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Delivering and developing oral contraceptives for grey squirrels

Delivering and developing oral contraceptives for grey squirrels. G. Massei, J. Lane, S. Beatham, R. Pinkham, K. Rickell, M. Gomm National Wildlife Management Centre APHA Royal Forestry Society meeting, National Memorial Arboretum 30 October 2018. Human-wildlife conflicts are increasing.

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Delivering and developing oral contraceptives for grey squirrels

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  1. Delivering and developing oral contraceptives for grey squirrels G. Massei, J. Lane, S. Beatham, R. Pinkham, K. Rickell, M. Gomm National Wildlife Management Centre APHA Royal Forestry Society meeting, National Memorial Arboretum 30 October 2018

  2. Human-wildlife conflicts are increasing • Damage to crops, forestry, property • Disease transmission • Impact on native species • Road traffic accidents • Livestock predation

  3. Grey vs. red squirrel

  4. Impact of grey squirrels • Conservation of native species • Impact on forestry through bark stripping (£10 million per year) • affects tree growth and timber value • may cause death of tree, hence costs of restocking • increases the susceptibility of trees to various pathogens • Reduce grey squirrel number to decrease impact on forestry • 36 species of UK trees are damaged by grey squirrels: beech, sycamore, oak, ash, maple, sweet chestnut, etc. Reducegrey squirrel numberto decrease impact on forestry Control for 12 yrs in a beech woodland decrease % of squirrel damage from 50% to 8% of trees

  5. Public attitudes Acceptability of grey squirrel control (n=3758) Planting trees Contraception Kill traps Shooting Live capture (+ kill) Biol. control (pine marten) Warfarin poisoning 0% 20% 40% 60% 80% 100% Blue+ Red: very acceptable or acceptable

  6. Novel immuno-contraceptives • Vaccines inducing antibodies against proteins or hormones essential for reproduction “single-dose”injectable vaccines from our US partners GonaCon Gonadotrophin Releasing Hormone vaccine 75-100% animals infertile for 2-8 years Credible practical applications BUT animals must be captured we need an oral contraceptive

  7. Fertility control applications via injectable contraceptives Wild boar: 1 dose GonaCon stopped reproduction in 92% sows for 5-8 years Feral goats: 1 dose GonaCon reduced fertility by 83-92% for > 4 years California ground squirrels: 1 dose GonaCon reduced the reproduction by 91% (year 1) and 96% (year 2)

  8. Oral immuno-contraceptive vaccine targeting GnRH Biology, behaviour, population dynamics APHA & collaborators developed a novel GnRH-based oralvaccine • 60% rats fed the contraceptive did not breed • (control rats: 10-30%) • Contraceptive fed in a bait : reduced response to the vaccine • Novel formulation to increase effect of oral vaccine

  9. Novel formulation to deliver an oral contraceptives Spores and pollen grains • Pollen/spores: natural, renewable, commercially available • Genetic material removed to obtain sporopollenin exine capsules (SPECs) • Proven effective delivery of drugs such as fats, oils, vitamins, enzymes, hormones, ibuprofen

  10. SpECs for an oral contraceptive vaccine Proven vaccine delivery in SPECs fed to mice increased antibodies in mice antibody response lasted for up to 7 months • a possible mechanism for oral vaccination

  11. Developing and delivering oral contraceptives to control populations of grey squirrels Identify SPECs species Lab trials with rats to test SPEC-encapsulated oral vaccine Monitor bait uptakeby squirrels (lab + field) Lab trials with grey squirrels Optimise bait uptake by squirrels Field pilot trials with squirrels to confirm efficacy Large-scale trials to monitor effects at population level Initiate trials for registration package Year 1 Year 2 Year 3+ 4 Year 5

  12. The project team Project leader Lab studies coordinator Field studies coordinator 4 field ecologists 2 lab ecologists 2 lab technicians 1 statistician 2 modellers Two teams in USA and France

  13. Year 1 results: testing oral vaccine in model species Tested SPECs of sunflower and club moss fed to rats 60% (n=12 of 20) had antibodies to oral vaccine but not sufficient to cause infertility 100% rats (n= 19) had antibodies to the injected vaccine with 95% sufficient to cause infertility More work in Year 2 on formulation of oral vaccine

  14. Year 1 results: delivering contraceptives to grey squirrels Developed grey squirrel-specific hopper to: • deliver baits that will contain oral contraceptives • monitor patterns of bait uptake by individual squirrels • Tested Rhodamine B (RB) to: • monitor bait uptake in the population Pilot trial 51 grey squirrels trapped in 2 woods, PIT-tagged, released 48 bait hoppers with PIT-tag readers deployed

  15. Year 1 results: delivering contraceptives to grey squirrels Bait hoppers Established how often squirrels visit hoppers > 93% PIT-tagged squirrels entered >1 hopper at least once in 4 days Rhodamine B After 4 days of RB-treated baits > 56% squirrels had RB bands in hairs

  16. Year 1 results integrated with Defra study Model the effort required to eradicate grey squirrels via culling, contraception or culling + contraception

  17. Year 1 results integrated with Defra study Culling with different levels of effort

  18. Year 1 results integrated with Defra study Cullingin Year 1, followed by fertility control with different levels of efficacy

  19. Highlights of Year 1 • A method, based on SPECs, to encapsulate an oral vaccine • Induced an immune response to an oral contraceptive vaccine • A food hopper to monitor bait uptake patterns by individuals • A bait marker (RB) to quantify the % of grey squirrels feeding on baits that will contain oral contraceptives • Established captive colony of grey squirrels to test contraceptives

  20. Scalable applications for oral contraceptives Oral contraceptives scalable to new species and contexts Non-native invasive species, incl. feral animals Over-abundant wildlife Where culling is illegal, unfeasible, undesirable To complement culling to control populations or their economic / environmental impact

  21. Non-lethal control : when? When lethal control is: • illegal • unacceptable • unfeasible • unsustainable • environmentally hazardous • ineffective BUT also complementary to lethal control

  22. What next… We have had spring traps for many years but we did not solve the problem Integrated Pest Management • Sustained control over long period • Less staff intensive • More publicly acceptable Fertility control

  23. With thanks to… …the squirrel team! Questions? giovanna.massei@apha.gsi.gov.uk

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