and IDV by real-time PCR. Cattle that have higher viral loads of IDV and ICV also have greater numbers of co-infecting viruses than controls. More strikingly, 2 logs higher IDV viral RNA in BRD-symptomatic cattle that are co-infected animals than those infected with IDV alone. Our results strongly suggest that ICV and IDV may be significant contributors to BRD.

Nipah virus (NiV) is a highly lethal zoonotic paramyxovirus that emerged in Malaysia in 1998. It is a human pathogen capable of causing severe respiratory infection and encephalitis. The natural reservoir of NiV, Pteropus fruit bats, remains a continuous virus source for future outbreaks, although infection in the bats is largely asymptomatic. NiV provokes serious disease in various mammalian species. In the recent human NiV outbreaks in Bangladesh and India, both bats-to-human and human-to-human transmissions have been observed. NiV has been demonstrated to interfere with the innate immune response via interferon type I signaling, promoting viral dissemination and preventing antiviral response. Studies of humoral immunity in infected NiV patients and animal models have shown that NiV-specific antibodies were produced upon infection and were protective. Studies on cellular immunity response to NiV infection in human and animal models also found that the adaptive immune response, specifically CD4+ and CD8+ T cells, was stimulated upon NiV infection. The experimental vaccines and therapeutic strategies developed have provided insights into the immunological requirements for the development of successful medical countermeasures against NiV. This review summarizes the current understanding of NiV pathogenesis and innate and adaptive immune responses induced upon infection.

Bovine respiratory disease (BRD) is the costliest disease affecting the cattle industry globally. Despite decades of research, the pathophysiology of BRD is not yet fully understood. It is widely believed that viruses predispose cattle to bacterial infection by causing direct damage to the respiratory tract and interfering with the immune system, leading to bacterial pneumonia. BRD remains a major challenge despite extensive vaccination against all major viral pathogens associated with the disease. Orthomyxoviruses (Influenza C & D viruses), have recently been found to infect cattle throughout the United States and are implicated to play a role in BRD. Here, we use the largest cohort study to date to investigate the association of influenza viruses in cattle with BRD. Cattle (n=599) from 3 locations were individually observed and scored for respiratory symptoms using the McGuirk scoring system. Deep pharyngeal and mid-nasal swabs were collected from each animal and were tested quantitatively for bovine viral diarrhea virus, bovine herpesvirus 1, bovine respiratory syncytial virus, bovine coronavirus, influenza C virus (ICV) and influenza D virus (IDV) by real-time PCR. Cattle that have higher viral loads of IDV and ICV also have greater numbers of co-infecting viruses than controls. More strikingly, in BRD-symptomatic cattle, the geometric mean of detectable IDV viral RNA was nearly 2 logs higher in co-infected animals (1.30×104) than those singly infected with IDV (2.19×102). This is strong evidence that viral coinfections can lead to higher replication of IDV. Our results strongly suggest that orthomyxoviruses may be significant contributors to BRD.