Indirect Transmission of Influenza A Virus between Pig Populations under Two Different Biosecurity Settings

Abstract

Respiratory disease due to influenza virus is common in both human and swine populations around the world with multiple transmission routes capable of transmitting influenza virus, including indirect routes. The objective of this study was to evaluate the role of fomites in influenza A virus (IAV) transmission between pig populations separated by two different biosecurity settings. Thirty-five pigs were divided into four experimental groups: 10 pigs (1 replicate) were assigned to the infected group (I), 10 pigs (2 replicates of 5 pigs) were assigned to the low biosecurity sentinel group (LB), 10 pigs (2 replicates of 5 pigs) were assigned to the medium biosecurity sentinel group (MB), and 5 pigs (1 replicate) were assigned to the negative control group (NC). Eight of 10 pigs in the infected group were inoculated with IAV and 36 hours following inoculation, personnel movement events took place in order to move potentially infectious clothing and personal protective equipment (PPE) to sentinel pig rooms. Following contact with the infected group, personnel moved to the MB group after designated hygiene measures while personnel moved directly to the LB group. Nasal swabs and blood samples were collected from pigs to assess IAV infection status and fomites were sampled and tested via RRT-PCR. All experimentally inoculated pigs were infected with IAV and 11 of the 144 fomite samples collected following contact with infected pigs were low level positive for IAV genome. One replicate of each sentinel groups LB and MB became infected with IAV and all five pigs were infected over time. This study provides evidence that fomites can serve as an IAV transmission route from infected to sentinel pigs and highlights the need to focus on indirect routes as well as direct routes of transmission for IAV.

Evaluation of biosecurity measures to prevent indirect transmission of porcine epidemic diarrhea virus

“…Transmission of PEDV with MB protocols may have been limited by low dose of virus, presence of non-infectious virus, inadequate interaction of pigs with contaminated PPE/surfaces, or the decreased efficiency of fecal oral transmission route from these contaminated areas. Similar experiments using an influenza virus transmission model showed a breakdown of medium biosecurity measures after 10 consecutive movements [17]. Swabs from Table 3 Number of porcine epidemic diarrhea virus positive pigs (2nd trial) −1 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 Infection group 0/3 0/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 3/3 Infection group sentinel 0/1 0/ HB group study personnel tested PEDV rRT-PCR negative even on the hair and face.…”

Mathematical Modeling of Influenza A Virus Dynamics within Swine Farms and the Effects of Vaccination

“…In line with experimental evidence, our model includes both direct transmission between pigs in the same room [14], and indirect transmission between pigs in separate rooms [10]. Infection can also spread in the model by the physical movement of swine through the farm.…”

Ecological drivers of African swine fever virus persistence in wild boar populations: Insight for control

“…Understanding mechanisms by which pathogens transmit between hosts is key for defining disease risk and for planning effective control strategies. In addition to direct host‐to‐host or vector‐borne transmission, pathogens can spread through environmental sources, such as through contact with fomites (Allerson, Cardpna, & Torremorell, ), ingestion of contaminated drinking water (Breban, ; Kraay et al, ), contact with contaminated soil (Turner et al, ), contact with contaminated carcasses (Chenais, Ståhl, Guberti, & Depner, ), or carcass scavenging (Brown & Bevins, ; Wille et al, ). Environmental sources of infection can promote pathogen persistence by increasing their likelihood of contact with susceptible hosts because many pathogens can remain viable in the environment longer than they can keep a host infectious.…”