It’s frustrating for veterinarians to try and make a definitive diagnosis of an ongoing health challenge if they lack the tools in the toolbox to help the situation.
One such disease of young suckling piglets is Rotaviral enteritis (diarrhea).
Rotavirus: the organism
While there are many devastating viral diarrheas on western Canadian pig farms, Rotavirus is very common. Based on surface protein patterns, western Canadian rotaviruses are grouped into four main categories: groups A, B, C and D.
Historically, Rota A was most frequently found in very young piglets, but in recent years, Rota B and Rota C have been common as well, often in various combinations.
Being a non-enveloped virus, meaning there is no fatty coating surrounding the virus, these pathogens have evolved to be very resistant to degradation by disinfectants, drying, freezing and heating.
Normal small intestines are lined by microscopic folds (villi) appearing as peaks and valleys, which significantly increase the intestine’s surface area and ability to help digest food and absorb nutrients.
The virus infects the cells lining these villi and once infected, these intestinal cells lose function and eventually slough off, creating a microscopic lesion we call villous atrophy.
The lining of the intestine loses the peaks and valleys and becomes flattened, with significantly reduced surface area for digestion to take place. The result is a piglet that is able to continue drinking milk, but is unable to digest or absorb it. Many farrowing techs can smell the scour as they walk into a room because of the undigested milk fats and proteins helping large intestinal bacteria in the piglets colon to thrive.
Many neonatal (newborn) diarrheas are indistinguishable from each other with similar clinical presentations. While commonly observed at higher frequency in first parity (gilt) litters, Rota can be seen in piglets from any parity. Shortly after becoming infected through exposure to virus in the environment, piglets will begin vomiting milk curd and within hours develop watery yellow diarrhea.
It’s common to see piglets piling on top of each other in corners or on the heat pads after being dampened by the scour material and becoming chilled. The piling behaviour helps to retain body heat and stay warm.
In time, piglets become gaunt and mildly dehydrated. Rotavirus seldom causes piglet mortality, but it stunts the growth of suckling piglets, which creates more variation in size at weaning and gut health challenges downstream in the weanling barn.
Disease control and management
Until recently, the tools in the toolbox were limited to basic strategies that resulted in mediocre success. Internal biosecurity has always been important on swine farms by preventing movement of the pathogen within the farrowing rooms.
While washing with hot water at high pressure (more than 2,000 p.s.i.) before placing another sow into the crate is important, farms will also use detergents during the wash to remove biofilm and organic material from surfaces, rotate a variety of different disinfectants and allow crates to thoroughly dry before reloading. Simple strategies can help, such as not stepping into farrowing crates, which can leave behind a contaminated footprint, changing gloves between handling piglets from different litters and reducing piglet stressors such as drafts and chills.
Reducing piglet exposure to Rota is only half the job. Diarrhea protection, regardless of the pathogen, is driven through lactogenic protection, which is consistent and frequent milk consumption by the piglet.
Sows will concentrate antibodies into their milk and provide a milk meal to their litter approximately every hour. Provided the piglets get their meal every hour, their intestinal tract is bathed with protective antibodies and if we have the right antibodies in the milk, they are protected from developing diarrhea.
We can guide antibody production through the strategic use of vaccines administered to sows before they farrow, giving the sows time to concentrate those protective antibodies into their mammary glands.
There has been a Rota A vaccine on the market for years, but we know many circulating Rota A strains are not similar to the vaccine strains and therefore we aren’t able to stimulate the correct antibodies in the sow to protect piglets. In addition to that, the commercial vaccines do not offer piglet protection for Rota B and C challenges.
Recently, another Rotavirus management tool was approved in Canada. We now have access to a new vaccine technology that uses messenger RNA to stimulate protective antibody production by the sow. This technology may sound familiar because it is similar technology to what Pfizer-BioNTech and Moderna use in their COVID-19 (SARS-CoV-2) vaccines.
The same technology allows us to use messenger RNA that codes for antigen-proteins from the surface of Rotavirus (we can choose Rota A or B or C or any combination of these found on a farm) to prepare custom Rota vaccines for farms.
While the vaccine is new to us, veterinarians and farmers look forward to getting some immunologic help in managing this frustrating disease.
Blaine Tully is a veterinarian and owner of Swine Health Professionals Ltd. in Steinbach, Man