Practical Approaches to Managing Rotavirus in Suckling Pigs

Laura Greiner, PhDCarthage Innovative Swine Solutions, LLC

Rotavirus Infections

• Types of rotavirus of interest– A– B– C

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Pre-wean Mortality

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Rotavirus Type C• Natural Planned Exposure

(NPE) did not provide same control as type A

• No commercial vaccine

• Worked with researchers and autogenous vaccine manufactures– Growing it in lab is difficult– Working on vectors

Rotavirus Type C

• When farms broke with PEDv, rotavirus C symptoms lessened

• Rotavirus C positive cases were not detected for approximately 6 months after the farms were PEDv negative

• Why?

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How PEDv Changed Our Thinking

• Prior to PEDv– Farrowing houses were washed and disinfected– NPE was conducted weekly on soon to farrow females

• During PEDv– Additional sanitation was conducted in the farrowing

house– Whole herd NPE was conducted multiple times– Gilt litters appeared to be more susceptible to infection– Discovered that timing is everything in addressing an

enteric infection

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Understanding Enteric Immunity

• Sow to piglet• Antibodies (IgA and IgG) • Timing• Live virus vs killed virus• Logs of infectious material• Whole herd vs sub-group

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Toll-like receptor signaling in the intestinal epithelium: how bacterial recognition shapes intestinal functionMaria T. AbreuNature Reviews Immunology 11, 215 (March 2010)www.nature.com

Antibodies• Primary infection is in the ileum

• After rotavirus infection– High numbers of intestinal IgA rotavirus-specific

primary antibody-secreting cells (ASCs) and memory B-cells (to recall antigen)

– Most short-term IgA memory B-cells were present in the ileum

– Long-term IgG memory B cells were present in the spleen

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Yuan and Saif. 2002

Aquired Passive Protection

• Enteric – Mammary relationship– IgA pre-plasma cells, T and B lymphocytes migrate

through the entero-mammary axis (Stoke and Bourne, 1989)

• This occurs 1-3 weeks prior to parturition

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Aquired Passive Protection• Piglet is born immunologically naiive and is

dependent on acquired immune protection• Colostral antibodies – IgA and IgG

– IgG in colostrum– IgA in milk

• Leukocytes– Can be found within 24 hours in GI tissue (Williams, 1993) after

nursing– Dam specific (Tuboly, et al., 1998)

• Immune components

• Piglets are better passively protected with IgA than IgG in enteric infections (Haelterman, 1975)

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Models for Protection• Macaque model

– Rotavirus-specific IgG titers • high (1:10,000), intermediate (1:300), or negative (<1:25)

were infused i.v. into naive pigtailed macaques– Rotavirus-specific IgG could be detected in the sera at

18 h and fecal IgG titers could be detected only in animals given high-titer pooled sera

– Orally challenged with 106 of a simian rotavirus strain– Findings:

• Control animals shed virus starting 1–3 days for 6–8 days• Passively immunized did not shed virus or had delayed

shedding

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Westerman et al., 2005.

Live vs Killed Vaccine– Killed vaccines, generally create an IgG response

– If IgA is also needed, how do we get that response in a sow to increase IgA antibody specific cells in the mammary gland?

– In TGEv infections, the ability of the vaccine to infect the enterocyte of the dam allows for an IgA response in addition to the IgG response (Saif and Bohl, 1979 and Gough et al, 1983)

• Live or MLV type of infection

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Timing of Exposure

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Tarlowe et al, unpublished. Sponsored by Zoetis

• Rotavirus A– Control (NPE 7 weeks pre-farrow)– 4 weeks pre-farrow + Con– 2 weeks pre-farrow + Con

• No significant differences in scour scores • Litters from gilts given NPE 4-weeks pre-farrow

had lower PWM than the other treatments• No gilts were shedding rotavirus at the start of

the trial or upon entry in farrowing stalls, but gilts began shedding rotavirus during lactation.

Keys to Good Natural Planned Exposure (NPE)

• Time exposure to reduce shedding in the farrowing house and allow for immune cell transfer to the mammary gland prior to farrowing– Multiple exposures to elicit memory cell response– 3 to 4 weeks prior to farrowing

• Provide natural planned exposure with live virus with good log numbers/ml– Make sure media does not contain disinfectant or viricide

• Minimize environmental exposure– Sanitation– Whole herd NPE

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Process

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Regular whole herd NPE with last exposure 4 weeks pre-farrow

Live virus exposure followed with either vaccination or additional NPE

Immune cell migration to mammary gland

Good colostrum intakeClean/warm environment

Outcomes

• System has seen an 80% reduction in scour incidence

• Population where environmental exposure overrides the passive immunity– Even in humans, neither natural infection nor

vaccination is 100% effective

• Why?

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Acknowledgements

• Carthage Innovative Swine Solutions team• Carthage System• Zoetis• Stephanie Tarlowe

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